GB2049142A - Process and equipment for the realisation of a coloured display - Google Patents

Abstract

A coloured light display is produced from light sources 2 of three different colours, each provided with a respective light reflector 3. The light emitted by the single light sources is directed onto a light- displaying plane 5, where all the light from all the light sources is united to form one single cone of light leaving the plane. Along the light-displaying plane a plurality of elementary light-deflectors, e.g. prisms, are arranged so that adjacent light-deflectors are alternately optically coupled to different light sources. Three light-deflecting groups are thus obtained. <IMAGE>

Description

SPECIFICATION Process and equipment for the realization of coloured display The invention relates to a process and equipment suitable for performing the process according to the invention, with the aid of which a coloured display/e.g. the operation of lightemitting information boards/ may be realiz ed-compared to known solutions more advantageously, with a higher efficiency of colour blending and at an identical power consumption with a higher surfacial brightness and more saturated colours.

In order to facilitate comprehension of our invention, first of all we intend to discuss in detail the colour blending mechanism to be developed and afterwards the possibilities yielded by the invention for developing a process and equipment, i.e. the types which may be developed, will be discussed.

In general, the equipments displaying by means of light are comprising all the equipments which give information to the viewer by means of a light-effect. In our specification this concept will be interpreted within a restricted scope; all the equipments have been ranged in this group which deliver the information by a change in /the composition of/ colour or brightness and which --comprise one or more light sources of different colour, or more than one light source of the same colour but having been provided with colour filters of different co lours, as well as elements influencing the path of the light beam, so e.g. mirrors, light-deflecting means, transparent or translucent light-transmitting means, and their task is to deliver some kind of infor mation for the viewer /a person or a technical device/, viewing the light-dis playing equipment within a given solid angular range, by the difference between the brightness-levels and colour composi tions belonging to different operational conditions of the light source.

The most characteristic field of application of the equipments of the described types has been the advertising lights composed of the light signal emitters and coloured image points. On the the displaying surface of such equipments by the individual control of the displaying elements filling the surface whereby control takes place according to brightness and colour composition-images approximating reality can be displayed. The image, as information, is realized in such a manner that each single light-displaying element is lit approximately with the same brightness and colour composition as the image-point it stands for.

The most characteristic field of application involves the following requirements: -simple and quick control in respect of brightness and colour composition, -high-grade operational safety, -low costs of realization, proper exploitation of the light, -high illumination intensity.

For solving the task, mostly the solution outlined in Fig. 1 has been used.

In the carrier and screening tube 1 there are three light sources 2 arranged and to each light source a respective reflector 3 has been co-ordinated. The reflectors 3 reflect the light of the light sources onto the translucent plate 5 arranged on the frontal plate. In the path of the three beams of rays colour filters 4 are arranged. In accordance with the law of additive colour blending one of the filters is capable of transmitting red /R/ beams of light, the other green /G/, the third blue /B/ beams. By the proper blending of the beams of light, corresponding to the basic colours R, G, B and by the individually performed change in intensity, the majority ot the shades of colours occurring in nature may be reproduced.

From the arrangement it necessarily emerges that the three beams of rays egressing from the light sources never run in parallel with each other and do not coincide with the optical axis of the light-displaying equipment, indicating simultaneously the main viewing direction of the same.

It goes without saying that this fact involves severe requirements in regard to the optical characteristics of the translucent screen ensuring colour blending.

In the whole viewing angular range uniform colour blending becomes possible if every point of the translucent screen behaving as a secondary source or radiating element produces a spherically symmetrical secondary radiation not dependent on the direction of the incident beam of rays.

Where the optical properties of the translucent screen deviate from the ideal, two disadvantages may be simultaneously observed: -the intensity of light decreases in the direc tion of viewing, -in the other directions the colour composi tion will be displaced.

The phenomenon is to be seen in Fig. 2. In Fig. 2/a the ideal case may be seen, showing the planar section of the two beams of rays.

