EP0109194A1
Expired / Lapsed
EP
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Optical information reproducing apparatus
Assignee: Mitsubishi Electric Corp
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Filing: 1983-10-14
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Granted: —
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Expires: 2003-10-14
Abstract
Abstract An optical information reproducing apparatus for optically reproducing a signal recorded on a disc which comprises a light source (1) of a semiconductor laser having a single longitudinal mode characteristic, a recording disc (8) having an information track of an optically readable structure, a collimating lens (2) for condensing a linearly polarized light beam from the light source to apply the same to the recording disc, an objective lens (7) for condensing the reflected light beam, a polarization beam splitter (4) for separating the reflected light beam, a light detector (11) for detecting the separated light beam, and a feed back means such as a phase plate (5) involving a wavelength deviation by a predetermined amount from the 1/4 wavelength, or a 1/4 wavelength phase plate disposed to be inclined by more than a predetermined angle about the light axis of the light source, or the like, for feeding back a portion of the reflected light beam exceeding a predetermined amount to the light source.
Inventors
- 👤 Kazuo C/O Mitsubishi Denki K.K. Okada
- 👤 Shinsuke C/O Mitsubishi Denki K.K. Shikama
- 👤 Nobumasa C/O Mitsubishi Denki K.K. Egashira
- 👤 Akira c/o Mitsubishi Denki K.K. Hashimoto
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 17:14
CPC Classifications
H; H01; H01S; H01S5/00; H01S5/10; H01S5/14; G; G11; G11B; G11B7/00; G11B7/12; G11B7/125; G11B7/135; G11B7/1365
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
86 words
Optical information reproducing apparatus comprising: a light source (1), means (6,7) for directing light from the source to a recording medium and for receiving light reflected from the recording medium, means (4,5,25) for separating reflected light from the light transmitted from the light source, and means (11) responsive to the reflected light which is separated for generating an output signal, characterised in that the separating means are adapted to feed back to the light source a or at least a predetermined quantity of the reflected light.
Claim 2
Dependent Claim
86 words
Optical information reproducing apparatus comprising: a light source (1), means (6,7) for directing light from the source to a recording medium and for receiving light reflected from the recording medium, means (4,5,25) for separating reflected light from the light transmitted from the light source, and means (11) responsive to the reflected light which is separated for generating an output signal, characterised in that the separating means are adapted to feed back to the light source a or at least a predetermined quantity of the reflected light.
Claim 3
Dependent Claim
138 words
Optical information reproducing apparatus, comprising: a light source (1) including a semiconductor laser of a longitudinal single mode characteristic, a condensing lens (7) for condensing and directing a laser beam from said light source to a recording disc (8) having an information track structured to be capable of optical reading and for condensing a light beam reflected from said recording disc, means (4,5,25) for separating said reflected light beam condensed by said lens from the light path of said laser beam transmitted from said light source to said lens, and a photodetector (11) for detecting said reflected light beam separated by said separating and feeding back means for providing a reproduced signal, characterised in that said separating means are adapted for feeding back a portion of said reflected light beam exceeding a predetermined amount to said light source.
Claim 4
Dependent Claim
138 words
Optical information reproducing apparatus, comprising: a light source (1) including a semiconductor laser of a longitudinal single mode characteristic, a condensing lens (7) for condensing and directing a laser beam from said light source to a recording disc (8) having an information track structured to be capable of optical reading and for condensing a light beam reflected from said recording disc, means (4,5,25) for separating said reflected light beam condensed by said lens from the light path of said laser beam transmitted from said light source to said lens, and a photodetector (11) for detecting said reflected light beam separated by said separating and feeding back means for providing a reproduced signal, characterised in that said separating means are adapted for feeding back a portion of said reflected light beam exceeding a predetermined amount to said light source.
Claim 5
Dependent Claim
37 words
Apparatus in accordance with Claim 1 or 2, characterised in that said separating and feeding back means is adapted to feedback said reflected light beam to said light source at a feedback ratio of 3% to 40%.
Claim 6
Dependent Claim
37 words
Apparatus in accordance with claim 1, 2 or 3, characterised in that said separating and feeding back means is adapted to feed back said reflected light beam to said light source at a feedback ratio of 15%.
Claim 7
Dependent Claim
56 words
Apparatus in accordance with any preceding claim, characterised in that said separating and feeding back means comprises in combination a polarization beam splitter (4), and a phase plate (5) involving a wavelength deviation by a predetermined amount from the 1/4 wavelength for feeding back a predetermined amount of said reflected light beam to said light source.
Claim 8
Dependent Claim
18 words
Apparatus in accordance with claim 5, characterised in that said phase plate comprises a 0.19 wavelength phase plate.
Claim 9
Dependent Claim
18 words
Apparatus in accordance with claim 5, characterised in that said phase plate comprises a 0.31 wavelength phase plate.
Claim 10
Dependent Claim
79 words
Apparatus in accordance with any of claims 1 to 4, characterised in that said separating and feeding back means comprises in combination a polarization beam splitter (4), and a 1/4 wavelength phase plate (25) disposed to be inclined by more than a predetermined angle about the light axis of said light source with respect to a linearly polarized light beam from said light source for feeding back a predetermined amount of said reflected light beam to said light source.
Claim 11
Dependent Claim
26 words
Apparatus in accordance with claim 8, characterised in that said 1/4 wavelength phase plate is disposed to be inclined at the angle of (45 ± 11)°.
Claim 12
Dependent Claim
73 words
Apparatus in accordance with any of claims 1 to 4, characterised in that said separating and feeding back means comprises in combination a polarization beam splitter, and a phase plate involving a phase deviation by a predetermined amount from the 1/4 wavelength and disposed to be inclined at more than a predetermined angle about the light axis of said light source with respect to a lenearly polarized light beam from said light source.
Claim 13
Dependent Claim
39 words
Apparatus in accordance with any of claims 1 to 4, characterised in that said separating and feeding back means comprises in combination a polarization beam splitter, 1/4 wavelength phase plate, and an additional phase plate of a predetermined wavelength.
References Cited (Backward Citations)
DE3027318A1
Cited
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