Patent ID: 8351033

Claim:
A tunable filter comprising: a polarization splitter operable to split input light into two linearly polarized orthogonal light rays; a wavelength dispersion spectroscopic element operable to split the two linearly polarized light rays split by the polarization splitter, into two spectral images having spatial spread in one direction, the two spectral images corresponding to the two linearly polarized light rays; and a reflective spatial modulator device operable to modulate and reflect linearly polarized light in each wavelength region for the two spectral images independently from each other, wherein the modulated light reflected at the reflective spatial modulator device reenters the wavelength dispersion spectroscopic element and the polarization splitter, thereby splitting and outputting the modulated light, as output light in a wavelength region modulated by the reflective spatial modulator device and output light in a wavelength region not modulated, input light and reentered light to the polarization splitter and input light and reentered light to the wavelength dispersion spectroscopic element are parallel light fluxes, and principal rays of the two spectral images are incident vertically to the reflective spatial modulator device.