US3681649A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Photo flash intensity control with variable resistor in flash tube discharge circuit
Assignee: Pentax Corp
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Filing: 1970-09-10
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Granted: 1972-08-01
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Expires: 1990-09-10
Abstract
Abstract A system for controlling the extent to which flash illumination is provided during exposure of film in a camera. A preparatory flash and a main flash are provided with the system. Light from the preparatory flash is reflected from the object which is to be photographed to a photosensitive unit which responds to this reflected light for influencing the setting of a variable resistor whose setting is further influenced in accordance with additional exposure-determining factors, so that the variable resistor is set at a given value indicative of these exposuredetermining factors as well as the light reflected during the preparatory flash. With the information thus stored at the variable resistor in the form of the given value of the setting thereof, this variable resistor is operatively connected to the main flash for controlling the extent of flash illumination provided thereby during actual film exposure.
Inventors
- 👤 Naoyuki Uno
- 👤 Seijiro Tokutomi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 09:49
CPC Classifications
H; H05; H05B; H05B41/00; H05B41/14; H05B41/30; H05B41/32
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
184 words
For use with a camera, preparatory flash means for providing preparatory flash illumination, photosensitive means for receiving from an object which is to be photographed light reflected from the object, variable resistor means operatively connected with said photosensitiVe means to be set thereby at a value influenced by the light received by said photosensitive means in response to said preparatory flash means, means operatively connected with said variable resistor means for additionally influencing the latter according to additional exposure-determining factors, so that said variable resistor means is set at a given value indicative of the light reflected from the object in response to the preparatory flash illumination and the additional exposure-determining factors, main flash means for providing flash illumination during exposure of film in the camera, and connecting means for connecting said variable resistor means to said main flash means after said variable resistor means has been set at said given value and for maintaining said variable resistor means operatively connected with said main flash means during operation of the latter, so that the main flash means is regulated to provide a proper exposure.
Claim 2
Dependent Claim
184 words
For use with a camera, preparatory flash means for providing preparatory flash illumination, photosensitive means for receiving from an object which is to be photographed light reflected from the object, variable resistor means operatively connected with said photosensitiVe means to be set thereby at a value influenced by the light received by said photosensitive means in response to said preparatory flash means, means operatively connected with said variable resistor means for additionally influencing the latter according to additional exposure-determining factors, so that said variable resistor means is set at a given value indicative of the light reflected from the object in response to the preparatory flash illumination and the additional exposure-determining factors, main flash means for providing flash illumination during exposure of film in the camera, and connecting means for connecting said variable resistor means to said main flash means after said variable resistor means has been set at said given value and for maintaining said variable resistor means operatively connected with said main flash means during operation of the latter, so that the main flash means is regulated to provide a proper exposure.
Claim 3
Dependent Claim
23 words
The combination of claim 1 and wherein said variable resistor means is a transistor having an internal resistance set at said given value.
Claim 4
Dependent Claim
65 words
The combination of claim 1 and wherein said preparatory and main flash means include a single flash tube and a pair of triggering circuits one of which is a preparatory triggering circuit for actuating said single flash tube to form said preparatory flash means and the other of which is a main triggering circuit for actuating said flash tube to provide said main flash means.
Claim 5
Dependent Claim
23 words
The combination of claim 3 and wherein said variable resistor means is a transistor having an internal resistance which assumes said given value.
Claim 6
Dependent Claim
31 words
The combination of claim 4 and wherein said means for influencing said variable resistor means according to additional exposure-determining factors includes a variable resistor connected in series with said photosensitive means.
Claim 7
Dependent Claim
57 words
The combination of claim 5 and wherein a junction interconnects said variable resistor forming said means for introducing said additional exposure-determining factors and said photosensitive means, a current-amplifying transistor connected with said junction, and an integrating capacitor operatively connected with an emitter of said current-amplifying transistor and connected to said transistor which forms said variable resistor means.
Claim 8
Dependent Claim
27 words
The combination of claim 6 and wherein a transistorized amplifier is connected between said integrating capacitor and a base of said transistor of said variable resistor means.
Claim 9
Dependent Claim
73 words
The combination of claim 7 and wherein said connecting means includes a switch connecting said transistor which forms said variable resistor means to said flash tube only when the latter provides the main flash illumination, a preparatory flash capacitor connected with said flash tube for providing a discharge through the latter during preparatory flash illumination, said switch connecting said flash tube into the circuit of said preparatory flash capacitor during preparatory flash illumination.
Claim 10
Dependent Claim
47 words
The combination of claim 8 and wherein a main flash capacitor is provided for discharging through said flash tube during main flash illumination, and additional switch means for connecting said main flash capacitor to said flash tube while said variable resistor means is connected in series therewith.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-08-01 | 1976-01-31 | 1976-08-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-08-01 | 1980-01-31 | 1980-08-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-08-01 | 1984-01-31 | 1984-08-01 | $7700.00 | Window Closed / Lapsed |