A spherical semiconductor photocell using lateral photoeffect

Previously, photocells using the lateral photoeffect for determining the direction to a light source within a small angle (one pair of contacts), or a small solid angle (two pairs of contacts), have been described. Here, a further development of the lateral photocell, in this case using spherical geometry and three pairs of contacts, is presented. This photocell allows measurement of the direction to a light source over nearly the entire 4φ solid angle. Because of the absence of p-n junction edges, distortion caused by edge effects is minimized. The cell does not need a lens system, as do planar lateral photocells, but without it the sensitivity is reduced.