US4916473A
Expired / Lapsed
US
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Focus detection apparatus
Assignee: Minolta Co Ltd
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Filing: 1988-09-27
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Granted: 1990-04-10
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Expires: 2008-09-27
Abstract
Abstract A focus detection apparatus for a camera comprising: a condensor lens being arranged close to or behind a predetermined focal plane of an objective lens of the camera. A pair of image separation members for separating the image of an object formed on the predetermined focal plane by use of light having been passed through said objective lens into two images which are arranged behind the condensor lens symmetrically with respect to the optical axis of the objective lens, wherein the correlation between the two images formed separately is measured in order to detect the focus condition of the objective lens; said image separating members including a mask members for projecting the exit pupil of the image separation members within an exit pupil of a cata-dioptric lens system as the objective lens.
Inventors
- 👤 Hiromu Mukai
- 👤 Tokuji Ishida
- 👤 Hisashi Tokumaru
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 06:14
CPC Classifications
G; G02; G02B; G02B7/00; G02B7/28; G02B7/34
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
187 words
A focus detection apparatus for a camera capable of using both a cata-dioptric lens system and a dioptric lens system as an objective lens, comprising: a condenser lens means being arranged close to or behind a predetermined focal plane of the objective lens, and an image separation means for separating an image of an object formed on the predetermined focal plane by use of light having been passed through said objective lens into two images, including: a pair of separation lenses arranged, behind said condenser lens means, symmetrically with respect to the optical axis of said objective lens, for forming the two images, and a mask means having a pair of apertures whose images, when projected on an exit pupil of the objective lens by the condenser lens means and separation lenses, are located within a range determined by an inner shape of the exit pupil of the cata-dioptric lens system and an outer shape of the exit pupil of the dioptric lens system, wherein the correlation distance between the two separately formed images is measured in order to detect the focus condition of the objective lens.
Claim 2
Dependent Claim
187 words
A focus detection apparatus for a camera capable of using both a cata-dioptric lens system and a dioptric lens system as an objective lens, comprising: a condenser lens means being arranged close to or behind a predetermined focal plane of the objective lens, and an image separation means for separating an image of an object formed on the predetermined focal plane by use of light having been passed through said objective lens into two images, including: a pair of separation lenses arranged, behind said condenser lens means, symmetrically with respect to the optical axis of said objective lens, for forming the two images, and a mask means having a pair of apertures whose images, when projected on an exit pupil of the objective lens by the condenser lens means and separation lenses, are located within a range determined by an inner shape of the exit pupil of the cata-dioptric lens system and an outer shape of the exit pupil of the dioptric lens system, wherein the correlation distance between the two separately formed images is measured in order to detect the focus condition of the objective lens.
Claim 3
Dependent Claim
22 words
A focus detection apparatus according to claim 1, wherein the outer and inner shapes of said pair of apertures are coaxial arcs.
Claim 4
Dependent Claim
61 words
A focus detection apparatus according to claim 1 wherein the mask means includes a first and second mask member, one of the mask members including an electrooptical device that can be activated to define the desired projected images of the apertures of the mask means on the exit pupil of a desired lens system in cooperation with the other mask member.
Claim 5
Dependent Claim
16 words
A focus detection apparatus according to claim 1 wherein the mask means includes an electro-optic device.
Claim 6
Dependent Claim
29 words
A focus detection apparatus according to claim 3 wherein the first and second mask members are spaced apart from each other along an optical axis of the separation lenses.
Claim 7
Dependent Claim
17 words
A focus detection apparatus according to claim 4 wherein the electro-optic device is a liquid crystal device.
References Cited (Backward Citations)
US4322616A
Cited
JPS56130725A
Cited
US4370551A
Cited
JPS6032013A
Cited
US4526458A
Cited
US4794416A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-04-09 | 1993-10-09 | 1994-04-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-04-09 | 1997-10-09 | 1998-04-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-04-09 | 2001-10-09 | 2002-04-10 | $7700.00 | Window Closed / Lapsed |