Lighting device with rod-shaped light guide element

Abstract

A lighting device (100) comprising: a light emitting diode (LED) (110) light source arranged to emit LED light (111); a reflector (120); a rod-shaped light guide element (130) extending along the main axis A, where the light guide element is arranged between the LED light source and the reflector, and where a side surface (140) of the light guide element comprises a prismatic structure (150), a cross-section CS of the prismatic structure perpendicular to the main axis A comprising a zigzag profile (160) around a circumference of the light guide element, the prismatic structure has at least 10 vertices (170) extending in a radial direction Ra of the light guide element, whereby the vertices define an edge (180) of the prismatic structure extending parallel to the main axis A, and wherein the prismatic structure comprises a surface roughness SR.

Description

Technical Field

[0001] The present invention generally relates to lighting devices. In particular, the lighting device comprises a rod-shaped light-guiding element with optimized optical performance. Background Art

[0002] The field of lighting has experienced rapid development with the introduction of new technologies such as light emitting diodes (LEDs). The field is undergoing a transformation and continues to attract attention. Compared to traditional light sources such as incandescent lamps, fluorescent lamps, neon tube lamps, etc., devices or equipment including LEDs offer many advantages, such as increased flexibility and control, more compact design and / or reduced power consumption. In particular, traditional light sources are rapidly being replaced by LED-based lighting solutions.

[0003] It is further preferred that the LED lighting device provides light with desired properties, such as, for example, light uniformity, low glare, adequate color mixing, and high comfort for the observer.

[0004] Light guide systems and / or devices have been disclosed in the prior art to provide light guiding and color mixing effects. However, these light guide systems and / or devices usually have limited tolerance for the control of color mixing and light distribution. Therefore, due to (multiple) effects such as reflection and / or refraction, the light output from the light guide system and / or device may vary. This, in turn, may deteriorate the characteristics of the emitted light, such as, for example, poor light distribution, higher glare, insufficient color mixing, reduced comfort for the observer, etc. In addition, the attractiveness of the light guide system and / or device may be reduced as a result.

[0005] It is therefore an object of the present invention to provide an improved lighting device to alleviate these disadvantages. In particular, it is desirable to provide a lighting device that can provide good light uniformity, low glare, sufficient light mixing, so that the lighting device can provide the desired light emission with optimized optical performance. A filamentary appearance is also provided in the present invention. Summary of the invention

[0006] In view of the above, it is of interest to provide an alternative lighting device to improve its optical performance and lighting effect. These and other objects are achieved by providing a lighting device having the features of the independent claims. Preferred embodiments are defined in the dependent claims.

[0007] Therefore, according to one aspect of the present invention, a lighting device is provided. The lighting device comprises: a light emitting diode (LED) light source arranged to emit LED light; a reflector; a rod-shaped light guide element extending along a main axis A, the light guide element comprising a first end and a second end, wherein the light guide element is arranged between the LED light source and the reflector, wherein the LED light source is arranged at the first end and the reflector is arranged at the second end, and wherein a side surface of the light guide element comprises a prismatic structure, a cross section CS of the prismatic structure perpendicular to the main axis A comprises a sawtooth profile around the circumference of the light guide element, having a radial direction R of the light guide element. a At least 10 vertices extending upwardly from the main axis A, whereby the vertices define edges of the prismatic structure extending parallel to the main axis A, and wherein the prismatic surface comprises a surface roughness SR.

[0008] Therefore, the present invention is based on the idea of ​​providing a lighting device, wherein the side surface of a rod-shaped light-guiding element is provided with a prismatic structure extending along the main axis and comprising surface roughness. In other words, due to the characteristics of the lighting device, in particular the rod-shaped light-guiding element comprises, on its side surface, a prismatic structure whose cross section CS is perpendicular to the main axis A, the surface roughness of the prismatic structure destroys the total internal reflection TIR of part of the light emitted from the LED light source, which is coupled into the rod-shaped light-guiding element via TIR and transported through the rod-shaped light-guiding element, the lighting device is able to provide sufficient color mixing with a filamentary appearance and prevent glare originating from reflections at the interface between the reflector and the light-guiding element. By the term "light-guiding element", it is meant here essentially any element, material, structure, etc., which is arranged or configured to guide and / or reflect light emitted from the LED light source during operation.

