Electronic flash control system and method for high-speed flashing
AssigneeNikon Corporation
InventorHiroshi Sakamoto
Life of this patent
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Abstract
An electronic flash control system and method for a high-speed repeating flash having a main capacitor which stores energy for flashing, a discharge element, a switching apparatus, a control unit and a photometric unit. The switching apparatus causes the discharge element to flash multiple times during the exposure operation of the camera based on a signal from the control unit generated in accordance with the duty ratio. The duty ratio for each flash is determined by the control unit based on a signal from the photometric unit representative of the quantity of light from the previous flash of the discharge element. As the control system does not perform real-time control, delays of the control system do not adversely affect accuracy.
Claims12
An electronic flash control system for causing a discharge element to flash multiple times based on a variable duty ratio during an exposure cycle of a camera, the control system comprising:
- a main capacitor;
- a discharge loop associated with the discharge element;
- a photometric unit for outputting a signal corresponding to the quantity of light emitted from the discharge element and received by the photometric unit;
- and
- a switching apparatus connected to said discharge loop and including
- a control unit adapted to output a control signal based on the duty ratio which causes the discharge element to turn on and off, said control system varying the duty ratio based on said photometric unit signal.
A method of controlling an electronic flash system during the exposure period of a photograph comprising:
- emitting light from the electronic flash system for an initial predetermined period;
- measuring the light received during the emission of the electronic flash system;
- computing an appropriate time period for next emission of the electronic flash system based on a quantity of light required for the photograph and the light received during the prior emission of the electronic flash system;
- triggering the electronic flash device for said appropriate period;
- and
- repeating the method from the step of measuring the light until the exposure period expires.
Dependencies are inferred from the claim text.