Index-type color cathode ray tube

Abstract

First and second index signal phosphor layers are formed on a phosphor screen that is formed on the inner surface of a face plate. A rear plate is provided with first and second light sensing units for detecting signal lights from the first and second index signal phosphor layers, respectively. Each first light sensing unit includes a first light collecting plate, which radiates absorbing light having a radiation peak wavelength substantially equal to or shorter than the radiation wavelength of each first index signal phosphor layer. Each second light sensing unit includes a second light collecting plate, which radiates absorbing light having a radiation peak wavelength substantially equal to or shorter than the radiation wavelength of each second index signal phosphor layer. Arranged between each second collecting plate and the rear plate is a filter, which transmits the index signal light from the second index signal phosphor layer and shades the index signal light from the first index signal phosphor layer.