High visual comfort road and urban LED lighting

Abstract

The invention provides a lighting system having a light source, a first reflective element, a second reflective element, and a lens, wherein the first reflective element tapers from a first end to a second end, the first reflective element includes a first reflective surface bridging the distance between the first end and the second end, wherein the first reflective surface is diffuse reflective, and wherein the light source is at least partially circumferentially surrounded by the first reflective surface, the light source is configured closer to the second end than to the first end to direct at least part of the light source light in the direction of the first end, the lens is configured to beam shape at least part of the light source light emanating from the reflective element and the light source, and the second reflective element is configured to redirect part of the light source light to the lens, wherein the second reflective element is configured to specularly reflect at least part of the light source light that reaches the second reflective element.

Claims

1. A lighting system comprising a light source, configured to provide light source light, a first reflective element, a lens at a varying distance (d2) from the first reflective element, and a second reflective element in between the first reflective element and the lens, wherein: the first reflective element tapers from a first end to a second end, wherein the first reflective element comprises a first reflective surface bridging the distance between the first end and the second end, wherein the first reflective surface is diffuse reflective, and wherein the light source is at least partially circumferentially surrounded by the first reflective surface; the light source is configured closer to the second end than to the first end, and wherein the light source is configured to direct at least part of the light source light in the direction of the first end; the lens is configured to beam shape at least part of the light source light emanating from the reflective element and the light source; and the second reflective element is configured to redirect part of the light source light to the lens, wherein the second reflective element is configured to specularly reflect at least part of the light source light that reaches the second reflective element, and wherein the second reflective element has different heights (h2) over its length so that over its full length at each location the second reflective element bridges the distance (d2) between the first reflective element and the lens.

2. The lighting system according to claim 1, wherein the lens comprises a Fresnel lens, and wherein the light source comprises a chip-on-board light source.

3. The lighting system according to claim 1, wherein the first reflective element has an opening angle (), defined by the reflective surface, of at least 120 and of at maximum 170.

4. The lighting system according to claim 1, wherein the first reflective element is rotationally symmetric.

5. The lighting system according to claim 1, wherein the first reflective element is non-rotationally symmetric, and wherein at least part of the first reflective element is a 3D printed part.

6. The lighting system according to claim 1, wherein the second reflective element is configured to specularly reflect at least 50% of the light source light that reaches the second reflective element.

7. The lighting system according to claim 6, wherein the first reflective element comprises a reflector wall comprising the first reflective surface, wherein the reflector wall comprises a slot for hosting a second reflective element.

8. The lighting system according to claim 7, wherein the first reflective element is rotationally symmetric, and wherein the slot defines part of a circle segment, wherein the circle segment has a secant, which may optionally be curved, and wherein the slot defines at least part of the secant.

9. The lighting system according to claim 1, wherein the first reflective element is a truncated cone or pyramid having a base with a perimeter, and wherein the second reflective element connects one point on the perimeter with another point on the same perimeter, said one point and said another point are lying apart on the perimeter by an angle , with in an angle range 60<=<=170.

10. The lighting system according to claim 1, wherein not any tangent to a reflective surface, which faces towards the light source, of the second reflective element extends through an optical axis (O).

11. A lamp comprising the lighting system according to claim 1, wherein the lamp is configured to provide a beam of lamp light with a non-rotationally symmetric shape.

12. A kit of parts comprising (i) the lighting system according to claim 1, wherein the first reflective element comprises a reflector wall comprising the first reflective surface, wherein the reflector wall comprises a slot for hosting a second reflective element, and wherein the kit of parts further comprises (ii) the second reflective element, wherein the second reflective element when configured in the slot is configured to specularly reflect at least 50% of the light source light that reaches the second reflective element during operation of the lighting system.

13. The kit of parts according to claim 10, wherein the reflector wall comprises a plurality of slots, and wherein the kit of parts comprises a plurality of different second reflective elements, wherein the second reflective elements are flexible.

