GB2260853A

GB2260853A - Colour display screens

Info

Publication number: GB2260853A
Application number: GB9122372A
Authority: GB
Inventors: Phillip Edwin Walker
Original assignee: GEC Ferranti Defence Systems Ltd
Current assignee: Leonardo MW Ltd
Priority date: 1991-10-22
Filing date: 1991-10-22
Publication date: 1993-04-28
Also published as: GB9122372D0

Abstract

A colour display in which the screen (10) comprises a display area having three different colour (R, G, B) light emitting materials disposed in a pattern such that a region of one colour (G) light emitting material is provided after each region of each of the other two different colour (R, B) light emitting materials to provide alternating couplets (R/G, B/G) of two different colour light emitting materials each including said one colour (G) light emitting material. As disclosed, the display screen is made up of phosphor stripes in a beam index type of cathode ray tube in which the indexing stripes 12 preceed and follow each couplet R/G, B/G of phosphor stripes. <IMAGE>

Description

Improvements In Or Relatina To Colour Displays This invention relates to colour displays and more particularly but not solely to beam index colour display tubes.

Colour displays normally employ adjacent regions of different materials which when activated emit one of several different colours of light for example red, blue and green.

In the case of one type of cathode ray tube the regions are formed by stripes which extend from top to bottom of the inside surface of the display screen. With a tube employing the beam index scanning principle there are also provided indexing phosphor stripes there normally being three index stripes for each four triplets of the other colour stripes.

When such a display is used in a monochrome mode it will be appreciated that only one stripe of the triplets is activated with consequential degradation of resolution.

The present invention seeks to provide a colour display with improved monochrome resolution.

According to the invention there is provided a colour display in which the screen comprises a display area having three different colour light emitting materials disposed in a pattern such that a region of one colour light emitting material is provided after each region of one of the other two different colour light emitting materials to provide alternating couplets of two different colour light emitting materials each including said one colour light emitting material.

A display constructed in accordance with the invention permits operation in the monochrome mode by activating only the region of said one colour light emitting material which it will be appreciated can be closer to the next same colour region than in constructions where the three colours are disposed in repetitive sequence.

The three colours of light may be red, blue and green and said one colour is preferably green.

The display may comprise a cathode ray tube wherein the pattern of regions of different colour light emitting materials is formed of stripes. The screen may include repetitive stripes of a fourth colour beam indexing light emitting material disposed between stripes of the other colour light emitting materials and the fourth colour may be ultra-violet.

In order that the invention and its various other preferred features may be understood more easily, some embodiments thereof will now be described, by way of example only, with reference to the drawings, in which: Figure 1 is a schematic diagram illustrating the structure of a conventional beam index cathode ray tube; and Figure 2 is a schematic diagram illustrating the structure of a beam index cathode ray tube constructed in accordance with the invention.

The same reference numerals are used to identify similar elements of the two constructions.

The conventional beam index cathode ray tube of Figure 1 is illustrated as a cross section through the glass screen 10. The inner surface of the screen is provided with stripes of different colour light emitting phosphors R, G, B, signifying red, blue and green respectively, and as will be seen these are disposed in an alternating triplet pattern. An aluminium film coating 11 is provided over the inside surface of the screen and over the phosphor stripes to prevent light leakage between them and short persistence phosphor index stripes 12 which are provided on the other side of the film. The illustration shows the normal configuration where three index stripes are provided for each four triplets. Putting this another way, there is provided an index stripe after every fourth colour stripe.

The problem with employing such a cathode ray tube display in a monochrome mode is that there is significant reduction in resolution compared with a dedicated monochrome display because only one third of the colour stripes are activated.

The cathode ray tube of Figure 2 is constructed in accordance with the invention and also illustrates a cross-section through the glass screen 10. The inner surface of the screen is provided with stripes of light emitting phosphors R, G, B but instead of providing them in an alternating triplet pattern as in Figure 1 they are arranged in an R, G, B, G quad arrangement. This permits significant improvement of resolution if the display is operated in green monochrome mode as every other stripe is green as opposed to every third stripe with the previously known arrangement. Indexing stripes 12 of a different colour e.g. ultra-violet short persistence phosphor are provided at repetitive intervals and are preferably provided as illustrated after each couplet of colour stripes.The illustration also shows a run in zone on the screen comprising the equivalent of 10 couplet spacings where there are no colour stripes but nine index phosphor stripes (1-9).

There is no index phosphor stripe at position 10 and there is a black screen matrix 14 over these first 10 index stripes.

Although the construction described is arranged to permit improved resolution when operated in green monochrome mode it will be appreciated that similar arrangements are possible where a different colour light emitting phosphor is the common colour in each couplet such that improved monochrome resolution is possible in that colour. Such constructions are considered to fall within the scope of this invention.

Although the embodiment described is specific to beam index tubes employing stripes of phosphor, the principle of this invention is applicable to other types of displays where repetitions of pixels of one colour can be increased across the display area to improve resolution when operating in the monochrome mode. Such constructions are considered to fall within the scope of this invention.

The invention permits improvements in either luminance, resolution, contrast or purity of display by varying the width of the quad structure stripes:

Claims

1. A colour display in which the screen comprises a display area having three different colour light emitting materials disposed in a pattern such that a region of one colour light emitting material is provided after each region of one of the other two different colour light emitting materials to provide alternating couplets of two different colour light emitting materials each including said one colour light emitting material.

2. A display as claimed in claim 1, wherein the light colours emitted by the three different colour light emitting materials are red, blue and green.

3. A display as claimed in claim 1 or 2, wherein the light colour emitted by said one colour light emitting material is green.

4. A display as claimed in claim 1, 2 or 3, comprising a cathode ray tube wherein the pattern of regions of different colour light emitting materials is formed of stripes.

5. A display as claimed in claim 4, comprising a beam index cathode ray tube wherein the screen includes repetitive stripes of a fourth colour beam indexing light emitting material disposed between stripes of the other colour light emitting materials.

6. A display as claimed in claim 5, wherein the stripes of a fourth different colour light emitting material emit ultra-violet light.

7. A display as claimed in claim 5 or 6, wherein each couplet of different colour light emitting stripes is proceeded and followed by a beam index light emitting stripe.

8. A display as claimed in claim 5, 6 or 7, wherein there is provided a run in section of the screen having only index stripes.

9. A display as claimed in any one of claims 5 to 8, wherein the index stripes extend beyond the different colour light emitting stripes above and below the effective screen display area.

10. A display as claimed in any one of claims 5 to 9, wherein the stripes are phosphor.

11. A display as claimed in any one of claims 5 to 10, wherein the stripes are disposed on the inside surface of the tube and are provided with a reflective covering over the rear of the stripes, and non covered inside surface of the screen, and the beam indexing stripes are disposed on the side of the covering which faces inwardly of the tube.

12. A display as claimed in claim 11, wherein the reflective covering is aluminium.

13. A colour display substantially as described herein with reference to the drawings.

14. A television, radar or thermal imaging system incorporating a display substantially as described herein with reference to the drawings.