Patent Number: 7,821,884

Title: Information recording and retrieval method, and its apparatus

Abstract: Provided is a recording and retrieval apparatus for a multi-layer optical disk. A multi-layer optical disk in which a plurality of recording layers and a single servo layer are combined to form a set is used. A spot for the servo layer and a spot for the recording layers are turned on in a time-sharing manner. Servo signal detection areas are formed discretely in the servo layer. The servo signal detection areas and data recording areas are provided so as not to overlap each other when viewed from the spot incident side. Thus, separation of data from each of the layers can be done by even a single photodetector without interference.

Inventors: Maeda; Takeshi (Koganei, JP), Shimano; Takeshi (Yokohama, JP), Hirotsune; Akemi (Saitama, JP), Miyamoto; Harukazu (Higashimurayama, JP)

Assignee: Hitachi, Ltd.

International Classification: G11B 7/00 (20060101)

Expiration Date: 2018-10-26 0:00:00