EP0070552A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Optical head
Assignee: Toshiba Corp
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Filing: 1982-07-19
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Granted: —
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Expires: 2002-07-19
Abstract
Abstract An optical head of the present invention is provided with an optical system including an objective lens, and a photodetector. A laser beam incident on the objective lens is converged thereby and projected on a light-reflecting layer. The laser beam reflected by the light-reflecting layer is transferred to a light receiving surface (66) of the photodetector through the optical system including the objective lens. The light receiving surface (66) includes two photosensitive regions (60-1, 60-2) and a photoinsensitive region (64) arranged between the two photosensitive regions (60-1, 60-2) and detecting no substantial light rays. While the objective lens is kept in the just focusing state, most of light rays are projected on the photoinsensitive region (64), and low level current is generated from the photodetector. if the objective lens is in the defocusing state, the laser beam is projected toward one of the photosensitive regions (60-1, 60-2), and a high level current is generated from the photodetector.
Inventors
- 👤 Hideo Ando
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 12:19
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/13; G11B7/131; G11B7/08; G11B7/09; G11B7/0908; G11B7/0909; G11B7/0916; G11B7/135; G11B7/1359; G11B7/1381
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
212 words
A system for focusing a light beam on a light reflecting surface (14), comprising: an objective lens (42) for converging the light beam, whereby a beam spot corresponding to the beam waist of the converged light beam is formed on the light reflecting surface (14) when the objective lens (42) is in the just focusing state, and whereby a beam spot of a larger size than that of the beam waist is formed on the light reflecting surface when the objective lens (42) is in the defocusing state; characterized by further comprising: a photodetector (48) having a light receiving surface (66) including at least two photosensitive regions (60-1, 60-2) and a photoinsensitive region (64) arranged between the two photosensitive regions (60-1, 60-2) and detecting no substantial light rays; and means (52, 54, 110, 118, 120, 123) for transferring a light beam reflected from the light reflecting surface (14) and directing the light beam toward the light receiving surface (66) of the photodetector (48), whereby the light beam is projected toward the photoinsensitive region (64) when the objective lens (42) is in the just focusing state, and whereby the light beam is projected toward at least one of the photosensitive regions (60-1, 60-2) when the objective lens (42) is in the defocusing state.
Claim 2
Independent Claim
212 words
A system for focusing a light beam on a light reflecting surface (14), comprising: an objective lens (42) for converging the light beam, whereby a beam spot corresponding to the beam waist of the converged light beam is formed on the light reflecting surface (14) when the objective lens (42) is in the just focusing state, and whereby a beam spot of a larger size than that of the beam waist is formed on the light reflecting surface when the objective lens (42) is in the defocusing state; characterized by further comprising: a photodetector (48) having a light receiving surface (66) including at least two photosensitive regions (60-1, 60-2) and a photoinsensitive region (64) arranged between the two photosensitive regions (60-1, 60-2) and detecting no substantial light rays; and means (52, 54, 110, 118, 120, 123) for transferring a light beam reflected from the light reflecting surface (14) and directing the light beam toward the light receiving surface (66) of the photodetector (48), whereby the light beam is projected toward the photoinsensitive region (64) when the objective lens (42) is in the just focusing state, and whereby the light beam is projected toward at least one of the photosensitive regions (60-1, 60-2) when the objective lens (42) is in the defocusing state.
Claim 3
Dependent Claim
22 words
The system according to claim 1, characterized in that said photoinsensitive region (64) is a light-shielding layer (70) to shield light rays.
Claim 4
Dependent Claim
17 words
The system according to claim 2, characterized in that said light-shielding layer (70) is an alumina layer.
Claim 5
Dependent Claim
31 words
The system according to claim 1, characterized in that said photodetector (48) is a semiconductor photodetector, and said photoinsensitive region (64) is a recess region (78) formed in the semiconductor photodetector.
Claim 6
Dependent Claim
48 words
The system according to claim 1, characterized in that said photodetector (48) is formed on a semiconductor substrate, and said photoinsensitive region (64) is an impurity region (80) of the same conductivity type as the substrate (68) having a higher impurity density than that of the substrate (68).
Claim 7
Dependent Claim
28 words
The system according to claim 1, characterized in that the width of said photoinsensitive region (64) is a quarter or more of the diameter of the beam spot
Claim 8
Dependent Claim
19 words
(82) formed on the light receiving surface (66) by the projection of the light beam when the objective lens
Claim 9
Dependent Claim
19 words
(82) formed on the light receiving surface (66) by the projection of the light beam when the objective lens
Claim 10
Dependent Claim
35 words
(42) is in the just focusing state, the diameter of the beam spot (82) being defined as the diameter of the region in which the intensity of the beam spot (82) has a maximum, 1/e2.
Claim 11
Dependent Claim
35 words
(42) is in the just focusing state, the diameter of the beam spot (82) being defined as the diameter of the region in which the intensity of the beam spot (82) has a maximum, 1/e2.
Claim 12
Dependent Claim
29 words
The system according to claim 6, characterized in that the width of said photoinsensitive region (64) ranges from 1/3 to 3 times the diameter of the beam spot (82).
