Solid-state imaging apparatus provided with automatic iris control means

摘要

A solid-state imaging apparatus has an optical iris and a CCD imaging device which responds to light received from an object for producing a picture signal component and a reference black level signal component. A limiter limits the amplitude of the black level component to less than a predetermined value and the amplitude of the reference black level signal component is higher when the CCD imaging device is receiving such a quantity of light that the electric charges generated by photo-charge conversion in the light-sensitive elements in the CCD imaging device may not overflow from the light-sensitive elements. The limited amplitude is lower than the amplitude of the reference black signal component when the electric charges generated by photo-charge conversion in the light-sensitive elements overflow from the light-sensitive elements. A clamp circuit clamps the output from the CCD imaging device derived after passing through the limiter so that the reference black level signal component may take a predetermined voltage. An iris control circuit responds to the output of the clamp circuit for controlling the optical iris when the electric charges generated by photocharge conversion in the light-sensitive elements in the CCD imaging device have overflown from the light-sensitive elements. The signal level of the reference black level signal component output from the limiter may be restored to the signal level of the reference black level signal component when the electric charges generated by photocharge conversion in the light-sensitive elements in the CCD imaging device do not overflow. The same conditions arises in the reproduced picture, at the moment when an excessively large quantity of light would be received by human eyes. Hence, a viewer of the reproduced picture does not have an unnatural feeling.