EP2642470B1 - Panel-shaped light conducting element and light with a light conducting element - Google Patents

Description

The present invention relates to a luminaire which has at least one light source and a plate-shaped light-conducting element assigned to the light source, wherein light is coupled or radiated into the light-conducting element at the end and is emitted via at least one of its two flat sides. Furthermore, the present invention relates to a plate-shaped light-guiding element. The luminaire according to the invention may in particular be a so-called escape sign luminaire.

Lights of the generic type are intended to be perceived as a larger illuminated area or display. In particular, in the case of so-called escape sign lights here is a pictogram, which indicates, for example, the direction of an escape route, brightened to be well visible at any time, but especially in emergency situations. In such a case, it is desirable that the pictogram or the corresponding luminous surface of the luminaire is illuminated as uniformly as possible and, moreover, that it is also clearly recognizable from different directions. However, a uniform surface light output is desirable not only for escape sign lights. There are also luminaires used for room lighting, in which at least part of the light is emitted via a - in the rule - flat, areal light-emitting element. Even in such cases, it is usually desirable for optical reasons that on the one hand, the light emitting surface appears uniformly bright and on the other hand, the light is emitted symmetrically.

For realizing uniformly luminous surfaces, it is known from the prior art to use plate-shaped so-called light-guiding elements. These consist of a translucent material, in particular plastic, and are designed such that the incident of one or more end faces in the light guide light is transported by reflection and / or total reflection in the manner of a light guide, so that the light ultimately over the entire plate is distributed. With the aid of special so-called light extraction structures, which are introduced in one or both flat sides of the light-guiding element, the light striking there is then deflected in a targeted manner such that it can leave the light-conducting element via one of the two flat sides. Depending on the configuration of these Lichtauskoppelstrukturen can thereby Light emission are selectively influenced, so that in particular a uniform over the entire surface radiation is present. The light output structures may also be configured such that the light is emitted only within certain angular ranges or in preferred directions. Such arrangements for the delivery of light have proven useful, since they can be realized in a very flat design and despite all allow a uniform light output. In contrast, with the use of reflectors or other optical elements, which are arranged on the back of a light-transmitting radiating element, the overall height of the arrangement would increase significantly.

The aforementioned advantages of corresponding arrangements with a plate-shaped light-guiding element mean that such solutions are also used, in particular, for the realization of the escape sign luminaires already mentioned, since in this case a compact or flat design is desired. Since escape sign luminaires are often arranged projecting perpendicularly perpendicular to the ceiling of a room in the room, so are visible from all sides over the circumference, a flat design in this case has a particularly advantageous effect on the appearance of the lamp.

The already mentioned light extraction structures thus ensure that the light coupled in at the front side into the light guide element is emitted via the flat side or flat sides of the light guide element. If light sources are present only at one end face of the plate-shaped light-guiding element, light is transported within the light-guiding element primarily from the light source (s) away from the opposite end face. If the light is coupled out on the way there, the structures indeed cause a corresponding deflection of the light, despite this, however, rather in the direction of the light pipe, ie emitted from the light source to the outside, with the result that an asymmetric light output in With respect to a plane perpendicular to the light guide plane is achieved. Since, as already mentioned, in particular with escape route luminaires - but usually also with other luminaires for room lighting - rather a symmetrical light output is desired, measures must be taken to avoid such asymmetry. The simplest solution for this would, of course, be to arrange light sources symmetrically, that is, on two opposite end faces of the light guide, but this would mean an increased material and cost and also entail an increase in the dimensions of the light.

In the US 2010/0091520 A1 an arrangement is shown which has a light-guiding element and a light source, wherein the light source is arranged on the end face of the light-guiding element. The light-guiding element has structures for deflecting or decoupling the light emitted by the light source.

The present invention is now based on the object to provide a solution by means of which when using a plate-shaped light guide element and the frontal light coupling only from one side as symmetrical as possible light output can be achieved.

The object is achieved by a luminaire, which has the features of claim 1, and by a light guide according to claim 10. Advantageous developments of the invention are the subject of the dependent claims.

