| 摘要 |
PURPOSE:To always stably obtain a good quality image, by starting the sampling of mask image data when the difference between the peak value of the present frame of a video signal and that of the previous frame thereof reaches a reference value or less. CONSTITUTION:A digital subtraction circuit A is interposed between the imaging tube 2 of an X-ray TV and a monitor display 10. The analogue video signal from the imaging tube 2 is inputted not only to the digital subtraction circuit A but also to a sampling start signal generating circuit B. The sampling start signal generating circuit B supplies a sampling start signal to the mask image frame memory 5 of the digital subtraction circuit A when the difference between the peak value of the present frame of an analogue video signal and that of the previous frame thereof reaches a reference value or less. By this method, the sampling of mask data is started immediately after the completion of the rising of the imaging tube 2. |
