Abstract: An information recording apparatus includes a record signal processor for converting information to be recorded into an analog signal having three levels or more, a laser beam source for emitting a laser beam whose power is modulated at multiple levels in accordance with the three levels or more of the processed signal, and an optical system for focusing/radiating the laser beam on an information recording medium. The information recording medium has a recording layer. The laser beam whose power is modulated at the multiple levels is radiated on the recording layer. As a result, a plurality of phases having different crystallinities are obtained in a radiated portion in accordance with the laser power, and hence multi-level information is recorded in the data recording medium. The recorded information can be reproduced by detecting optical characteristics in these phases.

Abstract: An optical memory device for recording, reproducing, or erasing information applies an optical beam such as a laser beam onto a recording medium. The optical memory device includes a recorded region detecting circuit for detecting information recorded region formed in the recording medium. In the optical memory device, a timing control for recording, reproducing, or erasing is performed with the use of a result obtained through detection of a synchronizing signal, such as a sector mark, indicative of a starting point of an information block and another result obtained through detection in the recorded region detecting circuit. The recorded region detecting circuit includes either at least one peak hold circuit for detecting a peak level of the playback signal or a low pass filter for smoothing the playback signal, and a comparator for comparing an output obtained through the peak hold circuit or through the low pass filter with a reference voltage.

Abstract: An optical card recording/reproducing apparatus for recording/reproducing information onto/from an optical card by relatively moving the optical card to an optical head is provided. The optical head has an optical system for producing focusing and tracking control signals. The optical system includes a light emitting diode having a narrow slit-like light emitting surface as a light source. The optical system has photo sensitive elements for focusing control, a photo sensitive element for tracking control, and a recorded information reproducing photo sensitive element which are used to detect the reflected lights from the optical card of a slit light which is emitted from the light emitting diode. By forming a slit-like light spot onto the optical card, the focusing and tracking controls can be accurately easily executed and the deterioration in pits and track guides is prevented.

Abstract: An optical head in use with an optomagnetic disk apparatus employs a polarized beam splitter when information is recorded on and read out from a recording medium. In the optical head according to the present invention, the polarization plane of the polarized beam splitter is arranged so that it makes an angle of substantially 45.degree. with the polarization angle of the polarized laser beam entering the polarized beam splitter, whereby the optical head according to this invention does not use a 1/2 wavelength plate which is indispensable to the conventional optical head. In addition, the assembly and adjustment of the optical head according to the present invention are simplified.

Abstract: An apparatus for reproducing an optically recorded information on an optical record medium is disclosed in which a plurality of light sources which irradiate light beams on a plurality of record tracks are illuminated in a time sharing mode and a reproduced signal derived by a receipt of reproduced lights with a signal photo detecting element is processed so as to reproduce the information on the tracks, whereby a crosstalk due to the light sources which simultaneously irradiate the light beams on the plurality of mutually adjacent record tracks can be avoided and a simple construction of the optically recorded information reproducing apparatus can be achieved.

Abstract: A method and apparatus for reducing the number of errors generated when reading digital data stored on a recording medium such as film, the method comprising passing light of two different frequencies (i.e., two different frequency bands) through the film, one frequency being modulated by digital data stored on the film and the other being unaffected by the stored data. The light that is unaffected by the stored data is modulated by debris on the film such as dirt and is used to flag data bits that may be in error to thereby facilitate an error correction process. In the first disclosed embodiment the two frequencies of light are processed separately to obtain the digital data and error flags. A second embodiment combines all light passing through the film to produce digital information that includes error flags.

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 disk cutting apparatus comprises an exposure optical system for expanding an exposure laser beam and for modulating the exposure laser beam in response to a signal to be recorded, and a focus servo optical system for expanding a focus servo laser beam and for detecting a reflected beam from a master recording disk through a polarizing means, in which one of the exposure and focus-servo optical systems the laser beam of which has a wave length longer than that of the other one includes a focusing lens provided in a stage preceding the objective lens for focusing the expanded laser beam. Therefore, it is possible to make the respective focal positions of the exposure laser beam and the focus servo laser beam be substantially the same and to obtain a small aberration by means of the difference in refractive index between laser beams.

