Hitachi, Ltd.

Kazuo Isaka

Takuya Mizokami

Takeshi Maeda

Atsushi Saito

Shinichi Arai

Satoshi Kawamura

Hisataka Sugiyama

Kazuo Shigematsu

Masahiro Takasago

Osami Kushizaki

Histaka Sugiyama

An information recording/reproducing method is disclosed for an information recording/reproducing apparatus including a recording medium having a disk-like shape, a unit for rotating the recording medium at a constant angular velocity, a unit for recording code information so that the bit length of the code information becomes approximately constant with respect to a radial position on the recording medium, a unit for modulating the code information to be recorded to form a modulated signal, and a recording unit for forming in the recording medium a localized recording region having a different physical property with respect to an unrecorded region, the recording unit being controlled by the modulated signal so that the code information is recorded to correspond to the edge of the recording region, wherein the bit rate of the code information to be recorded changes depending on a location on the recording medium, and a part of each of a recording characteristic of the apparatus and a reproducing characteristic of the apparatus is changed in accordance with a location on the recording medium.

Optical recording method employing pit edge recording on recording

Optical information recording/reproducing apparatus using pit edge

In an optical disk apparatus for recording and reproducing data using light beams, the light reflected from a record mark area provided on an optical disk is detected and the amplitude of the signal corresponding to the light is held; the record mark is composed of long pits and long unrecorded areas. This amplitude is compared with that of the signal relative to the light from a data recording area of the optical disk. If the comparison result has a predetermined relation between both signals, an output signal with a prescribed level is produced. This output signal is used to assure the quality of the recorded data.

Optical recording and reproducing apparatus

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

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Odawara, Japan

Kazuo Isaka