Laser radiation source
In a method and system for processing a processing surface of a material, a mounting receives the material with the processing surface. At least one fiber laser comprising a pump source and a laser fiber has an infeed end, an outfeed end, and a core surrounded by a pump core, the pump source being positioned at the infeed end, and the laser fiber outputting a continuous wave laser beam at the outfeed end. At least one of the laser beam and the processing surface are laterally movable with respect to each other. A focusing optics is provided through which the laser beam passes. The laser beam output from the laser fiber is diffraction-limited to permit the focusing optics to focus the laser beam onto the processing surface as a spot having a spot size sufficiently small to create a fine structure by processing material at the processing surface.
The invention is directed to a laser radiation source, preferably for processing materials, as well as to an arrangement for processing material comprising a laser radiation source and to the operation thereof.
When processing materials with focused energy beams such as, for example, electron beams or laser beams, there are applications wherein structures must be produced that make high demands of the focused energy beam with respect of its beam geometry and the focusability of the beam. At the same time, however, a high beam power is required.
A typical case wherein extremely fine structures must be produced on a processing surface is the production of printing forms, whether for rotogravure, offset printing, letter press printing, silk screening or flexo-printing or for other printing processes. In the production of printing forms, it is necessary to produce extremely fine structures on the surface of the printing forms, since highly resolved image information such as text, screened images, graphics and line work must be reproduced with the surface of the printing forms.
In rotogravure, the printing forms were produced in the past with etching, which had led to good results; the etching, however, was replaced over the course of time by more environmentally friendly engraving with electromagnetically driven diamond styli. Printing cylinders whose surface is composed of copper are normally employed as printing forms in rotogravure, these fine structures required for the printing being engraved thereinto in the form of cups with the diamond stylus. The printing cylinders are introduced into a printing press after they are produced, the cups being filled with ink therein. Subsequently, the excess ink is removed with a doctor blade and the remaining ink is transferred onto the printed matter during the printing process. Copper cylinders are thereby employed because of their long service life in the printing process. A long service life is required given large editions, for example, in particular, in magazine printing or packaging printing, since the surface of the printing form wears in the printing process as a result of the influence of the doctor blade and of the printed matter. In order to extend the service life even further, the printing cylinders are provided with a copper layer that has been galvanized on; on the other hand, solid cylinders of copper are employed. Another possibility of making the service life even longer is comprised in galvanically chrome plating the copper surface after the engraving. In order to achieve an even longer service life, what is referred to as “hot chrome plating” is additionally applied, whereby the galvanic process is carried out under elevated temperature. The longest service lives that could previously be obtained were achieved therewith. Deriving therefrom is that copper is the most suitable as the material for the surface of rotogravure cylinders. Materials other than copper have not hitherto proven themselves for large editions.
When producing the cups, the drive of the diamond stylus occurs via an electromechanically driven magnet system having an oscillating armature to which the diamond stylus is secured. Such an electromechanical oscillatory system cannot be made arbitrarily fast because of the forces that must be exerted in order to engrave the cups. This magnet system is therefore operated above its resonant frequency so that the highest engraving frequency, i.e. the highest engraving speed can be achieved. In order to increase the engraving speed even further, a number of such engraving systems have been arranged side-by-side in the axial direction of the copper cylinder in given current engraving machines. This, however, still does not suffice for the short engraving time of the printing cylinders required currently, since the engraving time directly influences the actuality of the printing result. For this reason, rotogravure is not employed for newspaper printing but mainly for magazine printing.
Upon utilization of a plurality of engraving systems, a plurality of what are referred to as lanes are simultaneously engraved into the surface of the printing cylinder. For example, such a lane contains one or more entire magazine pages. One problem that thereby arises is that cups having different volumes are generated in the individual lanes given the same tone value to be engraved, this occurring because of the different engraving systems that are driven independently of one another and leading to differences in the individual lanes that the eye detects during later observation. For this reason, for example in packaging printing, only one engraving system is employed so that these errors, which are tolerated in magazine printing, do not occur.
When engraving the cups, the cup volume is varied dependent on the image content of the master to be printed. The respective tone value of the master should thereby be reproduced as exactly as possible during printing. When scanning the masters, the analog-to-digital converters having, for example, a resolution of 12 bits are utilized for recognizing the tone value gradations for reasons of image signal processing (for example, gradation settings), this corresponding to a resolution of 4096 tone values in this case. The signal for the drive of the electromagnetic engraving system is acquired from this high-resolution image information, said signal usually being an 8-bit signal corresponding to a resolution into 256 tone value gradations. In order to generate the corresponding volumes that are required for achieving this scope of gradations, the penetration depth of the diamond stylus into the copper surface is varied with the drive of the magnet system, whereby the geometry of the cups changes between approximately 120 μm diameter given a depth of 40 μm and approximately 30 μm diameter given a depth of 3 μm. Because only an extremely small range of variation in the depth of the cups between 40 μm and 3 μm is available, the penetration depth of the stylus with which the cups are engraved must be exactly driven to fractions of a μm in order to reproducibly achieve the desired range of gradation. As can be seen therefrom, an extremely high precision is required in the engraving of the cups, at least as regard to the generation of the required diameters and depths of the cups. Since the geometry of the engraved cups is directly dependent on the shape of the stylus, extremely high demands are also made of the geometry of the diamond stylus which, as has been shown, can only be achieved with extremely high expense and with a high rejection rate in the manufacture of the styli. Moreover, the diamond stylus is subject to wear since, when engraving a large printing cylinder having fourteen lanes, a circumference of 1.8 m and a length of 3.6 m given a screen of 70 lines/cm—which corresponds to a plurality of 4900 cups/cm2, a stylus must engrave approximately 20 million cups. When one of the diamond styli breaks off during the engraving of a printing cylinder, then the entire printing cylinder is unuseable. On the one hand, this causes a considerable financial loss and, on the other hand, represents a serious loss of time since a new cylinder must be engraved, postponing the start of printing by hours. For this reason, users frequently replace styli earlier than necessary. As can also be seen therefrom, the endurance of the diamond styli is also a critical concern.
All in all, electromagnetic engraving is well-suited for producing high-quality rotogravure cylinders; however, it has a number of weak points and is extremely complicated and one would like to eliminate these disadvantages with a different method.
The cups produced in this way, which are intended to accept the ink later, are also arranged on the surface of the printing form in conformity with a fine, regular screen, namely the printing screen, whereby a separate printing cylinder is produced for each ink, and whereby a different screen having a different angle and different screen width is respectively employed. When printing in the printing press, given these screens, narrow bridges remain between the individual cups, these supporting the doctor blade that removes the excess ink after the inking. Another disadvantage of this operating mode of this electromechanical engraving is that texts and lines must also be reproduced in screened fashion, which leads to step-patterns in the contours of the written characters and the lines that the eye perceives as being disturbing. This is one disadvantage compared to the widespread offset printing wherein this stepping can be kept an order of magnitude lower, which can then no longer be perceived by the eye, and which leads to a better quality that rotogravure could hitherto not achieve. This is a serious disadvantage of the rotogravure process.
In rotogravure, no stochastic screens can be generated wherein the size of the cups and the position of the cups can be randomly distributed corresponding to the tone value; this is not possible when engraving with the diamond stylus. Such stochastic screens are also frequently referred to as “frequency-modulated screens” that have the advantage that details can be reproduced far better with no Moirè, this also leading to a better image quality than in rotogravure.
It is also known to utilize the electron beam engraving method applied in the processing of materials for generating the cups, this having exhibited extremely good results because of the high energy of the electron beam and the incredible precision with respect to the beam deflection and beam geometry.
This method is described in the publication, “Schnelles Elektronenstrahlgravierverfahren zur Gravur von Metallzylindern”, Optik 77, No. 2 (1987) pages 83-92, Wissenschaftliche Verlagsgesellschaft mbH Stuttgart. Due to the extremely high expense that is required for the hardware and electronics, electron beam engraving has hitherto not prevailed in practice for the engraving of copper cylinders for rotogravure but only in the steel industry for surface engraving of what are referred to as textured drums for sheet metal manufacture wherein textures are rolled into the sheets.
It has been repeatedly proposed in the trade literature as well as in the patent literature to engrave copper cylinders with lasers. Since copper, however, is an extremely good reflector for laser radiation, extremely high powers and, in particular, extremely high power densities of the lasers to be employed are required in order to penetrate into the copper and melt it. There has hitherto not been any laser engraving unit with laser radiation sources having a correspondingly high power density and energy with which one succeeds in providing the copper cylinders for rotogravure with the required cup structure in the copper surface.
Attempts have nonetheless been made to utilize lasers for rotogravure in that a switch has been made to materials other than copper. Thus, for example, the publication DE-A-19 20 323 has proposed to prepare copper cylinders with chemical etching such that the surface of the copper cylinder already comprises cups that have a volume that corresponds to the maximum printing density. These cups are filled with a solid filler material, for example plastic. Much of the filler material is then removed with a laser until the desired cup volume has been achieved. This method in fact manages with a lower laser power than would be necessary in order to melt and evaporate the copper as in electron beam engraving. In this method, however, the remaining plastic is attacked by the solvent of the ink in the printing process and is decomposed, so that only a low print run is possible. This method has not proven itself in practice and has thus not been utilized.
The publication of the VDD Seminar Series, “Direktes Lasergravierverfahren für metallbeschichtete Tiefdruckzylinder”, published within the framework of a “Kolloquium vom Verein Deutscher Druckingenieure e.V. und dem Fachgebiet Druckmaschinen und Druckverfahren, Fachbereich Maschinenbau, Technische Hochschule Darmstadt”, by Dr. phil. Nat. Jakob Frauchiger, MDC Max Dätwyler, A G, Darmstadt, 12 Dec. 1996, has proposed that rotogravure cylinders plated with zinc be engraved by a quality-switched Nd:YAG high-power solid-state laser pumped with arc lamps. In this method, the volume of the cups is defined by the optical power of the laser. The laser power required for the engraving is transmitted onto the cylinder surface via an optical fiber whose output is imaged onto the cylinder surface through a variable focusing optics. One disadvantage of this method is that the arc lamps required for pumping the laser have a relatively short service life and must be replaced after approximately 500 hours of operation. The engraving cylinder becomes unuseable given a failure of the pump light source during the engraving. This corresponds to a failure of the diamond stylus in electromechanical engraving and results in the same disadvantages. A preventative replacement of the arc lamps is cost-intensive and work-intensive, particularly since one must count on the fact that the laser beam must be re-adjusted in position after the replacement of the lamps. These lamp-pumped solid-state lasers also have a very poor efficiency since the laser-active material absorbs only a slight fraction of the available energy from the pump source, i.e. from the arc lamp here, and converts into laser light. Particularly given high laser powers, this means a high electrical connection cost, high operating costs for electrical energy and cooling and, in particular, a considerable expense for structural measures due to the size of the laser and the cooling unit. The space requirements are so high that the laser unit must be located outside the machine for space reasons, this in turn being accompanied by problems in bringing the laser output onto the surface of the printing cylinder.
