Method for detecting muzzle flashes from light weapons by means of an infrared matrix photodetector, wherein - an infrared matrix photodetector is implemented that is sensitive in the MWIR band reacting to infrared radiation of which the wavelengths are between 3 and 5 μm and comprising a plurality of photosites, each of which forms a portion of the image of the landscape observed by the photodetector, each photosite being associated with a measuring circuit, and - the sequence of the following operations is carried out in the infrared photodetector: • acquiring, at a frequency of approximately 1000 Hz, successive images of the landscape in which said light weapons may be located, a portion of the current image being acquired in first storage means of a photosite of a measuring circuit, a portion of a preceding image being acquired in second storage means of a photosite of a measuring circuit, said photosite forming the corresponding portion of the current image and of the preceding image, • calculating the differences between each of said images and the preceding image, by means which are capable of discerning the difference between each portion of the current image and each portion of the preceding image, • storing said differences in third storage means, • thresholding said image differences by means of a threshold that is at least approximately representative of the noise of said landscape, by thresholding means in order to let past only the difference signals which are above the threshold, extracting only said differences in the image portions that are above said threshold, for unloading only the differences in the image portions that are above said threshold, • unloading, by an unloading device, only the differences in the image portions that are above said threshold, and • transferring to a user of the image-difference portions that have exceeded the threshold and are characterised by their coordinates (X and Y) on the photodetector and their intensity. - an infrared matrix photodetector is implemented that is sensitive in the MWIR band reacting to infrared radiation of which the wavelengths are between 3 and 5 μm and comprising a plurality of photosites, each of which forms a portion of the image of the landscape observed by the photodetector, each photosite being associated with a measuring circuit, and - the sequence of the following operations is carried out in the infrared photodetector: • acquiring, at a frequency of approximately 1000 Hz, successive images of the landscape in which said light weapons may be located, a portion of the current image being acquired in first storage means of a photosite of a measuring circuit, a portion of a preceding image being acquired in second storage means of a photosite of a measuring circuit, said photosite forming the corresponding portion of the current image and of the preceding image, • calculating the differences between each of said images and the preceding image, by means which are capable of discerning the difference between each portion of the current image and each portion of the preceding image, • storing said differences in third storage means, • thresholding said image differences by means of a threshold that is at least approximately representative of the noise of said landscape, by thresholding means in order to let past only the difference signals which are above the threshold, extracting only said differences in the image portions that are above said threshold, for unloading only the differences in the image portions that are above said threshold, • unloading, by an unloading device, only the differences in the image portions that are above said threshold, and • transferring to a user of the image-difference portions that have exceeded the threshold and are characterised by their coordinates (X and Y) on the photodetector and their intensity. • acquiring, at a frequency of approximately 1000 Hz, successive images of the landscape in which said light weapons may be located, a portion of the current image being acquired in first storage means of a photosite of a measuring circuit, a portion of a preceding image being acquired in second storage means of a photosite of a measuring circuit, said photosite forming the corresponding portion of the current image and of the preceding image, • calculating the differences between each of said images and the preceding image, by means which are capable of discerning the difference between each portion of the current image and each portion of the preceding image, • storing said differences in third storage means, • thresholding said image differences by means of a threshold that is at least approximately representative of the noise of said landscape, by thresholding means in order to let past only the difference signals which are above the threshold, extracting only said differences in the image portions that are above said threshold, for unloading only the differences in the image portions that are above said threshold, • unloading, by an unloading device, only the differences in the image portions that are above said threshold, and • transferring to a user of the image-difference portions that have exceeded the threshold and are characterised by their coordinates (X and Y) on the photodetector and their intensity.