WAVELENGTH TUNABLE BIREFRINGENT FILTER

摘要

A wavelength tunable filter (200) selectively transmitting light of any desired wavelength within the range of 450 nm to 1100 nm without using a band pass filter is disclosed. The wavelength tunable filter (200) comprises a plurality of polarizers (101a to 101f) and a plurality of units between the adjacent polarizers (101 a to 101f) on a common optical axis (111) in a housing (201). Each unit has, in order from light incident side, a quartz birefringent plate (102), an ultra-wide band 1/4 waveplate (103) and an ultra-wide band 1/2 waveplate (104). The ultra-wide band 1/2 waveplate (104) is accommodated in a cylindrical rotatable body (303; 403; 503) and it is rotated by a rotating mechanism.