Optical head device and optical disc device

Abstract

In an optical head device and an optical disc device, which make it possible to reduce an influence of a differential push-pull signal by stray light without making the structure complicated, reflective light of zero-order diffracted light by other information recording surfaces than an access subject information recording surface, reflective light of + first-order diffracted light by other information recording surfaces than an access subject information recording surface, and reflective light of - first order-order diffracted light by other information recording surfaces than an access subject information recording surface form an interference fringe on an optical detector (9). If a length in a y-direction of one period of the interference fringe is Ty, a positive integer is N1, and lengths in the y-direction of divided receiving elements (9e, 9f, 9g, 9h) are Uy, respectively, then they satisfy the following: Uy=Ty x N1. Further, if a positive integer is N2, a distance from the center of a main beam light receiving unit (9M) to the divided receiving elements (9e, 9f, 9g, 9h) and a distance from the center of the main beam light receiving unit (9M) to a dividing line of the divided receiving elements (9g, 9h) are Vy, then they satisfy the following: Vy = (Ty / 2) x {N2 - (1 / 2)}.

Description

technical field [0001] The present invention relates to an optical head device for irradiating laser light onto a multilayer optical disc having a plurality of information recording surfaces and detecting the reflected light, and an optical disc device having the optical head device. Background technique [0002] In optical discs 10 such as CD (Compact Disc), DVD (Digital Versatile Disc: Digital Versatile Disc), and BD (Blu-ray Disc: Blu-ray Disc), there are reproduction-only optical discs and record-once or rewritable discs. disc, such as figure 1 As shown, the reproduction-only optical disc is formed with an arrangement of spiral pits TB with a track pitch of TP on the information recording surface, that is, a recording track TR, as figure 2 As shown, a write-once or rewritable optical disc has a spiral recording track TR on which a recording mark TM is written with a track pitch of TP formed on the information recording surface. [0003] The optical disc device include...

AI Technical Summary

Problems solved by technology

However, there is a problem that the structure of the optical head device is complicated by adding a photosensitive element and an arithmetic circuit for such countermeasures.

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