Abstract: A semiconductor laser adaptable for a 3-beam method, including a semiconductor laser chip bonded on a primary plane of a flat submount, the semiconductor laser chip having a thickness of 30 to 80 .mu.m is provided. Also provided is a method for manufacturing a semiconductor laser including the steps of: sequentially stacking layers of compound semiconductor materials on a semiconductor substrate to form a semiconductor laser wafer; mechanically abrading the semiconductor substrate to make it thin; subjecting the mechanically abraded face of the semiconductor substrate to a chemical treatment; forming an electrode film on both sides of the semiconductor laser wafer thus treated; and cutting the semiconductor laser wafer into chips and bonding each of the chips on a submount.

Abstract: At least two light sources are provided for an optical information recording/reproducing apparatus. The light sources emit a recording light beam and a reproducing light beam to form a recording light spot and a reproducing light spot on a recording medium. A wedge glass plate is interposed in the optical path of the beams. The wedge glass plate is rotated to adjust one or both positions of the recording and reproducing light spots formed on the recording medium.

Abstract: An optical data recording and reproduction apparatus which uses a semiconductor laser as a light source is disclosed. The half angle of light issuing from the laser in a junction direction of the laser and the focal length of a condenser lens adapted to focus a laser beam from the laser are adequately selected in such a manner as to satisfy a particular condition.

Abstract: An integrated light deflector and fabrication method are disclosed. In accordance with the method, a mold is constructed above the surface of a substrate using a thick photo resist and a mask to define a deflector plane. A collimated light beam is applied at an appropriate angle of incidence to the photo resist material and mask. The developed resist provides a mold into which the deflector body is cast, leaving a deflector body whose front surface serves as the deflecting surface.

Abstract: An optical pickup device includes an optical isolator provided in a beam path of an optical system for modulating the laser beam radiated from an end face of a semiconductor laser device and returning it to an end face of the semiconductor laser device, and a detector for detecting changes in an output of the return beam from the other face of the semiconductor laser device. The optical isolator transmits a beam component having the same plane of polarization as that of the laser beam. The magneto-optical recording medium may be reproduced by an optical system without employing a differential optical system.

Abstract: Method and apparatus for reading digital data stored on an optical tape are achieved with a digital optical tape read system including an optical tape and an illumination arrangement. The optical tape has bit cells which are stored along a plurality of tracks of bit cells. Each track includes a line of bit cells, and each bit cell has either a first spot power reflectance representative of a first binary value, or a second spot power reflectance representative of a second binary value. The illumination arrangement functions to illuminate a predetermined area of the optical tape covering a plurality of bit cells with incident light that provides substantially a 180.degree. phase difference between adjacent bit cell locations on the optical tape to be concurrently read.

Abstract: In an apparatus for optically recording data on and reproducing it from an optical disk, the level of a laser beam in reproducing mode is subjected to feedback control and the level of a laser beam in recording mode is controlled in accordance with the output of a capacitor which stores the level of the laser beam in reproducing mode. This apparatus monitors the output of a photodetector in a feedback circuit, which receives reflection light from the optical disk, and disables emission of a laser beam when a predetermined amount of light is not detected in recording or reproducing mode.

Abstract: A light signal detecting circuit which receives via a light detector light radiated from a laser diode oscillated as a multimode by a high frequency driving signal and reflected from an optical disk, amplifies a current signal proportional to the amount of the received light to a light detecting signal and outputs the signal, further includes a phase sensitive detector for selectively outputting from the current signal only a signal component having the same frequency and phase as the high frequency driving signal for driving said laser diode. Accordingly, a signal component with different frequency and phase from the output of laser diode is intercepted, and only a signal component with the same frequency and phase as the output of laser diode is detected.

Abstract: In an optical system including a laser diode with astigmatism such that the apparent source position in two orthogonal axes each normal to the beam direction differ, a beam prism expander and a collimating lens positioned between the diode and expander, the collimated lens is positioned relative to the laser such that the radius of curvature of the light beam exiting the beam expander in the two axes is identical.

