Abstract: In a magnetic tape readback system for a multi-track tape player, a phase lock loop is provided for each of the channel circuits used for reading signals from the respective tracks on a multi-track tape. A common frequency determining capacitor is coupled to all of the phase lock loops such that the frequency of operation of the phase lock loops is stabilized. The capacitor has a capacitance usable in the individual phase lock loops for determining a frequency of operation and it is commonly AC connected to all of the phase lock loops. A capacitance AC couples and DC blocks each of the individual phase lock loops to the frequency determining capacitor such that the individual phase lock loops have their own reference DC levels and yet receive AC input from all of the other phase lock loops.

Abstract: A magnetooptic storage member is scanned by a single laser beam. The beam intensity is sufficient to heat a localized area of the storage member to be above the Curie temperature for enabling reversing the remanent magnetization of the localized area. Such localized area is subjected to a magnetic bias field for directing which of the remanent directions shall be assumed in the localized area. The storage member and laser beam are relatively moved such that a front or leading portion of the localized area does not reach the Curie temperature. The light reflected from this leading portion, which moves with the laser beam relative to the storage member, is detected for indicating the initial remanent state of the localized area before any changes are made by the combination of the magnetic bias field and the laser beam.

Abstract: When an optical disk recorder having readback circuits is used with pulse width modulated (PWM) signals a phase error of a clocking system with respect to the phase of a data signal is used to generate an amplitude detection threshold offset for serving of the amplitude detection threshold by the phase error signals tending to increase the probability of faithful detection of data carried by the PWM or other signals.

Abstract: Information bearing signals are recorded in one of a plurality of record formats on one record medium, such as a magnetic tape, magnetic disk, optical disk, and the like. The format selected may be commanded or based upon record lengths, in bytes. When the record length equals or exceeds a predetermined number of bytes, then one record is recorded in each signal block of the record format. When the record length is less than the predetermined number, then a second format is used which inserts several of the records in one of the signal blocks. The signal block and its packets respectively contain indications of formats such that any one of several formats may be used on one record medium and in one signal block having a plurality of variable length packets. Logical indicators, such as format marks, tape marks, and the like, may separate formats used on the storage medium.

Abstract: An optical disk recorder has a laser driven by a digital analog converter (DAC). During initialization a pair of comparators actuated at minimum and at maximum power levels for actuating a microprocessor to calibrate a DAC 23 between the minimum and maximum power levels rended of digital input changed to the DAC. The same comparators can be used during normal recording and reading operations for detecting under and over power conditions of the laser. Procedures for the calibration and over power and under power detection are described.

Abstract: A magnetooptic recorder uses a magnetooptic disk for any predetermined number of radially inward tracks which are designated as calibration tracks. One of the calibration tracks is selected as a laser calibration track. The selected track is high powered erased and a test pattern is written on the track. A test pattern is repeated at diverse levels of laser recording power. A test pattern preferably includes or is limited to the highest frequency to be recorded in the ensuing data recordings. The recorded test pattern is read back with the readback signal amplitude being envelope indicated and detected. A table of signal envelope values is created in a digital computer. The values then are fit to a curve using second order polynomial curve fitting techniques.

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: An optical disk has four copies or sets of its control data structures. The control data structure includes a disk definition structure DDS, a primary defect list PDL, and a secondary defect list SDL. Procedures are described for checking to whether or not all copies of the data structures have congruence. If not, all the tables are then made congruent and re-recorded on a disk. In the procedure, the copy having the greatest number of entries is first examined for determining whether or not congruence is possible. If congruence is not possible from the longest copy, then the next longest copy is used.

Abstract: In an optical disk player, such as for a magnetooptic player, wherein the data recorded on the optical medium are at recording at such high densities then intersymbol interference causes the peaks of the readback signals to become closer together resulting in phase errors. A transition selecting means is operative to select a transition indicated by the readback signal or a substitute transition indicated by a timed delay means generates a signal based upon the immediately preceding transition received from optical medium. Various embodiments of the invention are illustrated.

Abstract: A focus acquisition system includes providing a focus offset and changing the offset symmetrically for each measurement cycle. The amplitudes of the readback or tracking error signal are sensed and compared. When the amplitudes of the tracking error or readback signal is different at each of the offsets, then a new measurment cycle is performed after calculating a new offset value. The process is repeated until the temporary measurement offsets result in readback amplitudes that are substantially equal. A best focus is then indicated as being a position in which small defocussing will not substantially degrade the quality of the readback signal.

