Illumination arrangement

1

ILLUMINATION ARRANGEMENT

CROSS-REFERENCE TO RELATED
APPLICATIONS

This is a Continuation of copending International Application No. PCT/EP99/00310, filed Jan. 19, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention 10 The present invention relates to an illumination arrangement which comprises an illumination means and a light permeable base body having light permeable profiled bodies formed by recesses in the base body to direct light from the illumination means to a light emission surface of the base 15 body. In particular an illumination arrangement which can be used in light fittings, display screens etc. .

2. Description of the Related Art

Illumination arrangements of the kind set out above are 20 for example also employed as covers or screens for light fittings. Thereby it is already known to use screens having profiled bodies formed and projecting on the side towards a lamp of the lamp fitting, for directing the light of the lamp of the light fitting, in order to restrict the emission direction 25 of the light rays, for reducing dazzling of an observer. In GB-A-1365507 it is proposed for this purpose to form the profiled bodies in the shape of truncated pyramids, which project from the base body of the screen, the upper bounding surfaces of the truncated pyramids being coated with a light 30 impermeable material. In U.S. Pat. No. 3,351,753 there is likewise proposed a screen having profiled bodies in the shape of truncated pyramids, whereby however in this case the side surfaces of the truncated pyramids and the intermediate spaces between the truncated pyramids are coated 35 with a light impermeable material.

By means of these known screens there is achieved a directing of light suitable for restricting the angle of emission of the light rays, but due to the non-transparent regions of the screen the efficiency of the light fitting is reduced. In 40 AT-A-301/87 there was therefore proposed a screen for light fittings likewise having pyramid-like profiled bodies, which are arranged in a matrix form on the side of the base body of the screen towards the lamp of the light fitting and having an upper bounding surface running parallel to the emission 45 surface of the screen, the entire screen being of a transparent material.

The individual glass profiled bodies of this screen known from AT-A-301/87 are so configured that light emitted from the lamp of the light fitting onto the upper bounding surface 50 of the individual profiled bodies is carried by the profiled bodies to the emission surface of the screen and emitted there within a predetermined maximum emission angle range. However, since this form of screen is preferably employed together with elongate fluorescent lamps, prob- 55 lems appear in the coupling of the light emitted from the lamp employed into the glass profiled body, since the lamp naturally irradiates not only the upper bounding surfaces of the individual profiled bodies but also the (light permeable) side faces of the truncated-pyramid-like profiled bodies. 60 This, however, has the result that the desired maximum emission angle for avoiding dazzling of the observer cannot be maintained without further measures, since the light emitted from the lamp is not only directed towards the emission surface of the screen in the interior of the indi- 65 vidual profiled bodies, but is also reflected or refracted at the side surfaces of the profiled bodies.

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Further, there is known from EP 0 345 468 A2 an illumination arrangement as an broad area irradiator with which a plurality of luminescence semiconductor bodies, as luminous means, are applied to a light permeable base body in a extensive distribution. However, the base plate of this illumination arrangement has no profiled bodies for directing light, such as are for example known from the abovementioned AT-A-301/87.

Moreover, there is disclosed in U.S. Pat. No. 5,272,410 an illumination arrangement which comprises an illumination means and a light permeable base body having light permeable profiled bodies formed by recesses in the base body to direct light from the illumination means to a light emission surface of the base body. The illumination arrangement is in this case a light emitting body, which can be used for example as tail light for motor vehicles. It consists of two plates of which at least one has a series of prismatic recesses the walls of which are coated with a phosphorescent layer. The recesses contain a gas under partial vacuum. At the ends of the glass plates electrodes are arranged by means of which, through gas discharge in the recesses, light is generated at the phosphorescent layer, which light is emitted in various directions. The outside of one of the two glass plates is provided with a reflecting layer, so that this reflector and the prismatic structure of the recesses provide that the light is so directed that it is emitted at the side of the body away from the reflector. With this illumination arrangement, however, the light is not emitted at a restricted angle of emission for reducing dazzling of an observer.

