Patent US3765312A successfully refreshed from Google Patents.
US3765312A
Expired / Lapsed
US
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Exposure control device
Assignee: Canon Inc
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Filing: 1972-05-25
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Granted: 1973-10-16
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Expires: 1992-05-25
Abstract
Abstract A light sensitive resistor for measuring light value of a scene to be photographed is in a bridge circuit from which the unbalance signal operates switches either to light lamps for guiding manual adjustment of exposure factors or to control a servomotor that makes the necessary adjustments. These adjustments, whether automatic or manual, produce changes in the bridge elements, so that balance of the bridge is reached when the proper exposure factor settings are made. Control of the servomotor and/or indication lamps is accomplished by means of an astable multivibrator of which the effective polarity of the output is changed by changing the duty cycle. The exposure factor adjustment obtained by balancing the bridge is stored in the value of a variable resistor which, after the shutter is released, controls, for example, the exposure time.
Inventors
- 👤 Y Takishima
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-10 02:24
CPC Classifications
G; G03; G03B; G03B7/00; G03B7/08; G03B7/081; G03B7/083
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
158 words
In an exposure control device controllable in response to the output of a photoelectric cell, an improvement comprising the combination of: a. light quantity control means, b. an astable multivibrator having two output terminals, c. a second control means interconnected between said two output terminals of said astable multivibrator for controlling said light quantity control means, d. switching means comprising at least one switching circuit which is actuated in response to the output of said photoelectric cell, said switching means being electrically coupled to said astable multivibrator for controlling the intervals at which said astable multivibrator makes transistions, and e. said light quantity control means including storage means which is controlled in response to the output of said second control means for storing an exposure factor as the state of a variable exposure factor control element prior to the shutter release operation and also including means for causing said element to control an exposure factor after shutter release.
Claim 2
Dependent Claim
158 words
In an exposure control device controllable in response to the output of a photoelectric cell, an improvement comprising the combination of: a. light quantity control means, b. an astable multivibrator having two output terminals, c. a second control means interconnected between said two output terminals of said astable multivibrator for controlling said light quantity control means, d. switching means comprising at least one switching circuit which is actuated in response to the output of said photoelectric cell, said switching means being electrically coupled to said astable multivibrator for controlling the intervals at which said astable multivibrator makes transistions, and e. said light quantity control means including storage means which is controlled in response to the output of said second control means for storing an exposure factor as the state of a variable exposure factor control element prior to the shutter release operation and also including means for causing said element to control an exposure factor after shutter release.
Claim 3
Dependent Claim
40 words
An improvement as set forth in claim 1 wherein said astable multivibrator further includes a pair of time constant circuits whose time constants during multivibrator operation are different from each other and mutually interchangeable by operation of said switching means.
Claim 4
Dependent Claim
71 words
An improvement as set forth in claim 1 wherein said switching means includes a bridge circuit in one arm of which said photoelectric cell is located and the output terminals of which are electrically coupled to the input terminals of said switching means; and wherein said switching means is made conductive in response to the output of said bridge cirCuit when unbalanced and then causes said astable multivibrator to start oscillating.
Claim 5
Dependent Claim
26 words
An improvement as set forth in claim 1 wherein said second control means comprises a motor which is drivingly coupled to said variable exposure factor element.
Claim 6
Dependent Claim
33 words
An improvement as set forth in claim 1 wherein said light quantity control means has manual controls and said second control means comprises display means for guiding the use of said manual controls.
Claim 7
Dependent Claim
23 words
An improvement as set forth in claim 3 wherein said switching means comprises a pair of switching circuits which are differential amplifier circuits.
Claim 8
Dependent Claim
110 words
An improvement as set forth in claim 2 wherein said time constant circuits have a common resistor network and wherein said switching means comprises a bridge circuit one arm of which comprises said photoelectric cell, and a pair of switching circuits to which are applied the output of said bridge circuit, and wherein said switching circuits are coupled to said resistor network of said time constant circuits so as to complete said time constant circuits at one of two points, or not at all, according to the state of said switching means, such point of completion being such as to determine the sense of the disparity of said time constants.
Claim 9
Dependent Claim
55 words
An improvement as set forth in claim 3 wherein said astable multivibrator comprises two transistors and a pair of time constant circuits whose capacitors are coupled to a series of resistors differentially and unequally apportionable to said respective capacitors by selection through said switching means of the circuit return point in said series of resistors.
Claim 10
Dependent Claim
51 words
An improvement as set forth in claim 5 wherein said display circuit comprises a pair of lamps and a pair of diodes which are each inserted in series with one of said lamps, but poled in the opposite direction relative to each other, the series lamp-diode circuits being connected in parallel.
Claim 11
Dependent Claim
88 words
An improvement as set forth in claim 4 wherein said variable exposure factor element is a variable resistor and said light quantity control means comprises shutter speed control means which comprises a CR time constant circuit comprising said variable resistor and a capacitor, a detector circuit for detecting a voltage drop across said capacitor, and electromagnet means coupled to said detector circuit for closing a shutter when said voltage drop has reached a predetermined value, said motor being operatively coupled to said variable resistor for varying its resistance.
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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) | 1976-10-15 | 1977-04-16 | 1977-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-15 | 1981-04-16 | 1981-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-15 | 1985-04-16 | 1985-10-16 | $7700.00 | Window Closed / Lapsed |