JP2531170B

PURPOSE:To reduce expense, by detecting the fluctuation of input between an image sensor and a control circuit, and also, compensating the fluctuation for the sensor. CONSTITUTION:A signal detected by the image sensor 1 is inputted to a plotting detection circuit 3 via the control circuit 2, and is compared with a level set in advance, and afterwards, it is converted to a DC signal corresponding to the sensitivity of the sensor. A converted output is inputted to an adder 5 as a correction signal for a signal outputted from the control circuit 2, and the signal corrected by the adder 5 is added on a stabilization circuit 4, and is outputted from the stabilization circuit 4. In such a way, it is possible omit an expensive sensor to detect the color and the density of plotting and a complicated control circuit, and to reduce the expense required for adjusting work remarkably.