Lighting device and method for making a lighting device

Abstract

The present invention relates to a light guide for a lighting device. The invention offers the advantage that the lighting device provides both a decorative appearance and functional illumination, in addition to being energy efficient.

Description

FIELD OF THE INVENTION

[0001] The present invention generally relates to the field of lighting devices. The present invention relates to the use of a light guide in a lighting device.BACKGROUND OF THE INVENTION

[0002] Traditional incandescent light bulbs are available in various designs such as plain functional bulbs with different glass finishes (e.g. transparent, diffuse or colored) and decorative bulbs with complex filaments, wherein the filament itself serves a decorative purpose. However, due to demands on power saving in lighting devices, driven by eco awareness and legislation, traditional incandescent light bulbs are being replaced by more power efficient light sources such as fluorescent lamps and LED (light emitting diode) lamps. Such conventional eco-friendly lamps do not provide the same various designs as traditional incandescent light bulbs.

[0003] A solution of how to provide a lighting device resembling a carbon filament lamp is disclosed in WO 2006 / 035349. The document shows a lighting device comprising a solid state light source optically coupled to an optical fiber having an out-coupling surface. A drawback with such a lighting device is that it does not provide a sufficiently energy-efficient functional lighting (such as e.g. general lighting or task lighting).

[0004] WO 2006 / 081707 A1 describes a type of hose lamp comprising a rectangular bar-shaped body extruded from flexible plastic, which is provided with a longitudinal rectangular through-hole. At least two copper strands are arranged longitudinally in the side wall of the strip. A plurality of flexible strip-shaped circuit boards, each with at least one LED light-emitting body, are disposed in the through-hole, with conductive pin wires electrically connecting the circuit boards to the copper strands. The hose lamp further includes a diffusing body for diffusing the light of the LED light emitters and a coating layer, which is a flexible plastic extrusion covering the strip, the diffuser, and the LED luminous bodies. The coating layer above the LEDs forms a semicircular curved surface to simulate a neon tubular light emitting surface. The structure enables the hose lamp to emit continuous, uniform, and soft light, and allows bending along various surfaces.

[0005] US 6,580,228 B1 describes a lamp for use in a conventional line current powered incandescent lamp socket, comprising a base adapted to electrically and mechanically engage the socket, a power supply, and a flexible substrate on which a plurality of solid-state light sources are mounted in a spaced-apart array. The flexible substrate may be configured as a generally rectangular panel formed into a cylindrical shape or as a flexible substrate strand wound in a helix around a cylindrical support. The lamp further includes a light transmissive envelope attached to the base, enclosing the flexible substrate and the plurality of solid-state light sources. The power supply provides an appropriate voltage and current to energize the light sources, so that light is emitted radially outward around the lamp.SUMMARY OF THE INVENTION

[0006] Thus, there is a need for providing alternatives and / or new devices that would overcome, or at least alleviate or mitigate, at least some of the above mentioned drawbacks. It is with respect to the above considerations that the present invention has been made. An object of the present invention is to provide an improved alternative to the above mentioned technique and prior art.

[0007] More specifically, it is an object of the present invention to provide a lighting device enabling both decorative lighting and functional lighting with improved efficiency.

[0008] This object of the present invention is achieved by the features defined in the independent claim. . Preferable embodiments of the invention are characterized by the dependent claims.

[0009] Hence according to an aspect of the invention, use of a light guide in a lighting device is provided, the lighting device resembling a traditional incandescent light bulb and enabling both decorative lighting and functional lighting, wherein the light guide is in the form of a continuous optical element in which a string of a plurality of LEDs is arranged, wherein the LEDs are mounted on a flexible printed circuit board, PCB, wherein the light guide further comprises scattering or diffusing particles and / or vacuum / gas bubbles for out-coupling light.

[0010] According to an embodiment of the present invention, the continuous optical element is on top of or encapsulates the string of the plurality of LEDs and the flexible PCB.

