Abstract: In a focus correction servo loop which maintains optical focus on an optical disk by movement of an objective lens, a focus error signal generating system which utilizes a pair of photodetectors in a differential channel, the first detector being located a predetermined distance within the focal length of the detector lens associated with that detector and the second detector being located beyond the focal length of the detector lens associated with that detector by the same predetermined distance. When the disk is at the focal point of the objective lens, equal light will fall on both detectors. When the disk position deviates from the focal point of the objective lens, more light will fall on one detector than on the other detector. The dc value of the difference between the detector signals is the focus error signal utilized by the servo loop.
Abstract: A system for providing a read signal from a magneto-optic medium wherein a non-rotated leaky beam splitter is utilized to provide both s and p components of the light reflected from the medium to a differential detector arrangement. The beam splitter, which may be of conventional construction and which has the reflected beam striking its medium-facing face at normal incidence, is operated in a leaky mode by utilizing it with a read beam having a wavelength differing from the wavelength for which the beam splitter was designed. One face of the beam splitter can be cut at a small angle off normal to prevent any p-polarized light from entering the differential detector arrangement directly from the light source.
Abstract: Additional control in a differentially-encoded printer utilizing an electro-optic element is achieved by normalizing or equalizing the strength of the fringe fields. Such normalization is provided by applying analog voltages to the adjacent electrodes in addition to the encoded data sample voltages.
Abstract: A temporal pixel clock synchronization system with jitter correction for an optical scanning system having a continuously running pixel clock source, circuitry for generating timing error signals having an amplitude representing any phase error between start of scan and start of pixel count pulses and any phase error between end of scan and end of pixel count pulses and circuitry, including a switched filter circuit with two storage elements for each facet of the polygon of the system, for generating a frequency correction signal for the pixel clock source.
Abstract: A small amplitude, low frequency, signal is added to the focus servo signal controlling the position of the objective lens of an optical disc storage system after focus acquisition has been achieved, so as to produce a slight defocusing effect of the light spot on the disc. The resulting variations in the read back signal is utilized by a synchronous detection circuit scheme to extract magnitude and polarity information of the focus offset present. That information is fed back to the focus servo signal to null out the focus offset, thereby assuring continual accurate focusing of the laser beam even under conditions of changes in the mechanical alignment of the optics of the storage system and/or the d.c. stability of the electronics of the storage system.
Abstract: A magneto-optic storage media which utilizes two layers or films of magnetic material, with the magneto-optic hysteresis loop of one of the films being of a sense opposite to the sense of the magneto-optic hysteresis loop of the other film. The media permits the Farraday effect polarization rotations produced by one of the magnetic films to be in phase with Kerr effect polarization rotations produced by the other of the magnetic films, such that additive mode conversion is provided from different portions of the media whereby the detected signal has an increased signal-to-noise ratio.
Abstract: The synchro-servo zones of the data blocks of an optical disc track are provided with information which will permit the generation of clock synchronization pulses and tracking pulses, with those latter pulses being used with peak detector/sample and hold circuitry of novel design to generate a substantially noise free tracking information servo feedback signal. Specifically, a pair of pulses having respective amplitudes proportional to the displacement of the read/write beam from the center of the track are generated, with the peak amplitudes of those pulses being stored, and then compared to provide, after carrier filtering, a tracking information servo feedback signal which would have an amplitude proportional to the displacement of the read/write beam from the center of the track and a sign or sense indicative of the direction of the displacement.
Abstract: A mount for a mirror of a laser resonator which will permit angular adjustment of the mirror with respect to two normal axes defining a plane at right angles to the axis of the laser resonator, while minimizing undesired mirror movement due to vibration and temperature variations. The mount, in the form of a flexure plate, is of unitary construction, comprised generally of a planar base plate member, two planar adjustment members, and connecting sections which couple the three planar members together. A first pair of the connecting sections rigidly link first and second oppositely disposed corner portions of the first adjustment member to the base plate member, and a second pair of the connecting sections rigidly link other oppositely disposed corner portions of the first adjustment member, generally disposed 90.degree. relative to the first and second corner portions, to the second adjustment member.
Abstract: An optical disk system having direct read after write capabilities in which the write beam and the read beam are generated by a pair of integrated injection diode lasers. The integration can be achieved by mounting two separate injection diode lasers side by side in a common package or providing two side by side injection diode lasers formed on a common seminconductor substrate. The two lasers would be located in the same focal plane relative to a recording material, with one of the lasers pulse modulated to provide a data modulated write beam and the other laser driven in the continuous wave (CW) regime to provide a read beam of constant intensity. The plane containing the focused beams would be oriented relative to the recording material so that the focused beams impinge upon adacent portions of one data track of the recording material. Since the pair of lasers are closely spaced (1-1000 microns) a common optical path or train is used for both the write beam and the read beam.
Abstract: A multi-channel laser ROS scanner for simultaneously scanning laser beam components across multiple lines of a photosensitive surface including apparatus for determining deviations in the position of the surface from a desired position due to undesired photosensitive surface velocity variations whereby an error correction signal can be generated, and a TIR modulator having a plurality of interdigitated, addressable drive electrodes. The total number of drive electrodes N.sub.t of the TIR modulator is greater than the collective number of drive electrodes N.sub.s needed to provide the desired pixel resolution for all of the simultaneously scanned lines. When the photosensitive surface is maintained at a desired velocity, such velocity being determined in a conventional manner by system parameters, the surface is correctly positioned and N.sub.
