| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a displacement measurement instrument capable of accurately measuring displacement, and a displacement measurement method for use in the same.SOLUTION: A first PD 31 outputs a current corresponding to the change in amount of light due to interference fringes of interference light 30 outputted from a pair of diffraction gratings 20, to an arithmetic circuit 40 as an output signal. A second PD 32 detects movement of the pair of diffraction gratings 20, namely, rectilinearly propagating light 24 being incoherent light independent of displacement X. The arithmetic circuit 40 corrects the signal inputted from the first PD 31, on the basis of a signal obtained by the second PD 32 to output a corrected value of displacement X. Since the light detected by the second PD 32 is incoherent light independent of the displacement X, the arithmetic circuit 40 can obtain an output variation of an LD 12 corresponding to the output signal of the second PD 32.</p> |
