WO2009083853A1

WO2009083853A1 - Lighting system

Info

Publication number: WO2009083853A1
Application number: PCT/IB2008/055283
Authority: WO
Inventors: Lars R. C. Waumans; Denis J. C. Van Oers
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-12-20
Filing date: 2008-12-15
Publication date: 2009-07-09
Also published as: TW200946820A

Abstract

The present invention relates to a lighting system (100, 200, 300, 310), comprising a base structure (102, 202), at least one light source (104, 206) arranged on the base structure (102, 202), the at least one light source (104, 206) emitting a beam of light having a first bandwidth, and a housing (106, 204, 302, 312) provided with a wavelength converting material (108), the wavelength converting material (108) being adapted to transform light having the first bandwidth to light having a second bandwidth, the second bandwidth being broader than the first bandwidth, wherein the lighting system (100, 200, 300, 310) further comprises an optical member (110) arranged between the at least one light source (104, 206) and the housing (106, 204, 302, 312), the optical member (110) being adapted to modify a shape of said beam of light to increase the surface area of the housing (106, 204, 302, 312) receiving light emitted by the at least one light source (104, 206). An advantage with the present invention is that the resulting lighting system will be perceived more naturally for an observer, i.e. similar to a conventional light bulb being homogeneously lit.

Description

LIGHTING SYSTEM

FIELD OF THE INVENTION

The present invention relates to a lighting system comprising a base structure, at least one light source, and a housing provided with a wavelength converting material.

DESCRIPTION OF THE RELATED ART

Recently, much progress has been made in increasing the brightness of light- emitting diodes (LEDs). As a result, LEDs have become sufficiently bright and inexpensive to serve as a light source in for example lighting system such as lamps with adjustable color, direct view Liquid Crystal Displays (LCDs) and in front and rear projection displays. By mixing and controlling the intensity of differently colored LEDs, e.g. red, green and blue

LEDs, any number of colors can be generated, e.g. white. The generated light color is further determined by the type of LEDs used.

One of the disadvantages with LEDs is that they are relatively narrow banded. A combination of several primary colors therefore results in a spectrum with a number of wavelength peaks. This means that although it is possible to make white with three LEDs

(e.g. red, green and blue), this does not necessarily yield very natural colors when objects are illuminated with this light. It has therefore been suggested to apply a phosphor coating to an LED, such that the narrow banded light emitted by the LED is transformed to light having a broader spectral bandwidth. An example of such an implementation is disclosed in US 6 504 301, illustrating an LED package comprising one or more blue LEDs and a florescent member, the LED package being suitable for retrofitting of a conventional MR- 16 halogen package. The fluorescent member is adapted to receive the blue light emitted by the LEDs (at approximately 460 - 480 nm), and to up-shift the optical energy to a mean wavelength of approximately 520 nm. The resulting emission is a broadband light stretching from 480 to 620 nm. However, the disclosed LED package is not suitable for retrofitting conventional bulbs, such as for example the standard "A" shaped bulb, or more complex bulb shapes/forms. OBJECT OF THE INVENTION

There is therefore a need for a novel lighting system that is useful for retrofitting of for example conventional or more complex light bulbs, where the lighting system can be manufactured at a cost suitable for the low cost consumer environment.

SUMMARY OF THE INVENTION

According to an aspect of the invention, the above object is met by a lighting system comprising a base structure, at least one light source arranged on the base structure, the at least one light source emitting a beam of light having a first bandwidth, and a housing provided with a wavelength converting material, the wavelength converting material being adapted to transform light having the first bandwidth to light having a second bandwidth, the second bandwidth being broader than the first bandwidth, wherein the lighting system further comprises an optical member arranged between the at least one light source and the housing, the optical member being adapted to modify a shape of said beam of light to increase the surface area of the housing receiving light emitted by the at least one light source, or to equalize observed luminance of the housing.

