Optical element for lighting system providing enhanced brightness uniformity

Abstract

The invention relates to an elongate optical element (1) for a lighting system (100) having a longitudinal extension and a transverse extension substantially perpendicular to the longitudinal extension. The optical element (1) has a central portion (2) with a first edge (2 ') and a second edge (2' ') arranged substantially parallel to each other and parallel to a longitudinal extension of the optical element (1). The optical element (1) further comprises a first light guide (3) arranged at least at a first edge (2 ') of the central portion (2), the optical element (1) having a first surface (4) facing at least one light source (112) of the lighting system (100) and a second surface (4') opposite the first surface (4), the first surface (4) of the first light guide (3) comprising at least one longitudinal saw tooth (5) extending substantially parallel to the longitudinal direction of the optical element (1).

Description

Technical Field

[0001] The invention relates to an optical element for an illumination system, an illumination system comprising such an optical element and an illumination device comprising such an illumination system. Background Art

[0002] Office lamps have strongly opposing requirements. In particular, office compliance lamps are required to have limited light distribution with UGR ≤ 19.0 and low diffuse light above 65 degrees (L65 ≤ 3000 cd / m 2 ). On the other hand, customers prefer office luminaires with maximum brightness uniformity, which means that the cover should be as diffuse as possible.

[0003] All of these above requirements can be met by currently available optical systems consisting of an MLO cover and a diffuse foil (e.g. FlexBlendMLO) or a diffuse reflector (e.g. SmartBalance). However, such solutions are costly (expensive MLO cut from a sheet must be fixed using additional elements) and inefficient, especially in luminaires with a small exit window (e.g. FlexBlend MLO – LOR = 65%).

[0004] There are more cost-effective luminaires such as KeyLine PCS or FlexBlend PCS, where the PCS cover, a hexagonal structure with a sphere radius of 2.3 mm, is used together with a lens inside the luminaire. Both the cover and the lens are molded, so it is cost-effective and easy to assemble. This optical system is highly efficient (80-86%) and meets office compliance requirements, but the brightness with the exit window is highly non-uniform.

[0005] In view of the foregoing, there exists a need to provide an improved track lighting system that exhibits uniform brightness while being cost-effective and easy to assemble.

[0006] DE202016002197U1 discloses a direct-emitting LED lamp with an anti-glare effect. Summary of the invention

[0007] It is an object of the present invention to overcome or at least alleviate the above mentioned problems and to provide an improved lighting system.

[0008] To this end, the invention provides an elongated optical element for a lighting system, having a longitudinal extension and a width as a transverse extension, which is substantially perpendicular to the longitudinal extension. The longitudinal extension of the optical element depends on the intended use and can be from 1 cm to 100 m. The transverse extension of the optical element can be from 5 mm to 30 cm. The optical element according to the invention can be a diffuser. The term "substantially" used in the context of this specification is intended to mean "consistent with or slightly deviating from".

[0009] The optical element of the invention further comprises a central portion having a first edge and a second edge, the first edge and the second edge being arranged substantially parallel to each other and to the longitudinal extension of the optical element. The lateral extension of the central portion of the optical element may be 10% to 90% of the lateral extension of the optical element. The central portion of the optical element is arranged to be placed in a position such that it covers the light source of the track lighting system.

[0010] The optical element according to the invention further comprises at least a first light guide, which is arranged at a first edge of the central part. The first light guide may be aligned with the light source of the track lighting system in a lateral direction. The first light guide may be attached to the first edge of the central part by means of a fastening element, such as an adhesive, a clamp, a screw or the like. Alternatively, the first light guide may be an integral part of the optical element, i.e. the first light guide and the central part may be manufactured as a single piece. In particular, the first light guide and the central part may be molded together by one tool in one processing step. In such an embodiment, the first light guide and the central part are manufactured from the same material.

[0011] The optical element according to the invention has a first surface facing at least one light source of a track lighting system and a second surface opposite to the first surface. The first surface of the first light guide comprises at least one longitudinal jag, which is substantially parallel to the longitudinal extension of the optical element. The optical element further comprises a plurality of first light guides spaced apart along the first edge of the central portion.

[0012] Therefore, the essence of the present invention is to provide an additional apparent light source so that the light beam emitted from the light source is reflected by the longitudinal serrations, thereby improving the brightness uniformity by illuminating the dark parts of the light pattern that may otherwise be formed.

