Abstract: A magneto-optical player employs a differential readback circuit. The differential signal output of the readback circuit is low pass filtered. The filtered signal is converted to a single-ended signal and applied to a field effect transistor (FET). The FET is connected between one of the differential inputs of the readback circuit and a reference potential. The single-ended signal controls the FET to variably attenuate one side of the differential signal for reducing noise induced into the readback signal from diverse sources.

Abstract: A record disk player removably receives for rotation a record disk having an index mark as the sole circumferential position indicator. A spindle in the player has a tachometer with marks angularly displaced a distance equal to the disk storing a predetermined number of bytes on the respective record tracks. A byte counter counts byte periods and is reset by each of the tachometer marks for indicating offset of the marks from the index signal. A register stores the offset as determined by the count in the segment counter at index time. A segment counter counts tachometer pulses for indicating which of the segments are currently being scanned on the record disk. The segment count when coupled with an offset indication provides true rotational position to a byte granularity. The index pulse resets the tachometer counter to zero. The tachometer counter has a modulus equal to the number of groups of bytes (segments) in each of the record tracks.

Abstract: An optical disk recorder includes a position servo control loop for causing a beam of radiation to faithfully follow a track on the disk, jump from a current track to an adjacent track or to a small number of tracks away from the current track. Operation of the position servo loop is altered by selectively reversing the phase of a differentiated position error signal and integrating the differentiated position error signal for comparison with a sawtooth signal for moving the beam of radiation from the current track to an immediately adjacent track under continuous position servo control. Upon reaching the adjacent track, the sawtooth signal returns to a reference potential for initiating track following. The servo error between the integrated differentiated position error signal and the sawtooth signal is sufficiently small such that relaxation of the sawtooth signal does not cause any significant perturbations in the positioning servo loop operation.

Abstract: An updatable and expandable directory structure and resultant access procedures emulating a write-once or indelible record medium to a rewriteable record medium as to accessing characteristics. The directory is indexed; one directory header for a first set of files indexes another set of files. Sector clusters or data extents are managed such that random recording from any file proceeds independently of write-once characteristics. The directory is stored on the medium as data is recorded. Each directory entry contains an archival history of recording of a related data file in the medium. Both logical and physical addressing is employable.

Abstract: A modulated light beam, as received from a magnetooptic record medium, carries information in the form of linear polarization rotations having P and S components, herein also referred to as light-phase modulated light. A phase-to-intensity converter optically rotates one of the component linear polarization to be aligned with the linear polarization of the other component. The rotated component and the other component are then combined along a common optical path for interferometrically generating a single intensity-modulated light beam. The intensity-modulated light beam is then detected with an output electrical signal indicative of the information carried by the P and S components. In one form, the phase-to-intensity converter includes generating two intensity-modulated light beams using interferometric techniques, separately detecting the intensity modulator light beams and combining same electrically in a differential amplifier.

Abstract: A data recorder, preferably of the magnetooptic type, employs a rotating record storage disk. The record storage disk has a track starting primary data storing sector circumferentially adjacent to the track starting sector or a small plurality of alternate data storing sectors which are not addressable directly by mechanisms outside of the recorder as are the primary recording sectors. Whenever a one of the primary sectors in a given track is found to be defective, then one of the alternate sectors in that same track receives data from a one of the primary storing records of sectors in the same track. A small number of alternate sectors are selected to extend circumferentially for creating an elapsed scan time over the element of sectors not less than the elapsed time required for the recorder to switch from scanning one track to scanning an adjacent one of the tracks.

Abstract: A data recorder employs a disk record having a spiral track with either magnetically or optically sensible indicia. A normal mode of operation is to repeatedly scan one turn or circumvolution of the spiral track for emulating a circularly closed track. The recorder responds to received commands from a utilization device to tailor the disk access and recovery operations to the received command based upon command parameters and current status of the disk record. Electrical circuit and programming arrangements for effecting the controls are disclosed.

Abstract: The holographic diffraction efficiencies of photorefractive or electro-optic crystals, such as bismuth silicon oxide (BSO), increase while experiencing high AC voltages. The diffraction efficiency also increases with frequency of the AC voltages up to a saturation frequency. These enhancements are attributed to the response times of the crystal and the superposition of internal electric fields. The enhanced diffraction efficiency assists in retentively recording information bearing holograms in electro-optic crystalline media.

Abstract: A focus and tracking support includes a pair of bender beams extending parallel to a track to be scanned. The bender beams are cantilevered from a mounting block carried by a head carriage. Disposed intermediate and pivotally secured to the distal ends of the bender beams is a lens holder having two pairs of oppositely-extending, pivotally-secured support arms connected to the distal ends. The arrangement is such that when the bender beams are moved in the same direction tracking functions are performed while when the bender beams are moved in opposing directions, focussing functions are performed. The arms and lens holder are formed from a plastic unitary member. When the bender beams are piezo-electric beams, electrical signals for focus and tracking controls are superposed for effecting simultaneous focus and tracking functions.

