Shaping of an electron beam in high-resolution CRTs for reduction of moire fringes

In order to reduce the raster moire fringes appearing in high-resolution CRTs, an evaluation technique is developed which simulates visual appearances of the moire patterns by using a Gaussian weighting method. It has been found that the moire patterns are strongly influenced by the shape of an electron beam profile. By using the evaluation technique, optimum electron beam profiles for various moire modes are pursued. Although the common belief is that the Gaussian current density distribution is the best for the beam profile which gives least moire fringes, it is found that an introduction of a small deviation to the Gaussian distribution reduces the moire contrast to an appreciable extent. This enables us to design CRT electron guns which have an improved moire characteristic.