Abstract: A focus error detecting apparatus in which a light emitting and receiving element including a light emitting portion and light receiving portions all of which are formed in a common semiconductor substrate, a hologram element diffracts a light beam reflected by an object to generate plus and minus first-order diffraction light beams and to introduce an astigmatism into the plus and minus first-order diffraction light beams such that shapes of spots of the diffraction light beams formed on the light receiving portions of the light emitting and receiving element vary into substantially reverse directions to each other, and a focusing condition is detected in accordance with outputs of the light receiving portions. Therefore, in this apparatus, positioning adjustment of the light receiving portions with respect to the light emitting portion is not necessary, and thus a number of the adjusting process can be remarkably decreased and the cost for manufacturing the apparatus can be reduced.

Abstract: An optical pickup comprises a substrate, an optical waveguide formed on the substrate, a semiconductor laser attached to the optical waveguide, and a grating formed on the optical waveguide and converging a waveguide light in the optical waveguide to an optical recording medium. On the substrate, there are provided a first light detector for detecting the waveguide light reflected from the optical recording medium, and a second optical detector for detecting the intensity of the waveguide light being guided in the optical waveguide. The quantity of laser beam light emitted from the semiconductor laser is controlled to be constant based on an intensity signal detected by the second light detector.

Abstract: An optical recording/reproducing apparatus comprises a semiconductor laser, and a drive circuit for supplying a drive current to the semiconductor laser. A light beam from the semiconductor laser is converged on a recording medium through an objective lens. A photodiode for receiving the light beam is provided within the semiconductor laser. A monitor output from the photodiode is input to an APC circuit. The APC circuit includes a reference value generator and an error detector circuit. The error detector circuit detects a difference between the monitor output and a reference value, and outputs a control signal for controlling the drive circuit so as to keep the monitor output constant. The APC circuit is turned on/off by a controller. With the APC circuit turned on, the controller detects the temperature or temperature variance of the on the basis of the drive current monitor signal from the drive circuit and the pre-stored data of the semiconductor laser with respect to temperatures.

Abstract: An optical pick-up for an optical disk has a semiconductor laser having an optical axis for generating a laser beam. An objective lens focuses the laser beam onto an optical disk disposed in the path of the optical axis of the semiconductor laser. A wavelength between the semiconductor laser and the objective lens has a plurality of input grating couplers for coupling the laser beam reflected from the optical disk into the waveguide for propagating beams in a plurality of directions. A plurality of output grating couplers radiate the propagated beams from the waveguide. A plurality of photodetectors detect the radiated beams from the output grating couplers.

Abstract: A device for processing optical data comprising a transparent substrate for a light to be applied, light source for projecting the diverging light onto one surface of the substrate substantially perpendicularly to the surface, lens provided on the substrate for causing the projected light to emerge obliquely or vertically upward from the other surface of the substrate and focusing the emergent light, photodetector provided on the substrate for receiving the light reflected from above, focusing drive mechanism for adjusting the position of the substrate upward or downward, and tracking drive mechanism for adjusting the position of the substrate laterally.

Abstract: A magneto-optic recording and regenerating process and the device using it in accordance with the present invention are intended to magnetize the magnetic, or magnet, film of a disk parallel to the plane of the magnetic film to record or erase information. When regenerating information, light beams whose incident plane is substantially perpendicular to the direction of magnetization of the recording medium is applied to the disk, so that the recorded information is regenerated dependent on the light intensity of reflected light obtained in response to the direction and magnitude of magnitization of the disk. Additionally, the magneto-optic disk includes a magnetic film having a coercive force smaller than the saturated magnetization at room temperature, so that irradiating light beams elevate the temperature of the magnetic film but not up to its Curie temperature. Information is then recorded on or erased from the magnetic film with its coercive force decreased by the elevated temperature.

