PURPOSE: To obtain a densitometer capable of suppressing the effect of contamination on an output signal to a reduced degree, by providing a correction signal generation circuit capable of arbitrarily selecting positive and negative polarities and amplitude.
CONSTITUTION: When the line 3 connecting the valleys of an electric wave form projected on the screen surface of a monitor is inclined by an angle αwith respect to a reference horizontal axis 4, density difference by decoloration irregularity is generated so as to traverse a specimen support sheet. A saw-tooth wave correction signal having polarity and amplitude sufficient to set off said inclination is generated by a correction signal generation circuit and superposed to the output signal of an image pick-up element. By this method, a relatively accurate measured result can be obtained without receiving the effect by the contamination of a sheet too much. This densititometer correction signal generation circuit consists of a saw-tooth wave signal generation circuit 19 and a switch circuit 20 and, when the switch circuit 20 is held to an open state, a saw-tooth wave correction signal with polarity and amplitude selected by a variable resistor 22 is outputted.
OIKE YOSHIKAZU
ISHIDA YASUNORI
