NL1024395C2 - Lighting system, light room and display device. - Google Patents

Description

Lighting system, light room and display device

The invention relates to an illumination system for illuminating an image, comprising a light-emitting panel with a light emission window, an opposite rear wall, and furthermore at least one light coupling surface located between the light emission window and the rear wall for coupling light from a light source in the light-emitting panel, wherein, in operation, the light spreads in the light-emitting panel.

The invention furthermore relates to a light chamber for use in an illumination system and to a display device provided with the illumination system.

Such lighting systems are known per se and are also referred to as edge lighting systems. They are used, among other things, as back lighting for translucent images, for example a sheet of paper, a film, a foil or a (color) photo, for example for advertising applications, for example in shops, offices, 15 shelters and at exhibitions. The lighting systems are also used as signposting (both inside and outside), for example at airports and public buildings. Such lighting systems are also used for decorative purposes.

In the lighting systems mentioned in the preamble, a tubular low-pressure mercury vapor discharge lamp is generally used as the light source 20, for example one or more compact fluorescent lamp (s), wherein the light emitted by the light source during operation is coupled into the light-emitting panel which acts as a light guide. That light conductor generally forms a relatively thin and flat panel which is for instance manufactured from a plastic or glass, and wherein, inter alia under the influence of (total) internal reflection, light is transported through the light conductor.

As an alternative light source, such an illumination system can also be provided with a plurality of opto-electronic elements, for example light-emitting diodes (LEDs). A further alternative light source is a laser diode. These light sources are generally disposed in the vicinity of or abut against a light interface 1024395

of the light-emitting panel, wherein, in operation, light from the light source is incident on I

the light-transmitting edge surface and spreads into the panel. I

From WO-A 02/50 473 a lighting system is known that a light-emitting I

panel, wherein one or more light sources are arranged which via an I

light coupling surface coupling light into the light-emitting panel, which light then I

diffuses into the light-emitting panel. The light interface is between an I

light emission window and the rear wall of the light-emitting panel. In the well-known I

The illumination system becomes the distribution of the light that is controlled by the light-emitting panel

effected by applying a suitable pattern of I

light-scattering elements on the rear wall of the light-emitting panel. I

An illumination system of the above-mentioned type has the disadvantage that the H

light distribution in the light-emitting panel is not sufficiently uniform. This makes it too I

15 illuminating image is not illuminated sufficiently evenly. I

The invention has for its object to completely or partially eliminate the aforementioned drawback

overcome. More particularly, it is an object of the invention to provide an illumination system of the type mentioned in the preamble, wherein the uniformity of the light distribution of the illumination system and hence the uniformity with which the image is illuminated is

improved. I

This object is achieved according to the invention in that the I

light emission window is provided with a pattern of light-scattering elements. I

The light-scattering elements have the property that they are light I

scatter (scatter). Preferably, the light-scattering elements scatter the light I

in all directions, for example according to a so-called Lambertian division. A portion

of the light can thus leave the light-emitting panel via the light emission window I

and is useful to illuminate the image. By varying the size, shape and I

The placement of the light-scattering elements becomes the aperture of the light-emission window I

affected. With the variation of the aperture, the internal reflection in the light-emitting I becomes I

panel and thus the light distribution in the light-emitting panel. As the I

If the number of internal reflections increases, the light distribution in the light-emitting panel becomes more I

homogeneous and increases the light output of the light emitting I due to increasing damping

1024395 I

3 panel. As the number of internal reflections decreases, the light distribution in the light-emitting panel becomes less homogeneous and the light output increases due to reduced dancing. By a suitable choice of the size, shape and placement of the light-scattering elements, a homogeneous light distribution is achieved in combination with a relatively high light output.

In the known illumination system, a pattern of light-scattering elements is applied to the rear wall of the light-emitting panel. In the illumination system according to the invention, a pattern of light-scattering elements is applied to the light emission window of the light-emitting panel. As a result, the light distribution in the light-emitting panel is controlled in consultation with the amount of light emitted by the light emission window. The measure according to the invention improves the uniformity of the distribution of the light emitted by the illumination system. This provides a more even illumination of the image to be displayed.

Further advantages of providing an exposure system according to the invention are that simpler and / or cheaper images can be used that nevertheless obtain a good appearance. The appearance of the image using the exposure system according to the invention is improved. Due to the improved uniformity of the light distribution, the designer of the image to be displayed has more technical freedom when designing the image. A uniform background color can thus be applied. If a uniform background color were to be applied in the known illumination system, small variations in the light distribution are clearly visible to the observer.