Abstract: An optical information reading and writing system, comprising an optical recording medium and a multibeam optical head optically coupled to the optical recording medium. The optical recording medium has a plurality of uniformly spaced tracks in a radial direction of the medium for recording information thereon. The multibeam optical head is movable in the radial direction of the medium and includes a laser diode and an image forming optics. The laser diode has a plurality of nonuniformly spaced lasing elements in a straight line for generating a plurality of spaced laser beams. The image forming optics directs each laser beam onto a respective tracks of the optical recording medium. The spacing between the adjacent laser beams on the tracks corresponds to the spacing between the adjacent lasing elements.

Abstract: An optical read/write apparatus includes an optical device for directing a main scanning spot and a pair of satellite spots, one on either side of the main scanning spot, onto a recording. It further includes a wobbling device for moving the satellite spots in relation to the main scanning spot. The satellite spots are moved with an oscillatory motion in a direction perpendicular to tracks on the recording medium. A tracking control device detects light reflected from the satellite spots, generates a tracking error signal, and moves the main scanning spot according to the tracking error signal in a direction perpendicular to the. This keeps the main scanning spot accurately centered on a track without offset and without wobbling the main scanning spot.

Abstract: An array of diode lasers selected to emit at certain fixed wavelengths is assembled to temperature stabilzed Bragg reflectors to assure maintenance of the selected wavelength within 1 .ANG.. One laser is included in the array for each wavelength at which absorption will occur within a photochemically active optical storage medium. Each temperature stabilized laser is focussed by a lens onto an optical storage medium containing photoactive chemical components containing guest and hose molecules, as is known in the art. Light emitted by each laser will be used to burn a pit for each bit of data at the locations of the storage medium. One or more photodetectors located on the opposite side of the sotrage medium to detect the presence or absence of a hole with respect to the selected wavelength with which the hole was initially burned. A similar device is available with a temperature stabilized tunable laser which accurately controls the selected wavelength withing 1 .ANG..

Abstract: An optical recording/reproducing apparatus capable of detecting recording defects on an information recording medium comprises a beam irradiation device for irradiating a first beam, by which information pits are recorded on/reproduced from the information track on the information recording medium, a second beam preceding the first beam and a third beam following the first beam, along the information track; an optical detector having a plurality of light receiving surfaces for individually detecting the reflected light of the first beam, the second beam and the third beam, which have been reflected from the information recording medium; a monitoring device for, in a recording mode, monitoring the condition of the information track prior to and after recording in response to amount-of-light signals which respectively correspond to the reflected light of the second beam and the third beam; and a signal generator for, in a reproducing mode, producing a tracking error signal in response to the amount-of-light sig

Abstract: An optical information readout system including a record medium having a record layer capable of storing information and of reading the same optically, a resonating mirror arranged in substantially parallel to and apart at a predetermined distance from the record medium, a laser medium arranged between the record medium and the resonating mirror, a light source for pumping the laser medium, and a detector for detecting changes in a laser resonance, wherein the information recorded in the record medium is read by utilizing the surface of the recording medium as the other resonating mirror of the laser resonator and by detecting the changes of laser resonance resulted from the changes of the record medium surface by the detector.

Abstract: An optical pick-up device for focusing a laser beam emitted from a light emitting element through an optical system onto a recording medium. The beam is reflected from the recording medium and redirected through the same optical system on to a photodetector. A tracking error signal and a focusing error signal are produced from the output signals of the photo-detector. A diffracting element positioned before the light emitting element and the photo-detector and produces two sub-spots in two directions for applying the so-called 3-spots method from the laser beams that were projected from the light emitting element toward the recording medium. The diffracting element is divided into a first sub-region and a second sub-region formed in the same place and defined by a parting line aligned substantially perpendicular to the track direction. The first sub-region includes a diffraction grating for diffracting three beams that comprise a main beam toward the recording medium.

Abstract: An optical pick-up device for use in an optical disc information recording/reproducing apparatus is provided. In the present optical pick-up device, the functions of two or more separate optical elements provided in the prior art structure are combined or integrated in a single element to reduce the total number of separate optical elements provided in the device. In particular, use is made of a diffraction grating rather than lenses and/or lenses are formed as holo lenses. A diffraction grating and a holo lens may be formed substantially in the shape of flat plates, so that many optical components can be put together to define an integrated subassembly, which reduces the total number of discrete elements, facilitates manufacturing and eliminates the necessity of adjustments among optical elements once set.

