Abstract
A method is provided, wherein a lighting device (200, 300, 400, 500) comprising an at least partly light transmitting envelope (110) and a solid state light source (120) is manufactured. The method comprises arranging (710) an at least partly light transmitting plastic material (140) in a mold (130) having a surface structure (132) arranged on an inner surface portion of the mold and blow molding (720) the plastic material so as to form the envelope. During the blow molding, the surface structure is at least partly transferred to the at least partly light transmitting plastic material, thereby forming an optical structure (150) on a portion of an outer surface of the envelope. The envelope is then removed (730) from the mold and arranged (740) to at least partly enclose the solid state light source. The optical structure may be formed to generate a desired optical effect.
Claims
1-14. (canceled)
15. A method for manufacturing a lighting device comprising an at least partly light transmitting envelope and a solid state light source, said method comprising: arranging an at least partly light transmitting plastic material in a mold having a surface structure arranged on an inner surface portion of the mold, blow molding the plastic material so as to form the at least partly light transmitting envelope, the surface structure being at least partly transferred to the at least partly light transmitting plastic material to form an optical structure on a portion of an outer surface of the at least partly light transmitting envelope, removing the at least partly light transmitting envelope from said mold, and arranging the at least partly light transmitting envelope to at least partly enclose the solid state light source, arranging a light refracting lens in an optical path of the lighting device to focus a visual pattern in the far field, wherein said visual pattern is formed of light being diffracted by the optical structure.
16. The method according to claim 15, wherein the at least partly light transmitting envelope is shaped like a bulb or a tube.
17. The method according to claim 15, wherein the optical structure comprises at least one of grooves, protrusions, micro grooves, micro protrusions, micro prismatic protrusions, a lens, a Fresnel lens and a diffraction grating.
18. The lighting device according to claim 15, wherein the optical structure is adapted to diffract light exiting the at least partly light transmitting envelope such that a visual pattern is formed in the far field and/or in the near field.
19. The lighting device according to claim 15, wherein the optical structure is adapted to diffract light exiting the at least partly light transmitting envelope so as to provide a predetermined color distribution.
20. The lighting device according to claim 15, wherein the optical structure is adapted to diffract and/or refract light exiting the at least partly light transmitting envelope so as to provide a predetermined angle distribution of said light.
21. The lighting device according to claim 15, wherein the optical structure is adapted to form a visual pattern at the outer surface portion of the at least partly light transmitting envelope, and/or adapted to diffract light from the solid state light source such that a visual pattern is formed at the outer surface portion of the at least partly light transmitting envelope.
22. The lighting device according to claim 15, wherein the optical structure is arranged to reflect light back into an interior of the at least partly light transmitting envelope.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] These and other aspects will now be described in more detail with reference to the appended drawings showing embodiments of the present invention.
[0034] FIG. 1 shows a prior art incandescent lamp.
[0035] FIG. 2a shows a three-dimensional side view of a lighting device according to an embodiment.
[0036] FIGS. 2b and c show cross-sectional top views of a lighting device similar to the one shown in FIG. 2a.
[0037] FIG. 2d shows a cross-section of a lighting device according to another embodiment.
[0038] FIG. 2e illustrates different examples of illumination patterns according to an embodiment.
[0039] FIG. 3 shows a three-dimensional side view of a lighting device according to an embodiment.
[0040] FIG. 4a shows a three-dimensional side view of a lighting device according to another embodiment.
[0041] FIG. 4b shows a cross-sectional side view of a portion of the envelope of the lighting device in FIG. 4a.
[0042] FIG. 4c shows a three-dimensional side view of a lighting device similarly configured as the lighting device shown in FIG. 4a.
[0043] FIGS. 5a and b show a three-dimensional side view and a cross sectional top view, respectively, of a lighting device according to an embodiment.
[0044] FIGS. 6a to c schematically illustrate a blow molding process according to an embodiment.
[0045] FIG. 7 is a flow chart illustrating a method for manufacturing a lighting device according to an embodiment.
[0046] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the embodiments, wherein other parts may be omitted or merely suggested. Like reference numerals refer to like elements throughout the description.
