EP0147749A2
Expired / Lapsed
EP
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Optical head
Assignee: Hitachi Ltd
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Filing: 1984-12-14
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Granted: —
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Expires: 2004-12-14
Abstract
Abstract This invention is characterized in that a modified polarization prism (2) or a modified half prism (8) is used therein. Since photodetectors (6-1, 6-2) serving at the same time for light signal detection, for automatic focussing and for tracking are disposed at both the sides of said optical source (1) of a semiconductor laser, a single axis optical system can be realized and it is possible to reduce the optical head in size.
Inventors
- 👤 Kimio Tatsuno
- 👤 Keiji Kataoka
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 04:21
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/135; G11B7/1381; G11B7/08; G11B7/123; G11B7/1356
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
88 words
An optical head comprising: an optical source of a semiconductor laser (1); an optical system (4) collecting a laser beam emitted by said optical source (1) focussing a spot on a recording medium (10); photodetectors (6-1, 6-2) disposed at both the sides of said optical source (1); and a beam dividing element (2 or 8) disposed between said optical source (1) and said optical system (4) and dividing light reflected by said recording medium (10) into two so as to lead them to said photodetectors (6-l, 6-2), respectively.
Claim 2
Dependent Claim
88 words
An optical head comprising: an optical source of a semiconductor laser (1); an optical system (4) collecting a laser beam emitted by said optical source (1) focussing a spot on a recording medium (10); photodetectors (6-1, 6-2) disposed at both the sides of said optical source (1); and a beam dividing element (2 or 8) disposed between said optical source (1) and said optical system (4) and dividing light reflected by said recording medium (10) into two so as to lead them to said photodetectors (6-l, 6-2), respectively.
Claim 3
Dependent Claim
44 words
An optical head according to Claim 1, wherein said beam dividing element is a half prism (8) having reflecting surfaces (7) disposed symmetrically with respect to a plane including the optical axis, of which surfaces are comprised in a region near said optical axis.
Claim 4
Dependent Claim
62 words
An optical head according to Claim 1, wherein a 1/4 wave plate (3) is disposed between said beam dividing element and said optical system (4) and said beam dividing element is a polarization prism (2), having reflecting surfaces (5) disposed symmetrically with respect to a plane including the optical axis, of which surfaces are comprised in a region near said optical axis.
Claim 5
Dependent Claim
16 words
An optical head according to Claim 1, wherein said optical system (4) comprises an aspheric lens.
Claim 6
Dependent Claim
16 words
An optical head according to Claim 1, wherein said optical system (4) comprises a GRIN lens.
Claim 7
Dependent Claim
16 words
An optical head according to Claim 1, wherein said optical system (4) comprises a hologram lens.
Claim 8
Dependent Claim
40 words
An optical head according to Claim 1, wherein each of the photodetectors (6-1, 6-2) disposed at both the sides of said optical source (1) comprises 2 photosensitive elements (D 1 , D 2 and D 3 , D 4 ).
Claim 9
Dependent Claim
26 words
An optical head according to Claim 1, wherein the photodetectors (6-1, 6-2) are formed in hybrid or in monolithic manner together with said semiconductor laser (1).
References Cited (Backward Citations)
No citation records indexed.
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