Abstract: A focusing control system comprises a lens system having a plano-convex lens part and a cylindrical lens part formed as a unitary body such that an optical axis of the plano-convex lens and an optical axis of the cylindrical lens coincides with an optical axis of the lens system for receiving an incident optical beam reflected by the rotary recoridng medium at its one side and for transmitting the optical beam thus received to the other side of the lens system, and a photo detector array disposed so as to receive the optical beam transmitted from the lens system. The photo detector array has a quadrant detecting plane comprising four detecting sub-planes arranged in a row and column formation, and each of the sub-planes is connected to a corresponding photo detector which produces an output electrical signal when an optical beam transmitted from the lens system is irradiated on its detecting sub-plane.

Abstract: The present invention relates to a laser reproducing apparatus which reproduces recorded data recorded on a recording medium such as an optical disc, a magneto-optical disc or the like by the irradiation of a laser beam, in which the current value of a driving signal which drives a laser diode (12) is set near a value at which there is the least interference with the laser beam is by reflected-back light from the recording medium, and the irradiation by the laser beam from the laser diode (12) at the thus set current value is intermittently carried out at predetermined intervals. Also, the duration of lock pulse of this laser beam is selected to be a duration in which writing on the recording medium (11) cannot be carried out by the thus set current value. Thus, the influence exerted on the laser beam by the reflected-back light from the recording medium (11) is small so that the data can be reproduced satisfactorily.

Abstract: A method is described which enables automatic determination of the monitor sensitivity of a radiation emitting arrangement (in particular a laser diode and photodiode arrangement), which monitor sensitivity relates a level of a monitor signal (I.sub.M) generated by the arrangement to a corresponding optical output level (O.sub.L) of the arrangement. The method comprises the steps of: (i) supplying a varying drive signal (I.sub.L1,I.sub.L2) to the arrangement and measuring the rate of change (.DELTA.I.sub.M /.DELTA.I.sub.L) of the monitor signal (I.sub.M) with respect to the supplied drive signal (I.sub.L); and (ii) combining the measured rate of change with an assumed differential efficiency (k) of the arrangement to determine the monitor sensitivity (O.sub.L /I.sub.M) of the arrangement. The provision of a control system able to implement such a method eliminates the need for a factory adjustment in the manufacture of apparatus such as optical recording and/or reproducing apparatus.

Abstract: In an optical pick-up arranged to detect information recorded on an optical disk by causing laser light projected onto and reflected from a signal surface of the optical disk disposed within an optical system, to be received by a light receiving element provided in the optical system, a method of mounting onto the optical pick-up is provided with a laser diode unit which includes a metallic substrate, a laser diode, a photo-diode, a current feeding lead portion to the laser diode and a current output lead portion from the photo-diode, respectively disposed at one side face in the direction of thickness of the metallic substrate for emitting the laser light. The laser diode unit is positioned and fixed at a predetermined position of the optical system through a mounting member. The mounting method of the laser diode unit includes the steps of setting the other side face in the direction of thickness of the substrate and the mounting member in a desired positional relation for contact with each other.

Abstract: A laser beam control circuit for an optical recording/reproducing apparatus, which controls the intensity of a laser beam striking a magneto-optical disc. The control circuit controls the injection current to a laser diode to provide high intensity for recording and low intensity for reproducing, providing a smooth transition between the high and low intensity states, and avoiding any excessive transition current. The control circuit monitors the output power of the laser diode and maintains it at a first value in the reproducing mode and a second value in the recording mode, and further controls the output power so that even during switching, the output power does not exceed the second level. This is done by supplying a compensating reference voltage to the recording power control loop during the reproducing mode, so that the output of the recording error amplifier does not change abruptly when the operating mode is switched to the recording mode.

