PURPOSE: To improve reproducibility and make uniform the photoelectric sensitivity of a photoelectric screen by measuring and detecting the resistance of a base thin film, specifying this resistance within the fixed value, controlling evaporation, and maintaining deposition within the desired range.

CONSTITUTION: Power is supplied to the evaporation source 26 where antimony is fused to heating metal wires and the 26 is heated. The antimony is evaporated and a base thin film is coated on the input fluorescent screen. Then, power is supplied to the evaporation source 27 and the 27 is heated. Cesium is evaporated and the base thin film is bleached in this cesium vapor. By activating it, a photoelectric screen is obtained. While this base thin film is being formed, the antimony is also coated on the detection mechanism 28 and the resistance which is proportional to the evaporation thickness of antimony is formed. By measuring this resistance, the evaporation of antimony is controlled and its coating is made uniform.