WO2025061622A1

WO2025061622A1 - A luminaire

Info

Publication number: WO2025061622A1
Application number: PCT/EP2024/075803
Authority: WO
Inventors: Minghui SHI; Wenxue ZHU; Liwen ZHOU
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2023-09-21
Filing date: 2024-09-16
Publication date: 2025-03-27
Anticipated expiration: 2026-03-21

Abstract

A luminaire comprising a first lighting element and an array of second lighting elements that surround the first lighting element. The first lighting element emits a beam of light centered around a first beam axis. The second lighting elements emit light away from the first lighting element, each second lighting element emitting a beam of light centered around a respective second beam axis. The angle between each second beam axis and the first beam axis is between 45° and 90°.

Description

A LUMINAIRE

FIELD OF THE INVENTION

The present invention relates to the field of artificial lighting, and in particular, to luminaires for providing artificial lighting.

BACKGROUND OF THE INVENTION

There is an ongoing desire to improve artificial lighting arrangements, which are used to provide artificial light in a wide variety of environments, such as in domestic, industrial and/or public settings.

One area of particular interest is the use of so-called artificial skylights. These are luminaires that are designed to simulate or emulate a window providing daylight (e.g., an appearance of the sky and/or sun). Such artificial skylights are typically, but not essentially, mounted to a ceiling.

There is an ongoing desire to reduce the artificial appearance of a luminaire that is able to function as an artificial skylight.

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 luminaire comprising: a first lighting element occupying a central portion of the luminaire, configured to emit light, wherein the light emitted by the first lighting element is centered around a first beam axis and an array of second lighting elements, surrounding the central portion of the luminaire, configured to emit light in directions away from the first beam axis, wherein the light emitted by each second lighting element is centered around a respective second beam axis, wherein each second beam axis makes an angle of between 45° and 90° to the first beam axis.

The present disclosure provides a luminaire that emits first light in a first general direction and second light in directions away from this first general direction, having an angle of between 45° and 90° to this first general direction. This advantageously increases a perceived size of the first light, increasing a resemblance of the luminaire to a true skylight. In some examples, the luminaire further comprises a diffuser surrounding the array of second lighting elements and configured to receive the light emitted by the array of second lighting elements. This provides improved light distribution of the light emitted by the array of second lighting elements, reducing a perception that the luminaire provides artificial light.

In some examples, the cross-sectional shape of the diffuser, in any half-plane bound by the first beam axis and containing any second beam axis, is curved.

In some examples, the cross-sectional shape of the diffuser, in any half-plane bound by the first beam axis and containing any second beam axis, is an arc segment or an annular segment.

In some embodiments, the array of second lighting elements comprises: a first layer of second lighting elements lying in a first plane orthogonal to the first beam axis; and a second layer of second lighting elements, lying in a second plane orthogonal to the first beam axis, the second plane being parallel to the first plane.

This approach provides a technique for facilitating a gradient light effect in light emitted by the array of second lighting elements. In particular, by defining two separate layers or rows of second lighting elements, different colored light emitted by each layer will undergo color mixing by the diffuser to form a gradient. This can be used to advantage to provide a gradient effect, for instance, resembling a light condition such as sunrise or sunset.

Alternatively, if both layers emit light having the same color and/or color temperature, then the proposed multi-layer array of second lighting elements also acts to improve a uniformity of light distribution across the diffuser, and therefore of light output by the luminaire using the array of second lighting elements.

In some examples, first layer of second lighting elements emits light of a different color and/or color temperature to the second layer of second lighting elements. This provides a gradient lighting effect for light emitted out of the luminaire using the second lighting elements.

In some examples, the smallest distance, in a direction parallel to the first beam axis between any one of the second lighting elements and the diffuser is no greater the distance between the first plane and the second plane, e.g., no greater than half the distance between the first plane and the second plane. This size relationship increases the likelihood that there will be a natural gradient effect of color light, or (if both layers emit light of a same color) that there is uniform brightness distribution. In some examples, the sagitta of the cross-sectional shape of the diffuser in any half-plane bound by the first beam axis and containing and second beam axis, is between 0.6 and 1.4 times the distance between the first and second planes. This size relationship also increases the likelihood that there will be a natural gradient effect of color light, or (if both layers emit light of a same color) that there is a more uniform brightness distribution.