The introduction of the optical member, in the form of e.g. a secondary optics, allows for the light emitted by the at least one light source to evenly spread onto essentially the complete visible surface area of the housing. The optical member is arranged to receive the beam of light emitted by the at least one light sources and reshape the beam such that it fits the shape of the housing, i.e. essentially all of the surface area of the housing will receive light from the at least one light source. As such, it is desirable that light emitted by the at least one light source is homogenously received by the wavelength converting material arranged together, possibly integrated with, the housing. An advantage with the present invention is thus that the resulting lighting system will be perceived more naturally for an observer, i.e. similar to a conventional light bulb being homogeneously lit. The housing may be formed from a material comprising glass, plastic, synthetic, polymer, or any other suitable transparent or translucent material. For reassembling an ordinary lighting system, e.g. a light bulb, the housing is preferably configured to have the same form factor as for example one of a halogen, incandescent and fluorescent light bulb. However, the optical member comprised in the lighting system allows for the housing to be arranged according to different complex forms and shapes. That is, the positioning and/or assemblage of the optical member is adjusted in relation to the size and shape of the housing. According to a preferred embodiment of the invention, the lighting system comprises a plurality of light sources, for example a plurality of blue LEDs, UV LEDs, or a plurality of differently colored LEDs. The use of blue LEDs is advantageous as currently known high grade wavelength converting materials have a high conversion efficiency when receiving light within the blue bandwidth, e.g. having a main light emission around 460 - 480 nm. Furthermore, it is also possible to include a plurality of differently colored LEDs (such as for example a combination of a blue, a red and a green LED, i.e. LEDs having different and separate peak wavelengths). In such a case, the inclusion of the red and the green LED (or at least one of them) allows for a "color boost", i.e. for filling gaps in the visible spectrum, in the bandwidth of the included LED. Advantages with LEDs include decreased power consumption and an increased lifetime of the lighting system as compared to a conventional light bulb. The LEDs may furthermore be arranged to emit violet light.

Preferably, the second bandwidth is selected to be between 400 and 700 nm. That is, it is preferred that the lighting system emits light covering the whole visible spectrum/band, i.e. produces essentially white light. As understood by the skilled addressee, the lighting system will generally emit light being a mixture of light of the first bandwidth and the second bandwidth.

In another preferred embodiment of the invention, the housing, sometimes also referred to as a bulb structure, is detachably connected to the base structure. In such an embodiment it is possible to fit differently and complex-shaped housings onto the base structure. This allows for a user of the lighting system to change the housing to suite different environments, such as for example in a high profile design environment.

To allow the optical member to reshape and redirect the beam of light emitted by the light source to suite the housing, the optical member is preferably arranged onto the at least one light source, being reflective mirrors or collimators for redirecting and collimating. Therefore, a receiving end of the optical member is preferably arranged to coincide with the light source.

In yet another preferred embodiment of the invention, the base structure comprises control logic for controlling at least one of an intensity and a color point of light emitted by the at least one light source. The control logic is preferably adapted to receive signals from at least one sensor provided for measuring at least the output of the light sources in different spectral bands, the operation temperature of the light source, and possibly also the white light emitted by the lighting system. The control logic then adapts the intensity of the light source such that the lighting system is perceived to emit light having a continuous intensity. If the optionally, differently colored LEDs are introduced, the control logic can furthermore be adapted to increase or decrease the color boost provided by the extra LEDs. Preferably, the optical member comprises at least one of a collimator and a reflector. In one embodiment, the optical member comprises a combination of a plurality of different collimators and reflectors.

The wavelength converting material preferably comprises at least one of a phosphor, a scintillator, and a mixture of phosphors and scintillators. Both phosphors and scintillators are material used for "stretching" the bandwidth of light received by the wavelength converting material. A phosphor is a substance that exhibits the phenomenon of phosphorescence (sustained glowing after exposure to light or energized particles such as electrons). Similarly, a scintillator is a substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. The present invention allows for the mixture of different phosphors and/or scintillators. Furthermore, the wavelength converting material may comprise a fluorescent material, organic fluorescent material, inorganic fluorescent material, impregnated phosphor, phosphor particles, phosphor material, YAG:Ce phosphor, or other material which can convert electromagnetic radiation into illumination and/or visible light.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing currently preferred embodiments of the invention, in which:

Figure 1 is a block diagram illustrating a lighting system according to an embodiment of the present invention;

Figure 2 illustrates an alternative lighting system according to the invention comprising a detailed view of an optical member and corresponding light sources; and

Figures 3 a and 3b show alternative embodiments of lighting systems according to the present invention.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, 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 invention to the skilled addressee. Like reference characters refer to like elements throughout. Figure 1 shows a block diagram of a lighting system 100 providing a general description of the inventive concept. The lighting system 100 comprises a base structure 102 having a plurality of light sources arranged thereto. The light sources are in the present invention a plurality of LEDs 104. It would however be possible, and within the scope of the present invention, to use different types of light source, for example different types of solid- state light sources known in the art. The lighting system 100 further comprises a housing 106 arranged to connect to the base structure 102 and to essentially surround the LEDs 104. Generally, the base structure 102 comprises a heatsink and a control unit for controlling the lighting system 100. In the present invention, the housing 106 completely surround the LEDs 104 thereby forming a lighting system 100 closely resembling a normal light bulb. It would however be possible to arrange the housing as a covering element not fully surrounding the LEDs 104. Such an arrangement can for example be useful if arranging the lighting system 100 according to the present invention in a corner of a room, where the housing 104 provides a cover for two sides, and the two walls of the corner provides a cover on the other two sides. The housing may be formed from a material comprising glass, plastic, synthetic, polymer, or any other suitable material.