[0013] The optical element may further comprise a second light guide arranged on a second edge of the central part. Such an embodiment provides the advantage of a symmetrical light pattern. The second light guide may be aligned in a lateral direction with the light source of the illumination system and / or with the first light guide. The second light guide may be attached to the second edge of the central part by means of an adhesive or by any other suitable means. Alternatively, the second light guide may be an integral part of the optical element, i.e. the second light guide and the central part may be manufactured as a single piece.

[0014] In an embodiment not claimed, the first and / or second light guide may be continuous and may have a longitudinal extension substantially equal in length to the longitudinal extension of the optical element. In other words, the first and / or second light guide may extend along the entire first and / or second edge of the central portion, respectively.

[0015] The invention will essentially only be discussed with respect to track lighting systems, but is therefore applicable to other types of (linear) lighting systems comprising elongated optical elements, such as TLEDs.

[0016] As stated above, the optical element comprises a plurality of first light guides spaced apart along a first edge of the central portion. Thus, the amount of light guided in the longitudinal direction of the optical element is minimized and thus the likelihood of meeting higher requirements for office compliance parameters (such as UGR, L65) in the longitudinal direction is enhanced. When there are a plurality of first light guides, each first light guide may be aligned in a transverse direction with a light source of the lighting system. Similarly, the optical element may comprise a plurality of second light guides spaced apart along a second edge of the central portion. When there are a plurality of second light guides, each second light guide may be aligned in a transverse direction with a light source of the lighting system. Furthermore, each second light guide may be aligned with the first light guide.

[0017] The second light guide may comprise longitudinal serrations arranged on the first surface of the second light guide.The longitudinal extension of the serrations may be substantially equal in length to the length of the longitudinal extension of the first and / or second light guide.

[0018] The longitudinal serrations provided on the first surface of the first and / or second light guide may be in the form of grooves.The depth of the grooves may be adapted to the intended use but should be sufficient to allow reflection of light emitted by the light source.

[0019] Alternatively, the longitudinal serrations may be formed between a riser portion and a tread portion of the step. In such an embodiment, the light beam is reflected by the riser portion.

[0020] The elongated optical element according to the invention may comprise at least one lens plate arranged along a central portion of the optical element. The lens plate is arranged to cover the light sources of the illumination system. Preferably, the number of lens plates is equal to the number of light sources.

[0021] The optical element may comprise at least one collimator arranged adjacent to the at least one lens plate at the first surface of the optical element in a central portion of the optical element. Such an embodiment provides the advantage of providing a parallel light beam through the light guide, thereby improving the control of the light beam once it reaches the light guide edge and / or the longitudinal serrations.

[0022] The angle between the first and / or second light guide and the central portion of the optical element may be from 90° to 180°.

[0023] The present invention relates to a lighting system, such as a track lighting system, comprising a (track) substrate having a longitudinal extension, a first edge and a second edge extending substantially parallel to the longitudinal extension and spaced apart in a lateral direction substantially perpendicular to the longitudinal extension. The substrate has a first width W1 between the first edge and the second edge. In other words, the substrate can be in the form of an elongated strip of material. The substrate can be flexible or rigid. The substrate can be made of any suitable material, such as polymethyl methacrylate (PMMA) or polycarbonate (PC). The length and width W1 of the substrate can be adapted to the desired use of the lighting system. Typically, the length of the substrate is much greater than the width W1 of the substrate. For example, the length of the substrate can be from 5 cm to 5 m. The width W1 of the substrate can be from 1 cm to 10 cm.

[0024] The lighting system further comprises at least one printed circuit board (PCB) arranged on the substrate, and the printed circuit board (PCB) comprises at least one light source. The at least one PCB has a second width W2 in a direction substantially perpendicular to the longitudinal extension (L) of the substrate. The term "arranged on" is understood to mean that the substrate and the PCB are arranged to be in direct or indirect contact with each other. In other words, the PCB may be in close proximity to the substrate. Alternatively, there may be an additional layer between the substrate and the PCB, for example in the form of a thin plastic sheet with high reflectivity. The first width W1 may be greater than the second width W2. In other words, a portion of the substrate may be detached from the PCB. In particular, W2 may be less than 100 mm, preferably less than 60 mm, more preferably less than 40 mm.