From this it emerges that in the case of spherically symmetrical secondary radiating characteristics within the entire range /180 / the secondary radiation produced by the two rays is mixed in equal proportions.

In Fig. 2/b the case has been illustrated where the optical properties deviate from the ideal. Up to now, it has been tried to approxi mate the ideal state by using semi-transpar ent, etched, sand blasted etc. (diffusing) screens with more or less success. We have to point out to a further resultant disadvantage of the solution.

It goes without saying that the most advantageous conditions of colour blending at light intensity are to be ensured in case of lightdisplaying equipments in the direction of viewing and in its environment.

From the facts previously related it emerges that the known solutions the most disadvantageous conditions may be observed just in the main direction of viewing, while there is no possibility to improve said conditions, not even to the debit of the extreme ranges of the viewing solid angle.

This is to be considered as a significant drawback, since advertising lights are mostly arranged in places where the environment itself excludes the realization of the entire viewing range of 2ir. The characteristic application of the advertising lights is such that they are arranged on the frontal face of a building lying in the central line of some much frequented road. In this case the solid angle of viewing is narrowed down by the environment itself. Taking the minimal overlooking distance into consideration, in most cases a solid angle of viewing corresponding to a cone with an apex angle of 50-70" may be obtained.

In the solutions known, in the case of arrangements previously described, the light energy-radiated outside the solid angle becomes superfluous and wasted. The quantity of the light energy wasted in this manner is considerable.

Let us suppose that in the range of the solid angle of 2sr uniform light distribution may be obtained /the ideal case, as previously discussed/, in the case of an actual solid angle of 60 but 10% of the light energy passing through the screen arrives into the desired solid angle, 90% will be scattered as a waste.

The aim of the invention seeks to realize a lightdisplaying equipment in which the losses do not occur, but the whole energy penetrating the screen arrives into the desired solid angle of less than 2sir, simultaneously ensuring proper colour blending.

The invention is based on the recognition that the screen of the light-displaying equipment viewed from the proper distance appears as a surface in a homogeneously mixed light, even when the screen itself does not illuminate with homogeneous mixed light, but it consists of lighting surface elements of defined size and of different colours /e.g.

coloured TV, coloured printing technique etc./.

In the case of an arrangement consisting of a known light source, mirror, and colour filter, from a lot of refractive means of predetermined size and shape, a screen may be formed, the surface elements of which--cor- responding to the size of the refractive means -are alternately illuminated with an intensity and colour complying with the colour of the three sources of light and simultaneously radiate the trasversing light energy to the desired solid angle in a uniform distribution. The invention will be described in detail by means of Figs. 3 to 13.

Let us place two prisms of angles of refraction of a and ss, respectively, beside each other in accordance with Fig. 3 and allow a parallel monochromatic beam of light to fall on the two prisms, perpendicularly to the common median plane; the beam of rays will transverse the two prisms in accordance with the angle of refraction, having been refracted at the angles y and 8 respectively, through the cross-sections A and B.Disregarding edge effects and effects caused by a complete refraction, the direction of the ray path may be reversed, in this case the rays starting from the cross-section A and arriving at an angle of arrival y, as well as the rays coming from the cross-section B and arriving at an angle 8 are leaving the prisms perpendicularly to the common median plane and run in parallel with each other /Fig. 4/.

Accordingly, by this arrangement the two parallel beams of rays--enclosing an angle y + 8 with each other-may be united into one single parallel beam of rays.

In the case where the beams of rays starting from the cross-sections A and B are of different colours, e.g. red and blue, then the upper part of the united parallel beam of rays will be red, the lower one blue and theoretically they run in parallel with each other to the infinity.

In the case where we place a focussing lens or a concave dispersing lens into the path of both of the red /upper/ and the blue /lower/ part of the beam of the rays, the path of the ray illustrated in Fig. 5 or 6 may be obtained.

