A reflector device for modifying light distribution

Abstract

A reflector device comprises a first reflective surface (203) for surrounding a first light source and a second reflective surface (204) for surrounding a second light source First rims (205) of the first and second reflective surfaces define light egress apertures, second rims (206) of the first and second reflective surfaces are coincident with a first geometric plane (xy), and the first and second reflective surfaces are mirror symmetrical with respect to a second geometric plane (xz) perpendicular to the first geometric plane. First portions (207, 208) of the first and second reflective surfaces which are nearest to the second geometric plane (xz) are higher in a direction (z) perpendicular to the first geometric plane than second portions (209, 210) of the first and second reflective surfaces which are farthest from the second geometric plane (xz) to achieve a desired light distribution pattern.

Description

[0001] A reflector device for modifying light distribution

[0002] Field of the disclosure

[0003] The disclosure relates generally to illuminating engineering. More particularly, the disclosure relates to a reflector device for modifying a light distribution pattern of light sources that can be, for example but not necessarily, light emitting diodes “LED”. Furthermore, the disclosure relates to a lighting fixture comprising light sources and a reflector device.

[0004] Background

[0005] Distribution of light produced by a light source can be important or even critical in many applications. The light source can be, for example but not necessarily, a light emitting diode “LED”, a filament lamp, or a gas-discharge lamp. Figure 1 a shows a schematic illustration of a street lighting application where streetlamps 122 and 123 are arranged to illuminate a road 120. Figure 1 b shows a view of a section taken along the line A1 -A1 shown in figure 1 a, and figure 1 c shows a view of a section taken along the line A2-A2 shown in figure 1a. Each of the streetlamps 122 and 123 comprises one or more light sources such as e.g. light emitting diodes “LED”. Furthermore, each streetlamp may comprise optical devices configured to modify a light distribution pattern of the one or more light sources. An exemplifying optical device 131 according to the prior art is illustrated in figures 1 e and 1f where figure 1f shows a view of a section taken along the line A-A shown in figure 1 e. In figures 1 e and 1f, exemplifying light beams are depicted with dashed line arrows. The optical device 131 comprises transparent material 133, e.g. plastic, glass, or optical silicone, whose refractive index is greater than one. In this exemplifying case, the optical device 131 comprises a reflective surface 134 for reflecting a part of the light beams as illustrated in figures 1 e and 1f. The reflective surface 134 is a surface of a cavity 135. The shape of the cavity 135 and the refractive index of the transparent material 133 are selected so that total internal reflection “TIR” takes place on the reflective surface 134. Figure 1d shows polar plots illustrating simulated luminance distributions on the surface of the road 120 when optical devices of the kind described above are being used in an exemplifying situation where the distance D between the adjacent streetlamps is about 4.5 times the height H of streetlamp poles and the width W of a lane 121 is about a half of the height H of the streetlamp poles. The solid line polar plot shows the luminance distribution on the line A1 -A1 shown in figure 1 a and the dashed line polar plot shows the luminance distribution on the line A2-A2 that is on the middle of the lane 121 . Angles <pi and 2 are defined in figure 1 c and angles 3 and 4 are defined in figure 1 b. An ideal situation would be such that the luminance is at a suitable level and uniform on the surface of the road.

[0006] It becomes inherently more and more challenging to achieve a luminance distribution that is sufficiently uniform in the longitudinal direction of the road 120 when the distance D between adjacent streetlamps is increased. On the other hand, the costs of the street lighting can be reduced by increasing the distance D. Thus, there is a clear economic incentive to increase the distance D between adjacent streetlamps.

[0007] Summary

[0008] The following presents a simplified summary to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments.

[0009] In this document, the word “geometric” when used as a prefix means a geometric concept that is not necessarily a part of any physical object. The geometric concept can be for example a geometric point, a straight or curved geometric line, a geometric plane, a non-planar geometric surface, a geometric space, or any other geometric entity that is zero, one, two, or three dimensional.