[0025] The PCB may be arranged symmetrically with respect to the central longitudinal axis of the substrate, such that the distance between the first edge portion and the PCB is equal to the distance between the second edge portion and the PCB. Alternatively, the PCB may be arranged asymmetrically with respect to the central longitudinal axis of the substrate. The lighting system may include one PCB having a length substantially equal to the length of the substrate. Alternatively, the lighting system may have a plurality of PCBs arranged along the longitudinal extension of the substrate. In such an embodiment, the length of each of the PCBs is shorter than the length of the substrate.

[0026] The lighting system according to the present invention may include a plurality of light sources. In such an embodiment, each of the plurality of light sources may be covered by a common lens plate or by a separate lens plate. Typically, the lens plate has a length of 280 mm (1 ft) and covers 20-24 LEDs. Alternatively, the number of light sources in the plurality of light sources is equal to the number of lens plates in the plurality of lens plates.

[0027] The plurality of light sources and the plurality of lens plates may be arranged in a linear array. The array may be a rectilinear (straight) array. In another embodiment, the linear array is curved in a plane perpendicular to the optical axis of the lens plates.

[0028] The lighting system comprises an optical element as described above. The optical element is arranged downstream from at least one light source. Finally, the lighting system also comprises a cover arranged downstream from the optical element. In the context of the present invention, the term "downstream" is intended to represent a continuous order in the direction of the light path. Finally, the lighting system comprises a cover arranged downstream from at least one diffuser. The cover may be an optical cover, which may be made of polycarbonate (PC). The cover may be transparent or diffuse. In addition, the cover may be flat or may include an optical structure in order to provide a proper light distribution and improve the uniformity of the light exit window so that the light exit window is perceived as uniformly illuminated.

[0029] The optical element may have a width Wo extending in the transverse direction. In particular, the width Wo of the optical element may be greater than the second width W2 of the PCB. Such an embodiment provides the advantage of improving brightness uniformity.

[0030] Finally, the invention relates to a lighting device comprising a lighting system as described above. The lighting system may be a track lighting system. The lighting device may be a track lighting device, comprising a track lighting system, a (track) luminaire, in particular an office (track) luminaire.

[0031] It is noted that the invention relates to all possible combinations of features recited in the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

[0033] Figure 1a and 1b depicts a perspective view of an optical element according to an unclaimed embodiment of the present invention;

[0034] Figure 2a Pictured Figure 1a and 1b as well as Figure 4a -c is a cross section of the optical element shown;

[0035] Figure 2b shows a cross section of an optical element according to another embodiment of the present invention;

[0036] Figure 3a and 3b depicts a brightness pattern provided by a track lighting system according to the present invention;

[0037] Figure 4a-4cA perspective view of an optical element according to yet another embodiment of the present invention is illustrated;

[0038] Figure 5 Depicted Figure 4a-4c The brightness pattern provided by the optical element shown in ;

[0039] FIG. 6 a illustrates a brightness pattern provided by a track lighting system according to the prior art (ie without any optical elements), and

[0040] Figure 6b Brightness patterns provided by a track lighting system having an optical element according to the present invention are respectively illustrated.

[0041] Like reference numerals refer to like elements throughout. DETAILED DESCRIPTION

[0042] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness and to fully convey the scope of the invention to the skilled person. In the drawings, the present invention will be discussed primarily in the context of track lighting devices, but should be considered generally applicable to other (linear) lighting devices comprising at least one elongated optical element.

[0043] Figure 1a and 1b A top view and a bottom view are depicted, respectively, of the elongated optical element 1. The elongated optical element 1 has a longitudinal extension L and a lateral extension T substantially perpendicular thereto. Figure 1a and 1b The optical element 1 shown in the figure further comprises a central portion 2 having a first edge 2′ and a second edge 2″ arranged substantially parallel to each other and to the longitudinal extension L of the optical element 1. The central portion 2 of the optical element 1 is arranged to be placed in a position such that it covers the light source of the illumination system 100, as shown in FIG. Figure 2a can be seen in.

[0044] The optical element according to the present invention further comprises a first light guide 3 arranged at a first edge 2' of the central part 2 and a second light guide 3' arranged at a second edge 2" of the central part 2. The first and second light guides 3, 3' may be aligned with the light source of the illumination system in a transverse direction T. The first and second light guides 3, 3' are integral parts of the optical element 1, i.e. the first and second light guides 3, 3' and the central part 2 are manufactured as a single piece.

