Abstract: Preprocessor for the detection of point sources in an infrared (IR) "scenario" or field, essentially consisting of an input interface; a transversal filter; an adaptable threshold device, consisting in turn of a two-port internal memory and of an arithmetic processing unit; a resource assembly and an output interface. The system can be used in surveillance in the IR band, more particularly, in the field of detection of signal emission on ships, planes, helicopters, transportation means, armored cars, airports and anywhere it is necessary to detect artificial or natural heat sources from as far away as possible. In comparison with the prior art, the preprocessor differs from the point of view of the filtering system, adjusting the filter itself to the real form of the IR signal which is punctiform and depends on the electro-optic characteristics of the sensor.