DETAILED DESCRIPTION
[0047] The present aspects will now be described more fully hereinafter with reference to the accompanying drawing, in which currently preferred embodiments are shown. The 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 fully convey the scope of the present aspects to the skilled person.
[0048] FIG. 1 illustrate an incandescent lamp known in the prior art. The lamp comprises a glass bulb 1 enclosing a low pressure inert gas 2 such as argon, nitrogen, krypton or xenon, and a tungsten filament 3 arranged on a glass stem 7 by means of electrically insulated support wires 6. The tungsten filament 3 is electrically connected to a contact wire 4 that goes out of the stem 7, through a cap or sleeve 9 and to an electrical terminal or contact 11. The filament 3 is also connected to another contact wire 5 that goes into the stem 7 and to the cap 9. The cap 9 and the contact 11 are electrically insulated from each other by means of an electrical insulation 10, such as vitrite.
[0049] FIGS. 2a-d illustrate lighting devices 200 according to some embodiments of the present invention. In line with the present embodiment, the lighting device comprises an at least partly light transmitting envelope 110 and a solid state light source 120. The envelope 110 may also be referred to as a bulb 110 and may be arranged to at least partly enclose the solid state light source 120. The bulb 110 according to the present embodiment provides optical effects such as collimation, and may improve the light output of the bulb 110 to be more uniform. The light source 120 may be formed as a LED chimney 120 which is a set of LED modules wrapped around a central cylinder, or cylindrical holding member 122 having an axial extension along an optical axis O of the lighting device. Such light source 120 may leave a black spot at the top of the chimney 120, or the top of the bulb 110. Further, an optical structure 150 may be formed on a portion of an outer surface of the envelope 110. The optical structure 150 may e.g. be formed during manufacturing of the envelope 110, such as during a blow molding process of the envelope 110. The optical structure 150 may e.g. be formed by a surface structure arranged on an inner surface portion of a mold (not shown in FIG. 2a) used in the blow molding process. Such optical structure 150 may alleviate at least some of the issues of light distribution from the bulb.
[0050] According to some embodiments, such as shown in FIG. 2a, the optical structure 150 may comprise grooves in a bottom part of the bulb housing, i.e. the portion of the housing closest to a socket 160 of the lighting device 100. The grooves 151 may e.g. be micro- or nano-grooves 151 and may be lengthwise oriented from south to north (should the lighting device 100 be standing in a vertical direction, i.e. the optical axis O being aligned with a vertical direction), i.e. along the optical axis O, or the optical path of the lighting device 100, and in a direction away from the socket 160. Micro-grooves should be understood as grooves having an average depth in the range of 1-1000 m, whereas nano-grooves refer to grooves having an average depth of less than 1 m. The grooves 151 may e.g. be arranged on a lower or bottom half of the envelope 110.
[0051] Turning now to FIG. 2b, which shows a cross-sectional top view of the lighting device of FIG. 2a, an example of micro-prismatic grooves 151 is shown. Micro-prismatic grooves may e.g. be provided with a peak 152 with a top angle of approximately 90 and a feature size or valley 153 depth of 10-100 micrometers, such as 25-100 micrometers. Such micro-prismatic grooves 151 may act efficiently as total internal reflection mirrors adapted to reflect impinging light (represented by arrows in FIG. 2b). This may provide a collimating reflector without the use of light reflecting metal coatings.
[0052] Turning back to FIG. 2a, such collimating effect can be achieved with the envelope 110 and the optical structure 150 according to the present embodiment. Light emitted by the LEDs 120 may be reflected at the optical structure 150, redirected upwards, in a direction away from the socket 160, and emitted from the lighting device 200 through the upper or north portion of the at least partly light transmitting envelope 110. Light emitted from mainly side-emitting light sources 120 may therefore be redirected so as to provide a mainly top-emitting lighting device 200. It will however be appreciated that the optical structure 150 may be configured such that at least some light exits the envelope 110 through the optical structure 150. The amount of light exiting through the optical structure 150 may e.g. depend on the angle of incidence, wherein total internal reflection e.g. may occur for light impinging at an angle of incidence exceeding a critical angle of the optical structure 150. Additionally, external focusing lens 170 is provided which is arranged to be external to (and separate from) the bulb 110 and to project an image of the logo 154 on e.g. a wall or surface.