Abstract: An erasable optical disk drive system is disclosed which utilizes an electron trapping media coated on the disk surface to store data in the form of light energy and which utilizes three laser beams, each having a wavelength range distinct from each other as well as distinct from the wavelength range of the emission produced by the impingement of the read laser onto the electron trapping media. Data is written onto the disk, which is contained in a light-tight contamination-free environment, using a visible light laser beam. Data is read from the disk and the disk is erased by using a near infrared light laser beam. The focus and tracking functions of the disk drive system are accomplished by using a laser beam having yet another range of wavelengths, which are greater than those of the visible light laser beam and those of the photon emission from the electron trapping optical memory media, but less than those of the read/erase laser.

Abstract: A high-density magnetic recording and optical reproducing apparatus for magneto-optically reproducing information magnetically recorded on information tracks on a recording medium, the apparatus comprising two laser beam sources emitting laser beams having different wavelengths respectively, an optical system for directing the laser beams from the two laser beam sources toward and onto the recording medium so as to irradiate the recording medium with laser beam spots partly overlapping each other, two photo detectors detecting the laser beams reflected from the surface of the recording medium, and a differential amplifier detecting the difference between the output signals of the two photo detectors thereby generating the differential signal as a reproduced output.

Abstract: The present invention relates to a method of recording on a rewritable recording medium using a laser beam capable of producing at least three discreet levels of power. The three levels of power used for writing to the recording medium is greater than the power required for reading. The present method is unique in that the power level of the laser beam is modulated between high, intermediate, and low levels over a time period so that at least three discreet power levels are radiated to the recording medium during recording. The increment of the radiation energy of the upward pulse from the intermediate level toward the high level is within the range of 0.8 to 1.2 times the decrement of the radiation energy of the downward pulse from the intermediate level to the low level. The present invention provides high density recording capability with minimum non-erasure areas even when the recording medium is formed from a high velocity crystallization (high speed erasure).

Abstract: A method of optically writing an information over an information recorded on a recording material which is reversively convertible between a stable phase and a metastable phase to show different light reflection or transmission by controlling a heating condition to be applied to the recording material wherein the recorded information is recorded in the form of a plurality of separated metastable-phase areas on a stable-phase area is disclosed.

Abstract: An optical recording/reproducing module comprises a housing defined with a depression, a focusing actuator provided on one side of the housing for carrying an objective lens such that the lens is movable in a direction perpendicular to the aforementioned one side, an optical system accommodated in the depression, the optical system includes an optical source for producing a first optical beam to be directed to the objective lens, an optical detector for detecting a second optical beam received by the objective lens and incident to the optical detector, the optical detector further produces an electrical output signal responsive to the second optical beam, and an array of optical elements for guiding the first optical beam produced by the optical source to the objective lens and for guiding the second optical beam received by the objective lens to the optical detector, a cover lid adapted to be mounted on the one side of the housing, the cover lid has a shape adapted to close the depression, and an electrical

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: 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 optical head apparatus for optical disks has a recording and reading laser beam generator and a wavelength reducer including reducing the wavelength of light from the laser generator. The laser beam generator is a separate unit from the head slider portion, the two being connected by an optical fiber which is used to transmit the recording and reading laser light to the slider. This arrangement enables short-wavelength laser light below 550 nm to be used for writing and reading operations without increasing the weight of the slider, thereby offering high-speed access and high recording densities.

Abstract: Method and apparatus for measuring nanometer or picometer surface displacements in a target surface. A laser beam is directed against the target surface, and time-dependent variations in laser output power are measured. These variations, which are due to non-specular reflection of the incident beam by the target and reentry of the retroreflected light into the laser cavity, are used to determine time-dependent displacements at the target surface, based on a linear relationship between the measured power variations and surface displacements. The invention is useful for determining microscopic surface features of a surface, for high-density laser optical disc data storage and retrieval, and as an ultrasensitive transducer for sound or mechanical vibrations.

