Patent ID: 7570426
Filing Date: 2009-08-04
Classification: F41H,G01J,G02B,G08B

Abstract:
1. An apparatus for wide-angle narrowband filtering of optical energy comprising: an optical entrance window for admitting light to the apparatus; a first polarizer to determine a first polarization state of light transmitted through the first polarizer and separated a first distance no less than zero from the optical entrance window along a central optical axis; a second polarizer oriented to substantively block light having the first polarization state and separated a second distance, greater than the first distance, from the optical entrance window along the central optical axis; a narrowband polarization-changing material disposed between the first polarizer and the second polarizer; and an optical exit window for transmitting light away from the second polarizer separated a third distance, no less than the second distance, from the optical entrance window along the central optical axis; wherein whereby the apparatus transmits light in the narrow wavelength range in each of a plurality of directions up to the maximum acceptance angle around the central axis and a tangent of the maximum acceptance angle is equal to half of a reciprocal of the aspect ratio and the maximum acceptance angle is greater than 7 degrees; and wherein: wherein: wherein: wherein: