Abstract:
High lumen output and brightness illumination modules using an excitation light source and wavelength conversion part with multi-channel heat dissipation are disclosed. The exciting light source is a light emitting diode or a laser diode emitting in the UV and/or blue region. The luminescent material in the wavelength conversion part absorbs the excitation light and emit longer wavelength light. The enhancement approaches for brightness and polarization is disclosed.

Description:
PRIORITY CLAIM AND RELATED APPLICATIONS 
       [0001]    This patent document claims the benefits of U.S. Provisional Application No. 61/398,509 entitled “HIGH BRIGHTNESS ILLUMINATION LED DEVICE USING WAVELENGTH CONVERSION MATERIALS” filed Jun. 28, 2010, the disclosure of which is incorporated by reference as part of the specification of this document. 
     
    
     BACKGROUND 
       [0002]    This document relates to lighting devices and modules. 
         [0003]    Light sources based on wavelength conversion use excitation light produced by solid-state light sources such as laser diodes (LDs) or light emitting diodes (LEDs) to optically excite wavelength conversion materials such as phosphors or quantum dots to produce high brightness light at wavelengths different from the wavelength of the excitation light. 
       SUMMARY 
       [0004]    High lumen output and brightness illumination modules using an excitation light source and wavelength conversion part with multi-channel heat dissipation are disclosed. The exciting light source is a light emitting diode or a laser diode emitting in the UV and/or blue region. The luminescent material in the wavelength conversion part absorbs the excitation light and emit longer wavelength light. The enhancement approaches for brightness and polarization is disclosed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a schematic view of an exemplary illumination module. 
           [0006]      FIG. 2  is a schematic view of the illumination module with optics that delivers excitation light to luminescent layer. 
           [0007]      FIG. 3  is a schematic view of the illumination module with wavelength division multiplexer optics that combines outputs of two excitation light sources with different wavelengths. 
           [0008]      FIG. 4  is a schematic view of the illumination module with an example of delivering optics that collect multiple light sources (LEDs) and then focus it onto luminescent layer with preservation light source Etendue. 
           [0009]      FIG. 5  is a schematic view of the illumination module with another example of delivering optics that couple multiple light sources (LEDs) into fiber and then deliver excitation light with fiber bundle onto luminescent layer with preservation light source Etendue. 
           [0010]      FIG. 6  is a schematic view of an illumination module with metal sheet in the embodiment of  FIG. 2 . 
           [0011]      FIG. 7  is a schematic view of an illumination module with heat-sink. 
           [0012]      FIG. 8  is a schematic view of an illumination module with color filter transmitting excitation light and reflecting emission light from luminescent layer. 
           [0013]      FIG. 9  is a schematic view of an illumination module with angel selective optics. 
           [0014]      FIG. 10  is a schematic view of an illumination module with polarization selective optics. 
           [0015]      FIG. 11  is a schematic view of an illumination module with polarization selective optics. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    In certain conventional LED devices, such as white light LED devices, excitation light impinges on a wavelength conversion material attaching to blue LED die and the wavelength conversion material absorbs the excitation light and emits light at a wavelength longer than the wavelength of the excitation light. The wavelength conversion material such as phosphors is structured to have a similar size as LED chip. The brightness of such LED device is high since the Etendue is preserved in such a design. 
         [0017]    Some other LED devices use a “remote phosphor” design where the wavelength conversion material such as phosphors is located with some physical distance away from the LED die. Some implementations of this design demonstrated promising performance on high conversion efficiency from excitation light due to reduced back scattering of excitation light. In many LED devices based on this remote phosphor design, the wavelength conversion material is often located within the individual LED package and the phosphor area is significantly larger than the LED chip size. Therefore, the output lumen of these illumination sources is limited by the individual LED and its brightness is much lower than the LED with normal phosphors configuration where phosphors is directly deposit on LED. 
         [0018]    The LED device designs described in this document offer illumination modules that can direct one LED or combine multiple LED output onto single phosphors or one wavelength conversion material layer and provide multiple channels heat dissipation from the phosphors/wavelength conversion layer to heat sink of the module. Therefore, the LED device designs described herein offer a practical solution for generating high power and high brightness light with desired wavelength by LED or other solid-state light sources. 
         [0019]    The present designs of using multiple LEDs can achieve high luminous light output as well as high brightness. Such designs may be used to provide high brightness and high power illumination sources that are traditionally dominated by arc lamps such as xenon and high pressure mercury lamps. 
         [0020]      FIGS. 1-11  illustrate various features of exemplary illumination source devices described in this document. The numerals in  FIGS. 1-11  represent the following elements or components of the illustrated devices:
     1 . Luminescent layer, e.g., phosphors with liquid or gel     2 . Transparent solid plates, e.g., sapphire plates     3 . Excitation light source, e.g., blue LED     4 . Optics for delivering excitation light to luminescent layer;  4   b : wavelength division multiplexer that combines excitation light from different wavelength light sources     5 . Collimating optics for LED or LD     6 . Condensing optics     7 . Coupling optics for optical fiber     8 . Optical fiber     9 . Metal sheet     10 . Heat-sink     11 . Color filter, e.g., short-pass filter     12 . Angle sensitive optics     13 . Polarization selective filter   
 