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: An optical information recording/reproducing apparatus includes signal recording means for recording a signal on a film. The signal is recorded by raising the temperature of the film with a writing laser beam. A signal reproduction apparatus reproduces the signal by irradiating the film with a reading laser beam. There is an optical system provided in common to both the writing laser beam and the reading laser beam. The signal recorded on the film is reproduced substantially simultaneously with the recording of the signal in order to allow for confirmation of the signal that has been recorded. A modulating circuit is provided for modulating the intensity of the writing laser beam with a frequency of at least twice as high as the maximum frequency of the signal to be recorded.

Abstract: A magneto-optical disk recording apparatus sequentially pulse-drive a plurality of semiconductor laser elements in a time-divisional manner so that spots of light are sequentially formed along a plurality of recording tracks of a magneto-optical disk with clock information recorded in advance along a plurality of recording tracks thereon. A magnetic modulating signal is generated by combining pieces of information desired to be recorded along the plurality of recording tracks so that a modulating magnetic field whose polarity is reversed in accordance with the magnetic modulating signal is applied to the plurality of recording tracks by means of a magnetic head.

Abstract: Autofocus apparatus for use in an optical system utilizing a recording medium formed from a birefringent medium and a radiation-sensitive medium. The autofocus apparatus automatically focuses radiation through the birefringent medium and substantially at the interface between the birefringent medium and the radiation-sensitive medium and includes a source of linearly polarized radiation, a quarter-wave plate to convert the linearly polarized radiation to circularly polarized radiation, and an actuator controlled lens for focusing the radiation onto the recording medium, whereby radiation reflected from the first surface of the birefringent medium and the interface between the birefringent medium and the radiation-sensitive medium passes back through the lens and quarter-wave plate and is deflected by a beamsplitter to a polarization detector. The polarization detector isolates polarization components which arise from reflection at the interface and the isolated polarization components impinge upon a detector.

Abstract: Provided is a process for the erasure of information recorded in an optical information medium. The erasure is effected by irradiating the medium with a laser beam, with the duty cycle, laser power and focus offset having been adjusted from that used during writing such that upon the irradiation complete and clean erasure of the information is effected. It is preferred that the focus offset and laser power are adjusted the minimal amount possible and that the duty cycle is the parameter of the three for which the greatest adjustment is made. Control and adjustment of the three parameters in accordance with the present invention permits one to realize more accurate, efficient and clean erasure, even bit-by-bit erasure if desired, than has heretofore been possible.

Abstract: An apparatus and method are provided for recording images on photon sensitive recording media (20) which includes a source (12) of image pixel data in digital form having a multiplicity of possible intensity values, a photon generator 16 for exposing the photon sensitive recording media at a fixed intensity level, and a controller (24, 22, 14) for controlling the amount of time of exposure of the recording media in correspondence with the pixel data intensity values from the source. Previously known apparatus either have problems producing clearly distinguishable shades of gray on the recording media or else require much more expensive technology. The most likely applications are the production of hard copy from medical imaging data where clarity and detail are the most important consideration. Other applications may prove feasible with any form of digitizable image data.

Abstract: An optical information carrier includes a cylinder (1) with a recording layer (2) and bushings (3,4) located at butt ends of the hollow cylinder (1) and insulating the recording layer (2) from the environment. A method for erasing information recorded on the optical carrier uses a high-frequency electrical discharge produced inside the air-tight closed space (5) of the hollow cylinder (1). An optical storage device realizing the method includes an erasing unit (11) having a circuit for initiating a high-frequency discharge, which has electrodes (12,13) between which the optical carrier (10) is located so that the high-frequency discharge is initiated inside the closed air-tight space (5).

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: When it is detected that the light spot stays in a same track for a time exceeding a predetermined length of time, the light spot is moved to any other track. Thus, the light spot is prevented from staying on a same track for a long time without recording/reproducing data.

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: Phase array apparatus for use with a lens system to provide a substantially smooth, uniform image of a laser array comprised of a multiplicity of lasers wherein the phase of the radiation emitted by the lasers alternates by an amount which is substantially equal to 180.degree.. The phase array includes: (1) phase means, disposed substantially at a far-field image of the laser array formed by the lens system, which far-field image comprises two prominent lobes, for changing the phase of the radiation in the two prominent lobes by 90.degree.

Abstract: A recording medium for wavelength selective optical data storage has at least one memory element on which information is recorded by creating recording holes on the absorption spectrum thereof. The spectrum has at least one prerecorded hole for identifying the wavelength positions of the recording holes.

