New approach to raising the resolution of position sensitive detector with moving current-voltage characteristic

Position sensitive detectors (PSD) are widely applied for determining the coordinate of an optical signal and continuously tracking it. Currently, studies concerned with the possibility of further raising the spatial resolution of PSDs remain topical. In this paper, we present the results obtained in reaching an ultrahigh resolution for a device based on the PSD Multiscan with an integral operation principle which fundamentally differs from that of the lateral PSD. The PSD Multiscan design is based on an array of back-to-back photodiodes. Its optical signal coordinate read-out is formed via the moving current-voltage characteristic of the sensor directly on the PSD as an output potential proportional to the coordinate of the optical spot median. This measurement principle provides a continuous comparison of near-equal photocurrents, which maintains a high signal-tonoise ratio over the whole sensing area. The absence of computational operations in electronic circuits of the PSD Multiscan makes it possible to introduce a nonlinear amplifier element, which substantially improves the resolution of the device based on the sensor developed in the study (as good as 0.05 mu m). It has been shown that the resolution remains high for detectors with different lengths and is independent of the position of the optical spot on the sensing area.