[0009] The lighting device of the invention is further advantageous in that the prismatic structure comprises a sawtooth profile around the circumference of the light-guiding element, with a radial direction R of the light-guiding element. a At least 10 vertices extending upwardly from the main axis, whereby the vertices define edges of the prismatic structure extending parallel to the main axis. Due to this arrangement, the lighting device can provide a higher degree of TIR to improve color mixing.

[0010] According to an embodiment of the present invention, a ratio R of a length L of the light guide element along the main axis A to a diameter D of the cross section CS satisfies R=L / D≥4. Due to this arrangement, the lighting device can provide more adequate color mixing.

[0011] According to an embodiment of the present invention, the edge of the prism structure is rounded. Due to this arrangement, the manufacturability of the lighting device is improved.

[0012] According to an embodiment of the invention, the light guiding element comprises a groove at the second end towards the first end, and wherein the reflector is tapered and arranged to be at least partially recessed into the groove. Due to this arrangement, light uniformity is improved.

[0013] According to an embodiment of the present invention, the top angle θ of the conical reflector is in the range of 65° to 85°. Due to this arrangement, the present invention is further advantageous because the lighting device can provide uniform light distribution.

[0014] According to an embodiment of the invention, the number of vertices is in the range of 20 to 60. With this arrangement, color mixing is significantly improved.

[0015] According to an embodiment of the present invention, the roughness average value of the surface roughness is in the range of 0.16 μm to 0.64 μm. Due to this arrangement, the light uniformity and the filamentary appearance are further improved.

[0016] According to an embodiment of the present invention, at least a portion of the second end of the light guide element is not covered by the reflector, wherein a portion of the LED light in the range of 8% to 20% is output from the portion of the second end of the light guide element not covered by the reflector. Due to this arrangement, light uniformity is further improved.

[0017] According to an embodiment of the present invention, the light reflected from the reflector and output from the lighting device is in the range of 15% to 35% of the LED light. With this arrangement, the light uniformity is further improved.

[0018] According to an embodiment of the present invention, at least a portion of the LED light is coupled into the light guide element at the first end as coupled-in light, wherein the light guide element is configured to guide at least a portion of the coupled-in light as guided light to the second end based on total internal reflection TIR, wherein the reflector is arranged to reflect at least a portion of the guided light incident on the reflector, so that the reflected light is arranged to leave the lighting device. Due to this arrangement, light is output from most directions of the lighting device, thereby further improving light uniformity.

[0019] According to an embodiment of the present invention, the lighting device comprises an air gap between the second end of the light guide element and the reflector, wherein the light C reflected based on TIR at the interface between the air gap and the second end of the light guide element is in the range of 30% to 55% of the LED light. The present invention is further advantageous because the lighting device can provide a reliable and / or stable light output with uniform light distribution from the lighting device. Therefore, during operation, a more attractive light output is generated for an observer from the lighting device.

[0020] According to an embodiment of the present invention, 10% to 40% of the LED light is output through the side surface of the light guide element without being reflected by at least one of the reflector and the groove. Preferably, 15% to 28% of the LED light is output through the side surface of the light guide element without being reflected by at least one of the reflector and the groove. Thus, the lighting device can provide more optimized optical performance, such as light distribution with uniformity, lower glare and a filamentary appearance.

[0021] According to an embodiment of the present invention, the LED light source includes at least one first LED arranged to emit white light, at least one second LED arranged to emit red light, at least one third LED arranged to emit at least one of green light and yellow light, and at least one fourth LED arranged to emit blue light.

[0022] It will be appreciated that the lighting device of the present invention may be suitable for use in a variety of lighting equipment, lamps, etc. Thus, the lighting device may be beneficial in substantially any area for illumination purposes.

[0023] Therefore, according to another aspect of the present invention, a lamp is provided. The lamp comprises an envelope at least partially surrounding a lighting device according to any exemplary embodiment of the present invention and a base, wherein the base comprises a cover that mechanically and electrically connects the lighting device to a socket of the lamp. This embodiment is advantageous because the lamp including the lighting device has aesthetic appeal and provides light with desired properties, such as, for example, light uniformity, low glare, adequate color mixing, and high comfort for the observer.