Abstract: A semiconductor laser controller converts the light output of the driven laser to a photovoltaic current proportional to that light output and separates the current into high and low frequency components. A negative feedback loop controls the forward current of the laser such that the sum of these high and low frequency components of the photovoltaic current equal a reference signal current defining the light output of the laser. A control unit controls the reference current such that a voltage proportional to the low frequency component of the photovoltaic current equals a reference voltage corresponding to the reference current.

Abstract: An optical information recording-reproducing system is provided using a laser diode with independent pulsating emission for recording and/or reproducing information, with the laser pulse period T (sec) and the distance L (m) between the semiconductor laser and information recording medium being set to meet the inequality:(n-1).times.0.8.times.c/2L<i/T<n.times.0.7.times.c/2Lwhere c is the velocity of light, and n is a natural number. By virtue of this arrangement, the relative noise intensity inherent to the optical feedback from the information recording medium is reduced below 10.sup.-3 Hz.sup.-1.

Abstract: An apparatus for recording and reproducing optical information comprises a laser beam source for emitting a laser beam; a collimator lens for forming light emitted from the laser beam source as an approximately parallel light beam; an objective lens for converging the approximately parallel light beam from the collimator lens in the shape of a spot on a recording face of an optical information recording medium; a device for recording and reproducing the optical information by converging the laser beam in the shape of a spot by the objective lens on the recording face of the optical information recording medium; a prism symmetrically arranged with respect to an optical axis in an optical path from the collimator lens to the objective lens; and a device for making a parallel light beam from the collimator lens through the prism incident to the objective lens so as to provide a light intensity distribution in which the light intensity in a peripheral portion of the optical axis is larger than that on the optical

Abstract: An optical pick-up for selective playback and recording on a magneto-optically recording medium, in which light is projected from a source onto the medium. The light is provided with a direction of a polarization, and is either reflected from the recording medium or is transmitted through the medium. The reflected or transmitted light becomes deflected onto a predetermined one of several photodetectors, depending on the direction of polarization of the light. The intensity of the reflected light or the transmitted light is held constant to minimize noise components that result from the optical properties of different recorded media as well as from the light. By holding the light intensity constant, moreover, precise readjustment to each of the different recording media that may be used, is not necessary.

Abstract: In case that the light beam emitted from a light source mounted on a base element is focused to a spot light on a data storage media to write the data, when the light beam reflected from the data storage media to return to the light source is reflected from the base element and focused again on the data storage media, it becomes difficult to precisely read/write the data on the storage media. In order to resolve the above problem, a light beam treating means is provided in the base element to prevent the re-incident light beams from being reflected toward the data storage media and focused thereon.

Abstract: An optical pickup apparatus is disclosed which comprises an optical detector formed on a substrate for detecting light reflected by a recording medium, a pattern formed on the substrate, a first block on which the substrate is fixed, a first reference surface formed on the first block substantially in parallel with an optical axis of the light to be detected, a second block arranged to be movable so as to be adjusted in a plane perpendicular to the optical axis and to support the first block, a second reference surface formed on the second block so as to correspondingly contact with the first reference surface; and a relay substrate fixed on the second block and electrically connected to the pattern.

Abstract: A beam controller for controlling a semiconductor laser provided in an optical recording/playback apparatus includes first and second current sources for driving the semiconductor laser at a low level (play-back mode) and/or at a high level (recording or erasing mode). The first and second current sources are controlled to have stable power automatically by a first and second auto-power circuits, respectively. The first and second auto-power control circuits include a sample-hold circuit which stores an output signal from a low-pass filter. This enables the beam controller to avoid the transition response problems of the low-pass filter. A switching circuit is also included to select either the stored low-pass filter signal on the present low-pass filter signal.

Abstract: An optical information recording and reproducing apparatus which radiates a plurality of beams onto an information recording medium to optically record information on the medium as well as reproduce the information just recorded. The apparatus includes a beam generator for radiating a plurality of beams of the same wavelength; an optical system for radiating the plurality of beams onto the information recording medium in such a manner that spots formed by the beams are arranged in the direction in which the information is being recorded, and for extracting the plurality of beams reflected by the information recording medium; and an optical detector for detecting each of the plurality of beams after they have been extracted by the optical system.

