Method and apparatus for adjusting CRT geometry

摘要

An improved method and apparatus for rapidly and accurately adjusting CRT image geometry for the purpose of removing defects in an image reproduced by a CRT. The method and apparatus include a conventional pattern generator for producing a grid-like test pattern, in the form of two mutually perpendicular sets of closely spaced parallel lines, on the viewing screen of the CRT whose geometry or image-forming apparatus is to be adjusted. A reference pattern image formed on a transparent base material suitable for viewing by transmitted light and having the same general characteristics as the CRT formed image is supported in superposed relationship with respect to the CRT formed, pattern generator produced test pattern image. Moire pattern bands or fringes indicative of defects in the displayed test pattern and therefore in the CRT geometry viewable by an equipment operator when viewing the displayed test pattern through the transparent reference pattern in such a superposed relationship may be readily removed by adjusting various component parts of the image-forming electron beam deflection system until the moire fringes resulting from image-defect generated misalignment between the CRT formed test pattern image and the transparent material formed reference pattern image are nulled or are no longer visible to an equipment operator.