[0010] In accordance with the invention, there is provided a new reflector device for modifying a light distribution pattern of light emitted by first and second light sources. A reflector device according to the invention comprises a first reflective surface for surrounding the first light source and a second reflective surface for surrounding the second light source, wherein:

[0011] - first rims of the first and second reflective surfaces define light egress apertures through which light leaves the reflector device,

[0012] - second rims of the first and second reflective surfaces are coincident with a first geometric plane e.g. a surface of a circuit board,

[0013] - the first and second reflective surfaces are mirror symmetrical to each other with respect to a second geometric plane perpendicular to the first geometric plane, and

[0014] - first portions of the first and second reflective surfaces which are nearest to the second geometric plane are higher in a first direction perpendicular to the first geometric plane than second portions of the first and second reflective surfaces which are farthest from the second geometric plane so that a first main beam of light emitted by the first light source is directed away from the second geometric plane and a second main beam of light emitted by the second light source is directed mirror symmetrically compared to the first main beam with respect to the second geometric plane.

[0015] The fact that the main beams of the light emitted by the first and second light sources are directed away from the second geometric plane and mirror symmetrically to each other with respect to the second geometric plane facilitates achieving for example a sufficiently uniform distribution of luminance in a longitudinal direction of a road when the above-described reflector device is used in a street lighting application so that the second geometric plane, i.e. the geometric plane of the mirror symmetry between the first and second reflective surfaces, is substantially perpendicular to the longitudinal direction of the road.

[0016] In accordance with the invention, there is also provided a new lighting fixture comprising light sources and a reflector device according to the invention. The light sources can be for example light emitting diodes “LED”. In accordance with the invention, there is also provided a new system comprising a road and at least one streetlamp comprising at least one lighting fixture according to the invention, wherein the reflector device of the least one lighting fixture is positioned with respect to the road so that the second geometric plane, i.e. the geometric plane of the mirror symmetry between the first and second reflective surfaces, is substantially perpendicular to the longitudinal direction of the road.

[0017] A reflector device according to an exemplifying and non-limiting embodiment comprises a body section being a single piece of solid material, e.g. plastic, and a light-reflective metal coating, e.g. silver or aluminum coating, on at least the above- mentioned first and second reflective surfaces. The body section can be manufactured for example by mold casting.

[0018] In accordance with the invention, there is also provided a new mold having a form suitable for manufacturing, by mold casting, a piece of solid material having a shape of a reflector device according to the invention.

[0019] Exemplifying and non-limiting embodiments are described in accompanied dependent claims.

[0020] Various exemplifying and non-limiting embodiments both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in connection with the accompanying drawings.

[0021] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.

[0022] Brief description of the figures

[0023] The exemplifying and non-limiting embodiments and their advantages are explained in greater details below with reference to the accompanying drawings, in which: figures 1a, 1 b, and 1 c show a schematic illustration of a street lighting application according to the prior art, figure 1 d shows polar plots illustrating simulated luminance distributions on the surface of a road shown in figures 1 a-1 c when optical devices according to the prior art are being used, figures 1 e and 1f illustrate an optical device according to the prior art, figures 2a, 2b, and 2c illustrate a reflector device according to an exemplifying and non-limiting embodiment, figures 3a and 3b illustrate a lighting fixture according to an exemplifying and nonlimiting embodiment, and figures 4a-4c illustrate a street lighting application according to an exemplifying and non-limiting embodiment.

[0024] Figures 1 a-1f have already been explained in the Background-section of this document.

[0025] Description of exemplifying embodiments

[0026] The specific examples provided in the description given below should not be construed as limiting the scope and / or the applicability of the appended claims. Lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated.

