Optics: measuring and testing – Inspection of flaws or impurities – Bore inspection
Patent
1976-08-13
1977-11-22
Corbin, John K.
Optics: measuring and testing
Inspection of flaws or impurities
Bore inspection
356 51, 356206, 250343, G01N 2122
Patent
active
040593568
ABSTRACT:
A methane detector comprising a He-Ne laser in which the plasma tube forms a portion of the resonant cavity and the laser can be stimulated to emit at two different atomic resonances at separate wave numbers .nu..sub.1 and .nu..sub.2, one of which is more strongly absorbed by methane than the other. Means such as a beam splitter disposed in the resonant cavity, are provided for directing two beams outwardly from the cavity to a pair of detectors each provided in the path of a respective beam. The cavity is tuned so that its length L meets the criterion m/2L = .nu..sub.1 -.nu..sub.2, m being a number of half integers. Means are provided for cyclically varying the gain of the laser across one free spectral range through some tuned center value.
REFERENCES:
patent: 3539804 (1970-11-01), Billetdeaux et al.
patent: 3547524 (1970-12-01), Javan et al.
patent: 3856406 (1974-12-01), Noble et al.
patent: 3860888 (1975-01-01), Stephens
patent: 3869613 (1975-03-01), Link et al.
patent: 3893771 (1975-01-01), Bell
Moore, C. B., "Gas-Laser Frequency Selection by Molecular Absorption," Applied Optics, vol. 4, No. 2, Feb. 1965, pp. 252-253.
Bergman, et al., "A New Cascade Laser Transition in He-Ne-Mixture," Physics Letters, vol. 29A, No. 2, 7 Apr. 1969, pp. 94-95.
Corbin John K.
Environmental Research & Technology, Inc.
Rosenberger R. A.
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