luminaire

Abstract

A luminaire comprising a light guide plate, a light source and a reflector. The light source is provided at a first side edge of the light guide plate, which extends between a pair of intact specular TIR surfaces of the light guide plate. Light emitted by the light source enters the light guide plate at the first side edge and exits at a second side edge, which also extends between the pair of TIR surfaces. The reflector is provided on one of the TIR surfaces, and extends away from the light guide plate from the second side edge. Both the first light guide plate and the reflector are flat and are parallel to each other.

Description

[0001] LUMINAIRE

[0002] FIELD OF THE INVENTION

[0003] The invention relates to the field of lighting, and, in particular, to luminaires for illuminating a ceiling.

[0004] BACKGROUND OF THE INVENTION

[0005] It is now accepted that best-practice lighting solutions illuminate an indoor space (i.e. illuminating all visible surfaces in an indoor environment), rather than illuminating only a particular task. This concept is outlined, for example, in the EN 12464-1(2021) Lighting Standard.

[0006] Some existing luminaires for illuminating a ceiling are mounted on the ceiling; these luminaires typically provide a bright “halo” of light around the luminaire, with a sharp decrease in illumination beyond the halo. An alternative solution (typically used to in long, narrow spaces) involves a beam or bar mounted to opposite walls of a room and / or suspended from the ceiling, with LEDs provided on a ceiling-facing surface. This solution is difficult to install, as the beam / bar must be fixed tightly to the walls and / or ceiling, and the beam shape of each LED must be controlled to provide uniform illumination. Further, the beam / bar is generally considered obtrusive and unsightly.

[0007] There is an ongoing desire to provide improved lighting solutions for illuminating ceilings.

[0008] US 20140029292A1 discloses a linear lighting device which includes an elongated light guide, a light source disposed at an end in a longitudinal direction of the light guide, and a case accommodating the light guide and the light source. In the linear lighting device, the light guide has a plurality of grooves arranged in the longitudinal direction of the light guide, and has a stepped cutout at the other end on an opposite side from the end, and a protruding portion protruding into the cutout is formed on an inner surface of the case which faces the cutout.

[0009] US 20080186726A1 discloses an LED lighting unit that uses a light guide. The LED lighting unit can include a light guide having one flat surface formed with many light diffusing patterns, a plurality of LEDs located along one end surface of the light guide, and a reflection board including a reflector located on a bend portion thereof.

[0010] SUMMARY OF THE INVENTION

[0011] The invention is defined by the claims.

[0012] According to examples in accordance with an aspect of the invention, there is provided a luminaire, comprising: a first light guide plate comprising: a first total internal reflection, TIR, surface; a second TIR surface wherein each TIR surface is an intact specular surface with no light extraction feature; a first side edge extending between the first TIR surface and the second TIR surface as a light in-coupling port; and a second side edge extending between the first TIR surface and the second TIR surface as a light out-coupling port; a first light source, provided at the first side edge of the first light guide plate and configured to emit light towards the first side edge, such that light emitted by the first light source enters the first light guide plate at the first side edge, and is output from the first light guide plate at a second side edge of the first light guide plate; and a reflector, provided on the first TIR surface and extending away from the first light guide plate from the second side edge; wherein both the first light guide plate and the reflector are flat and are parallel to each other.

[0013] In this way, none of the TIR surfaces has any light extraction feature, so that the total internal reflection on these surfaces is not destroyed by such light extraction feature as normal backlights of prior art. Most light is guided by the first light guide plate via the first and second TIR surface and outputs from the second side edge of the first light guide plate, and is projected to lateral directions which are either parallel or at a small angle with respect to the flat light guide plate and reflector, and a small portion of light is reflected onto a target surface by the reflector. This arrangement provides uniform light over a large area of the target surface (such as a ceiling). Further, the reflector portion extending away from the first light guide plate from the second side edge prevents light goes to the rear side of the reflector, thus glare is reduced from the view of a person standing below the luminaire (or in other words, at the rear side of the reflector), as a greater proportion of light output from the first light guide plate is reflected towards the target surface.

[0014] In some examples, an angle between the second side edge of the first light guide plate and the reflector is less than 90°.

[0015] In other words, the second side edge is slanted to face the reflector. This provides a smoother illumination distribution. In some examples, the angle between the second side edge of the first light guide plate and the reflector is greater than 60°.

[0016] In some examples, the second side edge of the first light guide plate has a diffuse finish.

[0017] The diffuse finish mitigates the color-over-angle issue, and provides a smoother bright-dark boundary.