A critical disadvantage of this method is that zinc is significantly softer than copper and is not suitable as a surface material for printing cylinders. Since the doctor blade with which the excess ink is removed before printing in the printing press is a steel blade, the zinc surface is damaged after a certain time and the printing cylinder becomes unuseable. A printing cylinder having a surface of zinc therefore does not even begin to approach as long a service life in printing as a printing cylinder having a surface of copper. Printing forms having a zinc surface are therefore not suitable for high press runs.
Even if the zinc surface is chrome-plated after the engraving, as has been also proposed in order to lengthen the service life, the durability does not come close to that of normal copper cylinders. Chrome does not adhere to zinc as well as it adheres to copper and what is referred to as “hot chrome plating”, which is successfully employed given copper cylinders in order to achieve an optimum adhesion of the chromium on the copper, is not possible given zinc since the zinc would thereby melt. Since the chrome layer does not adhere very well on the zinc, it is likewise attacked by the doctor blade, which leads to a relatively early failure of the printing cylinders. When, in contrast thereto, copper cylinders are chrome-plated according to this method, then incredibly high press runs are possible since the chromium firmly adheres on the copper surface, so that these copper cylinders out perform the chrome-plate zinc cylinders by far.
It proceeds from the publication EP-B-0 473 973, which is likewise directed to the method described above, that an energy of 6 mWsec is required in this method given zinc for cutting a cup having a diameter of 120 μm and a depth of 30 μm. An energy of 165 mWsec is recited in this publication for copper, this amounting to a factor of 27.5 for the required laser power. Lasers having a continuous-wave performance of several kilowatts given good beam quality are thus required in order to produce cups in copper with a speed that is accessible for the printing industry. Such a power, however, cannot be produced with the laser arrangement described above. For this reason, it is likewise only possible to engrave a zinc surface.
Such a laser arrangement, which is composed of a single solid-state laser, in fact makes it possible to process rotogravure cylinders having a zinc surface; if, however, one wishes to utilize the advantages of the copper surface and stay with copper cylinders and engrave these with a laser, the high power density required for penetration into the surface of the copper and the high energy required for melting the copper must be inevitably exerted. This, however, has not hitherto been successfully done with a solid-state laser.
It is known that the beam quality in solid-state lasers, i.e. the focusability, decreases with increasing power. Even if the power of the solid-state lasers were to be driven up or if a plurality of solid-state lasers were directed onto the same cup or parts thereof, it would therefore not be possible to satisfactorily engrave copper cylinders for rotogravure with such a laser because the precision of the laser beam, as offered by the electron beam, required for generating the fine structures cannot be achieved. If the laser power were increased given this apparatus, then a further problem would arise: the focusing of high radiant intensity into optical fibers is, as known, difficult. The fibers burn at high power as a consequence of misadjustment at the infeed location. If one wishes to avoid this, however, the fiber diameter would have to be enlarged which, however, in turn has the disadvantage that the fiber diameter would have to be imaged onto the processing material with even greater demagnification. A demagnified imaging, however, leads to an increase in the numerical aperture on the processing surface and, consequently, to a reduced depth of field on the processing surface. As proposed, the distance from the processing surface could be kept constant. When, however, the beam penetrates into the surface of the material, then a defocusing automatically derives. This has a disadvantageous influence on the required power density and on the exact dot size. Since, however, the diameter of the processing spot and the energy of the beam determine the size of the cup, it then becomes difficult to make the cup size as exactly as required by the desired tone value. For this purpose, it would also be necessary that the laser power is exactly constant and also remains constant over the entire time that is required for a cylinder engraving. When this is not the case, the cup size changes and the cylinder becomes unuseable. This cannot be compensated by varying the size of the processing spot since it is not possible to adequately vary the processing spot in shape.
Further, a complicated modulator is required given such an arrangement. As known, modulators for extremely high laser powers are slow, this leading to a reduction of the modulation frequency and, thus, of the engraving frequency. When, however, the engraving frequency is too low, the energy diffuses into the environment of the processing spot on the processing surface without cutting out a cup. It is therefore necessary to also exert a high power in addition to the high energy for the cutting.
The publication “Der Laser in der Druckindustrie”, by Werner Hülsbusch, page 540, Verlag W. Hülsbusch, Konstanz, describes that it is particularly a matter of a high power density in processing materials. Given power densities of typically above 107 through 108 W/cm2, a spontaneous evaporation of the material occurs in all materials, this being accompanied by a sudden absorption rise, which is especially advantageous since the laser power is then no longer reflected from the metal surface. When, for example, a laser source of 100 W is available, then the processing spot diameter may not be larger than 10 μm in order to arrive at these values in the region, as proceeds from the following equation: 100 W: (0.001 cm×0.001 cm)=108 W/cm2.
SUMMARY OF THE INVENTIONOne object of the present invention is to improve a laser radiation source, preferably for processing materials as well as an arrangement for processing materials having a laser radiation source and the operation thereof such that an extremely high power density and energy are achieved in a cost-beneficial way.
A material processing system and method is provided for processing a processing surface of a material. A mounting receives the material. At least one fiber laser comprising a pump source and a laser fiber having an infeed end, outfeed end, and a core surrounded by a pump core is provided. The pump source is positioned at the infeed end and the laser fiber outputs a continuous wave laser beam at the outfeed end. The laser fiber outfeed end is spaced from the processing surface and at least one of the laser beam and the processing surface are laterally movable with respect to each other. A focusing optics is provided through the laser beam passes. The laser beam output from the laser fiber outfeed end is diffraction-limited to permit the focusing optics to focus the laser beam onto the processing surface as a spot having a spot size sufficiently small to create a fine structure by processing material at the processing surface.
BRIEF DESCRIPTION OF THE DRAWINGS
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to preferred embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
The laser radiation source comprises at least one diode-pumped fiber laser, or a plurality of diode-pumped fiber lasers whose output radiation beams impinge the processing location next to one another and/or over one another or in a point or bundle and thus enables the generation of a processing spot that is designationally variable in shape and size, even given extremely high laser powers and extremely high power densities. According to preferred embodiments, these fiber lasers can be implemented as continuous wave lasers or as quality-switched lasers, also referred to as Q-switch lasers, whereby they are advantageously internally or externally modulated and/or comprise an additional modulator. Q-switch lasers have an optical modulator available to them within the laser resonator, for example an acousto-optical modulator, that, in its opened condition, interrupts the laser effect given a pump radiation that continues to exist. As a result thereof, energy is stored within the laser resonator, this being output as a short laser pulse having high power when the modulator is closed in response to a control signal. Q-switch lasers have the advantage that they emit short pulses having high power, which briefly leads to a high power density. An advantageous elimination of the molten and evaporated material is enabled in the pulsed mode due to the brief-term interruptions in the processing event. Instead of switching the quality, a pulsed mode can also be generated with internal or external modulation.
The processing spot can be designationally modified in shape and size in that different numbers of lasers are provided that can be switched on for shaping the processing spot. It is thereby especially advantageous that the depth of the cut cup can be determined by the laser energy independently of its shape and size. Further, a control of the energy of the individual lasers can also generate any arbitrary beam profile within the processing spot and, thus, any arbitrary profile within the cup as well.
Further advantages of the present preferred embodiments compared to known laser radiation sources are comprised therein that the infeed of the radiant power from a solid-state laser into an optical fiber can be eliminated but the exit of the fiber laser supplies diffraction-limited radiation that, according to the preferred embodiments can be focused onto less than a 10 μm diameter, as a result whereof an extremely high power density is achieved given the greatest possible depth of field.
Given a traditional arrangement with solid-state lasers, the size of the processing spot lies in the region of approximately 100 μm. Given the present preferred embodiments, thus a power density that is improved by the factor 100 derives, and a design possibility in the area of the processing spot that is improved by the factor 100 derives.
Due to the high precision and due to the shape of the processing spot that can be designed in very fine fashion, extremely fine screens, also including the stochastic screens that are also called frequency-modulated screens (FM screens) and, thus extremely smooth edges in lines and written characters can be economically produced, so that rotogravure no longer need be inferior to offset printing in terms of printing quality.
Due to the operating mode of the laser radiation source of the preferred embodiments, it is also possible to link arbitrary raster widths to arbitrary screen angles and apply arbitrary different screen widths and arbitrary different screen angles at arbitrary locations on the same printing cylinder. Line patterns and text can also be applied independently of the printing screen as long as one sees to sufficient supporting locations for the doctor blade.
One advantage of the preferred embodiments is that the differences in the data editing for the production of the printing form are reduced to a minimum between rotogravure and offset printing, this yielding substantial cost and time savings. Up to now, the data for the rotogravure are acquired by conversion from the data already present for the offset printing because a signal is required for the drive of the engraving system that defines the volume of a cup, whereby the area of a screen dot is determined in offset printing. As a result of the multiple arrangement of lasers, the laser beam source of the preferred embodiments makes it possible to vary the area of a cup given constant depth, for which reason it is no longer required to convert the data for offset printing into data for the rotogravure. The data for the offset printing can be directly employed for engraving the rotogravure forms.
Another advantage of the preferred embodiments is that both the area of a cup as well as the depth can be controlled independently of one another with this laser radiation source, this leading to a greater number of tone value gradations that can be reproducibly generated, this leading to a more stable manufacturing process for the printing cylinders and to an improved printing result.
It is also an essential advantage that the energy can be unproblemmatically transported from the pump source to the processing point with the fiber, namely the fiber laser itself, or with a fiber that is welded on or, respectively, attached in some other way, this yielding an especially simple and space-saving structure.
Another advantage of the preferred embodiments is that the efficiency of such an arrangement with fiber lasers is significantly higher than the efficiency of solid-state lasers, since absorption efficiencies of more than 60% are achieved for fiber lasers, these lying only at approximately half given traditional diode-pumped solid-state lasers and being even far lower given lamp-pumped solid-state lasers. Given the required power of several kilowatts for an efficient engraving of rotogravure cylinders, the efficiency of the lasers is of incredible significance for the system costs and the operating costs.
Further, a multiple arrangement of lasers yields the advantage that the outage of a laser is less critical than given a single-channel arrangement. When the only laser that is present given the single-channel arrangement fails during the engraving of a printing cylinder, the entire printing cylinder is unuseable. When, however, a laser fails given a multiple arrangement, then the power of the remaining lasers can, for example, be slightly boosted in order to compensate the failure. After the end of the engraving, the laser that has failed can then be replaced.
The dissertation, “Leistungsskalierung von Faserlasern”, Physics Department of the University of Hannover, Dipl.-Phys. Holger Zellmer 20 Jun. 1996, fiber lasers are discussed as being known. These lasers, however, had already been proposed in 1963 by Snitzer and Köster, without these having been previously utilized for processing materials given high powers. Although powers of up to 100 W can be fundamentally achieved with the lasers described in this dissertation, no useable arrangements are known for utilizing these lasers for purposes of the present preferred embodiments.
The publication WO-A-95/16294 has already disclosed phase-coupled fiber lasers; however, these are extremely involved in terms of manufacture and are not suitable for industrial employment. It had hitherto not been recognized to bring lasers of this simple type to high power density and energy in the proposed, simple way and to utilize them for erosive processing of materials.
