Hitachi, Ltd.

Masahiro Takasago

Takeshi Maeda

Kazuo Shigematsu

Yasumitsu Mizoguchi

Yoshito Tsunoda

Motoo Uno

Toshimitsu Kaku

Osami Kushizaki

Hisataka Sugiyama

Takuya Mizokami

Tokuya Kaneda

Shinichi Arai

Masuo Kasai

Toru Kawashima

Takakazu Huno

Koji Muraoka

Masanori Matsuzaki

Zenji Tsutsumi

Kazuo Isaka

Masamichi Ito

Noritaka Narita

Tokuya Kaneko

Kouji Muraoka

Akira Takagishi

Toshiharu Kon

Disclosed is an optical recording and reproducing apparatus comprising a light source directing a light spot toward a recording medium, a detection system detecting light reflected from the recording medium to derive an electrical signal from the reflected light, an information processing circuit modulating the intensity of the light spot according to writing pulses to record information on the recording medium and using the electrical signal to reproduce information from the recording medium, and a tracking servo circuit carrying out tracking servo operation on the basis of the electrical signal and including an extracting circuit connected to a source of extracting pulses having a pulse width at least equal to the writing pulse width so that writing pulse parts contained in the electrical signal are extracted during recording information, whereby a track offset occurring during information recording can be minimized, and the stability of the tracking servo system can be improved.

Method and apparatus for optical recording and reproducing with tracking servo reducing track offset

A tracking following apparatus for an optical disk device includes an objective for forming a light spot on an optical disk, a fine actuator for driving the objective, a coarse actuator for driving the fine actuator means, a detector for sensing a relative positional error between the light spot and a track on the optical disk, an RAM for keeping therein a drive signal associated with a rotation of the optical disk to drive the coarse actuator, an attenuator for reading from the RAM a drive signal associated with a disk rotation angle when the error is sensed by the detector and attenuating the signal, and an adder for adding the signal attenuated by the attenuator to the error signal sensed by the detector and thereby generating a drive signal to drive the coarse actuator.

Tracking following apparatus for optical disk device

A PLL circuit produces a synchronous signal by utilizing a regenerative clock signal in a VFO portion in a regenerative signal which was read out from a recording medium in sections. When a defective portion is present in a regenerative clock signal, the same sector is read out again from the recording medium to obtain the regenerative signal. A loop gain of the PLL circuit is made to be low in the defective portion of the regenerative signal which was read out again, thereby to prevent the synchronous fault of the PLL circuit due to the defective portion.

Apparatus for reproducing data from a regenerative signal using a PLH

It is intended that the relative head speed for a track in seeking is detected precisely without being influenced by track swing due to eccentricity of a disk. To this end, the current (proportional to the acceleration of an optical head) for a voice coil motor for driving an optical head is previously detected while track following control is executed and the detected data are stored in memory. In seeking, the sum of a detected current (representative of the acceleration of the head for a fixed component) and the data supplied from the memory is integrated to provide the relative speed of the head for a track. The relative speed signal is added to the differential signal of a pulsated signal of the track traversing signal of the head. The addition output represents the precise relative speed signal in consideration of track swing. If the voice coil motor is controlled so that this relative speed coincides with a target speed signal, the head speed can be controlled without being influenced by the track swing.

Controlling positioning of recording/reproducing head by combining a

An amplitude difference between a reproduction signal from a preformat portion of an optical disk and a reproduction signal from a recording portion of user's data is obtained. When the amplitude difference exceeds a predetermined value, a first gain value which was set for information from the preformat portion is used as a gain value of an AGC circuit for reproduction and a gain control of the reproduction signal is performed. On the other hand, when the amplitude difference is smaller than the predetermined value, a second gain value which was set for the user's data is used. Thus, a situation such that a noise and a remaining signal of the user's data which was not erased are erroneously recognized as an inherent reproduction signal can be prevented. A discrimination to see if the data has been recorded in the recording portion of the user's data or not can be also accurately performed.

Automatic gain control method and apparatus in optical disk system

Disclosed is an optical recording and reproducing apparaus comprising a light source directing a light spot toward a recording medium, a detection system detecting light reflected from the recording medium to derive an electrical signal from the reflected light, an information processing circuit modulating the intensity of the light spot according to writing pulses to record information on the recording medium and using the electrical signal to reproduce information from the recording medium, and a tracking servo circuit carrying out tracking servo operation on the basis of the electrical signal and including an extracting circuit connected to a source of extracting pulses having a pulse width at least equal to the writing pulse width so that writing pulse parts contained in the electrical signal are extracted during recording information, whereby a track offset occurring during information recording can be minimized, and the stability of the tracking servo system can be improved.

