Photoelectric direction finder

A photoelectric direction finder system for the detection and the location of a light radiating target, of the type comprising an optical reception and focussing objective, a revolving disk rotated in the focal plane of the objective and provided with reticles formed from transparent and opaque zones for producing a modulation whose frequency is linked with the rotation speed, an optical filter, a photodetector device for the modulated radiation and circuits for the processing and deviation measurement of the detected signals, comprising demodulating circuits and producing deviation signals which are representative of the angular offsetting of the target relative to a reference axis, and in which an intermediate deviation measurement objective is positioned between the reticles and the detector, the latter being of the four quadrant type for producing the deviation signals from the respective signals of the quadrants and consecutively separating the deviation measurement function from the modulating and spatial filtering function produced by the reticles, wherein the reticles are determined transparent to the radiation produced by an auxiliairy laser illuminator modulated with a modulation which is separate from that produced by the reticles and wherein it comprises additional processing circuits for processing the detected laser signals, as well as circuits for switching and selecting passive and semi-active operating modes for delivering the corresponding deviation measurement data.