Patent ID: 11972595
Assignee: OFFICE NATIONAL D'ETUDES ET DE RECHERCHES AEROSPATIALES
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 18:
19. The gas detector of claim 2, wherein the second acquisition means are adapted for providing, for each analysis band of the at least one analysis band, the background brightness temperature values according to one of the following ways:
from at least one spectral image which contains one background scene element of the background scene elements, which was captured by the optical channel of the image capturing unit dedicated to the analysis band, and which is declared or considered as having been captured when the field-of-view did not contain the target gas;
from at least one spectral image which contains one background scene element of the background scene elements and which was captured by one of the at least two optical channels of the image capturing unit for which the corresponding spectral band, called reference band, is contained in a spectral domain of transparency of the target gas or in which the target gas has a transparency greater than in each analysis band of the at least one analysis band, wherein the image processing unit is adapted for identifying a material of the one background scene element from said at least one spectral image captured for the reference band and for deducing the background brightness temperature values for the analysis band and for said one background scene element based on the ambient temperature value and a spectral emissivity value of the identified material for said one background scene element; and
from at least one spectral image which contains one background scene element of the background scene elements and which was captured by one of the at least two optical channels of the image capturing unit for which the corresponding spectral band, called reference band, is contained in a spectral domain of transparency of the target gas or in which the target gas has a greater transparency than in each analysis band of the at least one analysis band, wherein the image processing unit is adapted for producing the background brightness temperature values for the analysis band by using a linear regression based on a background brightness temperature value deduced from the at least one spectral image captured for the reference band.