JPS5727600A - X-ray automatic exposure controller - Google Patents

Abstract

PURPOSE:To prevent the excessive or insufficient blackening of an X-ray photograph by extracting the picture signal of a photoelectron multiplier within its lighting visual field using the signal from a television camera controller and providing a correction circuit which corrects the operation of an automatic exposure controller. CONSTITUTION:An automatic exposure controller 12 is controlled by providing a correction circuit 31 which corrects the operation of the automatic exposure controller and is controlled by a TV camera controller 10 in the automatic exposure control system which detects the quantity of X-ray and performs the X-ray control. The correction circuit 31 applies a picture signal to a mean value circuit and determines whether the output level is positive or negative. It inputs also the signal to the positive or negative mean value circuit, calculates each output in an addition circuit, computes the ratio of the output to the mean value output in a division circuit, uses the output as the control signal of the automatic exposure control system. As a result, this can prevent effectively the excessive or insufficient blackening of an X- ray photograph when a lighting visual field is covered by a contrast medium and when the X-ray is directly incident on the field.