Abstract:
Proposed is a light source comprising: first and second semiconductor diode structures adapted to generate light, the first and second semiconductor diode structures being laterally adjacent to each other; a light output section at least partially overlapping both of the first and second semiconductor diode structures and adapted to output light from the first and second semiconductor diode structures; and a light reflecting structure at least partially enclosing side surfaces of the first and second semiconductor diode structures and the light output section and adapted to reflect light from the semiconductor diode structures towards the light output section. The area of the light output section is less than the combined area of the first and second semiconductor diode structures.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a light source, and more particularly to a light source comprising a plurality of semiconductor light sources. 
       BACKGROUND OF THE INVENTION 
       [0002]    Semiconductor light sources, such as light emitting diodes (LEDs), high power LEDs, organic LEDs (OLEDs) and laser diodes are known to be energy efficient and small light sources that can exhibit a small/low etendue (i.e. the product of emitting area with solid angle in which the light is emitted). 
         [0003]    Such semiconductor light sources may therefore be beneficial for applications where a bright light source is needed. Typical example applications include projection systems, automotive lighting, camera flashlights, and spot lights. For these examples, improved miniaturization is often desirable. However, merely reducing the size of a semiconductor light source reduces the generated light flux. 
         [0004]    It is known to obtain increased luminance from a semiconductor light source by means of a mix box with a small aperture (i.e. light output section) from which the light can escape.  FIGS. 1A and 1B  illustrate a known LED-based light source  10  employing this concept, wherein light generated by an LED  12  (on a die substrate  14 ) is recycled/reflected in a mix box  16  having high reflectivity until it escapes via a small aperture  18 . By the aperture  18  being “small” it is simply meant as being smaller than the LED  12  such that the aperture area A A  (i.e. width W A  X L A ) is less than the LED area A LED  (i.e. width W LED  X L LED ) of the LED  12 . 
       SUMMARY OF THE INVENTION 
       [0005]    The invention is defined by the claims. 
         [0006]    According to an aspect of the invention there is provided a light source comprising: first and second semiconductor diode structures adapted to generate light, the first and second semiconductor diode structures being laterally adjacent to each other; a light output section at least partially overlapping both of the first and second semiconductor diode structures and adapted to output light from the first and second semiconductor diode structures; and a light reflecting structure at least partially enclosing side surfaces of the first and second semiconductor diode structures and the light output section and adapted to reflect light from the semiconductor diode structures towards the light output section, wherein the area of the light output section is less than the combined area of the first and second semiconductor diode structures. 
         [0007]    Embodiments may achieve savings in materials and/or space by arranging light emitting semiconductor diode structures (such as LEDs) to be laterally adjacent and then sharing a single light output section between the adjacent diode structures. Thus, there is proposed a concept for forming a high luminance LED-based light source that has a light output section which is of lesser area than the light generating portions (e.g. semiconductor diode structures). By arranging such a light output section to at least partially overlap a plurality of light generating structures, the light output section can comprise a single component/structure (such as an aperture or an phosphorescent platelet, for example) that is shared across multiple light sources to provide savings/reductions in materials, size, device complexity, and/or manufacturing complexity. 
         [0008]    In other words, embodiments may provide a high-luminance light source comprising laterally arranged sub-sources that are overlapped by a common light output section. The position(s) and/or shape of the light output section can be changed or designed to enable tiling of the sub-sources such that edges of multiple light output sections can be closely aligned (when viewed from above, for example). 
         [0009]    Multiple LED light sources may therefore be strategically arranged in the horizontal axis so that they are overlapped by a single or common light output section. For example, pairs of closely positioned LED light sources may be aligned with each other to form a column-like array of pairs such that, when viewed from directly above (i.e. plan view), a single elongate light output section can at least partially overlap each pair of LED light sources in the array. By arranging multiple LED light sources to be overlapped by a common light output section, savings in material and/or space (e.g. a reduction in foot print size) may be achieved. 
         [0010]    The LED light sources of the present disclosure may be any type of LED, such as a Flip Chip type (Thin Film Flip Chip), Patterned Sapphire Substrate, top connected/top emission, top-bottom connected. Also, the light source could be used as naked die, or packaged. 
         [0011]    A light output section (or light emission area) of an LED light source refers to an area towards or through which light from the LED is output (or emitted). A cavity or cavities of a LED light source may thus extend towards the light output section. The light output section may for example be an area (volume) of the growing template (growth substrate), such as a sapphire. Light from the semiconductor structures may be emitted in various directions, thus resulting in some emitted light being incident on the light reflecting structure and reflected back towards the semiconductor structure(s). Light generated by the semiconductor structures may therefore be reflected by the light reflecting structure until it is directed through (and out of) the light output section. The arrangement of the light reflecting structure and the light output section may therefore be considered as forming a ‘mix-box’ structure which reflects light rays until they are output through the light output section. Accordingly the light output direction (from the light output section) may be generalized to be in a vertical direction (e.g. upwardly in the Figures) along which light is output from the light output section. However, it will be understood that not all light output from a light output section may be output exactly vertically. Thus, the light output direction should be understood to refer to the general upwardly extending direction that light may be output from a light output section, extending away from the surface of the light output section for example. 
