| 摘要 |
PURPOSE:To detect surface displacement with high precision regardless of the asymmetry of the waveform of reflected light by detecting the set direction of a measurement objective surface from a mean value calculated from the number of kinds of threshold values of generation time intervals of a reference and a reflected signal. CONSTITUTION:Clock pulses of frequency/2 are counted in the rising period of the reference signal of a reference photodetecting element 24, and clock pulses of frequency/2 are counted in the falling period of the reference signal and the rising period of the reflected signal of a reflected light detecting element 28; and they are added together by an adder 78 to calculate precisely surface displacement as the number of pulses corresponding to the intermediate point between the reference and reflected light regardless of the asymmetry of the reflected light. Further, threshold values Va, and Vb1-Vb3 are varied according to the peak value of the reference or reflected signal to take a precise measurement regardless of variations in the crest value of an output signal de to scattered light, power source variation, etc. |
