EP0258450A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Device for detecting focus
Assignee: Sony Corp
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Filing: 1987-02-18
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Granted: —
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Expires: 2007-02-18
Abstract
Abstract Device for detecting a focus (1) which detects a state of focusing of an optical recording medium, wherein, in order that said device for detecting a focus (1) has a small size and is inexpensive, detection of a focus employing two photodetectors (33), (34) respectively located before and behind the point of convergence of beams (45) from the optical recording medium is made possible by means of a single prism (37), further, a plurality of optical parts (31), (33), (34), and (37) being formed into one body, moreover, mounting these optical parts (31), (33), (34), (37) on a single plane of a semiconductor substrate (32) being made possible, therefore, said device (1) can be applicable to an optical head which particularly requires a small size, light weight, low cost, and high performance.
Inventors
- 👤 You Sony Corporation Yoshitoshi
- 👤 Yoshiyuki Sony Corporation Matsumoto
- 👤 Hidehiro Sony Corporation Kume
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 09:09
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/08; G11B7/09; G11B7/12; G11B7/135; G11B7/1356; G11B7/0908; G11B7/0912; G11B7/123; G11B7/13; G11B7/131; G11B7/0925
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
266 words
A focusing detection apparatus comprising: a semiconductor laser fixed on a semiconductor substrate: a prism fixed on said semiconductor substrate; a first semi-transmissible reflecting surface formed on a prism surface opposite to said semiconductor laser; a second semi-transmissible reflecting surface constituted by a prism surface in contact with said semiconductor substrate and formed at a position where a beam passing through said first semi-transmissible reflecting surface is incident; a first photosensor including three photosensor elements formed on said semiconductor substrate at a position in contact with said first semi-transmissible reflecting surface and aligned in a predetermined direction; and a second photosensor including three photosensor elements aligned in a predetermined direction and formed on said semiconductor substrate at a position where the beam reflected by said second semi-transmissible reflecting surface is incident, wherein the optical recording medium is irradiated with the beam emitted from said semiconductor laser and reflected by said first semi-transmissible reflecting surface, a beam from the optical recording medium passed through said first semi-transmissible reflecting surface is converged after the beam is reflected by said second semi-transmissible reflecting surface but before the beam is incident on said second photosensor, and a sum of detection signals from end photosensor elements of said three photosensor elements of said first photosensor and a central photosensor element of said three photosensor elements of said second photosensor is compared with that from a central photosensor element of said three photosensor elefents of said first photosensor and end photosensor elements of said three photosensor elements of said second photosensor to produce a focusing error signal for the optical recording medium.
Claim 2
Dependent Claim
266 words
A focusing detection apparatus comprising: a semiconductor laser fixed on a semiconductor substrate: a prism fixed on said semiconductor substrate; a first semi-transmissible reflecting surface formed on a prism surface opposite to said semiconductor laser; a second semi-transmissible reflecting surface constituted by a prism surface in contact with said semiconductor substrate and formed at a position where a beam passing through said first semi-transmissible reflecting surface is incident; a first photosensor including three photosensor elements formed on said semiconductor substrate at a position in contact with said first semi-transmissible reflecting surface and aligned in a predetermined direction; and a second photosensor including three photosensor elements aligned in a predetermined direction and formed on said semiconductor substrate at a position where the beam reflected by said second semi-transmissible reflecting surface is incident, wherein the optical recording medium is irradiated with the beam emitted from said semiconductor laser and reflected by said first semi-transmissible reflecting surface, a beam from the optical recording medium passed through said first semi-transmissible reflecting surface is converged after the beam is reflected by said second semi-transmissible reflecting surface but before the beam is incident on said second photosensor, and a sum of detection signals from end photosensor elements of said three photosensor elements of said first photosensor and a central photosensor element of said three photosensor elements of said second photosensor is compared with that from a central photosensor element of said three photosensor elefents of said first photosensor and end photosensor elements of said three photosensor elements of said second photosensor to produce a focusing error signal for the optical recording medium.
Claim 3
Dependent Claim
43 words
An apparatus according to claim 1, characterized in that the predetermined direction along which said three photosensor elements of said first photosensor are aligned is the same as the predetermined direction along which said three photosensor elements of said second photosensor are aligned.
Claim 4
Dependent Claim
30 words
An apparatus according to claim 2, characterized in that said three photosensor elements of said first photosensor are respectively arranged adjacent to said three photosensor elements of said second photosensor.
Claim 5
Independent Claim
23 words
An apparatus according to any one of claims 1 to 3, characterized in that said focusing detection apparatus is sealed in a cap.
Claim 6
Independent Claim
30 words
An apparatus according to any one of claims 1 to 3, characterized in that said focusing detection apparatus is sealed in a holding member for holding an objective lens therein.
Claim 7
Dependent Claim
30 words
An apparatus according to claim 5, characterized in that said objective lens held in said holding means and a cover mounted on said holding member seal said focusing detection apparatus.
Claim 8
Dependent Claim
16 words
An apparatus according to claim 6, characterized in that a mirror is mounted on said cover.
Claim 9
Dependent Claim
27 words
An apparatus according to claim 7, characterized in that said mirror is inclined at a predetermined angle with respect to an optical axis of said objective lens.
Claim 10
Dependent Claim
18 words
An apparatus according to claim 5, characterized in that said holding member is movable along a focusing direction.
Claim 11
Dependent Claim
20 words
An apparatus according to claim 5 or 9, characterized in that said holding member is movable along a tracking direction.
References Cited (Backward Citations)
No citation records indexed.
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