The luminaire may further comprise an array of third lighting elements, surrounding the central portion of the luminaire, configured to emit light in directions towards the first beam axis. Light emitted by the array of third lighting elements thereby represents or resembles surfaces illuminated by the first lighting element (e.g., emulating surfaces illuminated by daylight or natural light). Use of the array of third lighting elements thereby increases the resemblance of the luminaire to a true skylight.

In some examples, the light emitted by each third lighting element is centered around a respective third beam axis, wherein each third beam axis makes an angle of between 45° and 90° to the first beam axis.

The array of second lighting elements and the array of third lighting elements may be mounted on a same heat sink. This approach significantly reduces a material cost and weight of the luminaire. A reduced weight for the luminaire advantageously increases an ease of installing and/or assembling the luminaire.

In some examples, the heat sink comprises a tubular element that surrounds the central portion of the luminaire. Such a shape and structure provides good structural integrity for the heat sink, and well as improved heat dissipation. However, other shapes and configurations for the heat-sink are envisaged.

The first lighting element may comprise a light exit plate comprising a light outputting surface from which light is emitted out of the first lighting element; and a first light source configured to illuminate the entirety of the light outputting surface. This causes the first lighting element to operate or function as a panel light, which more closely resembles a window or other surface that transmits daylight.

In preferred examples, the size of the light outputting surface is no less than 100 cm². In this way, the first light emitting element can effectively operate as a panel light or luminous surface for an artificial skylight.

In preferred examples, the first lighting element is configured to emit light having a wavelength of between 400 nm and 500 nm. Thus, the first light emitting element may be configured to emit blue light. 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

For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

Figure 1 is an exploded view of a proposed luminaire;

Figure 2 is a partially exploded view of the proposed luminaire;

Figure 3 illustrates the proposed luminaire;

Figure 4 is a cross-sectional view of the proposed luminaire;

Figure 5 is a cross-sectional view of an alternative luminaire;

Figure 6 illustrates a cut section of the alternative luminaire;

Figure 7 is an enlarged cross-sectional view of a portion of the alternative luminaire;

Figure 8 is a cross-sectional view of another alternative luminaire;

Figure 9 is a cross-sectional view of yet another alternative luminaire; and

Figure 10 illustrates a luminaire.

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 luminaire comprising a first lighting element and an array of second lighting elements that surround the first lighting element. The first lighting element emits a beam of light centered around a first beam axis. The second lighting elements emit light away from the first lighting element, each second lighting element emitting a beam of light centered around a respective second beam axis. The angle between each second beam axis and the first beam axis is between 45° and 90°.

Figure 1 provides an exploded view of a proposed luminaire 100, for improved understanding of the various elements of the luminaire 100.

The luminaire 100 comprises a first lighting element 110 and an array 120 of second lighting elements.

The first lighting element 110 occupies a central portion of the luminaire 100. The first lighting element 100 is configured to emit light. The light emitted by the first lighting element is centered around a first beam axis Xi. In particular examples, the first beam axis Xi intersects a center of the luminaire 100.

Preferably, the direction of the first beam axis is in a direction away from a surface to which the luminaire is mounted or located. For example, if the luminaire 100 is positioned on a ceiling, then the first beam axis Xi may be in a downward direction. Preferably, the luminaire 100 is completed protruded from a mounting surface of a ceiling.

More particularly, the first lighting element may comprise a light exit plate 111, having a light outputting surface 112, and a first light source 115. The first light source 115 is configured to illuminate the entirety of the light outputting surface 112. In this way, the first lighting element effectively functions or acts as a panel light, lighting panel or luminous surface.

Put another way, the first lighting element 110 may be a panel light or luminous surface.

The first light source 115 may, for instance, comprise a plurality of light emitting diodes (LEDs) or alternative light producing devices, such as halogen bulbs.

The size of the light outputting surface may, for instance, be no less than 100 cm², preferably between 150 cm² and 10000 cm². This approach provides an emulation of an artificial skylight or similar.

The light exit plate 111 may, for instance, comprise a diffuser or other optical element for diffusing, scattering or redirecting light received from the first light source 115 to illuminate the light outputting surface.

In the illustrated example, the first light source 115 is configured to emit light centered around the first beam axis.

In alternative examples, the first light source 115 emits light into an edge of the light exit plate 111. Thus, the light exit plate 111 may comprise an edge-lit light guide that receives light at one or more edges of the light exit plate and outputs light at the light outputting surface 112 that is centered around the first beam axis Xi.

