GB2132400A

GB2132400A - Visual display device

Info

Publication number: GB2132400A
Application number: GB08330829A
Authority: GB
Inventors: Barry Arthur James Clark
Original assignee: MELDISC INVESTMENTS Pty Ltd
Current assignee: MELDISC INVESTMENTS Pty Ltd
Priority date: 1982-11-18
Filing date: 1983-11-18
Publication date: 1984-07-04
Also published as: GB8330830D0; GB8330829D0; AU2152783A; GB2131590A; AU2152683A

Abstract

A display device 10 has a display unit with at least one array of light sources which are selectively switchable to on and off states. The light sources 16 are arranged in groups of three in closely spaced configuration and the sources in each group arranged to emit different colored light when operated so that, when viewed from a distance, the color of each group can be varied in accordance with which of the sources within a group are illuminated. The sources each comprise an electric filament lamp and an associated colour filter. The sources in each group are arranged to emit light having respective CIE 1931 chromaticity coordinates substantially as follows: y SIMILAR 0.3 x SIMILAR 0.7; y SIMILAR 0.4 x SIMILAR 0.6; and y SIMILAR 0.7 x SIMILAR 0.3, respectively. The device 10 includes a peripheral facia 100 colored in at least two colors which are visually distinguishable one from the other, and being of low reflectivity. By control of the switching different color patterns or a moving image is displayed. The color of the light sources may be chosen to be red, green and orange. <IMAGE>

Description

1

GB 2 132 400 A 1

SPECIFICATION Visual display device

In one aspect the invention relates to visual display devices of the kind having an array of light 5 sources and an array of switches, said switches being coupled whereby, in use and on application of a power source to the device, each said source is switchable to at least two conditions, at which the illumination provided by that source differs, by 1 o corresponding switching of the condition of a respective said switch between first and second states, the array of light sources comprising a plurality of groups of said sources each said group comprising three sources which, when 1 5 illuminated, are of differing color.

By selectively switching the light sources within each group the color of the group, viewed at a suitable distance, can be varied. If the relative states of illumination of the sources of each group 20 differs from group to group then a pattern of different colours will be presented by the display. Thus, by varying the arrangement of the switching of said switches different color patterns may be made to appear on the device. Devices of this kind 25 may be adapted, for example, for display of moving images of various kinds or for otherwise displaying information which varies with time.

A difficulty arises with display devices of the above kind in that, particularly if the devices are to 30 be used outside, powerful sources must be used in order that the visual information to be conveyed will be discernible to an observer. On the other hand, readily available types of light source are not capable of being formed in a way 35 which enables three sufficiently different color types to be formed to constitute a group which can, by control of the light outputs of respective ones thereof, be made to exhibit a wide color variation when the group is observed from a 40 distance. While this difficulty can be overcome by using specially designed sources, this is costly. An alternative is to use readily available lamps and selectively filter the light therefrom. However most such lamps do not exhibit substantial output 45 over a wide enough spectal range to permit filtering such that the resultant colors of the sources in each group can constitute a set enabling synthesis of a range of colors approaching the full range perceivable by the 50 human eye, at least unless the lamps to be filtered to produce one or more of the set of colors is made of impracticable power output compared with one or more of the others. Surprisingly, it has now been found however, in accordance with one 55 aspect of this invention, that if the colours for the three sources within each said group are selected in a particular way, it is possible to achieve the result that each group is capable of synthesizing the appearance of a useful and relatively wide 60 gamut of different colours whilst at the same time permitting use of readily available light sources of roughly the same output, suitably filtered. Thus, in accordance with this aspect of the invention, a display device as described above is characterized

65 in that first, second and third ones of the sources in each group in use emit light coloured such as to have respective CIE 1931 chromaticity coordinates substantially as follows:

y=0.3, x=0.7;

70 y=0.4, x=0.6; and y=0.7, x—0.2, respectively,

said coordinates being those prevailing when each source is at maximum luminosity prevailing in use of the display device.

