Method and apparatus for remote optical detection of a gas present in an observed volume
First Claim
1. A method for remote optical detection of a gas, e.g. a polluting gas, present in an observed volume, the method comprising:
- detecting the radiant fluxes coming from at least two different temperature points of said volume, said fluxes passing through the looked-for gas and being detected through a first filter having a transmission band that includes an absorption line characteristic of the looked-for gas;
taking the difference between the fluxes detected through the first filter;
detecting the radiant fluxes coming from the above-specified two points through a second filter having a transmission band similar to that of the first filter and complementary to said absorption line of the looked-for gas;
taking the difference between the fluxes detected through the second filter;
taking the ratio of the above-specified differences; and
deducing possible presence of the gas in the observed volume from the value of said ratio.
1 Assignment
0 Petitions
Accused Products
Abstract
A method and apparatus for remote optical detection of a gas present in an observed volume using a thermal imager or camera including one or more sensitive elements which are sensitive to radiant fluxes in a determined band of wavelengths, two filters interposable on the optical axis of the camera, the filters having similar transmission bands, one of which includes an absorption line characteristic of the looked-for gas, while the other of which is complementary to said absorption line, and signal processing means for taking the difference between the radiated fluxes received from two points at different temperatures in the volume as observed first through one of the filters and then through the other filter, for taking the ratio of said differences, and for deducing therefrom whether the gas is present in the observed volume.
-
Citations
13 Claims
-
1. A method for remote optical detection of a gas, e.g. a polluting gas, present in an observed volume, the method comprising:
-
detecting the radiant fluxes coming from at least two different temperature points of said volume, said fluxes passing through the looked-for gas and being detected through a first filter having a transmission band that includes an absorption line characteristic of the looked-for gas; taking the difference between the fluxes detected through the first filter; detecting the radiant fluxes coming from the above-specified two points through a second filter having a transmission band similar to that of the first filter and complementary to said absorption line of the looked-for gas; taking the difference between the fluxes detected through the second filter; taking the ratio of the above-specified differences; and deducing possible presence of the gas in the observed volume from the value of said ratio. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
-
8. Apparatus for remote optical detection of a gas, in an observed volume, e.g. a polluting gas, the apparatus comprising:
-
a thermal imager or camera including at least one sensitive element sensitive to radiant fluxes in a determined band of wavelengths, and an optical system enabling an image of at least a portion of the observed volume to be formed on said sensitive element; at least two filters suitable for being interposed on the optical axis of the thermal imager or camera for detecting the radiant fluxes of the observed volume through each of the filters, said filters having similar transmission bands in the above-mentioned band of wavelengths, the band of one of the filters including at least one absorption line of the lookedfor gas and the band of the other filter being complementary to said absorption line; and signal processing means comprising means for selecting the signals provided by said sensitive element and corresponding to the fluxes from at least two points at different temperatures in the observed volume, the fluxes from these two points being detected through the looked-for gas, means for establishing the differences between the fluxes from these two points as detected through one and then the other one of the filters and means for taking the ratio of these differences. - View Dependent Claims (9, 10, 11, 12, 13)
-
Specification