Sharp Kabushiki Kaisha Corporation

Toshihisa Deguchi

Kenji Ohta

Shigeo Terashima

Shigemi Maeda

Hiroshi Fuji

Kunio Kojima

Takeshi Yamaguchi

Akira Takahashi

Tetsuya Inui

Yoshikazu Fujii

Shozou Kobayashi

Masaru Nomura

Tsuneo Fujiwara

Hideyoshi Yamaoka

Takashi Iwaki

Junji Hirokane

Hirotsugu Matoba

Kazuo Van

Tomiyuki Numata

Noriaki Sakamoto

Shohichi Katoh

Michinobu Mieda

Toshihiro Yamanaka

Yoshiki Nishioka

Nobuyuki Horie

Takao Hyuga

Tetuya Inui

Yoshiteru Murakami

Junichi Washo

Masahiro Horii

Kentaroh Tsuji

Hisashi Minami

Tetsuo Fujiwara

Hiroyuki Katayama

Yoshihiro Sekimoto

Tomoyuki Miyake

Tohru Okuda

Mitsuo Ishii

Toshio Ishikawa

Daiji Yamane

Kentaro Tsuji

Shozo Kobayashi

Teruki Sugiura

Shigema Maeda

Yosikazu Fujii

Schohichi Katoh

Taeshi Yamaguchi

An optical memory element includes a guide track groove portion and address signal pit portion for indicating the address of the guide track groove. The address signal pit portion has a pit width narrower than the groove width of the guide track groove portion.

Optical memory apparatus

Magneto-optical memory element

A method is provided for manufacturing a magneto-optical memory element having guide grooves for storing information. The method includes applying a laser beam onto a resist film material located on a substrate to produce guide track grooves and address signal pits. Thereafter the resist film is developed. The remaining resist film is removed and a magnetic medium layer is deposited on the substrate.

Method for manufacturing a magneto-optical memory element

In an optical memory medium comprising prepits on which a light spot is impinged to obtain information and, if required, guide grooves: each of those among the prepits which are longer than the diameter of the light spot consists of a series of pit portions and unpitted portions; each of the prepits is sandwiched between two of the discontinuous portions of guide grooves adjacent to each other; the guide grooves have one or more narrow portions, and each of the prepits is sandwiched between two of the narrow portions of guide grooves adjacent to each other; or the guide grooves have one or more long portions, one or more short portions, and narrow portions formed between the long and short portions, and each of the prepits is sandwiched between two of the short portions of guide grooves adjacent to each other.

Optical memory medium with preformed pit arrangement

An optical memory disc medium contains a plurality of guide groove tracks. The guide groove tracks are arranged parallel to each other and they are used for controlling a position of a light beam. There is a land region between the guide groove tracks which is wider than the width of the guide groove tracks as measured in the disc-radial direction. Prepits for providing address information for the guide groove tracks are provided. The prepits are formed on the land regions and interposed between the lateral edges in the disc-radial direction of adjacent parallel guide groove tracks. Each prepit has a width which width is a narrower dimension than the width of each guide groove track as measured in the disc-radial direction.

Optical memory medium with predetermined guide tracks and prepits

A magneto-optical memory apparatus for enhancing the recording density of a magneto-optical recording medium, thereby to increase its recording capacity. The magneto-optical recording medium having recording marks, each having two ends in which information is recorded. The apparatus also includes an optical head arranged such that at the time of recording onto the magneto-optical recording medium, the recording marks are recorded such that the ends of each recording mark correspond to a second code of digital information composed of two different types of codes; at the time of reproduction, a light beam having a condensing spot is projected to the magneto-optical recording medium and, when a reproduction light containing reproduction information is entered to the optical head from the magneto-optical recording medium, a reproduction signal is supplied; and when the light beam is projected to a recording mark, an information pulse corresponding to the second code is generated in the reproduction signal, only when the reproduction light from the recording mark interferes with the reproduction light from the non-marking part; and a signal detector circuit for detecting the information pulse in the reproduction signal obtained from the optical head and for converting the reproduction signal into a digital reproduction signal.

Magneto-optical memory apparatus utilizing edges or recording mark to

A method for manufacturing an optical memory element including the steps of disposing a resist film on a substrate, placing a photo-mask carrying a guide groove pattern on the resist film so as to position the photo-mask over a predetermined position of the substrate, forming a guide groove pattern latent image on the resist film, developing the guide groove pattern latent image formed on the resist film, conducting an etching operation through the developed guide groove pattern as to form guide grooves in the substrate, removing the resist film from the substrate, and disposing a recording medium layer on the substrate having the guide grooves formed therein.

