US 3,938,365 A · Detecting trace gaseous species acoustically in response to radiation from an intense light source

Abstract

An intense light source, preferably of high monochromaticity, having its beam modulated at a frequency corresponding to an acoustical resonant frequency of a sample chamber energizes the sample chamber along its axis. A photoelectric detector provides a signal related to this modulation for comparison with an acoustical signal provided by a microphone in the sample chamber. Means are provided for adjusting the modulation frequency so that it corresponds to the acoustical resonant frequency of the sample chamber as determined by a maximum in the amplitude of the amplified acoustical signal. An integrator may respond to the amplified acoustical signal to provide an indication of the energy absorbed by the medium in the sample chamber at the light wavelength and thereby the concentration of certain species in the sample chamber.

Claims16

Dependent claims

Apparatus for detecting the presence of a species in a medium comprising,

means defining a sample chamber for receiving said medium,
a source of a beam of radiant energy incident upon said sample chamber for producing pressure waves therein of intensity related to the degree of absorption by said medium,
means modulating said beam at a rate corresponding to a predetermined resonant frequency of said means defining a sample chamber,
and acoustical detecting means for detecting the pressure wave signals produces in said sample chamber to provide an output signal representative of the degree of absorption of the medium in said sample chamber.

1 more element

Dependencies are inferred from the claim text.

Detecting trace gaseous species acoustically in response to radiation from an intense light source

Life of this patent

Detecting trace gaseous species acoustically in response to radiation from an intense light source

Life of this patent

Abstract

Claims16