Abstract

Consider a crosspoint array of thyristors. Initially all are off, and then one thyristor is turned on to give conduction from one row to one column. A peripheral array of diodes serves to encode just which row and column are conducting. The power may then be interrupted briefly to reset the thyristors. It is proposed that the thyristors be designed as avalanche photothyristors and that the device be moderately cooled and operated somewhat over the avalanche breakdown voltage as recommended by Ekstrom¹ for activation by individual photons. The result of obtaining photon positions is an imaging photon counter that should have three basic advantages over a CCD at extremely low light levels: lower background because of no readout noise; higher pictorial speed because of no raster scanning; and preservation of temporal sequence information for a posteriori dynamic image processing.

© 1988 Optical Society of America