WO2019162209A1

WO2019162209A1 - A stadium lighting system and luminaire

Info

Publication number: WO2019162209A1
Application number: PCT/EP2019/053851
Authority: WO
Inventors: Yves Sebastien BOULIN; Stephan Certain; Giorgia Tordini
Original assignee: Signify Holding B.V.
Priority date: 2018-02-20
Filing date: 2019-02-15
Publication date: 2019-08-29

Abstract

A lighting element comprises a reflector dome at the base of which is provided a set of three lighting units, angularly spaced around an optical axis of the lighting element and each having a light output axis directed outwardly perpendicular to the optical axis towards the inner surface of the reflector dome. For a given reflector area the total light emitting area of the solid state light source arrangement is increased by a factor of 3 compared to a conventional lighting element.

Description

A STADIUM LIGHTING SYSTEM AND LUMINAIRE

FIELD OF THE INVENTION

This invention relates to a stadium lighting system and a luminaire, in particular for providing a high power narrow beam. BACKGROUND OF THE INVENTION

Stadium lighting requires efficient high flux luminaires, for example up to 200klm, with a controlled light beam, in particular with a very narrow beam (FWHM=lO°). It is also required to implement the lighting elements with a compact form factor. Due to application constraints and the need to replace existing high intensity discharge lamps, the maximum surface area of the luminaire is often limited to 600 mm x 600 mm.

Existing solid state lighting devices (in particular LED lighting) for stadium lighting are not able fulfil the requirements for high intensity, narrow beam and small size. Typically, a lighting unit comprises an LED arrangement of a single LED or an LED group and reflector optics provided over the LED arrangement. The LED arrangement is for example a chip on board LED arrangement, with its optical output axis collinear with the general optical axis of the lighting unit. Typically, the LED arrangement is provided at the base of a parabolic collimating reflector, and facing the open end of the reflector, hence towards the light output direction.

In order to increase the lumen density in such collimator reflectors, there may be multiple LED arrangements, each with their own collimating reflector, and the reflectors together forming a single component.

Figure 1 shows schematically an example of a lighting unit with three LED arrangements 12 each facing forwardly at the base of a parabolic reflecting collimator 14 which together define a single optical component.

The size of the optical component is directly linked to the size of the LED arrangement and the light beam required. By way of example, the LED arrangement 12 may typically have a light emitting surface of 4 mm² and the outer diameter of the collimator reflector 14 associated with each LED may be 29 mm. It is clear therefore that the size of the current optics is the limiting factor for the flux output which can be achieved from a given surface area. In particular, the optics limit how many LED arrangements may be formed into an array within the available surface area.

Using known designs and with existing LED technology, it is not possible to generate more light without impacting the efficiency of the system or the size and volume.

There is therefore a need for a lighting unit which can deliver increased light output from a given available surface area, and without suffering a decrease in efficiency.

SUMMARY OF THE INVENTION

The invention is defined by the claims.

According to examples in accordance with an aspect of the invention, there is provided a stadium lighting system a plurality of luminaires, wherein each luminaire comprises a plurality of lighting elements, each lighting element, comprising:

a solid state light source arrangement; and

a reflector dome, having a bottom and a circular open top with an optical axis directed between the bottom and the center of the circular open top, wherein the light source arrangement is located at the bottom,

wherein the reflector dome comprises an outer wall with a reflective inner surface and wherein the solid state light source arrangement comprises three lighting units angularly spaced equally around the optical axis and each having a central light output axis directed outwardly perpendicular to the optical axis towards the inner surface of the outer wall,

wherein the reflector dome comprises a portion of an elliptical reflector with a proximal focal point within the reflector dome and a distal focal point outside the reflector dome and

wherein each lighting unit comprises a plurality of LEDs located offset from the proximal focal point.