The array 120 of second lighting elements surrounds the central portion of the luminaire 100, i.e., the first lighting element 110. Thus, the array 120 of second lighting elements surrounds, e.g., encircles, the first beam axis Xi.

Each second lighting element is configured to emit light in a direction away from the first beam axis. Thus, the distance between any photon of light emitted by each second lighting element and the first beam axis Xi will increase over time (assuming that said photon of light is not interrupted or redirected).

The light emitted by each second lighting element is centered around a respective second beam axis Y i. Thus, each second lighting element has its own second beam axis Y i around which the light emitted by said second lighting element is centered.

The angle between each second beam axis Yi and the first beam axis Xi is between 45° and 90°. This has been identified as having an effect of increased perceived size of the first lighting element 110. More particularly, arranging the first lighting element and the array of second lighting elements in this way decreases a visibility of a physical bound between the first lighting element and a viewer of the luminaire, thereby increasing the perceived size of the first lighting element.

More preferably, the angle between each second beam axis Y i and the first beam axis is between 60° and 90°, more preferably between 80° and 90° and more preferably between 89° and 90° (e.g., 90°). The effect of increased perceived size for the first lighting element is increased the closer the angle between each second beam axis Y i and the first beam axis Xi is to 90°.

In the illustrated example, the angle between each second beam axis Y i and the first beam axis is 90°. However, the skilled person would readily appreciate how to reconfigure the second lighting elements to provide an alternative angle for each second beam axis Y i with respect to the first beam axis Xi.

In the context of the present disclosure, the angle between a second beam axis Yi and the first beam axis Xi is the smallest angle between the two axes.

Each second lighting element may, for instance, comprise one or more light emitting diodes (LEDs) or alternative light producing devices, such as halogen bulbs.

Preferably, the first and second lighting elements are configured to emit light of different wavelength ranges. In some examples, the first lighting element comprises one or more LEDs configured to emit red light, blue light, green light, and/or white light having a color temperature between 5500 Kelvin (“K”) and 7000K. The second lighting elements may comprise LEDs configured to emit red light, blue light, green light, and/or warm white light having a color temperature between 2500K and 3500K, and/or cool white light having a color temperature between 5500K and 7000K.

For instance, the first lighting element may be configured to emit light having a wavelength of between 400 nm and 500 nm (i.e., blue light), whereas each second lighting element may be configured to emit light having a wider wavelength range (e.g., white light). Other variations will be apparent to the skilled person, and may depend upon user preference and/or specific use-case scenario.

The array 120 of second lighting elements may be mounted on a heat sink 125. The heat sink 125 may take the form of a tubular element that surrounds the central portion of the luminaire, i.e., the first lighting element 110. This configuration increases the sturdiness of the heat sink, and improves the structural integrity of the luminaire.

In some examples, the first lighting element abuts or fits within the hollow center of the heat sink 125.

The luminaire 100 may further comprise a diffuser 130 that surrounds the array 120 of second lighting elements. The diffuser 130 may be configured to receive (and diffuse/scatter) the light emitted by the array 120 of second lighting elements. As later described in detail, the diffuser may have a curved cross-sectional shape in a half-plane bound by (i.e., originating at) the first beam axis and intersecting any one of the second light beam axes. In effect, the diffuser may form or define a curved (diffusive) surface that wraps around the array 120 of second lighting elements.

Figure 2 illustrates a partially assembled luminaire 100 for improved contextual understanding regarding the positional relationship between the elements of the luminaire 100.

Figure 3 illustrates an assembled luminaire 100 for improved contextual understanding.

Figure 4 provides a cross-sectional view of the luminaire 100.

Figure 4 illustrates the angular relationship between the first beam axis Xi and each second beam axis Y i, namely how they are angled with respect to one another.

Figure 4 also illustrates the shape of the diffuser 130, namely the curved or arcuate shape of the diffuser.

More particularly, Figure 4 illustrates how the diffuser has a curved cross- sectional shape in a half-plane originating at the first beam axis and intersecting any one of the second light beam axes. One such plane is exemplified by the plane of the cross-sectional view of the luminaire illustrated by Figure 4.

Figure 4 also illustrates optional additional features of the luminaire 100.

In particular, the luminaire may comprise a mounting element 405, configured to mount the luminaire to a surface, such as a ceiling. Examples of mounting elements are well known to the skilled person. The mounting element may act as a backplate for the luminaire 100. The mounting element may, for instance, couple to first lighting element and the heat sink 125 for the array 120 of second lighting elements.