The solution according to the invention is based on the use of a special light extraction structure which, despite asymmetric light coupling, leads to the desired symmetrical light emission characteristic. This structure is arranged on the opposite flat side of the light-guiding element provided for emitting light and consists of wedge-like elevations aligned transversely to the light-guiding direction of the light-guiding element. Each elevation is here seen from the direction of the light entry surface designed such that it has a widening wedge region and a subsequent to the wedge region circular segment-like area, the wedge-like elevations are separated by flat surface areas of their length varies.

According to the invention, therefore, a luminaire with at least one light source and with a plate-shaped light guide element is proposed, wherein the light source is arranged on a light entry surface forming a narrow side of the light guide and the light guide is adapted to emit via the light entrance surface coupled light via a substantially perpendicular to the light entrance surface arranged light exit surface , It is provided according to the invention that the light guide is at least partially profiled on the side opposite the light exit surface side with juxtaposed wedge-like elevations, each elevation - seen from the direction of the light entry surface - a widening wedge region and a subsequent to the wedge region circular segment-like Has area and the wedge-like elevations seen in the optical fiber direction by plane Surface regions are separated from each other, wherein the length of the planar surface areas varies, in particular decreases in the light-guiding direction decreases.

It has been shown that the quality of the light output can be significantly optimized with the help of this special profiling. In particular, despite asymmetrical coupling of light into the light-guiding element, an almost symmetrical light output can be achieved. This makes it possible to realize very compact arrangements for emitting light, which has a positive effect, in particular, when, according to a preferred application example of the present invention, the luminaire is an escape sign luminaire.

The elevations of the structure according to the invention are preferably designed such that - seen in the light direction of the light guide - the ratio of the length of the wedge region to the length of the circular segment-like region is in the range of 4.5 to 7.5, preferably it is about 6.0. The ratio of the radius of the circular segment-like region to the length of the wedge region is further preferably in the range of about 0.15 to 0.21, preferably it is about 0.18. The wedge region and the circular segment-like region are preferably configured such that the wedge region merges tangentially into the circle-segment-like region, the center of the circular segment-like region being offset in this case in particular with respect to the surface of the light-conducting element.

In the event that the length of the planar surface areas decreases in the direction of light transmission, it follows that the density of the wedge-like elevations increases with increasing distance from the light source, resulting in the fact that across the entire width of the light guide away as uniform as possible homogeneous light emission achieved becomes. Thus, the light-guiding element not only gives off light symmetrically as desired, but also appears uniformly bright over its entire surface. The ratio of the length of the elevations to the length of the planar surface regions is preferably in the range from 0.5 to 1.1.

Depending on whether the lamp according to the invention is to be arranged on a wall or ceiling of a room or projecting from a wall or ceiling, it is usually desirable that the light output takes place only via one or both flat sides of the light guide. Depending on this, it may be provided that the wedge-like elevations designed according to the invention are arranged on one or both flat sides of the light-guiding element.

Fig. 1

ein Ausführungsbeispiel der vorliegenden Erfindung in Form einer Rettungszeichenleuchte in perspektivischer Ansicht;

Fig. 2

das Prinzip der Lichtleitung und Lichtauskopplung bei der erfindungsgemäßen Rettungszeichenleuchte;

Fig. 3

eine vergrößerte Ansicht der Wirkung der erfindungsgemäßen Lichtauskoppelstrukturen;

Fig. 4 bis 6

Ansichten der erfindungsgemäßen Lichtauskoppelstruktur bzw. der keilartigen Erhebungen und

Fig. 7

Lichtverteilungskurven zur Verdeutlichung der Wirkung der erfindungsgemäßen Lichtauskoppelstruktur.

The invention will be explained in more detail with reference to the accompanying drawings. Show it:

Fig. 1

an embodiment of the present invention in the form of a rescue sign lamp in a perspective view;

Fig. 2

the principle of light pipe and light extraction in the escape sign lamp according to the invention;

Fig. 3

an enlarged view of the effect of Lichtauskoppelstrukturen invention;

4 to 6

Views of the Lichtauskoppelstruktur invention or the wedge-like elevations and

Fig. 7

Light distribution curves to illustrate the effect of Lichtauskoppelstruktur invention.