The housing 106 is preferably provided with a thin layer of a wavelength converting material 108 adapted to receive light having a first peak wavelength, and convert an essential part of that light to light having a longer second peak wavelength. In accordance with the invention, the LEDs 104 are adapted to emit light having the first peak wavelength, preferably within the lower region of the visible spectrum. It would however also be possible, and within the scope of the invention, to use LEDs (or different light source(s)) having different colors. However, at present, the currently available wavelength converting materials 108 have a higher conversion ratio when receiving light in the lower visible wavelength spectrum. When the wavelength converting material 108 receives the light emitted by the LEDs 104, the wavelength converting material 108 will receive the light, convert a major part of that light, and emit light having the second peak wavelength. However, some of the light having the first peak wavelength will not be converted, but thus be allowed to pass through the wavelength converting material 108 such that it mixes with the light having the peak wavelength. The resulting light emitted by the lighting system 100 will thus be a uniform mixture of the light having the first and the second peak wavelengths. According to the invention, the light having the first peak wavelength will have a first bandwidth, and the light having the second peak wavelength will have a second peak wavelength, where the second bandwidth is greater (i.e. broader) than the first bandwidth. Preferably, the second bandwidth covers a majority of the visible spectrum, i.e. between approximately 400 and 700 nm, perceived by an observer as essentially white light.

The wavelength converting material 108 is preferably selected from a group comprising at least one of or a mixture of a phosphor, a scintillator, a fluorescent material, an organic fluorescent material, an inorganic fluorescent material, an impregnated phosphor, phosphor particles, a YAG:Ce phosphor, or any other material that can convert electromagnetic radiation into illumination and/or visible light.

The lighting system 100 further comprises an optical member 110 arranged between the LEDs 104 and the housing 106. In the present embodiment, the optical member 110 comprises a predetermined lens system adapted to redirect and collimate the light emitted by the LEDs 104 such that it fits, or is suitable for, the form factor of the housing. In the illustrated embodiment, the housing 106 has a somewhat outstretched form factor, similar to an oval. The optical member 110 is therefore adapted to project more of the received beam of light provided by the LEDs 104 such that they also reach the far most outer parts of the housing 106. By adapting the optical member 110 in such a way, it is possible to provide a lighting system 110 having a housing 106 that is essentially homogenously lit. That is, all parts of the inside of the housing 106 receives essentially the same amount of light from the LEDs 104, after which the wavelength converting material 108 deposited on, or integrated with, the housing 106, converts the light to essentially white light. For reassembling an ordinary lighting system, e.g. a light bulb, the housing is preferably configured to have the same form factor as for example one of a halogen, incandescent and fluorescent light bulb, when placed in a luminaire. Solitaire placed lighting systems allow big shape freedom.

In figure 1, all of the LEDs 104 are blue LEDs having a peak wavelength around approximately 460 - 480 nm. It would however be possible to use different types of light sources emitting light having a different peak wavelength. It would furthermore be possible to include one or a plurality of light sources that emits light within a different wavelength range, for example within the orange - red spectrum. Such inclusion can provide a color boost in a case where the wavelength converting material 108 is not that strong in providing light in that spectrum area. For controlling the lighting system 100, the base structure 102 preferably comprises control logic for controlling the intensity of the LEDS 104. The control logic comprised in the base structure is preferably also adapted to receive an information signal from a sensor provided for measuring the light emitted by the LEDs 104 and/or the light emitted by the lighting system 100. Such a sensor can for example be arranged next to the LEDs 104, collecting minor amount of scattered light. In controlling the LEDs 104, the control logic will receive the information signal from the sensor, and adapt the light emitted by the LEDs 104 such that it is kept at essentially the same level. The sensor can be a light diode, or a similar device. The control logic can also be adapted to receive an information signal from a temperature sensor, and control the LEDs 104 based on the same criteria's as discussed above.

Turning now to figure 2, illustrating an alternative lighting system 200 according to the invention. Similarly to figure 1 , the alternative lighting system 200 comprises a base structure 202, and a housing 204. The housing 204 is in the illustrated embodiment built as a complex shaped multi-legged arrangement, e.g. comprising two, three, or more legs. Such a multi legged arrangement is generally suitable for design related implementations, for example in display and showcase environments.

