Performance of the position sensitive photodetector with early stage digitizing of the photocurrents

Analog circuits processing PSD currents and calculating position value introduce errors of significant magnitude and demand separate circuits for amplitude and phase detection methods, thus prohibiting full use of the PSD's potential. In order to demonstrate PSD capabilities, a high performance electronics circuit has been constructed that digitizes PSD photocurrents and calculates position value using DFT from both amplitude and phase methods. Verification of the total system error has been independently carried out using Michelson interferometer. Comparison of both detection methods offers better insight into their potential use. Experimental results qualify PSD as detector capable of 100 nm displacement resolution in direct illumination setup.