Patent ID: 6717967
Filing Date: 2004-04-06
Classification: G01J,G02B,H04B

Abstract:
An absolutely calibrated optical filtering device for filtering a light beam, comprising:a periodic filter having a frequency response including a plurality of substantially regularly-spaced spectral features; a filter stabilizing assembly, comprising: an absolute reference filter having a transmission spectrum which includes at least one absolutely known absorption feature; a tunable laser source generating a primary light beam at a tunable frequency, at least a portion of said primary light beam being filtered by the absolute reference filter to generate a reference filter beam, and at least a portion of the primary light beam being filtered by the periodic filter to generate a periodic filter beam; means for separately obtaining a reference filter signal and a periodic filter signal from the reference filter and periodic filter beams respectively; laser locking means connected to the tunable laser source, wherein the reference filter signal is adapted to lock the frequency of the tunable laser source relative to a selected one of the absorption features of the absolute reference filter; and filter stabilizing means connected to the periodic filter, wherein the periodic filter signal is adapted to the frequency response of said periodic filter by locking one of the spectral features thereof relative to the frequency of the tunable laser source; an input receiving the light beam and propagating the same through the periodic filter, thereby generating a filtered light beam according to the frequency response of the periodic filter; and an output outputting the filtered light beam independently of the periodic filter beam.