Cathode-ray display tube for color printers

Claim 1

A cathode-ray display tube system for color printers, the cathode ray tube having a phosphor screen for producing thereon a light spot which is variable in position and color in response to input signals to expose photo-sensitive color paper, said phosphor screen including: a blue-emitting phosphor having a maximum ability of color emission in the range of wavelengths of 480 mμ and below with a radiant energy in the range of wavelengths of about 480 mμ and higher being 10% or less of the overall radiant energy; a green-emitting phosphor having a maximum ability of color emission in the range of wavelengths of 520 through 570 mμ with a radiant energy in the range of wavelengths of about 500 mμ and less and of about 630 mμ and higher being 5% or less of the overall radiant energy; and a red-emitting phosphor having a maximum ability of color emission in the range of wavelengths of 630 through 750 mμ with a radiant energy in the range of wavelengths of about 590 mμ and less being about 10% or less of the overall radiant energy; phosphor dots for producing color in a region of wavelengths to which ordinary photosensitive color paper is not sensitive and located beyond the area of normal raster; said tube system further comprising a photoelectric converter coupled to said phosphor dots for detecting light emission from said phosphor dots; a control circuit coupled to said photoelectric converter which is receptive of at least two pulse signals from said converter for determining the raster scanning condition of said phosphor dots: and an electron beam deflection circuit for said cathode-ray tube which is controllable by the output of said control circuit.