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.

Abstract: An apparatus for properly aligning a cathode-ray tube projection unit before a viewing screen includes a pair of ultrasonic rangefinders and a cooperating pair of light emitting diode (LED) reader units. One ultrasonic rangefinder and one reader unit are connected to each of two opposite sides of the projection unit. Each rangefinder is directed toward the viewing screen to sense the distance between the viewing screen and the side of the projection unit to which the rangefinder is connected. The cooperating LED reader unit then indicates whether that side is too close to, too far away from or a proper operating distance from the viewing screen.

Abstract: A cathode ray tube (CRT) having a faceplate-deposited cathodochromic material, said CRT having electron beam write and erase. The erase beam is an electron beam focused to a size of approximately 0.010 inches at the image screen of the CRT and the intensity of the beam is about 10.sup.5 watts/in.sup.2.

Abstract: A cathode ray tube (CRT) having a faceplate-deposited cathodochromic material, said CRT having electron beam write and erase. The erase beam is an electron beam focused to a size of approximately 0.010 inches at the image screen of the CRT and the intensity of the beam is about 10.sup.5 watts/in.sup.2.

Abstract: A cathode-ray tube projection system employing a cathodochromic image screen and electron beam erase and in which the image is projected from the image screen surface nearest the electron gun. The main advantages of this system are higher resolution and improved image erasure which provides a high-contrast image.

Abstract: A process for preparing cathodochromic materials whereby coloration properties of the materials are enhanced by a low-temperature re-crystallization process. Crystalline powders formed using either hydrothermal or sintering growth techniques are hydrothermally re-crystallized at a temperature sufficiently high and for a time sufficiently long to effect re-crystallization. The temperature range for hydrothermal re-crystallization is 60.degree.C to 300.degree.C and the re-crystallization growth time is at least the order of 12 hours and, more typically, the order of three days. There is shown a cathode ray tube employing said materials.