Preferably, the pattern of light scattering elements comprises a plurality of discrete markings on the surface of the light emission window. Such markings, also called spots, can be applied relatively easily to the surface of the light emission window. The markings can be distributed homogeneously over the surface of the light emission window. If the size of the markers and the distribution of the markers varies across the surface of the light emission window, special effects can be achieved. The attracting value of the displayed image can hereby be increased.

Preferably, the markings are at least substantially homogeneously distributed over at least substantially the entire surface of the light emission window. This leads to the smoothest possible illumination of the image to be displayed by the illumination system.

1024395 A favorable embodiment of the illumination system is characterized in that the number of marks per surface unit is between 10 and 50 I marks per cm 2, preferably between 16 and 25 marks per cm 2. With the magnitude of I and the distance between the markings, the aperture of the light emission window is adjustable from I about 20% to about 80%.

The markings preferably form small bulges on the surface of the light emission window. Preferably, the shape of the markings is selected from the group consisting of spheres, cones, pyramids, and pearl pipids, and parts of spheres, cones, pyramids, and pearl pipids. Such shapes are relatively easy to apply to the surface of the light emission window.

A preferred embodiment of the illumination system has the feature that the rear wall is provided with a reflective layer on a side remote from the light-emitting panel. Such a reflective layer increases the light output of the illumination system.

Preferably, the reflective layer is diffusely reflective. Such a diffuse reflective layer increases the homogeneity of the light distribution in the light-emitting panel. The diffuse reflective layer increases the viewing angle of the illumination system.

The reflective layer is, preferably, arranged at a distance from the rear wall. Such a reflective layer can simply be accommodated in the illumination system as a loose layer, for example in the form of a reflective film.

An alternative preferred embodiment of the illumination system is characterized in that the reflecting layer is provided on a side facing the light-emitting panel with a pattern of light-scattering elements. Preferably, the I pattern of the light scattering elements comprises a plurality of discrete markings on the I surface of the reflective layer. The application of a second scatter layer increases the number of internal reflections in the light-emitting panel.

A favorable embodiment of the illumination system is characterized in that the light emission window is provided with a light-diffusing layer on a side remote from the light-emitting panel. Such a light-scattering layer increases the viewing angle of the illumination system. The light-diffusing layer is preferably arranged at a distance from the light emission window. This simplifies the assembly of the illumination system.

I 1024395-5

An alternative, preferred embodiment of the illumination system is characterized in that a light chamber for accommodating a light source is associated with the light interface, and that the light chamber is provided with a reflective foil or layer for directing, in operation, the light originating from the light source to the light interface. The light chamber according to the invention is simple in construction and inexpensive to manufacture. The reflective film or layer causes the light from the light source to be directed towards the light interface of the light-emitting panel. The reflective film or layer preferably extends over a part of the light emission window and / or the rear wall of the light-emitting panel. Such a construction promotes the coupling of light from the light chamber into the light-emitting panel.

The invention will now be described in more detail with reference to a number of exemplary embodiments and a drawing.

It shows:

Figure 1 shows an embodiment of the illumination system according to the invention in cross-section;

Figure 2 shows an alternative embodiment of the illumination system according to the invention in cross-section;

Figure 3 shows a further alternative embodiment of the illumination system according to the invention in cross-section, and

Figure 4 shows the light intensity (English “luminance”) of the light measured at the light emission window of the illumination system as shown in Figures 1 and 3.

The figures are purely schematic and not drawn to scale. In particular, for the sake of clarity, some dimensions are strongly exaggerated. Similar parts are indicated in the figures as much as possible with comparable reference numerals.

30

Figure 1 schematically shows an embodiment of the illumination system according to the invention in cross-section. The illumination system comprises a light-emitting panel 1 of a light-transmitting material. The panel 1 is, for example, made of a plastic, of acrylic, of polycarbonate, of pmma, for example perspex, or of glass.

1024395 I 6 I A particularly suitable material with a high optical clarity is methyl methacrylate I (mma). The light-emitting panel can have a variety of dimensions. Due to the measure according to the invention, relatively large light-emitting panels can also be used. Exposure systems with dimensions of the panel LxWxT = 2000x3000x10 mm I 5 while maintaining the uniformity of the light distribution have been realized. I L represents the length of the panel, W the width of the panel and T the thickness of the panel I. Particularly suitable is an illumination system with a light-emitting panel the size of, for example, A1 format, where LxWxT = 935x630x10 mm.