Abstract: An optical disc drive system in which the empty sleeve component of an optical disc cartridge is utilized to lock the optical disc in its operational position while occupying a storage location within the drive system. The locking/storage feature is achieved by providing adjacent to the conventional disc insertion opening in the drive frame an additional opening for receipt of the empty sleeve component and by providing guides within the drive for positioning the empty sleeve over the optical disc. The empty sleeve cooperates with a spring loaded frame/disc lowering mechanism which lowers the optical disc to the drive spindle where it is held by a magnetic force generated by a magnetized portion of the spindle. The sleeve also cooperates with a frame/sleeve latching mechanism to facilitate withdrawal of a frame supported optical disc from the sleeve and reinsertion of the frame supported optical disc back into the sleeve.
Abstract: A linear array of injection diode lasers formed on a common substrate is utilized to provide modulated scanning beams for a photosensitive medium. A scanning device, preferably a multifaceted mirror polygon driven at a constant speed, is placed in the optical path between the array and the photosensitive medium, as is a focusing lens. To provide additive exposure intensity the plane of the emitting surface of the array is oriented relative to the scanning device so that all of the beams emitted by the array are caused to illuminate the same scan line of the photosensitive medium whereby each beam scans the same data spots on the same line of the photosensitive medium such that additive exposure of those spots is achieved.
Abstract: Each laser of a semiconductor laser array of an optical system has its own lens mounted adjacent to it in the space between the laser array and the objective lens of the system. The purpose of the lenses is to change the angle of divergence of the light beams leaving the emitting surface of the laser array so that the light beams can be collected efficiently by the objective lens, thereby providing significant beam power at the light sensitive medium (optical disk, photoconductor, etc.) of the optical system. The focusing power of each lens is chosen to form virtual images behind the emitting surface with spacings approximately corresponding to the spacings of the light beams emitted by the laser array, but with the emitter image size substantially magnified.
Abstract: A flexible force transmitting member biasing arrangement consisting of a snubbing device and a spring. The arrangement functions to permit a flexible force transmitting member attached to it to undergo a significant amount of movement (due to the force exerted by the spring) at very slow rates but prevents the flexible force transmitting member from undergoing substantial movement at high rates attendant with high frequencies of motion. A preferred form of the snubbing device is a dashpot.
Abstract: An optical disk recorder in which the optical disk, the drive spindle and the disk drive motor are moved or pivoted in an arcuate path relative to stationary laser optics. When moved in such an arcuate path, the optical disk, spindle and drive motor have a lessened movement of inertia (compared to linear movement thereof) which permits relatively fast accessing of an optical disk without a large drive motor. The accessing system can be naturally statically balanced by placing the spindle and the drive motor or opposite sides of the pivot point.
Abstract: A layer of an ion exchanged glass is utilized as the master for video disc production. Due to the ion exchange, such glass possesses stored energy in the form of compressive stress. When localized portions of the layer of ion exchanged glass are heated sufficiently, those portions of the glass soften and release the compressive stress energy in the form of localized surface bumps. The presence or absence of surface bumps and/or their height can convey the video information in analog or binary form. Once the ion exchanged master is formed, the master is used in a conventional manner to produce mirror image copies on a suitable, conventional substrate, generally a plastic. The copies are generally formed by a pressing or stamping technique, or by an injection molding technique. The relief surface of the copies can be coated with a conventional light reflective layer to aid in optical read-out of the video information stored by the relief surface.
Abstract: The number of data tracks or positions that a transducer can access or track is increased, beyond that conventionally permitted by the transducer conductor spacing, by first providing a plurality of signals corresponding in number to the factor by which the tracking capacity of the transducer is to be increased, with all signals having a common frequency equal to that of the drive signals applied to the transducer stator windings and with each signal being phase delayed relative to the other signals by one or more clock increments, then accessing the signal having a phase corresponding to the data track to be tracked, providing from that accessed signal a plurality of additional relatively phase delayed signals, and applying each of the later phase delayed signals to one of a plurality of phase detectors each of which also receives an input corresponding to the squared transducer rotor signal whereby the phase detectors provide at their output width modulated signals having a low frequency component correspon
Abstract: A disc drive including a rotatable interlock mechanism which, in the absence of disc insertion, maintains separation between adjacent read/write heads regardless of the position of the door latch of the disc drive. With no disc inserted and with the door latch closed, the interlock mechanism is held by a soft spring in a support position which limits movement of the moveable head support arm toward the fixed head such that contact between the heads cannot occur. Upon opening of the door latch, to facilitate disc insertion, the moveable head is lifted to a position further from the fixed head due to the disc clamping assembly contacting the protruding finger of the moveable head support arm.
Abstract: To generate a signal having at all times an amplitude directly proportional to the velocity of relatively moving members, a plurality of phase displaced position indicative signals are first generated. A pair of the position signals that are phase displaced by 90.degree. are then differentiated to provide velocity signals. Each velocity signal is applied in both its regular form and its inverted form to an analog multiplexer which receives the other position signals as control signals. The composite output of the multiplexer, after filtering to remove high frequency glitches due to sampling, is a signal having an amplitude at all times directly proportional to velocity.
Abstract: Settling problems of a closed loop servo system are substantially eliminated by switching the servo system into position mode operation only when there is zero position error and zero velocity error. The fast and clean settling is accomplished by digitizing the instantaneous amplitude of the position signal when the difference count has decremented to zero and using that digital value as the address of a square root look up table which provides for each instantaneous amplitude of the position signal a digital signal indicative of the instantaneous velocity required to effect rapid settling at the rest position. The digitized velocity signal is converted to an analog signal by a digital to analog converter for energization of the drive motor.