| 摘要 |
PURPOSE:To achieve a higher accuracy and reliability, by providing a lock-on decision unit which compares the output of a peak value detector with the maximum of hourly changes in the output of an A/D converter as outputted from a fine coefficient detector to output a lock-on signal. CONSTITUTION:Light scanned by a radial scan optical system 2 is quantized in N bits (N: natural number) through a light receiving element 3, a sampling device 5 and an F/D converter 7 and a signal 8 is outputted. Then, the maximum of hourly changes in the signal 8 and the time thereof are determined with a fine coefficient detector 9 and a maximum edge level signal 36 is outputted to a lock-in decision unit 39 while a target position signal 10 is outputted to a coordinate converter 11. On the other hand, the difference between the maximum and minimum of the signal 8 is detected with a peak value detector 37 and a peak level signal 38 is outputted to the decision unit 39. Then, when the signals 36 and 38 are inputted into the decision unit 39 to meet a specified formula, a lock-on signal 40 is outputted and only when the signal 40 is inputted, the signal 10 is converted with a converter 11 into target position signals 12 and 13 to be outputted.
|
