Abstract: A laser in a magneto optical recorder supplies a laser light beam to be used in processing signals to and from a magneto optical record member. The laser beam is split into two portions. A first portion is the data beam which is directed to impinge upon a magnetooptic storage member. A second portion is so-called wasted light which is directed away from the storage member. The wasted light is intercepted by a mirror and reflected into a beam splitter to phase-coherently combine with light reflected from the storage member for improving signal-to-noise ratio of the reflected storage member light beam. This action improves signal-to-noise ratio and enhances servo operation in the focusing position control of the optical head with respect to an optical storage medium.

Abstract: A record medium, such as a magnetic tape, optical disk, magnetic disk, and the like stores data signals and error redundancy signals. Resynchronization signals are interleaved between the recorded signals such that the error redundancy signals are usable to correct signals recorded between such interposed resynchronization signals wherein no error redundancy signals are recorded. Error pointing redundancy signals are recorded between all of the resynchronization signals for pointing to signals in error for enhancing the error correction. Such error pointing signals can be cyclic redundancy check (CRC) signals. Controls for taking advantage of the above-described arrangement are also described. Reframing and clock synchronization controls are also disclosed.

Abstract: A magnetooptic player reads magnetooptically recorded signals on a disk by using a differential detector. Intermediate areas on a storage member used to store the magnetooptically record signals are sector marks and ID fields formed by undulations in the surface of the disk. Such sector marks and ID fields are read by detecting the intensity modulation in a reading light beam; for detecting such embossed marks and D-ROM disks, one-half of the differential detector is disabled for facilitating such detection in a differentially arranged detector.

Abstract: A data detection circuit employing either amplitude or transition location techniques to adjust a detection threshold for following shifts in baseline of the signal being detected. In the amplitude version, the midway amplitude value between a detected succession of positive and negative peaks adjusts the detection threshold such that threshold adjustment occurs in one detection period and is used in the immediately-following detection period. In the transition-position detection, the relative location in time of successive transitions, represented by samples of the transition of a read signal, are integrated and averaged for providing detection which tracks baseline shifts. In all cases, shifting of detection threshold is always immediately adjacent the usage of a detection threshold which continually follows a shifting DC baseline of the input signal.

Abstract: An optical disk recorder, or other apparatus, use a rotary actuator for supporting a work tool, such as an objective lens which is pivotable or rotatable without a pivot pin. Rotation causing or tracking coils on the rotary actuator are disposed adjacent to permanent magnets to selectively effect rotation of the rotary actuator about the pivot pin. A bias electrical current is supplied to these coils to generate magnetic fields which are in opposite rotational senses; such fields force the rotary actuator against the pin in such a manner that the point of contact between the rotary actuator and the pin follows the rotation of the actuator about the pin.

Abstract: A position servo system has a position loop and a velocity loop. The position loop controls the stop-lock condition and provides for movement control within a range about the stop-lock position. The velocity circuit is employed for movements outside of the range of the position servo circuit. When the velocity servo's loop is being used, a compare circuit compares the servo drive signal from the velocity circuit with a signal generated by the position servo loop which is tracking the velocity servo loop. When the compare circuit finds that the servo drive signals have equal amplitudes, then the velocity servo loop is disconnected from an actuator with the position servo loop then connected to the activation for completing the movement to a desired or target stop-lock position. The above-indicated servo system controls a topping or fine actuator carried on a carriage moved by a coarse actuator.

Abstract: Information-bearing signals are stored using high-temperature superconducting materials. Type II semiconductors, such as materials in the perovskite class, are used for recording. A vortex of electrical current is induced in a layer of the super-conductive materials which causing a magnetic field extending from the axis of the vortex. One or more vortices can be used to record one bit of information. The induced magnetic field is sensed for reading the stored information.

Abstract: Recording operations for an optical disk recorder are calibrated by adjusting recording power level (light intensity) such that a permissible crosstalk can be detected in adjacent erased tracks. Following the power level calibration, pulse duration or width is calibrated for a predetermined symmetry of recorded pulses along the calibration track. Various sequences and procedures are described. Calibration occurs at a plurality of radially spaced-apart tracks.

Abstract: In a "piggy-back" head support system, a fine actuator which carries the head (lens or transducer) is controlled to move the head. A coarse actuator or headarm movably supports the fine actuator and is mounted on a frame for movement radially of the signal storage disk. The head scans tracks on the disk. A servo actuates the coarse actuator to follow the movements of the fine actuator. In a seek, the fine coarse actuator may not be able to follow the fine actuator resulting in the fine actuator hitting a safety stop. When this happens, seek errors occur. According to the invention, the relative displacement of the fine actuator with respect to the coarse actuator is limited during predetermined portions of a seek operation, i.e., the high speed accelerate and decelerate portions.

Abstract: A magnetooptic disk has circumferentially-spaced-apart, radially-aligned embossed sector areas which indicate data storage tracks. The sector areas include embossed signals which indicate track-following information, and in a second area which trails the track-following information, track-seeking information is carried by the embossed signals. A magnetooptic coating covers the entire disk including the embossed sector areas. Readback clock synchronization signals are recorded over the track-seeking area to enable synchronizing a readback phase-locked loop such that more of the areas between sector areas can be used for recording data signals. During track seeking, the track seek controlling embossed signals are read using intensity demodulation, while in track following, during a readback, the clock signals recorded over the embossing are read for synchronizing the readback circuits. During recording, the synchronization signals are recorded over the embossed area dedicated to track seeking.

