| 摘要 |
PURPOSE:To accurately know the change in a physical quantity, by extracting only the change in intensity by interference from a third intensity signal by performing predetermined operation on the basis of first, second and third intensity signals. CONSTITUTION:A controller 14 allows a polarizer 12 to rotate through the driving of a motor and, by this rotation, the polarizer 12 can take three kinds of angles, that is, a first angle wherein the polarization plane of straight polarized light emitted by the polarizer 12 becomes parallel to the F-axis 20 of a double refraction material 16, a second angle wherein the polarization plane of said straight polarized light becomes parallel to a S-axis 22 and a third angle wherein the polarization plane of said polarized light similarly takes 45 deg. to both of the F-axis 20 and the S-axis 22. A controller 14 informs the any setting angle of the polarizer 12 to an arithmetic unit 26 and attains the correspondence to the intensity signal having been inputted to the operation circuit 26. The intensity I of light is given by formula and the change in the value of cos(phiF-phiS) in the formula indicates the change in a physical quantity being a measuring amount and, in the arithmetic unit 26, only the value of cos(phiF-phiS) is calculated from intensity signals S1-S3. |
