LIFE EXTENDER AND BRIGHT LIGHT PROTECTION FOR CCTV CAMERA SYSTEM WITH IMAGE INTENSIFIER

摘要

A camera system for operating in nighttime lighting conditions without additional illumination includes an input lens (60) for receiving incoming light representative of an image, an image intensifier tube (61) for receiving the image from the input lens and producing an intensified image and a video camera (64) for receiving the intensified image. The life of the intensifier tube can be extended by automatically controlling its gain. The gain is sensed in an unused region of the intensifier tube, and the voltage applied to the intensifier tube is controlled to provide a desired gain. In addition, the intensifier tube can be gated on and off with a prescribed duty cycle to extend its life. A frame is stored when the intensifier tube is gated on, and the stored frame is repeated when the intensifier tube is gated off to provide a continuous series of images. The intensifier tube can be protected against bright light by turning it off for a prescribed time when the video signal exceeds a reference level that corresponds to a bright light.