As a preferred embodiment of the present invention is in Fig.1 a rescue sign provided with the reference numeral 1 illustrated. Such a rescue sign light 1 is usually used to display the direction of an escape route with the help of a lit icon 2 and thus allow people in an emergency, the reliable leaving a building. Usually, such a lamp 1 has a housing 3 with a flat design, wherein a corresponding icon 2 is arranged at least on one of the two flat sides. About arranged in the interior of the housing 3 means for light emission ensures that the icon 2 is backlit evenly in order to be able to be perceived reliably and as well as possible. A common procedure for this is to arrange a plate-shaped light guide 10 within the housing 3, as in Fig. 2 is shown. The light-guiding element 10 consists of a transparent material, usually of a transparent plastic (eg PMMA), wherein one or more light sources 50 are arranged on an end face 11 of the light-guiding element 10. In the present case, preferably LEDs 50 are used as light sources, which are arranged on a circuit board 51 which extends over the entire height of the light-conducting element 10. Accordingly, light is radiated into this over the entire end face 11 of the light-guiding element 10.

As an alternative to the arrangement of a plurality of LEDs 50, of course, the use of a single correspondingly elongated light source would also be conceivable. For example, a correspondingly configured organic LED (OLED) or a suitably adapted fluorescent lamp could be used, wherein the use of LEDs or OLEDs is preferred, since a space-saving solution can be realized here.

The coupled by the LEDs 50 via the end face 11 in the plate-shaped light guide 10 light is then forwarded along the light guide 10, which takes place in the usual way by reflections on the two flat sides 12 and 13 respectively. By this Lichtleiteffekt, which is primarily due to total reflections at the border crossings between the material of the light guide 10 and air or possibly on the use of reflective materials, therefore, a light pipe and ultimately a corresponding distribution of the light over the entire plane of the light guide 10th , which leads to a uniform light output. At certain areas of the flat sides 12, 13 of the light guide 10 special structures are then formed, which are designed so that here incident light rays are not totally reflected but instead deflected so that they can leave the light guide 10 10 via one of the two flat sides 12 ,. The use of such Lichtauskoppelstrukturen is basically already known and leads to a flat light output is achieved, which illuminates the even before one of the two flat sides 12, 13 of the light guide 10 Pictogram 2 as evenly as possible.

If light-outcoupling structures known from the prior art are used, the result is that the light emitted via the flat side or the flat sides 12, 13 of the light-conducting element 10 is emitted at least to a certain extent in the forward direction or in the direction of the light line. That is, the light output with respect to the light emitted from the light sources 50 arranged on the front side 11 has an asymmetry. However, since such an asymmetry is more undesirable in emergency exit luminaires, since the escape route should be recognizable as well as possible from different directions, symmetrical light output would be much more desirable. Of course, this could be achieved in an obvious way by arranging 10 light sources on two opposite end faces of the light-guiding element. However, since this would lead to an increased cost of materials and to a larger construction of the luminaire, according to the present invention, a special embodiment of the Lichtauskoppelstrukturen proposed over which a symmetrical light output is achieved despite an asymmetric light irradiation in the light guide 10.

The solution according to the invention consists of at least partially providing the flat surface opposite the light exit surface of the light-guiding element 10 with wedge-like elevations, as shown in FIGS Fig. 2 to 6 are shown and will be explained in more detail below. It should be noted that in the illustrated embodiment according to Fig. 2 a light output over both flat sides 12, 13th is provided, which is why the wedge-like elevations according to the invention are arranged on both flat sides 12 and 13. However, it would also be conceivable that only one of the two flat sides 12, 13 of the light-guiding element 10 should emit light. In this case, the wedge-shaped structures according to the invention are to be arranged exclusively on the corresponding opposite flat side 12 or 13. Furthermore, it can also be provided that complementary - eg alternating - to the wedge-like structures according to the invention, conventional light extraction structures are used in order to adapt the ultimately achieved light emission characteristic to specific requirements.

