Patent ID: 7196847
Filing Date: 2007-03-27
Classification: G02B,G02F

Abstract:
1. A spectral filter over a wavelength range comprising elements arranged in cascade along a light beam axis characterized by an entrance polarizer; at least a dispersive polarization rotator with the rotation angle varying as a function of light wavelength over said wavelength range; at least an orientation-sensitive polarization element; and means for rotating said orientation-sensitive polarization element(s) about said light beam axis or/and varying said rotation angle(s); whereby said polarization element or at least one of said polarization elements is a polarizer, said polarization rotator(s) and polarization element(s) are arranged behind said entrance polarizer along said beam axis to form tuner(s) such that said polarization element that is a polarizer works as the exit polarizer of said filter, and said filter has its spectral transmission determined by said rotation angle(s) and tunable by rotating said exit polarizer or/and the other(s) of said polarization element(s) about said beam axis and further tunable by varying said rotation angle(s); the filter being a single-stage spectral filter over said wavelength range comprising elements arranged in cascade along said light beam axis including an entrance polarizer ( a dispersive polarization rotator ( an exit polarizer ( means for rotating said exit polarizer about said light beam axis; whereby said polarization rotator ( the polarization rotator ( the filter having its spectral transmission determined by said Faraday rotation angle and tunable by varying said Faraday rotation angle or switchable by switching said Faraday rotation angle in at least two alternative states, further tunable by rotating said exit polarizer (