Abstract: A data reproducing apparatus is disclosed which permits stabilization of the light output of a light source, thereby to permit reliable reproduction of data. When recording data on an optical disk and also when reproducing the recorded data by illuminating the optical disk by means of a laser beam from a semiconductor laser, an idling current is supplied in advance to the semiconductor laser, to such an extent that the semiconductor laser does not emit a laser beam. As a result of the preliminary supply of the idling current, the output of the semiconductor laser is stabilized.

Abstract: An optical head device for use in a disc player has a light beam generating and detecting unit for generating a light beam emerging therefrom and detecting a light beam coming thereto from the outside, an object lens driving unit for supporting an object lens and moving the same in both a first direction along an optical axis of the object lens and a second direction substantially perpendicular to the first direction, and a movable base member for supporting the light beam generating and detecting unit and the object lens driving unit both mounted thereon so that the light beam emerging from the light beam generating and detecting unit is incident through a predetermined path upon the object lens supported by the object lens driving unit. In an embodiment, the movable base member is formed into the shape of a plate, and the light beam generating and detecting unit and the object lens driving unit are mounted respectively on opposite surfaces of the movable base member.

Abstract: Error correction in a feedback servo system. The feedback servo loop in, for example, a head positioning circuit in an optical disk data recording and retrieval system is provided with means for forcing the feedback signal to zero when the head is positioned at best focus as determined by a peak in the laser monitoring diode. The head in such a system must be dynamically maintained at a best focus position but, through use and transporting, the alignment of the head position error detecting system can be disturbed. In some cases, the loop circuit parameters may drift from their original values. To correct for errors introduced from such causes, the head is positioned at best focus and the focus error (head position error) signal is sensed. A correction system forces the sensed value to zero, e.g, by adjusting the gain of amplifiers used in the feedback loop.

Abstract: An optical pickup device having a semiconductor laser element mounted on a substrate, a photo detector formed on the substrate to receive a laser beam emitted from the semiconductor laser element and an optical element mounted on the substrate to cover the photo detector to branch the direction of optical path of the laser beam, the optical element having its face opposing the semiconductor laser element formed as an inclined face on which a semitransparent reflection film is deposited. The optical path branching optical element is provided with preventing means by which, of laser beams incident on the optical element, a laser beam reflected and/or scattered within the optical element is prevented from irradiating the photo detector.

Abstract: This device is an all-optical digital architecture for carrying out compuions. Residue number system addition and multiplication tables are produced on an optically-addressable plane composed of optically bistable material. The plane of optically bistable material devices represents a residue number system addition or multiplication tables and is addressed by two intersecting signal beams from the top and a bias beam from the bottom. A combination of two signal beams exceeds the material transmission threshold in the intersection region letting bias light emerge as a position encoded signal beam.

Abstract: The present invention has an object to provide a focus sensor or tracking sensor for an optical recording and reproducing device, which has a simplified optical system whose adjustment is much facilitated. The operational principle of this device is to produce a focusing error signal or tracking error signal by vibrating light spot on an optical disc with a small amplitude to scan interference fringes produced in the far field on an optical disc on the basis of a periodicity of information tracks of the optical disc and processing output signals of an optical sensor arranged in the far field.

Abstract: In case that the light beam emitted from a light source mounted on a base element is focused to a spot light on a data storage media to write the data, when the light beam reflected from the data storage media to return to the light source is reflected from the base element and focused again on the data storage media, it becomes difficult to precisely read/write the data on the storage media. In order to resolve the above problem, a light beam treating means is provided in the base element to prevent the re-incident light beams from being reflected toward the data storage media and focused thereon.

Abstract: An integrated optical head includes a substrate and an optical waveguide formed on a surface of one side of a substrate. Light is directed to the optical waveguide and a grating structure is provided for deflecting light propagating in the optical waveguide toward the substrate. A distributed refractive index lens is formed in the substrate for condensing the light passing through the substrate after the deflection toward an article.