Method and apparatus for optical recording and reproduction with

An optical disk storage access method using a fine and coarse actuators for positioning a light spot to an intended track on the disk, wherein a pulse is generated each time the light spot has traversed a track, the pulses are counted to determine the distance from the current spot position to a target track, the fine actuator is activated depending on the measured distance, and the fine and coarse actuators are operated in unison so that the light spot is positioned to the target track.

Optical disc access method and optical disk storage using coarse and

An optical disk is provided with a dedicated track area for recording optical conditions for read and write operations. The apparatus includes different types of demodulating circuits for allowing any type of demodulation to be adopted. After parameters, recorded on the dedicatad track area through phase encoding demodulation, are read out, the demodulating circuit compatible with the modulation type adopted in recording the data is selected for demodulation of the data.

Optical recording/reproducing method and apparatus for optical disk

An optical recording/reproducing apparatus for recording and reproducing information along tracks on an optical disc by irradiating the optical disc with a laser beam comprises a tracking error detecting circuit for detecting the digression of the laser beam from the center line of each track and a level detector for detecting that the output of the tracking error detecting circuit exceeds a predetermined level. An operation for recording information in the optical disc by the laser beam is stopped when the output of the level detector takes a predetermined state indicating that the output of the tracking error detecting circuit exceeds the predetermined level, for a first predetermined time, and a signal indicating the occurrence of off-track is generated when the duration time of the predetermined state in the output of the level detector exceeds a second predetermined time which is longer than the first predetermined time.

Defect detecting optical apparatus enabling recording in an alternate

An optical information recording and reproducing apparatus for irradiating a disk-shaped recording medium having spiral tracks with a light beam so that the information recorded along the tracks may be reproduced. The apparatus is equipped with a circuit for detecting the displacement of the light beam from said tracks and a clipping circuit for clipping a tracking error signal or the output signal of said detecting circuit with a predetermined threshold value. The light beam has its position corrected along the tracks in accordance with the output signal of said clipping circuit so that it may be prevented from tracking erratically.

Optical information recording and reproducing apparatus with tracking

In an optical position detecting apparatus using moire, two light receiving elements are associated with a single light emitting element, and moire or grating portions of an auxiliary moire i.e., fixed sub-scale opposing the respective light receiving elements are arranged such that detection signals produced from the two light receiving elements upon movement of a movable moire i.e., main scale are substantially 180.degree. out of phase. The difference between the detection signals from the light receiving elements is used as a positioning signal, and the sum of the detection signals from the light receiving elements is used as a signal for controlling the input of the light emitting element.

Optical position detecting apparatus for positioning an actuator

In an optical memory apparatus wherein predetermined information is optically recorded on a recording medium along guide grooves previously formed and then played back; an optical memory apparatus wherein, using a tracking signal and a signal indicating the quantity of reflected light at the time at which a projected light beam passes through the guide grooves, the directions in which the light beam passes through the grooves and the number of the guide grooves to be passed are detected, a seek control is performed by adding and subtracting the numbers of the guide grooves to be passed, depending upon the directions of passage, and fine positioning is thereafter performed by the use of the tracking signal.

Optical memory apparatus

A method of detecting a light spot control signal is disclosed in which, when information is reproduced from an optical disk for optically recording information, a signal level obtained at a high-reflectivity portion of the optical disk is taken out of a signal reproduced from the optical disk, and is used as a control signal, which controls a light spot so that it tracks information stored in the optical disk.

Method of detecting light spot control signal

An optical information processor records predetermined information along a track on a recording medium through the irradiation of a light beam intensity-modulated in accordance with the predetermined information. A tracking signal obtained when the light beam traces the track, is compared with first and second preset values which define a predetermined range. When the tracking signal departs from the predetermined range, the intensity modulation of the light beam or the recording operation is stopped, thereby preventing data destruction which otherwise occurs due to the digression of the light beam from the track.

Optical information processor

An optical information recording system in which predetermined information is recorded by a first laser light beam on a recording medium along a guiding groove previously formed in the recording medium. Second and third laser light beams are projected onto the recording medium at positions deviated from the center of the guiding groove and preceding and succeeding to the first laser beam. A pattern in which no mutual interference of information to be recorded by the first laser beam is present is detected from an information signal which modulates the intensity of the first laser light beam. A difference is determined between the quantity of light reflected upon illumination of the recorded pattern by the second laser beam chronographically succeeding to the first laser beam and the quantity of light reflected upon illumination by the third laser beam. The position of the first laser beam is controlled on the basis of the thus determined difference for effecting an information tracking operation with improved accuracy.

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Odawara, Japan

Masahiro Takasago