[0018] In some examples, the second side edge of the first light guide plate has an average roughness in the range 0.8-3.0 pm.

[0019] In some examples, a recess is provided in the first side edge of the first light guide plate for the first light source.

[0020] This improves an in-coupling efficiency of light emitted by the first light source, and increases the distance to which light output from the luminaire reaches.

[0021] In some examples, a quotient of a distance by which the reflector extends from the second side edge and a thickness of the first light guide plate is at least 2.0, wherein the thickness of the first light guide plate is a distance between the first TIR surface and the second TIR surface.

[0022] In some examples, the quotient of the distance by which the reflector extends from the second side edge and the thickness of the first light guide plate is in the range 2.0-6.0.

[0023] In some examples, the first light guide plate has a rectangular shape.

[0024] A luminaire with a rectangular-shaped light guide plate may, for example, be mounted on a side wall of a room to illuminate a ceiling. This shape may be used, in particular, to illuminate a ceiling in a long, narrow space (e.g. an aisle or corridor).

[0025] In some examples, a cut-out is provided in the first light guide plate, wherein the cut-out is centered with respect to the first light guide plate and has a same shape as the first light guide plate; the first side edge of the first light guide plate is a side edge facing the cut-out; and the second side edge of the first light guide plate is an outer edge of the light guide plate.

[0026] A luminaire with a cut-out in the light guide plate may be mounted on a target surface to be illuminated by the luminaire (e.g. on a ceiling), and may output light onto the target surface in various directions. Preferably, the inner (first) side edge and outer (second) side edge are smooth edges, in order to provide a smooth light distribution. In other words, the light guide plate and the cut-out each have a circular or elliptical shape, or a shape in which adjacent curves or lines share a common tangent at their join (i.e. an angle between adjacent curves or lines is 180° at the point at which the adjacent curves or lines join). In some examples, the first light guide plate is an annular disc, wherein the first side edge is an inner edge of the annular disc and the second side edge is an outer edge of the annular disc.

[0027] A luminaire with an annular light guide plate provides a smoother light distribution than other shapes with cut-outs.

[0028] In some examples, the luminaire is adapted to be mounted such that a distance between the second TIR surface of the first light guide plate and a ceiling is at least 120 mm, a width of the first light guide plate is at least 20 mm, and the first TIR surface and the second TIR surface each have an average roughness of Ra < 0.01 pm, such that an illuminated area of the ceiling of 2 m x 2 m around the luminaire has a maximum-to-minimum uniformity better than 10:1.

[0029] The inventors have found that a luminaire mounted at a distance of at least 120 mm from a ceiling, with a width of the first light guide plate of at least 20 mm and an average roughness of Ra < 0.01 pm for the first and second TIR surfaces, provides an illumination have a uniformity (expressed as a ratio of a greatest intensity to a lowest intensity) better than 10: 1 over an area of 2 m x 2 m. The width of the first light guide plate is a distance between the first side edge and the second side edge of the first light guide plate.

[0030] An average surface roughness of Ra < 0.01 pm meets SPI A2 requirements (i.e. the requirements for an A2 grade finish, as set out by the Society of the Plastics Industry, SPI, finish standard). In other words, the first TIR surface and the second TIR surface are smooth (such that they can be called as specular surfaces), with no light extraction features provided on the first TIR surface or the second TIR surface. In some examples, the first TIR surface and the second TIR surface each have an average roughness of Ra < 0.005 pm (meeting SPI Al requirements).

[0031] In some examples, a second light guide plate, provided on an opposite side of the reflector to the first light guide plate; and a second light source, extending along a first side edge of the second light guide plate and configured to emit light towards the first side edge of the second light guide plate, such that light emitted by the second light source enters the second light guide plate at the first side edge, and is output from a surface of the second light guide plate on an opposite side of the second light guide plate to the reflector.

[0032] In this way, the luminaire outputs light both towards and away from a target surface (e.g. both upwards and downwards light).

[0033] In some examples the luminaire further comprises a diffuser provided on the opposite surface of the second light guide plate to the reflector. In this way, light output from the luminaire away from the target surface (e.g. away from the ceiling) is diffuse, reducing glare.

[0034] In some examples, the first light source and the second light source are configured such that a luminous flux of the first light source is greater than a luminous flux of the second light source.

[0035] In some examples, the luminaire comprises a sub-assembly comprising the first light guide plate, the first light source and the reflector, wherein, the sub-assembly is moveable along an axis perpendicular to the first light guide plate.