For example, the resonator length of the individual lasers must be kept exactly constant to the fraction of a micrometer, for which purpose what are referred to as “piezoelectric fiber stretchers” are utilized. As a result of the complex structure, it is likewise not possible to construct the laser unit modularly, i.e. of components that are simple to assemble and to be multiply employed or to replace individual laser components as needed on site as a consequence of the great number of optical components within a phase-coupled laser. Moreover, the optical losses are extremely high, and the pump radiation absorption of the laser-active medium is low, which results in a low efficiency of the arrangement. Although fiber lasers are not particularly susceptible to back-reflections in and of themselves, phase-coupled lasers exhibit a great sensitivity to back-reflections due to their very principle, i.e. when portions of the emitted radiation proceed back into the laser resonator due to reflection or dispersion, as is unavoidable when processing materials. These back-reflections lead to uncontrolled output amplitudes and cause the laser to shut down. Although what are referred to as optical isolators are known, these being intended to attenuate such back-reflections, these involve a number of disadvantages in practice, which, for example, include the optical losses, the high price and the inadequate attenuation properties. The lasers for the purpose of the present preferred embodiments of processing materials need not only exhibit a high power density but also must be able to supply the required energy for cutting out the cups, must be extremely stable in terms of the emitted radiation and must have a very good efficiency.
Further, U.S. Pat. No. 5,694,408 has disclosed a laser system wherein a master oscillator generates low-power radiation energy at a specific wavelength, this being optically intensified and it being distributed for further post-amplification onto a plurality of post-amplifiers, in order to then be in turn united to form a common beam, a precise phase readjustment of the individual post-amplified signals being required for this purpose in order to avoid interferences in the output signal. This requires complicated measuring and control procedures and involved actuating elements, for which purpose, for example, electro-optical phase modulators must be utilized, these being extremely expensive and having to be operated with extremely high voltages.
Further, U.S. Pat. No. 5,084,882 discloses a phase-coupled laser system that employs a plurality of fibers or fiber cores in a bundle, the core thereof being, on the one hand, large compared to its cladding or its spacing in order to achieve the phase coupling; on the other hand, this should only have a diameter of a few micrometers since it is a matter of single-mode fibers. This system is mainly provided as an optical intensifier.
Another phase-coupled laser system that is likewise implemented in an extremely complex way and that is composed of a plurality of what are referred to as “sub-oscillators” is disclosed by GB-A-21 54 364 under the title “Laser Assemblies”, having already been disclosed in 1984; however, no industrial realizations with such phase-coupled laser systems have become known up to now.
It has also not been previously proposed to combine a number of the initially cited fiber lasers in a simple way, i.e. without a complex phase coupling or the like, to form a compact, rugged and service-friendly radiation source for processing materials and, for example, to employ this for multi-track recording. A multiple arrangement of such simple lasers that can be cost-beneficially manufactured in quantity in several tracks and levels yields enormous advantages for the purposes of the preferred embodiments that would certainly not have escaped attention if the preferred embodiments solution had been known.
A further advantage of fiber lasers is their clearly lower tendency to oscillate when energy proceeds back into the laser. Compared to traditional solid-state lasers, fiber lasers have a resonance overshooting that is lower by an order of magnitude in terms of its transfer function, this having been very positively proven during operation. When processing materials, namely, one cannot always prevent energy from being reflected from the processing location back into the laser because the melting material is explosively hurled in unpredictable directions and thereby flies through the laser beam before it can be removed and neutralized by particular techniques that are presented in one embodiment of the invention.
An essential advantage of the multiple arrangement of fiber lasers without phase coupling is that the individual lasers behave differently in case of a back-reflection. This is related to the fact that, for example, some of the lasers are not affected at all by a back-reflection and others may possibly be effected only with a delay. The probability is therefore high that oscillations of the individual lasers, if they occur at all, are superimposed such that they have no negative influence on the quality of the results of the engraving.
The laser radiation source of the preferred embodiments can also be advantageously utilized for all other types of processing materials or transferring materials wherein high power density, high energy and great precision or, too, high optical resolution are important. In addition to engraving rotogravure cylinders having a copper surface, other materials such as, for example, all metals, ceramics, glass, semiconductor materials, rubber or plastics can be processed and/or materials can be stripped from more specifically prepared carrier materials and transferred onto other materials at high speed and with high precision. In addition to those that are uncoated, moreover, rotogravure cylinders, printing plates or printing cylinders that are coated with masks as well as all types of printing forms can also be produced or, respectively, processed at high speed and with high resolution for offset printing, letter press printing, silk screening, flexo-printing and all other printing processes. For example, the offset printing plates having metal coating (bi-metal plates) that are employed for printing extremely large print runs in offset printing and similar materials can be provided with images in an environmentally friendly way, this having been hitherto possible only with etching.
Further, materials can be processed that contain a magnetizable surface, in that the parts of the material magnetized in large-area fashion by a pre-magnetization process are de-magnetized by briefly heating selected processing points to temperatures that lie above the Curie point, when heated with the laser radiation source of the preferred embodiments. The material provided with images in this way for applications in printing technology can serve as a print master in conjunction with a corresponding toner.
As a result of the high power density of the inventive laser radiation source of the preferred embodiments, it is also possible to directly process chromium. Thus, for example, printing cylinders of copper can already be chrome-plated for rotogravure before the laser engraving, this eliminating a work step after the engraving and benefiting the timeliness. Since the printout behavior of a cup engraved in copper is also better than that of a chrome-plated cup and its volume is more precise, this method also yields even better printing results in addition to the high service life as a result of the remaining chromium layer and the improved timeliness.
The employment of the laser radiation source of the preferred embodiments, however, is not limited to employments in printing technology but can be utilized anywhere that it is important to erode material or change the properties of the material by energy irradiation with lasers given high resolution and high speed. Thus, for example, the aforementioned texture drums can also be produced with the radiation source of the preferred embodiments. Further, the patterns of interconnects for printed circuit boards, including the boards for the components, preferably for multi-layer printed circuit boards, can be produced by eroding the copper laminate and allowing the interconnects to stand, and by eroding copper laminate and carriers at the locations of the bores. Further, the surface structure of material surfaces can be partially modified by partial heating. For example, extremely fine structures in the hardness of material surfaces can be produced in large-area fashion in this way, this being particularly advantageous for bearing surfaces since the bearing properties can be intentionally influenced in this way. Further, there are non-conductive ceramic materials at whose surface metal crystallizes out due to energy irradiation, this being capable of being utilized in conjunction with the laser radiation source of the preferred embodiments for applications that require a high resolution, for example for producing interconnects.
The laser beams can thereby be guided to the processing spot and can be moved across the material in the greatest variety of ways for example, the material to be processed can be located on a rotating drum past which the radiation source is conducted in relative fashion. However, the material can also be located in a plane over which the laser radiation source or its output radiation is conducted past in relative fashion. In a flat bed arrangement as presented in the aforementioned publication “Der Laser in der Druckindustrie” von W. Hülsbusch, FIG. 7-28 on page 431 and as likewise disclosed in the publication EP-A-0 041 241, the radiation source presented therein as argon or He Ne laser or, respectively, as laser light source (4) in
The output of the laser radiation source can also be implemented with a variable number of tracks whose mutual spacings are variable, preferably similar to a long comb, this moving relative to the material to be provided with images. Such an arrangement is disclosed by U.S. Pat. No. 5,430,816. It is disclosed therein to direct the radiation of an excimer laser having a strength of approximately 50 watts onto a bundle of what are referred to as stepped index fibers having diameters of 50 through 800 micrometers and to respectively couple a part of the radiation into the individual fibers. The exit of each fiber is then imaged onto the work piece via a respective positive lens having a diameter of 60 mm, whereby the spacing between the individual processing points must amount to at least 60 mm and a protective mechanism to prevent contamination is required per positive lens. What is disadvantageous is that only a fraction of the laser energy thus proceeds into the respective fibers. The energy distribution turns out very differently and changes in the exit power derive given movement of the fibers, for which reason what are referred to as scramblers must be utilized in order to avoid this. These scramblers, however, disadvantageously influence the efficiency of the system and increase the costs. Only relatively imprecise bores having a diameter of approximately 130 micrometers can be produced in plastic with such an arrangement. The pulse rate of the laser is the same for all simultaneously produced bores, so that all bores must be implemented of the same size. Moreover, the system is relatively slow since a boring processing lies between one and two seconds. An arrangement having fiber lasers yields tremendous advantages compared thereto: the speed can be increased by several orders of magnitude and metals can also be processed; the precision is substantially greater since fiber lasers also exhibit a stable output power given movement of the laser fibers; and bores having diameters below 10 micrometers can also be unproblemmatically produced. Since each fiber laser can be separately modulated, different processing patterns are possible. Further, the end sections of the fiber lasers can be unproblemmatically implemented smaller than 2.5 mm in diameter, this enabling a clearly smaller spacing between the processing tracks. As a result thereof, it is also possible to employ a shared protective mechanism to prevent contamination of the optics.
Another example for the application of the laser beam source of the preferred embodiments wherein the material is preferably arranged in a plane derives in the semiconductor industry in the processing of what are referred to as wafers, i.e. usually circular disks of suitable semiconductor material that, for example, are incised or cut or can be provided with all conceivable patterns in the surface, of a type that could previously be manufactured only by time-consuming chemical etching processes that were also not environmentally friendly.
For the multi-channel cutting and in sizing of materials, a simplified embodiment of the laser radiation source is possible, as disclosed in the German Patent Application P 198 40 936.2 of the assignee, “Anordnung zum mehrkanaligen Schneiden und Ritzen von Materialien mittels Laserstrahlen”.
A further application of the laser radiation source is established in the manufacture of monitors and displays. For example, the apertured masks for color picture screens as well as the masks of what are referred to as flat picture screens or LCD displays can be manufactured in a more environmentally friendly way with laser processing than with the chemical etching processes that were previously employed, in that the laser radiation source is applied.
A considerable advantage of the laser radiation source is that it has a small volume and has a flexible connection, namely the laser fibers or fibers connected thereto between the pump source and the exit of the radiation at the processing location and thus allows all conceivable operating positions of the laser radiation source or of its beam exit. There are therefore also no limitations for the spatial arrangement of the processing surface, since they can be arranged in an arbitrary attitude in space.
Another advantage of the preferred embodiments is comprised therein that the radiation beam of the individual lasers with defined values in beam diameter, beam divergence centering and angular direction can be exactly and durably acquired in a terminating section (terminator), as a result whereof a fabrication-suited and service-suited arrangement for forwarding the laser radiation onto the processing surface can be created. The radiation beams can thereby be coupled into the fiber dependent on the application, for example as pump spot and/or can be coupled out as parallel laser beam, can diverge at the exit location or, for example, can be focused in a certain distance from the exit point. There is thus a desire to fashion the terminator as small as possible and to provide it with one or more fits as a reference surface or reference surfaces for the alignment of the laser beam.
