Patent ID: 6633728
Filing Date: 2003-10-14
Classification: G03B,H05B

Abstract:
A flash device comprising:a booster circuit including primary and secondary windings, said secondary winding generating high voltage when power source voltage is applied to said primary winding; a main capacitor for being charged by said high voltage in said secondary winding; a flash discharge tube, connected in parallel with said main capacitor, for emitting flash light upon discharge with electric energy from said main capacitor; a trigger circuit for discharging said flash discharge tube upon a switching operation; a photo receptor element for measuring reflected light from an object illuminated by said flash light, to output a light amount signal; a light amount control circuit for quenching discharge of said flash discharge tube when an integration value of said light amount signal comes up to a predetermined value; a powering voltage generator circuit, connected with said secondary winding, for generating powering voltage adapted for powering said light amount control circuit in response to operation of said trigger circuit; wherein said light amount control circuit comprises: a first capacitor arranged in the light amount control circuit to integrate said light amount signal; a first switching element electrically connected with respect to the first capacitor so that the first switching element becomes conductive when a voltage across said first capacitor comes up to said predetermined value; a second capacitor separate from the first capacitor, and electrically connected so that the second capacitor can be charged by application of said powering voltage, and also electrically connected so that the second capacitor is discharged when said first switching element becomes conductive; a second switching element electrically connected so that it becomes conductive upon discharge of said second capacitor, the second switching element being further electrically connected so that, when conductive, it discharges the main capacitor, thereby quenching emission of said flash light from said flash discharge tube.