Vivitar Corporation

Jean M Orban

There is disclosed herein an electronic flash system which obviates the need for the typical large capacity main capacitor as the power source for the flashtube. The system includes a conventional flashtube, trigger circuit for ionizing the flashtube and control circuit for turning on and off an electronic switching element which applies the main operating power to the flashtube. The ignition circuit for the flashtube uses a relatively small capacitor which is charged to a high voltage level for first igniting the flashtube and causing it to commence emission of light. Once ignited, a medium voltage power supply supplies the necessary current level for the required length of time to continue the production of the flash of light. The system also enables the use of a relatively small electronic switch as well as a relatively small voltage converter for charging the ignition capacitor.

Electronic flash system

A device for activating an electronic slave flash unit for photographic use includes a circuit wherein there is a delay circuit responsive to a light sensing signal after a predetermined time delay to activate a flash unit. The time delay of the delay circuit is adjustable as required, and the delayed operation of the flash of the slave flash unit eliminates incorrect impulse signals being transmitted to light sensors of other slave flash units which would otherwise prematurely extinguish their flash and give a resultant incorrect lighting effect. The power for the circuit is obtained from a capacitor which is energized by a flash unit. The energy in the capacitor is used to power the delay circuit, and a Zener diode and unijunction transistor and variable resistance permit accurate variable time delays.

Electronic slave flash delay device

There is disclosed herein an electronic system and circuits for photographic devices for performing certain photographic calculation and control functions. In an exemplary embodiment, the system is particularly useful for performing metering, calculation and control of shutter timing and/or diaphragm aperture opening for a camera. The system includes a logarithmic converter for converting an electrical signal proportional to light intensity passing through the camera lens from a linear value to a log value, and a calculator responsive thereto and to other input parameters, such as film sensitivity, open aperture, selected aperture and selected shutter speed which, in turn, calculates an appropriate shutter speed and an appropriate aperture. The output of the calculator is connected to a circuit, which includes the log converter in a feedback loop for performing an antilog function and for controlling shutter speed and/or diaphragm aperture. The use of the same log converter for performing log and antilog operations provides compensation for errors inherent in the use of separate conversion circuits and improves accuracy and temperature stability to thereby insure accurate and stable metering. The calculator allows either or both of the shutter speed and diaphragm aperture to be calculated and controlled. In addition, a sample and hold circuit memorizes the exposure value EV to enable either shutter speed or aperture value to be changed while automatically compensating for the other.

Electronic system for photographic devices

There is disclosed herein an electronic system and display system for a camera. The electronic system receives various inputs pertaining to film speed, brightness, selected shutter speed and a relative aperture value, and provides outputs for control of shutter speed and aperture as well as display of these parameters. An electrical signal representing a relative aperture value is provided for the display system, and a mechanical input is provided to the display system representing a fixed aperture value, such as minimum aperture value or A.sub.o. The electrical and mechanical inputs are combined to provide a display of an absolute aperture value, such as computed aperture value A.sub.c. Details of the camera electronic system also are disclosed.

Display system for camera

Apparatus for converting a camera metering system from a manually set electronic metering system into an automatic, aperture-preferred metering system uses sensing means responsive to exposure signals provided by the metering system of the camera for providing a signal to drive means for automatically selecting the proper shutter speed.

Shutter speed selector accessory

There is disclosed herein a voltage regulator for a power supply for load devices such as electronic photoflash units. The voltage regulator supplies power to charge the main capacitor of the photoflash unit to an appropriate voltage, and uses a semiconductor series regulator circuit. The voltage regulator provides medium-to-long term heat integration to terminate power supplied to the electronic flash unit in the event of a thermal overload in order to protect the electronic flash unit. The circuit includes a ready indicator to indicate when the main capacitor of the flash unit has reached the appropriate charge, and also includes an overload indicator to indicate an overload condition.

Growing community of inventors

Santa Monica, CA, United States of America

Jean M Orban