PICTURE SIGNAL CORRECTING METHOD IN PICTURE INPUT DEVICE

摘要

PURPOSE:To realize picture signal correction easily with high accuracy by using a representative value of an output value at dark state of each element and a value after correction of a dark current of a photo sensor so as to apply correcting operation for both reading of a real picture signal and reading of a refernce signal. CONSTITUTION:A picture being a reference of a white level is read from a multi-element photo sensor 1 ahead the reading of a read picture at first. A value of photo sensor output signal which is shielded the light and included in a sensor output signal is detected by a DC lamp circuit 3 at a timing of t0, this value is held in a sample-and-hold circuit 11, the value is used as a representative value of an output at dark state, and this representative value is subtracted from the sensor output voltage by a substraction circuit 12. The remaining value after subtraction is used as a correction reference signal and stored in an RAM6 through a switch 10. In reading a real picture, the switch 10 is opened and the correction reference signal stored in the RAM6 is read sequentially by using the read request signal.