초록 ▼

A simple optomechanical method and apparatus is described for substantially reducing the amplitude of unwanted multiple-interference fringes which often limit the sensitivities of tunable laser absorption spectrometers. An exterior cavity is defined by partially-transmissible surfaces such as a lase

A simple optomechanical method and apparatus is described for substantially reducing the amplitude of unwanted multiple-interference fringes which often limit the sensitivities of tunable laser absorption spectrometers. An exterior cavity is defined by partially-transmissible surfaces such as a laser exit plate, a detector input, etc. That cavity is spoiled by placing an oscillating plate in the laser beam. For tunable diode laser spectroscopy in the mid-infrared region, a Brewster-plate spoiler allows the harmonic detection of absorptances of -5 in a single laser scan. Improved operation is achieved without subtraction techniques, without complex laser frequency modulation and without distortion of the molecular lineshape signal. The technique is applicable to tunable lasers operating from UV to IR wavelengths and in spectrometers which employ either short or long pathlengths, including the use of retroreflectors or multipass cells.

대표청구항 ▼

Apparatus for reducing interference fringes which are present in a passive cavity defined by partially-transmissible optical surfaces in a tunable laser absorption spectrometer, said apparatus comprising: a transmissive plate means adapted for oscillation and located in the laser\s optical beam; and

Apparatus for reducing interference fringes which are present in a passive cavity defined by partially-transmissible optical surfaces in a tunable laser absorption spectrometer, said apparatus comprising: a transmissive plate means adapted for oscillation and located in the laser\s optical beam; and means for oscillating said plate means over an angle selected to cancel the interference fringes.