In both cases, in the spatial parts indicated by cross-hatching, the complete mixture of red and blue colours could be obtained. If somebody is viewing said arrangement as a lightdisplay from the spatial part indicated by the cross-hatching, viewed from a short distance, a light point each illuminated in red and blue colour, respectively, may be seen. However, if in the same spatial part the arrangement is viewed from a distance, from which the distance between the two light points is to be seen at a smaller visual angle than the resolving power of the eye, one single illuminating point will be seen, lighting in a colour which corresponds to the mixture of the two colours, in our case to violet.

The solid angle of the spatial parts indicated by the cross-hatching depends on the geometrical size /curvature/ and the refractive index of the focussing lens and the concave dispersing lens, respectively. The size of the lens required for the realization of the desired solid angle may be calculated in accordance with the laws of geometrical optics.

In practice the individual preparation of the prisms and lens, however, may involve certain difficulties. The effect exerted by the device mentioned may be produced, however, with certain restrictions, in such a manner that the concave or convex surfaces are formed on one or both surfaces of the refractive prism, as may be seen in Fig. 7.

The prism system illustrated in Fig. 8 has been produced by the multiplication of the prisms shown in Fig. 7. It goes without saying that the same effect can be obtained as by means of the prisms shown in Fig. 2, but it is well suitable for guiding broader beams of rays in a common direction. In the case where the cubic prisms are simultaneously multiplied in the direction lying perpendicularly to the plane of the paper, we shall obtain a screen which is suitabble for mixing two colours.

It is obvious that the multiplication is followed by a phenomenon which cannot be disregarded. In order to understand the phenomenon, let us examine Fig. 9. In the case of a multiple prism system only the "a" part of the beam of rays arriving from the crosssection A advances in the desired direction, while the part "b" is scattered outside the useful spatial area. That means, that the fraction a a+b of the beam of rays arriving at the screen may be guided in the desired direction.

In the arrangement illustrated in said figure "a" is less than "b", as a consequence, less than 50% of the light streaming through the cross-section A is allowed to pass through the screen.

Considerably more advantageous conditions may be achieved if the prisms are formed in accordance with Fig. 1 0. In this case, as may be seen in the figure, "a" is larger than "b", as a consequence, more than the half of the light stream streaming through the cross-section A is able to pass through the screen into the desired solid angle.

In the case where the screen is used for mixing the light of three light sources of different colour and guiding the light to the desired solid angle, the light stream passing through the screen still amounts to about 50%, accordingly, approximately the same rate may be obtained as in the known solution, where translucent materials are used.

Accordingly, by using the proposed solution, it becomes possible to guide the light quantity passing through the screen in its entirety into the desired solid angle, thus a considerably better exploitation of the light energy may be obtained.

If we wanted to ensure the proper mixing of the light in a solid angle complying e.g. to the apex angle of 60 of a cone, by using the solution according to the invention, then compared with known solutions the surface brightness will be ninefold for the same capacity (output) of the light source.

A preferred embodiment according to the invention has been illustrated in Fig. 11.

The light-displaying unit contains-similarly to known embodiments-the light sources 2, the light reflectors 3, as well as the colour filters 4, arranged in the light deflecting tube 1. All the light-reflectors are oriented in such a manner that the beams of the rays of light sources should be reflected through a colour filter each onto the identical surface of the plane 5' on the frontal surface. In the plane 5' numerous refractive prisms are arranged, the refractive angles of which are formed in accordance with the angle enclosed by the beams of rays and the plane 5'.Here the prisms arranged in the plane 5' are individually turned in such a manner that one group of the prisms should deflect the rays of one colour /e.g. red/, the other group another colour /e.g. green/ and the third group the rays of the third colour /e.g. blue/ to the desired solid angle /Fig. 12/.

Advantageously this operation is performed in such a manner that to the rays of all the three colours prisms of an identical number or quantity /or at least approximately identical/ should be co-ordinated, and the prisms belonging to the different colours should be arranged along the surface in a cyclically alternating order of sequence.