         [0012]    The semiconductor diode structures may be arranged such that there is substantially zero separation between adjacent edges of the semiconductor diode structures. In practice, however, it may be difficult to perfectly align adjacent edges to have zero lateral separation. Thus, in embodiments, the semiconductor diode structures may be laterally separated by a negligible or small amount. For example, there may be a lateral separation between the adjacent edges of the two semiconductor diode structures, and this lateral separation or overlap may be less than 10% of the lateral width of the semiconductor diode structures. In embodiments, it may be preferable to reduce such separation to a minimum value (e.g. less than 5% of the lateral width of the semiconductor diode structures, and even more preferably less than 1% of the lateral width of the semiconductor diode structures). 
         [0013]    In an embodiment, the light output section may comprise an aperture formed in the light reflecting structure. 
         [0014]    Also, an embodiment may further comprise a layer of optical enhancement material below the light output section and at least partially overlapping both of the first and second semiconductor diode structures, wherein the light reflecting structure at least partially encloses side surfaces of the layer of optical enhancement material. In other words, an embodiment may further comprise a layer of optical enhancement material sandwiched between the top of the semiconductor light sources and the bottom of the light output section. 
         [0015]    Further, in embodiments, the light output section may comprise an optical enhancement material. 
         [0016]    Optical enhancement material may be a ‘color conversion fill’, such as a phosphorescent material. Examples may include a ceramic phosphor, a phosphor platelet, or a known phosphorescent material referred to as a “lumiramic” material. This may further help to maintain the etendue of the lateral emission area and/or change the color of the emitted light. 
         [0017]    Further, if an embodiment comprises a plurality of light output sections, some or all of the light output sections may comprise (e.g. be filled) with different materials. As an example, certain light output sections may be filled with a first type of phosphor (e.g. converting blue to white) and others may be filled with another type of phosphor (e.g. converting blue to red). 
         [0018]    Embodiments may be employed in the field of automotive lighting and other fields/applications where high-luminance lighting is desirable. 
         [0019]    Thus, according to an aspect of the invention, there may be provided an automotive light comprising a light source according to an embodiment. 
         [0020]    According to another aspect of the invention, there may be provided a projector light comprising a light source according to an embodiment. 
         [0021]    According to yet another aspect of the invention, there is provided a method of manufacturing a light source comprising: arranging first and second semiconductor diode structures adapted to generate light to be laterally adjacent to each other; providing a light output section at least partially overlapping both of the first and second semiconductor diode structures, the light output section being adapted to output light from the first and second semiconductor diode structures; and at least partially enclosing sides surfaces of the first and second semiconductor diode structures and the light output section with a light reflecting structure, the light reflecting structure being adapted to reflect light from the semiconductor diode structures towards the light output section, wherein the area of the light output section is less than the combined area of the first and second semiconductor diode structures. 
         [0022]    The step of arranging may comprise arranging the first and second semiconductor diode structures such that there is a lateral separation between the adjacent edges of the first and second semiconductor diode structures, the lateral separation being less than 10% of the lateral width of the first and second semiconductor diode structures. 
         [0023]    The light output section may comprise an aperture formed in the light reflecting structure. 
         [0024]    Embodiments may further comprise forming a layer of optical enhancement material below the light output section and at least partially overlapping both of the first and second semiconductor diode structures, wherein the step of at least partially enclosing sides surfaces of the first and second semiconductor diode structures and the light output section with a light reflecting structure light reflecting structure further comprise at least partially enclosing side surfaces of the layer of optical enhancement material with the light reflecting structure light reflecting structure. 