Under the influence of total internal reflection, during operation, light is transported through the panel 1. The light-emitting panel 1 has a light emission window

2 and an opposite rear wall 3. Between the light emission window 2 and the I

rear wall 3 is furthermore a light coupling surface 4 for coupling in light from I

I a light source 6 in the light-emitting panel 1. The illumination system further comprises an I

I light chamber 5 (very schematically indicated in Figure 1) provided with a light source 6. The I

The light chamber in Figure 1 is provided with a hinge 5 "for easy access I

I make the lighting system. A tubular I is usually used as the light source 6

I low-pressure mercury vapor discharge lamp used, for example one or more (compact) I

fluorescent lamp (s). A variety of optics can also be used as an alternative light source

I electronic elements, such as light-emitting diodes (LEDs), are used. I

For lighting systems of relatively small dimensions, one light chamber is I

I sufficient. For lighting systems with relatively large dimensions, two I is usually used

I light chambers applied on opposite sides of the light-emitting panel. I

The light chamber (s) is / are preferably located parallel to the long side (s) of the I

light-emitting panel. I

The light chamber 5 is associated with the light coupling surface 4, with which I

I means that the light chamber 5 is coupled to the light coupling surface 4 such that the light I

I that is generated in the light chamber 5 via the light coupling surface 4 becomes optimum

I connected to the light-emitting panel 1. In operation, light from the light source I falls

I6 onto the light-transmitting edge surface 4 and spreads into the light-emitting panel I

1. The light from the light source 6 can be used either directly or via (multiple) reflections I

I reach the light coupling surface against the walls of the light chamber 5. Furthermore, in Figure 1 I

The light chamber 5 is provided with a reflective foil 7 or layer for directing, in operation, I

I of the light from the light source 6 to the light interface 4. In the example of I

Figure 1, the reflective foil 7 extends over a part of the light emission window 2 and I

I 1024395 7 of the rear wall 3 of the light-emitting panel 1. This promotes the coupling of light from the light chamber 5 into the light-emitting panel 1. There can be a diffuser (not shown in Figure 1) between the light chamber 5 and the light coupling surface 4 for promoting the mixing of the light from the light chamber 5. Preferably, such a solid diffuser does not form an additional interface between the light chamber 5 and the light-emitting panel 1. The light chamber 5 can be manufactured in a simple manner, and comprises, for example, a housing of suitably folded metal plate.

A sensor (not shown in Figure 1) may be provided in the light chamber 5 for measuring the optical properties of the light that, in operation, is emitted by the light source 106. This sensor is linked to control electronics (not shown in

Fig. 1) for suitably adjusting the luminous flux of the light source 6 to the desired brightness and / or color point of the light to be coupled out by the light-emitting panel. A feedback mechanism can be realized with the aid of the sensor and the control electronics for influencing the quality and quantity of the light to be coupled out of the light-emitting panel 1

In Figure 1, reference numeral 13 shows a (translucent) image to be displayed by the exposure system. Suitable translucent images are, for example, a sheet of paper or a foil provided with an image, a film image, or a (color) photo. Combinations of images are also possible. The assembly of the light-emitting panel 1, the light source 6 and the image 13 forms a display device for displaying, for example, (video) images. To protect the image 13, for example from scratches or stains, a protective layer 15 is provided in the example of Figure 1. The light emitted by the light-emitting panel illuminates the translucent image 13 and leaves the illumination system according to the arrows as indicated in Figure. 1.

In order to increase the light output of the illumination system, the rear wall 3 of the light-emitting panel 1, on a side remote from the light-emitting panel 1, is provided with a reflective layer 9. In the example of Figure 1, the reflective layer 9 is spaced from the rear wall 3 is arranged. In a favorable embodiment, the reflective layer 9 is diffusely reflective.

In order to increase the viewing angle of the illumination system, the light emission window 2 is provided on a side remote from the light-emitting panel 1 with a light-diffusing layer 11. In the example of Figure 1, the light-diffusing layer 11 is spaced from the light emission window 2. applied.

