Video camera apparatus having solid state imager

An apparatus for detecting an absence of light incident on a solid state imaging means having an effective accumulating period and having different operating modes, said apparatus comprising:

• electronic shutter control means for controlling the effective accumulating period of said solid state imaging means and for varying the mode of said solid state imaging means between at least a first mode and a second mode, the effective accumulating period of said solid state imaging means in said first mode being of different temporal duration than the corresponding period in said second mode such that said solid state imaging means produces video signals having voltage levels which are a function of the accumulating period;
• a comparator means for comparing the voltage level of the video signal obtained in said first mode with that obtained in said second mode so as to produce a difference between the voltage levels of the video signals obtained in said first and second modes;
• and
• means for detecting the absence of incident light when the difference between the voltage levels of said video signals is less than a predetermined voltage level.

A method for detecting an absence of light incident on a solid state imaging means having an effective accumulating period controlled by electronic shutter control means, said method comprising the steps of:

• generating a voltage level of a video signal derived from said solid state imaging means in a first effective accumulating period;
• generating a voltage level of a video signal derived from said solid state imaging means in a second effective accumulating period which is of different temporal duration than said first effective accumulating period;
• producing a difference between voltage levels of the video signals obtained in said first and said second effective accumulating periods;
• and
• detecting the absence of incident light when the difference between the voltage levels of said video signals is less than a predetermined voltage.