WO2014118426A1

WO2014118426A1 - A light guide

Info

Publication number: WO2014118426A1
Application number: PCT/FI2014/050021
Authority: WO
Inventors: Petri Laukkanen
Original assignee: Ledil Oy
Priority date: 2013-02-01
Filing date: 2014-01-14
Publication date: 2014-08-07
Also published as: EP2951493A1

Abstract

A light guide (201) comprising a transparent element (202) is presented. The transparent element comprises an optically active section (203) forming a cavity for a light source and shaped to modify the light distribution pattern of the light source, and at least one channel (205) beginning from the cavity. Each channel comprises a punctureable sheet (210) of the transparent material closing the channel so that puncturing the punctureable sheet opens, through the channel, a passage between the cavity and ambient of the light guide. When the sheet is left intact, i.e. not punctured, the above-described light guide is suitable for applications where hermetic sealing of the cavity is needed. On the other hand, by puncturing the sheet, the light guide can be made suitable for applications where pressure balancing and/or ventilation of the cavity are/is needed.

Description

A light guide

Field of the invention

The invention relates generally to illuminating engineering. More particularly, the invention relates to a light guide for modifying a light distribution pattern of a light source that can be, for example but not necessarily, a light emitting diode "LED". Furthermore, the invention relates to a method for assembling an illuminator device.

Background Distribution of light produced by a light source can be important or even critical in some applications. The light source can be, for example but not necessarily, a light emitting diode "LED", a filament lamp, or a gas-discharge lamp. Figures 1 a and 1 b illustrate an exemplifying light guide 101 according to the prior art for modifying a light distribution pattern of a light source 106. Figure 1 b shows a view of a section taken along the line A - A shown in figure 1 a. The light guide 101 comprises a transparent element 102 made of transparent material having the refractive index greater than unity. The transparent element 102 comprises an optically active section 103 forming a cavity 104 for the light source 106 and shaped to modify the light distribution pattern of the light source. Some of the light beams radiated by the light source 106 are depicted with dot-and-dash line arrows in figures 1 a and 1 b. The transparent element 102 comprises a collar section 107 surrounding the optically active section 103. The transparent element 102 is pressed against a flat surface of a substrate element 108 with the aid of a support frame 109. The flat surface of the substrate element 108 is parallel with the xy-plane of a coordinate system 199. Electrical wires connected to the light source 106 are not shown in figures 1 a and 1 b. The transparent element 102 is shaped to provide passages between the cavity 104 and the ambient of the light guide. The passages are illustrated with dashed lines 130 in figure 1 b. The passages are needed, for example, in illumination systems where the light source 106 generates so much heat that pressure balancing of the cavity 104 is needed. It is also possible that there is a need for providing ventilation of the cavity 104. In conjunction with some illumination systems there can be, however, different needs so that the cavity has to be hermetically sealed from the ambient of the light guide. The ambient may contain, for example, such gases which should not get in contact with the light source. Therefore, in some cases there is a need for light guides such that pressure balancing and/or ventilation of the cavity can be arranged whereas, in some other cases, there can be a need for light guides such that the cavity can be hermetically sealed.

Summary The following presents a simplified summary in order to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

In accordance with the invention, there is provided a new light guide for modifying the light distribution pattern of a light source. The modification of the light distribution pattern can be based on reflection and/or refracting of light. A light guide ac- cording to the invention comprises a transparent element made of transparent material having refractive index greater than unity, the transparent element comprising:

- an optically active section forming a cavity for the light source and shaped to modify the light distribution pattern of the light source, and - at least one channel beginning from the cavity and comprising a puncturea- ble sheet of the transparent material closing the channel so that puncturing the punctureable sheet opens, through the channel, a passage between the cavity and the ambient of the light guide. When the sheet is left intact, i.e. not punctured, the above-described light guide is suitable for applications where hermetic sealing of the cavity is needed. On the other hand, by puncturing the sheet, the light guide can be made suitable for applications where pressure balancing and/or ventilation of the cavity are/is needed. Furthermore, the channel can be used as a passage for electrical wires of the light source when the sheet is punctured. Thus, the same light guide can be used in different applications having different needs.