SUMMARY OF THE INVENTION

The present invention thus has the object of providing an illumination arrangement having profiled bodies formed in a base body with which on the one hand the above-described light coupling into the individual profiled bodies is facilitated and on the other hand a higher optical efficiency, preferably with sufficient anti-dazzling effect, is realized.

In accordance with the present invention this object is achieved by means of an illumination arrangement of the type described above in regard to U.S. Pat. No. 5,272,410, wherein the luminous means are applied to upper bounding surfaces of the profiled bodies and emit light into corresponding profiled bodies through upper bounding surfaces thereof. In other aspects, the invention also includes further features, as will be seen from the specification. The subclaims describe preferred embodiments of the present invention, which for their part contribute to a manufacturability of the illumination arrangement in accordance with the invention which is as efficient as possible and allows series production, or contribute to a best possible optical efficiency with best possible anti-dazzling effect.

In accordance with the present invention there is applied directly on the profiled bodies of the illumination arrangement in accordance with the invention (in particular on the upper bounding surfaces of the profiled bodies), a luminous means which emits light into the corresponding profiled body. The profiled bodies are of a light permeable material and, in their interior, direct the light emitted from the luminous means towards the emission surface of the illumination arrangement, where the light of the luminous means is emitted. Thereby, the individual profiled bodies are preferably so configured that the illumination arrangement at each arbitrary point of its emission surface emits the light of the luminous means within a predetermined maximum emission angle range of for example 60° to 70° in order to avoid a dazzling of an observer due to too flatly emitted light.

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The individual profiled bodies may be formed for example in the manner of truncated pyramids, or elongate in the form of strips. As luminous means there may be considered for example a diffusely illuminating layer of organic or inorganic semiconductor materials, whereby electroluminescence is excited in these semiconductor materials by means of the application of electric voltage.

The profiled bodies of the illumination arrangement in accordance with the invention are separated from one another by means of recesses formed in the base body of the screen, whereby these recesses may in particular be V-shaped. The flanks of these recesses or the side flanks of the profiled bodies may be straight or curved. Advantageously, the side flanks of the profiled bodies are so formed as to be reflecting at their inner faces, so that the light is completely reflected within the profiled bodies. The same effect can be achieved by means of a configuration of the individual profiled bodies in such a way that in dependence upon the refractive index of the profiled bodies the light falls onto the inner faces of the side flanks of the profiled bodies exclusively at an angle of total reflection.

In accordance with a preferred exemplary embodiment, the individual profiled bodies are formed in a foil which is attached to a carrier of a light fitting, in particular glued thereto.

The advantage of the present invention consists in that the luminous means applied to the profiled bodies provide the light source for the corresponding illumination arrangement. If the luminous means are provided in the form of illuminating layers, a very flat illumination arrangement can correspondingly be realized. Since the luminous means are applied directly to the profiled bodies, with the illumination arrangement in accordance with the invention the abovedescribed problem of light coupling does not appear in practice. Since a light fitting with the illumination arrangement in accordance with the invention does not need a lamp or lamp mounting, no lamp changing is needed. Such a light fitting has, depending upon the luminous means employed in each case, a long lifetime.

The lighting arrangement in accordance with the invention can be employed in particular in combination with one or more flat fluorescent lamps, which serve as luminous means and bear directly on the upper bounding surfaces of the profiled bodies. In this manner the above-described advantages of the present invention can be combined with the advantages of such fluorescent lamps, such as e.g. a flat configuration and a constant, high light density.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below in more detail with reference to preferred exemplary embodiments.

FIG. 1 shows schematically a perspective view of a light fitting having an illumination arrangement in accordance with the invention, in the form of a screen,

FIGS. 2a and 2b show cross-sectional views of the lighting arrangement in accordance with the invention, according to first and second exemplary embodiments of the present invention,

FIG. 3 shows a perspective view of a preferred exemplary embodiment of the illumination arrangement in accordance with the invention, whereby two different variants are illustrated in FIG. 3,

FIGS. 4a and 4b show illustrations to an enlarged scale of a profiled body of the illumination arrangements illustrated in FIG. 2a or 2b, for explanation of the beam path within this profiled body, and

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FIGS. 5a and 5b show cross-sectional views of the illumination arrangement in accordance with the present invention, according to third and fourth exemplary embodiments of the present invention.