[0011] According to an embodiment of the present invention, a wavelength converting material is provided at an out-coupling surface of the light guide.

[0012] According to an embodiment of the present invention, the scattering or diffusing particles and / or vacuum / gas bubbles for out-coupling light are adapted to generate distortions of the optical characteristics of the light guide, wherein the distortions are located on the surface / edge of the light guide and / or inside of the light guide.

[0013] The light guide may be provided with diffusing means for out-coupling light. The diffusing means enhances the out-coupling of the light guided into the light guide and thus, renders the light guide more clearly visible. In an embodiment of the invention, the structure of the out-coupling surface (e.g. the roughness of the surface) may be selected to adjust the scattering of the light. Further, the light guide may comprise (scattering or diffusing) particles and / or vacuum / gas bubbles for out-coupling light. In other words, distortions of the optical characteristics of the light guide are provided for scattering out some of the light. These distortions may be located on the surface / edge of the light guide and / or inside of the light guide. Generally, any optical distortion resulting in a change of the internal light angles may result in that part of the light is coupled out of the light guide. Distortions in a 3D-shaped light guide may for example be obtained by local laser heating.

[0014] According to an embodiment of the present invention, the plurality of LEDs is dimmable.

[0015] According to an embodiment of the present invention, the lighting device comprises an envelope encapsulating the light guide, which is advantageous in that the light guide will be protected against damage and dust. Additionally, the lighting device will resemble a traditional incandescent light bulb.

[0016] According to an embodiment of the present invention, the lighting device comprises a base, wherein the base comprises a bayonet base or a screw base.

[0017] Further objectives of, features of, and advantages with, the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and nonlimiting detailed description of preferred embodiments of the present invention and examples, with reference to the appended drawings, in which: Fig. 1 shows a lighting device; Fig. 2 shows a light guide; Fig. 3 shows a light guide; and Fig. 4 is a general outline of a method of manufacturing a lighting device. DETAILED DESCRIPTION OF EMBODIMENTS

[0019] With reference to Figure 1, there is shown an exemplary lighting device.

[0020] Figure 1 shows a lighting device 1 comprising a first light emitting element 101 and a second light emitting element 102. The first light emitting element 101 is optically coupled to a light guide 110 having an out-coupling surface 111. The optical coupling can be provided e.g. via an optical element (not shown) arranged between the first light emitting element 101 and the light guide 110 or by linking the first light emitting element 101 directly to the light guide 110, as shown in Figure 1.

[0021] Optionally, the lighting device may be provided with additional first light emitting elements being optically coupled to the light guide 110. For example, one first light emitting element may be coupled to a first end of the light guide 110 and another first light emitting element may be coupled to another end of the light guide 110 (opposite to the first end).

[0022] Further, the lighting device may be provided with additional second light emitting elements 102 for providing functional lighting.

[0023] The first light emitting element 101 and / or the second light emitting element 102 may for instance be light emitting diodes, LEDs, such as e.g. laser LEDs. For example, an amber colored LED, providing a warm light, may be used as the first light emitting element 101, thereby resulting in a light guide resembling a warm glowing filament (when the first light emitting element is activated / on). An alternative is to provide e.g. phosphor (or any other wavelength converting material) on top of the light guide (i.e. at the out-coupling surface of the lightguide) and select a phosphor providing a warm colored light. According to another example, the first light emitting element 101 may comprise a red LED, a green LED and a blue LED, thereby together providing a white light, which may be modulated into different colors by controlling the red, green and blue LED.

[0024] Further, an LED of a colder color (which may be more efficient), such as white, may be used as the second light emitting element 102, thereby providing light being suitable for functional lighting. According to another example, the second light emitting element 102 may comprise a red LED, a green LED and a blue LED, thereby together providing a white light, which may be modulated into different colors by controlling the red, green and blue LED. However, it will be appreciated that the examples are not limited to such color configuration, the light emitting elements 101, 102 in the lighting device may be of any desired color.

