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

Claim 0:
1. A gas detector for revealing at least one gas, called a target gas, which could be present in a field-of-view, wherein said gas detector comprises:
an image capturing unit which comprises at least two optical channels arranged in parallel for separately and simultaneously capturing respective images of one and same content of the field-of-view, called spectral images, in different spectral bands to which said at least two optical channels are dedicated one-to-one;
first acquisition means adapted for providing an ambient temperature value intended to be attributed to a quantity of the target gas which is present in the field-of-view between a background scene and the image capturing unit;
second acquisition means adapted for providing, for at least one spectral band of the different spectral bands, called at least one analysis band, background brightness temperature values which are intended to be attributed to elements of the background scene;
an image processing unit arranged for receiving the spectral images captured by the at least two optical channels of the image capturing unit and adapted for deducing, separately for each analysis band of the at least one analysis band, an evaluation of a radiation transmission coefficient which relates to said analysis band, and which is attributed at least partially to a quantity of the target gas present in a part of the field-of-view between the background scene elements and the image capturing unit, based on an equation which combines:
the ambient temperature value;
the background brightness temperature values which are intended to be attributed to the background scene elements in the part of the field-of-view, for said analysis band; and
at least one brightness temperature value, called at least one apparent brightness temperature value, which corresponds to the spectral image captured for the analysis band, in said part of the field-of-view; and

a calculation unit adapted for deducing an evaluation of the quantity of the target gas which is present in the part of the field-of-view based on a value of the radiation transmission coefficient which relates to an analysis band of the at least one analysis band,, wherein the first acquisition means are adapted for providing the ambient temperature value according to one of the following ways:
based on at least one part of a spectral image which was captured by one of the at least two optical channels of the image capturing unit, said at least one part of the spectral image corresponding to a sector of the field-of-view declared or considered as being free of the background scene elements; and
based on at least one part of a spectral image which was captured by one of the at least two optical channels of the image capturing unit whose associated spectral band is contained in a spectral domain of complete opacity for a gas which is present in a sector of the field-of-view corresponding to the at least one part of the spectral image;, wherein the gas detector is adapted for capturing the spectral image at least a part of which is used in order to provide the ambient temperature value at a same time or during a same image capturing sequence as the spectral image of each analysis band of the at least one analysis band, wherein the image processing unit then combines said ambient temperature value with said at least one brightness temperature value of said spectral image of each analysis band of the at least one analysis band;, and wherein the first acquisition means, the second acquisition means, the image processing unit and the calculation unit are implemented by at least one processor.