According to the preferred embodiments, this is achieved in that the optical fibers are set in the terminator and the position of the optical fibers and/or the position of the emerging radiation beam is exactly adjusted. On the basis of the exact adjustment and of a correspondingly spatially small embodiment of the terminators which can also be attached to one another in an especially simple way as a result of a special shaping, it becomes possible to combine the radiation beams of a plurality of fiber lasers and focus them such that the respectively encountered object is achieved and, at the same time, an economical manufacture as well as a cost-beneficial maintenance of the laser radiation source is enabled.
The infeed event of the pump radiation into the pump cross-section 14 of the laser fiber 5 is shown in greater detail in
The relatively large pump cross-section 14 simplifies the infeed of the pump energy and enables the use of a connection between pump source and laser fiber that is simple to release, as shown in
The laser radiation emerging from the laser gun 23 impinges the surface of the drum at the processing location in the processing spot 24. Either the surface of the drum as well as a material clamped onto the drum surface can be processed. The fiber lasers, whose laser fibers 5 are respectively wound to a form, for example, an air-permeated coil 25, are supplied into the laser gun 23 with the terminators 26, 94. Advantageously, however, passive single-mode fibers or other passive optical fibers, referred to in brief as fibers 28, can also be welded to the fiber lasers or coupled thereto in some other way before the terminators 26, 94 are attached, as described in
The pump sources 18 of the fiber lasers are attached on a cooling member 27 that diverts the waste heat via a cooling system 31. The cooling system 31 can be a matter of a heat exchanger that delivers the waste heat to the surrounding air; however, it can also be a matter of a cooling unit. The laser gun 23 can also be connected to the cooling system, but this is not shown. The driver electronics for the pump sources 18, which belong to the supply 32 (not shown in further detail), are preferably situated on the cooling member. A machine control is provided for the drives but is not shown in
The modulation signals for the laser radiation are generated in the controller 33 and the interaction of the laser radiation source with the machine control and with the supply 32 as well as the executive sequence of the calibration events as well as of the control and regulation events are managed in the controller 33. A safety circuit (not shown), for example, switches the pump sources permanently off when there is danger.
Although a horizontally seated drum is shown in
Instead of one or each of the provided fiber lasers 2, it is conceivable to provide a laser system with a terminator into the laser radiation source and alternative supply to the laser gun 23, whereby the fiber laser described in detail under
Such a laser system that, for example, is disclosed by U.S. Pat. No. 5,694,408 contains an optical post-amplification and comprises a radiation output composed of a fiber. A terminator is described in greater detail later in one of the
Instead of employing the laser system disclosed by U.S. Pat. No. 5,694,408, it is also conceivable to employ a phase-coupled laser system according to U.S. Pat. No. 5,084,882. An image of the fiber bundle then results on the processing surface as the respective processing spot. Alternatively, a single-mode fiber could be welded to each fiber at the exit of the bundle, this being provided with the respective terminators, and supply the laser gun. However, it is extremely difficult and complicated to manufacture such phase-coupled laser systems and they would be correspondingly expensive. Up to now, such phase-coupled laser systems have also not been commercially available.
In a housing 35, 4 fiber lasers FHD1 through FHD4, FVD1 through FVD4, FHR1 through FHR4, FVR1 through FVR4 via terminators 26 with mounts 29 (
As explained in greater detail in
A particular advantage of the combining of a plurality of lasers to form a single spot, namely to each of the individual processing points B1 through Bn (for example B1 through B4 in
The laser emission of the individual fiber laser can also be distributed onto a plurality of terminators, this being described in
By omitting fiber lasers or, respectively, tracks, further, the acquisition costs for such an arrangement can be lowered as needed and fiber lasers can be retrofitted later as needed. For example, one can begin with one fiber laser and one track. The lacking terminators of the fiber lasers that are not introduced are replaced for this purpose by structurally identical terminators that, however, do not contain a through opening and no laser fibers and only serve for termination in order to close the housing 35 as though it were equipped with all terminators.
However, the laser radiation of a plurality of fiber lasers can also be combined and conducted into a single terminator, this being described in
Immediately after the beam bundle has left the respective terminator, a part of the laser emission can be coupled out via a beam splitter (which, however, is not shown) and can be conducted onto a measuring cell that is not shown in the FIGS. in order to produce a measured quantity therefrom that can be used as comparison value for a control of the output power of each and every fiber laser. However, laser emission can also already be coupled out of the laser fiber for the acquisition of a measured quantity before the terminator, this also not being shown.
The plurality of planes wherein the terminators are arranged is not limited to the one plane as described. For example, arrangements having three planes are recited in
The respective beam packets of the fiber lasers are modulated via a respective four-channel acousto-optical modulator 34 whose functioning and embodiment is explained in greater detail in
The multi-channel acousto-optical modulator 34 is preferably secured on a cylindrical modulator housing 41 that is rotatably seated in an opening 48 in the housing 35. After the modulator housing has been adjusted to the required Bragg angle αB, the modulator housing is fixed with a connection 42. A seal 43 sees to it that each modulator housing terminates gas-tight relative to the housing 35. A specifically prepared printed circuit board 171 projects from the modulator housing 41 into the interior space 44 of the housing 35, electrical connections to the piezo-electric transducers 45 being produced thereover. The preferred embodiment of the modulators is described in greater detail in
After passing through the acousto-optical modulators, the beam packets FD1 through FD4 and FR1 through FR4 are conducted to a strip mirror 46 that is described in greater detail in
A significant advantage of the arrangement is that the symmetry axis of the beam packets FHD1 through FHD4 and FD1 through FD4 lie on the axis of the housing 35 that is defined by the bore 47, and the beam axes of the corresponding beam packets respectively lie parallel or at a right angle to this axis, which allows a simple and precise manufacture. However, it is also possible to arrange the beam packets asymmetrically and at different angles. Further, it is possible to correct small differences in the position of the beam packets by adjusting the wavelength-dependent mirrors 37 and of the strip mirror 46. It is possible to still re-adjust the terminators in position after they are mounted and in terms of their angular allocation, for example for individual optimization of the Bragg angles in the individual channels; this, however, is not shown in the Figures.
It lies within the scope of the preferred embodiments that the plurality of tracks is reduced but can also be increased further; for example, by joining respectively eight instead of four terminators that are connected to fiber lasers to form a beam packet, a doubling of the number of tracks can be undertaken. For this purpose, two eight-channel acousto-optical modulators would have to be utilized. Acousto-optical modulators having 128 separate channels on a crystal can be commercially obtained.
Within the framework of the preferred embodiments, it is likewise possible to arrange the fiber lasers in different planes for increasing the power per track and to superimpose their power on the processing surface, this being explained in greater detail in
Another possibility for increasing the number of tracks is described in
Directly modulatable fiber lasers can also be utilized, this being described in greater detail in
Operation with a plurality of tracks of lasers and a plurality of lasers in a track enables high processing speeds given low relative speed between the laser gun and the work piece. The processing speed can also thus be optimally adapted to the time constant of the heat absorption of the material. Given a longer operating time, too much energy uselessly flows off into the environment.
The housing 35 is closed gas-tight with a cover and a seal, neither being shown in the Figures. A cylindrical tube 51 is flanged to the housing 35 in the region of the bore 47 and is sealed via a seal 52. The cylindrical tube contains as an optical transmission unit two tubes 53 and 54 each having a respective optical imaging system that image eight laser beam bundles FD1 through FD4 and FR1 through FR4 at the radiation exit 10 (
The beam path is shown as a side view in
In order to transmit the laser energy as efficiently as possible and keep the heating of the optical components within limits, all optical surfaces occurring in the various embodiments of the laser radiation source are anti-reflection coated with outmost quality for the wavelength range coming into consideration. The optical imaging systems can preferably be telecentrically implemented.
There are also other advantageous solutions for the transmission unit in order to shorten the structural length of the transmission unit and thereby nonetheless achieve a large spacing between the objective lens and the processing surface, as is shown in even greater detail in, among others, FIGS. 4b and 4c. The lenses 55 and 56 can be connected to the tube 53 by screwed connections or by gluing; however, they can also be preferably metallized at their edges and soldered to the tube 53. The same is true of the lenses 57 and 61 in the tube 54. A gas-tight seal of the lenses and a good heat transmission from the lenses to the tubes thus derives. The tube 54 is preferably terminated gas-tight relative to the cylindrical tube 51 with a seal 62. With respect to tightness and cleanliness, the same conditions apply to the space 63 as apply to the space 44 and, likewise, to the spaces 64 and 65 within the tubes 53 and 54. The chambers 66 and 67 are preferably connected to the spaces 44 and 63 via bores 71. The tubes 53 and 54 can preferably comprise openings 72.
An intercept arrangement 73 for neutralizing the laser radiation that is not intended to produce any processing effect on the processing surface and that comprises a high-reflectivity mirror 74 and a dispersion lens (concave lens) 75 projects into the space 63. The principle of the intercept arrangement 73 is described in greater detail in
It is advantageous in the arrangement according to
The laser gun 23 of the laser radiation source is rotatable around the optical axis that is identical to the axis of the cylindrical tube 51, 95 within the arrangement for processing materials (
By turning the laser gun 23 around its optical axis, the track spacing of the laser tracks on the processing surface 81 can be modified, this being shown in greater detail in
As a result of the high laser power, the optical elements in the beam path will heat, since they absorb a part, even though a slight part, of the laser energy. Preferably, the critical optical components are therefore not made of glass but of a material having better thermal conductivity, for example of sapphire. The waste heat, given metallization of the connecting surfaces of the optical components, is eliminated by the solder connections to the mounts and to the housing. For better heat output, the housing is implemented with cooling fins 92 that can be cooled by a ventilator (not shown). A permeation of the housing 35 as well as of the other component parts of the laser radiation source with bores is also possible, particularly in the critical regions at the lens mounts and mounts for the terminators 26, a coolant being capable of being pumped therethrough, as shown in
Since, as presented above, extremely high laser powers are required in processing of materials, it is critical to the preferred embodiments to keep the number of optical elements, particularly lenses, in the beam path as low as possible in order to keep the optical losses and the risk of contamination of the optics, which would always lead to a premature failure, as low as possible. It is also lies within the scope of the preferred embodiments that the objective lens (61, 103 and 112) is equipped with an interchangeable mount so that it can be quickly replaced by the user of the laser radiation source as needed, whether because it has been contaminated during operation or because a different imaging scale is requested. In this case, it is advantageous that the bore 72 and the tube 54 is not implemented.
