Described is a beam index type color cathode ray tube in which at least one of tricolor phosphor stripes, that is the red, blue and green stripes, is different in width from the other color phosphor stripes, and m index stripes are associated with n sets or triplets of the color phosphor stripes. The widthwise center-to-center distance between the adjoining color phosphor stripes is set to a constant value. Each index stripe is of a width lesser than the width of the guard band provided between adjoining ones of the color phosphor stripes, and is provided at the widthwise center of the associated guard band. The arrangement provides index signals of sufficient intensity, while assuring a positive color switching.
A beam-index-type cathode ray tube includes a vacuum tube defined by a panel and a funnel having a neck; a phosphor screen provided with index stripes to provide color selection, the phosphor screen being formed on an aluminum metal back layer; an electron gun mounted inside the neck to emit electron beams to the phosphor screen; a deflection yoke mounted around the neck; a light reception window provided on the funnel; a detector to generate an index electric signal by condensing index light generated from the index stripes through the light reception window; and an index circuit to transmit a signal obtained by synchronizing the index signal with a color signal. When a diagonal length on the outer surface of the funnel is "d", the light reception window is provided at a location within a range of 0.1-0.3 d from a corner of a seal edge of the funnel.
The color cathode ray tube of this invention improves the purity (color purity) adjustment margin and permits bright display without deteriorating the resolution. At least the black matrix holes 40g, 40b, 40r, forming the phosphor surface or the shadow mask apertures are so arranged that the center-to-center distance between the adjacent holes or apertures corresponding to the pixel phosphors of the same color in a vertical direction is greater by about 10 to 70% than the center-to-center distance in an inclined direction. Further, at least the black matrix holes or the shadow mask apertures are shaped non-circular with their vertical cross-section greater than their horizontal cross-section. With this invention it is possible to provide a color cathode ray tube which has improved brightness and purity (color purity) adjustment margin and a substantially enhanced resolution.
A screen for a beam index tube includes a fluorescent surface having a pattern of color stripes respectively producing red, green, and blue light in unit areas within the stripes in response to an incident electron beam and index unit areas regularly arranged in the pattern, the color stripes being arranged side-by-side and along a vertical direction with color unit areas of vertical stripes being in registration along a horizontal direction, each color unit area being spaced in the horizontal and vertical directions from the nearest color unit area by one unit area, and the index unit areas being disposed among the color unit areas and spaced from the nearest index unit area by three unit areas in the horizontal direction and one unit area in the vertical direction. A beam index tube may include the screen in combination with a tube assembly and an electron gun. Since the index unit areas are not spaced from nearest color unit areas, vertical deflection correction of the electron beam is not required and can be omitted. Thus, the picture quality produced is not adversely affected by the earth's magnetic field and manufacturing costs are reduced by avoiding the elements needed for the vertical deflection correction.
