Abstract: Apparatus for selectively reversing a magnetic bias field (e.g., to switch between recording and erasing modes in a magnetooptic recording system) includes a rod-shaped permanent magnet having its magnetic poles oriented along the cross-sectional dimension thereof. The rod is mounted for axial rotation within a concentrically arranged tube of electrically conductive material, and means are provided for biasing the rotational position of the magnet toward either of two nominal positions, 1/2.degree. apart. Upon being subjected to a torque, the magnet rotates toward either of its nominal positions, and oscillatory movement about such nominal positions is damped by eddy-current-produced magnetic forces in the conductive tube.

Abstract: In an optical recording system, automatic gain control circuitry is provided to maintain the gain of the focus (or tracking) servo system substantially constant and independent of intensity variations in the light beam used to detect focus (or tracking) error. According to a preferred embodiment, such circuitry comprises two cascaded stages, i.e., a switchable gain first stage for effecting coarse gain changes on command (e.g. when switching between write and read modes), and a non-linear feedback second stage for adjusting the coarsely trimmed output of the first stage to achieve overall constant focus (or tracking) error gain.

Abstract: Apparatus for sensing the instantaneous tracking position of a lens used in an optical read/write head for optically reading and/or writing information on an optical recording element (e.g. an optical disk). Such apparatus includes a variable inductance transducer which is positioned in close proximity to an electrically conductive, movably mounted lens support. As the lens is moved in a direction perpendicular to its optical axis, the lens support moves relative to the transducer, thereby varying the transducer's inductance. Circuit means responsive to the instantaneous transducer inductance provides a signal representative of the instantaneous lens position. Such signal is used to close a position feedback loop which maintains a fixed position of the lens axis relative to the optical axis of the head during sudden movements of the head (e.g. as occurs in during radial access in an optical disk recording system).

Abstract: An analog ASIC (Application Specific Integrated Circuit) circuit has a power control section, a conductivity filter testing section, a light emitting diode (LED) driving section, and a bias section. The LED driving section is responsive to the conductivity filter testing section for indicating when the filter should be replaced. The power control section, conductivity filter testing section, LED driving section, and bias section are all operated in a controlled timed relation by a digital ASIC logic system to minimize power use.

Abstract: The base bandwidth of any optical image that falls upon an imager is customized so that its uppermost spatial frequency is less than half the sampling frequency associated with the imager, thereby creating a power-vacant frequency window in the signal output of the imager. Since the edges of dead and hot pixels correspond with very high spatial frequency components, the very existence of a dead or hot pixel will result in signal power within the aforementioned window of the sampled output of the imager . . . and the extent of such power will be directly dependent on the magnitude of the discrete optical image that falls in the vicinity of the dead or hot pixel. Apparatus according to the invention detects the existence of power at a frequency of one-half the imager sampling frequency (i.e. at the center of the aforenoted power-vacant window); thereafter, such power is transformed into a correction signal for properly timed algebraic addition to the baseband signal output of the imager.

Abstract: A film video player apparatus for sensing a film frame image to produce a video signal comprised of standard video fields, includes means for selectively changing the magnification of the film frame image with respect to the video display (zoom) and for displacing the film frame image horizontally and vertically with respect to the video display (scan). The film video player apparatus is provided with a control system comprising means for coordinating zoom and scan so that the video display is always filled with the film image. The control system further includes means for returning the zoom to normal magnification when a new film frame image is selected for display. The video player apparatus blanks the video signal during film advance, but continues to produce a video signal for display while zooming and scanning.

Abstract: Regarding any given light source in an array thereof, apparatus according to the invention comprises a shift register adapted to store bits corresponding to the ON times for the light source. The output of the shift register is applied to the light source and, when a ONE bit occurs at the shift register output concomitantly with the application to the light source of a pulse from a train thereof, the light source turns ON. The pulses in the train thereof are of binary weighted durations. By making the duty cycle of at least the 2.degree. pulse of the pulse train fairly low, and by employing a secondary pulse train to effect shifting of bits within the register simultaneously with, or before, the occurrence of the binary weighted pulses, the maximum shift frequency within the shift register--as opposed to that which would be required by prior art apparatus that employs a bit weighted clock for shifting within the register--is lessened appreciably.