75 By this means, it has been found possible to use filament lamps for the said sources, particularly standard types of filament lamp such as 24 volt types. These lamps may be of a kind in use generating light having CIE 1931 80 chromaticity coordinates y, x approximately equal to 0.41 and 0.46 respectively, corresponding to a source of color temperature approximately 2,800K. In this case, the lamp of each source is filtered by a separate filter in order to bring about 85 the desired overall color renderings of the sources. In this case, said first source (that to have chromaticity coordinates y, x of substantially 0.3 and 0.7 respectively) may have a red filter with transmittance of approximately 40%, the 90 second source (that to have chromaticity coordinates y, x substantially equal to 0.4 and 0.6 respectively) may have an orange filter with transmittance of approximately 50%, whilst the third source (that to have chromaticity 95 coordinates y, x of 0.7 and 0.2 respectively) may have a green filter with transmittance of approximately 30%.

In another aspect, the invention is concerned with improving the visibility of visual display 100 devices in a-fashion permitting more ready discernment of information content thereof. In accordance with this aspect the invention provides a visual display device having an illuminatable display unit surrounded by a border 105 which border is coloured in at least two colours which are visually distinguishable one from the other, the border being of low reflectance. It is to be understood that the term "color" as immediately before defined includes black. 110 Preferably, the reflectance of the panel is less than 25% more preferably 12% or less. Likewise, the reflectance of the surface immediately surrounding the individual light sources themselves is preferably less than 25% more 115 preferably less than 12%.

I

Further in accordance with this invention, it has been found that visibility of the patterns displayed in visual display devices can be improved by providing reflectors around the lamps constituting 120 the array. Thus in another aspect, the invention provides a visual display device comprising an array of selectively illuminatable light sources characterised in that the sources comprise electric lamps associated with respective 125 reflectors operable to direct light in a forward direction away from the array.

2

T

GB 2 132 400 A 2

The invention is further described with reference to the accompanying drawings in which: ■

Figure 1 is a front view of a display device 5 constructed in accordance with the invention;

Figure 2 is a fragmentary view showing one portion of a display unit incorporated into the device of figure 1;

Figure 2 is a fragmentary view showing the 10 arrangement of light sources within a group of light sources in the unit of figure 2; and

Figure 4 is a fragmentary cross-sectional view showing the construction of a light source incorporated into the device of figure 1. 15 Referring firstly to figure 1, there is shown therein a display device 10 having a display unit 12 made up of, in this case, seven side-by-side planar arrays 14 of light sources 16. Light sources 16 in each array are arranged, in this case, in 20 groups of three, the sources in each group, as described later, having respective different colors when operated. The light sources 16 within each group 20 are arranged in a triangular closely spaced configuration as shown at figure 3. Each 25 source includes an electric filament lamp 48 (figure 4). The groups 20 of sources 16 may for example be arranged, in each array 14, as a rectangular array of eight columns and seven rows. The means whereby the lamps are supplied 30 with powder does not form part of this invention. However, generally an electric power source (not shown) is arranged to be coupled to lamps 48 via a lamp driver circuit operable to condition respective ones of thelamps 48 to on or 35 off conditions. In the off condition, there is substantially no light output from a lamp, but in the on condition the lamp is brightly illuminated.

Referring now to figure 4, one source 16 is shown therein as including its filament lamp 48 40 mounted in a hollow cylindrical housing 50. Housing 50 has an internal bore 52 which has a smaller diameter end portion 52a and a larger diameter portion 52b. The lamp is housed in the smaller dimensioned portion 52a such that the 45 light from the lamp when illuminated is directed against the portion 52b and against a reflective angled stepped surface 52c interconnecting portions 52a and 52b for direction of light forwardly of the source and outwardly from the 50 housing via an opening at the forward end of bore portion 52b remote from portion 52a, that is to say in the direction indicated by arrow 54.

Housing 50 is preferably of metal of a kind having a surface exhibiting a high luminous reflectance, 55 such as aluminium or an aluminium alloy.

Preferably too, the internal surface of bore portion 52b as well as stepped surface 52c are in the form of specular surfaces, preferably slightly irregular, to diffuse local concentrations of light in 60 the far field of illumination provided by each source 16.

A suitable filter 56 is interposed at the forward end of the bore 52, this filter being suitably colored to effect the desired coloration of the light 65 from the lamp. The housings 50 of all of the sources 16 in each array 14 may be mounted within circular openings 59 in a common front panel 60 of that array and held in position as shown with screws 62 which extend from the 70 front of panel 60, through openings in the panel 60 and thence to be threadedly received in threaded openings in clamping elements 64 bearing against the rear of the housings, so as to sandwich the housings between the elements 64 75 and the panel 60. Preferably, each filter 56 is retained in position in an internal groove at the forward end of bore portion 52b, by means of a circular sealing ring 68 received in that groove, in such a fashion as to seal the associated housing 80 50 against ingress of moisture.