[0036] In some examples, the luminaire comprises two or more first light guide plates, wherein: the first light source is shared with the first light guide plates. In other words, the first light source is configured to emit light towards the first side edges of the first light guide plates, and light is output from the first light guide plates at the second side edges of the first light guide plates. This approach saves the cost and space of light source and is beneficial for certain applications, e.g., wall washing from a corner to illuminate multiple walls / ceiling at a same time.

[0037] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] 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:

[0040] Figure 1 illustrates an exploded view of a luminaire, according to an embodiment of the invention;

[0041] Figure 2 illustrates a perspective view of the luminaire of Figure 1;

[0042] Figure 3 illustrates a cross-sectional view of the luminaire of Figure 1;

[0043] Figure 4 illustrates a perspective view of a luminaire, according to another embodiment of the invention;

[0044] Figure 5 illustrates a top view of the luminaire of Figure 4;

[0045] Figure 6 illustrates a side view of the luminaire of Figure 4;

[0046] Figure 7 illustrates a perspective view of a luminaire, according to yet another embodiment of the invention;

[0047] Figure 8 illustrates a cross-sectional view of a portion of the luminaire of

[0048] Figure 7; Figure 9 illustrates a perspective view of a luminaire, according to a further embodiment of the invention;

[0049] Figure 10 illustrates the inner structure of the luminaire in Figure 9 between its two configurations;

[0050] Figure 11 illustrates an explosive view of the luminaire in Figure 9;

[0051] Figure 12 illustrates a perspective view of a luminaire in its packaging state, according to yet another embodiment of the invention;

[0052] Figure 13 illustrates an explosive view of the luminaire in Figure 12;

[0053] Figure 14 illustrates a perspective view of the luminaire in Figure 12 in its assembly state;

[0054] Figure 15 illustrates a sectional view of the luminaire in Figure 12 mounted on a false ceiling, which partially enlarged view showing the sub-assembly of lighting module;

[0055] Figure 16 illustrates a side view of a luminaire, according to another embodiment of the invention, mounted at a comer of two intersecting walls (or ceiling);

[0056] Figure 17 illustrates an enlarged view of the luminaire in Figure 16;

[0057] Figure 18 illustrates a side view of a luminaire, according to a variety of the luminaire in Figure 16; and

[0058] Figure 19 illustrates the light output profile from a luminaire according to the present invention.

[0059] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] The invention will be described with reference to the Figures.

[0061] 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.

[0062] The invention provides a luminaire comprising a light guide plate, a light source and a reflector. The light source is provided at a first side edge of the light guide plate, which extends between a pair of TIR surfaces of the light guide plate. Light emitted by the light source enters the light guide plate at the first side edge and exits at a second side edge, which also extends between the pair of TIR surfaces. The reflector is provided on one of the TIR surfaces, and extends away from the light guide plate from the second side edge.

[0063] Figure 1 illustrates an exploded view of a luminaire 100, according to an embodiment of the invention. The luminaire 100 comprises a first light guide plate 110, a first light source 120, and a reflector 130. In some examples, the luminaire may further comprise a housing configured to hold the first light guide plate, first light source and reflector.

[0064] In Figure 1, the first light source 120 is a linear light source, comprising a plurality of light-emitting elements (e.g. a plurality of LEDs) provided on a linear printed circuit board, PCB. In some examples, the plurality of light-emitting elements may comprise at least a first group of light-emitting elements having a first correlated color temperature (CCT) and a second group of light-emitting elements having a second CCT, in order to enable CCT tuneability of the luminaire 100.

[0065] In Figure 1, the first light guide plate 110 and the reflector 130 each have a rectangular shape. The first light guide plate and the reflector are described in more detail below.

[0066] Figure 2 illustrates a perspective view of the luminaire 100. As Figure 2 shows, the first light source 120 is held between the housing 140 and a side edge of the first light guide plate 110. Similarly, the reflector 130 is held between the housing 140 and a surface of the first light guide plate. The housing is open at least on an opposite side of the first light guide plate to the first light source, allowing light to exit the luminaire.

[0067] Figure 3 illustrates a cross-sectional view of the luminaire 100. For illustrative purposes, the housing 140 is not included in Figure 3. Figure 3 illustrates more clearly the arrangement of the first light guide plate 110 with respect to the first light source 120 and the reflector 130.

