Abstract: The invention concerns a manufacturing process of a photocathode for an image intensifier tube.According to this process, the photocathode is made within the tube by depositing a photoelectric material on a conductive substrate by vacuum evaporation. During this operation, the optical transparency of the deposit is checked by illumination of this deposit by a light source. According to the invention, this light source is located within the tube and is protected from the vapors of the photoelectric material. In the prior art, this light source was located outside the tube and the illumination of the deposit was not sufficient.The invention has applications in the field of image intensifier tubes.