Fuji Photo Film Company, Limited

Takeshi Kubota

Kazuo Kamata

Nobuyuki Kameyama

Hirokazu Yokoo

Akihisa Iida

Jun Ogawa

Katsumi Motomura

A flash device for a lens-fitted photo film unit pre-loaded with unexposed photo film is provided. A main capacitor stores charge. A flash emitter emits flash light. A flash circuit board charges the main capacitor, and drives the flash emitter by discharging the main capacitor in response to an exposing operation. A tightly closed flash case is secured to the lens-fitted photo film unit, for containing the main capacitor, the flash emitter and the flash circuit board. Also, the lens-fitted photo film unit includes a sync switch for generating a trigger signal in response to the exposing operation. Two switch contact points are disposed outside the flash case, for receiving the trigger signal from the sync switch. The two switch contact points disable discharge of the main capacitor while the flash case is away from the lens-fitted photo film unit, and are short-circuited for discharge of the main capacitor upon supply of the trigger signal while the flash case is secured to the lens-fitted photo film unit.

Lens-fitted photo film unit, flash device, and lens-fitted photo film system

A charging circuit includes an oscillation transformer and an oscillation transistor. The oscillation transistor oscillates at a secondary current returned from a secondary coil in the charging circuit. The oscillation transistor increases/decreases a primary current, which flows from a battery to a primary coil, and flows the secondary current through the secondary coil to charge a main capacitor. The oscillation transistor, which satisfies the following conditions, is used: a DC current gain his 500&#xb1;10 when a collector-emitter voltage Vis 2V and a collector current Iis 0.5 A, and a DC current gain his 290&#xb1;10 when the collector-emitter voltage Vis 2V and the collector current Iis 5 A.

Flash device and lens-fitted photo film unit with built-in flash device

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.

Growing community of inventors

Minami-ashigara, Japan

Takeshi Kubota