| 摘要 |
PROBLEM TO BE SOLVED: To obtain an edge detector not affected by transmissivity and the like of an object to be detected and capable of stable and accurate edge detection. SOLUTION: Light reception sensors 12a and 12b of which parts shifted to relative moving direction X of an object to be detected 14 are overlapping use a photo sensor 10 having two detection areas. The differential amplifier 21 consisting a maximum detection means 20 produces a difference signal C of each detection signal A, B detected by the reception sensors 12a and 12b. A differentiating circuit 23 produces a differential signal E of the difference signal C and a comparator 24 compares the value nearly in the center of the maximum value and the minimum value of the differential signal E and obtains an edge signal F before removing containing differential noise. An AND circuit 26 makes a logical product of an output D obtained by comparing the difference signal C and a specified level C0 with a comparator 25 and the edge signal F before removing. By this, noise pulse contained in the edge signal F before removing is removed. |