Preferably, the front surface of panel 60 has a dark matt or dark semi-gloss finish, so that incident ambient illumination of the unit 12 will not interfere with perception of the display 85 provided by the device 10. This surface should have a total luminous reflectance for CIE llluminant C of less than 25%, more preferably less than 12%.

It is preferred that the lamps 48 be 90 commercially available 24 volt filament lamps. Preferably the lamps are under-run, by being supplied with a supply voltage of only 22 volts when switched on so as to maximise lamp life. The colors of the filters 56 in each group of 95 sources 20 may be as follows, where 'x' and 'y' in each case refer to CIE 1931 chromaticity coordinates and "transmittance" means direct luminous transmittance for light from lamps 48:

(a) first filter, red,

100 red transmittance approximately 20%, 'y' equals approximately 0.3, 'x' equals approximately 0.7;

(b) second filter orange,

orange transmittance approximately 50%, 'y' 105 equals approximately 0.4, 'x' equals approximately 0.6;

(c) third filter, green,

green transmittance equals approximately 30%, 'y' equals approximately 0.7, 'x' equals 110 approximately 0.2, or is substantially in the range 0.2 to 0.3.

The transmittances and chromaticity coordinates were measured using the described under-run lamp 48 having CIE 1931 chromaticity 115 coordinates approximately equal to 'y' equals 0.41 and 'x' equals 0.46, corresponding to a source of color temperature approximately 2800K.

The filters may be formed from cellulose 120 acetate material of thickness 0.25 mm.

As shown particularly in figure 1, the display unit 12 is preferably surrounded by a facia 100 in the form of a planar element surrounding the entire periphery of the unit 12. Preferably, this 125 facia is such as to present a matt surface to viewers of the device. In particular, it is preferred that the total reflectance of the facia should be

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GB 2 132 400 A 3

low, such not exceeding 25% and preferably being less than 12%. Furthermore it is preferred that the facia be colored in at least two colors preferably being colors which are generally 5 complementary to colors which the units 12 may assume in use or at least to the color assumed when all of sources 16 are turned on.

As shown, the different coloring may be achieved by painting the facia with three endless 1 o bands of color 102, 104, 106. The first band 102, i.e. that closest to and extending immediately around the periphery of unit 12, may be colored black. The second band 104, i.e. that extending around band 102 may be colored dark blue. The 15 third band 106, i.e. that extending around band 104, may be colored dark green. More particularly, the colors may have CIE 1931 chromaticity coordinates y, x, for illuminant 'C', substantially as follows:

20 band 106

green: y=0.3, 'x'=0.2,

band 104

blue: 'y'=0.2, 'x'=0.2,

band 102 25 black: 'y'=0.3, 'x'=0.3.

It has been found possible to form a suitable screen as shown and using the colors described by use of paints having total luminous reflectances for CIE Illuminant C as follows: green 30 (band 106) 8%, black (band 102) 4.5%, blue (band 104) 10.5%.

The described facia 100 permits a good improvement in the conspicuousness of the display of the device 10 and in the general 3 5 visibility thereof. In a particularly preferred form, the facia has a height 3x, where 'x' is the display unit height. Preferably the length of the facia is in the range 9 to 10x, where the unit 12 is rectangular.

40 In use of the described apparatus, illumination of the sources 16 is effected in any desired pattern. In particular the color presented by the device at local areas can be varied depending on whether none, one or any one of three different 45 pairs of sources in each group 20 is illuminated. Although with the described green, orange and red colors for the sources within each group 20 it is not possible to synthesize a full color range, it has been shown in practice that a very 50 satisfactory and pleasing visual effect is obtained. A sufficiently wide color variety can be achieved, to provide good readability of writing or letters or figures, for example. Particularly where the intended display is of writing, the lack of a full 55 color range synthesis is not important.

Claims

Claims

1. A visual display device of the kind having an array of light sources and an array of switches, said switches being coupled whereby, in use and 60 on application of a power source to the device,

each said source is switchable to at least two conditions, at which the illumination provided by that source differs, by corresponding switching of the condition of a respective said switch between 65 first and second states, the array of light sources comprising a plurality of groups of said sources each said group comprising three sources which, when illuminated, are of differing color, wherein first, second and third ones of the sources in each 70 group in use emit light coloured such as to have respective CIE 1931 chromaticity coordinates substantially as follows:

y=0.3, x=0.7;

y=0.4, x=0.6; and 75 y—0.7, x=0.2, respectively said coordinates being those prevailing when each source is at maximum luminosity prevailing in use of the display device.