It also lies within the scope of the preferred embodiments that techniques are undertaken in the optical beam path so that no laser energy can proceed back into the lasers. It is shown in
It is also shown for two planes in
It lies within the scope of the preferred embodiments to select embodiments of the optical, mechanical and electrical arrangement for
The housing 93 has mounts 29 fitting the terminators 94. The terminators 94 preferably correspond to those of
The tube body 96 can be evacuated in the space between the lenses 101 and 102 or can be filled with a protective atmosphere or, preferably, be connected to the space 105 via a bore 104, said space 105 being in turn connected via a bore 106 to the space 107. The space 107 is connected to the space 111 via the bore 47, said space 111 being in turn terminated gas-tight, as described under
A lens 55 could also be employed in order to deflect the beam bundles into the desired direction, as was shown in
According to the preferred embodiments, it is also possible to combine the lenses 102 and 103 to form a single, combined lens. A transmission unit having only two lenses then derives. It is also possible to arrange a displaceable lens (not shown) with a long focal length between the lenses 101 and 102, the focusing of the processing points on the processing surface being capable of being finely readjusted therewith without displacing the radiation source. A vario-focusing optics can also be employed, as was mentioned under
A special mouthpiece 82 is provided at the laser gun 23 that is intended to prevent a contamination of the objective lens 112 and that is described in greater detail under
The beam path is folded with the two mirrors 121 and 115. The arced mirror 121 is preferably fabricated of metal. It is intimately connected to the highly reflective mirror 97 and is preferably fabricated of one piece therewith. The convex surface of the arced mirror can be spherically or spherically shaped. The mirror 115 is concavely shaped, i.e. a concave mirror. Its surface can be spherically shaped but is preferably ly shaped. It is preferably composed of metal. Metal has the advantage of good elimination of the waste heat. A considerable advantage given manufacture of metal also derives in the production of surfaces, which, in this case, can be produced by known diamond polishing lathing methods, as can also spherical and planar surfaces. As a result thereof, the highly reflective mirror 97 and the arc mirror 121 can be manufactured of one piece and, preferably, in one work pass having the same shape of the surface and can be mirrored in common, which is particularly simple in terms of manufacture and very advantageous for the positional stability of the arced mirror. In the modulation of the laser energy with the acousto-optical modulator, it impinges either the arc mirror 121 or the highly reflective mirror 97. The waste heat that is produced remains the same in any case and the arced mirror stays at its temperature and, thus, its position, which is very important since it is preferably implemented with a short focal length and the imaging quality of the arrangement is therefore very dependent on its exact position. In this case, the arced mirror 121 has advantageously co-assumed the function of the highly reflective mirror 97. The highly reflective mirror 97 can, however, also have some other form of surface than the arced mirror 121 and, for example, can be a plane mirror.
The beam path is similar to that of an inverted mirror telescope after Herschel that, however, contains a convex lens instead of the arced mirror and that is described in greater detail in
The space 111 in the housing 93 is connected to the cavity 123 via the bore 122. Both spaces can be evacuated, filled with a protective atmosphere, or flooded by a protective atmosphere, as already described. The mount 116 that accepts the interchangeable objective lens 112 is attached to the end of the eccentric tube 113 that resides opposite the housing 93. A seal 124 closes the cavity 123 gas-tight. The mount can also accept an anti-reflection coated plate 117 whose edge is preferably metallized and that is preferably soldered gas-tight to the mount. Its job is to keep the cavity 123 gas-tight when the objective lens was removed for cleaning or when an objective lens having a different focal length is to be introduced in order to generate a different imaging scale. The space between the objective lens 112 and the highly anti-reflection coated plate 117 can also be connected to the space 123 via bore (not shown), particularly when the entire laser gun, as described under
The eccentric tube can be provided with cooling fins 92 over which a ventilator (not shown) can blow in order to eliminate the waste heat to the environment better. The laser gun is rotatably seated in a prism around the axis between concave mirror and objective lens in order, as described under
It is possible to arrange a displaceable lens (not shown) having a long focal length between, preferably, the concave mirror 115 and the objective lens 112, the focusing of the processing points onto the processing surface being capable of being finely readjusted therewith without displacing the laser gun. However, a variable focusing optics (zoom lens) can also be utilized, as was described under
This terminator 26 can be fundamentally used for all applications wherein the matter of concern is that the ray bundle emerging from a fiber 5, 28 be precisely coupled with a releasable connection. It is likewise possible with the assistance of this terminator to produce a precise, releasable connection of the fiber 5, 28 to the remaining optics. The terminator is composed of an oblong housing 132 that comprises a through cylindrical opening 130 extending in axial direction. The housing is preferably manufactured of prefabricated, for example drawn material that can preferably be composed of glass. The laser fiber 5 of the fiber laser is preferably stripped off its cladding at its ultimate end and is preferably roughened at its outside surface, this being disclosed in German Patent Application P 197 23 267, so that the remaining pump radiation leaves the laser fiber before the entry of the laser fiber into the terminator. The fiber 5, 28 can also be additionally surrounded by a single-layer or multi-layer protective sheath 131 that can be connected to the housing 132 of the terminator, for example with a glued connection 142. The housing 132 comprises fits 134 with which the housing can be exactly introduced in a mount 29 (
In order to prevent the optical surfaces on the optical fiber and the side of the lens 133 that faces toward the optical fiber from contaminating biparticles in the ambient air, the connections in
The inventive terminators advantageously enable the laser radiation source to be built of individual modules.
According to the preferred embodiments, it is possible to preferably implement the lens 133 at its side facing toward the fiber end on the basis of a corresponding shape being and vapor-deposition of a corresponding layer such that it co-assumes the function of the outfeed mirror 12. According to the preferred embodiments, it is also possible to implement the lens 3, 154 by corresponding shaping and vapor-deposition of a corresponding layer that it co-assumes the function of the infeed mirror 7.
It is fundamentally possible to combine a plurality of the terminators described above in a plurality of tracks side-by-side and above one another in a plurality of planes to form a packet.
It is also possible to implement the shape of the terminators differently from that shown in the Figures, for example that a cylindrical shape according to
However, all other types of light waveguides can be welded to the fiber laser or coupled thereto in some other way, for example via optics.
One or more passive single-mode fibers or one or more other passive fibers 28 can also be coupled to an individual fiber laser instead of a brancher according to
However, it is also possible to unite the outputs of a plurality of fiber lasers or single-mode fibers or other suitable fibers into which laser radiation can be coupled via wavelength-dependent or polarized beam combiners or other suitable techniques, and to in turn couple into single-mode fibers or other fibers that can be provided with a respective, corresponding terminator at one or both ends.
The described possibilities of branching and uniting fibers can be particularly advantageously employed when the modular structure is applied to the laser radiation source.
It is advantageous for an arrangement having a plurality of tracks to arrange a plurality of such modulators on a common crystal 34 according to
Instead of the acousto-optical modulator, however, it is also possible to utilize other modulators, for example what are referred to as electro-optical modulators. Electro-optical modulators are described under the terms “laser modulators”, “phase modulators” and “Pockels cells” on pages F16 through F33 of the overall catalog G3, Order No. 650020 of Laser Spindler & Hoyer, Göttingen. Multi-channel electro-optical modulators have also been possibly employed, which is shown in the publication “Der Laser in der Druckindustries” by Werner Hülsbuch, Verlag W. Hülsbusch, Constance, page 523,
The fiber laser can also be directly modulated. Such directly modulatable fiber lasers that have a separate modulation input available to them are offered, for example, by IPG Laser GmbH D-57299 Burbach, under the designation “Modell YLPM Series”. The advantage is that the acousto-optical modulators and the corresponding electronics for the high-frequency sources can be omitted. Moreover, the transmission unit can be simplified, as shown in
It is possible to secure the electro-optical modulator 168 to the modulator housing (172) in a similar way and to contact it via the printed circuit board 171.
A distinction between more than 100 tonal value levels is required in high-grade multi-color printing in order to obtain adequately smooth color progressions; more than 400 tonal value stages would be optimum. When, for example, a cup in rotogravure wherein the volume of the cups determines the amount of ink applied onto the material being printed is composed of 8×8 or 16×16 small individual cups and the cup depth is kept constant, the processed surface can be quantitized into 64 or 256 stages. When, however, the cup depth is controlled by additional, analog or digital amplitude modulation or by a pulse-duration modulation of the laser energy, the volume of the cups can be arbitrarily finely quantized even given a low plurality of tracks. If, for example, the cup depth were digitally controlled in only two stages, as described in greater detail under
The modulators 34 as well as the strip mirror 46 are not shown in
The intermediate imager (191, 192) is shown in
An arrangement having strip mirrors can be combined very well with an arrangement having wavelength-dependent mirrors, as shown, for example, in
The modulators and the wavelength-dependent mirror are not shown in
In
First,
The lens 197 in
It is advantageous to separately modulate the individual lasers. This is especially suitable when a high number of lasers is employed, since, for example, a quantized modulation that is similar to an analog modulation, a quasi-analog modulation of the united laser radiation is then enabled by digital modulation of the individual lasers. However, it is also possible to modulate the beam bundles 144 of all lasers in common, for example with an acousto-optical modulator. In this case, the ultrasound field of the modulator cell must exhibit such a size that the overall beam bundle shown in
The cylinder optics (202, 203) is shown in
For removing the material eroded from the processing surface,
As a result of its specific shaping, the mouthpiece 82 prevents the described disadvantages. Preferably, it is secured to the laser gun with connections 204 that are simple to release, so that it can be removed and cleaned in a simple way and also enables a simple cleaning as well as a simple replacement of the objective lens (not shown) 61, 103, 112. A cylindrical bore 206 for adaptation to the objective lens and a preferably conical bore 207 as passage for the beam bundle as well as another preferably cylindrical bore that represents the processing space 211 are located in a preferably cylindrical base member 205. The distance of the base member 205 from the processing surface 81 should not be excessively great. The processing points (not shown) for producing the individual processing tracks on the material to be processed lie in the processing spot 24. A broad, all around extraction channel 212 is preferably located in the base member, this channel 212 being connected to the processing space 211 via a plurality of extraction channels 213 that should have a large cross-section. Preferably, 3 through 6 extraction channels 213 are present. A further, preferably all around admission channel 214 is located in the base member, this channel 214 being connected via nozzle bores 215 to the processing space 211 and to the conical bore 207 via smaller bypass bores 216. 3 to 6 nozzle bores 215 and 3 to 20 bypass bores 216 are preferably distributed over the circumference of the admission channel 214. All bores can be offset relative to one another and relative to the extraction channels 213 on the circumference. Further bypass bores can also be attached and directed onto the objective lens. This, however, is not shown. The base member is surrounded by a ring 217 applied gas-tight that contains a plurality of extraction connectors 221 in the region of the channel 212 to which extraction hoses are connected, these being conducted via an extraction filter to a vacuum pump. The extraction hoses, the extraction filter and the vacuum pump are not shown in
A generally known scraper device that, however, is not shown in the figures can be located in the proximity of the mouthpiece but need not necessarily be connected to it or to the laser gun. For example, the job of the scraper device is to scrape off the ejects arising at the edges of the cups during the processing process at rotogravure forms. Further, a brush device (not shown) can preferably be located in the proximity of the laser gun, this brushing out the cups that have been cut and ridding them of adhering dirt. Further, a measuring device (not shown) can be preferably inventively located at the laser gun, this measuring the position and/or the volume of the cups immediately after they are produced. In contrast to cups that have been manufactured by electromechanical engraving or with a single laser beam, the volume can be inventively more precisely identified for cups that are produced with the inventive laser radiation source and have steep edges and constant depth, in that the area of the cup is determined with a specific, fast camera and the volume is derived therefrom. It is thereby advantageous to measure a series of cups in order to reduce measuring errors. It lies within the framework of the preferred embodiments that specific control fields are engraved in a region of the rotogravure cylinder, this being provided for monitoring measurements and/or for monitoring prints. A rated/actual comparison can be produced with this measured quantity for the generated cups and with the cup size prescribed for this location. The result can then be employed in order to correct the position and/or the volume of the subsequently produced cups.
