Diaphragm control circuit for TTL automatic electronic flash
AssigneeOlympus Optical Co., Ltd.
InventorKazunori Mizokami
Life of this patent
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Abstract
A diaphragm control circuit associated with TTL automatic electronic flash is adapted to be used in a camera of the TTL direct photometry type and capable of photometry of light reflection from film surface. When the electronic flash is mounted on the camera for cooperation therewith, the diaphragm control circuit responds to a brightness of an object being photographed by automatically establishing an aperture value which produces an exposure period synchronized with the operation of the electronic flash. The diaphragm control circuit also assures that the aperture controlling operation takes place reliably over a given time interval so that an aperture value which is less by a given number of steps than the open value is established.
Claims10
A diaphragm control circuit for TTL automatic electronic flash for use in a camera of the TTL direct photometry type and capable of photometry of light reflection from a film surface, the camera having the capability to control the amount of light emission from an associated TTL automatic electronic flash;
- the diaphragm control circuit comprising:
- a TTL diaphragm control signal generator circuit responsive to a photometric value determined by the photometry of light reflection from a reflecting surface by producing a diaphragm control signal which is effective to establish a diaphragm aperture which assures a proper exposure with an exposure period which is synchronized with the operation of the electronic flash, the diaphragm aperture established being intermediate an open value and a minimum aperture;
- a network for producing a signal which delays the termination of an aperture controlling operation for a given time interval since the initiation of the aperture controlling operation whenever there is a signal indicative of one of two conditions including the use of the electronic flash such as an electronic flash charged signal and the initiation of a charging operation within the electronic flash;
- and a diaphragm driver circuit for driving an electromagnet which controls a diaphragm aperture in response to a logical combination of the diaphragm control signal and the delay signal.
A diaphragm control circuit for TTL automatic electronic flash for use in a camera of the TTL direct photometry type and capable of photometry of light reflection from a film surface, the camera having the capability to control the amount of light emission from an associated electronic flash, the diaphragm control circuit comprising:
- a TTL diaphragm control signal generator circuit responsive to a photometric value determined by the photometry of light reflection from a reflecting surface for producing a diaphragm control signal for establishing a suitable diaphragm aperture, the diaphragm aperture established being intermediate an open value and a minimum aperture;
- a network for producing a signal which delays the termination of an aperture controlling operation for a given time interval since the initiation of the aperture controlling operation whenever there is a signal indicative of one of two conditions including the use of the electronic flash such as an electronic flash charged signal and a signal indicating the initiation of a changing operation within the electronic flash;
- and a diaphragm driver circuit for driving an electromagnet which controls a diaphragm aperture in response to a logical combination of the diaphragm control signal and the delay signal.
Dependencies are inferred from the claim text.