         [0025]    In an embodiment, the light output section may comprise an optical enhancement material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Examples of the invention will now be described in detail with reference to the accompanying drawings, in which: 
           [0027]      FIG. 1A  is a cross-sectional view of a known LED light source; 
           [0028]      FIG. 1B  is a plan view of the known LED light source of  FIG. 1A ; 
           [0029]      FIG. 2A  is a plan view of a light source according to an embodiment; 
           [0030]      FIG. 2B  is a cross-sectional view of the embodiment of  FIG. 2A  (taken along the line X-X of  FIG. 2A ); 
           [0031]      FIG. 3A  is a plan view of a light source according to another embodiment; 
           [0032]      FIG. 3B  is a cross-sectional view of the embodiment of  FIG. 3A  (taken along the line X-X of  FIG. 3A ); 
           [0033]      FIG. 4A  is a plan view of a light source according to another embodiment; 
           [0034]      FIG. 4B  is a cross-sectional view of the embodiment of  FIG. 4A  (taken along the line X-X of  FIG. 4A ); 
           [0035]      FIG. 5  illustrates a modification to the embodiment of  FIGS. 4A and 4B ; and 
           [0036]      FIG. 6  illustrates a modification to the embodiment of  FIGS. 2A and 2B . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0037]    The invention provides a light source comprising a plurality of LED light sources and a method for manufacturing the same. Embodiments may be of particular relevance to applications that require light of high or increased luminance from a relatively small and/or efficient light source. 
         [0038]    Embodiments employ the concept of arranging light emitting semiconductor diode structures (such as LEDs) to be laterally adjacent and then providing a single light output section (of reduced size compared to the aligned diode structures) overlapping the adjacent diode structures. In this way, a common light output section may be employed or shared across multiple LED light sources to provide savings or reductions in materials and/or manufacturing complexity. 
         [0039]    The term vertical, as used herein, means substantially orthogonal to the surface of a substrate. The terms lateral or horizontal, as used herein, means substantially parallel to the surface of a substrate. Also, terms describing positioning or locations (such as above, below, top, bottom, etc.) are to be construed in conjunction with the orientation of the structures illustrated in the diagrams. 
         [0040]    The diagrams are purely schematic and it should therefore be understood that the dimensions of features are not drawn to scale. Accordingly, the illustrated thickness and/or separation of any of the layers should not be taken as limiting. For example, a first layer drawn as being thicker than a second layer may, in practice, be thinner than the second layer. 
         [0041]    Referring to  FIG. 2 , there is depicted a light source according to an embodiment of the invention. More specifically,  FIG. 2A  is a plan view of the light source, and  FIG. 2B  is a cross-sectional view of the light source (taken along the line X-X of  FIG. 2A ). 
         [0042]    The light source comprises a plurality of LEDs  12  positioned on the upper surface of a substrate  20 . Here, the plurality of LEDs  12  are arranged in a  2 x 4  array comprising two columns of LEDs  12 , each column having four rows of LEDs  12 . Thus, it will be appreciated that the depicted arrangement of LEDs  12  may be described as comprising four pairs  12   1 , 12   2 , 12   3 , 12   4  of closely-positioned LED light sources  12  which are aligned in a column to form a column-like array of pairs. Being positioned on the flat upper surface of the substrate, the LEDs  12  can be described as being laterally adjacent to each other since they all lie in the same horizontal plane. 
         [0043]    A light output section  18  is provided on top of the LEDs  12  such that it partially overlaps the top/upper surface of each LED  12 . The light output section  18  is adapted to output light from the LEDs  12 . Here, the light output section  18  comprises an optical enhancement material such as phosphorescent material or a lumiramic. 
         [0044]    Accordingly, when viewed from directly above (i.e. in plan view as depicted in  FIG. 2A ), a single elongate light output section  18  partially overlaps each pair of LEDs  12  in the 2×4 array. A single, common light output section  18  partially overlaps all of the LEDs. 
         [0045]    A light reflecting structure  16  encloses the side surfaces of the LEDs  12  and the light output section  18 , and also encloses the LED top/upper surfaces that are not covered by the light output section  18 . Thus, the light reflecting structure  16  covers the LEDs  12  and light output section  18  such that only the top/upper surface of the light output section  18  is exposed (i.e. is not covered by the light reflecting structure  16 ). The light reflecting structure  16  comprises a highly reflective material that reflects light from LEDs  12  towards the light output section  18 . The light reflecting structure  16  may therefore be considered as forming a light mix box from which light can only escape via the light output section  18 . 
         [0046]    Because the area of the light output section  18  is less than the total area of the LEDs, the embodiment employs the concept of having a light output section  18  which is smaller than the LEDs  12  it is adapted to output light from. This enables increased luminance from the LEDs  12  to be obtained. Furthermore, the use of a single light output section  18  partially overlapping multiple light generating structures (e.g. LEDs  12 ) enables a single component or structure to be employed and shared across multiple light sources. A reduction in device complexity and required materials can therefore be obtained. 
         [0047]    Referring to  FIG. 3 , there is depicted a light source according to another embodiment of the invention. More specifically,  FIG. 3A  is a plan view of the light source, and  FIG. 3B  is a cross-sectional view of the light source (taken along the line X-X of  FIG. 3A ). 