As already mentioned, the structures according to the invention constitute wedge-like elevations 15, as enlarged in FIGS 4 to 6 are shown. These wedge-like elevations are aligned parallel to one another and arranged one behind the other transversely to the direction of light-guiding the light-conducting element 10 (the light-guiding direction corresponds to the direction starting from the light-coupling surface 11 to the opposite end face of the light-guiding element 10). Each elevation 15 consists of a first, widening wedge region 16 and a subsequent circular segment-like area 17. Both areas 16 and 17 are dimensioned and designed such that they merge tangentially into each other, as the representation of Fig. 6 can be removed. The wedge-like elevations 15 formed in this way are separated from each other by planar surface regions 20, so that the in the 4 and 5 illustrated wave-like structure of the surface of the light guide 10 results.

The mode of operation of the structures 15 according to the invention can be seen in particular from the view of FIG Fig. 3 be removed. It can be seen that light rays coming from the direction of the light source 50 and incident on the boundary surface of the wedge region 16 which is slightly inclined with respect to the light guiding direction are reflected. Due to the inclination of this region 16, however, the light beams are not directed directly back into the light guide 10 but only reflected so that they impinge on the interface of the circular segment-like region 17. Again, a (total) reflection takes place, wherein this now takes place such that the reflected light beam has a backward component, that is aligned in the direction of the light source 50 out. The deflected in this way light beam then falls on the opposite flat side of the light guide 10, he can leave this (see Fig. 2 ).

The interaction of the wedge region 16 with the circular segment-like region 17 thus ensures that the inventively designed surveys incident light beams are not only deflected so that they can leave the light guide, but that they are also afflicted with a certain directional proportion in the direction back to the light coupling. Since this is true only for a part of the light rays, while other light rays leaving the light guide 10, for example, due to the complementary use of conventional Lichtauskoppelstrukturen still with a directional portion in the forward direction or from the light source 50 are afflicted, is ultimately seen in total achieved a balanced light output on both sides.

The mode of action of the outcoupling structures according to the invention is in Fig. 7 shown, which shows two light distribution curves for plate-shaped light-guiding elements, wherein in each case light according to the arrow, that is coupled from the right side into the light guide. On the left side, the light distribution curve of a conventional light-guiding element is shown, while the right-hand side shows a light distribution curve, as obtained with the aid of the structures according to the invention. It can be clearly seen that in a light guide according to the prior art, an extremely asymmetric light output is achieved, while on the other hand, the light output to both opposite sides in the structure according to the invention is significantly more uniform. The illustrated curves thus show very clearly that, with the aid of the structure designed according to the invention, the desired symmetrical light output can be achieved despite asymmetrical light coupling.

The structure of the surveys according to the invention will be described below with reference to FIGS. 5 and 6 will be described in more detail again. As already mentioned, each elevation consists of two sections or regions, the wedge region 16 extending in a linear manner with a length l ₁ and the adjoining circular segment-like region 17 with a length l ₂ . The dimensions of both regions 16 and 17 are preferably dimensioned such that the ratio of the length l _{1 of} the wedge region 16 to the length l _{2 of} the circular segment-like region 17 is in the range of 4.5 to 7.5. In particular, a ratio l ₁ / l ₂ = 6.0 has been found to be particularly advantageous.

Furthermore, it has been found to be advantageous if the center Z of the circular segment-like region 17 is not located in the plane of the light exit surface of the light guide, but instead is further offset inwards, as in Fig. 6 is shown. This has the consequence that the circular segment-like portion 17 does not meet at a right angle to the adjoining flat surface area 20. In this case, the radius r of the circular segment-like region 17 is preferably located compared to the length l _{1 of} the wedge region in the range of 0.15 to 0.21. Particularly advantageous is a ratio r / l ₁ = 0.18 has been found.

The juxtaposed, inventively designed elevations 15 are, as already mentioned, separated from one another by planar surface regions 20. Since the light density decreases due to the continuous partial decoupling of light in the light-conducting direction, it is provided that the length L of the planar surface regions 20 varies, in particular decreases in the light-conducting direction. This in turn means that the density of the projections 15 according to the invention increases with increasing distance from the light source 50, which compensates for the effect of decreasing luminance and ultimately leads to a uniform, homogeneous density of the light output over the entire surface of the light guide 10. It is thus not only achieved a symmetrical light output, but also ensures that the icon 2 of the lamp 1 across the entire width of the luminaire is brightened evenly. The ratio of the total length l _{g of} a survey 15 to length L of the surface regions 20 may be in the range between 0.5 and 1.1.

