| 摘要 |
PURPOSE:To obtain a mass-productionable color picture tube by bringing the projection of one of at least two masks higher than that of the other mask thereby achieving strong focusing force more effectively at the mask section while maintaining sufficient mechanical strength. CONSTITUTION:First mask 8 and second mask 7 are provided with projections 24, 23 around the apertures 22, 21 and upon application of potential onto each mask, electric force lines are produced from the projection 24 of mask 8 to the projection 23 of mask 7 to form a tetrode lens system. Consequently the electric force lines will be stronger in the direction perpendicular to the advancing direction of beam when compared with general tubular lens system to increase focusing force. Here since it will function as a disperse lens in Y-Z face while function as a focus lens in X-Y face, a beam spot elongated in Y-axis is produced on screen 1 for impinging electron beam. The focusing force will increase as the heights of projections 24, 23 increase but equivalent focusing force is achieved even the height of projection of one mask is low if the height of the other projection is sufficiently high. |
