US3842425A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus enlarging the range of exposure time control
Assignee: KABUSHIKI HAISHA LATTARI TOKER
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Filing: 1973-06-04
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Granted: 1974-10-15
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Expires: 1993-06-04
Abstract
Abstract A built-in exposure time control apparatus for a camera shutter in which a detector detects whether the brightness of the subject being photographed is above or below a given brightness level. An exposure time control circuit develops an exposure time control signal used to close a camera shutter and having a delay in dependence upon the brightness of the subject being photographed. The delay is determined by circuitry that memorizes a voltage representative of the brightness and extends the delay under control of the detector if the brightness detected is below the given brightness level. The delay extension is accomplished by placing in circuit an additional memory extending the range of the memory circuit thereby extending the range of possible exposure time control. The detector determines whether the brightness detected is above or below the given level to determine the necessity of extending the range of the delay. The delay is made by varying mechanical limits or determinations of possible movements of a mechanical member as a function of the brightness being sensed by a photoconductive element. The detector can also make the determination electronically with a transistor functioning as a comparator comparing a predetermined voltage, set by a voltage divider, with a varying voltage proportionate to the brightness of the subject being photographed and determined by the photoconductive element. The electronic comparator determines according to the comparison of the voltages whether the delay is to be extended by placing in circuit the necessary additional memory and delay elements.
Inventors
- 👤 K Kitai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 11:40
CPC Classifications
G; G01; G01J; G01J1/00; G01J1/42; G01J1/44; G01J1/46; G03; G03B; G03B7/00; G03B7/08; G03B7/081; G03B7/083
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
210 words
For use in a camera having a shutter, a built-in automatic exposure time control apparatus for controlling the exposure time of a shutter in a camera comprising, detector means having means detecting when in use the brightness of a subject being photographed and brightness-level determining means for determining whether the brightness of said subject is above a given level or below said given level, said detector means comprising a detecting circuit including a photoconductive element for sensing said brightness and said brightness-level determining means comrpising a comparator comparing a given voltage and a variable voltage under control of said photoconductive element varying in dependence upon said brightness, signal-developing means coactive with said detector means developing an output signal for closing said shutter after opening thereof to determine exposure time comprising first means for determining the exposure time as a function of said brightness of said subject and second means connectable to said first means including capacitor means, said brightness-level determining means further including means for connecting said second means to said first means when said brightness is below said given level to augment said first means and to jointly therewith vary said output signal, and means receptive of said output signal for use as a command to close said shutter.
Claim 2
Dependent Claim
210 words
For use in a camera having a shutter, a built-in automatic exposure time control apparatus for controlling the exposure time of a shutter in a camera comprising, detector means having means detecting when in use the brightness of a subject being photographed and brightness-level determining means for determining whether the brightness of said subject is above a given level or below said given level, said detector means comprising a detecting circuit including a photoconductive element for sensing said brightness and said brightness-level determining means comrpising a comparator comparing a given voltage and a variable voltage under control of said photoconductive element varying in dependence upon said brightness, signal-developing means coactive with said detector means developing an output signal for closing said shutter after opening thereof to determine exposure time comprising first means for determining the exposure time as a function of said brightness of said subject and second means connectable to said first means including capacitor means, said brightness-level determining means further including means for connecting said second means to said first means when said brightness is below said given level to augment said first means and to jointly therewith vary said output signal, and means receptive of said output signal for use as a command to close said shutter.
Claim 3
Dependent Claim
60 words
For use in a camera having a shutter, a built-in automatic exposure time control apparatus according to claim 1, in which said brightness-level determining means comprises an iris in a path of light from the subject being photographed to said photoconductive element, and means automatically displacing said iris from said light path when said brightness is below said given level.
Claim 4
Dependent Claim
173 words
In a camera having a shutter, light-responsive means sensing the brightness of a subject being photographed, detector means coactive with said light-responsive means determining whether said brightness is below or above a given brightness level, means including said light-responsive means developing an output signal for closing a shutter after opening thereof to determine exposure time, a trigger circuit means for closing a shutter upon application of said output signal, means memorizing said output signal, delay means including the last-mentioned means having a time constant delaying application of said output signal to said trigger circuit means to determine an exposure time as a function of whether said sigNal memorized is above said given brightness level and in accordance with the value of the memorized signal, time-constant-increasing means in said delay means controlled in dependence upon whether the detected brightness is below said given level for effectively increasing said time constant in conjunction with said means memorizing said output signal, and change-over means rendered effective by said detector means for rendering said time-constant-increasing means effective.
Claim 5
Dependent Claim
173 words
In a camera having a shutter, light-responsive means sensing the brightness of a subject being photographed, detector means coactive with said light-responsive means determining whether said brightness is below or above a given brightness level, means including said light-responsive means developing an output signal for closing a shutter after opening thereof to determine exposure time, a trigger circuit means for closing a shutter upon application of said output signal, means memorizing said output signal, delay means including the last-mentioned means having a time constant delaying application of said output signal to said trigger circuit means to determine an exposure time as a function of whether said sigNal memorized is above said given brightness level and in accordance with the value of the memorized signal, time-constant-increasing means in said delay means controlled in dependence upon whether the detected brightness is below said given level for effectively increasing said time constant in conjunction with said means memorizing said output signal, and change-over means rendered effective by said detector means for rendering said time-constant-increasing means effective.
Claim 6
Dependent Claim
92 words
In a camera according to claim 3, in which said delay means comprises a circuit having a time constant, said light-responsive means comprising a photo-cell having a resistance varying in dependence upon the brightness of the subject being photographed, said means memorizing said output signal comprising capacitor means in said circuit charged at a rate dependent upon the resistance of said photo-cell, and said time-constant-increasing means controlled in dependence upon whether the detected brightness is below said given level comprising means to change the value of the capacitance of said capacitor means.
Claim 7
Dependent Claim
92 words
In a camera according to claim 4, including a current-measuring device responsive to current flow through said photo-cell, said device having a deflectable pointer moving to positions representative of the value of said current, means to selectively hold the pointer in a position to which it deflects, switch means in said circuit, and means for selectively operating said switch means to select the time constant of said circuit in dependence upon whether the deflected position in which said pointer is held corresponds to a current value above or below a predetermined value.
Claim 8
Dependent Claim
86 words
In a camera according to claim 3, in which said delay means comprises a circuit having a time constant, said light-responsive means comprising a charging circuit having a photo-cell having a resistance varying in dependence upon the brightness of the subject being photographed, capacitor means in said circuit charged at a rate dependent upon the resistance of said photo-cell, and said time-constant-increasing means controlled in dependence upon whether the detected brightness is below said given level comprising means to vary the resistance of said charging circuit.
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) | 1977-10-14 | 1978-04-15 | 1978-10-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-14 | 1982-04-15 | 1982-10-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-14 | 1986-04-15 | 1986-10-15 | $7700.00 | Window Closed / Lapsed |