[0053] FIG. 2c is a cross-section of a similar lighting device as that described with reference to FIGS. 2a and b, wherein the optical structure 150 comprises a nano-structure which may be arranged to reflect and/or to diffuse light emitted by the light source 120. The nano-structure 150 may e.g. have an average feature size of less than 1 micrometer.
[0054] FIG. 2d shows a lighting device 200 similarly configured as the lighting device described with reference to FIGS. 2a and b. However, the optical structure 150, which may comprise grooves or micro-grooves, may be arranged in the top or north part of the bulb housing, oriented from east to west so as to form concentric circles or a spiral having a centre coinciding with the optical axis O of the lighting device 200. The micro-prismatic grooves 151 may e.g. be provided with a peak or sharp corner having a top angle of approximately 90 and a feature size or valley depth of 10-100 micrometers, thereby allowing light emitted by the light source 120 to be reflected and the resulting light beam to be reshaped or redirected.
[0055] The embodiments described with reference to FIGS. 2a-d thereby allow for beam shaping, wherein grooves 151, such as e.g. micro-grooves, in the top or bottom part of the bulb housing 110 may be arranged to redirect the emitted light. An emission pattern of a LED source, directed north, can e.g. be steered to go partially south, thereby being more compliant with requirements relating to energy saving. At least some problems associated with beam shaping of light from an incandescent replacement LED-bulb can hence be addressed. Effects associated with the beam shaping can for instance include collimation effects, lensing effects (Fresnel) or scattering.
[0056] In FIG. 2e, two examples of such emission patterns are illustrated. The emission pattern of the light source 120 is represented by arrows inscribed in an area 10 defined by a solid line. The arrows indicate the different directions in which light is emitted from the light source 120, in this example along the optical axis O, i.e. directed north, and in directions ranging between the optical axis and a lateral axis L being orthogonal to the optical axis. The length of the arrows, or the distance from the enclosing line and origo, indicates the relative amount of light emitted in that direction. The longer arrow, the more light may be emitted in that direction.
[0057] The dotted line 20 illustrates the emission pattern of a lighting device according to FIGS. 2a and b, wherein the optical structure 150 may be arranged in the bottom part of the bulb 110. As shown in FIG. 2e, the emission pattern may be redirected upwards such that a lighting device having a top-lighting character may be provided.
[0058] Further, the dashed line 30 illustrates the emission pattern of a lighting device according to FIG. 2d wherein the optical structure 150 may be arranged in the top part of the bulb 110 so as to increase the amount of light being emitted in lateral and downward directions.
[0059] FIG. 3 illustrates a lighting device 300 according to an embodiment, which may be similarly configured as the lighting devices described with reference to FIGS. 2a-d. The present embodiment however differs in that the optical structure 150 may be introduced to stamp a visual pattern, such as a trademark 154 on the outer surface of the bulb 110. The light scattering properties can be made different for the logo 154 and the rest of the bulb 110 surface. This makes the logo 154 visible in the OFF-state of the lighting device 300, thereby allowing for a potential buyer or user to inspect the logo 154 under e.g. ambient light to verify that the lighting device 300 is a genuine product and not a counterfeit one. However, in the ON-state the light emitted from the lighting device 300 may dazzle the eye of the observing buyer or user. In such case, the logo 154 may be made visible with the aid of an external focusing lens 170, which is arranged to be external to (and separate from) the bulb 110 and to project an image of the logo 154 on e.g. a wall or surface. The observer may then inspect the projected logo 154 to verify authenticity of the product.
[0060] FIG. 4a-c show a lighting device 400 according to an embodiment similar to the embodiments as described in connection with FIGS. 2 and 3. According to this embodiment, the optical structure 150 comprises concentric diffraction gratings or rings 155 that e.g. may be embossed in the bulb 110 and designed in such a way that a colored spot appears in the far field or at a specific distance of e.g. 20-30 cm. The grating pitch may depend on the angle of incidence of the LED light. FIG. 4b shows a cross sectional portion of the envelope 110, wherein light may be emitted from the light source 120 and diffracted by the grating rings 155 arranged at the surface of the envelope and at different incident angles as seen from the light source 120. In this example, an outer one of the grating rings 155 may be configured to diffract light such that a blue spot may be generated in the focal point f.sub.B of the outer grating ring. Further, a green spot may be generated in the focal point f.sub.G of a middle grating ring, and a red spot in the focal point f.sub.R of an inner grating ring. Each colored spots may e.g. appear at different distances from the lighting device 400.
