Document Type and Number:
Japanese Patent JPS5172331
Kind Code:
A
Abstract:
The output of a bridge circuit which is unbalanced when the quantity of light falling on a light-sensitive element is less than or more than a predetermined light quantity is applied to a differential amplifier circuit whose output varies from a minimum amplitude to a maximum amplitude. The output of the differential amplifier is connected to a first and second threshold circuit whose threshold values are symmetrical to the output value of the differential amplifier when the bridge is in balance. The gain of the differential amplifier is adjusted so that the differential output signal has an amplitude exceeding the first threshold value and less than the second threshold value for variations of light within an allowable range. Within this range the first threshold circuit furnishes an output signal and the second threshold circuit does not. When the first threshold circuit does not furnish an output signal or if the second threshold circuit does, a pulse generator is energized whose pulses are counted by a counter which is controlled to energize the windings of the stepmotor controlling the diaphragm aperture in pairs in a predetermined sequence for opening and the reverse sequence for closing the diaphragm. The operation of the pulse generator and thereby of the motor is impeded when a switch furnishes a signal indicating that the diaphragm is fully open.
Inventors:
EDOARUTO UAGENZONNAA
AROOISU RIIDAA
BERUNHARUTO FUON FUITSUSHERUN
AROOISU RIIDAA
BERUNHARUTO FUON FUITSUSHERUN
Application Number:
JP13357275A
Publication Date:
June 23, 1976
Filing Date:
November 06, 1975
Export Citation:
Assignee:
AGFA GEVAERT AG
International Classes:
G03B19/18; G03B7/085; G03B7/095; G03B7/10; G05D25/00; (IPC1-7): G03B7/10; G05D25/00