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DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS

FIG. 1 shows a perspective view of a light fitting formed to be elongate, with which the illumination arrangement in

10 accordance with the invention is employed as screen. As can be seen from FIG. 1, in the light fitting 1 an illumination arrangement or screen 2 is so held in a housing 9 that the emission surface of the screen 2 is directed downwardly. The emission surface of the screen 2 is preferably formed to be

15 flat. The screen 2 and the profiled bodies formed therein (and not seen in FIG. 1) are so configured that light is emitted from the emission surface of the screen 2 at any arbitrary point P solely within a particular maximum emission angle (non-dazzling angle) ymax. The emerging light rays corre

20 spondingly bound a conical surface 3. The relationships illustrated in FIG. 1 with regard to the point P apply analogously for all other points of the emission surface of the light fitting screen 2.

25 FIG. 3 shows a perspective view from above of a preferred exemplary embodiment of an illumination arrangement or screen 2 in accordance with the invention. More precisely, FIG. 3 shows a view from above of the surface of the screen 2 towards the light fitting housing. The screen 2

3Q has a plurality of profiled bodies 5 which are formed on or in a base body 4 of the screen 2. The individual profiled bodies 5 are spaced from one another by means of recesses 6. As is shown in FIG. 3, the profiled bodies 5 may have for example the form of truncated pyramids or elongate strips.

35 If the profiled bodies 5 are formed in the shape of truncated pyramids, the profiled bodies can be arranged uniformly in rows and columns, i.e. in the manner of a matrix, so that the recesses 6 between the individual truncated pyramids 5 form a grid. If the profiled bodies 5 are formed in the shape of

4Q strips, these are preferably arranged parallel to one another, so that the recesses arranged therebetween also run parallel to one another.

FIGS. 2a and 2b show exemplary cross-sectional views of the illumination arrangement in accordance with the

45 invention, along the chain-line section line illustrated in FIG. 3. Thereby, in FIGS. 2a and 2b, the side flanks of the individual profiled bodies are differently formed.

It is common to the exemplary embodiments illustrated in FIGS. 2a and 2b that the individual profiled bodies 5 are

50 separated by recesses 6 developing in substance V-shaped. The side flanks of the individual profiled bodies 5 fall away relatively steeply. On the underside of the base body 4, which represents the emission surface of the screen 2, there adjoins a substantially plane parallel section, which does not

55 in substance affect the beam path and is so formed in that the individual V-shaped incisions 6 cannot be carried completely through up to the underside of the base body 4.

The profiled bodies 5 are preferably produced in one piece with the base body 4 of a light permeable material. The

60 entire base body 4 including the profiled bodies 5 may be for example of acrylic glass. Advantageously, however, the base body 4 can be configured in the shape of a light permeable plastics foil in which the individual profiled bodies 5 are formed analogously to the known glass profiled body con

65 figuration. This plastics foil is then simply attached to a rectangular carrier of the light fitting, for example by gluing. By means of the employment of the plastics material, the manufacture of the base body 4 and the provision of the profiled bodies 5 in the base body 4 can be facilitated.

In accordance with the present invention, a luminous means 7 is applied on each profiled body 5. Preferably, the luminous means 7 is formed by means of a relatively thin 5 illumination layer, which is applied directly onto the upper bounding surface of each profiled body 5 and which may have a thickness of <1 mm. Each luminous means 7 emits light directly into the interior of the corresponding profiled body 5. The profiled bodies 5 are preferably so configured 1° that the light is completely reflected at the inner faces of their side flanks and directed towards the underside of the base body 4, i.e. to the emission surface of the screen 2. Further, the individual profiled bodies 5 satisfy geometrical conditions in order to be able to keep to the maximum :5 emission angle ymax shown in FIG. 1. The illumination layer 7 may for example be of an inorganic or organic semiconductor material and be applied by means of screen printing onto the individual profiled bodies 5.

