An infrared image sensor, comprising: - on a support , a plurality of first pixels and a plurality of second pixels intended to detect an infrared radiation emitted by an element of a scene, each pixel comprising a bolometric membrane suspended above a reflector covering the support, the reflector of each first pixel being covered with a first dielectric layer , and the reflector of each second pixel being covered with a second dielectric layer differing from the first dielectric layer by its optical properties; - a read circuit for reading out first values (V1, V2) representative of the temperatures of the bolometric membranes of first and second neighboring pixels; and - a processing unit adapted to determine the emissivity of the scene element based on the first values (V1, V2), the processing unit being configured to generate estimated temperature (Ti, T E ) and emissivity (Ei, E E ) values corresponding to a minimum of an error value representative of differences, the differences comprising: a first difference between the first value (V1) read from the first pixel and a second value (V1 TH ) representative of the temperature that the bolometric membrane of the first pixel would have according to a theoretical model if the temperature and the emissivity of the scene element had the estimated values; and a second difference between the first value (V2) read from the second pixel and a further second value (V2 TH ) representative of the temperature that the bolometric membrane of the second pixel would have according to a theoretical model if the temperature and the emissivity of the scene element had the estimated value. - on a support , a plurality of first pixels and a plurality of second pixels intended to detect an infrared radiation emitted by an element of a scene, each pixel comprising a bolometric membrane suspended above a reflector covering the support, the reflector of each first pixel being covered with a first dielectric layer , and the reflector of each second pixel being covered with a second dielectric layer differing from the first dielectric layer by its optical properties; - a read circuit for reading out first values (V1, V2) representative of the temperatures of the bolometric membranes of first and second neighboring pixels; and - a processing unit adapted to determine the emissivity of the scene element based on the first values (V1, V2), the processing unit being configured to generate estimated temperature (Ti, T E ) and emissivity (Ei, E E ) values corresponding to a minimum of an error value representative of differences, the differences comprising: a first difference between the first value (V1) read from the first pixel and a second value (V1 TH ) representative of the temperature that the bolometric membrane of the first pixel would have according to a theoretical model if the temperature and the emissivity of the scene element had the estimated values; and a second difference between the first value (V2) read from the second pixel and a further second value (V2 TH ) representative of the temperature that the bolometric membrane of the second pixel would have according to a theoretical model if the temperature and the emissivity of the scene element had the estimated value. a first difference between the first value (V1) read from the first pixel and a second value (V1 TH ) representative of the temperature that the bolometric membrane of the first pixel would have according to a theoretical model if the temperature and the emissivity of the scene element had the estimated values; and a second difference between the first value (V2) read from the second pixel and a further second value (V2 TH ) representative of the temperature that the bolometric membrane of the second pixel would have according to a theoretical model if the temperature and the emissivity of the scene element had the estimated value. <EOS>