The problem of moire is eliminated by randomizing the vertical and horizontal pattern of webs between apertures of a shadow mask. A cathode ray tube is provided having a color phosphor screen structure comprising a plurality of arrays of substantially parallel lines. The lines in each array are adapted to emit light of a particular color. A shadow mask, having a plurality of substantially parallel rows of apertures that are elongated in the direction of the rows and separated from adjacent apertures in each row by webs, is spaced from the screen. The webs are randomly spaced along each row and the webs in adjacent rows are randomly displaced from one another in the direction of the rows. Alternatively, the web spacing in each row can be uniform and the rows randomly displaced from one another in the direction of the rows.
A color picture tube having a shadow mask provided with a plurality of vertical aperture rows arranged as horizontally juxtaposed to one another, each vertical row comprising the electron beam transmissive apertures vertically arranged in line with a predetermined pitch P.sub.y. With a view to making possibly occurring moires imperceptible, the arrangement of the apertures are made such that, when spatial deviation in the vertical positions between any two apertures in the horizontally adjacent aperture rows is represented by .DELTA.y, there may be included combinations of at least two different type aperture rows of different deviations .DELTA.y which satisfy the following condition ##EQU1## at least when n is equal to 1, 2, 3 or 4 and k is an odd number smaller than 2n.
The present invention provides an improved cathode-ray tube of a type having a cathodoluminescent line screen and slit apertured mask mounted within the tube in spaced relation to the screen, wherein the slits in the mask are aligned in substantially parallel columns, each column containing a plurality of slits which are vertically separated by web portions of the mask. In the tube, some of the end portions of the aperture columns are modified to produce a more asthetically pleasing screen border.
An improved color picture tube includes a shadow mask which has a rectangular periphery with two long sides and two short sides. The mask has a major axis, which passes through the center of the mask and parallels the long sides, and a minor axis, which passes through the center of the mask and parallels the short sides. The mask includes slit-shaped apertures aligned in columns that essentially parallel the minor axis. Adjacent apertures in each column are separated by tie bars in the mask. The widths of the tie bars are graded in dimension. The grading is at least partially related to the amount of tie bar stretch occurring in a similar size mask having different tie bar widths.
In a color cathode ray tube having a vertically striped screen and a vertically slotted aperture mask, the top and bottom screen edges are made smooth by varying the vertical pitch between mask apertures while keeping the number of apertures per vertical column constant, so that every other column terminates in a full length slot.
A shadow mask type color CRT has a plurality of electron beam holes and a plurality of bridges for dividing the holes in the axial direction thereof. The electron beam projected from an electron gun passes the electron beam holes and stimulates the fluorescent screen behind the holes so as to cause the fluorescent screen to emit light. By the arrangement of the bridges in such a manner as to deviate the position of each bridge by the distance U from the intersection of an imaginary lattice, the defect such as fringes including a Moire on the screen caused by the regular arrangement of the bridges in the prior art is eliminated. The distance U is determined by a probability distribution function Q(U) which satisfies Moire regulating conditions. The shadow mask type CRT is used as a CRT commonly for two different systems using a different number of scanning lines.
