Seikosha Co., Ltd.

Youichi Seki

Nobuo Shinozaki

Shigeru Tagami

Masuo Ogihara

Shinji Nagaoka

Hiroshi Yamazaki

Michio Taniwaki

Hiroyuki Ishida

Hiroyuki Saito

Tadashi Nakagawa

Michio Kawai

An analog-to-digital converter for a camera has a reference signal generating element, a measurement signal generating element, and pulse output means for generating pulses of pule durations corresponding respectively to signals from the generating elements. The generating elements are alternately selected to produce two pulse durations, and the ratio of these two durations is computed by pulse duration ratio computing means. Control information corresponding to the computed ratio is retrieved from memory means.

Analog-to-digital converter for camera

A drive ring drivable by a stepping motor is normally urged by a spring to turn in one direction around a lens aperture. When not in use, the stepping motor is not subjected to the resilient force from the spring since the drive ring is locked against rotation by a ratchet wheel engaged by an engagement lever. The stepping motor is therefore not subjected to undue stresses and is prevented from malfunctioning. Consequently, focusing failures and exposure adjustment failures which could otherwise arise from malfunctioning of the stepping motor are prevented from occurring. In operation, a solenoid is energized to move the engagement lever out of engagement with the ratchet wheel, which is then freed to allow the drive ring to be turned by the stepping motor.

Motor-driven shutter for camera

A camera shutter has an automatic focusing lens operative when actuated to effect an automatic focusing operation. An actuating ring is normally placed in a non-operating region and momentarily shifted to an operating region during the automatic focusing operation. The actuating ring is sequentially displaceable in forward and reverse direction through the operating region to actuate the automatic focusing lens, and displaceable in the forward and reverse directions in the non-operating region without effecting actuation of the automatic focusing lens. A ratchet mechanism is coupled to the actuating ring for selectively locking and unlocking the actuating ring in the non-operating region in response to the displacement thereof in the forward and reverse directions. A bi-directionally rotatable stepping motor is connected to drive the actuating ring to displace the same in the forward and reverse directions.

A program shutter has a plurality of shutter sectors driven in opening and closing directions by a reversible stepping motor to define a lens aperture during an exposure operation. An arithmetic circuit calculates an exposure amount corresponding to the brightness of the object being photographed, and a counting circuit outputs a pulse count corresponding to the number of steps through which the stepping motor should be rotated based on the calculated exposure amount. A pulse circuit produces driving pulses equal in number to the number of steps determined by the counting circuit, and a time circuit determines the ON/OFF periods of the driving pulses based on the calculated exposure amount. The driving pulses are applied to the stepping motor through a driving circuit to accordingly drive the shutter sectors in the opening and closing directions during the exposure operation.

Program shutter

A power circuit for a camera comprising a power activation means containing a release switch for activating the camera, a step-up means for starting to step up the voltage of a battery by the power activation means, a CPU which is driven by an output of the step-up means so as to control the operation of the camera and which has a reset terminal for stopping the operation, and a voltage detecting means for detecting the output voltage of the step-up means and for generating a detection signal when the voltage is lower than a set value which has previously been determined, the set value being set to correspond to the limiting operation voltage of the CPU and, when the output voltage of the step-up means is lower than the limiting operation voltage of the CPU, the CPU being reset and stopped to operate.

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Yotsukaido, Japan

Youichi Seki