Abstract: Optical scanning method and apparatus suitable for use with a video player for scanning an information bearing medium to produce a standard television signal is disclosed. The scanning apparatus includes a movable mirror that deflects an optical path to effect a scan. The mirror is angularly displaced, back and forth, between first and second positions at a substantially constant rate in a "back-to-back sawtooth" fashion, such that one scan is made as the mirror is moved from the first position to the second position, and the next scan is made as the mirror is returned from its second position to its first position. The scanning apparatus inverts an image transmitted along the optical path between each successive scan to provide scanning in a "sawtooth" fashion, e.g. scanning an image from top to bottom--quickly retracing to the top of the image--and repeating the scanning process from top to bottom, as is required in the standard television scanning format.

Abstract: A color line sensor for use in color film scanning apparatus is disclosed. The scanning apparatus is of the type employing a line sensor for scanning an image of the film in one direction and having means for continuously displacing the image relative to the sensor, in a direction generally perpendicular to the line scan direction, to effect a raster scan composed of a number of equally spaced lines. The color line sensor includes a plurality of line sensing arrays, spaced apart from each other by a distance corresponding to the spacing between scan lines in the raster. Each line sensing array is sensitized to a particular color of light so that a plurality of color signals are produced by the sensor. Respective color signals from the line sensing arrays are delayed by an amount sufficient to cause all the color signals emerging from the color line sensor at any given instant to represent the same point in the image.

Abstract: In accordance with a presently preferred embodiment of the invention, a servo control loop is disclosed using optical feedback to control the movement of a small, lightweight scanning mirror. The optical feedback is accomplished by reflecting radiation from the scanning mirror and imaging such radiation onto a pair of radiation detectors. An optical element having alternate relatively transparent and opaque regions is disposed in the optical path between the scanning mirror and the detectors to modulate in phase quadrature the intensity of radiation beams received by the detectors. The output signals from the detectors are used to develop a feedback signal to close the servo loop.

Abstract: Frame-rate converting film scanning apparatus capable of scanning film (having frame location indicia) projected at any speed, selected from within a range of speeds, to produce a television signal having a standard field rate is disclosed. The scanning apparatus is of the type employing a solid-state line sensor for scanning a projected image of the film in a direction generally perpendicular to the length of the film and a rotating multifacet mirror to displace the projected image relative to the line sensor for effecting a raster scan of a film frame to produce a standard television signal. The apparatus includes a frame position sensor responsive to a frame-rate converted image of the frame location indicia for producing a frame location signal. The speed of rotation of the mirror is controlled by a phase locked loop servo that employs a standard television vertical synchronization signal as a reference and receives the frame location signal as a feedback signal.

Abstract: In using helical-scan-type apparatus for recording video information in parallel tracks on magnetic tape, the typical slanted arrangement of the tracks results in track-to-track shifting or offset. Tape scanning apparatus adapted for implementing an improved recording technique employs an incremented scanning head speed for scanning one track in a period of time that departs from the period of one video signal sequence (e.g. a video field or frame) by an amount that is specially selected in accordance with the track offset. By so incrementing the scanning head speed the position of a video signal sequence within a track is shifted with respect to the signal sequences in adjacent tracks in a manner that compensates for the offset and provides a closer correlation between the video signal in adjacent tracks, thereby minimizing the effects of cross-talk between tracks.

Abstract: An off-the-air color video recorder employs frequency interleaved chroma and luminance signal information for purposes of bandwidth compression. During playback, a shooting gallery picture defect characterized by motion along horizontal scene edges was noted. Analysis indicated the problem source to be the bleeding of chroma into the playback luminance channel. To avoid this problem, the chroma signal information, prior to recording, has its vertical resolution reduced, e.g., by line-by-line averaging of chroma.