In cathode-ray tubes utilising screens with a luminescent layer made up of two kinds of phosphors having different spectra, one having virtually no remanence (1), and the other being of remanent kind (2), with switching of the voltage between two values, low and high, the second phosphor only being excited at the high value, due to the presence of a barrier B, in order to prevent the unwanted flash of different colour, produced by the non-remanent phosphor at the instant of appearance of the remanent trace, the invention provides for the addition to the aforementioned two constituents, of a third non-remanent phosphor (3) equipped with a barrier B and having a spectrum such that the superimposition of the flash which it yields at high voltage, and that yielded by the phosphor (1), produces the colour corresponding to the phosphor (2). Application to radars using real and synthetic video signals.
A cathode-ray tube has a phosphor screen which is made by using a mixture of a long persistent phosphor and a short persistent phosphor. A light emission from the short persistent phosphor has a spike figure, so that a light pen can have sufficient sensitivity therefor, and a light emission from the long persistent phosphor is continuous within the one cycle period of the frame frequency, so that flicker is not noticeable.
