Victor Company of Japan, Limited

Other

Matsushita Electric Industrial Co., Ltd.

Yutaka Osada

Yasuhiro Ueki

Kohjyu Konno

Kenji Koishi

Makoto Usui

Chikashi Inokuchi

Yuuichi Kamioka

Osamu Yanagisawa

Hironori Deguchi

Yuichi Hasegawa

Hideo Nomura

Takashi Kawai

Keiichi Kaneko

Yoshiyuki Miyabata

Susumu Sakakibara

Hideharu Eguchi

Ken Miyazaki

Tomonori Ueno

Takahiro Ochi

Toru Fujimoto

Mitsuhiko Ohta

Mitsuhiko Oohta

An optical disc apparatus reads the address information from an optical disc which has tracks and track spaces formed between tracks. The apparatus has an optical head which irradiates the disc with light and includes tracking detectors, divided into a first detector and a second detector in a track direction, detecting the light reflected from the disc and outputting detection signals, an adjusting circuit which adjusts amplitudes of the first and second detection signals and outputs the signals at a position where the address information is recorded, a differential amplifying circuit which outputs the differential signal which is the difference between the adjusted first and second detection signals, and an address detecting circuit which detects the address information based on the differential signal. As a result, the optical disc apparatus accurately detects whether information is being recorded on a correct track and improves the reliability during recording.

Optical disc apparatus and method for reading information from an optical disk having tracks and spaces between the tracks on which address information is recorded

Crosstalk between tracks, land prepit leakage, and effects of recording power modulation can cause the wobble signal period to change irregularly, thereby producing jitter in the recording clock which is derived by frequency multiplying the wobble signal. This problem is resolved by a recording clock generating circuit having an arrangement to average the wobble signal period, a timer for generating a rectangular wave with substantially the same period as the average period, and a frequency multiplying PLL for multiplying the timer output. The period averaging arrangement in particular determines the approximate average period at every wobble period and reflects the phase difference between the wobble signal and the timer in the timer setting so as to improve recording clock stability.

Recording clock generating device and method thereof

Of (A&plus;B) signal and (C&plus;D) signal for detecting a radial push-pull signal, the (A&plus;B) signal is multiplied with a predetermined coefficient k. The predetermined coefficient k is changed appropriately depending on an error rate upon decoding a land pre-pit, a lens shift amount of an objective lens of an optical pickup, and the levels of a land pre-pit signal and a wobbling signal relative to the level of (A&plus;B&plus;C&plus;D) signal. Consequently, the land pre-pit on an optical disc can be detected securely at a high precision at any time of recording time and reproduction time.

Recording and/or reproducing apparatus and recording and/or reproducing method capable of detecting a land pre-pit on disc securely at a high precision

Playback signal amplitude drops and continuity of the signal track amplitude is lost at the beginning the data recording area when data is incrementally written to optical discs such as DVD-R or DVD-RW media. Feed-forward control quickly settles semiconductor laser recording power to the target power level immediately after an incremental recording starts. While recording continues, feedback control maintains laser power at a desired recording power level even when the required current supply varies due to the temperature characteristics of the semiconductor laser when recording lasts for an extended period of time. A semiconductor laser control method and semiconductor laser control device thereby maintain laser power at a stable target recording power level quickly and for as long as recording continues.

Semiconductor laser control method and semiconductor laser control device

A period accumulating portion inputs a reference clock &ldquo;Clock 2&rdquo; and a wobbling pulse WBLPOL_I obtained by binarizing a wobbling signal extracted from a reproduction output from a DVD, and accumulates and counts reference clocks &ldquo;Clock 2&rdquo; in an interval of predetermined periods of the wobbling pulses WBLPOL_I so as to obtain a count value &ldquo;m&rdquo;. An average period detecting circuit obtains an average count value &ldquo;n&rdquo; corresponding to the interval of an averaged period of the wobbling pulse by dividing a count value of the reference clock &ldquo;Clock 2&rdquo; with a number of the predetermined periods. A divider generates a wobbling pulse WBLPOL_O having a constant period, deprived of a period fluctuation due to a prepit by dividing the reference clock based on the average count value. The phase of that generated wobbling pulse WBLPOL_O having the constant period is matched with the phase of a land prepit LPP by a LPP generating circuit, a phase comparator, an AC phase shifter and a PLL circuit, and the wobbling pulse, whose phase is matched, is outputted as a recording/reproducing clock signal WTCLK.

Recording/reproducing apparatus and method using accurate recording/reproducing clock signal

Multi-pulse trains of a forward laser beam are applied to an optical disc to record mark areas thereon. The multi-pulse trains correspond to the mark areas respectively. The multi-pulse trains represent information to be recorded. Detection is made as to an intensity of a reflected laser beam which results from reflection of the forward laser beam by the optical disc. The detected intensity is divided by a setting intensity to get a division result. A condition of recording of each of the mark areas is detected in response to the division result. An amplitude of each of the multi-pulse trains is controlled in response to the detected condition.

Method and apparatus for recording information on recording medium

A video disk recorder has a function for carrying out a linking on an optical disk and contains a predetermined data building-in circuit for supplying a predetermined fixed data as a playback data. Upon linking, a linking point is placed in a CPM area on the optical disk and the fixed data is recorded in this CPM area. Upon playback of the CPM area in which the linking is carried out, the fixed data supplied from the predetermined data building-in circuit is read out as the playback data.

