Patent ID: 8749636

Claim:
A multi-band aperture filter for optically coupling to a focal plane array (FPA) of a camera, comprising: a substrate; a first spectral coating disposed on a first surface of said substrate, the first spectral coating arranged to pass a first longer wavelength band and a second shorter wavelength band; a phase matching coating disposed on a second surface of said substrate, the first and second surfaces of said substrate being mutually opposed to one another, wherein the phase matching coating is arranged to provide a reduction in a relative phase relationship between S and P polarization components of light passing through the phase matching coating; and a second spectral coating arranged to pass said longer wavelength band and block said shorter wavelength band, the second spectral coating disposed on the second surface of said substrate, wherein said second coating provides a larger aperture area for said longer wavelength band relative to an aperture area for said shorter wavelength band, wherein the phase matching coating comprises an inner annulus region on the first surface of said substrate relative to an outer annulus region defined by the first spectral coating on the first surface of said substrate.