In accordance with the invention, there is provided also a new illuminator device comprising at least one light source and at least one light guide according to the invention. The at least one light source may comprise, for example, one or more light emitting diodes "LED".

In accordance with the invention, there is provided also a new mold having a form suitable for manufacturing, by mold casting, the above-mentioned transparent element of the light guide according to the invention. In accordance with the invention, there is provided also a new method for assembling an illuminator device. The method comprises puncturing the punctureable sheet of the light guide according to the invention.

A number of exemplifying and non-limiting embodiments of the invention are described in accompanied dependent claims. Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in connection with the accompanying drawings. The verbs "to comprise" and "to include" are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Brief description of the figures

The exemplifying and non-limiting embodiments of the invention and their advantages are explained in greater detail below with reference to the accompanying drawings, in which: figures 1 a and 1 b illustrate an exemplifying light guide according to the prior art, figures 2a, 2b, 2c and 2d illustrate a light guide according to an exemplifying embodiment of the invention, figures 3a, 3b and 3c illustrate a light guide according to an exemplifying embodiment of the invention, figure 4 illustrates a light guide according to an exemplifying embodiment of the invention, figure 5 illustrates a light guide according to an exemplifying embodiment of the invention, figures 6a and 6b illustrate an illuminator device according to an exemplifying em- bodiment of the invention, and figure 7 illustrates a method according to an exemplifying embodiment of the invention for assembling an illuminator device.

Figures 1 a and 1 b have already been explained in the Background-section of this document. Description of exemplifying embodiments

Figures 2a, 2b, 2c and 2d illustrate a light guide 201 according to an exemplifying embodiment of the invention for modifying the light distribution pattern of a light source 206. Figure 2b shows a view of a section taken along the line A - A shown in figure 2a. The section shown in figure 2b has been taken along a section plane parallel to xz-plane of a coordinate system 299. Figure 2c shows a magnification of portion 231 of figure 2b, and figure 2d shows a corresponding magnification. The light guide 201 comprises a transparent element 202 made of transparent ma- terial having the refractive index greater than unity. The transparent material can be, for example, acrylic plastic, polycarbonate, optical silicone, or glass. The method of manufacture of the transparent element 202 can be for example mold casting. The transparent element 202 comprises an optically active section 203 forming a cavity 204 for the light source 206 and shaped to modify the light distribution pattern of the light source. The light source 206 can be, for example but not necessarily, a light emitting diode "LED", a filament lamp, or a gas-discharge lamp. Some of the light beams radiated by the light source 206 are depicted with dot- and-dash line arrows in figures 2a and 2b. The transparent element 202 comprises a collar section 207 surrounding the optically active section 203. The transparent element 202 is pressed against a flat surface of a substrate element 208 with the aid of a support frame 209. The flat surface of the substrate element 208 is parallel with the xy-plane of the coordinate system 299. Electrical wires connected to the light source 206 are not shown in figures 2a and 2b. The transparent element 202 comprises a channel 205 beginning from the cavity 204 and comprising a punctureable sheet 210 of the transparent material closing the channel so that puncturing the punctureable sheet opens, through the channel, a passage between the cavity 204 and the ambient 232 of the light guide. Figure 2c shows a situation where the sheet 210 is intact, i.e. not punctured, and thus the light guide is suitable for applications where hermetic sealing of the cavity 204 is needed. Figure 2d shows a situation where the sheet 210 has been punctured and thus the light guide is suitable for applications where pressure balancing of the cavity is needed. Furthermore, the channel can be used as a passage for electrical wires of the light source when the sheet is punctured. Thus, the light guide illus- trated in figures 2a-2d can be used in different applications having different needs. In figure 2d, the passage between the cavity 204 and the ambient of the light guide is illustrated with a dashed line 230. The thickness T of the sheet 210 can be, for example, at most 5 %, or at most 10 % of the length of the channel 205, where the length is measured from a point 250 to a point 251 along the dashed line 230. In some applications, the transparent element 202 is advantageously flexible material such as e.g. optical silicone. When the transparent material is flexible, a hole made using e.g. a needle to the sheet 210 gets substantially closed due to the flexibility after the needle has been removed from the hole. Thus, the punctured sheet 210 allows pressure balancing of the cavity 204 but prevents external impurities from getting into the cavity. Furthermore, when the channel 205 is used as a passage for electrical wires, the flexible sheet provides sealing of the lead-in of the wires.