[0027] Figures 2a and 2b show isometric views of a reflector device 201 according to an exemplifying and non-limiting embodiment for modifying the light distribution pattern of light sources that can be, for example but not necessarily, light emitting diodes “LED”. The viewing directions related to figures 2a and 2b are illustrated with geometric x-, y- and z- coordinate axes shown in figures 2a and 2b. Figure 2c shows the reflector device 201 when seen along the negative direction of the geometric z- coordinate axis. The reflector device 201 comprises a first reflective surface 203 for surrounding a first light source 202a and a second reflective surface 204 for surrounding a second light source 202b. In this exemplifying case, the reflector device 201 comprises a first section 217 that comprises the above-mentioned first and second reflective surfaces 203 and 204, and a second section 218 that comprises reflective surfaces similar to the first and second reflective surfaces so that the first and second sections 217 and 218 are successively in the x-direction as shown in figures 2a-2c. It is also possible that a reflector device according to an exemplifying and non-limiting embodiment comprises only one section such as the section 217 shown in figures 2a-2c or three or more sections which are successively in the way illustrated in figures 2a-2c. Without limiting generality, the description below can be limited to the above-mentioned first and second reflective surfaces 203 and 204.

[0028] First rims 205 of the first and second reflective surfaces 203 and 204 define light egress apertures through which light leaves the reflector device 201 . Second rims 206 of the first and second reflective surfaces are coincident with a first geometric plane that is the geometric xy-plane in figures 2a-2c. In figure 2a, a part of the first geometric plane is illustrated with a dashed line 250. The first and second reflective surfaces 203 and 204 are mirror symmetrical to each other with respect to a second geometric plane that is perpendicular to the first geometric plane. In figures 2a-2c, the second geometric plane is the geometric xz-plane. In figure 2a, a part of the second geometric plane is illustrated with a dashed line 251.

[0029] First portions 207 and 208 of the first and second reflective surfaces 203 and 204 which are nearest to the second geometric plane, i.e. the geometric xz-plane, are higher in a first direction perpendicular to the first geometric plane, i.e. the geometric xy-plane, than second portions 209 and 210 of the first and second reflective surfaces which are farthest from the second geometric plane, i.e. the geometric xz- plane. In figures 2a-2c, the first direction is parallel with the geometric z-coordinate axis. In this exemplifying case, the first portions 207 and 208 are concave to provide a collimating effect. Correspondingly, the second portions 209 and 210 are concave to provide a collimating effect. In the exemplifying reflector device 201 , the height of the first portions 207 and 208 of the first and second reflective surfaces in the first direction, i.e. the z-direction, is at least two times the height of the second portions

[0030] 209 and 210 of the first and second reflective surfaces in the first direction.

[0031] The fact that the main beams of the light emitted by the first and second light sources 202a and 202b are directed away from the second geometric plane, i.e. the geometric xz- plane, and mirror symmetrically to each other with respect to the second geometric plane, i.e. the geometric xz-plane, facilitates achieving for example a sufficiently uniform distribution of luminance in a longitudinal direction of a road when the reflector device 201 is used in a street lighting application so that the second geometric plane, i.e. the geometric xz-plane, is substantially perpendicular to the longitudinal direction of the road.

[0032] In a reflector device according to an exemplifying and non-limiting embodiment, each of the first and second reflective surfaces 203 and 204 is asymmetrical in a second direction parallel with a geometric section line between the above- mentioned first and second geometric planes. In figures 2a-2c, the second direction is parallel with the geometric x-coordinate axis. The asymmetry in the x-direction means that there is no geometric plane which is perpendicular to the geometric x- coordinate axis, and which would divide a reflective surface under consideration into two parts that are mirror symmetric to each other with respect to the geometric plane. Furthermore, each of the first and second reflective surfaces 203 and 204 is asymmetrical in a third direction perpendicular to the second geometric plane. In figures 2a-2c, the third direction is parallel with the geometric y-coordinate axis. The asymmetry in the y-direction means that there is no geometric plane which is perpendicular to the geometric y-coordinate axis, and which would divide a reflective surface under consideration into two parts that are mirror symmetric to each other with respect to the geometric plane. The above-mentioned asymmetries cause that the first main beam of light emitted by the first light source 202a is directed obliquely away from the first and second geometric planes, i.e. the geometric xy- and xz- planes, and the second main beam of light emitted by the second light source 202b is directed mirror symmetrically compared to the first main beam with respect to the second geometric plane, i.e. the geometric xz-plane. In figure 2c, the directions of the main beams of the light emitted by the light sources are depicted with dashed line arrows. In a reflector device according to an exemplifying and non-limiting embodiment, third portions 211 and 212 of the first and second reflective surfaces which are between the first and second portions of the first and second reflective surfaces are, in the first direction i.e. the z-direction, lower than the first portions 207 and 208 and higher than the second portions 209 and 210.