This arrangement makes use of three lighting units for each reflector, by arranging them to direct light radially outwardly. Each lighting unit makes use of one third of the reflector inner surface. In this way, for a given reflector area (e.g. the area of the circular open top) the total light emitting area of the solid state light source arrangement is increased by a factor of 3 compared to a conventional lighting element.

The use of three lighting units enables substantially the full light output from each lighting element to by collimated by the reflector. In particular, for each lighting unit preferably at least 95% of the output is within a cone of cone angle 120 degrees. This means that the light output from each lighting unit is limited to the one third portion of the reflector associated with the lighting unit.

There are multiple LEDs within each lighting unit so that the output flux may be increased. However, this means they cannot all be located at the proximal focal point so that beam broadening will result. Indeed, the LEDs are offset from the proximal focal point. The use of an elliptical reflector increases the convergence, for example compared to a parabolic reflector (since light passing through the proximal focal point is focused to the distal focal point). In this way, there is compensation for the broad beam which is caused by the LED array of each lighting unit by the use of an elliptical reflector.

The elliptical reflector portions are preferably all part of the same elliptical surface so that the design is simplified and there is continuity between the reflector portions, compared to separate reflector designs which are then mated together.

The aim of the overall design is to provide narrow beam illumination to a surface at the distal focal point of the elliptical reflector. The lighting units are provided in the vicinity of (although offset from) the proximal focal point of the elliptical reflector. They may for example direct light along an axis which extends generally from that proximal focal point (which lies on the main central optical axis). Thus, the lighting units are positioned on a radial path between the proximal focal point and the inner surface of the reflector.

The reflective inner surface preferably comprises a specular reflector. This provides the narrowest output beam, for example with a full width at half maximum

(FWHM) of less than 10 degrees.

The lighting element may further comprise a set of dividers which divide the volume of the reflector dome into three dome sectors, wherein one lighting unit is in each dome sector. These dividers prevent any interference between the light outputs of the lighting units, for stray light which is emitted outside a 120 degree cone.

The dividers are for example made of reflective parts on both sides. The function of the dividers is to block stray light, but they are preferably reflective to increase light recycling into each dome sector and thus increase the light output and efficiency.

Note that the dividers are optional, and depending on the desired relationship between stray light control and system efficiency, they may not be needed.

Each dome sector extends over 120 degrees. Thus, the interior volume of the reflector is divided into three identical sections giving a rotationally symmetrical light output.

Each lighting unit for example comprises an LED chip on board arrangement. Preferably the LEDs are formed as a close packed array in order to provide a light source which is as close as possible to a point source. The area may for example be in the range 2 mm² to 10 mm².

The distance between the focal points of the elliptical reflector (of which the reflector dome is only one portion) is for example in the range 10 m to 50 m, preferably in the range 20 m to 30 m. This range corresponds to the distance at which illumination is to be provided, for example on a sports playing field beneath the lighting element.

The lighting element may further comprise secondary optics over the circular open top. This may be used to provide a partially diffuse light output if desired, or to provide other beam shaping or beam directing functions.

The invention also provides a luminaire comprising a plurality of lighting elements each as defined above, for example 14 lighting elements. An array of 14 such elements is able to fit into a form factor compatible with a conventional luminaire retrofit. By way of example, one example of a conventional luminaire has mechanical dimensions of 6l6mm x 6l6mm x l30mm.

The 14 lighting elements are for example arranged as a row of three, two rows of four and a final row of three.

The light output flux of the luminaire is for example greater than 50 klm especially suitable for a stadium lighting application. However, the design is scalable to any size and light output flux.