The light guide 201 has a front face comprising an outer surface of the optically active section 203 and the front surface of the collar section 207. The light guide 201 comprises a back face comprising a recess portion constituting the cavity 204 and the back surface of the collar section 207. In the situation shown in figured 2a- 2d, the back face is pressed against the flat surface of the substrate element 208. A part of the channel 205 is formed by a groove on the back face. The groove extends from the recess portion, i.e. from the cavity 204, to an end-point 252 of the groove, and the punctureable sheet 210 is between the front face and the groove. The punctureable sheet 210 is constituted by the transparent material between the front face and the end point 252 of the groove so that the thickness of the transparent material between the front face and the bottom of the groove is at its smallest in the punctureable sheet 210 as illustrated in figures 2c and 2d.

Figures 3a, 3b and 3c illustrate a light guide 301 according to an exemplifying embodiment of the invention for modifying the light distribution pattern of a light source. Figure 3b shows a view of a section taken along the line A - A shown in figures 3a and 3c. The section shown in figure 3b has been taken along a section plane parallel to xz-plane of a coordinate system 399. The light guide 301 comprises a transparent element 302 made of transparent material having the refractive index greater than unity. The transparent element 302 comprises an optically active section 303 forming a cavity 304 for a light source and shaped to modify the light distribution pattern of the light source. The transparent element 302 comprises a collar section 307 surrounding the optically active section 303. The light guide 301 has a front face comprising an outer surface of the optically active section 303 and the front surface of the collar section 307. The light guide 301 comprises a back face comprising a recess portion constituting the cavity 304 and the back surface of the collar section 307. The transparent element 302 comprises a chan- nel 305 beginning from the cavity 304 and comprising a punctureable sheet 310 of the transparent material.

The collar section 307 comprises a first sealing ridge 31 1 on the front face of the transparent element 302. The first sealing ridge 31 1 is shown in figures 3a and 3b. The first sealing ridge 31 1 forms a closed path surrounding the optically active section 303. The collar section 307 comprises a second sealing ridge 312 on the back face of the transparent element: The second sealing ridge 312 is shown in figures 3b and 3c. The second sealing ridge 312 forms a closed path surrounding the cavity 304. The first and second sealing ridges provide sealing when the collar section 307 is pressed between external elements. The external elements can be, for example, such as the substrate element 208 and the support frame 209 shown in figures 2a and 2b. The punctureable sheet 310 is outside the closed path formed by the first sealing ridge 31 1 and inside the closed path formed by the second sealing ridge 312 as illustrated in figures 3a and 3c. Thus, when the punc- tureable sheet 310 is intact, i.e. not punctured, the cavity 304 can be tightly sealed by pressing the back face of the transparent element 302 against a flat surface of an external element.

