Electronic endoscope apparatus having magnification changing function

Abstract

The present invention provides an electronic endoscope apparatus which prevents a picked up image from being blurred utilizing an optical magnification change mechanism. A viewing distance is changed by moving a movable lens with an actuator, magnification changing location of the movable lens is detected with an encoder and a shutter speed for a CCD which is shorter than an exposure time while the optical magnification changing mechanism is not operating is set with a CPU dependently on the magnification changing location. It is possible to prevent an image from being blurred, for example, by storing various patterns which provide higher electronic shutter speeds as an image magnification ratio is enhanced in a ROM and controlling an electronic shutter speed with these patterns. Furthermore, a variable width of a stop is limited to a predetermined width as the electronic shutter speed is enhanced and a gain of a video signal is enhanced with an AGC circuit when image brightness is insufficient due to limitation of a variable width of the stop. When an electronic magnification changing circuit is provided, a displacement speed of optical magnification change is detected on the basis of magnification changing data detected with the encoder, and control is performed at the same speed as this speed so that a shift is made to an electronic magnification changing operation.