[0045] Figure 1aThe optical element 1 shown in the figure has a first surface 4 facing at least one light source of the illumination system 100 and a second surface 4' opposite to the first surface 4. The first surface 4 of the first light guide 3 comprises longitudinal serrations 5 which are substantially parallel to the longitudinal extension L of the optical element 1. The second surface 4' of the second light guide 3' comprises longitudinal serrations 5' which are substantially parallel to the longitudinal extension L of the optical element 1. Figure 1a , 1b The longitudinal serrations 5, 5' depicted in Figures 2a and 2a are in the form of grooves.

[0046] The lighting system 100 comprises a substrate 110 having a longitudinal extension, a first edge 110' and a second edge 110". extending substantially parallel to the longitudinal extension and spaced apart in a lateral direction substantially perpendicular to the longitudinal extension. The substrate 110 has a first width W1 between the first edge 110' and the second edge 110". In other words, the substrate 110 is in the form of an elongated material strip.

[0047] The lighting system further includes at least one PCB 111 arranged on the substrate 110 and including at least one light source 112. The at least one PCB 111 has a second width W2 in a direction substantially perpendicular to a longitudinal extension (L) of the substrate 110. The first width W1 is greater than the second width W2.

[0048] The PCB 111 is arranged symmetrically with respect to the central longitudinal axis 8 of the substrate 110 such that the distance between the first edge portion 110 ′ and the PCB is equal to the distance between the second edge portion 110 ″ and the PCB.

[0049] The optical element 1 has a width Wo extending in the transverse direction. Figure 2a As can be seen in FIG. 1 , the width Wo of the optical element 1 is greater than the second width W2 of the PCB 111. The cover 113 is arranged downstream from the optical element 1.

[0050] Therefore, the essence of the present invention is to provide an additional apparent light source so that the light beam emitted from the light source is reflected by the longitudinal serrations, thereby improving the brightness uniformity by illuminating the dark parts of the light pattern that may otherwise be formed.

[0051] The optical element 1 further comprises a second light guide 3' arranged on a second edge 2" of the central part 2. Such an embodiment provides the advantage of a symmetrical light pattern. The second light guide 3' may be aligned in a lateral direction with a light source of the illumination system 100 and / or with the first light guide 3. The second light guide 3' may be attached to a second edge 2" of the central part 2. Similar to the first light guide 3, the second light guide 3' may be an integral part of the optical element 1, i.e. the second light guide 3' and the central part 2 may be manufactured as a single piece.

[0052] Figure 1a and 1b The first and second light guides 3, 3' depicted in are non-claimed embodiments, which are continuous and have a longitudinal extension that is substantially equal in length to the longitudinal extension of the optical element 1. In other words, the first and second light guides 3, 3' extend along the entire first and second edges 2', 2" of the central portion 2, respectively.

[0053] Figure 3a Describes how Figure 2a The brightness pattern of the track lighting system 100 obtained by the embodiment shown in FIG. 6A has a viewing angle of 0° to the left and 30° to the right. As can be seen, the brightness pattern is improved compared to the brightness pattern provided by the track lighting system according to the prior art shown in FIG. 6A .

[0054] Figure 2b The cross section of an optical element 101 according to another embodiment of the present invention is shown. The structure of the optical element 101 is similar to that of the optical element 1. The longitudinal serrations 105, 105' are in the form of steps and are provided at the first surface 104 (opposite to the second surface 104') of the first light guide 103 and the second light guide 103' connected to the central portion 102. Figure 3b Describes how Figure 2b The brightness patterns of the track lighting system 1001 including the optical element 101 obtained in the embodiment shown in FIG. 1 have viewing angles of 0° to the left and 30° to the right.

[0055] As described above, the optical element 201 may include a plurality of first light guides 203 spaced apart along a first edge 202' of the central portion 202. Such an embodiment minimizes the amount of light guided in the longitudinal direction of the optical element 201. When there are a plurality of first light guides 203, each first light guide 203 may be aligned in a lateral direction with a light source of the track lighting system 2001. The optical element 201 also includes a plurality of second light guides 203' spaced apart along a second edge 202" of the central portion 202. When there are a plurality of second light guides 203', each second light guide 203' is aligned in a lateral direction with a light source of the track lighting system 2001. Furthermore, each second light guide 203' is aligned with the first light guide 203.

[0056] Each of the first light guides 203 and each of the second light guides 203' comprises a longitudinal serration 205, 205' arranged on the first surface 204. The longitudinal extension of the serration 205, 205' is substantially equal in length to the length of the longitudinal extension of the first and second light guides 203, 203'. The longitudinal serration 205, 205' provided on the first surface 204 of the first and second light guides 203, 203' is in the form of grooves. The depth of the grooves 205, 205' should be sufficient to allow reflection of light emitted by the light source, such as Figure 5 As shown in .