2. A visual display device as claimed in claim 1 80 wherein said first, second and third sources in each group comprise first, second and third filament lampis having respective first, second and third filters to'selectively filter light therefrom.

3. A visual display device as claimed in claim 2 85 wherein said first filter has a transmittance of about 20%, said second filter has a transmittance of about 50% and said third filter has a transmittance of about 30%.

4. A visual display device as claimed in claim 2 90 or claim 3 wherein said display lamps when emitting illumination to the maximum extent prevailing in use of the display device emit light having CIE 1931 chromaticity coordinates substantially as follows:

95 y=0.41

x=0.46;

5. A visual display device as claimed in claim 2 or claim 3, wherein said lamps have a color temperature of 2800K when emitting illumination

100 to the maximum extent prevailing in use of the device.

6. A visual display device having an illuminatable display unit surrounded by a border which border is coloured in at least two colours

105 which are visually distinguishable one from the other, the border being of low reflectance.

7. A visual display device as claimed in claim 6 wherein the total reflectance of said border for CIE Illuminant C is less than 25%.

110 8. A visual display device as claimed in claim 6 wherein the total reflectance of said border for CIE Illuminant C is less than 12%.

9. A visual display device as claimed in claim 7 or claim 8 wherein said border comprises a first

115 band around the periphery of said unit, a second band around said first band and a third band around said second band.

10. A visual display device as claimed in claim 9 wherein said first band is black, said second

120 band is dark blue and said third band is dark green.

GB 2 132 400 A

11. A visual display device as claimed in claim

10 wherein the CIE 1931 reflectance chromaticity coordinates of said bands, measured with Illuminant "C" are substantially as follows:

5 first band: y=0.3; x=0.3

second band: y=0.2; x=0.2

third band: y=0.3; x=0.2.

12. A visual display device as claimed in any one of claims 6 to 11 wherein said border has a

10 height 3x, where "x" is the display unit height.

13. A visual display device as claimed in any one of claims 6 to 12 wherein said unit is rectangular and the side to side length of said border is 9 to 10x where "x" is the display unit

15 height.

14. A visual display device comprising an array of selectively illuminatable light sources characterised in that the sources comprise electric lamps associated with respective

20 reflectors operable to direct light in a forward direction away from the array.

15. A visual display device as claimed in claim 14 wherein each said source includes a housing having a bore therethrough, said bore having an

25 annular step surface between larger and smaller cross sectioned portions of the bore, said surface at least in part defining the reflector of that source, and being an irregularly reflective surface.

16. A visual display device as claimed in claim

30 1 5 wherein said lamp of each housing is positioned in the smaller cross sectioned bore portion of its associated housing and projects into the larger cross sectioned bore portion thereof.

17. A visual display device as claimed in claim 35 16 including light filters in said larger diameter bore portions of the housings.

18. A visual display device as claimed in any one of claims 15 to 17 including a front panel and means for clamping said housings therebehind,

40 said front panel having openings to permit light from the lamps to pass from the larger cross ■ sectioned bore portions of the housings through those openings and forwardly from the front panel.

45 19. A visual display device as claimed in any one of claims 15,16 or 17 wherein said reflector is defined by said surface and the surface of said larger cross-sectioned portion of said bore.

20. A visual display device as claimed in any 50 preceding claim wherein said array of light sources is positioned so as when viewed from a position in front thereof to appear in a background formed by a surface of dark color.

21. A visual display device as claimed in claim 55 20 wherein the total luminous reflectance of said background for CIE Illuminant C is less than 25%.

22. A visual display device as claimed in claim 20 wherein the total luminous reflectance of said background for CIE Illuminant C is less than 12%.

60 23. A visual display device as claimed in any one of claims 1 to 5 wherein said chromaticity coordinate "x" for said third light source is substantially in the range 0.2 to 0.3.

24. A visual display device substantially as 65 herein described with reference to the accompanying drawings.

25. The steps or features disclosed herein or any combination thereof.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1984. Published by the Patent Office. 25 Southampton Buildings, London, WC2A 1AV, from which copies may be obtained.