Hitachi, Ltd.

Shigeki Inoue

Akio Fukushima

Kazuhiko Ono

Hiroshi Minoda

Eiji Ikeda

Hiroaki Shioyama

Yoshimi Iso

Harushige Nakagaki

Takao Arai

Nobutaka Amada

Hiroyuki Kimura

Masafumi Nakamura

Takashi Takeuchi

Tsutomu Noda

Shin-ichi Ohashi

Toshifumi Takeuchi

Hiroyuki Tanaka

Yutaka Nagai

Hiromichi Tanaka

Masaharu Kobayashi

Yukio Fukui

Toshifumi Shibuya

Isao Akitake

Tatsuo Baba

Shinichi Ohashi

Eijiro Oshitani

A method and apparatus for reproducing data from an optical disc which has a plurality of recording layers reproducible from one side of the optical disc, and in which the disc is recorded in the OTP (Opposite Track Path) type. Upon receipt of a command of pausing, a pausing operation is performed by switching a moving direction of a focal point of an optical pickup in accordance with layer information of the recording layer to be currently reproduced.

Optical disc apparatus and method

An optical disc apparatus for recording information and/or reproducing on an optical disc which has at least two recording layers including layer and layer reproducible from one side of the disc. The apparatus includes an optical pickup having a laser source, an objective lens, and an actuator. A controller is provided which obtains a present layer information of a sector recording layer from light reflected from the disc, confirms a target layer information of a target recording layer, judges whether the present layer information is the same as the target layer information, and outputs a first control signal to the actuator when it is judged that the present layer information is layer and the target layer information is layer and outputs a second control signal to a slider.

Optical disk apparatus

A method for reproducing information on a dual layer disc which has two recording layers including layer and layer reproducible from one side of the &lsqb;disk&rsqb; disc, wherein each layer has a plurality of sectors. The method includes the steps of emanating an optical beam from a laser source, concentrating the optical beam on a recording layer with an objective lens, moving the objective lens in the direction of the thickness of the &lsqb;disk&rsqb; disc so that a focal point of the objective lens is focused on one layer of the two recording layers, obtaining a present layer information of a sector of the recording layer being reproduced from the reflected light from the &lsqb;disk&rsqb; disc, confirming a target layer information of a target recording layer of a target information, and moving the objective lens in a direction of the thickness of the &lsqb;disk&rsqb; disc until the focal point of the objective lens is focused on layer 1 when the present layer information is layer and the target layer information is layer

Optical disc apparatus accessing method and system therefor

There are provided a plurality of information recording surfaces to be reproduced on one side of an optical disc to be reproduced, and when accessing control of an optical pickup over a plurality of recording layers is performed, first, a beam focal point of the optical pickup is moved using a moving device to the recording layer on which target information is recorded to thereby perform switching processing of information recording layers during reproduction, after which accessing control of the optical pickup is performed using control processor similar to the access between the same recording layers, and with respect to the pausing operation, in a layer in which information is recorded from the inner circumference to the outer circumference, one track jumping is repeated toward the inner circumference, while in a layer in which information is recorded from the outer circumference to the inner circumference, one track jumping is repeated toward the outer circumference.

An optical disk apparatus for reproducing or recording and reproducing two or more sorts of optical disks whose recording plane heights are different is arranged to reproduce or record data from or on the optical disk transparently to the user and without the users intricate operations. For this purpose, the optical disk apparatus provides a disk discriminating circuit for discriminating the disks whose recording plane heights are different. The disk discriminating circuit operates to discriminate the disk before reproducing or recording the disk mounted to the optical disk apparatus and switch the optical system and the circuit system to the suitable ones to the discriminated disk and then reproduce or record the data from or on the disk.

Method and apparatus for automatically discriminating types of optical disks

There are provided a plurality of information recording surfaces to be reproduced on one side of an optical disc to be reproduced, and when accessing control of an optical pickup over a plurality of recording layers is performed, first, a beam focal point of the optical pickup is moved using a moving device to the recording layer on which target information is recorded to thereby perform switching processing of information recording layers during reproduction, after which accessing control of the optical pickup is performed using control processing circuit similar to the access between the same recording layers, and with respect to the pausing operation, in a layer in which information is recorded from the inner circumference to the outer circumference, one track jumping is repeated toward the inner circumference, while in a layer in which information is recorded from the outer circumference to the inner circumference, one track jumping is repeated toward the outer circumference.

There are provided a plurality of information recording surfaces to be reproduced on one side of an optical disc to be reproduced, and when accessing control of an optical pickup over a plurality of recording layers is performed, first, a beam focal point of the optical pickup is moved using a moving means to the recording layer on which target information is recorded to thereby perform switching processing of information recording layers during reproduction, after which accessing control of the optical pickup is performed using control processing means similar to the access between the same recording layers, and with respect to the pausing operation, in a layer in which information is recorded from the inner circumference to the outer circumference, one track jumping is repeated toward the inner circumference, while in a layer in which information is recorded from the outer circumference to the inner circumference, one track jumping is repeated toward the outer circumference.