[0061] FIG. 4c shows an example wherein the diffractive grating may be configured to generate a green colored spot in the far field, whereby the grating pitch of three concentric grating rings arranged in a plane orthogonal to the optical axis O may be chosen as 635 nm/855 nm/1610 nm for the grating rings that are at an angle of incidence of 60/40/20, respectively. As shown by the arrows in FIG. 4c, the green light may be diffracted by each one of the grating rings and exit the envelope 110 in a direction parallel to the optical axis, wherein the remaining light continues in another direction. It will however be appreciated that the optical structure 150 or grating may be adapted to generate further colors, such as blue and green, as indicated in FIG. 4c.
[0062] FIGS. 5a and b illustrate a lighting device 500 according to an embodiment similarly configured as the embodiments described with reference to FIGS. 2-4. According to the present embodiment, the optical structure 150 comprises decorative patterns, such as patches of Fresnel lenses or other structures which may create a pattern in far field. The size, orientation and position of the patches or regions provided with the optical structure may be adapted depending on the desired result or optical effect. As shown by the cross section of FIG. 5b, the optical structure 150 may also be configured to focus light at a certain point or distance from the lighting device 500.
[0063] FIGS. 6a-c illustrate a blow molding process according to an embodiment of the present invention. The mold 130 has a surface structure 132 arranged on an inner surface portion of the mold 130. The mold 130 comprises two parts 137, 139 that can be joined during the blow molding process and disjoined so as to allow for the blow molded envelope 110 to be removed from the mold. In FIG. 6a, an at least partly light transmitting plastic material 140, which may be arranged on a blowing rod 135, has been introduced in the mold 130. In FIG. 6b, the plastic material 140 has been expanded by e.g. air, supplied by the blowing rod 135, such that the plastic material 140 forms a thin plastic layer that may be pressed against the inner surface of the mold 130 and hence against the surface structure 132. The surface structure 132, which may comprise both extrusions and indentations, hence forms an imprint or embossing in an outer surface of the plastic layer, thereby transferring the surface structure 132 of the mold 140 into an optical structure 150 at the resulting envelope 110. As shown in FIG. 6c, the mold 130 may be disjoined, the blowing rod 135 retracted and the blow molded envelope 110 removed.
[0064] FIG. 7 schematically illustrates a method according to an embodiment of the present invention. The method comprises: [0065] arranging 710 a plastic material 140 in a mold 130 having a surface structure 132 arranged on an inner surface portion of the mold 130; [0066] blow molding 720 the plastic material 140 so as to form the envelope 110, the surface structure being at least partly transferred to the plastic material 140 to form an optical structure 150 on a portion of an outer surface of the envelope 110; [0067] removing 730 the envelope 110 from the mold 130; [0068] arranging 740 the envelope 110 to at least partly enclose a solid state light source 120; and optionally [0069] arranging a light refracting lens 750 in an optical path of the lighting device 100 to focus a visual pattern in the far field, wherein the visual pattern may be formed of light being diffracted by the optical structure 150.
[0070] Thus, the present invention provides a lighting device, which may comprise an at least partly light transmitting envelope and a solid state light source. The envelope may be blow molded and provided with an optical structure that may be transferred to a surface of the envelope from a mold used during a blow molding process. The optical structure may e.g. be a diffractive or refractive optical structure and designed for providing optical effects such as collimation, scattering, lensing, various watermarking or trademarking optical effects, and far field and near field effects.
[0071] The person skilled in the art realizes that the present invention by no means is limited to the embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. By means of the above-described lighting device, the envelope, even if referred to as a bulb, may be formed into almost any form capable of transmitting light and at least partly enclose a light source. Further, the blow molding technique could also be used according to some embodiments of the invention to provide a tube for tube lighting (TL), or any other type of luminaire requiring a shaped envelope or bulb. Additionally, 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. Any reference signs in the claims should not be construed as limiting the scope.