Abstract: A cached DASD controller is illustrated which is attached to a high speed serial channel, such as an optical fiber channel. The data rate of the serial channel is much greater than the data rate of a DASD connected to the controller. The serial channel has a relatively long propagation time such that synchronous operations between the host processor 10 and the DASD cannot be efficiently performed. Operation of a data transfer, whether read or write between the host processor 10 and the DASD is monitored. Whenever reading a copy of the track contents stored in cache or the DASD reaches either an index mark, a break point from a roll mode operation or certain write operations occur resulting in predetermined data being stored in cache, then a GOCACHE flag is set in a control portion of the controller. The device operations are then momentarily idled while cache to host processor data transfer operations are enabled.

Abstract: An optical disk recorder includes disk reflectance calibration means for measuring variations in disk reflectance over the recording area of the disk. Correction factors based on measured reflectance for adjusting sensed signal level and gain reduce the effects of varying reflectance on the sensed signal. In a preferred embodiment, the sensed signal is employed as a signal in quadrature to a tracking error signal for ensuring reliable track counting in a track seeking operation. In a grooved medium, reflectance is calibrated for both grooves and mesas between the grooves.

Abstract: A magnetic tape readback system is disclosed for a multi-track tape player. A single phase lock loop is provided for the channel circuits used for reading signals from the respective tracks on a multi-track tape. A common frequency determining circuit means is coupled to all of the phase lock loops such that the frequency of operation of the phase lock loops is stabilized. A capacitor which has a capacitance usable in the individual phase lock loops for determining a frequency of operation is commonly AC connected to all of the phase lock loops; in this arrangement none of the phase lock loops have the frequency determining capacitor. A capacitance AC couples and DC blocks each of the individual phase lock loops to the frequency determining capacitor such that the individual phase lock loops have their own reference DC levels and yet receive AC input from all of the other phase lock loops.

Abstract: An optical disk recorder is capable of operating with diverse types of optical media. A device initialization procedure is repeated for each receipt of each optical medium. Such procedure includes moving an objective lens to an extreme radial position, defocussing the lens at a most remote position, then calibrating the laser circuits to ensure that the emission of radiation from the laser will not inadvertently destroy signals recorded on the just received medium. Then the medium type is read from the medium and based upon the type indication, various additional calibrating procedures are followed and different sources of laser control values are used for signal exchanging operations between the recorder and received optical medium.

Abstract: This disclosure deals with an optical disk recorder/player (drive) of the type that receives a removable disk for signal exchanging operations. Once a disk is inserted into the drive, the rotation of the disk begins a period of accelerating rotational speed called spin up. During spin up, the focus and tracking systems of the drive are calibrated. Once the disks reach a desired operating rotational speed, a menu is provided for determining when to calibrate a laser in the drive for recording operations. Such writing or recording calibration of the laser occurs at different times in accordance with the types of signal processing functions to be performed with respect to the particular disk. Description includes a media library in which a plurality of optical disk drives are controlled in a manner for minimizing access times to any optical disk within the media library.

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 optimizied. 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: Rewriteable media, such as magnetooptic record members or disk has its recording controlled such that the recording is certifiable as meeting write once read many characteristics. Controls are introduced for the entire disk for indicating that the rewriteable disk is to be used for certified or vault writing, at least in some radial zones of the disk. Recording or writing operations are limited to those addresssable areas on the certifiable rewriteable medium that have not been previously written. Each of the addressable areas of the medium, in a disk termed, sectors, have a precursor portion called a control area which indicates the status of the sector and is used for preventing overwriting or erasure as well as controlling.

Abstract: A large capacity data storing disk includes a volume table of contents (VTOC) which identifies allocated ones of data storage tracks and identification of the data contents therein, indications of unallocated data storage track and an indication of which of the data storage tracks on the large capacity disk surface are unformatted. The indications may also include indications of unallocated "erased" tracks that do not contain data residuals from previous recordings. Those unallocated tracks having such erased condition in a count key data record format (CKD) require a home address record on each of the formatted tracks. The home address record may include indications of rotational position of defects to be skipped over during the recording and readback operations. A specific embodiment of the invention using a magnetooptic record medium is described.

Abstract: The focus acquisition system on optical disk recorder as well as other optical systems, uses repeated pulse position pulses with interlead coasting of an objective lens for providing a soft focus acquire. The pulse energization of the lens to move toward an in-focus condition overcomes stiction and friction. While the coasting allows the energy level applied to the lens movement to be minimal, i.e. soft, the purpose of the interdirectional pulse control actuation is to overcome friction without requiring large power to the lens which can cause an overshoot of the lens at the in-focus position. Compensation techniques and stopping the lens at the in-focus position are also shown.

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 extends 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.