Photographic flash apparatus

Details Photographic flash apparatus Photographic flash apparatus

1975-04-18

1977-04-19

Segal, Robert

Electric lamp and discharge devices: systems

With radiant energy sensitive control means

Electric switch controlled by the radiant energy responsive...

315241P, H05B 4132, H05B 3702, H05B 3700

Patent

active

040190927

ABSTRACT:
Electronic flash apparatus of the general type having exposure-measuring and flash-limiting mechanism comprising a light-sensitive element connected in series with an integrating capacitor and a thyristor, arranged so that when the thyristor becomes conductive, it causes a pulse which interrupts or terminates the flash. In distinction from prior flash apparatus of this same general type, the present apparatus has circuitry in which one plate of the integrating capacitor is connected to the collector of a photo-transistor and the other plate is connected to the control grid of the thyristor and to a higher voltage source, while the emitter of the photo-transistor is connected to a lower voltage source. Other circuit details are disclosed, resulting in a flash unit which is less trouble-prone and easier to adjust than prior flash units of the same general type, and which compensates for the close-up effect so that pictures taken at close range are not over-exposed, as happens so often with many of the prior art flash units.

REFERENCES:
patent: 3716753 (1973-02-01), Exner
patent: 3774072 (1973-11-01), Ogawa
patent: 3864601 (1975-02-01), Schneider
patent: 3869642 (1975-03-01), Sabanci

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