EP0198655A2
Expired / Lapsed
EP
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Optical heads
Assignee: Sony Corp
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Filing: 1986-04-08
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Granted: —
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Expires: 2006-04-08
Abstract
Abstract An optical head (21) includes a plate-like half mirror (22) for reflecting a beam (6) from a light source (5), via a collimator lens (7) and an objective lens (8), onto an optical recording medium ( 11 ). The beam is reflected from the medium (11), via the lenses (7, 8) onto the half mirror (22). The half mirror (22) serves as a beam splitter, enabling the beam to pass therethrough to reach a photodetector (12), and functions also to produce astigmatism for detecting a focusing error. An optical element (23) is disposed between the half mirror (22) and the photodetector (12) for correcting a coma produced by passage af the beam through the half mirror.
Inventors
- 👤 Akira C/O Sony Corporation Nakamura
- 👤 Hiroshi C/O Sony Corporation Oinoue
- 👤 Tomoyuki C/O Sony Corporation Ishida
- 👤 Kenji C/O Sony Corporation Shintani
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 19:53
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/135; G11B7/1362; G11B7/1365; G11B7/08; G11B7/09; G11B7/0908; G11B7/0909; G11B7/1381; G11B7/1392
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
139 words
An optical head (21;31) comprising: a collimator lens (7); an objective lens (8); a photodetector (12); and a plate-like half mirror (22) arranged to reflect a beam (6) from a light source (5) onto the collimator lens (7) so that the beam becomes incident on an optical recording medium (11) through the collimator lens (7) and the objective lens (8) and returns through the objective lens (8), the collimator lens (7) and the half-mirror (22) to be incident on the photodetector (12), the passage of the returned beam through the half-mirror (22) producing astigmatism; characterised by an optical element (23;32) for correcting a coma, the optical element (23;32) being so disposed that the returned beam, after passing through the half mirror (22), is incident on the photodetector (12) through the optical element (23;32) so as to eliminate coma therefrom.
Claim 2
Dependent Claim
139 words
An optical head (21;31) comprising: a collimator lens (7); an objective lens (8); a photodetector (12); and a plate-like half mirror (22) arranged to reflect a beam (6) from a light source (5) onto the collimator lens (7) so that the beam becomes incident on an optical recording medium (11) through the collimator lens (7) and the objective lens (8) and returns through the objective lens (8), the collimator lens (7) and the half-mirror (22) to be incident on the photodetector (12), the passage of the returned beam through the half-mirror (22) producing astigmatism; characterised by an optical element (23;32) for correcting a coma, the optical element (23;32) being so disposed that the returned beam, after passing through the half mirror (22), is incident on the photodetector (12) through the optical element (23;32) so as to eliminate coma therefrom.
Claim 3
Dependent Claim
25 words
An optical head according to claim 1, wherein the half mirror (22) and the optical element (23;32) are arranged in planes that intersect each other.
Claim 4
Dependent Claim
44 words
An optical head according to claim 2, wherein the optical element (23;32) causes an optical axis of the beam between the optical element and the photodetector (12) to coincide substantially with the optical axis between the recording medium (11) and the half mirror (22).
Claim 5
Dependent Claim
58 words
An optical head according to claim 1, claim 2 or claim 3, wherein the optical element (32) has a first surface (34) operative to transmit the beam incident on the optical element therethrough, and a second surface (35) which is parallel to the first surface (34) and is operative to reflect the beam transmitted through the first surface.
Claim 6
Dependent Claim
43 words
An optical head according to claim 4, wherein a material of the optical element (32) is the same as a material of the half mirror (22), and a thickness of the optical element (32) is half the thickness of the half mirror (22).
Claim 7
Dependent Claim
32 words
An optical head according to claim 1, claim 2 or claim 3, wherein the optical element (23) and the half mirror (22) are of the same material and of the same thickness.
References Cited (Backward Citations)
No citation records indexed.
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