| 摘要 |
PURPOSE:To detect surely the peak position of a position detecting sensor consisting of a light emitting element and a photodetector with a position detector which detects the positional relation between said sensor and an object to be inspected such as a film or the like by performing addition and subtraction of biasing current in the stage before amplification of a voltage signal. CONSTITUTION:A stabilized DC power source is supplied from a stabilizing power source circuit 63 to a light emitting element 61 and a photodetector 62 constituting a sensor 60. The output current (detection signal) PS from the detector 62 is applied as an addition signal to a current adder 101 and the fixed biasing current FB from a fixed biasing circuit 106 is inputted as a subtraction signal to the adder 101 and at the same time a variable biasing current VB is inputted as an addition signal thereto from a variable biasing circuit 105. A computer 100 has a CPU110 and a memory 120. The CPU110 compares the data DV from an AD converter 104 and reference values S0, S1 inputted from a keyboard, etc., feeds a bias control signal BC to the circuit 105 and outputs a sensor moving signal SM to the driving mechanism of the sensor 60. Processing with a high SN ratio is thus made possible and the peak value of the sensor detection signal is surely and exactly measured. |