[0068] The first light guide plate 110 comprises a first total internal reflection, TIR, surface 111, a second TIR surface 112, a first side edge 113 and a second side edge 114. The first side edge and second side edge each extend between the first TIR surface and the second TIR surface. The first side edge provides a light in-coupling port for the first light guide plate; the first light source 120 is provided at the first side edge and is configured to emit light towards the first side edge.

[0069] In some examples, the first side edge 113 of the first light guide plate 110 may be configured to provide a high in-coupling efficiency of light emitted by the first light source 120. For instance, in Figure 3, a recess for the first light source (i.e. a recess configured to receive the first light source) is provided in the first side edge. As the skilled person will readily appreciate, the shape of the recess may depend on the first light source 120. For instance, where the first light source comprises a plurality of light-emitting elements, a plurality of recesses may be provided in the first side edge, each configured to receive a respective light-emitting element. Alternatively, a single recess may extend along the length of the first side edge.

[0070] Light emitted by the first light source 120 enters the first light guide plate 110 at the first side edge 113, and is output from the first light guide plate at the second side edge 114, which provides a light out-coupling port for the first light guide plate. Most, if not all, of the light that enters the first light guide plate and is incident on either of the first TIR surface 111 and the second TIR surface 112 is reflected back towards the first light guide plate, as light emitted towards either TIR surface will generally have an angle greater than the critical angle, until the light exits the light guide plate at the second side edge.

[0071] The reflector 130 is provided on / over the first TIR surface 111 of the first light guide plate 110, and extends away from the first light guide plate from the second side edge 114. The reflector comprises a reflective surface facing the first light guide plate. In this way, light output from the light guide plate is reflected by the reflector 130 illuminating a large area of a target surface on the opposite side of the first light guide plate to the reflector (i.e. a surface facing the second TIR surface 112 of the first light guide plate). In addition to this, if any light emitted by the first light source is incident on the first TIR surface at an angle less than the critical angle for the first light guide plate, this light will be reflected by the reflector back towards the first light guide plate.

[0072] The reflector 130 extends from the second side edge 114 by a distance X. The value of the distance X may depend on the thickness T of the first light guide plate 110 (i.e. a distance between the first TIR surface 111 and the second TIR surface 112). For instance, a quotient of the distance X by which the reflector extends from the second side edge and the thickness T of the first light guide plate (i.e. X / T) may be at least 2.0. In some examples, the quotient of the distance X and the thickness T may be in the range 2.0-6.0 (i.e. 2.0 < X / T < 6.0).

[0073] Such optical arrangement achieves an asymmetrical light output profile as shown in Figure 19. Light output from the luminaire 100 is a combination of light guided by the first light guide plate 110, with the first TIR surface 111 and the second TIR surface 112, and light reflected by the reflector 130. In a preferably embodiment, the output beam is in the range of about -5° ~ +55°, among which about 95% light is projected to the target surface and about 5% is projected away from the target surface. In Figure 3, the second side edge 114 of the first light guide plate 110 is slanted to face the reflector 130, so that more of the light output by the first light guide plate is reflected by the reflector. In other words, an angle a between the second side edge and the reflector is less than 90°. In some examples, the angle a may be less than 90° but greater than 60°. Angles in the range 60° < a < 90° have been found to provide a smoother illumination distribution; the particular angle used may depend on the size of the luminaire 100, the distance between the reflector and the target surface to be illuminated by the luminaire, and the size of the target surface to be illuminated.

[0074] In some examples, the second side edge 114 of the first light guide plate 110 may have a diffuse finish, in order to provide an illumination with a smooth bright-dark boundary (i.e. rather than a sharp boundary at an edge of the illuminated area) and to mitigate the color-over-angle issue typical of wide-angle luminaires. For instance, the second side edge of the first light guide plate may have an average surface roughness of between 0.8 and 3.0 pm. A surface roughness in this range may, for example, be achieved by chemical etching, sandblasting, or coating the second side edge with scattering particles. Alternatively, the diffuse finish may be provided by a diffuser foil having bulk and / or surface scattering properties provided on the second side edge.

[0075] In best practice, the first TIR surface 111 and the second TIR surface 112 should be made smooth (or specular) and without any light extraction structures. For instance, the first TIR surface and the second TIR surface may each have an average roughness of Ra < 0.01 pm (or, more preferably, of Ra < 0.005 pm). In this way, the light emitted by the first light source 120 and output at the second side edge 114 can illuminate as far as expected, creating a large uniformly illuminated ceiling area.

