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Control of CRT Contrast by Internal Etching

IP.com Disclosure Number: IPCOM000041413D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02

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Beeteson, JS Chase, BD Sowter, BR van den Oever, WE [+details]


Etching or stippling of the internal surface of a CRT has to been used to reduce the specular reflections from that surface. By choosing the etch to give a particular etch pit density, the diffuse reflectivity can be adjusted to control the contrast of the CRT. U.S. Patent 3,813,568 describes a technique for etching the internal surface of a CRT so that there are 3.5 x 105 to 3.5 x 107 pits/cm with optimum results for minimum specular reflection at 1 x 107 pits/cm and a pit depth of 1.5 microns. We have now found that within this range there is an intermediate range which allows control of the diffuse reflectivity as well as the specular reflectivity. Within the range of 2.8 x 106 to 2 x 107 pits/cm , the diffuse reflectivity and hence the contrast can be finely tuned.