Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Patent
1993-05-04
1994-12-13
Hannaher, Constantine
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
25033901, 25033912, 250340, 250347, 250349, G01N 2117, G01N 2135
Patent
active
053731603
ABSTRACT:
Gases such as pollutants are discerned in the open air, preferably using a laser to emit an infrared light beam along a sight path for illuminating the gases. A telescope is directed along the sight path and collects light from the gases, the combination of the laser and telescope permitting redirection of the sight path to any target, such as fugitive emissions of a stack. An optical tunable filter is coupled to the telescope for selecting a particular optical wavelength or band, and focusing the filtered wavelength on a detector. A processor 72) is coupled to the detector output and pulses the laser. The processor analyzes the light levels as a function of wavelength to discriminate for the presence of selected gases by determining a characteristic pattern of light absorption and light emission by the gases. The tunable filter has an acousto-optical crystal of Tl.sub.3 AsSe.sub.3, in which an RF acoustic wave is generated for varying diffraction of light by the filter, thereby selecting a wavelength. A nonlinear output crystal selectively generates harmonics for increasing wavelength coverage, and can also be Tl.sub.3 AsSe.sub.3. When the laser is off, the filter acts on infrared emissions of the gases. Sensitivity to narrow emission lines is increased by modulating the RF drive to the tunable filter, producing derivatives of the spectra.
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Glick Edward J.
Hannaher Constantine
Westinghouse Electric Corporation
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