Abstract: A rotary objective lens support having a predetermined tolerance to parasitic vibrations enables rapid focussing and track following and track changing motions. The rotary support is a beam having a central aperture for slidably and rotatably receiving a pivot pin. A pair of apertures on laterally opposite sides of the central aperture receive motion actuating U-shaped magnets. A lens is mounted on one end portion of the beam and a position indicator is mounted on the opposite end portion of the member. A base, which includes the pivot pin and U-shaped magnets, has a position-sensing means for sensing the rotational position of the member. A pair of outside walls extend past and partially form the magnet receiving apertures. The walls are shaped to reduce effects of parasitic vibrations. In one embodiment, the lens and position indicator are mounted on axially offset end portions; the walls extend between the end portions such that an oblique surface is formed on each of the walls.

Abstract: In a disk recorder, unintended radial portions of a transducer or head, herein termed "skating", is rapidly controlled and stopped before the transducer or head can hit a crash stop. Even when a braking operation is effected in the wrong direction, the skating compensation reverses the braking operation for rapidly stopping the radial motion of a transducer. A pair of clamp circuits are electrically interposed between the servo actuator drive signal generation and a run-out compensation circuit such that the clamping operation does not alter the run-out compensation. The sequences of machine states for effecting the state accommodation are described.

Abstract: A holographic storage system receives light having its linear polarization rotated from a reference linear polarization for carrying given information. The modulated light is stored as two distinct images in a photorefractive crystal, the images carrying the same information but being complementary projections of linear polarization rotations from the reference linear polarization in a given rotational sense. The images are stored in the same volume portion of the crystal. Upon readout, the two images are converted into modulated electrical signals. To reproduce the information, one of the modulated electrical signals is divided into the other modulated electrical signal. A function of square root of arc tangent is introduced into the signal processing at the output portion of the system.

Abstract: A track-seeking apparatus of a disk recorder employs a track-crossing sensor to produce track-crossing signals. An oscillator is slaved to the sensor for supplying substitute track-crossing pulses in the absence of the sensor providing such pulses or when the radial velocity exceeds a threshold velocity. A velocity profile means alters the oscillator frequency so that the oscillator produces track-crossing pulses in accordance with the profile.

Abstract: A magnetooptic recorder player provides for residual data checking and media defect checking. Media defect checking is effected by comparing the reflected light intensity of a modulated optical beam with the input data characteristics. A difference between the input data and the detected light intensities represents asperities in the record media. Residual data is checked by selectively gating MO detected signals during recording, which are intermediate the high intensity light beam pulses used for recording signals. Both the detected residual data and detected media asperities are counted for each addressable record storage area on the medium.

Abstract: A focus acquire circuit for use in optical systems, such as optical data recorders and players, uses up to three parameters signals to indicate an in-focus condition. The zero crossing of a focus error signal is combined with a signal indicating that the focus error signal has approached a peak value and with a signal indicating a change in laser drive signal amplitude to indicate an in-focus condition. Various circuit details are illustrated showing how the three parameters cna be combined together for indicating an in-focus condition.

Abstract: Uncompressed data is represented in a constrained code for transmission through a channel which may include record media. A d,k code having a code rate of m/n is employed. "d" represents the minimum number of successive zeros in the channel code while k represents the maximum number of zeros in the channel code. "n" is an integer representing the number of code bits in a channel group. The encoding and decoding follows a sliding block coding and decoding algorithm. In the channel coding, the number of successive ones is limited to being not less than two, in some coding it can be a value of d-1. The modification of the d,k code results in decreasing error propagation while increasing the recorded information density. This increase is achieved by increasing the channel code dictionary.

Abstract: The disclosure relates to sequential performance of a cached data storage subsystem with a minimal control signal processing. Sequential access is first detected by monitoring and examining the quantity of data accessed per unit of data storage (track) across a set of contiguously addressable tracks. Since the occupancy of the data in the cache is usually time limited, this examination provides an indication of the rate of sequential processing for a data set, i.e., a data set is being processed usually in contiguously addressable data storage units of a data storage system. Based upon the examination of a group of the tracks in a cache, the amount of data to be promoted to the cache from a backing store in anticipation of future host processor references is optimized. A promotion factor is calculated by combining the access extents monitored in the individual data storage areas and is expressed in a number of tracks units to be promoted.

Abstract: Mounting volumes (tape reels or disks) to data processing system is managed for reducing the number of mounting operations. A data accumulation algorithm generates mounting criteria.

Abstract: Data is accessed by record identification in a peripheral sub-system having cache and back store to transfer the most recently updated version of one or more records stored in the subsystem where one version of a record may be in a back store and a modified version of the record may be in a cache storage, by a method and apparatus including table lookup means for indicating for each record of each track of each device in said back store whether record data stored in cache is modified with respect to a version of the same record stored in back store; and means responsive to the indicating means for transferring the modified or backing store version of a record in accordance with predetermined criteria.