It is also possible that there is only the first sealing ridge 31 1 on the front face and no sealing ridge on the back face, or only the second sealing ridge 312 on the back face and no sealing ridge on the front face. It is also possible that the first sealing ridge and/or the second sealing ridge are/is strips made of different material than the transparent element 302. When the transparent element 302 is made of material that is too hard for providing sealing, it might be advantageous to have sealing strips made of softer material on the front face and/or on the back face. Furthermore, when the transparent element 302 is sufficiently soft for providing sealing, it is possible that there are sealing ridges on one or both of the surfaces of external elements between which the collar section 307 is pressed. Furthermore, it is also possible that there are sealing ridges on one or both sides of the collar section 307 and, in addition, on one or both of the surfaces between which the collar section 307 is pressed. It is also possible to have a flat layer of sealing material between the collar section 307 and one or both of the surfaces between which the collar section 307 is pressed. Figure 4 illustrates a light guide 401 according to an exemplifying embodiment of the invention. The light guide 401 is otherwise similar to the light guide 301 illustrated in figures 3a-3c but the light guide comprises more than one channel. The light guide 401 comprises channels 405a, 405b, 405c, 405d and 405e that com- prise punctureable sheets 410a, 410b, 410c, 41 Od and 41 Oe, respectively. Puncturing the punctureable sheets 410a-410e of the channels 405a-405e makes the channels suitable for ventilating the cavity 404. The efficiency of the ventilation depends, however, on the cross-sectional areas of the channels and on the sizes of holes made to the punctureable sheets. The principle based on the punctureable sheet is applicable also in conjunction with light guides different from those illustrated above with the aid of figures 2a-2d, 3a-3c, and 4. Figure 5 shows a section view of a light guide 501 according to an exemplifying embodiment of the invention for modifying the light distribution pattern of a light source 506. The light guide comprises transparent elements 502 and 542 made of transparent material having refractive index greater than unity. The transparent elements comprise optically active sections 503 and 543 forming a cavity 504 for the light source 506 and shaped to modify the light distribution pattern of the light source. The transparent element 502 comprises a channel 505 beginning from the cavity and comprising a punctureable sheet 510 of the trans- parent material closing the channel. The thickness T of the punctureable sheet is smaller than the length of the channel L, and puncturing the punctureable sheet opens, through the channel, a passage between the cavity 504 and the ambient of the light guide. The thickness T of the punctureable sheet can be, for example, at most 50 %, or at most 10 %, or at most 5 % of the length L of the channel 505. Figures 6a and 6b illustrate an illuminator device according to an exemplifying embodiment of the invention. Figure 6a shows a view of a section taken along the line A - A shown in figure 6b. The section shown in figure 6a has been taken along a section plane parallel to the xz-plane of a coordinate system 699. The illuminator device comprises light sources and light guides 601 a, 601 b, 601 c and 601 d. Two of the light sources are denoted with reference numbers 606a and 606b. Each of the light guides is according to an exemplifying embodiment of the invention. Each of the light sources may comprise at least one light emitting diode "LED". In the exemplifying case illustrated in figures 6a and 6b, the light guides 601 a-601 d are parts of a single piece 614 of transparent material. The piece 614 is pressed against a substrate element 608 with a support frame 609. The piece is provided with channels 605a, 605b, 605c, and 605d which provide passages be- tween cavities of the light guides and a punctureable sheet 610. When the sheet 610 is left intact, i.e. not punctured, the illuminator device is suitable for applications where hermetic sealing of the cavities is needed. On the other hand, by puncturing the sheet, pressure balancing of the cavities can be achieved. Therefore, the punctureable sheet 610 has been punctured in illuminator devices ac- cording to some exemplifying embodiments of the invention, whereas the punctureable sheet 610 is intact in illuminator devices according to some other exemplifying embodiments of the invention.

Figure 7 illustrates a method according to an exemplifying embodiment of the invention for assembling an illuminator device. The method comprises, in phase 701 , puncturing a punctureable sheet of a light guide of the illuminator device, wherein the light guide comprises a transparent element made of transparent material having the refractive index greater than unity and the transparent element comprises:

- an optically active section forming a cavity for a light source and shaped to modify the light distribution pattern of the light source, and

- at least one channel beginning from the cavity and comprising the punctureable sheet so that the puncturing the punctureable sheet opens, through the channel, a passage between the cavity and the ambient of the light guide. The specific examples provided in the description given above should not be construed as limiting the scope and/or the applicability of the appended claims. In the above-presented examples, the light guide comprises only transparent material. However, in some cases, the light guide may comprise also parts made of non- transparent material such as, for example, parts for providing mechanical support to a light source.

