| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a wavelength variable filter equivalent to a multistage-structured Lyot filter, in which an increase in the length/scale of equipment is suppressed by decreasing the number of components, sharp and narrow-band characteristics of transmitting spectrum can be demonstrated in a wide wavelength band including short wavelength band. <P>SOLUTION: The wavelength filter 31 includes: a Babinet-Soleil phase plate 32 composed of two wedge-shaped birefringence plates 33 and 34 and has a fixed optical thickness between upper side and the lower side principal surfaces; first to fourth polarizers 35 to 38 and upper side reflection mirrors 39 and 40 provided to the upper side principal surface and a lower side reflection mirror 41 provided to the lower side principal surface. Incident light is multiply-reflected between the first to the fourth polarizers and the upper and the lower reflection mirrors, passes through the Babinet-Soleil phase plate, and is emitted. The phase difference between two adjacent polarizers along an optical path inside of the Babinet-Soleil phase plate is set at 2<SP>n-1</SP>×2π (here n: 1 to 3). <P>COPYRIGHT: (C)2010,JPO&INPIT |