[0076] The luminaire 100 illustrated in Figures 1 to 3 is configured to illuminate a target surface from one side of the luminaire (i.e. light output by the luminaire extends from the luminaire in one direction). The luminaire 100 is particularly suitable for illuminating long, narrow target surfaces; for instance, the luminaire 100 may be mounted on a short side wall of a long, narrow indoor space (such as a corridor or an aisle-shaped room), at a distance of at least 120 mm from a ceiling of the indoor space, in order to illuminate the ceiling. If the luminaire has a width of at least 20 mm and is mounted at a distance of at least 120 mm from a ceiling, the luminaire will illuminate an area of at least 2 m x 2 m of the ceiling with a uniformity better than 10: 1 (where the uniformity is a ratio of a greatest intensity to a lowest intensity in the 2 m x 2 m area, i.e. a brightest portion of the 2 m x 2 m area of the ceiling is no more than 10 times brighter than a least bright portion of the 2 m * 2 m area). As previously mentioned, the first light guide plate 110 and reflector 130 of the luminaire 100 illustrated in Figures 1 to 3 each have a rectangular shape. However, other shapes for the first light guide plate are also envisaged. The shape of the reflector may depend on the shape of the first light guide plate, such that the reflector extends by the same distance from the second side edge of the light guide plate (i.e. the edge from which light is output) throughout the length of the second side edge.

[0077] In some examples, a cut-out may be provided in the first light guide plate, and the first side edge may be an inner edge of the first light guide plate (i.e. an edge facing the cut-out), while the second side edge may be an outer edge of the first light guide plate. In other words, the first light source may be provided in the cut-out, and light may enter the first light guide plate from the cut-out and be directed away from the cut-out, exiting the first light guide plate at an outer edge. The cut-out may be centered with respect to the first light guide plate and have a same shape as the first light guide plate. The shape of the first light guide plate and cut-out may be circular, elliptical, or a shape formed from smoothly connected curves and / or lines (i.e. curves and / or lines connected such that adjacent curves / lines share a common tangent at the point of connection).

[0078] For instance, the first light guide plate may be an annular disc. Figure 4 illustrates a perspective view of a luminaire 200, according to another embodiment of the invention, in which the first light guide plate 210 is an annular disc. The luminaire 200 comprises a first light guide plate 210, a first light source and a reflector 230. The reflector 230 also has an annular shape.

[0079] In Figure 4, the luminaire 200 further comprises a plurality of mounting elements 250, configured to attach the luminaire to a base 260, for mounting the luminaire to a target surface (e.g. a ceiling). Each mounting element comprises a screw configured to be secured within a respective hole in the first light guide plate 210. Each mounting element is secured to the base 260 to provide a desired distance between the first light guide plate and the target surface to be illuminated (e.g. a distance of at least 120 mm).

[0080] Figure 5 illustrates a top view of the luminaire 200. For illustrative purposes, the mounting element and base are omitted from Figure 5. Figure 5 illustrates more clearly the placement of the first light source 220 with respect to the light guide plate 210. In Figure 5, the first light source comprises a plurality of light-emitting elements provided at regular intervals around the inner edge (i.e. the first side edge) of the annular first light guide plate 210. The first side edge may comprise one or more recesses configured to receive the light-emitting elements. As described above with reference to the luminaire 100 of Figures 1 to 3, the annular first light guide plate 210 comprises a first TIR surface and second TIR surface, with a first side edge (the inner edge of the annular first light guide plate) and a second side edge (the outer edge of the annular first light guide plate) each extending between the first and second TIR surfaces. The reflector 230 is provided on the first TIR surface of the first light guide plate, and extends away from the first light guide plate from the second side edge; in other words, the reflector extends radially outwards from the first light guide plate. As described above, the second side edge of the first light guide plate 210 may be slanted to face the reflector 230, and / or may have a diffuse finish.

