Abstract: CD-ROMS of poor quality, such as those having eccentric center holes or uneven weight distributions circumferentially, are easy to wobble or otherwise vibrate when driven at high speed, overloading tracking and focusing servos and inviting read errors and retries. Each CD-ROM on being loaded into a CD-ROM drive is therefore checked as to its quality in terms of the speed of rotation at which the disk drive motor gains a steady state on being started up at a full supply voltage. The poorer the disk quality, the lower is the steady state speed of motor rotation. A poor quality disk is read at four times the standard audio CD speed, an intermediate quality disk at eight times that speed, and a good quality disk at twelve times that speed.

Abstract: CD-ROMS of more or less poor quality, such as those having eccentric center holes or uneven weight distributions circumferentially, tend to overload tracking and focusing servos and hence to invite read errors and retries. Each CD-ROM on being loaded into a CD-ROM drive is therefore checked as to its quality preparatory to reading. Either or both of the servos may fail to keep the read beam under control if the disk is not of good quality. Such unlocking of either or both servos is detected in terms of the number of transducer output pulses, the magnitude of transducer output voltage, or the number of read errors, during a complete disk revolution. Disk quality is first checked at four times the standard audio CD speed, then at eight times that speed, and finally at twelve times that speed.

Abstract: CD-ROMS of poor quality, such as those having eccentric center holes or uneven weight distributions circumferentially, are easy to wobble or otherwise vibrate when driven at high speed, overloading tracking and focusing servos and inviting read errors and retries. Each CD-ROM on being loaded into a CD-ROM drive is therefore checked as to its quality in terms of the speed of rotation at which the disk drive motor gains a steady state on being started up at a full supply voltage. The poorer the disk quality, the lower is the steady state speed of motor rotation. A poor quality disk is read at four times the standard audio CD speed, an intermediate quality disk at eight times that speed, and a good quality disk at twelve times that speed.

Abstract: CD-ROMS of more or less poor quality, such as those having eccentric center holes or uneven weight distributions circumferentially, tend to overload tracking and focusing servos and hence to invite read errors and retries. Each CD-ROM on being loaded into a CD-ROM drive is therefore checked as to its quality preparatory to reading. Either or both of the servos may fail to keep the read beam under control if the disk is not of good quality. Such unlocking of either or both servos is detected in terms of the number of transducer output pulses, the magnitude of transducer output voltage, or the number of read errors, during a complete disk revolution. Disk quality is first checked at four times the standard audio CD speed, then at eight times that speed, and finally at twelve times that speed.

Abstract: A CD-ROM drive is disclosed which usually is put to use with CR-ROMs of varying qualities which may, or may not, wobble during rotation, possibly resulting in the vibration of the complete device. On being loaded into the device, therefore, each disk is rotated at increasing speed preparatory to reading. The speed of disk rotation at which vibration due to disk wobbling builds up to a prescribed limit is held as a maximum allowable speed until the disk is unloaded. The disk is subsequently read at no more than the maximum allowable speed.

Abstract: CD-ROMS of poor quality, such as those having eccentric center holes or uneven weight distributions circumferentially, tend to overload b tracking and focusing servos and to invite read errors and retries. Each CD-ROM on being loaded into a CD-ROM drive is therefore checked as to its quality preparatory to reading. The disk is first rotated at eight times the standard audio CD speed, with both tracking and focusing servo gains set at matching values. If then at least either servo malfunctions, the disk is of poor quality, fit for reading at four or two times the standard audio CD speed. If both servos function normally, on the other hand, then the disk quality is rechecked at the same speed as before but with the servo gains lowered six decibels. A malfunctioning of at least either servo at this time indicates that the disk is of intermediate quality, to be read at eight times the standard audio CD speed.

Abstract: Disk apparatus for detecting address marks in the data of a zoned constant angular velocity (ZCAV) recording disk. The apparatus includes a detecting unit for detecting sector marks in the data. Time delay circuitry establishes a time delay between sector mark detection and an address mark detecting gate period. A portion of the time delay is established by a pulse count which is independent of the reproducing frequency corresponding to the zone of the sector mark. A second portion of the time delay is established responsive to the recording frequency. The time delay so established is used to position the address mark detecting period to reliably detect the address mark.

