| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to lessen polarization dependence loss and to obtain a distinct peak. SOLUTION: At least the incident side transparent substrate 10a of two sheets of the incident side and exit side transparent substrates 10a, 10b of the wavelength selection filter F1 of a liquid crystal etalon 1 type constituted by holding liquid crystals 2 with two sheets of the incident side and exit side transparent substrates 10a, 10b laminated and formed with alignment layers 5, reflection films 3 and transparent electrodes 4 is constituted by joining an azimuth rotator 8a formed to a trapezoidal shape in section having a slope 9a inclining at an angle θ with the plane orthogonal with an optical axis X and having the angle θ1 of θ1>tan<-1> (180 deg./rotatory power/beam diameter) and a polarizer 6a. Collimated incident light is depolarized by the azimuth rotator 8a and is then transmitted through the polarizer 6a. Only the linearly polarized light acting as a variable wavelength filter may be transmitted into the filter. |