Recording/playback apparatus capable of carrying out linking on optical disk, and optical disk recorded with linked data

An apparatus operates for recording and reproducing information on and from a recording medium formed with a track and pre-pits. The track has a wobble. The pre-pits are in a predetermined phase relation with the wobble of the track. The apparatus includes a pickup for reproducing a signal from the recording medium. A limiter operates for limiting an amplitude of the signal reproduced by the pickup in response to a limiting level, and thereby processing the signal reproduced by the pickup into a limiting-resultant signal. A filter operates for suppressing components of the limiting-resultant signal, and thereby processing the limiting-resultant signal into a filtering-resultant signal. The components have specified frequencies, and are caused by the pre-pits. The limiting level for the limiter is generated in response to the filtering-resultant signal. A signal caused by the wobble of the groove is extracted from the filtering-resultant signal.

Information recording and reproducing apparatus

An optical disk apparatus for stable tracking and reproduction of information recorded on a high density disk, the apparatus cancels various noise components in the tracking error signal. Disturbances caused in the tracking error signal, such as crosstalk from adjacent tracks, the positional shift of the photo detectors due to a change of the ambient temperature, an inclination of the disk surface to a laser beam causing a defocus of the laser beam, and defects on a disk are eliminated. The optical disk apparatus has a light source, a diffraction grid, a semi-transparent prism, a collimator lens, an objective lens, a concave lens, a cylindrical lens, a photodetecting device, a reproduction control circuit, a tracking drive circuit, and an actuator for displacing the objective lens.

Optical disk apparatus having an improved tracking control system

An access control device for use in an optical disk system provided with an information recording disk medium having a concentric or spiral track for recording information thereon, a recording/reproducing head for recording information on or reproducing information from the information recording disk medium, a tracking actuator for controlling the head in such a manner to follow a center of a track, a tracking error detection circuit for detecting a difference between the position of the head and the center of the track and a tracking drive circuit for driving the tracking actuator. Further, the access control device is used to move the recording/reproducing head to a desired or target track. Furthermore, the access control device is provided with a relative speed detection circuit for detecting the relative speed of the head with respect to the target track and reference-speed signal generation means for outputting a signal indicating a reference value of the relative speed. Additionally, the tracking drive circuit is adapted to be controlled according to the tracking error signal after controlled according to a difference between an output of the relative speed detection circuit and the reference speed signal when tracking control operation is started. Thereby, when an operation to be currently performed by the system is changed to the tracking control operation, the tracking control operation can be stably started and performed. Further, an access time can be substantially decreased.

Access control device

A speed and position control apparatus comprising: an encoder generating two-phase signals having a 90-degree phase difference to correspond to a movement of a carrier; and adder obtaining a sum of phase signals; a subtracter obtaining a subtraction of phase signals; a circuit making bi-leveled signals from the sum and subtraction signals; a circuit obtaining an exclusive OR signal based on the bi-leveled signals; a circuit generating differential signals of respective phase signals; a first selector selecting either of the differential signals by the exclusive OR signal; a first switch selectively outputting an output of the first selector or its opposite-polarity output signal based on the bi-leveled subtraction signal; a second selector selecting either of the respective phase signals by the exclusive OR signal; a second switch selectively outputting an output of the second selector or its opposite-polarity output signal based on the bi-leveled subtraction signal; a device inputting an AC component of the second switch output signal to a sample and hold circuit; and a device returning an output of the sample and hold circuit, which holds a sample value inputted during a predetermined period of time in response to a building-up of the exclusive OR output signal, to its input terminal so as to realize a DC restoration.

Speed and position control apparatus for positioning a movable object

A position control system for a read/write device for fast positioning the read/write device at a particular track of a disk having a tracking pattern in the recording medium. The system having a transportation unit for transporting the read/write device to a target track and a control loop containing a BAF (multi-peak band-pass filter), includes a position control unit for controlling the position of the read/write device so as for the read/write device to track the target track, and a storage unit for storing the internal variables of the BAF filter. When the operation by the transportation unit is switched to the operation of the position control unit, the operation of the BAF filter is performed in accordance with the internal values or initial values stored beforehand, a particular one of the variables stored beforehand is used for the operation by the position control unit, or a reference value of the speed control is adjusted in accordance with a particular one of the variables stored beforehand.

Position control system for read/write device

In a head position control apparatus, a magnetic pole disc mounted on a DC motor has a plurality of opposite magnetic poles arranged on its circumference in a predetermined relationship with tracks on a floppy disk. A sensor located close to the pole disc generates a pulse signal having pulses corresponding to the tracks and a voltage representing the actual speed of the motor. The pulses are counted in an incremental or a decremental mode. The difference between a track position indicating command signal from a keyboard and the pulse count is detected for deriving a direction signal which indicates the direction of the head and determines the count mode, a speed reference variable according to a predetermined transfer function and a switching signal when the difference reduces below a certain limit. A speed control signal is generated representing the difference between the speed reference and the actual speed of the motor. A position control signal is generated representing the difference between the amplitude of the pulse signal and a reference voltage. In response to the switching signal one of the control signals is applied to a polarity inverter for inverting or noninverting its polarity depending on the direction signal and on its amplitude relative to the reference voltage.

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Fujisawa, Japan

Yutaka Osada