Fluorescence detector for monitoring atmospheric pollutants

Claim 2

A remote measuring device for monitoring pollutant gases in an atmospheric area including the subject pollutant gases, which area is located at a site remote from the measuring device, said measuring device comprising: an infrared coherent radiation source adapted to excite fluorescence radiation in said pollutant gases at said atmospheric area; filter means at said measuring device for blocking infrared radiation from said coherent radiation source and passing said fluorescence radiation from the excited pollutant gases; a gas cell means in the path of said fluorescence radiation passed by said filter means, said gas cell means containing a standard sample of a known pollutant gas to be monitored for absorbing the fluorescence associated with said known gas and passing the remaining fluorescence; a neutral cell means in the path of said fluorescence radiation passed by said filter means for passing all of said fluorescence including the fluorescence of the type absorbed by said gas cell means; photodetector means, in response to fluorescence received from said gas cell means and said neutral cell means, for emitting an electrical difference signal indicative of the magnitude of the particular pollutant gas being monitored; and signal detecting means in circuit with said photodetector for detecting the electrical difference signal.

Claim 3

The remote measuring device of claim 1 and further comprising: output means connected to said signal detecting means and responsive to said detected signal for indicating the magnitude of said particular pollutant gas being monitored.

Claim 4

The measuring device of claim 2, wherein said detecting means further comprises: an amplifier connected to said photodetector means; demodulating means in circuit with said amplifier; and an integrator connected to said demodulating means for providing A direct voltage to said output means.

Claim 5

The measuring device of claim 3, wherein said infrared coherent radiation source comprises a laser.

Claim 6

The measuring device of claim 4 and further comprising: a chopper positioned between said cells and said photodetector; a reference oscillator; and a motor connected to said reference oscillator and rotating said chopper, said motor being synchronized by the fundamental frequency of said reference oscillator.

Claim 7

The measuring device of claim 5, wherein said reference oscillator is connected to a harmonic generator having a second output frequency at a harmonic of said fundamental frequency, and wherein said laser is a pulsed laser, and further comprising: means for applying said second output frequency from said generator to said laser as a pulsing signal.

Claim 8

The measuring device of claim 6 wherein said amplifier includes an AC amplifier connected to the output of said photodetector.

Claim 9

The measuring device of claim 7 and further comprising: a signal shaping circuit connected to the output of said AC amplifier and driven by said second output frequency to synchronize the output signal from the shaping circuit with said pulsed laser.

Claim 10

The measuring device of claim 8 and further comprising a tuned amplifier connected between said signal shaping circuit and said demodulating means, said amplifier tuned to the reference oscillator frequency.

Claim 11

The measuring device of claim 2 wherein said output means comprises a strip chart recorder.

Claim 12

In a remote receiver for detecting the fluorescence signatures of several pollutant gas molecules in a gas mixture excited by a pulsed infrared laser, the combination of: an optical filter adapted to block the infrared wavelength of said exciting laser and passing the fluorescence signatures radiated by the pollutant gas molecules; a gas cell positioned to be illuminated by radiation passed by said optical filter, said gas cell having a first compartment and a second compartment; a pollutant gas sample of a particular pollutant gas to be monitored in said first compartment, and a neutral gas in said second compartment; a photodetector adapted to be illuminated by radiation passing through said gas cell; motor driven chopper means positioned between said gas cell and said photodetector for enabling a variable radiation signal from said first and second compartments to be passed to said photodetector; a waveform eductor in circuit with said photodetector; a synchronizing reference oscillator having a first, fundamental frequency output connected to said motor driven chopper, and a second, harmonic frequency output connected to said laser and to said waveform eductor, whereby said chopper, said laser and said waveform eductor are synchronized; a tuned amplifier connected to the output of said waveform eductor; a synchronous demodulator and an integrator in circuit with said tuned amplifier to produce a direct voltage output corresponding to the amount of said particular pollutant gas; and a strip chart recorder responsive to said direct voltage output for providing a visual record of the magnitude of said particular pollutant gas.

Claim 13

In a remote receiver for detecting the fluorescence signatures of several pollutant gas molecules in a gas mixture excited by a pulsed infrared laser, the combination of: an optical filter adapted to block the infrared wavelength of said exciting laser and passing the fluorescence signatures radiated by the pollutant gas molecules; a gas cell positioned to be illuminated by radiation passed by said optical filter, said gas cell having a first compartment and a second compartment; a pollutant gas sample of a particular pollutant gas to be monitored in said first compartment, and a neutral gas in said second compartment; a photodetector adapted to be illuminated by radiation passing through said gas cell; motor driven chopper means positioned between said gas cell and said photodetector for enabling a variable radiation signal from said first and second compartments to be passed to said photodetector; a waveform eductor in circuit with said photodetector; a synchronizing reference oscillator having a first, fundamental frequency output connected to said motor driven chopper, and a second, harmonic frequency output connected to said laser and to said waveform eductor, whereby said chopper, said laser and said waveform eductor are synchronized; a tuned amplifier connected to the output of said waveform eductor; a synchronous demodulator and an integrator in circuit with said tuned amplifier to produce a direct voltage output corresponding to the amount of said particular pollutant gas; and a strip chart recorder responsive to said direct voltage output for providing a visual record of the magnitude of said particular pollutant gas.

Claim 14

A remote gas measuring device for monitoring pollutant gases in an atmospheric area of interest, said device comprising: a laser means for causing unknown pollutant gases in said atmospheric area to fluoresce; means for receiving the fluorescence of said pollutant gases; means at said receiving means including a standard known pollutant gas for absorbing the fluorescence associated with said known pollutant gas in the received fluorescence of pollutant gases while passing the fluorescence associated with other pollutant gases in the received fluorescence of pollutant gases; means for passing the fluorescence of all of the pollutant gases received at said receiving means, including the fluorescence associated with the standard known pollutant gas; and difference means responsive to said standard known pollutant gas fluorescence absorbing means and said passing means for emitting a signal indicative of the quantity of the standard known pollutant gas in the atmospheric area being monitored.

Claim 15

A remote gas measuring device for monitoring pollutant gases in an atmospheric area of interest, said device comprising: a laser means for causing unknown pollutant gases in said atmospheric area to fluoresce; means for receiving the fluorescence of said pollutant gases; means at said receiving means including a standard known pollutant gas for absorbing the fluorescence associated with said known pollutant gas in the received fluorescence of pollutant gases while passing the fluorescence associated with other pollutant gases in the received fluorescence of pollutant gases; means for passing the fluorescence of all of the pollutant gases received at said receiving means, including the fluorescence associated with the standard known pollutant gas; and difference means responsive to said standard known pollutant gas fluorescence absorbing means and said passing means for emitting a signal indicative of the quantity of the standard known pollutant gas in the atmospheric area being monitored.