Electronic flash device of automatic light adjusting type
First Claim
1. An electronic flash device of an automatic light adjusting type, including a main capacitor for storing charge at a high voltage, a flash discharge tube for generating flash light with a current upon discharging said main capacitor, and a light adjusting circuit for adjusting a light amount of said flash light, said flash device comprising:
- wherein said light adjusting circuit includes;
a reflected light measuring unit for outputting an integration voltage for representing a light amount of reflected light from a photographic field illuminated with said flash light;
a non-contact switch for short-circuiting terminals of said main capacitor upon being turned on, to quench emission of said flash light in said flash discharge tube;
a turn-on capacitor for being charged in response to said emission of said flash light, and for being discharged when said integration voltage comes up to a prescribed level, to turn on said non-contact switch upon a pulse of discharge; and
a control switching element for keeping said reflected light measuring unit disabled while said turn-on capacitor is initially charged, and for enabling said reflected light measuring unit after voltage across said turn-on capacitor comes up to a predetermined level.
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Accused Products
Abstract
An electronic flash device of an automatic light adjusting type includes a main capacitor for storing charge at a high voltage. A flash discharge tube generates flash light upon discharging the main capacitor therewith. A light adjusting circuit adjusts a light amount of the flash light by feedback. The light adjusting circuit includes a reflected light measuring unit for outputting an integration voltage for representing a light amount of reflected light from a photographic field illuminated with the flash light. A thyristor as non-contact switch short-circuits terminals of the main capacitor upon being turned on, to quench emission of the flash light in the flash discharge tube. A turn-on capacitor is charged by a current of discharge in response to the emission of the flash light, and is discharged when the integration voltage comes up to a prescribed level, to turn on the thyristor responsively. A control transistor keeps the reflected light measuring unit disabled while the turn-on capacitor is initially charged, and enables the reflected light measuring unit after the integration voltage comes up to a predetermined level.
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Citations
14 Claims
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1. An electronic flash device of an automatic light adjusting type, including a main capacitor for storing charge at a high voltage, a flash discharge tube for generating flash light with a current upon discharging said main capacitor, and a light adjusting circuit for adjusting a light amount of said flash light, said flash device comprising:
wherein said light adjusting circuit includes;
a reflected light measuring unit for outputting an integration voltage for representing a light amount of reflected light from a photographic field illuminated with said flash light;
a non-contact switch for short-circuiting terminals of said main capacitor upon being turned on, to quench emission of said flash light in said flash discharge tube;
a turn-on capacitor for being charged in response to said emission of said flash light, and for being discharged when said integration voltage comes up to a prescribed level, to turn on said non-contact switch upon a pulse of discharge; and
a control switching element for keeping said reflected light measuring unit disabled while said turn-on capacitor is initially charged, and for enabling said reflected light measuring unit after voltage across said turn-on capacitor comes up to a predetermined level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
Specification