| 摘要 |
PROBLEM TO BE SOLVED: To provide an inspection device wherein accuracy of measurement distance and resolution are improved with the ruse of a frequency-variable light source by outputting control signal from a control circuit so that detection output of straight line sweeping error of light frequency of a light source becomes zero. SOLUTION: When inclination of variation of light frequency of the output of a light source 5 is constant (straight-line-swept), the frequency of the signal outputted from a photodetector 17 is constant. The signal outputted from the photodetector 17 is, with a phase comparator 19, compared with known frequency signal outputted from art oscillator 18 for frequency or phase. At this time, when the inclination of variation of modulation frequency does not constant, the error signal is outputted from the phase comparator 19. A lump wave generator 3 is provided with an integrator containing a calculation amplifier 28 and a register 25, and integrates the output current of a control circuit 20. Thus the output of the control circuit 20 is added to the integrator, so that the output of the phase comparator 19 is so closed-loop- controlled as to be zero, and the light frequency of the light source 5 is straight-line- swept with high accuracy. |
