Patent ID: 9625628
Date: 2017-04-18
CPC Classifications: G01J,G02B

Claim:
1. An optical filter comprising: an upstream laterally variable bandpass optical filter; and a downstream laterally variable bandpass optical filter; wherein the downstream laterally variable bandpass optical filter is sequentially disposed downstream of the upstream laterally variable bandpass optical filter and separated by a distance L along an optical path of an optical beam, wherein the upstream and downstream laterally variable bandpass optical filters each have a bandpass center wavelength that gradually varies in a mutually coordinated fashion along a first direction transverse to the optical path, thereby providing for each bandpass center wavelength having a same dependence, and wherein a dependence of spectral selectivity of the optical filter on a degree of collimation of the optical beam is less than a corresponding dependence of spectral selectivity of the downstream laterally variable bandpass optical filter on the degree of collimation of the optical beam.