As is shown in FIG. 2a, the side flanks of the profiled 20 bodies 5 or of the V-shaped recesses 6 may be straight. Instead of this, however, the bowed or curved development of these side flanks shown in FIG. 2b is also possible.

As has already been explained, there may be employed as ^ luminous means 7 for the profiled bodies 5 shown in FIGS. 2a and 2b for example organic or inorganic semiconductor materials. In dependence upon the respectively employed material, these materials are excited to be illuminated (electroluminescence) by the application of a d.c. or a.c. 3Q voltage. Corresponding electroluminescent foils or plates are already known.

Thus, the luminous means 7 may be formed for example by means of an electroluminescence illumination layer having luminous crystals arranged in a dielectric, whereby there 35 is applied to the luminous layer, via ITO electrodes (IndiumTin-Oxide), an electrical voltage for exciting the electroluminescence. Such electroluminescence illumination layers may have a thickness of <1 mm. Further, there can be employed as luminous layer a polymer film to which a 40 electric voltage is applied likewise via ITO electrodes. Upon application of the electric voltage positive charge carriers (holes) and negative charge carriers (electrons) are injected, whereby these different charge carriers recombine with the emission of light rays. The polymer film may for example be 45 of PPV and have a thickness of <1 fim. As luminous layer there can also be employed an arrangement of light emitting layers arranged one over another, which each emit light of different wavelengths, so that overall white light is emitted from the luminous layer. In general, in accordance with the 50 present invention, luminous means are preferably employed which emit diffuse light.

Has as already been explained, the individual profiled bodies must satisfy certain geometrical conditions, so that— as is shown in FIG. 1—light is emitted from the emission 55 surface of the illumination arrangement or screen 2 exclusively in the range 0°<ymax, to avoid dazzling an observer. These geometrical conditions depend in particular upon the refractive index of the luminous means 2 shown in FIG. 2, the refractive index of the material of the profiled bodies 5 go and the selected maximum emission angle (anti-dazzle angle) ymax. Preferably, as maximum emission angle ymax, there is selected an angle of 60°. In general, however, maximum emission angles ymax in the range 60° to 70° are sufficient. 65

The geometrical conditions of the respectively employed profiled bodies will be explained in more detail with refer

ence to FIGS. 4a and 4b. FIGS. 4a and 4b show 2D-projections of the profiled bodies 5, with luminous layers 7 applied thereto, illustrated in FIGS. 2a and 2b.

As is shown in FIG. 4a, light rays are emitted from the luminous layer 7 into the interior of the corresponding profiled body 5. These rays can leave the profiled body 5 without reflection at the side flanks 8 of the profiled body 5, which is indicated in FIG. 4a by means of the left ray path. Likewise, it is however also possible that certain light rays emitted from the luminous layer 7 are reflected at a side flank 8 of the profiled body 5 and only thereafter are emitted at the underside of the profiled body 5, which is indicated in FIG. 4a by means of the right ray path. In each case, the light rays emitted from the luminous layer 7 are refracted twice, namely once at the boundary surface between the luminous layer 7 and the profiled body 5 and a second time at the underside of the profiled body 5, when the light rays again leave the profiled body 5 and are emitted. In the following it is taken that nL is the refractive index of the luminous layer 7 and ns is the refractive index of the structural block or profiled body 5.

The directing of light within the profiled body 5, or the light emission from the profiled body 5, should substantially fulfill two conditions. On the one hand no light ray emitted from the luminous layer 7 into the profiled body 5 should be refracted sideways out of the profiled body 5, i.e. the light rays of the luminous layer 7 should emerge at the underside of the profiled body 5, either without reflection at the side flanks 8 of the profiled body 5, or being totally reflected at the side flanks 8 of the profiled body 5. Further, no light ray should leave the lower surface of the profiled body 5 with an angle which is greater than the desired maximum emission or anti-dazzle angle ymax. Advantageously, this maximum emission angle ymax is 60° in order for example in the case of employment of the illumination arrangement for room illumination, to attain an optimum anti-dazzle effect.

