Image Intensifier and Television Technique
David R. Hill · 1975
From Roentgen’s first experiment until about 1950, the only satisfactory method of viewing the X-ray image was with a fluorescent screen which emits light when X-ray quanta are absorbed. The intensity of the light emitted by the fluorescent screen is proportional to the rate of absorption of the X-ray quanta. The energy is transformed into heat and light; very little heat but a relatively large amount of light.