| 摘要 |
PURPOSE:To obtain a highly accurate optical center position by calculating an optical output from a one-dimensional optical element array at the frequency of twice the driving frequency when the optical output is less than the threshold value, and also calculating the output at the driving frequency when exceeding the threshold value. CONSTITUTION:An optical image is projected to an array 10 by an optical system 100 and the output signal 20 from the array 10 is supplied to a voltage comparator 40 and compared with threshold voltage Vt 45. When the signal 20 is larger than the Vt 45, an output 27 is turned to ''1'', and when smaller than the Vt 45, an output 28 is turned to ''1''. Therefore, an FF 50 keeps the output at ''1'' until the output 27 is turned to ''1'' after receiving a start signal 39, and an FF 55 keeps the output at ''1'' until the output 28 is turned to ''1'' after turning the FF 50 to ''0'', so that two AND gates 61, 62 are opened until t1 and during t1-t2 to generate pulses with the frequency of twice the driving frequency until t1 and generate pulses with the driving frequency during t1-t2. These pulses are supplied to a counter 70 to detect the center position of the optical image at an element interval of a half of the original element interval of the one-dimensional photoelectric element array. |