Also illustrated in figure 2 is a detailed view of an optical member and corresponding blue LED light sources 206. The optical member comprises collimators 208 and reflectors 210 for directing the beam of light emitted by the light sources 206. With the application of the collimators 208, the shape of the light beams will be tuned more narrow and will be aimed at the reflective facets of the reflectors 210 that are placed adjacent to the collimators 208, collecting the light beams from the light sources 206 and redirecting it towards the bulb legs, i.e. the housing 204, in such a way that the inner surface of the bulb legs efficiently are illuminated with blue light. The shape and the angle of the reflectors 210, e.g. in the form of mirrors, realize an acceptable uniform luminance pattern on the surface of the housing 204, which is scattering the (e.g. white) light towards the ambient, where the white light is generated due to the conversion of the light from blue to white light as the housing 204 is integral covered (inside) with a fluorescent layer. In the illustrated embodiment, each of the three legs of the housing 204 has a corresponding light source 206, reflector 208 and collimator 210.

In figure 2, and subsequent figure 3a and 3b, the base structure 202 is arranged to resemble a normal E27 base, thus making it useful as a retrofit e.g. for a normal A shape, or similar, bulb. However, different base sizes and bulb shapes are possible and within the scope of the present invention. Similarly to figure 1, the base structure preferably comprises a heatsink and a control unit, or similar, for controlling the lighting system 200.

Figures 3 a and figure 3b show alternative embodiments of lighting systems 300 and 310 according to the invention. In figure 3a, the housing 302 has been arranged such that it comprises a large round flat surface providing a large lighting area. Correspondingly, the lighting systems 310, in figure 3b, has been arranged to have a shape and form resembling a bottle. In both embodiments, the optical member has been adapted such that it provides an acceptable uniform luminance pattern on the surface of the housing.

Furthermore, the skilled addressee realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, the skilled addressee understands that many modifications and variations are possible and within the scope of the appended claims. For example it would be possible to construct the housing according to any different form or shape, for example shapes resembling animals, letters, logos, pictograms, or similar. In conclusion, it is according to provide a novel lighting system comprising a base structure, a plurality of LEDs arranged on the base structure, and a housing provided with a wavelength converting material that is adapted to transform light emitted by the LEDs to light having a broader bandwidth, e.g. white light. The lighting system further comprises an optical member arranged between the light source and the housing, the optical member being adapted to modify the shape of the beam of light to increase the surface area of the housing receiving light emitted by the light source. The lighting system according to the invention will be perceived more naturally for an observer, i.e. similar to a conventional light bulb being homogeneously lit, while at the same time providing advantages in relation to the possibility to adapt the shape and form of the housing such that it resembles any suitable shape or form.

Claims

CLAIMS:

1. A lighting system (100, 200, 300, 310), comprising: a base structure (102, 202); at least one light source (104, 206) arranged on the base structure (102, 202), the at least one light source (104, 206) emitting a beam of light having a first bandwidth; and - a housing (106, 204, 302, 312) provided with a wavelength converting material (108), the wavelength converting material (108) being adapted to transform light having the first bandwidth to light having a second bandwidth, the second bandwidth being broader than the first bandwidth, wherein the lighting system (100, 200, 300, 310) further comprises an optical member (110) arranged between the at least one light source (104, 206) and the housing (106, 204, 302, 312), the optical member (110) being adapted to modify a shape of said beam of light to increase the surface area of the housing (106, 204, 302, 312) receiving light emitted by the at least one light source (104, 206).

2. Lighting system (100, 200, 300, 310) according to claim 1, wherein the lighting system (106, 204, 302, 312) comprises a plurality of light sources (104, 206), and the light sources (104, 206) are selected from a group comprising blue LEDs, UV LEDs, and a plurality of differently colored LEDs.

3. Lighting system (100, 200, 300, 310) according to any of claims 1 or 2, wherein the second bandwidth is between 400 and 700 nm.

4. Lighting system (100, 200, 300, 310) according to any one of the preceding claims, wherein the housing (106, 204, 302, 312) is detachably connected to the base structure (102, 202).

5. Lighting system (100, 200, 300, 310) according to any one of the preceding claims, wherein the optical member (110) is arranged onto the at least one light source (102, 206).

6. Lighting system (100, 200, 300, 310) according to any one of the preceding claims, wherein the base structure (102, 202) comprises control logic for controlling at least one of an intensity and a color point of light emitted by the at least one light source (102, 206).

7. Lighting system (100, 200, 300, 310) according to any one of the preceding claims, wherein the optical member (110) comprises at least one of a collimator (208) and a reflector (210).

8. Lighting system (100, 200, 300, 310) according to any one of the preceding claims, wherein the wavelength converting material comprises at least one of a phosphor, a scintillator, a mixture of phosphors and scintillators.

9. Lighting system (100, 200, 300, 310) according to any one of the preceding claims, wherein the housing (106, 204, 302, 312) is configured to resemble at least one of a halogen, incandescent and fluorescent light bulb.

10. Lighting system (100, 200, 300, 310) according to any one of the preceding claims, wherein the optical member (110) provides for the housing (106, 204, 302, 312) to be arranged according to different complex forms and shapes.