The invention also provides a luminaire suitable for a stadium lighting system, said luminaire comprising a plurality of lighting elements, preferably at least 14, each as defined above, said lighting elements being arranged in a, preferably densest, hexagonal packing. Such an arrangement renders the luminaire to have favourable, samll dimensions. For an improved light distribution with abberations being at least partly averaged out, the luminaire may have the feature that essentially a first half of the lighting elements is arranged in a 60 degrees rotation about a respective optical axis with respect to a second half of the lighting elements. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described in detail with reference to the accompanying schematic drawings, in which:

Fig. 1 shows schematically an example of a lighting unit with three LED arrangements each facing forwardly at the base of a parabolic reflecting collimator; Fig. 2 shows a lighting element with the components shown in transparent form;

Fig. 3 shows the lighting element of Figure 2 with the components shown in solid form;

Fig. 4 shows the lighting element of Figure 2 in plan view;

Fig. 5 shows the planar reflector bottom and the attached lighting units;

Fig. 6 shows one lighting unit in more detail as a chip on board LED arrangement;

Fig. 7 shows one example of possible elliptical cross sectional shape for the reflector;

Fig. 8 shows an example of the narrow beam intensity distribution for the lighting element;

Fig. 9 shows one possible arrangement of lighting elements to form a luminaire;

Fig. 10 shows an electrical circuit to manage the LED chip on boards used in the luminaire of Figure 9, and

Fig. 11 shows a stadium provided with a stadium lighting system.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described with reference to the Figures.

It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

The invention provides a lighting element comprising a reflector dome at the base of which is provided a set of three lighting units, angularly spaced around an optical axis of the lighting element and each having a light output axis directed outwardly perpendicular to the optical axis towards the inner surface of the reflector dome. For a given reflector area the total light emitting area of the solid state light source arrangement is increased by a factor of 3 compared to a conventional lighting element. The reflector is elliptical, and the lighting units each comprise an array of LEDs. This enables a large light output flux while maintaining a desired narrow beam light output.

In the description and claims below, the terms "lighting element", "lighting unit" and "light source arrangement" are used. These terms are intended simply to distinguish between different elements and they are not intended to have any special meaning. The "lighting element" is the overall system comprising a light source and a reflector. The "light source arrangement" is the light source associated with one reflector. The "lighting unit" is one part of the "light source arrangement"; in particular each light source arrangement has three lighting units.

Figure 2 shows a lighting element 20 with the components shown in transparent form, and comprising a solid state light source arrangement 22 and a reflector dome 24. The reflector dome 24 has a bottom 26 and a circular open top 28 with an optical axis 30 directed between the bottom and the center of the circular open top 28. The bottom is for example a planar reflective surface to reflect downwardly emitted light back to the reflector dome. The optical axis 30 is the general light output direction. The light source arrangement 22 is located at the bottom.

The reflector dome 24 comprises an outer wall with a reflective inner surface 32. The solid state light source arrangement 22 comprises three lighting units 34, two of which can be seen in Figure 2. They are angularly spaced around the optical axis 30 with an even spacing of 120 degrees, and each has a light output axis 36 which is directed radially outwardly perpendicular to the optical axis 30 and towards the inner surface 32 of the outer wall 24.

Each lighting unit 34 makes use of one third of the reflector inner surface. In this way, for a given reflector area (e.g. the area of the circular open top 28) the total light emitting area of the solid state light source arrangement is increased by a factor of 3 compared to a conventional lighting element.

Each lighting unit 34 has an output which is within a 120 degree cone, in particular so that at least 95% of the light output flux is within this cone. As a result, each lighting unit 34 is associated only with its respective one third of the reflector.

The reflective inner surface 32 comprises a specular reflector so that a very narrow beam may be generated, for example with full width at half maximum (FWHM) of less than 10 degrees. In the example shown, a set of radial dividers 38 is provided which divide the volume of the reflector dome into three dome sectors, with lighting unit 34 in each dome sector. These dividers prevent any interference between the light outputs of the lighting units, for stray light which is emitted outside a 120 degree cone.

The dividers are made of flat high reflective parts on both sides. These dividers are optional. The more the light output from the light source is confined within a 120 degree cone, the less the benefit or need for the dividers.