The luminaire 100 may comprise a support plate 407 for supporting elements of the luminaire, including at least the first lighting element 110 and the array 120 of second lighting elements. If present, the support plate 407 may connect or mount the heat sink 125 thereto.

Preferably, the mounting element 405 connects to the support plate 407 and/or remainder of the luminaire 100 by a twist-and-click mechanism or other clipping mechanism. This advantageously increases an ease of assembling or installing the luminaire.

In one example, the mounting element comprises one or more safety cable clips. The support plate 407 may comprise one or more safety cables that each connect to a respective safety cable clip for securing the mounting element 405 to the support plate 407 before using the clipping mechanism. Thus, during an installation of the luminaire 100, the mounting element may be positioned against a surface, each safety cable may be engaged with a respective safety cable clip (to reduce a risk of dropping or damaging the luminaire during later installation), before the support plate 407 is engaged to the mounting element using the clipping mechanism.

The luminaire 100 may further comprise a power system 410 configured to provide power for driving the first lighting element 110 and the array 120 of second lighting elements. Approaches for appropriately driving or powering lighting elements are well known in the art. The power system 410 may, for instance, convert a mains power supply to one or more lighting power supplies for the first lighting element 110 and the array 120 of second lighting elements.

The luminaire 100 may further comprise a control system 420 configured to control the operation of the first lighting element 110 and the array 120 of second lighting elements, e.g., control whether or not the first/second lighting elements emit light and/or control one or more lighting properties (e.g., color, color temperature, intensity and so on) of the first and second lighting elements. Approaches for controlling such lighting properties are well established in the art.

Figures 5, 6 and 7 illustrate portions of an alternative luminaire 500. Figure 5 provides a cross-sectional view of the luminaire 500. Figure 6 provides a perspective cut-out view of a portion of the luminaire. Figure 7 provides an enlarged cross-sectional view of the array of second lighting elements and the diffuser.

In Figures 5, 6 and 7 elements of the luminaire 500 that are similar or the same as previously described and identified elements have the same reference numerals, and may not be described in detail for the sake of conciseness.

The luminaire 500 differs from the previously described luminaire in that the array of second lighting elements comprises a plurality of layers 521, 522 of second lighting elements.

In particular, the array 520 of second lighting elements comprises at least a first layer 521 of second lighting elements lying in a first plane pl orthogonal to the first beam axis Xi; and a second layer of second lighting elements, lying in a second plane p2 orthogonal to the first beam axis Xi The second plane is parallel to the first plane.

Thus, the array 520 of second lighting elements comprises two or more rows (i.e. , layers) of second lighting elements. Each row or layer encircles or surrounds the central portion of the luminaire, i.e., the first lighting element 110.

It will be appreciated that each second beam axis Y i will continue to make an angle of between 0° and 45° with respect to the first and/or second plane, e.g., between 0° and 30°, e.g., between 0° and 15°, e.g., between 0° and 1° (e.g., 0°).

The diffuser 130 is positioned such that the curved cross-sectional shape of the diffuser curves away from each row or layer. The sagitta of the curved cross-sectional shape of the diffuser (in any half-plane originating at the first beam axis and intersecting any one of the second light beam axes) is preferably orthogonal to the first beam axis Xi, but this is not essential.

In particular, as best illustrated by Figure 7, in any half-plane originating at the first beam axis and intersecting any one of the second light beam axes, the diffuser 130 has an arcuate shape. The arcuate shape defines a center of curvature 700. A dividing plane pd, parallel to the first plane pl and second plane p2, that intersects this center of curvature 700 lies between the first plane pl and the second plane p2. The dividing plane thereby divides the diffuser into two hypothetical halves (which are not necessarily equal in size). Thus, the first 521 and second 522 layers of second lighting elements may he either side of a dividing plane pd that divides the diffuser (into two hypothetical halves) and lies orthogonal to the first beam axis Xi.

The dividing plane pd may intersect the midpoint of the arcuate shape of the diffuser 700.

More preferably, the distance between the first layer 521 and the dividing plane pd is (substantially) the same as the distance between the second layer 522 of second lighting elements and the dividing plane.

The first layer 521 of second lighting elements may be configured to emit light of a different color and/or color temperature to the second layer 522 of second lighting elements.

In some examples, the distance d between the first plane pl and the second plane p2 is between 1cm and 15 cm, preferably between 2cm and 10cm.