Advantageously, the cross-section of the prisms related to the plane 5' should be chosen in such a manner that three prisms each should form in their turned position a regular hexagon /accordingly, each prism should have a diamond-shaped cross-section with angles of 120 /, because in this case the surface may be filled with prisms without any loss of the surface /Fig. 13/.

From the facts described here it becomes obvious what kind of construction is to be realized by the light-display according to the invention. In knowledge of this fact the invention can be translated into practice, i.e. in such a manner that at the place of operation the optical elements known per se are arranged and adjusted so that the construction previously described could be achieved. In this case the invention is not constituted by the formation of the optical elements, but rather by the selection of the suitable elements from the mass of the known elements, as well as in their local (positional and spatial) relative arrangement.

For realizing the process, light sources of different colours of a number N /N may equal e.g. to 3/ individually provided with light reflectors, are used; the light energy delivered by the single light sources /e.g. the first, the second and the third/ in concentrated onto the light-displaying plane, i.e. onto the useful surface designated in said plane, where the light energies delivered from all light sources are united to one single cone of rays leaving the useful surface.Along the light displaying plane a mass of elementary light deflecting means /light deflectors/ are arranged in such a manner that the adjacent light deflectors should be alternately optically coupled to the different light sources /e.g. in the order of sequence to the order of sequence to the first, the second and to the third, then repeatedly to the first/; the light-deflecting group of the number N thus obtained (by "light-deflecting group" the totality of the light-deflectors connected to the same light source is meant) is put into the operational position in such a manner that all light reflectors belonging to the single groups are rotated in synchronism while the angular position of the single lightdeflecting groups /being common for each group/ is to be changed as long as the direction of progress of the beams of rays of different basic colour, forming the ray cone leaving the light-display plane, remain perpendicular to the light-displaying plane or the cones of rays of the same colour are advancing on conical paths, where the axes of the cones are perpendicular to the light-displaying plane.

In accordance with an advantageous embodiment of the invention K X N light-deflectors are used /K being a natural whole num ber/, while each light-deflecting group consists of K light-deflectors. Preferably lightrefractive devices are used as light-reflecting means, e.g. lenses, prisms, and/or the combination thereof. Light-deflection can be realized not only by means of light-refractive elements, flexible light-conducting bands etc. may also be successfully applied.

It goes without saying that in general operation is not obtained by the local empirical assembly of the means, but in the knowledge of the above-described principle, the equip ment is to be designed and produced by using the most up-to-date production technologies. When planning the equipment, one may start from empirically experimented optical systems, but in knowledge of the described facts, the experimental methods need not be followed. In the knowledge of the optical rules the proper selection of the shape and arrangement of the light-deflecting means may be performed with the aid of mathematical, geometrical and optical designs; moreover, up-to-date computation-technical auxiliary means can be used.The mass of prisms, lens and combined optical systems of predeter mined size and refractive angle may be produced with a high productivity by casting glass or by injection moulding of any conve nient synthetic material, by using expedient tools. It is proposed to use the diamond shaped elementary prisms shown in Fig. 13; in this case the tools may be composed of hexagonal pnsms in a mosaic-like arrangement.

The preparation of the tools may be facilitated by using the concept according to Figs.

9 and 10; a more advantageous exploitation of light may be obtained when the side of the elementary prisms facing the inside of the light-displaying unit are co-planarly arranged.

For the sake of good order it should be mentioned, that arranging the light-deflecting means along a plane does not involve the prerequisite that the side facing the plane, where the light is leaving, must be formed of a plane parallel to the light-displaying plane; on the contrary, this is either a relief-like surface obtained by rotating the planar surfaces of the three prisms into a convenient angle, or the surface of the elementary light-refractive element may be formed concave or convex, since it need not be a single plane at all.

Besides arranging the light-deflecting elements in accordance with the invention, further supplementary solutions improving the image effect may also be applied. In known equipments a screen system used to be applied lying in a plane parallel to the lightdisplaying plane for improving the contrast effect /see e.g. the Hungarian Patent Application No. Vl-1 215/. Of course, the equipment according to the invention may be combined with such contrast-improving means.

