| 摘要 |
PURPOSE:To have the optimum control of diaphragm for a TV camera and to eliminate a zoom lens, by mixing the video signal given from a TV camera main body with the DC signal that is rectified and smoothed by the 1st circuit and then with the DC signal rectified and smoothed by the 2nd circuit after elimination of the low frequency component. CONSTITUTION:A video signal (a) supplied from an input terminal 10 is inverted and amplified by an inverting/amplifying circuit 11 of a luminance detecting circuit of an automatic diaphragm device. This inverted and amplified video signal (b) is rectified through a diode D1 of the 1st signal processing circuit12 and then smoothed by a capacitor C2 and a resistance R3. At the same time, the signal (b) is applied to an HPF of the 2nd signal processing circuit 13, and a signal (d) with elimination of the low frequency component is rectified by a diode D2 and then smoothed by a capacitor C3 and a resistance R4. The rectified and smoothed mean value detecting signal (c) and peak value detecting signal (e) are mixed together by a mixing circuit 14. Thus a luminance detecting signal (f) is delivered through an output terminal 15 and fed to a level control circuit. Then the diaphragm of a camera is cotrolled in an optimum way. |
