Patent ID: 6243170
Filing Date: 2001-06-05
Classification: G01J

Abstract:
A double pass etalon based spectrometer for making spectral measurements of a beam, said spectrometer comprising:A) a diffusing optic for directing light in said beam in a very large number of directions, to produce a diffuse beam;B) an etalon positioned in said diffuse beam and configured to transmit portions of said beam to produce a once transmitted beam having angularly separated spectral components;C) a retroreflector positioned to reflect at least a portion of said once transmitted beam back through said etalon to, produce a twice transmitted beam having angularly separated spectral components;D) a focusing optic;E) a light detector,F) a reflecting optic positioned to reflect at least a portion of said twice reflected beam through said focusing optic onto said light detector wherein spectral components of said beam are detected by said light detector;wherein said diffuse beam defines a primary polarization direction said reflecting optic is a polarizing beam splitter and said retroreflector is comprised of two intersecting reflected plates defining a cross-line at their intersection, said two plates being positioned at a 90 degree angle relative to each other and the cross-line of the said plates is positioned at an angle of about 45 degrees to the primary polarization direction of said diffuse beam.