X-ray image intensifiers are large diameter imaging tubes that convert low contrast images into visible light images, and are used in medical X-ray TV systems and non-destructive X-ray inspection systems. Due to a newly developed CsI input phosphor screen, Hamamatsu X-ray image intensifiers provide high DQE (detection quantum efficiency) and high-quality images. Furthermore, the use of an aluminum input window and the improvement in the output phosphor screen achieve a very high contrast. In particular, the high definition types offer superior spatial resolution that assures an exceptionally clear image even for microstructures in a stomach mucous membrane that have been previously obtained only with photographic film. In addition, the combination of new input/output phosphor screens and an electron lens designed by computer simulation allows high quality image even in the digital imaging method.