14. A method of providing the lighting system according to claim 1, wherein the method comprises (i) providing the light source, the first reflective element and the lens, and (ii) assembling these into the lighting system, wherein the method comprises providing a reflector wall comprising the first reflective surface, wherein the reflector wall comprises a slot, wherein the method further comprises providing a second reflective element and configuring the second reflective element in the slot, wherein the second reflective element when configured in the slot is configured to specularly reflect at least 50% of the light source light that reaches the second reflective element during operation of the lighting system.

15. A method of providing light, the method comprising providing lighting system light with the lighting system according to claim 1, wherein relative to an optical axis (O) of the lighting system at least 60% of the lighting system light is provided within an angular range of 40-90 relative to the optical axis (O).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

(2) FIGS. 1a-1e schematically depict some aspects of the lighting system and lamp, as well as the kit of parts;

(3) FIGS. 2a-2c (schematically) depict yet some further aspects of the lighting system and lamp;

(4) FIG. 3a shows the intensity (in cd) as function of theta and phi in the xy-plane with an optimized reflector (3a). FIG. 3b shows the luminance (cd.m.sup.2) of the exit window, with on the x-axis the distance from the center of the window and on the y-axis the intensity (luminance) in cd/m.sup.2, with viewing direction perpendicular to the module with the lens; and

(5) FIGS. 4a-4b schematically show two embodiments of the segmentation of the first reflective element by the second reflective element.

(6) The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) FIG. 1a schematically depicts an embodiment of the lighting system 1000 comprising a light source 10, configured to provide light source light 11, a first reflective element 210, and a lens 240,

(8) The first reflective element 210 tapers from a first end 211 to a second end 212. Here, the firs reflective element has a conical shape. The first reflective element 210 comprises a first reflective surface 213 bridging the distance between the first end 211 and the second end 212, wherein the first reflective surface 213 is diffuse reflective, such as a diffuse white reflector. The light source 10 is at least partially circumferentially surrounded by the first reflective surface 213. Here, the light emitting surface of the light source essentially closes the second end 212 of the first reflective element.

(9) The light source 10 is configured closer to the second end 212 than to the first end 211. As can be seen, the light source 10 is configured to direct at least part of the light source light 11 in the direction of the first end 211. Hence, some light of the light source may escape from via the first end 201 without any reflection.

(10) The lens 240 is configured to beam shape at least part of the light source light 11 emanating from the reflective element 210 and the light source 10. Especially, the lens may comprise a plurality of refractive elements, especially configured to couple light at large angles relative to the optical axis into the lens, for outcoupling at the other side (downstream side) of the lens. The lens may be a Fresnel lens, as very schematically depicted in FIG. 1b.

(11) The opening at the first end may comprise a window 300, which is here the lens 240. The window has a light source side 302 and an opposite side, facing the external, indicated with reference 301. Likewise, the lens has a light source side 242 and an opposite side, facing the external, indicated with reference 241. Note that the Fresnel elements may especially be (only) configured at the upstream side or the light source side.

(12) The terms upstream and downstream relate to an arrangement of items or features relative to the propagation of the light from a light generating means (here especially the light source), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is upstream, and a third position within the beam of light further away from the light generating means is downstream.

(13) The first reflective element 210 has an opening angle , defined by the reflective surface 213, of at least 120 and of at maximum 170.

(14) Reference 310 indicates the cavity that is essentially formed by the lens 240, the first reflective surface 213, the optional second reflective element 220 (see below) and the light source 210 (and optionally a support comprising the light source 210; not depicted here).

(15) Further, as can be seen the first reflective element 210 is rotationally symmetric.

(16) FIG. 1a also schematically depicts a lamp 100.

(17) Optionally, the lighting system 1000 may further comprise a second reflective element 220 configured to redirect part of the light source light 11 to the lens 240. The second reflective element 220 may especially be configured to specularly reflect at least 50% of the light source light 11 that reaches the second reflective element 220.

(18) Hence, in embodiments, some basic features of the invention are an optical cavity in which a single Chips on Board (CoB) type LED is placed. The optical cavity in embodiments consists of a conical reflector part (white, diffuse) and a Fresnel lens. The modules can be characterized by the cut-off ( (see FIG. 1a)), height (h) and diameter (w). The Fresnel lens has features only on the side directed to the light source. At least one free-form specular or semi-specular reflector can be placed in the cavity (insert). An example of a Fresnel lens is schematically indicated in FIG. 1b. Especially, the upstream side includes the Fresnel lens (elements), and the downstream side may essentially be flat. The upstream side is especially directed to the light source 10.

