Automatic gain control device for electronic endoscope

An electronic endoscope apparatus that comprises an automatic gain control device, the automatic gain control device comprising:

• a controllable gain amplifier that amplifies image signals output by an imaging device comprising a plurality of pixels;
• an A/D converter that digitizes the amplified image signals;
• a detector that detects a status of digitized amplified reference image signals output by the imaging device when the imaging device captures images of a white-balance test accessory;
• and
• a gain control processor that, based on the detected status of the digitized amplified reference image signals, sets a gain of the controllable gain amplifier to a value such that a linear operating range of an amplified image signal corresponding to a pixel of the plurality of pixels, having a smallest linear operating range out of the plurality of pixels, is approximately equal to a tolerance range of the A/D converter.

An automatic gain control device for an electronic endoscope, comprising:

• a controllable gain amplifier that amplifies image signals output by an imaging device comprising a plurality of pixels;
• an image signal processor that processes the amplified image signals;
• a detector that detects a status of processed amplified reference image signals output by the imaging device when the imaging device captures images of a white-balance test accessory;
• and
• a gain control processor that, based on the detected status of the processed amplified reference image signals, sets a gain of the controllable gain amplifier to a value such that a linear operating range of an amplified image signal corresponding to a pixel of the plurality of pixels, having a smallest linear operating range out of the plurality of pixels, is approximately equal to a tolerance range of the image signal processor.