The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 30, 1989
Filed:
Dec. 23, 1987
Norifumi Nakagawa, Tokyo, JP;
Junichi Matsumoto, Tokyo, JP;
COPAL Company Limited, Itabashi, JP;
Abstract
A drive current of a motor is controlled by an output of a pulse oscillator having a variable duty ratio in response to a shutter release operation. Shutter blades having the function of the diaphragm blade start to open the aperture for exposure in interlocked relationship with the rotation of the motor. The shutter blades are provided with a plurality of detection marks for use in detection of the shutter blade position, and every time each of the detection marks passes through a predetermined detection point, an aperture value detection circuit produces a detection pulse. Each of the detection pulses is supplied to an operation circuit which calculates a time interval between the detection pulses. The time interval between the detection pulses is compared with a reference time stored previously in a setting device so that the duty ratio of the output signal of the pulse oscillator in the next cycle of the detection pulse is controlled to control the rotational speed of the motor. Further, the duty ratio of the pulse oscillator is made equal to 100% so that the motive power at the initial operation is secured until the aperture value detection circuit produces a first detection pulse.