Color picture tube having shadow mask with improved aperture shapes

In a color picture tube having a shadow mask, a dot screen and an electron gun for producing and directing three electron beams through said mask to said screen, said mask being rectangular and having two long sides and two short sides, said long sides paralleling a central major axis of said mask, and said short sides paralleling a central minor axis of said mask, said mask including an array of apertures arranged in columns and rows, the apertures in one row being in different columns than are the apertures in adjacent rows, and the size of the electron beam spots at said screen increasing with increasing distance from the center of said screen, the improvement comprising

• each of said shadow mask apertures having four sides with rounded corners in a substantially rectangular shape, two of said aperture sides approximately paralleling said major axis and establishing aperture height and two of said aperture sides approximately paralleling said minor axis and establishing aperture width, the widths and heights of said apertures increasing at a first rate and a second rate, respectively, from the center to the sides of said mask, along said major axis in a manner approximately proportional to the increase in the horizontal and vertical dimensions of said electron beam spots at said screen, and the widths and heights of said apertures increasing at a third rate and a fourth rate, respectively, from the center to the top and bottom of said mask, along said minor axis, in a manner approximately proportional to the increase in horizontal and vertical dimensions of said electron beam spots at said screen.