Abstract: A cathode-ray tube with either a positive-or a negative tolerance viewing-screen structure comprises an evacuated envelope, a luminescent viewing screen within the envelope and means for exciting the screen to luminescence. The tube includes means, such as an apertured mask or a light-absorbing matrix, for selectively defining to the viewer an array of discrete excited areas in the screen which are noncircularly graded in size, with the largest areas in the central portion of the screen and the smallest areas in the peripheral portions of the screen.

Abstract: A correcting lens for use in the formation of a color picture tube screen has a first effective surface comprised of a plurality of elements separated by boundaries of discontinuity. Each of the elements in the first effective surface is separately contoured to reduce misregister in the tube. The second effective surface, opposite the first, is contoured to additionally reduce misregister in the tube.