As already mentioned, it is not absolutely necessary for the elevations according to the invention to be arranged on both flat sides of the light-guiding element. Depending on whether a light output on both sides is desired or not, both or only one of the two sides can be provided with the structures.

Finally, it should be noted that the inventive design is of course not limited to escape sign lights. Also in the case of lights that are provided for room lighting, an insert of the solution according to the invention may be provided. Thus, for example, luminaires are known, which have a box-shaped housing, wherein an elongate light source is centrally located and a portion of the light is emitted directly to the bottom for direct illumination, whereas a further portion of the light via two arranged to the light source light guide surface is delivered. In this case as well, an asymmetrical coupling of light into the optical waveguides is present, in which case the structure according to the invention in turn advantageously leads to despite all, a symmetrical light output is obtained for each individual light guide element, which leads to an overall improvement in the appearance.

Claims (10)

1. A luminaire (1) with at least one light source (50) as well as a plate-shaped light-guiding element (10),
   wherein the light source (50) is arranged on a narrow side of the light-guiding element (10) forming a light entry surface (11) and the light-guiding element (10) is designed to emit light incoupled via the light entry surface (11) via a light exit surface arranged substantially perpendicular to the light entry surface (11) and wherein the light-guiding element (10) is profiled on the side opposite the light exit surface at least partially with wedge-like elevations (15) lying adjacent to one another transversely to the light-guiding direction,
   characterized in
   that each elevation (15) - viewed from the direction of the light entry surface (11) - has a linearly expanding wedge area (16) as well as a circular segment-like area (17) adjoining the wedge area (16) and the wedge-like elevations (15) are separated from one another by planar surface areas (20), wherein the length (L) of the planar surface areas (20) varies, in particular decreases viewed in the light-guiding direction.
2. A luminaire according to Claim 1,
   characterized in
   that - viewed in the light-guiding direction - the ratio of the length (l₁) of the wedge area (16) to the length (l₂) of the circular segment-like area (17) is in the range of 4.5 to 7.5, preferably approximately 6.0.
3. A luminaire according to Claim 1 or 2,
   characterized in
   that the radio of the radius (r) of the circular segment-like area (17) to the length (l₁) of the wedge area (16) is in the range of 0.15 to 0.21, preferably approximately 0.18.
4. A luminaire according to any one of the preceding claims,
   characterized in
   that the wedge area (16) passes tangentially into the circular segment-like area (17).
5. A luminaire according to any one of the preceding claims,
   characterized in
   that the center (Z) of the circular segment-like area (17) is offset relative to the surface of the light-guiding element (10).
6. A luminaire according to any one of the preceding claims,
   characterized in
   that the ratio of the length (l_g) of the elevations (15) to the length (L) of the planar surface areas (20) is in the range of 0.5 to 1.1.
7. A luminaire according to any one of the preceding claims,
   characterized in
   that the wedge-like elevations (15) are arranged on both flat sides (12, 13) of the light-guiding element (10).
8. A luminaire according to any one of the preceding claims,
   characterized in
   that said luminaire has a plurality of LEDs (50) as light sources.
9. A luminaire according to any one of the preceding claims,
   characterized in
   that it is an escape sign luminaire.
10. A use of a plate-shaped light-guiding element (10) in a luminaire according to Claim 1,
    wherein the light-guiding element (10), is designed to emit light incoupled via a frontal light entry surface (11) via a light exit surface arranged substantially perpendicular to the light entry surface (11) and wherein the light-guiding element (10) is profiled on the side opposite the light exit surface at least partially with wedge-like elevations (15) lying adjacent to one another transversely to the light-guiding direction,
    characterized in
    that each elevation (15) - viewed from the direction of the light entry surface (11) - has a linearly expanding wedge area (16) as well as a circular segment-like area (17) adjoining the wedge area (16) and the wedge-like elevations (15) are separated from one another by planar surface areas (20), wherein the length (L) of the planar surface areas (20) varies, in particular decreases viewed in the light-guiding direction.

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