Abstract: An automated data storage library accesses data stored on storage media contained in cartridges in response to commands from an external host. The cartridges may include cartridge memory and a component in the library may include a cartridge memory interface for reading data from and/or writing data to the cartridge memory. When a cartridge is to be stored in the library, the library modifies the contents of the cartridge memory, or the contents of the storage media such that the data stored on the cartridge becomes inaccessible, thereby preventing access to the data outside of the library. To perform an authorized access, the library restores the contents of the cartridge memory or the storage media. Alternatively, the library provides a correction or correction algorithm to the drive to allow access to the data stored on the storage media without removing the access protection of the storage media.

Abstract: A method to read (N) sequential files written to an information storage medium, and then skip the next (M) sequential files. The method initially identifies the (M) files to be skipped. After identifying the (M) files to be skipped, the method reads the (N) files.

Abstract: A method to read information from a tape storage medium, where that tape includes a calibration region and a data region. The method uses a read channel having a first detection mode and a second detection mode. The method initializes the first detection mode and forms a calibration waveform comprising information read from the calibration region using the first detection mode. The method then defines a plurality of bit cell boundaries, initializes the second detection mode, and reads information from the data region using the second detection mode.

Abstract: A method to read information from a tape storage medium, where that tape includes a calibration region and a data region. The method uses a read channel having a first detection mode and a second detection mode. The method initializes the first detection mode and forms a calibration waveform comprising information read from the calibration region using the first detection mode. The method then defines a plurality of bit cell boundaries, initializes the second detection mode, and reads information from the data region using the second detection mode.

Abstract: A method of reducing data expansion during data compression is provided that allows the coding scheme used to compress data to be swapped between two or more coding schemes. Specifically, a coding window is provided that allows analysis of the compression potential of data within the coding window. The data within the coding window then is analyzed to determine the compression potential of the data. If the compression potential of the data exceeds a first predetermined value, the coding scheme used to compress the data within the coding window is swapped from one coding scheme to another. Preferably the first predetermined value is programmable and is related to the bit cost required to swap back and forth between coding schemes. The two preferred coding schemes are ALDC Lempel-Ziv 1 coding and a pass-through coding scheme wherein raw data is passed unencoded.

Abstract: In a pulse width modulated read signal channel for an optical disk drive, a data-transition threshold is maintained for data detection by a threshold tracking circuit that estimates the amplitude centerline data-transition threshold from the most recent maximum and minimum values of the read signal waveform. To improve the accuracy of the response of the centerline estimator, the threshold is increased or decreased based on the phase error at each read signal transition through the data-transition threshold. In addition, defects in the optical recording media are detected, and a defect present signal is used to inhibit the transition phase error input to the centerline estimator. This prevents the estimator from moving the threshold to an incorrect stable level. In addition, the defect present signal boosts the error feedback in the centerline estimator. The estimator then more quickly follows the read signal waveform.

Abstract: A write-once read-many (WORM) optical disk recorder automatically calibrates its laser to emit a laser beam of a desired power level. While writing data to the WORM disk, a laser test signal is written to a laser checking area termed Automatic Laser Power Correction (ALPC) field. If the emitted laser test signal has a power level outside an acceptable power level window, then inappropriate laser power is indicated. Then, in an error recovery procedure (ERP) the laser power is calibrated in the data sector to be written to using short spaced-apart laser test signals. After successful calibration, data are written to the sector. The test signals appear as burst errors that can be corrected by a suitable error correction code. If such calibration is not successful then a write calibrate sector, WCS, is created and used for an extensive automatic calibration. In the WCS both laser power level is calibrated. The calibration result information is written to WCS for later use.

Abstract: A light intensity, direct overwrite, magneto-optical system generates signals such that, during the formation of a recording mark on an optical disk, a laser is driven a) at a pedestal power level, then b) at a quench power level for a first quench period t.sub.1, the quench power level being less than the pedestal power level, then c) at a write power level for a write period t.sub.2 whereby the reference bit becomes oriented in the writing direction, the write power level being greater than the pedestal power level, then d) at the quench power level for a second quench period t.sub.3, and then e) at the pedestal power level until the formation of another recording mark begins. The system is provided with a controller to determine optimal lengths of the quench periods t.sub.1 and t.sub.3, thereby reducing thermal interference between closely spaced recording marks. From sample recording marks, recorded with different quench periods t.sub.1 and t.sub.

Abstract: In a write-once read-many (WORM) optical disk device recorded unipolar pulse signals having a high lineal recorded densities are read back using an inverted analog signal processing channel that processes the read back signal after polarity inversion of the read back signal. Some fields in each sector of an optical disk are recorded at a specific maximal mark density pattern. Read back of such fields is signal processed using non-inverted read back analog signal processing, i.e. the read back unipolar pulse signal is processed without polarity inversion. In the non-inverted read back, automatic gain control of the read signal is turned off such that amplification of the read back signal is at a constant gain. Also during non-inverted read back, low read back signal amplitude results in degating the read back output.

Abstract: The present invention provides a method and an apparatus to accurately and consistently distinguish blank sectors from written sectors on optical media despite drive and media variations. A readback envelope threshold is established each time optical media is mounted into an optical drive. In one embodiment, the gain of readback amplifiers are set to a first level, the optical head seeks to and reads a sector or set of sectors on the optical disk known to have information recorded thereon and a first readback envelope generated. The gain of the readback preamplifier is then set to a second level, the optical head seeks to and reads another sector or set of sectors known to have information recorded thereon and a second readback envelope generated. The readback threshold is calculated from the amplitudes of the first and second envelopes.

