IMPROVED SHADOW MASK CRT FOR DOCUMENT VIEWING

Publishing Venue

Xerox Disclosure Journal

Abstract

Advanced electroreprographic systems make use of cathode ray tube (CRT) user interfaces, and as the features offered on these systems become more complex, it is occasionally appropriate to utilize color CRT's for the user interface displays. These user interfaces may also display the image of a document on the CRT to confirm the feature selections associated with processing of the document. For this reason, it is necessary to combine the color CRT feature display with a bitmap display of the document. Unfortunately, conventional shadow mask color CRT's often have somewhat poorer resolution that monochromatic CRT's because the color image is created by three different electron guns which address the respective color phosphors on the internal surface of the CRT screen. The three electron guns may not be accurately aimed at the appropriate phosphor dots over the entire screen area, thus resulting in color mis-registration which degrades the resolution of black and white images created by overlaying three color images. The severity of the mis-registration is dependent upon the accuracy of alignment of the color shadow masks during manufacture of the CRT. While it is possible to to remove the effects of the mis-registration by displaying the bitmap image in a monochromatic fashion, it is unacceptable from a user interface perspective to display a black and white document in the manner.

XEROX DISCLOSURE JOURNAL

IMPROVED SHADOW MASK CRT FOR DOCUMENT VIEWING U.S. C1.340/721 Richard H. Tuhro

Proposed Classification

Int. Cl. G09g 1/06

Advanced electroreprographic systems make use of cathode ray tube (CRT) user interfaces, and as the features offered on these systems become more complex, it is occasionally appropriate to utilize color CRT's for the user interface displays. These user interfaces may also display the image of a document on the CRT to confirm the feature selections associated with processing of the document. For this reason, it is necessary to combine the color CRT feature display with a bitmap display of the document. Unfortunately, conventional shadow mask color CRT's often have somewhat poorer resolution that monochromatic CRT's because the color image is created by three different electron guns which address the respective color phosphors on the internal surface of the CRT screen. The three electron guns may not be accurately aimed at the appropriate phosphor dots over the entire screen area, thus resulting in color mis-registration which degrades the resolution of black and white images created by overlaying three color images. The severity of the mis-registration is dependent upon the accuracy of alignment of the color shadow masks during manufacture of the CRT. While it is possible to to remove the effects of the mis-registration by displaying the bitmap image in a monochromatic fashion, it is unacceptable from a user interface perspective to display a black and white document in the manner.

Accordingly, the present invention is directed towards a novel shadow mask CRT which eliminates the aforedescribed problems. Generally, in the manufacture of a shadow mask CRT, the color dots are put in place by using a shadow mask as a film tool to control the positioning of the phosphor dots. For example, a phosphor mixture is placed on the CRT faceplate and exposed...