Olympus Optical Company, Ltd.

Hiroaki Nakamura

Juro Kikuchi

Toshifumi Nakano

Isao Kondo

Tatsuji Higuchi

Akira Inoue

A flash device comprises a pre-flash circuit which conducts a small flash a plurality of times for reducing the pupil size in response to a camera release signal just before the commencement of the shutter opening operation and a main flash circuit for conducting flash for taking a picture after the commencement of shutter opening operation.

Flash device

A camera having a red-eye alarm device which receives a signal representative of a distance l between an object to be photographed and a camera, the focal length f of a taking lens, a signal representative of a distance d between the optical axis of the taking lens and the center of an electronic flash discharge tube, and develops an alarm signal based upon the object distance l, the focal length f and the spacing d, the red-eye alarm signal being developed when a conditional formula ##EQU1## is satisfied.

Camera having a red-eye forecasting and/or preventing device

An electronic flash includes a main capacitor having a discharge loop in which a circuit arrangement including a flash discharge tube, a switching element and an emission controlling capacitor is connected. During the time the flash discharge tube is maintained excited, the emission controlling capacitor is either charged or discharged to cause an emission of flashlight from the flash discharge tube.

Electronic flash

An electronic flash of series controlled type is provided. It comprises a series connection of a flash discharge tube and a main thyristor, which series connection is further connected in series with a thyristor which forms a reverse charging path for a commutating capacitor. The series combination of the flash discharge tube, the main thyristor and the last mentioned thyristor is connected in parallel with a main capacitor. A diode is connected in series with the commutating capacitor so that their series combination is in parallel with the reverse charging thyristor. The reverse charging thyristor is rendered conductive as the main thyristor is rendered conductive so as to establish a reverse charging path for the commutating capacitor therethrough when a commutating operation is to be performed. This prevents a reverse charging current to the commutating capacitor from passing through the flash discharge tube, thus enabling an accurate control over the amount of exposure produced by flashlight.

Electronic flash of series controlled type

An electronic flash unit of the dynamic flat flash type includes a flash control circuit which produces a flash termination signal by detecting the fact that a value associated with pulse flashes reaches a predetermined level and further produces a flash resumption signal within a period of time less than the deionization time of a flash discharge tube after the flash termination signal has been produced. With the flash control circuit, the electronic flash unit permits the discharge tube to repeatedly emit a pulse flash during an exposure operation of a shutter of a camera so that the flash characteristics substantially equivalent to a continuous flash can be obtained.

Electronic flash units

A series controlled electronic flash of automatic emission control type includes a switching element connected in series with a commutating switching element for selectively charging a commutation capacitor. A trigger signal is repeatedly applied to a main switching element, the commutating switching element and the charging switching element in a given sequence to enable a continued emission at substantially constant brightness level to be obtained from a flash discharge tube. A trigger capacitor may be connected with pair of switching elements for charging and discharging the trigger capacitor. A trigger signal may be repeatedly applied to the pair of switching elements for charging and discharging the trigger capacitor, to the main switching element, to the commutating switching element and the commutation capacitor charging switching element in a given sequence, thereby allowing a multiple emission to be obtained intermittently and at a high rate from the flash discharge tube.

A photometry power supply for automatic electronic flash comprises an impedance element through which part of the charge stored across a main capacitor of the electronic flash discharges to develop a voltage thereacross which may be used as a power supply for a photometric circuit.

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Hachioji, Japan

Hiroaki Nakamura