The Luminescent Profile of a Scanning Electron Beam on a Fast Decay Phosphor Screen

摘要

Film scanning CRTs are used to transfer images into digital format by scanning the image with an intense,broad band,spot of light and analysing the output in the three RGB colour channels.The spatial resolution of the system is dependent on the size of the spot interrogating the film and is optimised by using a small spot size and a fast response phosphor to minimise the distortion of the spot profile produced by the finite rise and decay of luminescence in the phosphor.The effects of finite rise and decay on the spot profile of a moving electron beam have been calculated and the spatial MTF curves determined for various scanning speeds,spot sizes and phosphor decay times.The phosphors commonly used are P46 and P47 and their modifications,with decay constants of 30 -60 nsec.