Accuracy of position detection using a position-sensitive detector

Position-sensitive detectors (PSD) provide four current outputs that are pr oportional to the two-dimensional center of mass of a light spot impinging on the face of the detector. This characteristic permits the PSD to be used for sensing the position of a light source. The application motivating the work reported here involved the tracking of a light source located on a su rface with approximate dimensions 122 cm wide by 91 cm high located approxi mately 2 m from the detector. The diameter of the light source was a few mi llimeters. The work described here demonstrates the feasibility of using a PSD to track the position of a light source with accuracy better than 1 mm from this distance.