JPS561660A - Reading method - Google Patents

Abstract

PURPOSE:To ensure the decision for the proper threshold level even with the picture image having a low contrast and high noise each, by deciding the threshold level statistically and based on the picture information. CONSTITUTION:At the scanning time when scanning line SL goes and comes back, the picture signal sent from image pickup element 4 is quantized through A/D con- verting circuit 6 and then applied to decoder circuit 7 to obtain the corresponding output. Counters 80-831 are counted up by the sampling signal synchronized with the picture element of the picture signal when the output of circuit 7 is supplied. And the value is stored in sequence into adder circuit 9 starting at counter 80. Comparator circuit 10 delivers the output to control circuit 11 when the cumulative value of circuit 9 exceeds the fixed number of the entire picture element number, and then supplies the output to buffer circuit 12. Thus the input value of circuit 12 becomes to the threshold level. Then the picture signal sent from circuit 6 is compared with the threshold level given from circuit 12 at comparator 13 and at the going and coming back scanning time, and then binary-coded. In this way, the signal preserving memory becomes unnecessary.