A LIGHTING DEVICE PROVIDING AN IMPROVED VISIBILITY

Abstract

The present invention relates to a lighting arrangement (1) for outdoor illumination, the lighting arrangement comprising at least one first light source for emitting a first light and at least one second light source arranged at a distance from the first light source and arranged for emitting a second light. The lighting arrangement further comprises a modulating optical element (7) for converting the first light into a modulated first light providing a first illumination pattern on a first target surface (4), wherein the first illumination pattern comprises a sequence of alternating illuminance peaks. The modulating optical element (7) further converts the second light into a modulated second light providing a second illumination pattern on a second target surface (4), wherein the second illumination pattern comprises a sequence of alternating illuminance peaks. The first and the second target surfaces at least partially overlap, and the first illumination pattern is substantially complementary to the second illumination pattern.

Claims

1. A lighting arrangement for outdoor illumination, said lighting arrangement comprising: a first light source for emitting a first light, the first light source being arranged in a first lighting device; a second light source for emitting a second light, the second light source being arranged in a second lighting device; a first modulating optical element for converting said first light into a modulated first light providing a first illumination pattern on a first target surface, and a second modulating optical element for converting said second light into a modulated second light providing a second illumination pattern on a second target surface, wherein the second lighting device is arranged at a distance from the first lighting device, the distance being from 0.3 m to 10 m, wherein said first target surface and said second target surface at least partially overlap, wherein each of said first illumination pattern and said second illumination pattern comprises a sequence of alternating illuminance peaks; and wherein said first illumination pattern is substantially complementary to said second illumination pattern.

2. The lighting arrangement according to claim 1, wherein said lighting arrangement further comprises at least one supporting element for supporting said first and said second lighting devices.

3. The lighting arrangement according to claim 2, wherein said lighting arrangement comprises one supporting element having a vertical extension, and wherein said first and said second lighting devices are arranged at a distance from each other along said vertical extension of said supporting element.

4. The lighting arrangement according to claim 3, wherein said distance between said first and said second lighting device is from 0.5 m to 2 m.

5. The lighting arrangement according to claim 1, wherein said lighting arrangement comprises a first and a second supporting element arranged at a distance from each other, wherein said first lighting device is arranged on said first supporting element, and wherein said second lighting device is arranged on said second supporting element.

6. The lighting arrangement according to claim 5, wherein said distance between said first and said second supporting element is from 5 m to 10 m.

7. The lighting arrangement according to claim 1, wherein said lighting arrangement further comprises at least one beam-shaping optical element for shaping said first and/or said second light emitted by said first and/or said second light source into a beam of light.

8. The lighting arrangement according to claim 7, wherein said modulating optical element is arranged on said at least one beam-shaping optical element.

9. The lighting arrangement according to claim 1, wherein said lighting arrangement further comprises a cover plate being arranged to cover at least one of said first and said second light sources.

10. The lighting arrangement according to claim 9, wherein said modulating optical element is arranged on said cover plate.

11. The lighting arrangement according to claim 1, wherein said modulating optical element is a pattern corresponding to said first illumination pattern on said first target surface and/or said second illumination pattern on said second target surface.

12. The lighting arrangement according to claim 1, wherein said first and/or said second illumination pattern is a dynamic pattern.

13. The lighting arrangement according to claim 1, wherein said lighting arrangement comprises a control unit for individually controlling said first and said second light sources.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing example embodiments of the invention, wherein:

[0055] FIG. 1 illustrates a lighting arrangement of the present invention comprising a lighting device and a post;

[0056] FIGS. 2a-2d illustrate the improved visibility provided by the lighting arrangement according to the present invention;

[0057] FIGS. 3a-3c depict illumination patterns on a target surface provided by the lighting arrangement of the present invention;

[0058] FIGS. 4 and 5 illustrate the intensity distribution and illuminance distribution on a road wherein the modulating optical element is arranged on the beam-shaping optical element;

[0059] FIG. 6 is the illuminance distribution on a cylinder representing a pedestrian moving across the road depicted in FIGS. 4 and 5;

[0060] FIG. 7 shows a lighting device comprising a plurality of first light sources and a plurality of second light sources, a beam-shaping optical element in the form of a peanut lens optic with the modulating optical element in the form of an absorbing pattern on the cover plate;

[0061] FIGS. 8 and 9 depict the intensity and illuminance distribution on a target surface when the plurality of first light sources in FIG. 7 is on;

[0062] FIG. 10 depicts the illuminance distribution on a cylinder representing a pedestrian moving across the road depicted in FIGS. 8 and 9;

[0063] FIGS. 11 and 12 illustrate the intensity and illuminance distribution on a target surface when the plurality of second light sources in FIG. 7 is on;

[0064] FIG. 13 depicts the illuminance distribution on a cylinder representing a pedestrian moving across the road depicted in FIGS. 11 and 12;

[0065] FIG. 14 shows a lighting arrangement comprising two lighting devices providing complementary illumination patterns on the target surface.

[0066] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate embodiments of the present invention, wherein other parts may be omitted or merely suggested.

DETAILED DESCRIPTION

[0067] The present invention will now be described hereinafter with reference to the accompanying drawings, in which exemplifying embodiments of the present invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments of the present invention set forth herein; rather, these embodiments of the present invention are provided by way of example so that this disclosure will convey the scope of the invention to those skilled in the art. In the drawings, identical or similar reference numerals denote the same or similar components having a same or similar function, unless specifically stated otherwise.

[0068] FIG. 1 illustrates a lighting arrangement 1 comprising a lighting device 2 arranged on a post 3. The lighting device 2 is arranged for outdoor illumination of a target surface 4, in this case being a pedestrian crossing across which a pedestrian 5 is moving. The lighting device 2 comprises a first and a second light source for emitting a first and a second light.

