| 摘要 |
PURPOSE: A beam index CRT is provided to have a larger screen by removing the approach area discriminated from the image area to expand the effective screen. CONSTITUTION: Light spots and black matrices are deposited as arranged on the upper side of a panel. Index fluorescent stripes(20) are formed in the starting part of a fluorescent face index fluorescent stripe. The index fluorescent stripes(20) have a width smaller than that of index fluorescent stripes(19) formed in an image area. The stripes(20,19) are formed side by side with same shape. Electron beams emitted from the electron gun are detected in a photo detector with photo output from the index fluorescent stripes(20,19) formed on the index fluorescent face. An indexing circuit detects with an index signals excited from the detected electron beams. The indexing circuit discriminates the image area from an image approach area.
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