[0081] Figure 6 illustrates a side view of the luminaire 200, showing the relationship between the dimensions of the luminaire 200. The dimensions of the luminaire may be described by Equation 1 : where P is an angle between the reflector 230 and a virtual line between a top of the outer edge of the first light guide plate 210 (i.e. a part of the second side edge furthest from the reflector), T is the thickness of the first light guide plate (i.e. a distance between the first TIR surface and the second TIR surface), A is the distance by which the reflector extends from a line between the reflector and the top of the outer edge of the first light guide plate that is perpendicular to the plane in which the reflector lies (i.e. the distance between an outer edge of the reflector and the top of the outer edge of the first light guide plate in the direction in which the reflector extends from the first light guide plate), H is a distance from the bottom of the luminaire 200 (i.e. from a surface of the reflector on an opposite side to the first light guide plate) to an expected eye level, and S is a distance from a point at expected eye level on the virtual line between the top of the outer edge of the first light guide plate and a point at expected eye level directly below the center of the luminaire 200. Although Figure 6 illustrates this relationship in the context of the luminaire 200 having an annular light guide plate, Equation 1 may be applied to any shape of light guide plate (e.g. to the luminaire 100 illustrated in Figures 1 to 3). In the case of an annular light guide plate (as shown in Figure 6), the distance A may also be expressed as half of the difference between the diameter of the reflector (i.e. a distance from one point on the outer edge to an opposite point on the outer edge) and the diameter of the first light guide plate (i.e. a distance from one point on the second side edge to an opposite point on the second side edge). The angle P may have a value in the range 18° < P < 25°; in other words, the thickness T of the first light guide plate and the size of reflector may be designed such that the ratio between T and A satisfies the condition tan 18° < T / A < tan 25°. Angles in this range have been found to reduce glare.

[0082] Such optical arrangement achieves an asymmetrical light output profile as shown in Figure 19. Light output from the luminaire 200 is a combination of light guided by the first light guide plate 210, with the first TIR surface and the second TIR surface, and light reflected by the reflector 230. In a preferably embodiment, the output beam is in the range of about -5° ~ +55°, among which about 95% light is projected to the target surface and about 5% is projected away from the target surface.

[0083] Figure 7 illustrates a perspective view of a luminaire 300, according to yet another embodiment of the invention. The luminaire 300 is similar to the luminaire 200 of Figures 4 to 6, but further comprises a second light guide plate 370 and a second light source, in order to provide downward as well as upward light. The second light source may comprise a plurality of light-emitting elements.

[0084] Figure 8 illustrates a cross-sectional view of a portion of the luminaire 300. The second light guide plate 370 is provided on an opposite side of the reflector 330 to the first light guide plate 310. The second light source 380 is provided at a first side edge of the second light guide plate, and is configured to emit light towards the first side edge of the second light guide plate, such that light emitted by the second light source enters the second light guide plate at the first side edge, and is output from a light output surface of the second light guide plate on an opposite side of the second light guide plate to the reflector. The light output surface may be provided with light extraction features (e.g. scattering roughness dots, surface structures, scattering paint dots, etc.) to facilitate light extraction by the light output surface. The surface of the second light guide plate opposite to the light output surface may be a TIR surface, to increase an amount of light output at the light output surface.

[0085] The first light source 320 and second light source 380 may be configured such that a luminous flux of the first light source is greater than a luminous flux of the second light source. In other words, an upward luminous flux of the luminaire may be greater than a downward luminous flux. In some examples, a ratio between the luminous flux of the first light source to the luminous flux of the second light source may be adjustable (i.e. by adjusting a driving current for the first light source and / or second light source).

[0086] In some examples, the first light source 320 and second light source 380 may be CCT tunable; i.e. each of the light source may comprise a first group of light-emitting elements having a first CCT and a second group of light-emitting elements having a second CCT. In some examples the first light source and second light source may be configured such that an adjustment to the CCT of the first light source results in a corresponding adjustment of the CCT of the second light source (i.e. such that the first and second light sources always have the same CCT).

[0087] In Figure 8, the luminaire 300 further comprises a diffuser 390 provided on the surface of the second light guide plate on the opposite side of the second light guide plate to the reflector (i.e. on the light output surface of the second light guide plate). This provides diffuse downwards light when the luminaire is mounted with the first light guide plate 310 facing a ceiling, thus reducing glare.

[0088] In Figure 8, the luminaire 300 further comprises a housing 340 configured to hold the first light guide plate 310, first light source 320, reflector 330, second light guide plate 370, second light source 380 and diffuser 390.

[0089] Figure 8 illustrates a cross-section of the luminaire 300 along a line passing through a threaded hole 355 in the first light guide plate 310 for attaching a mounting element 350. The threaded hole extends through the thickness of the first light guide plate and into the housing 430, enabling the mounting element to be secured to the housing.

[0090] In Figures 7 and 8, the first and second light guide plates each have an annular shape. However, second light guide plate and second light source, as described with reference to the luminaire 300 of Figures 7 and 8, may be provided with any shape of light guide plate. The second light guide plate may have a same shape as the first light guide plate.