Claim 13
Dependent Claim
119 words
The system according to claim 1, characterized in that said transfer means (52, 54, 110, 118, 120, 123) includes a projection lens (54) for directing the light beam toward the light .receiving surface (66) of the .photodetector (48) and means (52, 110, 118, 120) for deflecting the light beam in accordance with the distance between the objective lens (42) and the light reflecting surface (14), and the light receiving surface (66) of the photodetector (48) is arranged on an image forming plane on which an image (82) of the beam spot corresponding to the beam waist is formed by the objective lens (42) and the projection lens (54) when the objective lens (42) is in the just focusing state.
Claim 14
Dependent Claim
45 words
The system according to claim 8, characterized in that said means (52, 110, 118) for deflecting the light beam is a light shielding plate (52) to transmit light beams passing through only those areas which are off the optical axis of the projection lens (54).
Claim 15
Dependent Claim
23 words
The system according to claim 8, characterized in that said means (52, 110, 118) for deflecting the light beam is a biprism (110).
Claim 16
Dependent Claim
102 words
The system according to claim 1, characterized in that said transfer means (54, 120, 123) includes a projection lens (54) for directing the light beam toward the light receiving surface (66) of the photodetector (48), which has an optical axis intersecting the optical axis of the objective lens (42), and the light receiving surface (66) of the photodetector (48) is arranged on an image forming plane on which an image of the beam spot corresponding to the beam waist is formed by the objective lens (42) and the projection lens (54) when the objective lens (42) is in the just focusing state.
Claim 17
Dependent Claim
92 words
The system according to claim 1, characterized in that said transfer means (54) includes first and second projection lenses (54, 120) and a mirror (118), so that an image of the beam spot corresponding to the beam waist is formed on the mirror (118) by the objective lens (42) and the first projection lens (54) when the objective lens (42) is in the just focusing state, and that the image on the mirror (118) is transferred onto the light receiving surface (66) of the photodetector (48) by the second projection lens (120).
Claim 18
Dependent Claim
45 words
The system according to claim 8, characterized in that said means (52, 110, 118) for deflecting the light beam includes means for generating a light beam passing parallel to the optical axis of the objective lens (42) through an area arranged off the optical axis.
Claim 19
Dependent Claim
27 words
The system according to claim 1, characterized in that said transferring means includes a cylindrical lens (123) arranged between the objective lens (42) and the photodetector (48).
Claim 20
Independent Claim
134 words
A system for focusing a light beam on a light reflecting surface (14), characterized by comprising: a photodetector (48) having a light receiving surface (66) including at least two photosensitive regions (60-1, 60-2) and a photoinsensitive region (64) arranged between the two photosensitive regions (60-1, 60-2) and detecting no substantial light rays; and an objective lens (42) for converging and directing the light beam toward the light reflecting surface (14) and directing the reflected light beam from the light reflecting surface (14) toward the photodetector (48), whereby the light beam is projected toward the photoinsensitive region (64) when the objective lens (42) is in the just focusing state, and whereby the light beam is projected toward at least one of the photosensitive regions (60-1, 60-2) when the objective lens is in the defocusing state.
Claim 21
Independent Claim
134 words
A system for focusing a light beam on a light reflecting surface (14), characterized by comprising: a photodetector (48) having a light receiving surface (66) including at least two photosensitive regions (60-1, 60-2) and a photoinsensitive region (64) arranged between the two photosensitive regions (60-1, 60-2) and detecting no substantial light rays; and an objective lens (42) for converging and directing the light beam toward the light reflecting surface (14) and directing the reflected light beam from the light reflecting surface (14) toward the photodetector (48), whereby the light beam is projected toward the photoinsensitive region (64) when the objective lens (42) is in the just focusing state, and whereby the light beam is projected toward at least one of the photosensitive regions (60-1, 60-2) when the objective lens is in the defocusing state.
Claim 22
Dependent Claim
22 words
The system according to claim 15, characterized in that said photoinsensitive region (64) is a light-shielding layer (70) to shield light rays.
Claim 23
Dependent Claim
17 words
The system according to claim 15, characterized in that said light-shielding layer (70) is an alumina layer.
Claim 24
Dependent Claim
31 words
The system according to claim 15, characterized in that said photodetector (48) is a semiconductor photodetector, and said photoinsensitive region (64) is a recess region (78) formed in the semiconductor photodetector.
Claim 25
Dependent Claim
48 words
The system according to claim 15, characterized in that said photodetector (48) is formed on a semiconductor substrate, and said photoinsensitive region (64) is an impurity region (80) of the same conductivity type as the substrate (68) having a higher impurity density than that of the substrate (68).
Claim 26
Dependent Claim
82 words
The system according to claim 15, characterized in that the width of said photoinsensitive region (64) is a quarter or more of the diameter of the beam spot (82) formed on the light receiving surface (66) by the projection of the light beam when the objective lens (42) is in the just focusing state, the diameter of the beam spot (82) being defined as the diameter of the region in which the intensity of the beam spot (82) has a maximum, l/e2.
Claim 27
Dependent Claim
29 words
The system according to claim 15, characterized in that the width of said photoinsensitive region (64) ranges from 1/3 to 3 times the diameter of the beam spot (82).
References Cited (Backward Citations)
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