The dependence of sensitivity of the selenium-sulphur rectifier photo-electric cell on the obliquity of the incident light, and a method of compensation therefor

The paper describes an investigation of the loss of sensitivity of the selenium-sulphur rectifier photoelectric cell with increasing obliquity of the incident light. When a restricted portion only of the surface of the cell is illuminated, it is found that the sensitivity increases as the centroid of the illuminated area is displaced from the centre of the cell. This permits of a simple method of compensation for the fall in sensitivity at oblique incidence, comprising the use of a central stop arranged at a suitable distance above the surface of the cell.