Optical memory element and manufacturing method thereof

A recording and reproducing device, which records and reproduces information on and from a rewritable recording medium having absolute addresses and including an information recording area wherein information entered from external devices is recorded and a Table of Contents area wherein additional address information with respect to the information recorded in the information recording area is recorded. The TOC area contains the absolute addresses of the recording positions of each information recorded in the information recording area. A display section graphically and independently displays the recorded and unrecorded ranges of the information recording area according to the absolute addresses recorded in the TOC area with respect to the recording positions of each piece of information. A warning device alerts the user that a position on the disc is occupied by referring TOC area when it is instructed to record new information in the position of the information recording area where another information has already been recorded.

Method and device for data management in optical recording medium

A disk recording and reproducing device records and reproduces information on and from a magneto-optical disk having 3 3 and there is TOC (Table of Contents) area. Additional information with respect to each piece of the information recorded in the information recording area is recorded in the TOC. The device includes operation keys, a TOC memory for storing read/write control information for desired pieces of information entered through the operation keys. There is an optical head and a magnetic coil for recording, in the TOC area, the contents stored in the TOC memory as additional information. A controller controls the read/write operation to the disk according to the read/write control information. With the arrangement, a user can recognize necessary/unnecessary information and defective parts in the disk, and therefore make effective use thereof as well as maintaining secrecy of the information.

Disk recording and reproducing device

A tracking system for positioning a light spot onto a magneto optic or optical disc having a beam guide track preformatted thereon comprises a main light beam and two auxiliary light beams, and a circuit for subtracting a low frequency component of a difference between the tracking error signals, detected by the respective auxiliary light beams and the main light beam, from a tracking error signal detected by the main light beam.

Tracking system for optical disc memory using tracking error signals

An information recording and reproducing device records, erases and reproduces information on and from a memory device. The memory device has pre-format sections. The information recording and reproducing device includes a pre-recorded area detection circuit for detecting a pre-recorded area having information predeterminately recorded and located on the memory device and timing control circuits for providing timing control of an information recording, erasing or reproducing operation according to a pre-recorded area detecting signal released from the pre-recorded area detection circuit, thereby enabling each timing of recording, reproducing, or erasing operation is accurately determined. The timing control may be performed according to both of the pre-recorded area detecting signal of the present invention and the conventional synchronization detection signal. In that case, if an error should occur in the synchronization detection signals, since the pre-recorded area detecting signal is released every time pre-recorded information for a sector mark or the like is reproduced, an accurate timing control without time lag is achieved according to the pre-recorded area detecting signals.

Information recording and reproducing device

An information recording and reproducing device having an automatic gain control device wherein its amplification degree is adjusted according to an AGC voltage varying with an amplitude of a reproduced signal. The automatic gain control device has a holding circuit which holds the AGC voltage in each of recording and erasing operations, and also holds the AGC voltage in reproducing an un-recorded area of information. The AGC voltage is also used for determining an optimum recording condition for a recording medium. Instead of the holding circuit, by installing a limiter circuit for limiting an amplitude of a reproduced signal, and by the use of transient response of the reproduced signal due to an coupling situated before the limiter circuit, an appropriate amplification degree can also be obtained in the automatic gain control device. Further, the limiter circuit which is disposed at a stage before a reproduction circuit and also before a capacitor having the ac coupling, may restrain influence of the transient response of the ac coupling given on the reproduced signal, thereby making it possible to reproduce a signal with small amplitude immediately after recording or erasing operation.

Information recording and reproducing device with reproduction and

An optical memory device comprising a substrate and guide tracks having a depth of .lambda./8n or less formed on said substrate, wherein .lambda. is the wavelength of laser light used for the optical memory device, and n is the refraction index of the guide track portion of the substrate.

Optical memory device having guide tracks shaped for increasing the

In the optical recording element of the invention, alignments of long thin pits inclined in various directions with respect to the track direction are formed on the tracks and information is recorded therein according to the different inclines of the pits, thereby performing higher-density and larger-volume recording without reducing the spacing between each pit and the track pitch. The invention also discloses an optical data retrieval system for use with the above optical recording element, which scans the pit alignments with a laser beam spot, detects the inclines of the pits by obtaining the distribution of the intensity of reflected light which is caused by light diffraction at the pits, and plays back information in accordance with the inclines. Therefore, not only can the substantially same structure as that of a standard type optical data retrieval system be applied to the invention without making any complicated change, but also cross-talk is less likely to be produced in the read out signals.

Optical retrieval system for encoding pit angular data and optical

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Nara, Japan

Toshihisa Deguchi