[0024] Other objectives, features and advantages of the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims.Those skilled in the art will realize that different features of the present invention can be combined to create embodiments other than those described in the following. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] This and other aspects of the present invention will now be described in more detail, with reference to the accompanying drawings showing embodiment(s) of the invention.

[0026] Figure 1 Schematically shows a cross-sectional view of a part of a lighting device according to an exemplary embodiment of the present invention,

[0027] Figure 2 Schematically shows a cross-sectional view of a part of a lighting device according to an exemplary embodiment of the present invention,

[0028] Figure 3a , Figure 3b and Figure 3c Schematically shows a top view of a cross section of an illumination device according to an exemplary embodiment of the present invention,

[0029] Figure 4 schematically shows a detailed view of a portion of a prismatic structure of a lighting device including surface roughness according to an exemplary embodiment of the present invention, and

[0030] Figure 5 A view schematically illustrating an LED lamp including a lighting device according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0031] Figure 1 A cross-sectional view of a portion of an illumination device 100 according to an exemplary embodiment of the present invention is schematically shown. The illumination device 100 includes an LED light source 110 arranged to emit LED light. It is to be understood that the illumination device 100 may include substantially any number of LEDs of the LED light source 110. For example, the LEDs of the LED light source 110 may be aligned in a horizontal array. According to an alternative example, the LED light source 110 may include at least one first LED arranged to emit white light, wherein white light refers to light having a wavelength range of 400nm to 700nm. According to another alternative example, the LED light source 110 may include at least one second LED arranged to emit red light, wherein red light refers to light having a wavelength range of 450nm to 495nm. According to another alternative example, the LED light source 110 may include at least one third LED arranged to emit at least one of green light and yellow light, wherein green light refers to light having a wavelength range of 495nm to 570nm, and yellow light refers to light having a wavelength range of 570nm to 590nm. According to another alternative example, the LED light source 110 may include at least one fourth LED arranged to emit blue light, wherein blue light refers to light with a wavelength range of 620nm to 750nm. According to another alternative example, the correlated color temperature of the white light may be in the range of 2000K to 8000K. The color rendering index of the white light may be at least 80, in particular at least 85. At least one of these LEDs emitting different light may form the LED light source 110, or may be combined together to form the LED light source 110.

[0032] The lighting device 100 further includes a reflector 120, which is arranged to reflect at least a portion of the light incident thereon. The lighting device 100 further includes a rod-shaped light guide element 130, which is configured to guide the light emitted from the LED light source 110. The rod-shaped light guide element 130 may be solid or hollow. The light guide element 130 extends along the main axis A and includes a first end 131 and a second end 132. The light guide element 130 is arranged between the LED light source 110 and the reflector 120, wherein the LED light source 110 is arranged at the first end 131 and the reflector 120 is arranged at the second end 132.

[0033] According to some embodiments, when the lighting device 100 is in operation, at least a portion of the LED light is coupled into the light guide element 130 at the first end 131 as incoupled light, and the light guide element 130 is configured to guide at least a first portion of the incoupled light to the second end 132 as guided light 134 based on TIR, such as Figure 1 As shown in B and C in FIG. 1 , the reflector 120 is arranged to reflect at least a portion of the guided light 134 incident on the reflector 120, such as Figure 1 As shown in B in FIG. 1 , the reflected light is arranged to leave the lighting device 100. The lighting device 100 is also arranged to output at least a second portion of the coupled-in light through the side surface 140 of the light guide element 130, as shown in FIG. Figure 1 The lighting device 100 is also arranged to output at least a third portion of the incoupled light through a portion of the second end 132 of the light guide element 130, and ultimately emit the light from the top of the lighting device 100, as shown in FIG. Figure 1 As indicated by D in FIG.

[0034] According to the alternative example, Figure 1 As shown, Figure 1 The illustrated portion B of the LED light is reflected from the reflector 120 and is output from the lighting device 100 within a range of 15% to 35%, preferably 20% to 27%, of the LED light emitted from the LED light source 110 .

[0035] Further, according to an alternative example, the lighting device 100 includes an air gap (not shown in the drawings) between the second end 132 of the light guide element 130 and the reflector 120, such as Figure 1 As shown. Figure 1 As shown, the portion C of the LED light reflected based on TIR at the interface between the air gap and the second end 132 of the light guide element is in the range of 30% to 55% of the LED light, preferably in the range of 39% to 48% of the LED light.

