Photoelectric direction finder

A photoelectric direction finder for detection and angular location of a light-radiating target, comprising:

• optical reception means for focusing radiation coming from an observed field;
• optical filtering means for selection of the radiation received from said target;
• reticle means in the form of a revolving disc centered on the optical axis of said optical reception means and having a reticle pattern on one planar surface thereof for modulating and spatial filtering of the focused radiation, the reticle pattern being located substantially in the focal plane of the optical reception means and comprising at least one optical circular track formed of a uniform array of alternate opaque and transparent radially extending sectors to modulate said radiation at a determined modulation frequency;
• detection means comprising a four quadrant detector at a distance from said reticle means, and an intermediate optical objective for transposing the focused field image on said detector;
• means for relative movement of the assembly comprising said optical reception means and said reticle means with respect to said detection means, by rotation around an instantaneous center of rotation which coincides substantially with the center of said detector;
• and
• circuits for processing and deviation measurement of four reception channels issued from said detection quadrants respectively, to demodulate the signals detected and produce deviation signals representing the angular offset of the target direction with respect to a reference measurement axis.