US3813679A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Focus detector device
Assignee: Canon Inc
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Filing: 1972-10-17
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Granted: 1974-05-28
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Expires: 1992-10-17
Abstract
Abstract A focus detector device of this invention employs flashlight as reference light so that the quantity of such light reflected by an object to be photographed is converted into an electrical signal and stored in a storage capacitor, whereby the focus detection may be effected in accordance with the quantity of the stored signal. The pre-flash is automatically actuated when the ambient light falls below a certain level. For focusing two photodiodes of logarithmic compression characteristics are used. A third photoelectric element meansures the amount of ambient light.
Inventors
- 👤 G Hasegawa
- 👤 S Nakamoto
- 👤 K Hosoe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 11:55
CPC Classifications
G; G02; G02B; G02B7/00; G02B7/28; G02B7/30; G02B7/32
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
319 words
A focus detector device in a photographic camera having a focussable photographic lens, comprising: optical means offset from said photographic lens for forming therethrough an image of an object to be photographed, said optical means being sufficiently offset to cause the position of said image to be detectably displaced laterally in accordance with the distance of said object from said camera; first photoelectric converter means disposed substantially in the focal plane of said optical means and having a light receiving surface of such a configuration as to cause said converter means to produce an electrical output corresponding to the object distance; focus detection control circuit means electrically connected so that the input thereof receives the output from said first photoelectric convertEr means, said focus detection control circuit means including: driving power means for operating the focusing movement of said photographic lens; a drive control circuit for controlling said driving power means, including means producing a signal corresponding to the position of said photographic lens, means for comparing said signal with the output of said first photoelectric converter means and means for operating said driving power means to cause said signal to balance the output of said first photoelectric converter means; a light source for illuminating at least a portion of said object; an illumination control circuit for controlling the illumination of said light source, said light source being electrically connected with the input of said illumination control circuit; and means including a second photoelectric converter means and switching circuit means operated thereby, said second photoelectric converter means being responsive to the brightness of said object and arranged to operate said switching circuit means when the brightness of the object is below a predetermined brightness level to turn on said illumination control circuit, said switching means being connected to said illumination control circuit, and thereby to improve the operation of said first photoelectric converter means under low brightness light conditions.
Claim 2
Dependent Claim
319 words
A focus detector device in a photographic camera having a focussable photographic lens, comprising: optical means offset from said photographic lens for forming therethrough an image of an object to be photographed, said optical means being sufficiently offset to cause the position of said image to be detectably displaced laterally in accordance with the distance of said object from said camera; first photoelectric converter means disposed substantially in the focal plane of said optical means and having a light receiving surface of such a configuration as to cause said converter means to produce an electrical output corresponding to the object distance; focus detection control circuit means electrically connected so that the input thereof receives the output from said first photoelectric convertEr means, said focus detection control circuit means including: driving power means for operating the focusing movement of said photographic lens; a drive control circuit for controlling said driving power means, including means producing a signal corresponding to the position of said photographic lens, means for comparing said signal with the output of said first photoelectric converter means and means for operating said driving power means to cause said signal to balance the output of said first photoelectric converter means; a light source for illuminating at least a portion of said object; an illumination control circuit for controlling the illumination of said light source, said light source being electrically connected with the input of said illumination control circuit; and means including a second photoelectric converter means and switching circuit means operated thereby, said second photoelectric converter means being responsive to the brightness of said object and arranged to operate said switching circuit means when the brightness of the object is below a predetermined brightness level to turn on said illumination control circuit, said switching means being connected to said illumination control circuit, and thereby to improve the operation of said first photoelectric converter means under low brightness light conditions.
Claim 3
Dependent Claim
97 words
A focus detector device according to claim 1, wherein said first photoelectric converter means comprises two photodiode means of logarithmic compression characteristic, and said focus detection control circuit means further includes a differential amplifier having differential inputs connected with said photodiode means and an output connected with said focus detection control circuit means one of said photodiode means producing an output corresponding to the image position of the object which is variable in accordance with the position of the object, and the other producing an output corresponding to the lighting of the object regardless of image position.
Claim 4
Dependent Claim
28 words
A focus detector device according to claim 2, wherein said focus detection control circuit means further includes a storage capacitor connected with the output of said differential amplifier.
Claim 5
Dependent Claim
82 words
A focus detector device according to claim 3, wherein said focus detection control circuit means includes a delay circuit having an electric timer circuit and a start switch responsive to camera release operation and switching means connected to the timer circuit so as to change over in response thereto, said switching means being connected between said capacitor and said differential amplifier circuit so as to be opened after a predetermined time to thereby electrically disconnect said capacitor and said differential amplifier circuit.
Claim 6
Dependent Claim
16 words
A focus detector device according to claim 3, wherein said light source is a xenon tube.
Claim 7
Dependent Claim
113 words
A focus detector device according to claim 1, wherein said focus detection control circuit means further includes a circuit for confirming the focus-detected condition, said circuit having: generator means drivingly connected with said driving power means for producing a signal while said driving power means is operating; a variable resistor in said drive control circuit variable with the position of said photographic lens; a differential amplifier circuit in said drive control circuit having differential inputs connected with said generator means and said variable resistor; and indicating means electrically connected with the output of said differential amplifier circuit so as to indicate the completion of a focusing cycle in accordance with said differential output.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-05-27 | 1977-11-26 | 1978-05-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-27 | 1981-11-26 | 1982-05-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-27 | 1985-11-26 | 1986-05-28 | $7700.00 | Window Closed / Lapsed |