[0025] The light guide 110 may comprise an optical fiber (like an optical wave guide) made of a suitable material such as plastics or glass-fiber. The use of glass-fiber material is advantageous because of its optical quality and material characteristics (e.g. sensitivity to heat). The optical fiber may be of a shorter or longer length allowing a simple or more complex design. For example, the optical fiber may be spirally wound in order to resemble a traditional retro-filament.

[0026] The out-coupling of light from the out-coupling surface 111 of the light guide 110 may be achieved (and / or enhanced) in different ways. Some of the light may be out-coupled due to curvatures of the light guide 110. Moreover, the light guide 110 may be provided with diffusing means for out-coupling the light. In general, any optical distortion added to the light guide will provide out-coupling of light. The diffusing means may be provided e.g. by making the out-coupling surface 111 rough (e.g. by sand-blasting, scratching, or molding in a texture in the surface), or by providing indents or small protrusions in the out-coupling surface 111. Further, particles (e.g. white paint) and / or vacuum / gas bubbles (e.g. created by local laser heating) may be provided on or inside the light guide such that light is scattered out of the light guide.

[0027] According to an example, the light guide 110 may comprise at least one connecting port 112 to which the first light emitting element 101 may be optically coupled. The present example is advantageous in that it allows a great part of the light emitted from the first light emitting element 101 to be received and out-coupled by the light guide 110, thereby serving a decorative purpose, and still a great part of the light emitted from the second light emitting element 102 provides an illumination without unnecessary considerable energy-losses in any light guide.

[0028] However, some (i.e. a relatively small part) of the light emitted from the second light emitting element(s) 102 may be coupled into the light guide 110 via the out-coupling surface 111, and thus, coupled out again via the out-coupling surface 111, thereby contributing to the illumination out of the light guide 110.

[0029] With reference to Figure 2, there is shown an alternative design of a light guide according to an example not according to the invention. Figure 2 shows a light guide in the form of a light guide plate 210 being optically coupled to a first light emitting element 201. Some of the light emitted from the first light emitting element 201 is coupled out via an edge 211 which may be curved (and optionally rough), thereby resulting in the appearance of a filament such as in a traditional light bulbs. Further, light may be coupled out via diffusing means provided inside the light guide plate 210 or on the surface of the light guide plate 210.

[0030] It will be appreciated that the light guide may be designed in any desired three-dimensional shape, such as a spherical or prismatic shape. Further, the diffusing means may be provided at any desired position in or on the light guide. For example, the diffusing means may form a pattern (such as a filament-resembling pattern).

[0031] With reference to Figure 3, there is shown another design of a light guide according to an embodiment of the invention. Figure 3 shows a light guide 320 in the form of a continuous optical element 323 in which a string of a plurality of LEDs 321 is arranged. The LEDs 321 may be mounted on a small flexible PCB (printed circuit board) 322 with the continuous optical element 323 on top of it (or encapsulating it).

[0032] Turning again back to Figure 1, further examples will be described. The lighting device 1 may further comprise an envelope 130 encapsulating the first light emitting element 101, the second light emitting element 102 and the light guide 110. Preferably, the envelope 130 is transparent (or at least semi-transparent) such that the light guide 110 is visible for providing a decorative effect. Further, the envelope 130 may be formed as a bulb resembling a traditional incandescent light bulb. The lighting device 1 may further comprise a base 140 at which the first light emitting element 101 and the second light emitting element 102 are arranged. The base 140 may comprise a bayonet base or a screw base 141 (e.g. of the type E14, E26 or E27), which is advantageous in that the lighting device can be fitted in conventional lamp fittings and used as a replacement for a traditional incandescent light bulb (retro-fitting). The base 140 may further comprise a heat-sink 142 for cooling the light emitting diodes 101, 102. Optionally, the light emitting elements 101, 102 may be arranged such that an upper portion of the heat-sink 142 (or an upper portion of the base 140) hides the light emitting elements 101, 102 (as shown in Figure 1) for reducing the risk of direct view of them. Further, the inside of the upper portion of the heat-sink 142 may be reflective such that all (or at least almost all) light emitted from the light emitting elements 101, 102 can be output from the lighting device.

