| 摘要 |
PURPOSE:To perform automatic dimming at a high speed corresponding to abrupt variation in brightness by adjusting the quantity of illumination light to a subject according to the sum of the output of a detecting means which detects abrupt variation in the quantity of light to the entire screen and the output of an image pickup means. CONSTITUTION:The illumination light from the lamp 30 in a light source unit 12 is guided to the tip of an endoscope 10 through a light guide 16 to light the subject. Then a subject image incident from an objective 18 is picked up by a solid-state image pickup element CCD22 and the brightness of the subject image in one screen is detected by a photodetecting element SBC24. The output of the CCD22 is passed through a video circuit 34 and integrated by the LPF42 of a dimming circuit 36, and then supplied to the 1st input terminal of an adder 46. The detection signal of the SBC24, on the other hand, is differentiated by an HPF50 and supplied to the 2nd input terminal of the adder 46. Then, the output of the adder 46 is supplied to a stop driving circuit 54 to control a stop 32, thereby dimming the illumination light.
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