How the beam bundles focused by the lens 165 impinge the generated line M of the drum is shown in
As described under
It has been emphasized that the processing of the material in
It is also possible to cool the critical component parts of the laser gun 23 and of the pump source 2 with the assistance of what are referred to as micro-channel coolers, as described in the article “Lasers in Material Processing” in the publication SPIE Proceedings, Vol. 3097, 1997.
The principle of the described arrangement of laser outputs in a plurality of planes or in a plurality of tracks or in a plurality of tracks and in a plurality of planes or overlapping in a point also applies to the laser rays incident on the processing surface 81. A plurality of tracks or a plurality of levels or a plurality of tracks and a plurality of levels of laser beams can likewise be arranged on the processing surface according to this ordering principle or the laser beams can be arranged overlapping in a point.
The arrangement according to
The described arrangement for cutting and incising is not only suitable for processing semiconductor materials but can be employed for all materials wherein the precise production of patterns is important such as, for example, in manufacturing printing forms.
The various motion directions of the table 225 can be realized with the same element, whereby the motion directions can also be partly allocated to the table and partly to the profiled rail. The housing for the acceptance of individual components, the cooling system, the control for the lasers, the pump sources for the fiber lasers, and the terminators 26, 94 are shown, the arrangement for removing the material eroded from the processing surface and the machine control for the drives are not shown in the Figures.
It lies within the framework of the preferred embodiments that the rotating mirror can also be replaced by an oscillating mirror. It also lies in the scope of the preferred embodiments that the rotating mirror can be replaced by two oscillating mirrors, whereby the oscillatory direction of the one mirror, called “mirror u”, lies on the processing surface 81 in the direction referenced u, and whereby the oscillating direction of the other mirror called “mirror v”, lies on the processing surface 81 in the direction referenced v.
An arrangement having oscillating mirrors is especially well-suited for fast incising of photo-voltaic cells, as was described in detail under
As a result of the extremely high beam quality of the laser radiation source that derives due to the fiber laser working diffraction-limited, a nearly parallel laser beam bundle can be generated, as shown in
The deflection mirror and the objective lens are inventively combined with one another to form a unit and slide back and forth on a guide rail (not shown) in the direction v, so that a number of parallel processing tracks corresponding to the number of channels in the laser radiation source are registered on the processing surface (81) similar to previously with the rotating mirror 243 and the optics 245.
The guide rail is implemented as a bearing having very low friction, for example as an air bearing or as a magnetic bearing. The drive of the unit composed of the objective lens and the deflection mirror in the direction v and back respectively occurs with a thrust into the corresponding direction that, for example, is carried out by a preferably contact-free electromagnetic system, whereby the energy acquired from the deceleration of the moving unit is partially re-employed for the drive. Parts of the guide rail, deflection mirror and objective lens are, for example, accommodated in a closed space that contains windows for the entry and the exit of the laser radiation and can be evacuated in order to reduce frictional losses. The drive and guide rail represent a linear drive for the unit composed of the objective lens and the deflection mirror.
It lies within the framework of the preferred embodiments that the respective, true position of the moving unit can be determined for correction purposes via, for example, an optical reference track. An arrangement 249 serves for the removal of the material eroded from the processing surface 81. The advantage of such an arrangement is that it can be very cost-beneficially realized for long path lengths and high resolutions, and that it can be set to various formats by displacement of the one and/or other drive. A plurality of such units can also be arranged in parallel in order to increase the processing speed.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.
Claims
1-263. (cancelled).
264. A material processing system for processing a processing surface of a material, comprising:
- a mounting which receives said material with the processing surface;
- at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a laser beam at said outfeed end;
- said laser fiber outfeed end being spaced from said surface, and at least one of said laser beam and said processing surface being laterally movable with respect to each other;
- focusing optics through which said laser beam passes; and
- the laser beam output from said laser fiber outfeed end being diffraction-limited to permit said focusing optics to focus the laser beam onto said processing surface as a spot having a spot size sufficiently small to create a fine structure by removing material at said processing surface.
265. A system according to claim 264 wherein said focusing optics comprises a lens on a terminator connected to said laser fiber outfeed end.
266. A system according to claim 264 wherein said focusing optics comprises a laser gun having a lens.
267. A system according to claim 266 wherein said laser gun has a modulator which controls the laser beam.
268. A system according to claim 264 wherein the spot size is equal to or less than approximately 10 micrometers in diameter.
269. A system according to claim 264 wherein the spot size is equal to or less than approximately 20 micrometers in diameter.
270. A system according to claim 264 wherein the laser beam at the spot has a power of at least approximately 100 watts at full beam intensity.
271. A system according to claim 264 wherein the laser beam at said spot has a power density of at least approximately 107W/cm2 at full beam intensity.
272. A system according to claim 264 wherein said pump source comprises at least one laser diode.
273. A system according to claim 266 wherein:
- a housing is provided having said mounting for the processing surface;
- the pump source and an end of the laser fiber opposite the outfeed end are mounted in a fixed position with respect to said housing;
- the laser gun is mounted for lateral movement parallel to said processing surface; and
- said laser gun having at an output end adjacent said processing surface said lens and at an input end said modulator, said laser fiber outfeed end being connected to said input end of said laser gun and moveable as said laser gun moves.
274. A system according to claim 273 wherein one of said laser fiber outfeed end and an outfeed end of a passive fiber connected to said laser fiber are at said input end of said laser gun.
275. A system according to claim 264 wherein a reflection surface is positioned to deflect the laser beam when it is intended that it not strike said processing surface.
276. A system according to claim 264 wherein a sump is positioned to receive the laser beam when it is intended that it not strike said processing surface.
277. A system of claim 276 wherein a reflection surface is positioned to deflect said laser beam to said sump when it is intended that the laser beam should not strike said processing surface.
278. A system according to claim 277 wherein said reflection surface and sump are positioned on a laser gun after the outfeed end of the laser fiber.
279. A system according to claim 267 wherein a diffraction optics is provided between said lens and an output of said modulator.
280. A system of claim 264 wherein a modulator is located to modulate said laser beam from said outfeed end.
281. A system according to claim 264 wherein said pump source comprises a plurality of laser diodes having light outputs directed to said laser fiber.
282. A system according to claim 264 wherein said laser fiber comprises two surfaces positioned to reflect laser light in said laser fiber.
283. A system according to claim 264 wherein at least one of said laser fiber and a passive fiber connected to said laser fiber has a length which is significantly greater than a distance between said pump source and an input end of a laser gun.
284. A system according to claim 264 wherein said laser fiber is flexibly arranged in a pattern with bends to take up an excess length of said laser fiber between a laser gun and said pump source.
285. A system according to claim 273 wherein said housing has a controller, and wherein at a top side of said housing said flat processing surface is positioned along with said laterally moveable laser gun.
286. A system according to claim 264 wherein said laser fiber comprises an outfeed reflection surface and another reflection surface spaced from said outfeed reflection surface.
287. A system according to claim 267 wherein at one of said outfeed end of said laser fiber and an outfeed end of a passive fiber a terminator is connected with an optics adjacent an input of said modulator which converts the laser beam exiting the laser fiber with diverging rays to parallel rays which enter at the input of the modulator.
288. A system according to claim 264 wherein a terminator having an optics is adjustably attached to said laser fiber at said outfeed end to set a distance between an end of said core of said laser fiber and said terminator optics.
289. A system according to claim 267 wherein said modulator comprises an acousto-optical modulator which receives a control signal having a frequency which controls a deflection angle of the laser beam output from said modulator.
290. A system according to claim 267 wherein said modulator comprises an acousto-optical modulator and an amplitude of a control signal fed to said modulator controls an amplitude of the laser beam exiting from the modulator.
291. A system according to claim 275 wherein said reflection surface is positioned after an output of a modulator and is angled so as to direct said laser beam deflected by the reflection surface to a sump, said sump being attached to a laser gun radially outwardly from a longitudinal axis of said laser gun.
292. A system according to claim 275 wherein said reflection surface is positioned on a laser gun with respect to a longitudinal axis of said laser gun between an output of a modulator and a diffraction optics in said laser gun.
293. A system according to claim 267 wherein said modulator comprises an acousto-optical modulator on said laser gun and is positioned such that a control signal fed to said modulator controls an output angle of said laser beam from said modulator by a frequency of said control signal to selectively strike said processing surface through the lens.
294. A system according to claim 267 wherein said modulator comprises an acousto-optical modulator positioned in said laser gun such that given no control signal fed to said modulator the output laser beam from the modulator hits a reflection surface and given presence of the control signal with a prescribed frequency said laser beam output from said modulator passes through said focusing lens and hits said processing surface.
295. A system according to claim 279 wherein said diffraction optics is mounted in said laser gun, and, relative to a traveling direction of the laser beam, said diffraction optics causes a laser beam output from said modulator to diverge prior to passing through said lens.
296. A system according to claim 264 wherein said focusing optics comprises at least one lens and focuses the laser beam onto said processing surface to form a laser spot at said processing surface having a diameter equal to or less than approximately 10 um.
297. A system according to claim 264 wherein said material processing surface comprises a semiconductor.
298. A system according to claim 297 wherein said semiconductor comprises a wafer.
299. A system according to claim 264 wherein said laser beam is oriented so that the laser beam strikes said processing surface at an angle which is less than 90° relative to a perpendicular of said processing surface.
300. A system according to claim 264 wherein said laser fiber converts a relatively large diameter of a pump spot at said infeed end to a relatively much smaller diameter of the output laser beam from said core at said outfeed end of said laser fiber.
301. A system according to claim 264 wherein said laser fiber at said outfeed end connects to a passive fiber.
302. A system according to claim 264 wherein said laser fiber at said outfeed end connects to a terminator, said terminator having an open portion a lens.
303. A system according to claim 266 wherein a plurality of laser fibers are provided between said pump source and said laser gun, and a coupler which combines outfeed ends of said plurality of laser fibers being connected to said laser gun.
304. A system according to claim 264 wherein a plurality of fiber lasers are provided.
305. A system according to claim 266 wherein said laser fiber connects to a coupler having at its output end a plurality of passive fibers, output ends of said passive fibers being connected to said laser gun.
306. A system according to claim 267 wherein said modulator comprises an electro-optical modulator which changes a polarization direction of a laser beam passing therethrough, and wherein a polarization direction sensitive element follows said electro-optical modulator so that depending upon a polarization direction, the element either transmits a laser beam which is communicated to said lens and then to said processing surface, or deflects the laser beam.
307. A system according to claim 266 wherein a plurality of said laser fibers are provided connected to said laser gun for outputting onto said processing surface a plurality of said laser beams.