An optical disk reproducing apparatus for reproducing at a high access-speed an optical disk on which data has been recorded at a constant linear velocity (CLV) includes a control circuit for controlling reading of the disk recorded at a CLV to be rotated at a constant angular velocity (CAV), and a processor for changing the frequency of a reference clock to determine the processing timing of the reproduced digital signal in accordance with a transmission speed of the digital information signal picked up from the disk. A motor for driving the disk can be rotated at a constant revolution rate upon access to the disk, and thus it is possible to remove one of the factors for determining the access time in the conventional CLV type reproduction system, or the time for controlling the motor to rotate for a constant linear velocity in accordance with the position of the optical pickup.

Disk reproducing apparatus capable of increasing speed of access to

In a disc playback apparatus using an optical pickup or the like, any flaws on a track of the disc are detected using: a first level detector for detecting a maximum value level of a recording information signal of an output of the pickup; a second level detector for detecting a change of the maximum value level of the recording information signal; and a comparator for comparing outputs of the above first and second level detectors. When any flaws are detected, a driving signal of a driving device for the pickup is held to a fixed reference potential.

Disc playback apparatus

A tracking servo circuit for controlling an optical pickup is used in a tracking error detecting device including an optical system for forming on an optical disc a main light spot for illuminating a pit on the optical disc and forward and backward sub-light spots. The forward and backward sub-light spots are disposed before and behind the main light spot in the moving direction of a track with a small distance between each of the sub-light spots and the main light spot and are shifted from the center line of the track, so that a half of each sub-light spot area is placed on the pits of the track. The tracking servo circuit includes photodetectors for detecting reflected light based upon the forward and backward sub-light spots, a tracking-error-signal detecting circuit for detecting a difference between output signals from the photodetectors, a tracking control circuit for controlling on the basis of an output signal from the tracking-error-signal detecting circuit an optical pickup for reading out a recorded signal which is recorded on a spiral track of the optical disc in the form of a row of pits, and a delay circuit for delaying the output signal from the photodetector. A difference between the output signal delayed by the delay circuit and the output signal from the photodetector is used as a tracking error signal.

Plural beam tracking servo including delay compensation

A servo circuit for a signal reproducing apparatus for reproducing signals from a record medium such as a disc utilizing an optical pickup, wherein a variable gain amplifier is arranged in a servo loop between a pickup and an actuator so that the pickup is caused to track a signal track in accordance with a servo error signal produced by the variable gain amplifier. A playback condition of a disc is discriminated by detecting the number of errors in a signal reproduced from a recorded signal on the disc by the pickup, and a gain of the variable gain amplifier is controlled by the discrimination output so that the variation of the servo error signal caused by a difference in reflectance between individual discs is eliminated and a loop gain appropriate to an individual disc is automatically set.

Servo circuit for a signal reproducing apparatus

In a pulse width detector circuit, a high-level pulse width and a low-level pulse width of a digital signal derived by slicing an analog signal reproduced from a disc at a predetermined level are independently measured and maximum or minimum values thereof in a predetermined time interval are stored, and an average value, sum or difference of the maximum or minimum high-level pulse width and the maximum or minimum low-level pulse width is calculated to detect a correct pulse width of original data recorded on the disc.

Digital player using a pulse width detector

An information reproducing apparatus having a tracking servo control loop for causing an information reading unit including device for detecting a tracking error signal for tracking an information bearing track on a disc, to track the information bearing track in accordance with the tracking error signal so as to reproduce information in accordance with an information signal read by the information reading unit. A circuit for extracting a discrimination signal for discriminating a negative feedback region of the tracking error signal is provided so that a tracking servo control loop is closed in the negative feedback region.

Tracking servo control unit for an information reproducing apparatus

Disclosed is a disc or tape signal reproducing apparatus having a first speed control loop in which the duration of a specific pulse in the PCM signal recorded on the disc or tape is detected and the current sync signal interval is anticipated from the duration of the pulse so that the motor speed is pulled into the operation range of the sync signal detector, and a second speed control loop which controls the motor speed basing on the sync signal reproduced by the sync signal detector. The motor speed is controlled by the first speed control loop until the sync signal detector detects the sync signal, thereafter the motor speed is controlled by the second speed control loop basing on the reproduced sync signal.

Playback speed control system

In a power amplifier having a power circuit of a switching control system, a protective device for the power amplifier has connected to the amplifier a means for detecting an abnormal signal produced at the amplifier, and a control means connected between the detecting means and the power circuit to the amplifier so as to cut off a switching control signal to the power circuit when an abnormal signal is generated at the amplifier, thereby stopping the power circuit from operating to cut off power to the power amplifier. The detecting means is formed of a detecting circuit connected to the output end of the amplifier so as to detect the DC output voltage or excessive current from the amplifier, and a driving circuit connected to the detecting circuit so as to be operated by the output signal from the detecting circuit. The control means is formed of a switching control signal cut off circuit connected between the driving circuit and the power circuit so as to be supplied with the output voltage or current from the detecting means when it detects the DC output voltage or excessive current from the amplifier, thereby cutting off the switching control signal cut-off circuit.

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Toyokawa, Japan

Shigeki Inoue