Cathodochromic CRT erasure and tube set up method

Abstract

An improved method for erasure of an image target in a CCRT projection system includes the steps of projecting a defocused electron beam onto the target forming a scan line, establishing an energy level below the erase threshold to prevent erasure of any portion of the target within the single line, scanning multiple lines across the full target, and overlapping the scan lines sufficiently to provide integrated heat energy to cause erasure. The energy level is established at about 75% of the erase threshold or about 0.3 joule/cm.sup.2. The power is preferably set at 30 kv and 400 microamps with a single scan line being established at 0.056 inch. Preferably, the scan line is set to overlap 5-12 times to cause erasure, with the optimum being approximately 8 overlaps. In the related CCRT set up of the erasure mode, after overlapping the scan lines, the energy level is gradually increased until the integrated heat energy is sufficient to cause erasure. With these parameters established, the desired erasure of the target is assured when needed.

Dependencies are inferred from the claim text.