Flash device, lens-fitted photo film unit, camera, and producing method for the same

A lens-fitted photo film unit comprising:

• a main body pre-loaded with photo film;
• 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.

A camera having a main body for being loaded with photo film, 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 contril 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.

A lens-fitted photo film unit producing method for producing a lens-fitted photo film unit, said lens-fitted photo film unit comprising:

• a main body pre-loaded with photo film;
• a front cover for covering a front side of said main body;
• 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;
• a flash circuit board having said booster circuit, said main capacitor, said flash discharge tube, said trigger circuit, said photo receptor element, said light amount control circuit, and said powering voltage generator circuit;
• a charging operation portion, disposed in said front wall, for being externally actuated, to turn on said flash circuit board;
• and
• a photometric window, formed in said front cover, for passing said reflected light from said object to said photo receptor element;
• said lens-fitted photo film unit producing method comprising steps of:
• securing said flash circuit board to said main body;
• securing said front cover to said main body in positioning said photometric window at said photo receptor element in said main body, and in positioning said charging operation portion at said flash circuit board in said main body.

A flash device comprising:

• an oscillation transformer, including primary and secondary windings coupled with each other in mutual induction, there occurring an induction current flowing in a secondary winding upon flowing of a current in said primary winding, said induction current adapted for charging a main capacitor;
• a flash discharge tube, triggered by application of trigger voltage, for emitting flash light by discharging said main capacitor being charged;
• a light amount control circuit for receiving said flash light reflected by an object to be photographed, and for quenching discharge of said flash discharge tube when an amount of said received reflected flash light comes up to a predetermined level;
• and
• a driving capacitor for being charged by back electromotive force generated in said primary winding, and for generating powering voltage adapted for powering said light amount control circuit in emitting said flash light.

A flash device comprising:

• an oscillation transformer, including primary, secondary and tertiary windings coupled with one other in mutual induction, there occurring an induction current flowing in a secondary winding upon flowing of a current in said primary winding, said induction current adapted for charging a main capacitor;
• a flash discharge tube, triggered by application of trigger voltage, for emitting flash light by discharging said main capacitor being charged;
• a light amount control circuit for receiving said flash light reflected by an object to be photographed, and for quenching discharge of said flash discharge tube when an amount of said received reflected flash light comes up to a predetermined level;
• and
• a driving capacitor for being charged by electromotive force of induction generated in said tertiary winding by changes in a current flowing in said secondary winding, and for generating powering voltage adapted for powering said light amount control circuit in emitting said flash light.