Directed Beam CRT Spot Shaping
Original Publication Date: 1979-Jun-01
Included in the Prior Art Database: 2005-Feb-20
High content, directed beam or stroked character displays are limited by their ability to achieve a bright enough display within the opposing constraints of flicker and phospher dwell times. By making use of spot astigmatism, the effective phosphor dwell time can be increased. This means that a display can have a higher picture content, with the resulting image having finer and sharper lines. For example, suppose the spot is astigmatically shaped using cylindrical lenses within the tube so that the long axis of the spot is aligned with the direction of beam writing. Then, if the length of the spot is made twice the normal spot diameter, the effective phosphor dwell time is doubled. The width of the spot is ideally only half the original spot diameter. producing a finer and better image quality.