| 摘要 |
PURPOSE:To improve the S/N ratio of an output video signal, by controlling the output of signal voltage through a switch between fluoroscopy and digital subtraction modes. CONSTITUTION:In a fluoroscopy mode an indication is given to a remote control aperture 16 of an optical system from a control panel 26 of a video processor 24 for full open of the aperture 16 via a signal line A. At the same time, the gain of an amplifier 20 of a TV camera is designated by an analog switch so that a signal current is amplified up to a prescribed level of output to the amplifier 20 via a signal line B. Furthermore the beam voltage of an image pickup tube 18 is set at an optimum level by the switch disignation. While in a continuous or serial mode, the aperture value is designated by the aperture 16 via the line A so as to obtain such quantity of light that the signal current of the tube 18 has a full swing within a dynamic range. In addition, the gain is designated with switching to the amplifier 20 by an analog switch via the line B. At the same time, the beam voltage is also controlled, and the signal voltage of a level equivalent to that of a fluoroscopy mode is delivered. |