Figure 3 shows the lighting element 20 of Figure 2 with the components shown in solid form.

Figure 4 shows the lighting element 20 of Figure 2 in plan view.

Figure 5 shows the planar reflector bottom 26 which is a separate component to the rest of the reflector dome, and which functions as the mounting surface for the light source arrangement 22. Figure 5 shows that each lighting unit 34 comprises an LED chip on board arrangement and it shows separate LED driver circuitry 50.

The LED chip on board arrangement is shown more clearly in Figure 6 as a regular array of LED chips 60, such as 44 LED chips 60 in the example shown, formed into an essentially circular array. The area of the array is for example in the range 2 mm² to 10 mm².

Figure 6 also shows an optional improvement by which the LED chip in the center of the array is omitted (or it may be present but not connected). This is of particular interest for color mixing if the array includes LED chips of different color. The LED chips of any given color may then be arranged in groups angularly spaced around the central light output axis 36 (and there is no LED chip actually generating light along that axis). For example, the LED chips of a given color may be arranged in pairs on opposite sides of the central axis, or in fours each at 90 degrees to each other around the optical axis. Of course, any other rotationally symmetric configuration may be used. This improves color mixing in the output beam. In this way, all LED chips are spaced laterally from the central light output axis 36 as well as spaced along that light output axis 36 from the focal point, since the focal point lies on the optical axis 30. The LED array is generally spaced from and in front of the focal point.

This omitted central LED chip is not needed for a single color solution.

Figure 6 shows an LED array formed generally as a square. There are many other possible arrangements. If the LED chips are independently controllable, a patterned output may be generated, such as: a circle;

two diametrically opposed 90 degree quadrants;

a semi-circle;

an annular ring; or

a set of concentric annular rings.

These (and other) patterns may be generated dynamically, but they may instead be static for a fixed desired lighting effect. Annular rings may for example be used for color mixing.

The reflector shape is chosen to create the most accurate illumination at a desired distance from the lighting element. By way of example, an illumination distance of 25 m is typically desired for stadium light, more generally in the range 10 m to 50 m, for example in the range 20 m to 30 m.

An elliptical reflector shape is one option, with the distance between the two focal points corresponding to this desired illumination range. The elliptical reflector shape is repeated in the 3 sectors.

Figure 7 shows one example of possible elliptical cross sectional shape. The light source arrangement 22 is provided in the vicinity of one of the focal points, in particular the proximal focal point which lies within the reflector. The other, distal, focal point lies outside the reflector dome at a remote distance from the lighting element. In particular, the lighting units direct light along an axis which (when extended behind the lighting unit) extends through that focal point.

In the example shown, the diameter of the open top is 468 mm (214 + 214 +20 +20) and the height of the reflector is 293 mm with the focal point 39 mm from the bottom of the reflector.

In one design, the aim is to provide a narrow beam, for example with the intensity distribution shown in Figure 8, with a FWHM of 10 degrees.

In order to generate wider beams the finishing of the inner surface of the reflector can be modified from highly specular to partially diffuse. Wider beams can also be generated by using secondary optics added at the open top 28.

These optics may also be used as cooling elements, in addition to a heat sink beneath the bottom 26.

One arrangement of lighting elements 20 to form a luminaire 90 is shown in Figure 9. The luminaire comprises 14 lighting elements 20 in an array having a row of three, two rows of four and a final row of three and being arranged in a densest hexagonal packing. This may for example fit into a conventional luminaire with dimensions 616mm x 616mm (and l30mm depth). As further schematically shown in Figure 9, of the luminaire 90 essentially a first half of the fourteen lighting elements 20 is arranged in a sixty degrees rotation about a respective optical axis 30 with respect to a second half of the lighting elements 20'. Here, two mutually unmixed first and second halves are shown, however, the first half of lighting elements 20 and the second half of lighting elements 20’ may also be arranged in a mutually mixed arrangement.