Abstract: A write-once optical disk data recorder automatically calibrates a laser during a write data operation and using write pulses focussed to a disk. First, the laser is calibrated using a non-focussed laser beam. Each sector of the disk has a laser checking or test area, such as an automatic laser power correction field (ALPC) of two byte lineal extent. During a first write operation after a power up or disk load, a pulse width modulated (PWM) laser test signal is recorded using a laser power level set using the non-focussed laser beam and an indicated desired recording power level on the disk. The recorded laser test signal is read back. The length of the read back laser test signal is measured. The measured length is then compared with a desired length of the PWM laser test signal that indicates a desired laser power level. That is, as laser recording power levels increase, a resultant recorded signal grows in size. This property is used to measure laser power for calibrating laser operation.

Abstract: The present invention provides a method and an apparatus to accurately and consistently distinguish blank sectors from written sectors on optical media despite drive and media variations. A readback envelope threshold is established each time optical media is mounted into an optical drive. In one embodiment, the gain of readback amplifiers are set to a first level, the optical head seeks to and reads a sector or set of sectors on the optical disk known to have information recorded thereon and a first readback envelope generated. The gain off the readback preamplifier is then set to a second level, the optical head seeks to and reads another sector or set of sectors known to have information recorded thereon and a second readback envelope generated. The readback threshold is calculated from the amplitudes of the first and second envelopes.

Abstract: A record carrier having essentially circular tracks concentrically located around a point of rotation. The record carrier is divided into circular zones each having m tracks, where m is an integer. Each track within a zone is subdivided into n sectors, where n is an integer which is constant per zone and which increases as the zone is more remote from the point of rotation. Each sector including a header portion and a data portion. The header portions in the radial direction in each zone are in line. In each zone the condition of m*n=j*k is satisfied, where is j an integer greater than or equal to 2 and is constant for each zone, and k is an integer.

Abstract: Apparatus and method are provided to increase the capacity of spiral track data storage disks while improving the reliability of access to sectors on the disk by permitting previously unusable sectors immediately following a band boundary to be reliably accessed. In accordance with the present invention, an optical drive controller is provided having a clock for generating a clock signal with a frequency of f.sub.N and a cycle slipper for generating a slipped clock signal with a frequency of f.sub.N-1 from the clock signal. The controller also includes a device for enabling the slipper when an optical head is positioned opposite a sector in a band N-1 during a seek operation to a target sector in band N, and for disabling the slipper when the optical head is positioned opposite the end of the last sector in band N-1. Thus, identification information pertaining to sectors in band N-1 is processed at a data transfer rate of f.sub.N-1 and the data transfer rate is switched to f.sub.

Abstract: An envelope follower is provided which reduces defect propagation when reading analog information signals from a read head of, for example, an optical drive or a magneto-resistive tape drive. In a preferred embodiment, the envelope follower includes a differential amplifier, to sense the difference between the amplitude of the information signal and an envelope voltage across a capacitor, and a current mirror, responsive to the differential amplifier, to charge the capacitor at a predetermined rate when the amplitude of the information signal exceeds the envelope voltage. When the amplitude of the information signal is below the envelope voltage, the current mirror is deactivated by the differential amplifier and the capacitor is allowed to discharge through a voltage divider.

Abstract: Apparatus and method are provided to increase the capacity of spiral track data storage disks while improving the reliability of access to sectors on the disk. In one embodiment, employed when logical tracks on an optical disk are grouped into concentric bands, previously unusable sectors immediately following a band boundary can be reliably accessed. In accordance with this embodiment, when the target sector is, for example, the first sector of band N and a laser beam from a read head lands on a sector in the previous band N-1, the clock governing the data transfer rate is set to the frequency of the band N-1 and a sector in that band is detected and identified. Based upon the period of sectors in the band N-1, a delay interval is computed which ends when the last sector in the band N-1 rotates past the laser beam. Sector mark detection is disabled during the delay interval and the clock frequency changed to that of band N.

Abstract: To sense the presence of written data on an optical disk, the readback signal from the disk is detected, and the intervals between detected signal events are measured. That signal event occurring at an expected time delta after the preceding signal event indicates a valid data signal time delta. Those signal events occurring at an unexpected time delta after the preceding signal event indicates the readback signal to be noise. If the count of valid signal time deltas minus the unexpected time deltas attributed to noise accumulates rapidly along a given track within a given sector of the optical disk that sector is determined to be written. Provision is made for counting signal events in accordance with the specific run-length limited in use.

Abstract: A drive circuit for a laser which has the capability of eliminating transient conditions when switching a high frequency modulator on or off, and including elements for maintaining desired depth of modulation. These capabilities are included in a circuit that automatically compensates for changing conditions due to temperature, laser characteristics and fluctuations in media reflectivity.

Abstract: Data-storing disks, preferably each disk having a single spiral track, have addressable tracks that are independent of the length of disk or spiral track revolutions. Each revolution may contain a non-integral number of addressable tracks and sectors. An optical disk is used to describe the invention. The circumferential location of the tracks and sectors precess circumferentially. A plurality of radially disposed revolution bands each contain a fixed number of the revolutions an increasing number of the addressable tracks in the radially outer more ones of the bands. It is preferred that the number of bands be 2.sup.n, where n is an integer. Each band is divided into a plurality of revolution groups, each group having a fixed number of revolutions. Each group in a band has a like number of the addressable tracks. A so-called anchor sector has one end anchored to a reference circumferential position on the disk.

Abstract: A circuit for simultaneously detecting both MO and ROM signals reflected from an optical disk so that both signals are present and useable without switching from one to the other. The circuit eliminates switching time and switching transients. Two photodetectors are arranged to sense P and S components of polarized light in order to stimulate a differential amplifier and produce an output representative of MO recorded data. A second amplifier is connected to at least one of the photodetectors to produce an output representative of ROM recorded data and also representative of defects in the MO portion of the optical disk.