Three tube color projection television system having at least one tube without an interference filter

摘要

A projection television system having three cathode ray tubes one of which has a display window, a fluorescent material layer disposed on the innermost surface of the display window, and a multilayered interference filter disposed between the display window and the fluorescent material layer. The multilayer interference filter is composed of a number of alternate layers of high refractive index material and low refractive index material. At most, two of the cathode ray tubes have only the display window and the fluorescent material layer. Images are thereafter produced with high brightness wherein respective supplied beam currents are increased by an amount to compensate for a drop in luminance intensity caused by filter removal. The brightness attained is equal to that of a conventional projection system which includes cathode ray tubes which each utilize multilayer interference filters.