Method and apparatus for accurate remote monitoring of gases

Claim 1

Apparatus for accurate remote monitoring of the concentration of a target gas, which includes; first and second gas filter correlation channels both operating at a first spectral wavelength and each having an output terminal; differential amplifier means having first and second input terminals coupled to respective ones of said output terminals of said first and second gas filter correlation channels for producing a first output signal which represents the target gas but requires correction for ambient conditions; a corrective channel operating at a second spectral wavelength substantially different from said first spectral wavelength for producing a second output signal representative of said ambient conditions; signal multiplying means coupled to said differential amplifier means and to said corrective channel for multiplying said first and second output signals to produce a target-gas concentration signal, said pair of gas filter correlation channels and said corrective channel being optically aligned to receive radiant energy from a common source region; and, means to utilize said gas concentration signal.

Claim 10

The method of accurately and remotely measuring, for a region being observed, the concentration of a target gas having, under natural conditions, a high absorption at a predetermined first spectral wavelength, which includes the steps of: collecting radiant energy from said region to be observed; chopping said radiant energy in a cylical manner to produce cylically chopped radiant energy; splitting said chopped radiant energy into first and second beams of chopped radiant energy, one at said first spectral wavelength and the other at a second spectral wavelength significantly different from said first spectral wavelength; passing said first beam of chopped radiant energy thru a narrow-bandpass filter centered at first wavelength; processing said first beam, after it passes thru said narrow-bandpass filter, in a pair of gas filter correlation channels to produce a first processing signal and a second processing signal, respectively; differentially amplifying said first processing signal and said second processing signal to produce a first output signal representative of all energy received from said region to be observed at said first spectral wavelength; processing said second beam in a third channel to produce a second output signal which is representative of the difference between background radiant energy and atmospheric radiant energy at said second spectral wavelength; multiplying said first output signal by said second output signal, at any instant, to produce an instantaneous target-gas concentration signal; and, summing said instantaneous target gas signals over a chopping cycle.

Claim 11

The method of accurately and remotely measuring, for a region being observed, the concentration of a target gas having, under natural conditions, a high absorption at a predetermined first spectral wavelength, which includes the steps of: collecting radiant energy from said region to be observed; chopping said radiant energy in a cylical manner to produce cylically chopped radiant energy; splitting said chopped radiant energy into first and second beams of chopped radiant energy, one at said first spectral wavelength and the other at a second spectral wavelength significantly different from said first spectral wavelength; passing said first beam of chopped radiant energy thru a narrow-bandpass filter centered at first wavelength; processing said first beam, after it passes thru said narrow-bandpass filter, in a pair of gas filter correlation channels to produce a first processing signal and a second processing signal, respectively; differentially amplifying said first processing signal and said second processing signal to produce a first output signal representative of all energy received from said region to be observed at said first spectral wavelength; processing said second beam in a third channel to produce a second output signal which is representative of the difference between background radiant energy and atmospheric radiant energy at said second spectral wavelength; multiplying said first output signal by said second output signal, at any instant, to produce an instantaneous target-gas concentration signal; and, summing said instantaneous target gas signals over a chopping cycle.