Abstract: A system for recording data onto optical tape by means of a laser. The optical tape may be disposed on reels and transported along a tape path between supply and takeup hubs. A laser or laser array is used to write data on the tape in a plurality of parallel tracks as it is driven along the tape path. The tape features a flexible web backing, a reflective metallic layer deposited over the backing and an optical storage layer on top of the metallic layer with a planar crust of irregular, nonfilamentary and oblong black silver particles within the top one-half micron of the storage layer and substantially clear gelatin below the crust. The tape may have prepatterned indica, such as servo track guides or timing marks. Laser recording modifies the black silver particles of the crust to expose the reflective underlayer through the clear gelatin. The laser at low power together with a light detector may be used to read the data, an optical reflective contrast ratio of at least 1.

Abstract: Transparent cache memory for data processing system in which a central processing unit requests the read out of information contained in a working memory at a current address and immediately receives, without waiting, the requested information from the cache memory if the requested information is contained in the cache memory. Meanwhile the cache memory performs the reading and the storing into the cache, of information contained in the working memory at the address next following the current address, so as to advance a possible subsequent request of the central processing unit. If the requested information is not contained in the cache memory, the cache memory performs a double memory read in page mode at the current memory address and at the next following address, thus minimizing the occupation time of the memory. The double reading is performed only for those addresses which allow for page mode operation.

Abstract: An optical pickup comprising a semiconductor laser, a first waveguide for leading light emitted by the semiconductor laser to recording medium and coupling again light returning from the recording medium; splitting element for separating the light returning from the recording medium from the first waveguide path; and a second waveguide propagating light returning from the recording medium and separated by the splitting element; wherein light going towards the recording medium and light returning from the recording medium propagate separately in the first and the second waveguide so that the utilization efficiency of the light is increased.

Abstract: An optical recorder such as a data recorder has an interchangeable, prealigned laser diode/lens module arrangement which can be readily replaced without complex realignment of the recorder. The module includes a cylindrical outer housing/heat-sink, and a tiltable yoke within the outer housing/heat-sink. A heat pump such as a thermoelectric element has a hot side coupled to the yoke, and also has a cold side. A combination mount is at least thermally cantilevered from the cold side of the thermoelectric element, and is thermally isolated from adjacent structures. A laser diode is bonded to a structure within the combination housing, and a lens is loosely mounted at the light-emitting end of the combination housing. The module is prealigned by operating for a period sufficient to achieve thermal stability in a fixture which is dimensionally identical to the optical recorder with which the module is to be used.

Abstract: The hold mode period of a sample/hold circuit disposed in a control system for controlling a laser diode so as to keep constant luminous power contains the information signal write period, and a third drive circuit for making proper the low level of modulation current of the laser diode is disposed to maintain the low level of laser light in write operation at the proper value.

Abstract: An apparatus for optically scanning a surface, such as the information surface of an optical record carrier. An error in focus of the scanning spot on the surface is detected by providing two gratings in succession in the path of the beam reflected from the surface. The grating periods of the two gratings are related in accordance with the nominal beam divergence at zero focus error, and the grating strips thereof are parallel but offset with respect to each other. A bounding line between detectors in a composite radiation-sensitive detection system extends parallel to the grating strips. An interference pattern of light and dark bands is projected by the second grating on the detection system, such pattern having an intensity distribution which varies with variations in focus error and can be enhanced by an appropriate value of the offset between the two gratings.

Abstract: A structure of an optical pickup. The optical pickup has a substrate used for an optical recording medium. The optical pickup is provided with a device for condensing and radiating a polarized light and a light receiving device for receiving, through an analyzer set in a crossed Nicol state, the reflected light of this substrate or the above mentioned polarized light on the light transmitted side. The amount the C/N (carrier to noise ratio) is reduced or increased based on the substrate may be evaluated by the light amount received by the light receiving device.