Abstract: An optical information carrier includes a cylinder (1) with a recording layer (2) and bushings (3,4) located at butt ends of the hollow cylinder (1) and insulating the recording layer (2) from the environment. A method for erasing information recorded on the optical carrier uses a high-frequency electrical discharge is produced inside the air-tight closed space (5) of the hollow cylinder (1). An optical storage device realizing the method includes an erasing unit (11) having a circuit for initiating a high-frequency discharge, which has electrodes (12,13) between which the optical carrier (10) is located so that the high-frequency discharge is initiated inside the closed air-tight space (5).

Abstract: A micro optical head, for optically reading and/or writing digital data on a recording medium in which digital data 1 and 0, corresponding to a high reflection factor and a low reflection factor, is composed of a self-coupled semiconductor laser located close to the recording medium. A bias current of the laser is determined so that it is smaller than a first threshold current, in which the medium has a low reflection factor, and is higher than a second threshold current, in which the medium has a high reflection factor. Output light of the laser is either strong stimulated emission light, corresponding to the high reflection factor, or weak spontaneous emission light, corresponding to the low reflection factor. The present head is carried on a flying slider with a spacing length less than several .mu.m which provides a small beam spot of about 1 .mu.m, and has an excellent signal to noise ratio.

Abstract: Disclosure is made of an optical memory wherein a cylindrical information carrier (2) is disposed in a stationary cylindrical container (14) filled with a liquid or gaseous medium transparent for the radiation flux emitted by a source (1) of modulated coherent radiation. The cylindrical information carrier (2) is equipped with a rotational drive. A recording coating (12) is applied on a tubular base (11) of the cylindrical information carrier (2). The cylindrical information carrier (2) is optically connected with the source (1) of modulated coherent radiation and with an addressing unit (3) arranged so that its optical elements can move axially with respect to the cylindrical information carrier (2).

Abstract: A polarization-rotator (22) and a polarization-sensitive beam combiner (30') are arranged in the radiation path between a phase-locked diode laser array (10) radiating in a stable supermode and a collimator lens (46). The two radiation lobes (11, 12) are superposed so that a single radiation spot (S) can be obtained. The quality of the spot can be improved by an arrangement of a prism system (40) and a spatial filter (45) in the lateral far field.

Abstract: Disclosure is made of an optical storage device wherein a cylindrical information carrier (2) with a recording medium (12) applied on a tubular base (9) is disposed in a stationary cylindrical container (3) having a window (4) in the lateral wall thereof. A lens (5) is secured in the window (4) of the cylindrical container (3) to let through the radiation flux from a source (1) of modulated coherent radiation. The cylindrical container (3) is filled with a liquid or gaseous medium transparent for the radiation flux. The length of this cylindrical container (3) is at least twice as long as that of the recording coating (12) applied on the tubular base (9) of the cylindrical information carrier (2) equipped with drives for rotation and axial motion.

Abstract: An optical type head device comprises a laser beam source for emitting a laser beam, a light focussing means for converging the laser beam on a data storing surface of an optical type data storing medium, a laser beam detecting means which receives the laser beam reflected by the optical type data storing medium and modulated by data held by the same, and converts the data into electric signals, a driving current supplying means for supplying a driving current to the laser beam source. The driving current supplying means comprises a high frequency current generator which supplys to the laser beam source a high frequency current having a waveform ranging from the lower part of the threshold value at which the laser beam source starts emission of the laser beam to the higher part of the thresheld value, and the frequency of the high frequency current is at least twice as high as the maximum frequency component of information which is contained in the data storing medium.

Abstract: An optical recording and reproducing apparatus comprises an optical disc having a recording surface; a laser diode emitting a laser beam; an optical lens for changing the laser beam into a parallel laser beam; a diffraction grating for diffracting the parallel laser beam and generating 0-order and .+-.1st diffracted lights, a light intensity ratio of each of the .+-.1st diffracted lights to the 0-order diffracted light ranging from 8:1 to 9:1; and an optical system for forming spot lights of the 0-order and .+-.1st diffracted lights on the recording surface of the disc and extracting the 0-order and .+-.1st diffracted lights which have been reflected from on the recording surface.

