Abstract: An improved phase locked loop utilizing control logic generated by a phase detector to eliminate sensitivity to uncorrelated noise when the loop is in lock.

Abstract: An adjustable optical system for determining aberration in a source beam by comparison of a test beam with a reference beam. The system includes a test source for producing a source beam having a spacial intensity distribution including an aberration component, a wavefront analyzer for processing a fringe signal associated with the aberration component, and an interferometer interposed between the test source and wavefront analyzer. The interferometer includes a beamsplitter for splitting the source beam into a test beam and a reference beam, a mirror disposed in the test beam path, and a micromirror disposed in the reference beam path. The micromirror reflects a central portion of the reference beam toward an imaging device and allows an outer portion of the reference beam to pass thereby.

Abstract: An integrated digital communication system utilizing multilevel vestigial sideband transmission is provided. The communication system receives a multi-level pulse-amplitude modulated digital signal from a limited bandwidth channel. The system includes processing stages which demodulate, sample and filter the incoming signal prior to recovery of the digital data. Other stages recover the timing and lock on to the frequency and phase of the transmitted signal, as well as provide for automatic gain control. An adaptive equalizer, error correction circuitry, and an output interface recover the digital data and provide for transfer to other devices.

Abstract: There is disclosed an apparatus for controlling the strength of a magnetic field, comprising a first controller, a second controller, a digital-to-analog converter, a current driver, and a bias coil. The first controller determines the position of the focal point of a lens and passes it to the second controller, which provides a digital signal related to the position. The digital-to-analog converter converts the digital signal to a driver voltage and passes the driver voltage to a current driver, which provides to the bias coil a bias current related to the driver voltage. The bias coil produces a magnetic field having a strength related to the bias current. The second controller accounts for stray magnetic fields in creating the digital signal. The stray magnetic fields may be constant or may vary in strength based on position of the objective lens, circumferential velocity of the storage medium, or longitudinal velocity of the storage medium.

Abstract: A method for detecting transitions in an input signal having a DC component. The method includes the steps of generating a threshold signal from the input signal, comparing the input signal to the threshold signal to thereby generate an output signal, and adjusting the threshold signal in response to the output signal. In one preferred embodiment, the method is employed to retrieve data from an information storage device.

Abstract: An apparatus for moving an optical head from an initial track to a target track on a storage medium and generating a track crossing signal is disclosed. The apparatus comprises a sensor for measuring the reflectivity level from a storage medium, a preamplifier for generating a data signal, a tracking error signal generator responsive to the reflectivity level for deriving a tracking error signal, a track/hold selector to direct the tracking error signal generator to generate a corrected tracking error signal of a constant amplitude for a predetermined period of time based on the data signal, and a track crossing signal generator based on the corrected tracking error signal for deriving a track crossing signal indicating the crossing of an information track by the optical head.

Abstract: An optical beamsplitter comprises a right angle prism having a hypotenuse and two legs wherein the hypotenuse includes an optically selective coating deposited thereon. An optical element is positioned adjacent the hypotenuse such that the hypotenuse and the optical element form a beamsplitting interface. Various optical elements are utilized to achieve the desired spatial and angular relationships between incoming and outgoing light beams. Several embodiments are disclosed wherein the optical element can comprise a flat plate for providing spatial offset, a wedged plate for producing spatial and angular offset, a lens for adding optical power, or a faceted thin plate.

Abstract: An optical beamsplitter comprises a right angle prism having a hypotenuse and two legs wherein the hypotenuse includes an optically selective coating deposited thereon. An optical element is positioned adjacent the hypotenuse such that the hypotenuse and the optical element form a beamsplitting interface. Various optical elements are utilized to achieve the desired spatial and angular relationships between incoming and outgoing light beams. Several embodiments are disclosed wherein the optical element can comprise a flat plate for providing spatial offset, a wedged plate for producing spatial and angular offset, a lens for adding optical power, or a faceted thin plate.

Abstract: An optical beamsplitter comprises a right angle prism having a hypotenuse and two legs wherein the hypotenuse includes an optically selective coating deposited thereon. An optical element is positioned adjacent the hypotenuse such that the hypotenuse and the optical element form a beamsplitting interface. Various optical elements are utilized to achieve the desired spatial and angular relationships between incoming and outgoing light beams. Several embodiments are disclosed wherein the optical element can comprise a flat plate for providing spatial offset, a wedged plate for producing spatial and angular offset, a lens for adding optical power, or a faceted thin plate.

Abstract: A high speed analog-to-digital converter employs a comparator having first and second units cross coupled in a positive feedback loop. The units are alternately connected to an input voltage and a reference voltage, after which positive feedback is introduced established, and a differential output established. The arrangement is fully symmetric, and balanced and rejects common-mode switching noise.

Abstract: An apparatus is disclosed for processing video information using a first and a second prediction filter circuit which are substantially identical, and a control signal to process video information encoded in multiple standards. A filter circuit, such as may be used in such an apparatus, for use in video decompression comprises a prediction filter formatter, a first one-dimensional prediction filter, a dimension buffer, and a second one-dimensional prediction filter. A prediction filter, such as may be used in such a filter circuit, may comprise six registers, two multiplexers, and two summing circuits. A first register is connected to a first summing circuit. A second register is connected to a first multiplexer, which is connected to the first summing circuit. The first summing circuit is connected to a third register. A fourth register is connected to a second multiplexer, which is connected to a fifth register.

Abstract: The invention discloses a method and an apparatus for implementing an L phase clock in conjuction with L counters, where L is an integer, to count at a frequency scalable by L.

