The article offers a method for determining image intensifier working view field purity. In order to solve this problem, it is suggested to automate control under view field purity by using application program package. The automatic control is supposed to get an image of working view field and carry out its further processing by computer means. It allows to determine a permissible zonal amount of points and spots, as well as sizes and locations of light and dark defects. The article presents an algorithm for image intensifier view field purity level control developed by the authors simplifies control by means of measuring instruments and auxiliaries provided by GOST. It shows the results of field-emission bright point defect control and the view field purity level within the working field of a photocathode using a source of light.