US3591829A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic control device for electronic flash
Assignee: Minolta Co Ltd
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Filing: 1968-04-18
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Granted: 1971-07-06
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Expires: 1988-04-18
Abstract
Abstract A device for automatic control of the quantity of light from an electronic flash, by comparing the brightness of a photographic object with the quantity of light required for particular photographing conditions including the degree of lens aperture selected and the sensitivity of the film used. The brightness of the photographic object is measured as the sum of the natural light brightness and the brightness due to electronic flash, and as soon as the sum brightness thus measured reaches the required quantity of light, a stop signal is given. Thereby, the electronic flash is controlled, and at the same time signal is given for the sufficient brightness of the photographic object.
Inventors
- 👤 Tomoji Murata
- 👤 Sadao Yamaoka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 05:47
CPC Classifications
H; H05; H05B; H05B41/00; H05B41/14; H05B41/30
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
233 words
An automatic control circuit for determining the duration of light emitted by an electronic flash unit, said control circuit comprising photoelectric means positioned to receive light reflected from an object illuminated by natural light and by flash light from the electronic flash unit, electric filter means coupled to said photoelectric means and operative to furnish at a first output thereof a first component representative of the reflected natural light and at a second output thereof a second component representative of the reflected flash light, integrating circuit means coupled to the second output of said electric filter means for integrating said second component, an adding circuit coupled to said integrating circuit means and to the first output of said electric filter means and operative to produce an output voltage proportional to the sum of said first component and the integration of said second component, circuit means to provide a reference voltage proportional to the exposure as established by the sensitivity of the film in the associated camera and the size of the lens aperture, a comparator coupled to said adding circuit and to said circuit means and operative to produce a control signal when the difference between said output voltage and said reference voltage reaches a predetermined value, and a firing circuit coupled to said comparator and to the electronic flash unit for terminating the flash produced thereby upon reception of said control signal.
Claim 2
Dependent Claim
233 words
An automatic control circuit for determining the duration of light emitted by an electronic flash unit, said control circuit comprising photoelectric means positioned to receive light reflected from an object illuminated by natural light and by flash light from the electronic flash unit, electric filter means coupled to said photoelectric means and operative to furnish at a first output thereof a first component representative of the reflected natural light and at a second output thereof a second component representative of the reflected flash light, integrating circuit means coupled to the second output of said electric filter means for integrating said second component, an adding circuit coupled to said integrating circuit means and to the first output of said electric filter means and operative to produce an output voltage proportional to the sum of said first component and the integration of said second component, circuit means to provide a reference voltage proportional to the exposure as established by the sensitivity of the film in the associated camera and the size of the lens aperture, a comparator coupled to said adding circuit and to said circuit means and operative to produce a control signal when the difference between said output voltage and said reference voltage reaches a predetermined value, and a firing circuit coupled to said comparator and to the electronic flash unit for terminating the flash produced thereby upon reception of said control signal.
Claim 3
Dependent Claim
68 words
The automatic control circuit set forth in claim 1, wherein said photoelectric means includes a first photoelectric element and a second photoelectric element, and said electric filter means includes first and second filter portions respectively coupled to said first and second photoelectric elements, said first filter portion being operative to pass only said first component and said second filter portion being operative to pass only said second component.
Claim 4
Dependent Claim
19 words
The automatic control circuit set forth in claim 1, wherein said photoelectric means consists of a single photoelectric element.
Claim 5
Dependent Claim
113 words
The automatic control circuit set forth in claim 1, wherein said firing circuit includes a capacitor coupled in parallel with said electronic flash unit and operative to fire said electronic flash unit by discharging therethrough, a starting section having a silicon controlled rectifier coupled to said capacitor and being conductive in response to the discharge of said capacitor to close a switchable circuit through the electronic flash unit, a reverse bias section for applying a reverse bias to said silicon controlled rectifier upon reapplication with a predetermined time delay determined by a capacity and a resistance, and a pair of diodes preventing mutual interference between said starting section and said reverse bias section.
Claim 6
Dependent Claim
35 words
The automatic control circuit set forth in claim 1, and further comprising an indicating means coupled to said comparator and being operative to provide an alerting signal when said output voltage exceeds said reference voltage.
References Cited (Backward Citations)
US3350604A
Cited
US3464332A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-07-05 | 1975-01-04 | 1975-07-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-07-05 | 1979-01-04 | 1979-07-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-07-05 | 1983-01-04 | 1983-07-06 | $7700.00 | Window Closed / Lapsed |