[0091] Figures 9-11 illustrate a luminaire 400 comprises an optical module 445 which is movable along an axis AX. The luminaire 400 may be mounted on a target surface (wall or ceiling) 10. By rotating the lamp front panel 441, the distance between the light module 445 and the target surface 10 is controllable, by which the light pattern on the wall 10 can be changed to fit different application requirement.

[0092] Figure 10 illustrates sectional views of the inner structure of the luminaire 400 with its two configurations: left image shows that the optical module 445 is at its left-most position which is remote from the target surface 10; right image shows that the optical module 445 is at its right-most position which is adjacent to the target surface 10. The optical module 445 comprises a light guide plate 410 and a reflector 430 covering the light guide plate 410 at the side remote from the target surface 10. The reflector 430 extends away from the light guide plate 410 as the structure described in Figures 4-8. Figure 11 illustrates an explosive view of the luminaire 400. A front panel 441 and a rotor track 443 is assembled together to form a rotor sub-assembly 440. A stator housing 451, a stator track 453 and a stator bottom cover 455 form a stator sub-assembly 450. A driver 447 may be placed in the cavity of stator sub-assembly 450, and provide power to the optical module 445 via leaf springs 446. When the rotor sub-assembly 440 rotates with respect to the stator sub-assembly 450, the optical module 445 moves along the axis AX according to the principle of a cam, which transforms rotary motion into linear motion. The diameter of the front panel 441 is larger than that of the optical module 445 (in which the diameter of the reflector 430 is larger than that of the light guide plate 410), therefore, a person facing the luminaire 400 may see very few glares. And as shown in Figure 10, the light projection pattern 490 on the target surface 10 can vary along with the distance change between the optical module 445 and the target surface 10.

[0093] Figures 12-15 illustrates a luminaire 500, which reuses the plasterboard 10 of a false ceiling as a reflector and minimize the package size.

[0094] In Figure 12, the luminaire 500 is in a compact mode, fits to a minor package size, with all components stack together.

[0095] Figure 13 illustrates the main components of this luminaire 500: a pair of optical modules 501, four pieces of supports 505 and one driver 509. These components may be assembled as shown in Figures 14 and 15. The supports pieces 505 are connected to a frame 550 supporting the optical modules 501 at the opposite side of the frame 550. A piece of plasterboard 10 is fixed on top of the frame.

[0096] As shown in Figure 15, the bottom side of the plasterboard 10 has the same function the target surface 10 as described in above embodiments. It’s preferable that this bottom side has a scattering white finish (e.g., for high reflectivity with TiCh coating), so that it can also function as a reflector, adding an additional function to the luminaire 500 to make a whole as a troffer luminaire.

[0097] As shown in the enlarged view in Figure 15, the optical module 501 has the same structure as described in the embodiment of Figures 1-3. A light guide plate 510 is provided over a reflector 530, light emitted by a light source 520 enters the light guide plate 510 and leaves the light guide plate 510 from the side which the reflector 530 extends away from the light guide plate 510. With the troffer luminaire mounted on the false ceiling, a person standing on floor can hardly see any glare because of the extending reflector 530, as the light output from the light guide plate 510 is mostly reflected to the plasterboard 10 and is then reflected downwards (scatteringly). Figure 16 illustrates a side view of a luminaire 600 according to another embodiment of the invention, mounted at a corner of two intersecting walls 10-1, 10-2 (or ceiling 10-1 and wall 10-2). From the view of a person in the space, the glare is minimized.

[0098] As shown in the enlarged view of Figure 17, the luminaire 600 comprises two light guide plates 610-1 and 610-2, a shared light source 620, and two reflectors 630-1, 630-2. Each reflector covers one respective side of the light guide plates 610-1 and 610-2, and extends away from its respective light guide plate. Preferably, the light source 620 may be a linear light source, for example, an elongate LED filament. To improve the optical efficiency, the luminaire 600 may comprise a further reflector 650 covering outer surface of the light source 620 remote from the light guide plates. The light guide plates 610-1 and 610-2, the shared light source 620, the further reflector 650 and the two reflectors 630-1, 630-2 may be mounted on a L-shaped support 640.

[0099] As shown in Figure 18, the luminaire 600 may comprise more than two light guide plates, for example, three light guide plates 610-1, 610-2, 610-3. The shared light source 620 emits light into those light guide plates at the same time. There are three reflectors 630-1, 630-2, 630-3 covering one respective side of the light guide plates, and extends away from its respective light guide plate. The output light goes along the direction basically aligns with the respective reflector as shown as the dash-lined arrows. There may be even more light guide plates sharing a common light source 620, e.g., four to six.