In some examples, the smallest distance ds, in a direction parallel to the first beam axis between any one of the second lighting elements and the diffuser is no greater than the distance d between the first plane pl and the second plane p2. The distance between the first plane pl and the second plane p2 may be labelled an interplane distance d. More preferably, the smallest distance ds, in a direction parallel to the first beam axis between any one of the second lighting elements and the diffuser is no greater than half the distance d between the first plane pl and the second plane p2 (i.e., 0.5d).

The sagitta h of the cross-sectional shape of the diffuser in any half-plane bound by the first beam axis and containing and second beam axis, is between 0.6 and 1.4 times the distance d between the first and second planes, i.e., between 0.6 and 1.4 times the interplane distance d. This approach improves the evenness or uniformity of light distribution and light mixing of light emitted by the first and second layers of second lighting elements in the array of second lighting elements.

Thus, the ratio L between the sagitta h and the inter-plane distance d (i.e., h/d) may have a value of between 0.6 and 1.4 inclusive, i.e., 0.6 < L < 1.4. More preferably, the ratio L has a value of between 0.8 and 1.2 inclusive, and more preferably between 0.9 and 1.1 inclusive. The closer the value of L is to 1, the greater the evenness or uniformity of light distribution and light mixing of light emitted by the first and second layers of second lighting elements in the array of second lighting elements.

Figure 8 provides a cross-sectional view of an alternative luminaire 800. Elements of the luminaire 800 that are similar or the same as previously described and identified elements have the same reference numerals, and may not be described in detail for the sake of conciseness.

The alternative luminaire 800 differs from the luminaire described with reference to Figures 1 to 4, in that the luminaire 800 further comprises an array 810 of third lighting elements.

The array 810 of third lighting elements surround the central portion of the luminaire (i. e. , surrounds the first lighting element) and is configured to emit light in directions towards the first beam axis Xi. Thus, the distance between any photon of light emitted by each third lighting element and the first beam axis Xi will (at least initially) decrease over time, e.g., until it passes the first beam axis Xi.

Preferably, the light emitted by each third lighting element is centered around a respective third beam axis Y2, wherein each third beam axis makes an angle of between 45° and 90° to the first beam axis. Thus, the angle between each third beam axis Y2 and each second light beam axis Y 1 is between 90° and 180°.

More preferably, the angle between each third beam axis Y2 and the first beam axis Xi is between 60° and 90°, more preferably between 80° and 90° and more preferably between 89° and 90° (e.g., 90°).

In preferred examples, the array 120 of second lighting elements and the array 810 of third lighting elements are mounted on a same heat sink 125. This significantly reduces a material cost and weight of the luminaire 800.

The heat sink 125 may therefore be a heat sink that surrounds or encircles the central portion (i.e., the first lighting element) upon which the array 120 of second lighting elements and the array 810 of third lighting elements are mounted. The array of second lighting elements emit light outwardly from the heat sink 125 (i.e., outwardly from the luminaire). The array 810 of third lighting elements emit light inwardly with respect to the heat sink 125 (i.e., inwardly from the luminaire).

As illustrated in Figure 8, the light exit plate 111 of the first lighting element 110 is preferably disposed between the first light source 115 and the array 810 of third lighting elements. In this way, when illuminating an environment, the light emitted by the array of third lighting elements is not subject to modification or alteration by the light exit plate.

The third lighting elements may comprise LEDs configured to emit warm white light having a color temperature between 2500K and 3500K, and/or cool white light having a color temperature between 5500K and 7000K. In preferred examples, each third lighting element is configured to produce light with a color temperature between 4000 Kelvin and 5500 Kelvin. This emulates luminance of a sun struck surface, to increase the illusion that the luminaire is a true skylight.

Figure 9 provides a cross-sectional view of an alternative luminaire 900. Elements of the luminaire 900 that are similar or the same as previously described and identified elements have the same reference numerals, and may not be described in detail for the sake of conciseness.

The alternative luminaire 900 differs from the luminaire 500 described with reference to Figures 5 to 7, in that the luminaire 900 further comprises the array 810 of third lighting elements.

Thus, the alternative luminaire 900 comprises the array 520 of second lighting elements (comprising two or more layers 521, 522 of second lighting elements) and the array 810 of third lighting elements.

As previously explained, any herein described luminaire may comprise a mounting element 405, configured to mount the luminaire to a surface, such as a ceiling.

