Sharp Kabushiki Kaisha Corporation

Panasonic Corporation

Tdk Corporation

Memory-tech Corporation

Hiroaki Ashiwa

Hideharu Tajima

Isamu Kuribayashi

Atsushi Etoh

Masahito Konishi

Takaaki Kassai

Keiji Fujita

Kenji Maebara

Ryo Kojima

Takeshi Omori

An optical information recording medium () includes on a substrate (), a ROM layer (), a RE layer (), an intermediate layer () separating the ROM layer () and the RE layer (), and a light transmitting layer () provided farthest from the substrate (). The RE layer () is an information recording layer provided most farthest from the light transmitting layer (), and is a recording layer of BCA recorded in a format easily determinable as compared to an information recording format used in the ROM layer (), and antifouling property of a surface of the light transmitting layer () is set based on the RE layer (). This makes it easy for the recording and reproducing apparatus to confirm a disc type, allows for sharing one recording and reproducing apparatus with other types of optical discs, and simplifies the disc production. Furthermore, an optical information recording medium is accomplished, in which outdated data on the ROM layer is replaced by recording, on the RE layer, updated data obtained while Internet connection can be established.

Optical information recording medium

In a focus optical system for optical discs or optical disc master exposure apparatuses, a relative positional relation between a cylindrical lens and a 4-division detector in an astigmatic optical system is adjust so that an interference fringe appearing in reflected light derived from an optical disc master is made to be incident on a dead zone of the 4-division detector. Thus, an astigmatic focus servo free from effects of variations in a focus error signal due to the interference fringe is realized. As a result of this, effects of the interference fringe appearing in the reflected light derived from an optical disc or optical disc master can be suppressed.

Focus optical system and optical disc master exposure apparatus

Growing community of inventors

Ibaraki, Japan

Hiroaki Ashiwa