Patent ID: 7362489
Filing Date: 2008-04-22
Classification: G02B,G02F

Abstract:
1. A spectral imaging filter, comprising: at least two spectral filter stages coupled along an optical signal path, wherein each of the at least filter stages has a periodic transmission characteristic with bandpass peaks separated by free spectral bandpass gaps; wherein each of the filter stages comprises a set of birefringent retarders and at least one polarizer, and the birefringent retarders in the set of at least one of said stages is characterized by retardation that is different from a retardation of the birefringent retarders in at least one other of the stages, such that said one of the at least two filter stages has a greater free spectral range than the other of the two filter stages, between the bandpass peaks of said one of the filter stages, and said other of the two filter stages has narrower bandpass peaks than said one of the two filter stages; wherein the bandpass peaks of said at least two filter stages overlap in an operative state of the filter, whereby a transmission characteristic of the spectral imaging filter as a whole is characterized by said greater free spectral range and said narrower bandpass peaks.