Patent US4258989A successfully refreshed from Google Patents.
US4258989A
Expired / Lapsed
US
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Focus detecting device
Assignee: Pentax Corp
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Filing: 1979-04-25
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Granted: 1981-03-31
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Expires: 1999-04-25
Abstract
Abstract A focus detecting device having a release lens for reforming the image of an object which is formed between a lens and the focal plane of the lens. A mirror is provided between the release lens and an image reforming plane for dividing the primary image into two secondary images. Two light receiving element arrays provided in the image forming planes of said secondary images provide outputs to a signal processing circuit for comparison to produce a signal indicating whether or not the lens is focussed on the object. The mirror for dividing the primary image into two secondary images, shifts the two secondary images in opposite directions on the light receiving element arrays at the time of defocussing so that the difference between the outputs of said two light receiving element arrays is not zero. At the time of focussing, the two secondary images are located at equivalent positions on the light receiving element arrays so that the difference between the outputs of said two light receiving element arrays is zero.
Inventors
- 👤 Seijiro Tokutomi
- 👤 Ryota Ogawa
- 👤 Michiro Ohishi
- 👤 Kazuo Nakamura
- 👤 Masao Jyojiki
- 👤 Satoru Tachihara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 04:15
CPC Classifications
G; G02; G02B; G02B7/00; G02B7/28; G02B7/34
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
187 words
A focus detecting device comprising; a release lens for reforming a primary image of an object which is formed relative to a photographing lens and the focal plane of said photographing lens to produce an image reforming plane; a mirror provided optically between said release lens and said image reforming plane for dividing the primary image into two secondary images; a pair of light receiving element arrays provided in the image forming planes of said secondary images; and signal processing circuit means for subjecting the outputs of said light receiving element arrays to comparison and producing an output signal indicating whether or not said lens is focussed on said object, wherein said two secondary images are shifted in the opposite direction on said light receiving element arrays if the image is defocussed so that the difference between the outputs of said two light receiving element arrays is not zero, and when the image is focussed said two secondary images are located at equivalent position on said light receiving element arrays so that the difference between the outputs of said two light receiving element arrays is substantially zero.
Claim 2
Dependent Claim
187 words
A focus detecting device comprising; a release lens for reforming a primary image of an object which is formed relative to a photographing lens and the focal plane of said photographing lens to produce an image reforming plane; a mirror provided optically between said release lens and said image reforming plane for dividing the primary image into two secondary images; a pair of light receiving element arrays provided in the image forming planes of said secondary images; and signal processing circuit means for subjecting the outputs of said light receiving element arrays to comparison and producing an output signal indicating whether or not said lens is focussed on said object, wherein said two secondary images are shifted in the opposite direction on said light receiving element arrays if the image is defocussed so that the difference between the outputs of said two light receiving element arrays is not zero, and when the image is focussed said two secondary images are located at equivalent position on said light receiving element arrays so that the difference between the outputs of said two light receiving element arrays is substantially zero.
Claim 3
Dependent Claim
24 words
The device of claim 1 further comprising display means receiving the output signal from said signal process circuit for indicating the state of focus.
Claim 4
Independent Claim
83 words
The device of claims 1 or 2 wherein said signal processing circuit means comprises differential circuit means responsive to the outputs of a corresponding pair of elements in said pair of light receiving element arrays, absolute value circuit means for converting the output of said differential circuit means into an absolute value signal, transducer means to convert the extension of said lens into an electrical signal and detector means receiving said electrical signal and said absolute value signal and producing said output signal.
Claim 5
Dependent Claim
25 words
The device of claim 3 wherein said detector means produces said output signal as a function of minimum absolute value with respect to lens extension.
Claim 6
Dependent Claim
19 words
The device of claim 3 wherein said light receiving arrays respectively comprise a series of N light sensitive elements.
Claim 7
Dependent Claim
58 words
The device of claim 5 wherein said differential circuit means comprises a series of N differential circuits, said absolute value circuit means comprises N absolute value detectors coupled respectively to said differential circuits and further comprising an addition circuit for adding the outputs of said absolute value detectors and supplying said absolute value signal to said detector means.
Claim 8
Dependent Claim
30 words
The device of claim 5 wherein said light sensitive elements are selected from the group consisting of silicon photo-diodes, chemical semiconductors, charge coupled devices and self scanning type image sensors.
Claim 9
Independent Claim
17 words
The device of claims 1 or 2 wherein said lens comprises of photography lens on a camera.
Claim 10
Dependent Claim
34 words
The device of claim 8 further comprising a mirror receiving the primary image and deflecting said image to said release lens thereby allowing viewing of said image in a view finder of said camera.
Claim 11
Dependent Claim
18 words
The device of claim 9 further comprising an aperture positioned between said mirror means and said release lens.
Claim 12
Dependent Claim
40 words
The device of claim 1, wherein said mirror is roof-shaped having two surfaces, disposed relative to the optical axis of said release lens so as to reflect the light passing through said release lens to provide said two secondary images.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-03-30 | 1984-09-29 | 1985-03-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-30 | 1988-09-29 | 1989-03-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-30 | 1992-09-29 | 1993-03-31 | $7700.00 | Window Closed / Lapsed |