Abstract: A reproducing rate control apparatus for an optical disk includes a synchronizing clock generating unit which generates a synchronizing clock pulse with a phase locked to a phase of a digital reproduction signal. A signal processing unit generates a demodulated data signal from the digital reproduction signal in accordance with the synchronizing clock pulse, wherein the demodulated data signal is written to a memory in accordance with the synchronizing clock pulse, the demodulated data signal is read from the memory in accordance with a read reference clock pulse, and the read demodulated data signal is processed through an error correction so that a processed demodulated data signal is output. A frequency detecting unit detects whether the frequency of the synchronizing clock pulse is within a predetermined range of frequencies centered at a standard frequency.

Abstract: An optical disk device generating reproduced data based on a reproduced digital signal which is derived by tracking a track on an optical disk with an optical pickup is shown. A bit-frequency-information generation unit measures a bit frequency of the reproduced digital signal after transition of the optical pickup in a seek operation, and generates measured-bit-frequency information which indicates a measured bit frequency measured thereby. In a bit-frequency setting unit, if there is a difference between the measured bit frequency and a specified bit frequency, the measured-bit-frequency information is corrected so as to adjust the bit frequency of the reproduced digital signal to the specified bit frequency by a given amount of correction, and is produced as setting-bit-frequency information.

Abstract: An optical disk reproducing apparatus uses a spindle motor having a low torque to reduced power consumption and manufacturing cost while maintaining a low error rate for reproduced data. The spindle motor is rotated at a constant rotational speed under a CAV control when a pick-up is moved. The rotational speed of the spindle motor is switched to a reference linear speed under a CLV control when a reproducing operation is performed. The reference linear speed is established for each of the zones of a recording area of an optical disk. The reference linear speed is determined by generating a zone clock set for each of the zones. A frequency error signal is generated by comparing the zone clock with the reproduction data so as to maintain the spindle motor at the reference linear speed determined by the zone clock.

Abstract: This digital data reproducing apparatus is adapted to prevent reproduction errors of data, wherein a read gate opened when a fixed pattern in a header field for phase locking is detected is kept opened until the data reproduction in a data field is completed, whereby the phase locking in the data field is performed still in the same low-speed mode as when the PLL pull-in is completed in the header field, with the responding ability lowered to defects such as voids or the like in the phase locking pattern area in the data field.This digital data reproducing apparatus is adapted to prevent reproduction errors, wherein, when a reproduced data in a data field is locked, a read gate is opened after a fixed pattern recorded for phase locking is surely detected, so that the phase locking is started in a high-speed mode, while avoiding erroneous operations of the PLL.

Abstract: A method and apparatus well suited for the conversion of a digitized audio signal into analog form with as wide a dynamic range as possible. A digital dither signal is added to a digital audio or like data signal to provide a digital data/dither signal. This digital data/dither signal and the digital dither signal are both converted into an analog data/dither signal and an analog dither signal respectively, and the analog dither signal is subtracted from the analog data/dither signal to obtain an analog data signal equivalent to the digital data signal. The level of the incoming digital data signal may be so high that when the digital dither signal is added thereto, the total level of the data/dither signal may exceed the capacity of the digital to analog converter in use.

Abstract: A method and apparatus well suited for the conversion of a digitized audio signal into analog form with as wide a dynamic range as possible. A digital dither signal is added to a digital audio or like data signal to provide a digital data/dither signal. This digital data/dither signal and the digital dither signal are both converted into an analog data/dither signal and an analog dither signal respectively, and the analog dither signal is subtracted from the analog data/dither signal to obtain an analog data signal equivalent to the digital data signal. The level of the incoming digital data signal may be so high that when the digital dither signal is added thereto, the total level of the data/dither signal may exceed the capacity of the digital to analog converter in use.

Abstract: A method and apparatus well suited for digitizing an audio signal with as wide a dynamic range as possible. An analog dither signal is added to an analog audio or like data signal to provide an analog data/dither signal. This analog data/dither signal and the analog dither signal are both converted into a digital data/dither signal and a digital dither signal respectively, and the digital dither signal is subsequently subtracted from the digital data/dither signal to obtain a digital data signal equivalent to the analog data signal. The magnitude of the incoming analog data signal may be so high that when the analog dither signal is added thereto, the magnitude of the resulting data/dither signal may exceed the capacity of the analog to digital converter in use. In that case the analog dither signal is either gated off or reduced in magnitude, with the result that the analog to digital converter inputs either the data signal only or the data/dither signal having a magnitude not exceeding its capacity.