[0100] As the skilled person will readily appreciate, any of the luminaires disclosed herein may further comprise one or more other elements, such as driving circuitry, control circuitry, communication circuitry, and so on.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A luminaire (100, 200, 300), comprising: a first light guide plate (110, 210, 310) comprising: a first total internal reflection, TIR, surface (111); a second TIR surface (112), wherein each TIR surface is an intact specular surface with no light extraction feature; a first side edge (113) extending between the first TIR surface and the second TIR surface as a light in-coupling port; and a second side edge (114) extending between the first TIR surface and the second TIR surface as a light out-coupling port; a first light source (120, 220, 320), provided at the first side edge of the first light guide plate and configured to emit light towards the first side edge, such that light emitted by the first light source enters the first light guide plate at the first side edge, and is output from the first light guide plate at a second side edge of the first light guide plate; and a reflector (130, 230, 330), provided on the first TIR surface and extending away from the first light guide plate from the second side edge; wherein both the first light guide plate and the reflector are flat and are parallel to each other.

2. The luminaire (100, 200, 300) of claim 1, wherein the second side edge (114) of the first light guide plate (110, 210, 310) has a diffuse finish.

3. The luminaire (100, 200, 300) of claim 2, wherein the second side edge (114) of the first light guide plate (110, 210, 310) has an average roughness in the range 0.8-3.0 pm.

4. The luminaire (100, 200, 300) of any of claims 1 to 3, wherein a recess is provided in the first side edge (113) of the first light guide plate (110, 210, 310) for the first light source.

5. The luminaire (100) of any of claims 1 to 4, wherein a quotient of a distance (X) by which the reflector (130) extends from the second side edge (114) and a thickness (T) of the first light guide plate (110) is at least 2.0, wherein the thickness of the first light guide plate is a distance between the first TIR surface (111) and the second TIR surface (112).

6. The luminaire (100) of claim 5, wherein the quotient of the distance (X) by which the reflector (130) extends from the second side edge (114) and the thickness (T) of the first light guide plate (110) is in the range 2.0-6.0.

7. The luminaire (100) of any of claims 1 to 6, wherein the first light guide plate (110) has a rectangular shape.

8. The luminaire (200, 300) of any of claims 1 to 7, wherein: a cut-out is provided in the first light guide plate (210, 310), wherein the cut-out is centered with respect to the first light guide plate and has a same shape as the first light guide plate; the first side edge of the first light guide plate is a side edge facing the cut-out; and the second side edge of the first light guide plate is an outer edge of the light guide plate.

9. The luminaire (200, 300) of claim 8, wherein the first light guide plate (210, 310) is an annular disc, wherein the first side edge is an inner edge of the annular disc and the second side edge is an outer edge of the annular disc.

10. The luminaire (100, 200, 300) of claim 9, wherein: the luminaire is adapted to be mounted such that a distance between the second TIR surface (112) of the first light guide plate (110, 210, 310) and a ceiling is at least 120 mm; a width of the first light guide plate is at least 20 mm; the first TIR surface and the second TIR surface each have an average roughness of Ra < 0.01 pm, such that an illuminated area of the ceiling of 2 m x 2 m around the luminaire has a maximum -to-minimum uniformity better than 10: 1.

11. The luminaire (300) of any of claims 1 to 10, further comprising: a second light guide plate (370), provided on an opposite side of the reflector (330) to the first light guide plate (310); and a second light source (380), provided at a first side edge of the second light guide plate and configured to emit light towards the first side edge of the second light guide plate, such that light emitted by the second light source enters the second light guide plate at the first side edge, and is output from a surface of the second light guide plate on an opposite side of the second light guide plate to the reflector.

12. The luminaire (300) of claim 11, further comprising a diffuser (390) provided on the opposite surface of the second light guide plate (370) to the reflector (330).

13. The luminaire (300) of claim 11 or 12, wherein the first light source (320) and the second light source (380) are configured such that a luminous flux of the first light source is greater than a luminous flux of the second light source.

14. The luminaire (200, 300) of any of claims 1 to 7, comprising a sub-assembly comprising the first light guide plate, the first light source and the reflector, wherein: the subassembly is moveable along an axis (AX) perpendicular to the first light guide plate.

15. The luminaire (200, 300) of any of claims 1 to 7, comprising two or more first light guide plates, wherein: the first light source (620) is shared with the first light guide plates.

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