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EP0516906A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

An optical disc and pickup apparatus therefor

Assignee: Pioneer Corp
•
Filing: 1991-11-08
•
Granted: —
•
Expires: 2011-11-08
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Abstract

Abstract An optical disc has a two-step pit structure in which first pits (6) and second pits (7) whose depth ( lambda 1/8) is half that ( lambda 1/4) of the first pits are arranged in superposition in the same track direction. A first laser diode (11) emits first laser light having a first wavelength ( lambda 1) which is four times the depth of the first pits, and a second laser diode (12) emits second laser light having a second wavelength ( lambda 2) which is four times the depth of the second pits. An optical system (14-18) introduces the first and second laser light beams onto a recording surface (17) of the optical disc and also introduces reflected light to a detector (19). A selecting drive mechanism (13,20) may be provided to select one of the first and second laser diodes as a light source for actually emitting light to be introduced onto the recording surface. <IMAGE>

Inventors

  • 👤 Minoru c/o Pioneer Electronic Corp. Hanaoka

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-09 06:07
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/24; G11B7/2407; G11B7/24085; G11B7/12; G11B7/125; G11B7/126

Claims Analysis

Total Claims: 5
Claim 1
Independent Claim 46 words
An optical disc (10) comprising: a plurality of first pits (6) arranged in a track direction and having a first depth (λ₁/4); and a plurality of second pits (7) arranged in the track direction and having a second depth (λ₁/8) which is half the first depth.
Claim 2
Dependent Claim 20 words
An optical disc according to claim 1, wherein the first and second pluralities of pits represent different sets of information.
Claim 3
Dependent Claim 125 words
A pickup apparatus for reading out information recorded on an optical disc (10) according to claim 1, the apparatus comprising: means (11) for emitting a first coherent light beam having a first wavelength (λ₁) which is four times the depth of the first pits; means (12) for emitting a second coherent light beam having a second wavelength (λ₂) which is four times the depth of the second pits; means (14-18) for introducing the first and second coherent light beams onto a recording surface (17) of the optical disc and for introducing at least respective parts of the first and second light beams reflected by the recording surface into means (19) for detecting quantities of the respective parts of the reflected first and second light beams.
Claim 4
Dependent Claim 38 words
Apparatus according to claim 3, further comprising means (13,20) for selecting one of the first and second coherent light beam emitting means as a light source emitting a light beam to be introduced onto the recording surface (17).
Claim 5
Dependent Claim 42 words
Apparatus according to claim 3 or claim 4, further comprising means for separating the respective parts of the reflected first and second light beams, wherein the detecting means detects the respective parts of the first and second light beams individually and simultaneously.

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