Abstract: A digital information recording and reproducing method for significantly improving the transfer rate of digital information, comprises the steps of: forming a plurality of light beam guide tracks on a recording medium capable of multiple light-wavelength recording, the tracks being spaced apart by a predetermined pitch and each of the tracks comprising a series of pre-pits disposed in a scan direction and spaced apart by an interval longer than the diameter of a spot of a light beam for use in recording and reproducing; and recording and reproducing an information bit by changing the light beam to have a different wavelength predetermined n times in a predetermined order while the light beam is scanned by one interval of the pre-pits.

Abstract: An optical data storage and readout apparatus having an optical head which includes a light source device for producing laser beams, a device for converging the laser beams on a selected area of a surface of an optical recording medium on or from which information is recorded or read out, and an optical detecting device for detecting signal beams reflected by or transmitted through the selected area of the recording medium which is irradiated by the converged laser beams. The optical head has at least one light-emitting optical fiber which receives at its one end the laser beams from the light source device and emits the laser beams from its other end toward the surface of the recording medium. The optical head further has a plurality of light-receiving optical fibers which receive at their one end the signal beams from the selected area of the recording medium, and transmit the signal beams to the optical detecting device.

Abstract: In a recording/reproducing optical system of the invention, which comprises a semiconductor laser causing single transverse mode oscillation and having beam radiation angles of .theta..perp. and .theta..parallel. in planes normal and parallel to an active layer, respectively; a collimator lens having a focal length f.sub.c ; an anamorphic optical element having a magnification ratio of 1:.beta. in two directions crossing each other at right angles; and an objective lens having a focal length f.sub.0, a numerical aperture NA.sub.0 and an aperture 2A.sub.0, and in which ratios A.sub.0 /W.perp. and A.sub.0 /W.parallel. of the apertures to diameters 2W.perp. and 2W.parallel., on the planes normal and parallel to the active layer, of beams which are emitted from the semiconductor laser, pass through the collimator lens and the anamorphic optical element and are incident to the objective lens have the following relations with predetermined values fi.perp. and fi.parallel.:A.sub.0 /W.perp..ltoreq.fi.perp.A.sub.0 /W.

Abstract: An optical information recording and reproducing system comprises a light source for emitting a working beam from a front end thereof and a monitoring beam from a rear end thereof, an optical system control circuit, a loop gain adjusting circuit and a photo detector. The monitoring beam emitted from the rear end of the light source is detected by the photo detector, and the loop gain of the servo loop control circuit for the focusing and/or tracking is automatically adjusted by means of the loop gain adjusting circuit according to the detected signal so that a desired closed loop control of the working beam can be performed according to the operation modes and the light beam power variation.

Abstract: There is disclosed a tracking error detecting apparatus for an optical head, which includes a semiconductor laser apparatus, a diffraction grating, a beam splitter, an objective lens and a photo-detector, in which a laser beam from the semiconductor laser apparatus is divided into a main beam and two side beams at both sides of the main beam by the diffraction grating, the three beams are introduced through the beam splitter and the objective lens to an optical recording medium, beams reflected on the optical recording medium are introduced through the objective lens to the beam splitter and reflected thereon, the reflected beams are made incident on the photo-detector and detected outputs of at least two beams of the three beams from the photo-detector are used to produce a tracking error signal corresponding to the tacking state of the main beam on the optical recording medium.

Abstract: An information reading apparatus for reading information includes a board having a plane optical waveguide and a light source on the board. Light beam emitted from the source is conducted by a first optical system to a predetermined direction through the waveguide. Part of the light beam is deffracted toward a second optical system by a surface elastic wave region formed in the waveguide. The second optical system conducts the light beam to an information recording region of a card through the waveguide and leads reflected light beam from the information recording region to a photodetector. The light beam not diffracted by the elastic wave region is conducted to a third optical system formed in the waveguide. The system conducts the light beam to a synchronizing signal recording region of the card and leads reflected light beam from the synchronizing signal recording region to a photodetector.