[0033] In a reflector device according to an exemplifying and non-limiting embodiment, fourth portions 213 and 214 of the first and second reflective surfaces which are between the first and second portions and face towards the third portions 211 and 212 are higher in the first direction, i.e. the z-direction, than the third portions 211 and 212.

[0034] In a reflector device according to an exemplifying and non-limiting embodiment, the fourth portions 213 and 214 of the first and second reflective surfaces are provided with light-spreading grooves extending between the first and second rims 205 and 206 of the first and second reflective surfaces.

[0035] In a reflector device according to an exemplifying and non-limiting embodiment, each of the first and second reflective surfaces has overhangs 215 and 216 protruding towards each other in directions, i.e. in +x-directions and -x-directions, parallel with the geometric section line between the first and second geometric planes and configured to reflect light to directions away from the second geometric plane. Reflective surfaces of the overhangs direct light emitted sidewards from the light sources to desired directions.

[0036] Figures 3a and 3b illustrate a lighting fixture according to an exemplifying and nonlimiting embodiment. Figure 3b shows a view of a section taken along the line A-A shown in figure 3a. The section plane is parallel with the geometric yz-plane of a coordinate system 399. The lighting fixture comprises four light sources 302a, 302b, 302c, and 302d and a reflector device 301 . The reflector device 301 is according to an exemplifying and non-limiting embodiment of the invention. The reflector device 301 can be for example such as the reflector device 201 illustrated in figures 2a-2c. Each of the light sources may comprise at least one light emitting diode “LED”. In the exemplifying case illustrated in figures 3a and 3b, the lighting fixture further comprises a circuit board 319. The light sources are mounted on a surface of the circuit board 319, and rims of the reflective surfaces corresponding to the rims 206 in figures 2a and 2b are against the surface the circuit board. In figures 3a and 3b, the directions of the main beams of the light emitted by the light sources are depicted with dashed line arrows.

[0037] Figure 4a shows a schematic illustration of a street lighting application where streetlamps 422 and 423 are arranged to illuminate a road 420. Figure 4b shows a view of a section taken along the line A1 -A1 shown in figure 4a, and figure 4c shows a view of a section taken along the line A2-A2 shown in figure 4a. Each of the streetlamps 422 and 423 comprises one or more lighting fixtures each of which comprises light sources, e.g. light emitting diodes “LED”, and one or more reflector devices for modifying the light distribution pattern of the light sources. Each reflector device can be for example according to what is illustrated in figures 2a-2c. Each reflector device is positioned with respect to the road 420 so that the second geometric plane related to the reflector device, i.e. the geometric xz-plane in figures 2a-2c, is substantially perpendicular to the longitudinal direction of the road and the first direction related to the reflector device, i.e. the z-direction in figures 2a-2c, is vertically downwards, or obliquely downwards to illuminate the whole width of the road 420.

[0038] The specific examples provided in the description given above should not be construed as limiting the scope and / or the applicability of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.