(19) As shown in FIG. 1c, the lighting system 1000 the first reflective element 210 may comprise a reflector wall 214 comprising the first reflective surface 213. This reflector wall 214 may comprises a slot 215 for hosting a second reflective element 220.

(20) As indicated above, the first reflective element 210 may be rotationally symmetric. However, the slot 215 may define part of a circle segment 216, wherein the circle segment 216 has a secant 216a, which may optionally be curved, but which may also be straight, or which may have a curved part and a straight part, or two or more of such parts, and wherein the slot 215 defines at least part of the secant 216a. Hence, the second reflective element 220 may be configured in substantially any desired shape.

(21) This is also schematically depicted in FIG. 1d.

(22) FIG. 1d also schematically shows a kit of parts 2000 comprising the lighting system 1000. Here, the first reflective element 210 comprises a reflector wall 214 comprising the first reflective surface 213, wherein the reflector wall 214 comprises a slot 215 for hosting a second reflective element 220. The kit of parts 2000 further comprises the second reflective element 220, wherein the second reflective element 220 when configured in the slot 215 would configured to specularly reflect, e.g. at least 50% of the, light source light 11 that reaches the second reflective element 220 during operation of the lighting system 1000 (see FIGS. 1a and 1c). The reflector wall may also comprise a plurality of such slots, optionally having different shapes. Further, the kit of parts may comprise a plurality of (different) second reflective elements 220 (see by way of example the further second reflective elements 220 at the right). The differences may be in length, height, and optionally reflectivity.

(23) The second reflective element (including optionally a plurality of such elements) may essentially be a free-form reflector (i.e. free in the XY-plane (perpendicular to the optical axis of the device)). Further, especially it divides the circle (or virtual circle) of the first reflective surface in two (or more) parts. The second reflective element 220 especially connects one point on the (virtual) circle with another point on the same (virtual) circle.

(24) Here, the term virtual circle may also be used. For instance, when referring to FIG. 1d it may not be necessary to provide the entire circle of the first reflective element 210, or more precisely the first reflective surface 213. For instance, with 3D printing or other techniques, only the necessary elements may be provided, such as only the hatched area in FIG. 1d. The (virtual) circle is indicated with reference C.

(25) FIG. 1e schematically depicts an embodiment of the lighting system in perspective. The concentric rings indicate schematically the Fresnel lens embodiment. Here, a module is shown comprising the first reflective element and the second reflective element, the light source and the lens. The variable distance d2 between the first reflective element 210 and the lens 240 is indicated as well as the second reflective element 220 having a variable height h2 to bridge said variable distance d2 so that over its full length at each location the second reflective element 220 extends from the first reflective element 210 onto the lens 240. Thus, more blocking of light in undesired directions and direct to other directions by the reflective elements 210, 220 is attained.

(26) FIG. 2a schematically depicts a lamp 100 comprising the lighting system 1000, wherein the lamp 100 is configured to provide a beam 101 of lamp light. Reference 2 indicates a plane, such as a road. The beam 101 may have a non-rotationally symmetric shape, as very schematically depicted in FIG. 2c, with on the y-axis the relative flux (RF) and on the x-axis the cone angle (CA) in (2* is the opening angle). For instance, the bar at 10 indicates the intensity between 0-10. Likewise, the bar at 90 indicates the intensity between 80-90. The intensity distribution over the window of the lighting system, however, appeared to be relatively uniform. FIG. 2c schematically depicts thus a possible light pattern on the road and shows the illuminance (lm/m2).

(27) Road lighting requires an intensity profile which ensures a uniform illumination of the road at the highest possible pole-pole distance and a limited glare. The white conical reflector creates a cut-off (typically 70-80 w.r.t. to the optical axis (z-direction)). The Fresnel lens directs the light from the CoB source to the high angles (w.r.t. the optical axis). The inserted (semi-)specular reflector(s) direct and collimate the light from the source to the required off-axis angles in the x-y plane. A significant amount of light (typically 30-40%) of the flux is scattered at the conical shaped, white reflector surface. The background of the CoB source is illuminated (although much less bright than the CoB itself). The fact that the whole optical surface emits light improves the visual comfort of the lighting system dramatically (compared to a lens array).