1024395

I 8 I

According to the invention, the light emission window 2 is of the light-emitting I

I panel 1 provided with a pattern of light-scattering elements 8,8 ", .... The pattern I

I of the light-scattering elements 8,8 ", ... preferably comprises a plurality of discrete I

I markings on the surface of the light emission window 2. I

The markers are preferably homogeneous across the surface of the I

I light emission window 2 distributed. This leads to the most uniform possible illumination of the I

I the image to be displayed in the exposure system. If the size of the markers and the I

The distribution of the markers varies over the surface of the light emission window 2 I

I special effects can be achieved. For example, I

Certain parts of the surface of the light emission window 2 emit more light than I

I other parts; the corresponding parts of the image can in this way have an additional I

Obtain a radiance relative to their environment (for example the product itself or an I

I radius around the product), which is the attractive value of the displayed product

I increased. I

The number of markings per unit area is, preferably, located I

I between 10 and 50 marks per cm2. A number of markings per I is particularly suitable

I surface unit located between 16 and 25 marks per cm2. Preferably, the I

I size of the marks between 1 and 2.5 mm and the distance between the marks between I

0.5 and 2.5 mm. With the size of and the distance between the marks, the aperture is I

The light emission window is adjustable from approximately 20% to approximately 80%. The height of the I

I markings range from 0.002 to 0.25 mm, a height of I is particularly suitable

I 0.10-0.15 mm. I

The markings form, preferably, small bulges on the surface

I of the light emission window. These markings include (patterns of) distortions and I

I include, for example, screen-printed dots, wedges and / or creases. The markings are I

For example by etching, scratching or sandblasting in the light emission window 2 of I

I applied the panel 1 Alternative ways of applying the markings are I

I grinding, laser treatment or cutting. The markings can be flat, convex and / or polygonal I

I are. Particularly suitable markings are spheres, cones, pyramids, and parallelelle and I

I 30 parts of spheres, cones, pyramids and pearl pipids. Such forms are I

Relatively easy to apply to the surface of the light emission window, I

For example by means of roll or screen printing techniques. The markers act as an I

I secondary light source and couple out light from the light-emitting panel 1 by reflection, I

I scattering and / or refraction. The markings that are irradiated from the I

I 1024395 9 light-emitting panel 1 have the property of scattering the light in all directions (scattering). As a result, a portion of the light exits from the light-emitting panel 1 and a portion of the light is reflected and remains in the light-emitting panel 1. By a suitable choice of the size, shape and placement of the light-scattering elements, the aperture of the light-emitting can panel can be arranged between 23 and 77%. By varying the aperture, the internal reflection of the light-emitting panel is influenced and the light distribution is adjusted to the size of the light-emitting panel 1. In this way, an illumination system with a homogeneous light distribution in combination with a relatively high light output is achieved.

Figure 2 schematically shows an alternative embodiment of the illumination system according to the invention in cross-section. Corresponding components are designated in Figures 1 and 2 with the same reference numerals. In Figure 2, the light-emitting panel 1 is provided with a pattern of light-scattering elements 18, 18 ', ... Preferably, the pattern of the light-scattering elements 18, 18', ... comprises a plurality of discrete markings on the surface of the reflective layer 9. Applying a second scatter layer increases the number of internal reflections in the light-emitting panel 1. In an alternative embodiment of the illumination system (not shown in Figure 1), the rear wall 3 is provided with a pattern of light-scattering elements, which pattern, preferably, comprises a plurality of discrete markings on the surface of the rear wall 3.

In the example of Figure 2, the reflective foil 7 comprises a trapezoidal mirror which is built up from one or more mirrors. The placement of the sub-mirrors is preferably chosen such that the reflected light is not sent back in the direction of the light source 6. Preferably, a trapezoid-shaped mirror is also used such that when opening the light chamber 5 via the hinge 5 ' the light source 6 becomes easily accessible

Figure 3 schematically shows a further alternative embodiment of the illumination system according to the invention in cross-section. Corresponding components are designated in Figures 1 and 3 with the same reference numerals. In the illumination system 30 as shown in Figure 3, the rear wall 3 also functions as a light emission window and is provided with a pattern of the light-scattering elements 28, 28 ', .... There is a light-scattering layer on either side of the light-emitting panel 1 in Figure 3. 11,11 ', an image 13,13' and a protective layer 15,15 '. The light emitted by the light-emitting panel in Figure 3 illuminates the translucent images 13, 13 "and leaves it 1024395

10 I

illumination system on opposite sides according to the arrows as indicated in I

Figure 3. I

Figure 4 shows the light intensity Lu (English “luminance”) of the light measured I

to the light emission window of the illumination system as shown in Figures 1 and 3. In both I