[0033] The lighting device may further comprise a diffusing / scattering element (not shown) in form of a plate on top of the second light emitting elements 102. For example, such plate may be arranged on top of the base 140. The plate may be provided with a hole where light emitted from the first light emitting element 101 may go through to be coupled into the light guide 110.

[0034] The lighting device 1 may further comprise electronic driving means 150 provided with a power supply for converting the mains voltage supply into an output signal suitable for driving the light emitting elements 101, 102. The electric driving means 150 may further comprise an electronic circuitry configured to control the light intensity of the first light emitting element 101 and / or the second light emitting element 102 such that the light intensity of the second light emitting element 102 is adjustable relative to the light intensity of the first light emitting element 101. Further, the electronic circuitry may be configured to slightly modulate the brightness (or color) of the first light emitting element 101, or to sequentially switch on and off the first light emitting element 101, for providing a flame and flickering effect of the light guide 110. The electronic circuitry may further contain a transfer function for correlating an input signal (such as input current or input voltage) with a light output and / or an emission color of the first and second light emitting elements. The electric driving means 150 may be controlled by a remote control unit, by buttons on the base 140 or by any other type of user interface.

[0035] In an example, the first light emitting element 101 and / or the second light emitting element 102 may be dimmable. In an example, the lighting device supports traditional incandescent light dimmers such that the light emitting elements can operate in a dimmed mode.

[0036] With reference to Figure 4, a method of manufacturing a lighting device according to an example will be described. Figure 4 shows the general outline of a method 400 of manufacturing a lighting device. The method comprises a step 410 of providing a first light emitting element, a step 420 of providing a light guide having an out-coupling surface, and a step 430 of optically coupling the first light emitting element to the light guide. Further, the method 400 comprises a step 440 of providing a second light emitting element dedicated for direct illumination from the lighting device.

[0037] While specific embodiments have been described, the skilled person will understand that various modifications and alterations are conceivable within the scope as defined in the appended claims.

[0038] For example, additional light guides with associated first light emitting elements may be provided in the lighting device. Further, the lighting device can be applied in standalone retro-fit incandescent bulb replacements as well as in dedicated new luminaries. Moreover, the lighting device is not limited to be designed as a conventional light bulb. It can also be designed e.g. as a tubular-shaped lamp with connectors at both ends of the tube.

Claims

1. Use of a light guide (320) in a lighting device resembling a traditional incandescent light bulb and enabling both decorative lighting and functional lighting, wherein the light guide (320) is in the form of a continuous optical element (323) in which a string of a plurality of LEDs (321) is arranged, wherein the LEDs (321) are mounted on a flexible printed circuit board, PCB, (322), wherein the light guide (320) further comprises scattering or diffusing particles and / or vacuum / gas bubbles for out-coupling light.

2. The use according to claim 1, wherein the continuous optical element (323) is on top of or encapsulates the string of the plurality of LEDs (321) and the flexible PCB (322).

3. The use according to any of the preceding claims, wherein a wavelength converting material is provided at an out-coupling surface of the light guide.

4. The use according to any of the preceding claims, wherein the scattering or diffusing particles and / or vacuum / gas bubbles for out-coupling light are adapted to generate distortions of the optical characteristics of the light guide, wherein the distortions are located on the surface / edge of the light guide and / or inside of the light guide.

5. The use according to any of the preceding claims, wherein the plurality of LEDs (321) is dimmable.

6. The use according to any of the preceding claims, wherein the lighting device comprises an envelope, wherein the envelope encapsulates the light guide.

7. The use according to any of the preceding claims, wherein the lighting device comprises a base, wherein the base comprises a bayonet base or a screw base.

Images