Abstract: An optical head for a laser memory disk in accordance with the present invention containing a substrate (1); a waveguide layer (3) formed over a main surface of the substrate; a semiconductor laser (4) provided at an end of the waveguide layer for injecting laser beams into the waveguide; a focusing grating coupler (6) formed on the waveguide layer for focusing the injected laser beams on the disk and introducing beams reflected back from the disk into the waveguide; beam splitters (5) formed on the waveguide layer between the semiconductor laser and the focusing grating coupler, for bisecting each of the reflected beams at a prescribed acute angle; photodetectors (10) for converting the bisected beams into electrical signals; optical isolators (17, 18) formed between the semiconductor laser and the photodetectors.

Abstract: An optical head for reading a signal recorded along spiral or concentric tracks on an optical disc including a semiconductor laser for emitting a linearly polarized light beam, a polarization prism for transmitting the light beam, an objective lens for projecting the light beam upon the optical disc and for collecting a light beam reflected by the optical disc, a critical angle prism for totally reflecting the light beam reflected by the polarization prism and a light detector for receiving the light beam totally reflected by an optical surface of the critical angle prism. The polarization prism and critical angle prism are integrally coupled with each other to form an assembly of prisms which is rotated to adjust an incident angle of the light beam impinging upon the optical surface of critical angle prism substantially at a critical angle of total reflection.

Abstract: An optical system is described for use in processing information on a surface of an erasable record disc. The system decreases erasure time by forming an elongated spot from the generally circular cross section of a collimated laser beam so as to provide increased illumination time to an area recorded on the disc. The system includes a source of collimated light having a generally circular cross section, a cylindrical lens for focusing one aspect of the collimated light at a finite distance f, and a beam expander having the principal plane of its input lens at the distance f from the cylindrical lens, where the light forms a beam waist. An objective lens focuses the expanded elongated beam to a diffraction spot on the surface of the record disc. A linear actuator, such as a voice coil, responds to a control signal to position the cylindrical lens in the path of the collimated light beam for the erasing process, or out of the light path for the recording process.

Abstract: This invention relates to the field of radiant energy information storage devices and provides for a low reading level, an intermediate level and a high writing level of power from the radiation source so as to lower the overall power requirements of the radiation source and increase availability and accuracy of the verification read directly after or during writing, without causing unwanted damage to the information recording media. A circuit is described to accomplish this. The circuit basically employs two power sources, one for reading power, one for writing power and an intermediate ("Pedestal") circuit to employ a portion of the writing power source's power to provide the step-up in power to the intermediate level.

Abstract: Disclosed is a new magnetic storage medium including a layer of amorphous material typically GdDyFe whose Curie recording point (e.g., 120.degree. C.) is lower than its crystallization point (e.g., 350.degree. C.) to enable crystallization to cause variations in its optical properties such as transmittance or reflectivity for thermomagnetic writing. Reversible recordings are set up on the amorphous material layer by a thermomagnetic writing technique, for example Curie point writing, while unchangeable or permanent recordings are set up on the amorphous material layer through laser-activated crystallization of the amorphous material layer.

Abstract: A system and a method for applying a sound track to cinematic film by means of a modulated laser beam.

Abstract: An optical system includes a semiconductor laser for emitting a laser beam, a coupling lens for converting the laser beam a parallel beam, an optical beam shaping system for increasing the diameter of the parallel beam in a direction in which the semiconductor laser has a smaller far field pattern, and an objective lens for focusing a beam shaped by the optical beam shaping system into a spot. To make the spot substantially circular in shape and increase the light utilization efficiency, the magnification of the optical beam shaping system in a direction parallel to the junction plane of the semiconductor laser is selected to fall in a certain range.

Abstract: An optical storage system is disclosed having improved spatial combining and separating apparatus along with improved focus detection and control apparatus. The spatial combining and separating apparatus functions to precisely combine a writing laser beam with a reading beam prior to focusing on an optical medium, and also functions to separate the reading and writing beams after reflection from the medium in a manner so as to prevent interference therebetween. The improved focus detecting and control apparatus employs a portion of the reflected reading beam to derive two beams which are applied to first and second photosensitive elements, respectively. Focus detection is achieved based on determining the difference between the diameters of the beams incident on the photosensitive elements which are located so that the diameters of the beams applied thereto are indicative of the quality of focusing of the beam on the surface.