| 摘要 |
PURPOSE:To prevent decline of the resolution of a high-luminance object and to surely realize a light reducing action by means of a photosensitive member, by providing a dimming member made of an interative photosensitive material which is sensible to an invisible light ray in an optical system provided with an aperture diaphragm which controls brightness and, at the same time, an irradiating means which irradiates the dimming member. CONSTITUTION:A image by photographing lenses 1 and 2 is formed on the image pickup surface of an image pickup tube 4. A signal processing circuit 5 processes the signal of the image pickup tube 4 and sends the processed signal to a TV receiver as video signals but part of the signals is inputted in an aperture diaphragm controlling motor 7 through a control circuit 6 and controls an aperture diaphragm 3 so as to maintain the video signal level constantly. A plane parallel plate 8 made of a photochromic material is provided at the back of the aperture diaphragm 3 closely to the diaphragm 3. An optical path dividing prism 9 equipped with a dichroic film which reflects ultraviolet rays is provided in front of the diaphragm 3 and a lens can be put between the prism 9 and diaphragm 3. An ultraviolet-ray source 10 is turned on and off or its luminance is changed by the control circuit 6. |