Figure 10 illustrates a luminaire 100 during an installation process that illustrates optional features and elements for the mounting element 405. These features may form part of any herein disclosed luminaire.

Preferably, the mounting element 405 comprises a clipping mechanism 1050 for connecting the mounting element 405 to the remainder of the luminaire, e.g., the support plate (not visible in Figure 10). The clipping mechanism 1050 may, for instance, comprise a twist- and-click mechanism.

One difficulty with installing a luminaire using such a clipping mechanism is the risk of dropping part of the luminaire (i.e., the part not containing the mounting element), which risks damaging the lighting elements. This is particularly problematic if the luminaire is to be installed to a ceiling. Moreover, using a twist-and-click mechanism is easier for an installer if both of the installer’s hand can be used to perform the twisting motion.

To mitigate the risk of dropping (part ol) the luminaire, the mounting element may comprise one or more safety cable clips 1010. The support plate (not visible in Figure 10) may comprise one or more safety cables 1020 that connect to a respective safety cable clip 1010 for (e.g., temporarily) securing the mounting element 405 to the support plate before using the clipping mechanism.

In this way, during an installation of the luminaire 100, the mounting element may be positioned against a surface, each safety cable 1020 may be engaged with a respective safety cable clip 405 (to reduce a risk of dropping or damaging the luminaire during installation), before the support plate is engaged to the mounting element using the clipping mechanism.

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.

If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A luminaire (100, 500, 800, 900) comprising: a first lighting element (110), occupying a central portion of the luminaire, configured to emit light, wherein the light emitted by the first lighting element is centered around a first beam axis (Xi), and the first lighting elements comprising a light outputting surface (112) and a first light source (115), the first light source (115) is configured to illuminate the light outputting surface (112); an array (120, 520) of second lighting elements, surrounding the central portion of the luminaire, configured to emit light in directions away from the first beam axis, wherein the light emitted by each second lighting element is centered around a respective second beam axis (Y i), wherein each second beam axis makes an angle of between 45° and 90° to the first beam axis; a diffuser (130) surrounding the array of second lighting elements and configured to receive the light emitted by the array of second lighting elements; and the array of second lighting elements comprises a first layer (521) of second lighting elements lying in a first plane (pl) orthogonal to the first beam axis; and a second layer (522) of second lighting elements lying in a second plane (p2) orthogonal to the first beam axis, and the second plane being parallel to the first plane.

2. The luminaire of claim 1, wherein the cross-sectional shape of the diffuser, in any half-plane bound by the first beam axis and containing any second beam axis, is curved.

3. The luminaire of claim 2, wherein the cross-sectional shape of the diffuser, in any half-plane bound by the first beam axis and containing any second beam axis, is an arc segment or an annular segment.

4. The luminaire of claim 1, wherein the first layer of second lighting elements emits light of a different color and/or color temperature to the second layer of second lighting elements.

5. The luminaire of claim 1, wherein the smallest distance (ds), in a direction parallel to the first beam axis between any one of the second lighting elements and the diffuser is no greater than a half of the distance between the first plane and the second plane.

6. The luminaire of any of claims 1 to 5, wherein the sagitta (h) of the cross- sectional shape of the diffuser in any half-plane bound by the first beam axis and containing and second beam axis, is between 0.6 and 1.4 times the distance between the first and second planes.

7. The luminaire of any of claims 1 to 6, further comprising an array (810) of third lighting elements, surrounding the central portion of the luminaire, configured to emit light in directions towards the first beam axis.

8. The luminaire of claim 7, wherein the light emitted by each third lighting element is centered around a respective third beam axis, wherein each third beam axis makes an angle of between 45° and 90° to the first beam axis.

9. The luminaire of any of claims 7 or 8, wherein the array of second lighting elements and the array of third lighting elements are mounted on a same heat sink.

10. The luminaire of claim 9, wherein the heat sink comprises a tubular element that surrounds the central portion of the luminaire.

11. The luminaire of any of claims 1 to 10, wherein the first lighting element comprises: a light exit plate (111) comprising the light outputting surface (112) from which light is emitted out of the first lighting element; and the first light source (115) configured to illuminate the entirety of the light outputting surface.

12. The luminaire of claim 11, wherein the size of the light outputting surface is no less than 100 cm².

13. The luminaire of any of claims 1 to 12, wherein the first lighting element is configured to emit light having a wavelength of between 400 nm and 500 nm.