[0057] like Figure 4a As shown in FIG. 2 , an elongated optical element according to the present invention comprises a plurality of lens plates 206 arranged along a central portion 202 of the optical element 201. The lens plates 206 are arranged to cover the light sources of the track lighting system 2001. Preferably, the number of lens plates 206 is equal to the number of light sources.

[0058] like Figure 4b As shown in FIG. , the optical element 201 includes a plurality of collimators 207, which are arranged adjacent to the lens plate 206 at the first surface 204 of the optical element 201 in the central portion 202 of the optical element 201. Figure 4c Shows Figure 4b Detailed view of the . Figure 5 and 6b Depicted Figure 4a-4b From these figures it is apparent that the brightness pattern is improved compared to the brightness pattern shown in FIG6 a provided by a track lighting system of the prior art.

[0059] The skilled person realizes that the present invention is in no way limited to the preferred embodiments described above. Additionally, variations of the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention by studying the drawings, the present 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.

Claims

1. An elongated optical element (1) for an illumination system (100), having a longitudinal extension (L) and a width (Wo) as a transverse extension (T), the transverse extension (T) being substantially perpendicular to the longitudinal extension, the optical element (1) having a central portion (2), the central portion (2) having a first edge (2') and a second edge (2"), the first edge (2') and the second edge (2") being arranged substantially parallel to each other and to the longitudinal extension of the optical element (1), the optical element (1) further comprising a first light guide (3) arranged at least at the first edge (2') of the central portion (2), the optical element (1) having a first surface (4) facing at least one light source (112) of the illumination system (100) and a second surface (4') opposite to the first surface (4), wherein the first surface (4) of the first light guide (3) comprises at least one longitudinal serration (5), the longitudinal serration (5) being substantially parallel to the longitudinal extension of the optical element (1), The optical element (1, 201) comprises a plurality of first light guides (203) spaced apart along the first edge (202') of the central portion (202).

2. An elongated optical element (1) according to claim 1, wherein the optical element (1) further comprises a second light guide (3') arranged on the second edge (2") of the central portion (2).

3. The elongated optical element (1) according to claim 2, wherein the second light guide (3') comprises longitudinal serrations (5') arranged on the first surface (4) of the second light guide (3').

4. An elongated optical element (1) according to any one of the preceding claims, wherein the serrations (5) are in the form of grooves.

5. The elongated optical element (101) according to any one of claims 1 to 3, wherein the serrations (105) are formed between the facade portion and the tread portion of the step.

6. The elongated optical element (1) according to any of the preceding claims, wherein the longitudinal extension of the saw teeth (5) is substantially equal in length to the length of the longitudinal extension of the optical element (1).

7. An elongated optical element (1) according to any one of the preceding claims, wherein the optical element (1) comprises at least one lens plate (6) arranged along the central portion (2) of the optical element (1).

8. An elongated optical element (201) according to claim 7, wherein the optical element (201) comprises at least one collimator (207), which is arranged adjacent to the at least one lens plate (206) at the first surface (204) of the optical element (201) in the central part (202) of the optical element (201).

9. An elongated optical element (1) according to any one of the preceding claims, wherein the optical element (1) is a diffuser.

10. The elongated optical element (1) according to any of the preceding claims, wherein the angle between the first and / or the second light guide (3, 3') and the central portion (2) of the optical element (1) is from 90° to 180°.

11. A lighting system (100), comprising: a substrate (110) having a longitudinal extension (L), a first edge (110') and a second edge (110"), the first edge (110') and the second edge (110") extending substantially parallel to the longitudinal extension (L) and spaced apart in a transverse direction substantially perpendicular to the longitudinal extension (L), the substrate (110) having a first width W1 between the first edge (110') and the second edge (110"); at least one printed circuit board (PCB, 111) arranged on the substrate (110) and comprising at least one light source (112); the at least one PCB (111) having a second width W2 in a direction substantially perpendicular to the longitudinal extension (L) of the substrate (110), The optical element (1) according to any one of claims 1 to 10, which is arranged downstream from the at least one light source (112); A cover (113) is arranged downstream from the optical element (1).

12. The lighting system (100) according to claim 11, wherein the lighting system is a track lighting system.

13. A lighting device, comprising the lighting system (100) according to any one of claims 11-12.

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