         [0048]    The embodiment of  FIG. 3  is very similar to the embodiment of  FIG. 2 . Detailed description of all of the same or similar technical features will be omitted so as to avoid unnecessary repetition. Instead, it is noted that the embodiment of  FIG. 3  only differ from that of  FIG. 2  in that four light output sections  18   1 ,  18   2 ,  18   3 ,  18   4  are employed. Each light output section  18  is arranged to partially overlap a respective pair of LEDs. Thus, a first light output section  18   1  partially overlaps a first pair  12   1  of LEDs, a second light output section  18   2  partially overlaps a second pair  12   2  of LEDs, a third light output section  18   3  partially overlaps a third pair  12   3  of LEDs, and a fourth light output section  18   4  partially overlaps a fourth pair  12   4  of LEDs. It will therefore be appreciated that each light output section  18  is arranged to partially overlap two LEDs. 
         [0049]    As with the embodiment of  FIG. 2 , the area of a light output section  18  is less than the total area of the LEDs it partially covers, thus employing the concept of having a light output section  18  which is smaller than the LEDs  12  it is adapted to output light from. This enables increased luminance from the LEDs  12  to be obtained. Furthermore, the use of a single light output section  18  partially overlapping two light generating structures (e.g. LEDs  12 ) enables a reduction in materials and complexity whist providing for light of increased luminance from the light source. It may also enable a similar layout of light outputting areas as current devices, which can assist implementation in existing products. 
         [0050]    Referring to  FIG. 4 , there is depicted a light source according to another embodiment of the invention. More specifically,  FIG. 4A  is a plan view of the light source, and  FIG. 4B  is a cross-sectional view of the light source (taken along the line X-X of  FIG. 4A ). 
         [0051]    The embodiment of  FIG. 4  is similar to the embodiment of  FIG. 2 . Detailed description of all of the same or similar technical features will be omitted so as to avoid unnecessary repetition. Instead, it is noted that the embodiment of  FIG. 4  differs from that of  FIG. 2  in that the single light output section  18  now comprises an aperture  18  (formed in the light reflecting structure  16 ). As with the embodiment of  FIG. 2 , the light output section  18  (i.e. aperture 18 ) of the embodiment of  FIG. 4  is situated above the LEDs  12  such that it partially overlaps each LED  12 . Further, the shape and size of the light output section  18  of  FIG. 4  is very similar to that of  FIG. 2 . Thus, the area of the light output section  18  is less than the total area of the LEDs it overlaps, thereby employing the concept of having a light output section  18  which is smaller than the LEDs  12  it is adapted to output light from. 
         [0052]    Also, there is provided a layer  22  of optical enhancement material below the light output section  18  and overlapping all of the LEDs  12 . Here, the light output optical enhancement material comprises a lumiramic or phosphorescent material which is adapted to convert the color of light emitted by the LEDs. 
         [0053]    The light reflecting structure  16  covers the side surfaces of the layer  22  of optical enhancement material as well as a portion of the upper surface of the layer  22  of optical enhancement material. In other words, the light reflecting structure  16  covers the LEDs  12  and layer  22  of optical enhancement material such that only the top/upper surface of layer  22  of optical enhancement material is exposed (i.e. uncovered) by the light output section  18 . 
         [0054]    Hence, it will be appreciated the  FIG. 4  illustrates an embodiment wherein the light output section  18  comprises an aperture or cavity. The layer  22  of optical enhancement material is provided in this embodiment to alter the color of light emitted by the LEDs  12 . However, it will be appreciated that the embodiment of  FIG. 4  may be modified to not include the layer  22  of optical enhancement material (if alteration of the color of light from the LEDs is not required, for example). 
         [0055]    Alternatively, the embodiment of  FIG. 4  may be modified by replacing the aperture  18  of  FIG. 4  with optical enhancement material (such as lumiramic or phosphorescent material, for example). Such a modification to the embodiment of  FIG. 4  is depicted in  FIG. 5 , wherein the light output section comprises first  24 A and second  24 B portions of phosphorescent material. The first  24 A and second  24 B portions of phosphorescent material may provide for the alteration of output light to different colors, for example. 
         [0056]    It is noted that, in practice, the light reflecting structure  16  may not be entirely reflecting. In other words, the light reflecting structure may not have substantially 100% reflectivity, and so some light may leak through it. This increases the size of the light outputting area and hence reduces luminance. This may introduce color over position effects (e.g. a blue halo around white light in the center). To address this, embodiments may be made “light leak tight” by blocking the light with an opaque/reflective coating. Such a modification to the embodiment of  FIG. 2  is depicted in  FIG. 6 , wherein a reflective coating  30  is provided on the upper surface of the light reflecting structure  16 . This helps to lower the overall light transmittance of the light reflecting structure  16  by reflecting light that is incident on the lower surface of the reflective coating  30  from below (e.g. light leaking through the light reflecting structure  16 ). 
         [0057]    Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.