| 摘要 |
PURPOSE:To perform automatic intensity adjustment with good contrast and easy to observe by detecting the maximum concentration level from a concentration histogram and increasing or decreasing the tube voltage to control it so that the maximum concentration level reaches the reference level. CONSTITUTION:A concentration histogram related with the picture element number data with various concentration levels is stored in a frame memory 7. An address generating circuit 9 updates addresses of the frame memory 7 in sequence during the vertical retrace line period and reads out the picture element number data of each concentration level and sends them to a maximum concentration value detecting circuit 12. The maximum concentration value detecting circuit 12 outputs the concentration level corresponding to the maximum picture element number data as the maximum concentration level date, it is inputted to one input terminal of a maximum concentration level voltage differential amplifier circuit 14 through a D/A converter 13. The preset reference voltage in the intensity level range is inputted to the other input terminal, they are compared, a tube voltage control circuit 15 is controlled so that the maximum concentration level is made equal to the reference level. Intensity adjustment with good contrast and easy to observe can be performed. |
