Abstract: The heating of a tunable-acoustic optical filter (TAOF) results in a drift in the calibration of the TAOF as the acoustic-optical medium temperature varies. In practicing the invention, the TAOF is calibrated by combining it in tandem with a broad band light source and a cell containing a medium that absorbs light at a known wave number. The TAOF is tuned to minimize the light transmitted through the elements, thereby tuning the TAOF to the wave number of maximum absorption which is a calibrated standard.
Abstract: The heating of a tunable-acoustic optical filter (TAOF) results in a drift in the calibration of the TAOF as the acoustic-optical medium temperature varies. In practicing the invention, the TAOF is periodically locked to a reference wavenumber and a calibration correction is then derived and employed to keep the TAOF consistently accurate.
Abstract: Light passing through an etalon is divided into three beams, each beam being incident to the etalon at a different angle. Two of the beams are received by detectors which generates intensity representative signal for each beam. The difference between the beam intensities represents the error between the etalon's passband and the wavenumber of the received light.
Abstract: Apparatus for separating radiation due to Raman scattering from a background of fluorescence.A sample of freely rotating molecules is exposed to monochromatic radiation of a fixed plane polarization. The resulting Raman radiation will be strongly polarized while any fluorescence will be essentially non-polarized. Orthogonal components are sequentially received by a detector which responds with output signals. The difference in signals corresponds to the Raman intensity independent of fluorescence.
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