Optical device and optical pickup device

Abstract

There is provided an optical device for receiving an incident light on the light reception surfaces (20A-29) on the light reception element by diffracting the incident light by a hologram element. The optical device receives a reflection light of sub beam used for tracking operation on the different light reception surfaces depending on the wavelength. When an incident light of one wavelength is received on one light reception surface (22, 23, 26, 27), calculation is performed according to the output signal from the one light reception surface and the output signal from other light reception surface (24, 25, 28, 29) so as to detect an unnecessary light component. Thus, when recording and / or reproducing an information signal onto / from an optical disc using a light source of a different wavelength such as 'DVD' and 'CD', it is possible to eliminate the affect by an unnecessary reflection light from the optical disc and eliminate calculation complexity about the output signal.

Description

technical field [0001] The present invention relates to an optical device of an optical pickup device used for recording and reproducing an information recording medium such as an optical disk, and to an optical pickup device constructed using such an optical device. Background technique [0002] Conventionally, various optical discs have been proposed as information recording media. As such an optical disc, a "DVD" (Digital Versatile Disc) standard optical disc having about seven times the recording capacity of a "CD" (compact disc) standard optical disc has rapidly spread in recent years. "DVD-Video" in which video signals are recorded on this "DVD" can be reproduced in large quantities, and will replace videotape media such as "VHS" (trade name) as a medium for distribution and rental of contents such as movies. [0003] In addition, the so-called "DVD-RAM", "DVD-R", "DVD-RW", "+R", "+RW" and other optical disc standards that users can record information signals are also...

AI Technical Summary

Problems solved by technology

However, when the area of ​​the light-receiving region is enlarged, the amount of receiving the above-mentioned unnecessary reflected light increases approximately in proportion to the enlargement of the area. dynamic range of

[0016] Here, in order to avoid this problem, it is considered to separate the light-receiving area for each wavelength. However, only by separating the light-receiving area, although the unnecessary light component can be halved, there is a problem that it cannot be completely removed.

[0017] In addition, for example, in an optical pickup device provided with a light-receiving part for canceling offset as described in Japanese Patent Application Laid-Open No. 11-73658, it is necessary to increase the area of ​​the hologram element only for so-called offset canceling. Divide and light-receiving area and use dedicated calculation circuit, so there is a problem of cost increase due to complicated structure and difficult manufacturing

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