[0036] Further, according to the alternative example, Figure 1 As shown, a portion of the LED light S is output through the side surface of the light guide element 130 without being reflected by the reflector 120 or the groove of the second end 132. Figure 2 The notch of the second end 132 is discussed in detail. The portion S of the LED light is in the range of 10% to 40% of the LED light, preferably in the range of 15% to 28% of the LED light.

[0037] Due to the specific prismatic structure of the lighting device 100 with surface roughness disclosed above, a uniform light distribution with low glare and adequate color mixing is obtained.

[0038] Figure 2A cross-sectional view of a portion of an illumination device 100 according to an exemplary embodiment of the present invention is schematically shown. Figure 1 , Figure 3a , Figure 3b and Figure 3c The following are set forth in the references provided therein. Figure 2 In the embodiment, the side surface 140 of the light guide element 130 includes a prism structure 150. The cross section CS of the prism structure 150 is perpendicular to the main axis A. According to an alternative example, Figure 2 combination Figure 1 , Figure 3a , Figure 3b and Figure 3c As shown, the light guide element 130 includes a groove at the second end toward the first end. The reflector 120 can be conical, such as Figure 3a and Figure 3b as shown, or can be multifaceted, such as Figure 3c According to another alternative example, the reflector 120 is conical and has a top angle θ in the range of 65° to 85°, preferably in the range of 70° to 80°, and more preferably 72°.

[0039] Figure 3a , Figure 3b and Figure 3c The top view of the cross section of the lighting device 100 according to an exemplary embodiment of the present invention is schematically shown. Figure 1 and Figure 2 The following contents are elaborated in the references provided therein. Figure 3a to Figure 3c As shown, the prismatic structure 150 comprises a sawtooth profile 160 around the circumference of the light guide element 130. The sawtooth profile 160 comprises at least 10 vertices 170, preferably 20 to 60 vertices 170. The vertices 170 are in the radial direction R of the light guide element 130. a The edge 180 extends parallel to the main axis A and defines an edge 180 of the prismatic structure 150. The edge 180 extends parallel to the main axis A.

[0040] like Figure 3a As shown, in some embodiments, the reflector 120 may be tapered and cover only a portion of the second end 132 of the light guide element 130. In this case, the reflector 120 may be translucent or opaque, and at least a portion of the second end 132 of the light guide element 130 is not covered by the reflector 120, thereby Figure 1The portion T of LED light shown is output from the portion of the second end 132 of the light guide element 130 that is not covered by the reflector 120. In some preferred examples, the portion T of light is in the range of 8% to 20%, preferably in the range of 11% to 15%. Figure 3b , the reflector 120 may also be tapered but cover the entire portion of the second end 132 of the light guide element 130. In this case, the reflector 120 may be arranged to be translucent so that a portion T of the LED light emitted from the LED light source 110 is output from the second end 132 of the light guide element 130 via the reflector 120. In some preferred examples, the portion T of the light is in the range of 8% to 20%, preferably 11% to 15%. A third embodiment of the reflector 120 may be Figure 3c As shown, the reflector 120 may be multi-faceted, and the reflector 120 may be arranged to be translucent so that a portion T of the LED light emitted from the LED light source 110 is output from the second end 132 of the light guide element 130 via the reflector 120. In some preferred examples, the portion T of the light is in the range of 8% to 20%, preferably 11% to 15%.

[0041] The above-mentioned special prism structure 150 provides a higher degree of TIR in the light guide element 130 to improve light mixing. According to some embodiments of the present invention, the prism structure 150 may also have a rounded edge 180 to improve the manufacturability of the light guide element 130. In order to further improve the color mixing effect, in some embodiments, the length L of the light guide element 130 along the main axis A and the diameter D of the cross section CS may have a ratio R that satisfies R=L / D≥4, in particular 15≥L / D≥4. The length L can be defined according to the specific application. In some alternative examples, the length L is in the range of 4 cm to 12 cm.

[0042] Figure 4 Schematically shows a detailed view of a portion of a prismatic structure of a lighting device 100 including a surface roughness SR according to an exemplary embodiment of the present invention. To provide a filamentary appearance, the prismatic structure 150 includes a surface roughness SR such as Figure 4 In some embodiments, the surface roughness SR has a roughness average in the range of 0.16 μm to 0.64 μm, preferably in the range of 0.3 μm to 0.5 μm. Since the surface roughness disrupts the TIR of part of the light source light coupled into the light guide element via TIR and transported through the light guide element, the filamentary appearance is obtained.