Abstract: A multi-standard video decompression apparatus has a plurality of stages interconnected by a two-wire interface arranged as a pipeline processing machine. Control tokens and DATA Tokens pass over the single two-wire interface for carrying both control and data in token format. A token decode circuit is positioned in certain of the stages for recognizing certain of the tokens as control tokens pertinent to that stage and for passing unrecognized control tokens along the pipeline. Reconfiguration processing circuits are positioned in selected stages and are responsive to a recognized control token for reconfiguring such stage to handle an identified DATA Token. A wide variety of unique supporting subsystem circuitry and processing techniques are disclosed for implementing the system.

Abstract: An IDCT, or Inverse Discrete Cosine Transform, method decimates a 2-D IDCT into two 1-D IDCT operations and then operates separately on the even and odd pixel input words. In a common processing step, selected input values are passed directly to output adders and subtractors, while others are multiplied by constant, scaled cosine values. In a pre-common processing step, the lowest-order odd input word is pre-multiplied by .sqroot.2, and the odd input words are summed pairwise before processing in a common processing step. In a post-common processing step, intermediate values corresponding to the processed odd input words are multiplied by predetermined coefficients to form odd resultant values. After calculation of the even and odd resultant values, the high-order and low-order outputs are formed by simple subtraction/addition, respectively, of the odd resultant values from/with the even resultant values. The input values are preferably scaled upward by a factor of .sqroot.2.

Abstract: An IDCT, or Inverse Discrete Cosine Transform, method decimates a 2-D IDCT into two 1-D IDCT operations and then operates separately on the even and odd pixel input words. In a common processing step, selected input values are passed directly to output adders and subtractors, while others are multiplied by constant, scaled cosine values. In a pre-common processing step, the lowest-order odd input word is pre-multiplied by .sqroot.2, and the odd input words are summed pairwise before processing in a common processing step. In a post-common processing step, intermediate values corresponding to the processed odd input words are multiplied by predetermined coefficients to form odd resultant values. After calculation of the even and odd resultant values, the high-order and low-order outputs are formed by simple subtraction/addition, respectively, of the odd resultant values from/with the even resultant values. The input values are preferably scaled upward by a factor of .sqroot.2.

Abstract: An IDCT method decimates a 2-D IDCT into two 1-D IDCT operations and then operates separately on the even and odd pixel input words. In a common processing step, selected input values are passed directly to output adders and subtractors, while others are multiplied by constant, scaled cosine values. In a pre-common processing step, the lowest-order odd input word is pre-multiplied by .sqroot. 2, and the odd input words are summed pairwise before processing in a common processing step. In a post-common processing step, intermediate values corresponding to the processed odd input words are multiplied by predetermined coefficients to form odd resultant values. After calculation of the even and odd resultant values, the high-order and low-order outputs are formed by simple subtraction/addition, respectively, of the odd resultant values from/with the even resultant values. The input values are preferably scaled upward by a factor of .sqroot. 2.

Abstract: An apparatus for controlling the spacing between information tracks while recording information on an optical disc that does not have pre-manufactured information tracks. The invention employs a precision reference scale to guide the position of information tracks recorded on an optical disc. The reference scale is a linear strip with spaced optical tick marks. The spacing of the optical tick marks on the reference scale directly correlates to track pitch between information tracks recorded on the optical disc. The invention utilizes a first optical system for reading-from and writing-to an optical disc. A second optical system is used for detecting optical tick marks on the reference scale. The first optical system and the second optical system share common optical components. Optical components in common to both the first and second optical systems include a light source, a diffraction grating, a field lens, and a beam splitter.

Abstract: An optical tape cartridge is disclosed that is suitable for playing by an optical tape player. The tape player provides the cartridge with a voltage supply capable of supplying the optical tape with a relatively high voltage. The tape cartridge includes a sealed cartridge housing and first and second tape reels that are disposed within and freely rotatable in either direction within the housing. The reels act as tape supply and tape take up reels. Also included in the cartridge is an optical tape that has a first surface on an optically recordable side. The tape is wound on and couples the two reels with a tape segment. The tape segment is positioned with the optically recordable side facing outwardly from each of the reels. The tape includes a conductive layer that extends substantially the length of the optical tape. The conductive layer is grounded at least one end. The housing includes a sealed window positioned on a housing surface that is located across a portion of the tape segment.

Abstract: In a data reproducing apparatus, an optical pick-up is radially movable with respect to, and recovers information from, an information storage member. A motor rotates an information storage member. A spindle servo controls the speed of rotation of the motor in response to a timing signal, to provide constant linear velocity between the information storage member and the optical pick-up. A signal processor creates a recovered timing signal from the information recovered by the optical pick-up, and passes the recovered timing signal to a switching circuit. During normal playback, the switching circuit passes the recovered timing signal to the spindle servo as the timing signal. During search, a controller directs an oscillator to output a reference timing signal to the switching circuit. A controller directs the switching circuit to pass the reference timing signal to the spindle servo as the timing signal while the optical pick-up is moving radially with respect to the information storage member.

Abstract: There is disclosed a method for moving an optical head from an initial track to a target track on a storage medium. The total number of tracks to be crossed is determined, and the optical head is moved toward the target track. A reflectivity level of light from the storage medium is measured, and a tracking error signal is derived from the reflectivity level. The tracking error signal has both true and false indicators of track crossings. A data indicator signal is derived from the reflectivity level, having indicator points corresponding to the false indicators of track crossings. A track count number is incremented for each true indicator of a track crossing, and the optical head is stopped when the track count number equals the total number of tracks to be crossed. Another method is disclosed whereby a track count signal is generated from the tracking error signal and the data indicator signal.