[0069] The lighting device 2 comprises a light exit window 6 for releasing the light being emitted by the first and the second light sources. The lighting device 2 further comprises a modulating optical element 7 for converting the first light into a modulated first light providing a first illumination pattern on the first target surface 4, wherein the illumination pattern comprises a sequence of alternating illuminance peaks. It should be noted that in the embodiment depicted in FIG. 1, only one of the first and the second light sources is operating. The modulating optical element is arranged on the cover plate 8 covering the light exit window 6.

[0070] As mentioned above, the lighting arrangement of the present invention provides improved visibility of an object regardless the positive and negative contrast that may occur depending on the outer factors such as clothing of a pedestrian, illumination angle, weather conditions or the like.

[0071] FIGS. 2a and 2b illustrate the lighting arrangement 101 according to the prior art, wherein a pedestrian 105 wearing dark clothing is visible, while a pedestrian 205 wearing light clothing is substantially invisible. FIGS. 2c and 2d depict the lighting arrangement 201 according to the present invention, wherein both the pedestrians 105 and 205 are clearly visible.

[0072] FIGS. 3a-3c illustrate illumination patterns comprising a sequence of alternating illuminance peaks. It should be noted that the illuminations patterns in FIGS. 3a and 3b are complementary.

[0073] FIGS. 4 and 5 depict intensity and illuminance distribution provided by a lighting arrangement of the present invention. The lighting arrangement comprises a beam-shaping optical element in the form of a lens having a diameter of 30 mm, and a light source having area of 0.10.1 mm.sup.2. A very small source size (point source) was chosen to enable sharp modulation features in the illumination pattern. When larger sources are used, the features become less pronounced. The modulating optical element in the form of a checkboard pattern is arranged on the lens in the form of a slight variation in local lens curvature. As may be seen in FIGS. 4, and 5, the illumination pattern is clearly visible on a target surface. The dark shadow in the upper right corner in FIG. 5 is cast by a cylinder having a longitudinal extension of 180 cm and arranged such that the longitudinal extension of the cylinder is perpendicular to the target surface. The cylinder thus represents a pedestrian. FIG. 6 shows the illumination pattern on the unfolded cylinder, wherein the portion of the cylinder between 180 and 100 degrees and between 120 and 180 degrees is illuminated by the lighting device. The illumination pattern is clearly visible on the illuminated portion.

[0074] FIG. 7 depicts a lighting arrangement 302 comprising a plurality of first light sources 309 and a plurality of second light sources 309. The lighting arrangement 302 further comprises four beam-shaping optical elements 310, each beam-shaping optical element being assigned to a light source 309, 309.

[0075] The modulating optical element 307 in the form of an absorbing grid is arranged on the cover plate 308. It should be noted that the pattern of the modulating optical element is selected such that the plurality of first light sources 309 is aligned with an opening in the grid, and the plurality of second light sources is aligned with a cross in the grid. Therefore, the plurality of first light sources and the plurality of second light sources will provide two distinctly different illumination patterns. When the first and the second light sources are operated individually, the lighting arrangement may dynamically switch between the two patterns or be in a state where both patterns are on, thus providing a reduced contrast.

[0076] FIGS. 8 and 9 illustrate the intensity and illuminance distribution provided by a lighting device when the plurality of second light sources is operating. The dark shadow is cast by a cylinder having a longitudinal extension of 400 cm and arranged such that the longitudinal extension of the cylinder is perpendicular to the target surface. The cylinder thus represents a pedestrian. FIG. 10 shows the illumination pattern on the unfolded cylinder, wherein the portion of the cylinder between 0 and 100 degrees is illuminated by the lighting device. As may be seen in FIG. 10, the cylinder is rather evenly illuminated.

[0077] When the plurality of first light sources is operating instead, the intensity and illuminance distribution depicted in FIGS. 11 and 12 is obtained. As may be noted, the cylinder is now positioned in a dark area of the pattern. However, as may be seen in FIG. 13, the illumination pattern on the cylinder is clear even in this case.

[0078] FIG. 14 illustrates a lighting arrangement 401 comprising a first lighting device 402 arranged on a post 403 extending vertically from the ground. Further, the lighting arrangement 401 comprises a second lighting device 402 wherein the second lighting device 402 is arranged at a distance from the first lighting device 402. The first lighting device 402 comprises a first light source which provides a first illumination pattern on a first target surface 404. As may be seen in FIG. 14, the first and second lighting devices 402, 402 are arranged at different heights along the vertical extension of the post 403. The second lighting device 402 comprises a second light source which further provides a second illumination pattern on a second target surface 404. The first and the second target surfaces 404, 404 overlap thus forming a target surface 404. The first illumination pattern is complementary to the second illumination pattern. The complementary illumination patterns are chosen such that no pattern is visible on the target surface 404, but, because of the different positions of the light sources, the alignment breaks down at other heights and the pattern is visible on pedestrians. In other words, such an embodiment offers the advantage of providing a substantially invisible illumination pattern on the target surface 404, since overlapping complementary illumination patterns will provide an impression of an even illuminance. On the other hand, at a distance vertically from the target surface 404, i.e. in the space where a pedestrian is normally moving, the illumination pattern will still be perceivable, thus increasing visibility.

[0079] Although the present invention has been described with reference to various embodiments, those skilled in the art will recognize that changes may be made without departing from the scope of the invention. It is intended that the detailed description be regarded as illustrative and that the appended claims including all the equivalents are intended to define the scope of the invention. While the present invention has been illustrated in the appended drawings and the foregoing description, such illustration is to be considered illustrative or exemplifying and not restrictive; the present invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the appended claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.