As has been explained above, the light rays emitted from the luminous layer 7 are refracted upon passing into the profiled body 5, in dependence upon the refractive index nL of the luminous layer 7 and the refractive index ns of the structural block or profiled body 5. Thereby, the following relationship exists between the angle of incidence (3 and the angle of refraction 8, in accordance with the laws of refraction:

In general upon a transition into an optically denser material, light rays are refracted towards the normal, whilst upon passing into an optically less dense material the light rays are refracted away from the normal. This means in the present case that the light rays emitted from the luminous layer 7, for ns>nL, are refracted into the structural block or profiled body 5, i.e. towards the normal, whilst for nL<ns, the light rays are refracted away from the normal.

If ns<nL, there occurs, from a certain maximum angle of incidence fimax a total reflection of the light rays emitted from the luminous layer 7 at the boundary surface to the profiled body, there applying:

Consequently, the angle 8 can take up the following maximum value in accordance with formula (1):

(3)

Of course, the above considerations apply also for the refraction of the light rays at the underside of the profiled body 5, whereby however in this case it is to be taken into 1° consideration that for the refractive index n of air, n=l.

As has already been explained, the light rays meeting the inner surfaces of the side flanks 8 of the profiled body 5 should be totally reflected. This can be attained for example 15 by means of a (light impermeable) mirroring of the inner surfaces of the side flanks 8, so that no light rays can be refracted sideways out of the profiled body 8. Instead of this, however, there can also be attained a total reflection analogous to the above-indicated formula (2) if it is ensured that 20 the light rays meet the side surface 8 at an angle e, with which—in accordance with the laws of refraction—the light rays are refracted completely into the optically more dense profiled body 5, i.e. the light rays must be incident with an angle e>em,„, whereby 25

(4)

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In dependence upon the above-explained conditions, the geometrical dimensions of the profiled body 5 shown in FIG. 4a or 4b can be calculated, whereby these dimensions are in particular dependent upon the predetermined refraction indices nL and ns and the desired maximum anti-dazzle angle Pmax- Thereby, in accordance with FIGS. 4a and 4b, it is assumed that the structural element or the profiled body 5 is arranged symmetrically to the y-axis and that the underside of the profiled body 5 forms the x-axis. Further, the profiled body 5 is to be so configured that the side flanks 8 run outwardly inclined from above downwardly. In the following, Yh indicates the height of the profiled body 5, 2xi indicates the width of the upper bounding surface and 2xa the width of the lower bounding surface of the profiled body 5.

With regard to the profiled body shape shown in FIG. 4a, along with the values for x,-, xa and Yh, of interest is in particular also the angle of inclination a of the side flanks 8 of the profiled body 5. Due to the desired total reflection at the side flanks 8 of the profiled body 5 there is yielded by means of an evaluation of the above indicated known relationships the following condition for the angle of inclination a:

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40

45

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The same procedure is possible in principle for the profiled body development shown in FIG. 4b. Thereby, however, due to the curved development of the side flanks 8 of the profiled body 5, it is assumed that the side flanks 8 develop in accordance with a predetermined function f(x), i.e. that:

y=f(x) for all |x|>x,- (9)

Thereby, in the following, it is assumed that suitable values for x,-, and yh are predetermined along with the development f(x), and in dependence thereupon solely the value xa is to be determined.

From the requirements relating to the total reflection at the side surfaces 8 of the profiled body 5 there is yielded the following condition:

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In dependence upon the predetermined values for x,- and yh, the likewise predetermined function f(x) is now to be solved for all x with |x|>x,-, taking into account the aboveindicated conditions (10)-(12), until a value for Xa is found which fulfills the condition according to formula (13).

FIGS. 5a and 5b show further exemplary embodiments of the present invention, whereby a flat fluorescent lamp is employed as light source or luminous means 7.

Flat fluorescent lamps are recent developments in the field of area irradiators. Referring to FIG. 5a, such flat fluorescent