(28) The Fresnel lens can be injection molded using a transparent polymer (PMMA, PC). The semi-specular or specular (mirror) sheets can be MIRO or MIRO-SILVER from Alanod corporation (thickness 0.2-0.8 mm). The thin sheets can easily be curved and inserted in the white reflector. The white reflector can have a matte or high-gloss surface finish. The white reflector can be 3D printed (e.g. from white polycarbonate) or injection molded. Additive manufacturing or 3D printing techniques (e.g. Fused Deposition Modelling; FDM) allows the fabrication of a white reflector with multiple customized slots in which flexible reflectors can be inserted. The inserted specular reflector can also be a 3D printed part which is coated with a thin aluminum layer (evaporation, sputter deposition). Having a single type of Fresnel lens, a variety of beams can be created by printing the white reflector with the appropriate slots, followed by insertion of a mirror sheet. The mirrors can be laser cut from a sheet of MIRO-SILVER and placed into these slots.

(29) A prototype was built, with a matte, white conical reflector, two curved mirrors and a Fresnel lens. A CoB capable to generate 12.2 klm from a circular surface with a diameter of 22 mm (CRI 80, 4000 K) was used. The white reflector has the following parameters: h=40 mm, w=200 mm and =70 deg. (see FIG. 1a). The Fresnel lens is designed in such a way that all light directly from the source is directed to an angle of 70 deg. w.r.t. the optical axis.

(30) The facet structure of the Fresnel lens may also change depending on the position on the circumference of the Fresnel lens. The white reflector and Fresnel lens could also have an elliptical shape.

(31) FIG. 3a provides the intensity profile (in candela) of an optimized system. Reference HI indicates a high intensity region; FIG. 3a schematically depicts a relative even (but non-symmetric) distribution of the intensity with the beam of light generated by the lighting system. FIG. 3b shows the luminance of the luminaire (the CoB generates 10 klm in this example). The image illustrates that the luminance is on every location in the optical cavity >20 kcd/m.sup.2. The viewing direction is perpendicular to the module (i.e. parallel to the optical axis).

(32) FIGS. 4a-4b schematically show two embodiments of the lighting system with segmentation of the first reflective element 210 by the second reflective element 220. In FIG. 4a the second reflective element 220 consists of a first and a second separate part which are mutually convex towards each other when viewed and projected along the optical axis O on the XY-plane. In FIG. 4b the second reflective element 220 is in one part only.

(33) As shown in both FIG. 4a and FIG. 4b, the second reflective element 220 has the feature that not any tangent 960 to a reflective surface (which faces towards the light source located at the optical axis O) of the second reflective element 220 extends through the optical axis O. Furthermore, it is shown that the second reflective element 220 divides the first reflective surface 213 in two respectively three segments and that both end portions of each separate part of the second reflective element 220 divides a perimeter 910 of the first reflective element 210, a circle in FIG. 4a and a rectangle in FIG. 4b, into perimeter portions. The second reflective element especially connects one point 920 on the perimeter 910 with another point 930 on the same perimeter 910, said one point 920 and said another point 930 are lying apart on the perimeter 910, with lines 940, 950 from the optical axis O respectively to said one point 920 and to said another point 930 mutually at an angle , with in an angle range 60<=<=170.

(34) The term substantially herein, such as in substantially all light or in substantially consists, will be understood by the person skilled in the art. The term substantially may also include embodiments with entirely, completely, all, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term substantially may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term comprise includes also embodiments wherein the term comprises means consists of. The term and/or especially relates to one or more of the items mentioned before and after and/or. For instance, a phrase item 1 and/or item 2 and similar phrases may relate to one or more of item 1 and item 2. The term comprising may in an embodiment refer to consisting of but may in another embodiment also refer to containing at least the defined species and optionally one or more other species.

(35) Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

(36) The devices herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

(37) It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb to comprise and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words comprise, comprising, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of including, but not limited to. The article a or an preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. 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.

(38) The invention further applies to a device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

(39) The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.