The light output flux of the luminaire is for example greater than 50 klm for outdoor lighting such as for stadium lighting. Of course, the same design may be scaled to any size.

Figure 10 shows an electrical circuit to manage the 42 LED chip on boards used in the luminaire of Figure 9.

A three channels driver 100 is used. On each channel, a current splitter 102 is used to split the current in two and then manage two separated strings of 7 chip on board lighting units 34.

Each sector is individually controllable. The three sectors may all be the same color or there may be one primary color per sector within each lighting element 20. The use of three channels gives the system flexibility.

The invention enables a target lumen to be achieved with the desired efficiency and quality.

Figure 11 shows a football stadium 1000 provided with a stadium lighting system 101. A controller 103 is in communication with (a plurality of) said stadium lighting system 101. Said controller 103 is configured to adjust the lighting systems 101 to illuminate the desired locations of the stadium based on sensor data received from a sensor system 105 in communication with the controller, such data comprise for example illuminance levels at various locations in the stadium.

Multiple luminaires of Figure 9 may be used in a stadium lighting system. However, the invention is equally applicable to other lighting applications, in particular outdoor lighting applications requiring high light flux with narrow beam illumination for illuminating a target surface or object.

The lighting element preferably makes use of LEDs. However, the same design may be implemented with other solid state lighting solutions. The LEDs also do not have to be in the form of a chip on board arrangement. They may be discrete LED packages. 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 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.

Claims

CLAIMS:

1. A stadium lighting system comprising a plurality of luminaires (90), wherein each luminaire comprises a plurality of lighting elements (20), each lighting element (20), comprising:

a solid state light source arrangement (22); and

a reflector dome (24), having a bottom (26) and a circular open top (28) with an optical axis (30) directed between the bottom and the center of the circular open top, wherein the light source arrangement is located at the bottom,

wherein the reflector dome comprises an outer wall with a reflective inner surface (32) and wherein the solid state light source arrangement comprises three lighting units (34) equally angularly spaced around the optical axis (30) and each having a central light output axis (36) directed outwardly perpendicular to the optical axis (30) towards the inner surface of the outer wall,

wherein the reflector dome (34) comprises a portion of an elliptical reflector with a proximal focal point within the reflector dome (24) and a distal focal point outside the reflector dome, and

2. A stadium lighting system as claimed in claim 1, wherein for each lighting unit (34) at least 95% of the output is within a cone of cone angle 120 degrees.

3. A stadium lighting system as claimed in claim 1 or 2, wherein the reflective inner surface (32) comprises a specular reflector.

4. A stadium lighting system as claimed in any preceding claim, wherein each lighting element further comprises a set of dividers (38) which divide the volume of the reflector dome into three dome sectors, wherein each dome sector extends over 120 degrees and wherein one lighting unit is in each dome sector.

5. A stadium lighting system as claimed in claim 4, wherein the dividers (34) are reflective on both sides.

6. A stadium lighting system as claimed in any preceding claim, wherein each lighting unit (34) comprises an LED chip on board arrangement.

7. A stadium lighting system as claimed in any preceding claim, wherein the distance between the proximal and distal focal points of the elliptical reflector is in the range 10 m to 50 m, preferably in the range 20 m to 30 m.

8. A stadium lighting system t as claimed in any preceding claim, further comprising secondary optics over the circular open top.

9. A stadium lighting system wherein each luminaire comprises 14 lighting elements.

10. A stadium lighting system wherein each luminaire has a light output flux greater than 150 klm.

11. A luminaire (90) suitable for use in the stadium lighting system as claimed in any one of the claims 1 to 10, wherein the luminaire comprises at least 14 lighting elements (20) arranged in a hexagonal packing.

12. A luminaire as claimed in claim 11, wherein essentially a first half of the lighting elements (20) is arranged in a 60 degrees rotation about a respective optical axis (30) with respect to a second half of the lighting elements (20').