GB1316624A - Shadow masks for use in cathode ray tubes - Google Patents

Abstract

1316624 Colour television tubes SONY CORP 29 May 1970 [31 May 1969] 25994/70 Heading H1D A shadow mask for a colour television tube using three co-planar electron beams, wherein the apertures in the mask are arranged at the intersections of barrel-shaped horizontal lines with orthogonal pin-cushion-shaped vertical lines as in Specification 1,249,954 is characterized in that the apertures are circular in the centre of the mask and elliptical away from the centre. When the mask and the screen are spheres of radius R disposed a distance L from the centre of deflection of the beams, it is shown that the horizontal and vertical pitches P H (n, m) and P V (n, m) at co-ordinates (n, m) measured from the centre should be related by the equation if the pitches are to be constant along the central axes. For close packing of the impact areas on the screen without any overlapping, the ratio of the major axis a(n, m) to the minor axis b(n, m) of the elliptical aperture should be related by the equation Thus apertures at the same distance from the centre have the same eccentricity but the inclination of their major axes with the horizontal varies. An alternative arrangement considered is where the pitch of the apertures is constant along a line y =γx; the horizontal and vertical pitches are then given by the equations and the axis ratio given above is multiplied by a factor Similar equations may be derived for a cylindrical mask used with a cylindrical screen.