308. A system according to claim 307 wherein said plurality of laser beams are focused to a common spot.
309. A system according to claim 307 wherein said plurality of laser beams are arranged to provide spots along a line next to one another on said processing surface.
310. A laser system according to claim 266 wherein a plurality of said laser guns are provided spaced from each other adjacent to said processing surface and in a direction along and parallel to said processing surface, each laser gun being fed by at least one laser fiber.
311. A system according to claim 266 wherein in said laser gun between said focusing optics and said processing surface a base member having an inner cavity is provided with a transparent plate through which said laser beam passes on its way to said processing surface through said cavity, and after said transparent plate at least one extraction channel which extracts unwanted eroded material from said cavity.
312. A system according to claim 273 wherein the housing has at an upper side said mount and said movable laser gun positioned adjacent thereto, and wherein a lower portion of said housing has a controller, modulation signal unit, and a cooling system, the cooling system being connected to cool said pump source, and wherein said laser fiber extends between said pump source fixedly mounted in said lower portion of said housing up to said laser gun at said upper portion of said housing.
313. A system according to claim 264 wherein said laser beam striking said processing surface creates said fine structure as at least one of the laser beam and the processing surface move laterally with respect to each other.
314. A system according to claim 264 wherein said laser beam striking the processing surface is amplitude modulated to cause a changing intensity of said laser light beam for causing different amounts of said material to be eroded depending on an intensity of said laser light beam.
315. A system according to claim 264 wherein a penetration depth of said fine structure changes dependent upon an intensity of said laser light beam.
316. A system according to claim 264 wherein said fine structure comprises holes.
317. The system according to claim 264 wherein an intensity of said laser beam is controlled by a modulator in accordance with at least an 8-bit signal fed to said modulator.
318. A system according claim 264 wherein said structure comprises eroded material forming a line in the processing surface.
319. A system according to claim 264 wherein said material is used for creating a printed circuit board.
320. A system according to claim 264 wherein a modulation control of said laser beam allows adjusting a depth of said fine structure within a fraction of a micrometer.
321. A system according to claim 264 wherein the processing of the material comprises individual circuits cut from a semiconductor wafer.
322. A system according to claim 267 wherein the modulator is located on the laser gun and an optics is provided such that parallel rays of the laser beam leaving the modulator diverge and when the laser beam passes through the focusing optics rays of the laser beam converge.
323. A system according to claim 264 wherein the fine structure comprises eroded holes.
324. A system according to claim 264 wherein the laser beam erodes the processing surface as the mount moves the processing surface.
325. A system according to claim 264 wherein at least one of the outfeed end of the laser fiber and an outfeed end of a passive fiber connected to said laser fiber is moved during the structuring.
326. A system according to claim 264 wherein the processing surface comprises at least one of metal, ceramic, glass, semiconductor, rubber, and plastic.
327. A system according to claim 264 wherein the laser beam impinging on the processing surface creates the structure such that a shape of the structure is created independently of a size of the structure at the processing surface.
328. A system according to claim 264 wherein the laser beam impinging on the processing surface creates an area of the structure at the processing surface which is independent of its depth.
329. A system according to claim 264 wherein the laser fiber has an absorption efficiency of more than 60%.
330. A system according to claim 264 wherein the laser fiber core has a diameter which creates a laser radiation beam at its outfeed end having a diameter of approximately 10 μm or less.
331. A system according to claim 264 wherein said processing surface is substantially flat, and said mount moves the processing surface in at least two dimensions.
332. A system according to claim 273 wherein one of the laser fiber outfeed end and an outfeed end of a passive fiber connected to said laser fiber is directly connected at the input end of the movable laser gun and proceeds in a pattern with bends back to the pump source at a fixed location on the housing.
333. A system according to claim 264 wherein said material comprises at least a layer of a printed circuit board and the material at the processing surface is eroded to form at least one of bores and patterns of interconnects for the printed circuit board.
334. A system according to claim 264 wherein the laser beam at said spot has a power density of at least approximately 107 W/cm2.
335. A system according to claim 264 wherein the processing surface comprises a semiconductor wafer which is at least one of excised and cut to provide differing fine patterns on the surface.
336. A system according to claim 264 wherein the processing surface comprises a display screen structured by the laser beam.
337. A system according to claim 265 wherein said terminator comprises a body with an aperture receiving one of said outfeed end of said laser fiber and an outfeed end of a passive fiber connected to said laser fiber, the lens being provided at an end of said body, and said body being adjustable and positioned to adjust a spacing of said lens from one of said outfeed end of said laser fiber and said passive fiber outfeed end.
338. A system according to claim 264 wherein a plurality of fiber lasers are provided and wherein at least one of the outfeed end of said laser fiber and an outfeed end of a passive fiber connected to said laser fiber of each laser being arranged along a line and at a substantially same distance from said processing surface.
339. A system according to claim 338 wherein each of the laser fiber outfeed ends has a respective terminator with a lens thereon connected to the laser fiber.
340. A system according to claim 338 wherein said material comprises a semiconductor which is cut by each of the laser beams from the respective fiber lasers.
341. A system according to claim 264 wherein a plurality of fiber lasers are provided and respective outfeed ends thereof are commonly connected to a carrier.
342. A system according to claim 341 wherein the carrier is rotatable so that a spacing between the laser beams can be changed on the processing surface by rotating the carrier.
343. A system according to claim 341 wherein the carrier has a guide, each of at least one of the outfeed ends of the fiber lasers and outfeed ends of passive fibers connected to said laser fibers being mounted adjustably to the guide so that a spacing between the laser beams can be adjusted.
344. A system according to claim 341 wherein each of the laser fiber outfeed ends has a connected terminator and the terminator is mounted by a mounting element in adjustable fashion to the carrier.
345. A system according to claim 341 wherein the carrier is connected to a laser carrier guiding machine which allows movement of the carrier towards and away from the processing surface and also movement of the carrier in a direction parallel to the processing surface.
346. A system according to claim 345 wherein said carrier is rotatable by said machine about a vertical axis perpendicular to said processing surface.
347. A system according to claim 264 wherein the processing surface is substantially flat and the mounting comprises a table on which the material with the processing surface is positioned.
348. A system according to claim 264 wherein the mounting is moveable in at least one dimension.
349. A system according to claim 264 wherein the mounting is movable in at least two dimensions.
350. A system according to claim 264 wherein the mounting is movable in at least three dimensions.
351. A system according to claim 264 wherein the laser fiber outfeed end is stationary, the processing surface is stationary, and at least one optical element is employed which causes movement of the laser beam across the processing surface in at least one dimension.
352. A system according to claim 351 wherein the movement is in at least two dimensions.
353. A system according to claim 264 wherein the mounting is movable in at least in one dimension with the laser fiber outfeed end being stationary and at least one optical element is provided which moves the laser beam in at least one different dimension relative to the processing surface.
354. A system according to claim 264 wherein optical elements comprising a rotating mirror, a deflection mirror, and an optics are utilized to move the laser beam relative to the processing surface while the laser fiber outfeed end remains stationary.
355. A system according to claim 264 wherein a chamber is provided adjacent the processing surface through which the laser beam passes and which collects eroded material.
356. A system according to claim 355 wherein the chamber comprises a suction outlet.
357. A system according to claim 355 wherein the chamber comprises a gas inlet which, combined with a gas outlet, removes eroded material during the fine structuring.
358. A system according to claim 355 wherein said chamber comprises a glass plate closing off an end of the chamber and through which said laser beam passes.
359. A system according to claim 264 wherein the material with the processing surface comprises a pattern of photo-voltaic cells and a plurality of fiber lasers with respective laser beams are employed for the processing.
360. A material processing system for processing a processing surface of a material, comprising:
- a mounting which receives said material with the processing surface;
- at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a laser beam at said outfeed end;
- at least one of said laser beam and said processing surface being movable with respect to each other;
- focusing optics through which said laser beam passes; and
- the laser beam output from said laser fiber outfeed end being diffraction-limited to permit said focusing optics to focus the laser beam onto said processing surface as a spot having a spot size sufficiently small to create a fine structure by removing material at said processing surface.
361. A material processing system for processing a processing surface of a material, comprising:
- a mounting which receives said material with the processing surface;
- at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a laser beam at said outfeed end;
- said laser fiber outfeed end having a connected terminator with a lens, and the terminator being connected to a laser gun, said laser gun having an optics through which said laser beam directed through said terminator lens passes on its way to said processing surface, and wherein said terminator lens and said laser gun optics comprise a focusing optics;
- at least one of said laser gun and said processing surface being movable with respect to each other;
- the laser beam output from said laser fiber outfeed end being diffraction-limited to permit said focusing optics to focus the laser beam onto said processing surface as a spot having a spot size sufficiently small to create a fine structure by removing material at said processing surface.
362. A material processing system for processing a substantially flat processing surface of a material, comprising:
- a mounting which receives said material with the substantially flat processing surface, said material comprising at least one of a metal, a semiconductor, ceramic, plastic, and a rubber;
- at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a laser beam at said outfeed end;
- said laser fiber outfeed end being spaced from said flat surface, and at least one of said laser beam and said substantially flat processing surface being laterally movable with respect to each other;
- focusing optics through which said laser beam passes; and
- the laser beam output from said laser fiber outfeed end being diffraction-limited to permit said focusing optics to focus the laser beam onto said processing surface as a spot having a spot size sufficiently small to create a fine structure by processing material at said material processing surface.
363. A system according to claim 362 wherein said fine structure comprises cuts in a semiconductor material to divide up said semiconductor material into pieces.
364. A system according to claim 362 wherein said fine structure comprises holes in a semiconductor material.
365. A system according to claim 362 wherein said fine structure comprises eroded lines in said processing surface.
366. A method for processing a processing surface of a material, comprising the steps of:
- providing a mounting to receive said material with the processing surface;
- providing at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a laser beam at said outfeed end;
- providing a focusing optics through which said laser beam passes;
- providing the laser beam output from said laser fiber outfeed end as diffraction-limited to permit said focusing optics to focus the laser beam onto said processing surface as a spot having a spot size sufficiently small to create a fine structure by removing material at said processing surface;
- providing said laser fiber outfeed end at a spacing from said processing surface; and
- moving at least one of said laser beam and said processing surface with respect to each other and creating said fine structure by removing material at said processing surface.
367. A method according to claim 366 wherein the moving occurs during said removing of the material when creating at least a portion of said fine structure.
368. A method according to claim 366 wherein the fine structure comprises making holes in the processing surface.
369. A method according to claim 366 wherein said fine structure comprises cutting off pieces of said material at said processing surface.
370. A method according to claim 366 wherein said fine structure comprises eroding lines into said processing surface.
371. A method according to claim 366 wherein the spot size is equal to or less than approximately 20 micrometers diameter.
372. A method according to claim 366 wherein the spot size is equal to or less than approximately 10 micrometers diameter.
373. A method according to claim 366 wherein the laser beam at the spot has a power of at least approximately 100 watts at full beam intensity.
374. A method according to claim 366 wherein the laser beam at said spot has a power density of at least approximately 107 W/cm2 at full beam intensity.
