Patent US3543422A successfully refreshed from Google Patents.
EP0259148A2
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EP
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Focus detector
Assignee: Canon Inc
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Filing: 1987-09-02
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Granted: —
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Expires: 2007-09-02
Abstract
Abstract A focus detector which comprises as follows: means (1 to 4) for irradiating a focused light beam to a surface (5) to be examined; an optical element (7) located in a vicinity of a focus point of a detection light beam formed by the irradiation light beam reflected by or passed through the surface and refocused; said optical element splitting a portion of the detection light beam only when the irradiation light beam is not in an in-focus state on the surface; and means (10) for receiving the light beam split by said optical element so as to detect a focus error signal.
Inventors
- 👤 Hiroshi Matsui
- 👤 Osamu Koyama
- 👤 Hideaki Yano
- 👤 Yasuo Nakamura
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 10:10
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/12; G11B7/135; G11B7/1381; G02; G02B; G02B27/00; G02B27/10; G02B27/16; G11B7/08; G11B7/09; G11B7/0908; G11B7/0916
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
94 words
A focus detector comprising: means for irradiating a focused light beam to a surface to be examined; an optical element located in a vicinity of a fucus point of a detection light beam formed by the irradiation light beam reflected by or passed through the surface and refocused; said optical element splitting a portion of the detection light beam only when the irradiation light beam is not in an in-focus state on the surface; and means for receiving the light beam split by said optical element so as to detect a focus error signal.
Claim 2
Dependent Claim
94 words
A focus detector comprising: means for irradiating a focused light beam to a surface to be examined; an optical element located in a vicinity of a fucus point of a detection light beam formed by the irradiation light beam reflected by or passed through the surface and refocused; said optical element splitting a portion of the detection light beam only when the irradiation light beam is not in an in-focus state on the surface; and means for receiving the light beam split by said optical element so as to detect a focus error signal.
Claim 3
Dependent Claim
33 words
A focus detector according to Claim 1, wherein said irradiation means comprises a light source and a first lens system for focusing a light beam emitted from said light source onto said surface.
Claim 4
Dependent Claim
19 words
A focus detector according to Claim 2 further comprising a second lens system for focusing the detection light beam.
Claim 5
Dependent Claim
41 words
A focus detector according to Claim 1, wherein said optical element comprises a reflection plane having a boundary to a transmissive section out of a light path of the detection light beam in an in-focus state of the irradiation light beam.
Claim 6
Dependent Claim
28 words
A focus detector according to Claim 4, wherein said reflection plane is of stripe shape having a width corresponding to a beam waist of the detection light beam.
Claim 7
Dependent Claim
29 words
A focus detector according to Claim 5, wherein said surface has a track thereon and a longitudinal direction of said stripe-shaped reflection plane is substantially orthogonal to the track.
Claim 8
Dependent Claim
51 words
A focus detector according to Claim 4, wherein said signal detection means comprises a first photo-detector having a two-split photo-receiving plane for receiving the detection light beam overflown from said reflection plane and a signal processing circuit for finitely differentiating output signals from the respective photo-receiving planes of said first photo-detector.
Claim 9
Dependent Claim
22 words
A focus detector according to Claim 7 further comprising a second photo-detector for receiving a light beam reflected by said reflection plane.
Claim 10
Dependent Claim
35 words
A focus detector according to Claim 8, wherein said surface is an information record surface having a track thereon, and said second photo-detector detects at least one of an information signal and a tracking signal.
Claim 11
Dependent Claim
69 words
A focus detector according to Claim 1, wherein said optical element comprises a plate-like transparent member with one side thereof being planar and the other side thereof having a plane parallel to said one side and a plane inclined with respect to said one side, therein a boundary thereof being out of a light path of the detection light beam in an in-focus state of the irradiation light beam.
Claim 12
Dependent Claim
28 words
A focus detector according to Claim 10, wherein said parallel plane is of stripe shape having a width corresponding to a beam waist of the detection light beam.
Claim 13
Dependent Claim
29 words
A focus detector according to Claim 11, wherein said surface has a track thereon and a longitudinal direction of said stripe-shaped parallel plane is substantially orthogonal to the track.
Claim 14
Dependent Claim
51 words
A focus detector according to Claim 10, wherein said signal detection means includes a first photo-detector haivng a two-split photo-receiving plane for receiving the detection light beam refracted by said inclined plane and a signal processing circuit for finitely differentiating output signals from the respective photo-receiving planes of said first photo-detector.
Claim 15
Dependent Claim
22 words
A focus detector according to Claim 13 further comprising a second photo-detector for detecting a light beam passed through said parallel plane.
Claim 16
Dependent Claim
35 words
A focus detector according to Claim 14, wherein said surface is an information record surface having a track thereon, and said second photo-detector detects at least one of an information signal and a tracking signal.
Claim 17
Dependent Claim
65 words
A focus detection system in which an irradiating light beam to be focused on a surface is reflected or transmitted as a detection beam whose state of focus on a splitting means is dependent on the state of focus of the irradiating beam on said surface, the splitting function of the spliting means being dependent on the state of focus of the detection beam thereon.
Claim 18
Dependent Claim
65 words
A focus detection system in which an irradiating light beam to be focused on a surface is reflected or transmitted as a detection beam whose state of focus on a splitting means is dependent on the state of focus of the irradiating beam on said surface, the splitting function of the spliting means being dependent on the state of focus of the detection beam thereon.
References Cited (Backward Citations)
No citation records indexed.
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