Halo-reducing faceplate arrangement
AssigneeNorth American Philips Corporation
InventorJacob Khurgin
Life of this patent
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Abstract
A faceplate arrangement for a monochromatic cathode ray tube includes a compound filter disposed between the faceplate and a light scattering luminescent screen. The compound filter includes a multilayer interference edge filter adjacent the screen and a multilayer matching filter adjacent the faceplate. The edge filter reflects back into the screen light rays received from the screen which would contribute to halo, and the matching filter matches the optical admittances of the edge filter and the faceplate.
Claims5
In a monochromatic cathode ray tube having a faceplate arrangement including a faceplate consisting essentially of a transparent material, an internal screen consisting essentially of a light scattering luminescent material for emitting light radiation in a band encompassing a predetermined wavelength .lambda..sub.0 and extending from a lower wavelength .lambda..sub.0.sup.- to an upper wavelength .lambda..sub.0.sup.+, when excited by an electron beam, and an electrically-conductive reflective layer disposed on an inner surface of the screen, the improvement comprising a compound optical filter disposed between the screen and the faceplate, said optical filter including:
- (a) a first portion comprising a multilayer interference edge filter having a cutoff wavelength of .lambda..sub.0.sup.+ for light rays received from the screen which are perpendicular to said edge filter, and having a cutoff wavelength of .lambda..sub.0.sup.- for light rays received from the screen which are incident to said edge filter at angles greater than a predetermined angle .theta..sub.H, which light rays would significantly contribute to halo;
- and
- (b) a second portion comprising a multilayer matching filter for matching the optical impedances of the faceplate and the edge filter.
Dependencies are inferred from the claim text.