In 5 cases it concerns an illumination system with a length of approximately 0.94 m where I

a light chamber with light source is provided on both sides. The brightness measurements I

are performed without an image being applied to the exposure system. Curve (1) shows I

the luminous intensity as1 function of the distance of the illumination system that a single-sided light I

(Figure 1). Curve (2) shows the brightness as1 function of the distance of the I

10 illumination system that radiates a two-sided light (Figure 2). Near the edges of the I

light emission window shows a small effect of the coupling of the light from the I

light rooms. The measurements show that the light distribution over the whole of the I

The light emission window of the light-emitting panel is sufficiently uniform everywhere, even in the I

near the light source. With the exposure system according to the invention, the image becomes I

IS sufficiently uniformly highlighted I

It will be clear that within the scope of the invention for the person skilled in the art I

Many variations are possible. I

The scope of the invention is not limited to the given I

exemplary embodiments. The invention lies in every new feature and every combination I

20 of features. Reference numerals in the claims do not limit the scope of protection I

thereof. Use of the word "include" does not exclude the I

presence of elements other than stated in the claims. Use of the word I

"A" (English: "a" or "an") preceding an element does not exclude the presence of I

a multitude of such elements. I

1024395 I

Claims (18)

An illumination system for illuminating an image (13), comprising a light-emitting panel (1) with a light emission window (2), an opposite rear wall (3), and furthermore at least one light coupling surface (4) located between the light emission window (2) and the rear wall (3) for coupling light from a light source (6) into the light-emitting panel (1), wherein, in operation, the light spreads into the light-emitting panel (1), characterized in that the light emission window (2) is provided with a pattern of 10 light-scattering elements (8,8 ', ...). 2. An illumination system according to claim 1, characterized in that the pattern of the light-scattering elements (8,8 ", ...) comprises a plurality of discrete markings on the surface of the light-emission window (2). An illumination system according to claim 2, characterized in that the markings are distributed at least substantially homogeneously over at least substantially the entire surface of the light emission window (2). An illumination system according to claim 2 or 3, characterized in that the number of marks per surface unit is between 10 and 50 marks per cm 2, preferably between 16 and 25 marks per cm 2. 5. An illumination system as claimed in Claim 2, 3 or 4, characterized in that the shape of the markings is selected from the group formed by spheres, cones, pyramids and pearl pipids and parts of spheres, cones, pyramids and pearl pellets. 1024395 I 12 I An illumination system according to any one of the preceding claims, characterized in that the rear wall (3) is provided on a side remote from the light-emitting panel (1) with a reflective layer (9). I 5 An illumination system according to claim 6, characterized in that the reflective layer (9) is diffusely reflective. I An illumination system according to claim 6 or 7, characterized in that the reflective layer (9) is arranged at a distance from the rear wall (3). An illumination system according to claim 6, 7 or 8, characterized in that the II reflective layer (9) on a side facing the light-emitting panel (1) is provided with a pattern of light-scattering elements (18, 18 ') , ...). I 15 An illumination system according to claim 9, characterized in that the pattern of the light-scattering elements (18, 18, ...) comprises a plurality of discrete markings on the surface of the reflective layer (9). I 11. An illumination system according to any one of the preceding claims, characterized in that the light emission window (2) is provided with a light-diffusing layer (11) on a side remote from the light-emitting panel (1). An illumination system according to claim 11, characterized in that the light-scattering layer (11) is arranged at a distance from the light-emission window (2). I 25 An illumination system according to any one of the preceding claims, characterized in that a light chamber (5) for accommodating a light source (6) is associated with the light coupling surface (4), and that the light chamber (5) is provided with a reflective foil (7) or layer for directing, in operation, the light from the light source (6) to the light interface (4). An illumination system according to claim 13, characterized in that the reflective film (7) or layer extends over a part of the light emission window (2) and / or the rear wall (3) of the light-emitting panel (1). 1024395 An illumination system according to any one of the preceding claims, characterized in that the rear wall (3) also functions as a light emission window and is provided with the pattern of the light-scattering elements (28, 28 ", ...). 5 A light chamber (5) for use in an illumination system according to claim 13 or 14. 17. A display device provided with an illumination system according to any one of the preceding claims. A display device according to claim 17, wherein the display device is provided with a translucent image (13), for example a photo. J 024395