[0043] Figure 5 FIG. 1 schematically shows a view of an LED lamp 300 including the lighting device 100 according to an exemplary embodiment of the present invention. Figure 5In the example, LED lamp 300 includes an envelope 200 at least partially surrounding a lighting device according to an exemplary embodiment of the present invention and a base 301, wherein the base includes a cover 210 that mechanically and electrically connects the lighting device to a socket of a lamp.

[0044] Those skilled in the art realize that the present invention is by no means limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, one or more components of the lighting device 100 (such as the light guide element 130, the reflector 120, etc.) may have a shape, size and / or size different from that depicted / described.

Claims

1. A lighting device (100), comprising: a light emitting diode LED (110) light source arranged to emit LED light, A reflector (120), A rod-shaped light guide element (130) extending along a main axis A, the light guide element comprising a first end (131) and a second end (132), wherein the light guide element is arranged between the LED light source and the reflector, wherein the LED light source is arranged at the first end and the reflector is arranged at the second end, and wherein a side surface (140) of the light guide element comprises a prismatic structure (150), a cross section CS of the prismatic structure perpendicular to the main axis A comprising a sawtooth profile (160) around the circumference of the light guide element, the sawtooth profile having a radial direction R of the light guide element. a At least 10 vertices (170) extending upwardly from the main axis A, whereby the vertices define edges (180) of the prismatic structure extending parallel to the main axis A, wherein the prismatic structure comprises a surface roughness SR having a roughness average value in the range of 0.16 μm to 0.64 μm, and Wherein the light guiding element comprises a groove at the second end towards the first end, and wherein the reflector is tapered and arranged to be at least partially recessed into the groove. 2 . The lighting device according to claim 1 , wherein a ratio R of a length L of the light guide element along the main axis A to a diameter D of the cross section CS satisfies R=L / D≥4.

3. The lighting device according to claim 1 or 2, wherein the edges of the prismatic structures are rounded. 4 . The lighting device according to claim 1 , wherein a vertex angle θ of the conical reflector is in the range of 65° to 85°. 5 . The lighting device according to claim 1 , wherein the number of the vertices is in the range of 20 to 60.

6. A lighting device according to any of the preceding claims, wherein at least a portion of the second end of the light guiding element is not covered by the reflector, and wherein a portion D of the LED light in the range of 8% to 20% is output from the portion of the second end of the light guiding element not covered by the reflector.

7. The lighting device according to any one of the preceding claims, wherein the light B reflected from the reflector and output from the lighting device is in the range of 15% to 35% of the LED light.

8. A lighting device according to any of the preceding claims, wherein at least a portion of the LED light is coupled into the light-guiding element at the first end as coupled-in light, wherein the light-guiding element is configured to guide at least a portion of the coupled-in light as guided light (134) to the second end based on total internal reflection (TIR), wherein the reflector is arranged to reflect at least a portion of the guided light incident on the reflector so that the reflected light is arranged to leave the lighting device.

9. The lighting device according to any of the preceding claims, comprises an air gap between the second end of the light guide element and the reflector, wherein the light C reflected based on TIR at the interface between the air gap and the second end of the light guide element is in the range of 30% to 55% of the LED light.

10. The lighting device according to any one of the preceding claims, configured to output 10% to 40% of the LED light S through the side surface of the light guide element without being reflected by at least one of the reflector and the groove. 11 . The lighting device according to claim 10 , configured to output 15% to 28% of the LED light S through the side surface of the light guide element without being reflected by at least one of the reflector and the groove.

12. A lighting device according to any one of the preceding claims, wherein the LED light source comprises at least one first LED arranged to emit white light, at least one second LED arranged to emit red light, at least one third LED arranged to emit at least one of green light and yellow light, and at least one fourth LED arranged to emit blue light.

13. An LED lamp (300), comprising: The lighting device according to any one of the preceding claims, an envelope (200) at least partially surrounding the lighting device, and A base (301), wherein the base comprises a cover (210) arranged to mechanically and electrically connect the lighting device to a socket of a lamp.

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