Claims

What is claimed is:

1 . A light guide (201 , 301 , 401 , 501 , 601 a-601 d) for modifying a light distribution pattern of a light source, the light guide comprising a transparent element (202, 302, 502) made of transparent material having refractive index greater than unity and the transparent element comprising:

- an optically active section (203, 303, 503) forming a cavity (204, 304, 404, 504) for the light source and shaped to modify the light distribution pattern of the light source, and

- at least one channel (205, 305, 405a-405e, 505, 605a) beginning from the cavity, characterized in that the channel comprises a punctureable sheet (210, 310, 410a-410e, 510, 610) of the transparent material closing the channel, the thickness of the punctureable sheet being smaller than a length of the channel, and a passage between the cavity and ambient of the light guide being arranged to be opened through the channel in response to puncturing the punctureable sheet.

2. A light guide according to claim 1 , wherein the transparent element comprises two or more channels (405a-405e) each having the punctureable sheet (410a- 41 Oe), the channels being arranged to become suitable for ventilating the cavity in response to puncturing the punctureable sheets of the channels.

3. A light guide according to claim 1 or 2, wherein the transparent element comprises a front face comprising an outer surface of the optically active section (203, 303, 503) and a back face comprising a recess portion constituting the cavity (204, 304, 404).

4. A light guide according to claim 3, wherein each channel (205, 305, 405a- 405e) comprises a groove on the back face so that the groove extends from the recess portion to an end-point (252) of the groove and the punctureable sheet (210, 310, 410a-410e) is between the front face and a bottom of the groove, the groove and a surface of an external element forming a part of a tubular passage when the back face is pressed against the external element.

5. A light guide according to claim 4, wherein the punctureable sheet (210, 310, 410a-410e) is constituted by the transparent material between the front face and the bottom of the end point of the groove, thickness of the transparent material between the front face and the bottom of the groove being at its smallest in the punctureable sheet.

6. A light guide according to claim 4 or 5, wherein the transparent element (202, 302, 402) comprises a collar section (207, 307, 407) surrounding the optically active section (203, 303, 503), and the collar section comprises a first sealing ridge (31 1 ) on the front face of the transparent element and forming a closed path sur- rounding the optically active section and a second sealing ridge (312) on the back face of the transparent element and forming a closed path surrounding the recess portion, the first and second sealing ridges providing sealing when the collar section is pressed between external elements.

7. A light guide according to claim 6, wherein the punctureable sheet (310) is outside the closed path formed by the first sealing ridge (31 1 ) and inside the closed path formed by the second sealing ridge (312).

8. A light guide according to any of claims 1 -7, wherein the thickness (T) of the punctureable sheet is at most 50 % of the length (L) of the channel.

9. A light guide according to any of claims 1 -7, wherein the thickness of the punctureable sheet is at most 10 % of the length of the channel.

10. A light guide according to claims 1 -7, wherein the thickness of the punctureable sheet is at most 5 % of the length of the channel.

1 1 . A light guide according to any of claims 1 -10, wherein the transparent material is one of the following: acrylic plastic, polycarbonate, optical silicone.

12. An illuminator device comprising at least one light guide (601 a-601 d) according to any of claims 1 -1 1 and at least one light source (606a, 606b) at the cavity of each light guide.

13. An illuminator device according to claim 12, wherein the illuminator device comprises a plurality of light guides (601 a-601 d) according to any of claims 1 -1 1 and a plurality of light sources, the light guides being parts of a single piece (614) of the transparent material.

14. A mold having a form suitable for manufacturing, by mold casting, the transparent element of a light guide according to any of claims 1 -1 1 .

15. A method for assembling an illuminator device, characterized in that the method comprises puncturing (701 ) a punctureable sheet of a light guide of the illuminator device, the light guide comprising a transparent element made of trans- parent material having refractive index greater than unity and the transparent element comprising:

- at least one channel beginning from the cavity and comprising the punc- tureable sheet so that puncturing the punctureable sheet opens, through the channel, a passage between the cavity and the ambient of the light guide.