From the aforesaid it emerges that the equipment according to the invention may be realized in several versions and forms. The common characteristics of all the realizations lie in that along the plane before the light source /i.e. the light-displaying plane/ a plurality of elementary light-deflecting means /light-deflectors/ are arranged in such a manner that the adjacent light-deflectors are optically and alternatively coupled to the different light sources and all the optical axes of the light egressing surfaces of the light-deflector optically coupled to identical light-sources run in parallel with each other.

In a preferred embodiment of the invention the light-deflectors are formed by light-refractive means, e.g. refractive optical systems consisting of prisms, lenses and/or the combi-; nation thereof. From the point of view of production technology, the equipment formed with three light souces seems to be particu larly advantageous in which the adjacent lightrefractive means-the number of which always amounts to threeoptically coupled to different light sources form a complete optical system, and are built up in such a manner that the resultant cross-sections of the three prisms related to the light-displaying plane should form a regular hexagon.

Claims (10)

1. A process for the realization of coloured light-display by using light sources of different colours in a number N (N may equal e.g. to 3), individually provided with light reflectors, in the course of which the light energy delivered by the single light sources /e.g. the first, second and third one/ is concentrated onto the light-displaying plane, i.e. onto the useful surface designated here, where the light energies delivered from all the light-sources are united to one single cone of rays leaving the useful surface, characterized in that along the light-displaying plane a plurality of elementary light-deflecting means /light-deflectors/ are arranged in such a manner that the adjacent light deflectors are alternately optically coupled to the different light sources, e.g. in the order of sequence to the first, second and third one, then repeatedly to the first etc., the light-deflecting group thus obtained, (the number of which amount to N, and where under "a light-deflecting group the totality of the light-deflectors connected to the same light-source is meant) is put into the operational position in such a manner that all lightdeflectors belonging to the single groups are rotated in synchronism, while the angular position of the single light-deflecting groups being common for each groups to be changed as long as the direction of progress of the beams of rays of different basic colours forming the ray cone leaving the light-displaying plane are perpendicular to the light-displaying plane or the cone of rays of the same colour advance on conical paths, where the axes of the cones are lying perpendicular to the light-displaying plane.

2. A process as claimed in claim 1, characterized in that K X N light-deflectors are used /K being a natural whole number/ and every light-deflecting group consists of K light-deflectors.

3. A process as claimed in claim 1 or 2, characterized in that as light-deflectors lightrefractive means, e.g. prisms, lenses or any suitable combination thereof are used.

4. Light-displaying equipment with N /e.g. 3/ light-sources of different colour, individually provided with reflectors, characterized in that in the plane lying before the light sources /the light-displaying plane/ a plurality of elementary light-deflecting means (lightdeflectors) are arranged in such a manner that adjacent light-deflectors are optically coupled to different light sources in an alternating order of sequence, and the optical axes of the surfaces, where the light is egressing, being optically coupled to the same light source, run in parallel with each other.

5. Equipment as claimed in claim 4, characterized in that the light-deflecting means are refractive means, e.g. prisms, lenses and/or refractive optical systems formed from any suitable combination thereof.

6. Equipment as claimed in claim 5, characterized in that N equals to 3 and the adjacent refractive means, the number of which always amounts to three and which are optically coupled to different light sources, form an assembled optical system.

7. Equipment as claimed in claim 6, characterized in that in the assembled optical system the prisms optically coupled to three different light sources and forming edges are mutually assembled in such a manner that the resultant cross-section of the three prisms related to the light-displaying plane should form a regular hexagon.

8. A process for producing a light display according to claim 1 substantially as herein described with reference to and as shown in the accompanying drawings.

9. Equipment for producing a light display according to claim 4 substantially as herein described with reference to and as shown in the accompanying drawings.

10. A coloured light-display whenever produced by the process claimed in any of claims 1 to 3 or 8.