Abstract: In a magnetic recorder, magnetooptic, for example, the erasure dircetion for successive recording areas (sectors) are determined by the direction of magnetization of prior recording. A mark is placed in each sector for identifying its erasure direction.

Abstract: A photodetection system includes first and second photodetectors, each having an anode and a cathode. The anode of one of the photodetectors is ohmically connected to the cathode of the other photodetectors. The photodetectors are suitably electrically biased and disposed for receiving one or two light beams. Output circuit means are electrically connected to the anode and cathode junction between the two photodiodes for providing an output electrical signal having low or no common mode noise. A preferred embodiment of the invention using a single semiconductor chip for the entire circuit arrangement is also illustrated.

Abstract: Initialization time of a peripheral storage subsystem is reduced. Each subsystem includes a cache store plus a back store having a plurality of DASD storage devides. Storage locations in the cache store are initially allocated for an index table for other subsystem control structures, track buffers, and a limited number of data storing record slots. Limiting the allocation of record slots reduces initialization time. The number of record slots initially allocated is determined by a maximum allowable system initialization time, a total number of subsystem devices to be initialized and the time required to initialize each record slot.

Abstract: A storage-management program, executable in one host or simultaneously in a plurality of hosts, manages concurrently executing migration, recall, and recycle (such as defragmentation) tasks. Accesses to data storage volumes (tape, disks, etc.) are managed in accordance with predetermined contention resolution procedures and priorities. Certain tasks are non-interruptible.

Abstract: An optical disk recorder focus-error system includes a so-called "knife-edge" focus detector. The dynamic range of the detector is enlarged by placing an apertured mask intermediate the knife edge and the source of the light beam being focused. The knife-edge mask and the apertured mask can be deposited opaque films on a lens.

Abstract: Shade or tint intensities in holograms are calibrated by an array of calibration pixels in each hologram. The preferred array consists of crossed lines of the calibration pixels in the hologram disposed to cover all critical portions of the hologram. An optical processing apparatus employing a hologram having an array of calibration pixels is disclosed.

Abstract: A multi-layer assembly includes a support block with a plurality of circular cylinder bores, each receiving optical elements. Juxtaposed along the length of each of the bores in a circumferentially spaced-apart relation is a pair of positioning rods having surfaces extending into the bore. The surfaces are precisely aligned with a desired optical axis to be established by the optical element. A plunger pushes the optical element against the rods to establish the optical axis. Lasers and adjustment apparatus are included in the assembly.

Abstract: A storage-management program, executable in one host or simultaneously in a plurality of hosts, manages concurrently executing migration, recall, and recycle (such as defragmentation) tasks. Accesses to data storage volumes (tape, disks, etc.) are managed in accordance with predetermined contention resolution procedures and priorities. Certain tasks are non-interruptible.

Abstract: Data supplied to a data storage system by a host processor has one of two use status. A first use status is that the supplied data is to be retentively stored in the data storage system. A second use status is that the supplied data is exempted from the retentive storage requirement. An example of exempted use status is that data only temporarily stored in the data storage system, i.e. is transitory. A second example is data that is being manipulated prior to retentive storage, data that is temporarily volatile. Termination of the exempted use status results in either discard or a retentive storage of the exempted use data. Data integrity controls for the exempted use status data are described. The invention is described for a data storage hierarchy environment having a volatile cache and a magnetic recorder as a backing store. The exempted use data need be stored only in or primarily in the cache while retentive data is primarily stored in the retentive store and selectively in the cache.

Abstract: The disclosure relates to demotion of data to a backing store (disk storage apparatus--DASD) from a random access cache in a peripheral data storage system. A cache replacement control list, such as a least recently used (LRU) list is scanned in a soon-to-be replaced first portion (portion closest to LRU entry) to identify first data to be demoted. Then the control list is scanned in first and second portions to identify further data to be demoted with the first data as a single group of data. In DASD, such data is all storable in the same cylinder of the DASD.

Abstract: A holographic unit includes a planar array of hologram/sections disposed along a central axis. A pair of parabolic arrays of planar mirrors are symmetrically disposed on opposite sides of the hologram array such that all planar mirrors face respective ones of the hologram/sections. A hologram emitter transmits hologram-inducing light to mirrors in a first one of the parabolic arrays, and a hologram receptor receives hologram/light emitted from the hologram array via mirrors in a second one of the parabolic arrays. The emitter and receiver are respectively disposed at the focal points of the parabolic arrays. The emitter and receiver have planar arrays of photoelements oriented at identical angles with respect to the hologram array and respectively facing the mirrors. The planar array of holograms may be used for storing or processing information-bearing signals.