Claims

What is claimed is:

1. A reflector device (201 ) for modifying a light distribution pattern of first and second light sources, the reflector device comprising:- a first reflective surface (203) for surrounding the first light source, and- a second reflective surface (204) for surrounding the second light source, wherein first rims (205) of the first and second reflective surfaces define light egress apertures, second rims (206) of the first and second reflective surfaces are coincident with a first geometric plane (xy), and the first and second reflective surfaces are mirror symmetrical to each other with respect to a second geometric plane (xz) perpendicular to the first geometric plane, characterized in that first portions (207, 208) of the first and second reflective surfaces which are nearest to the second geometric plane (xz) are higher in a first direction (z) perpendicular to the first geometric plane than second portions (209, 210) of the first and second reflective surfaces which are farthest from the second geometric plane (xz) so that a first main beam of light emitted by the first light source is directed away from the second geometric plane and a second main beam of light emitted by the second light source is directed mirror symmetrically compared to the first main beam with respect to the second geometric plane.

2. A reflector device according to claim 1 , wherein each of the first and second reflective surfaces is asymmetrical in a second direction (x) parallel with a geometric section line between the first and second geometric planes and each of the first and second reflective surfaces is asymmetrical in a third direction (y) perpendicular to the second geometric plane so that the first main beam is directed obliquely away from the first and second geometric planes and the second main beam is directed mirror symmetrically compared to the first main beam with respect to the second geometric plane.

3. A reflector device according to claim 1 or 2, wherein a height of the first portions (207, 208) of the first and second reflective surfaces in the first direction (z)is at least two times a height of the second portions (209, 210) of the first and second reflective surfaces in the first direction (z).

4. A reflector device according to any one of claims 1 -3, wherein the first portions (207, 208) of the first and second reflective surfaces are concave to provide a collimating effect.

5. A reflector device according to any one of claims 1 -4, wherein the second portions (209, 210) of the first and second reflective surfaces are concave to provide a collimating effect.

6. A reflector device according to any one of claims 1 -5, wherein third portions (211 , 212) of the first and second reflective surfaces which are between the first and second portions of the first and second reflective surfaces are, in the first direction (z), lower than the first portions (207, 208) and higher than the second portions (209, 210).

7. A reflector device according to claim 6, wherein fourth portions (213, 214) of the first and second reflective surfaces which are between the first and second portions and face towards the third portions are higher in the first direction (z) than the third portions.

8. A reflector device according to claim 7, wherein the fourth portions (213, 214) of the first and second reflective surfaces are provided with light-spreading grooves extending between the first and second rims (205, 206) of the first and second reflective surfaces.

9. A reflector device according to any one of claims 1 -8, wherein each of the first and second reflective surfaces has overhangs (215, 216) protruding towards each other in directions (+x, -x) parallel with a geometric section line between the first and second geometric planes and configured to reflect light to directions away from the second geometric plane.

10. A reflector device according to any one of claims 1 -9, wherein the reflector device comprises a body section being a single piece of solid material and a light- reflective metal coating on at least the first and second reflective surfaces.

11. A reflector device according to any one of claims 1-10, wherein the reflector device comprises a first section (217) comprising the first and second reflective surfaces (203, 204) and one or more second sections (218) each comprising reflective surfaces like the first and second reflective surfaces so that the reflective surfaces of each of the one or more second sections are mirror symmetrical to each other with respect to the second geometric plane (xz) and the first and one or more second sections are successively in a / the second direction (x) parallel with a geometric section line between the first and second geometric planes.

12. A lighting fixture comprising light sources (302a-302d) and a reflector device (301 ) according to any one of claims 1-11.

13. A lighting fixture according to claim 12, wherein the lighting fixture comprises a circuit board (319), the second rims of the first and second reflective surfaces are against a surface of the circuit board, and the light sources are mounted on the surface of the circuit board.

14. A mold having a form suitable for manufacturing, by mold casting, a piece of solid material having a shape of a reflector device according to any one of claims 1- 11.

15. A system comprising a road (420) and a streetlamp (422, 423) comprising at least one lighting fixture according to claim 12 or 13, wherein a reflector device of the at least one lighting fixture is positioned with respect to the road so that the second geometric plane is substantially perpendicular to a longitudinal direction of the road.

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