Image pickup apparatus

Claim 1

An image pickup apparatus which comprises: light source means for providing an illumination light; an endoscope including illumination means coupled to said light source means for transmitting the illumination light from said light source means to a foreground subject to be illuminated; and image transmission means for sensing an optical image of the foreground subject illuminated by said illumination means and for transmitting the optical image; image signal conversion means coupled to said image transmission means of said endoscope for converting the optical image into a video signal; clamp means coupled to said image signal conversion means for clamping the black level of said video signal to provide a clamped signal; and integrator means coupled to said clamp means and to said light source means for integrating said clamped signal to continuously provide averaged information of said video signal to said light source means to continuously set the amount of illumination light provided by said light source means in accordance with said averaged information; said light source means, illumination means, image transmission means, image signal conversion means, clamp means and integrator means jointly comprising an automatic level control loop which is continuously actuated so at to continuously set amount of illumination light in accordance with said averaged information to cause said video signal to be at a substantially constant prescribed level; said automatic level control loop further comprising comparator means coupling said image signal conversion means to said clamp means for comparing the level of the video signal with that of a reference potential and for generating an output signal when the video signal reaches a level corresponding to the reference pontential; and said clamp means clamping said output signal of said comparator means at a prescribed level and at a predetermined timing.