375. A method according to claim 366 wherein said pump source comprises at least one laser diode.
376. A method according to claim 366 including the steps of:
- providing a housing for said processing surface mounting;
- mounting the pump source and an end of said laser fiber opposite said outfeed end in a fixed position with respect to said housing;
- connecting the laser outfeed end to a laser gun positioned adjacent said processing surface; and
- providing said laser gun at an output end adjacent said drum with a lens, and at an input end with a modulator, and providing at least one of said laser fiber outfeed end connected to said input end of said laser gun and an outfeed end of a passive fiber connected to said laser fiber and connected to said laser gun so that as the laser gun moves at least one of the laser fiber outfeed end and passive fiber outfeed end also moves.
377. A method according to claim 376 wherein one of said laser fiber outfeed end and passive fiber outfeed end is secured at said input end of said laser gun and moves along with said laser gun during the processing.
378. A method according to claim 376 wherein a reflection surface is positioned in said laser gun after an output of said modulator, a sump is positioned on said laser gun, and as said material is being processed, a laser beam from said modulator is deflected by said reflection surface to said sump.
379. A method according to claim 366 including providing a lens in front of a modulator through which said laser beam passes so that parallel rays from said modulator diverge prior to the laser beam entering the focusing optics.
380. A method according to claim 366 including providing a plurality of laser diodes having outputs directed to said laser fiber.
381. A method of claim 366 including the step of providing at least one of said laser fiber and a passive fiber connected to said laser fiber with a length sufficiently greater than a distance between said pump source and an input end of a laser gun.
382. A method according to claim 366 wherein after said outfeed end of said laser fiber a lens is provided so that the laser beam entering an input to a modulator has parallel rays.
383. A method according to claim 366 including the step of connecting said laser fiber at said outfeed end to a passive fiber.
384. A method according to claim 366 wherein a modulator is provided which comprises an acousto-optical modulator mounted in a laser gun and providing a control signal having a frequency which controls a deflection angle of the laser beam output from said modulator.
385. A method according to claim 366 wherein an amplitude of a control signal fed to a modulator controls an amplitude of the laser beam exiting from the modulator.
386. A method according to claim 366 wherein a modulator is provided which comprises an acousto-optical modulator and a control signal fed to said modulator controls by its frequency an output angle of said laser beam from said modulator to selectively strike said processing surface through said focusing optics.
387. A method according to claim 366 wherein a modulator is provided through which said laser beam passes.
388. A method according to claim 366 wherein said processing surface comprises a semiconductor.
389. A method according to claim 366 including the step of having said laser beam strike said processing surface at an angle which is less than 90 degrees relative to a perpendicular to a said processing surface.
390. A method according to claim 366 including the step of providing a plurality of fiber lasers.
391. A method according to claim 366 wherein an optics is provided so that diverging rays of the laser beam exiting the core of the laser fiber enter a modulator in parallel.
392. A method according to claim 366 wherein a modulator is provided which comprises an electro-optical modulator which changes a polarization direction of the laser beam passing there through, and wherein a polarization direction sensitive reflection surface follows said electro-optical modulator.
393. A method according to claim 366 wherein a laser gun connected to at least one of said fiber lasers outputs onto said processing surface a plurality of laser beams.
394. A method according to claim 393 wherein said plurality of laser beams are focused to a common spot.
395. A method according to claim 366 wherein a plurality of laser beams provide spots along a line next to one another on said processing surface.
396. A method according to claim 366 wherein a plurality of fiber lasers are provided spaced apart from each other adjacent to said processing surface.
397. A method according to claim 366 wherein said laser beam striking the processing surface is amplitude modulated to cause a changing intensity of said laser light beam for causing different amounts of said surface to be eroded depending on an intensity of said laser beam.
398. A method according to claim 366 including the step of providing a plurality of said fiber lasers each having a connected terminator at an end thereof, each terminator having a lens.
399. A method according to claim 398 wherein the terminators are positioned a same distance from said processing surface.
400. A method according to claim 366 including the step of connecting a terminator to the laser fiber.
401. A method according to claim 400 including the step of rotating the carrier to change a spacing between the laser beams from the respective terminators.
402. A method according to claim 366 including the step of providing a chamber which removes eroded material from the processing surface, said laser beam passing through said chamber.
403. A method according to claim 402 including the step of providing a vacuum in the chamber to remove the eroded material.
404. A method according to claim 366 wherein the mounting is moved in at least two dimensions.
405. A method according to claim 366 including the step of moving at least one of the outfeed end of the laser fiber and an outfeed end of a passive fiber connected to the laser fiber in at least one dimension.
406. A method according to claim 366 including the step of moving at least one of the outfeed end of the laser fiber and an outfeed end of a passive fiber connected to the laser fiber in at least two dimensions.
407. A method according to claim 366 including the step of providing at least one of the outfeed end of the laser fiber and an outfeed end of a passive fiber connected to the laser fiber in a fixed position and moving the laser beam with optical elements across said processing surface.
408. A method according to claim 407 including the step of moving the mounting in at least one dimension.
409. A method for processing a processing surface of a material, comprising the steps of:
- providing a mounting to receive said material with the processing surface;
- providing at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a laser beam at said outfeed end;
- providing a focusing optics through which said laser beam passes;
- providing the laser beam output from said laser fiber outfeed end as diffraction-limited to permit said focusing optics to focus the laser beam onto said processing surface as a spot having a spot size sufficiently small to create a fine structure by removing material at said processing surface; and
- moving at least one of said laser beam and said processing surface with respect to each other.
410. A method for processing a substantially flat processing surface of a material, comprising the steps of:
- providing a mounting to receive said material with the substantially flat processing surface, the material comprising at least one of a metal, a semiconductor, a ceramic, and a rubber;
- providing at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a laser beam at said outfeed end;
- providing focusing optics;
- providing the laser beam output from said laser fiber outfeed end as diffraction-limited to permit said laser gun to focus the laser beam onto said processing surface with the focusing optics as a spot having a spot size equal to or less than 20 μm to create a fine structure by processing material at said processing surface;
- providing said laser fiber outfeed end at a spacing from said processing surface; and
- moving at least one of said laser beam and said processing surface laterally with respect to each other and creating said fine structure by processing material at said processing surface.
411. A material processing system for processing a surface of a material, comprising:
- at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a continuous wave laser beam at said outfeed end;
- said laser fiber outfeed end being spaced from said surface, and at least one of said laser beam and said surface being movable with respect to each other;
- focusing optics through which said laser beam passes; and
- the laser output from said laser fiber outfeed end being diffraction-limited to permit said focusing optics to focus the laser beam onto said surface as a spot having a spot size sufficiently small to create a fine structure by processing material at said surface.
412. A system according to claim 411 wherein a modulator is provided after said outfeed end of said laser fiber to control said continuous wave laser beam.
413. A system according to claim 412 wherein said modulator changes an intensity of said laser beam.
414. A system according to claim 412 wherein said modulator controls whether or not the laser beam strikes said surface.
415. A system according to claim 411 wherein said surface comprises a printing form.
416. A method for processing a surface of a material, comprising the steps of:
- providing at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a continuous wave laser beam at said outfeed end;
- providing a focusing optics through which said laser beam passes;
- providing the laser beam output from said laser fiber outfeed end as diffraction-limited to permit said focusing optics to focus the laser beam onto said surface as a spot having a spot size sufficiently small to create a fine structure by processing material at said surface;
- providing said laser fiber outfeed end at a spacing from said surface; and
- moving at least one of said laser beam and said surface with respect to each other.
417. A method of claim 416 including providing a modulator through which said laser beam from the outfeed end of said laser fiber passes.
418. A method of claim 417 wherein the modulator changes an intensity of the laser beam.
419. A method of claim 417 wherein the modulator determines whether or not the laser beam reaches the surface.
420. A method according to claim 416 wherein the surface comprises a printing form.
421. A material processing system for processing a surface of a material, comprising:
- at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a pulsed laser beam at said outfeed end;
- said laser fiber outfeed end being spaced from said surface, and at least one of said laser beam and said surface being movable with respect to each other;
- focusing optics through which said laser beam passes; and
- the laser output from said laser fiber outfeed end being diffraction-limited to permit said focusing optics to focus the laser beam onto said surface as a spot having a spot size sufficiently small to create a fine structure by processing material at said surface.
422. A system according to claim 421 wherein a modulator is provided which internally modulates the pulsed laser beam.
423. A system according to claim 421 wherein a modulator externally modulates the pulsed laser beam.
424. A system according to claim 421 wherein an acousto-optical modulator within a laser resonator of the laser fiber modulates the pulsed laser beam.
425. A system according to claim 421 wherein said surface comprises a printing form.
426. A system according to claim 421 wherein said pulsed laser beam comprises a quality-switched laser beam.
427. A method for processing a surface of a material, comprising the steps of:
- providing at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a pulsed laser beam at said outfeed end;
- providing a focusing optics through which said laser beam passes;
- providing the laser beam output from said laser fiber outfeed end as diffraction-limited to permit said focusing optics to focus the laser beam onto said surface as a spot having a spot size sufficiently small to create a fine structure by processing material at said surface;
- providing said laser fiber outfeed end at a spacing from said surface; and
- moving at least one of said laser beam and said surface with respect to each other.
428. A method according to claim 427 wherein a modulator is provided which internally modulates the pulsed laser beam.
429. A method according to claim 427 wherein a modulator externally modulates the pulsed laser beam.
430. A method according to claim 427 wherein an acousto-optical modulator within a laser resonator of the laser fiber modulates the pulsed laser beam.
431. A method according to claim 427 wherein said surface comprises a printing form.
432. A method according to claim 427 wherein said pulsed laser beam comprises a quality-switched laser beam.
433. A material processing system for processing a surface of a material, comprising:
- at least one fiber laser comprising a pump source and a laser fiber having an outfeed end and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a laser beam at said outfeed end;
- at least one of said laser beam and said surface being movable with respect to each other; and
- the laser beam output from said laser fiber outfeed end being diffraction-limited to permit said laser beam impinging onto said surface as a spot to have a spot size sufficiently small to create a fine structure by processing material at said surface.
434. A method for processing a surface of a material, comprising the steps of:
- providing at least one fiber laser comprising a pump source and a laser fiber having an outfeed and a core surrounded by a pump core, said pump source being positioned at said laser fiber, and said laser fiber outputting a laser beam at said outfeed end;
- providing the laser beam output from said laser fiber outfeed end as diffraction-limited to permit said laser beam impinging onto said surface to have a spot with a spot size sufficiently small to create a fine structure by processing material at said surface; and
- moving at least one of said laser beam and said surface with respect to each other.
435. A method of claim 434 wherein said surface comprises at least a layer of a printed circuit board.
436. A method of claim 434 wherein at least two fiber lasers are provided outputting respective laser beams of at least one of different wavelengths and different polarization directions, and wherein the two laser beams are combined at said spot.
Type: Application
Filed: Jul 30, 2004
Publication Date: Jan 20, 2005
Inventor: Heinrich Jurgensen (Raisdorf)
Application Number: 10/909,670