         [0034]    In one implementation, an illumination device is described for providing high lumen output and brightness. Referring to  FIG. 1 , this device includes a light source  3  that provides excitation light; and a luminescent layer  1  in a liquid or gel form sandwiched by two solid plates  2  with a sufficiently high thermal conductivity (e.g., equal or greater than 15 W/m° C.). The liquid or gel of the luminescent material  1  absorbs light from excitation light source  3  at one wavelength range and emits light at second wavelength range. Both solid plates  2  are transparent to the excitation light from the light source  3  and emission light emitted by the luminescent material  1 . The liquid or gel of the luminescent material  1  has a composition that is wetting with the solid plates  2 . 
         [0035]    Referring to  FIGS. 6 ,  7 ,  8 ,  9 ,  10  and  11 , this device can include a metal sheet  9  that is sandwiched by two transparent solid plates  2 , This metal sheet  9  provides a channel of heat dissipation. The metal sheet  9  can be configured to have the same thickness as the luminescent layer  1  so that is sandwiched by the two solid plates  2  and is adjacent to the luminescent layer  1 . A liquid or thermal compound can be added between the metal sheet and the two solid plates to further improve the heat dissipation. The metal sheet has larger size than the solid plates  2  and is in physical and thermal contact with a heat-sink  10 . 
         [0036]      FIGS. 7 ,  8 ,  9 ,  10  and  11  further show that, a heat-sink  10  can be provided outside the two plates  2  to be in thermally and physically contact with two solid plates  2  and the metal sheet  9  to improve the heat dissipation of the device. The heat-sink  10  can be configured to have an aperture for transmitting the excitation and emission light and is in physical and thermal contact to the one or both solid plates. The heat sink  10  can include metal plates or ceramic plates. 
         [0037]    In some implementations as shown in  FIG. 5 , the illumination device may optionally include focusing optics  7  and optical fiber coupling optics  8  disposed between the light source  3  and the luminescent material  1 . 
         [0038]    In some implementations as shown in  FIG. 9 , a color filter  11  can be disposed between the luminescent material  1  and the light source  3  as a short pass filter that transmits the excitation light at a shorter wavelength than that of the emission light out of the luminescent material  1 . In addition, this short pass filter  11  can reflect light of longer wavelengths than that of the emission light to increase the optical efficiency and output brightness. 
         [0039]    In implementations such as in  FIGS. 9 ,  10  and  11 , an angle-selective reflecting layer or angle-sensitive optics  12  can be located adjacent the wavelength conversion material (i.e., the luminescent material  1 ) on a side opposite to the light source  3 . This element  12  reflects light of different incident angles differently to select desired light with certain incident angles as output light. For example, the angle-selective reflecting layer or angle-sensitive optics  12  can transmit light with small incident angles while reflecting light with large incident angles. For another example, the angle selective optics transmits majority of output light with incident angle smaller than a pre-defined angle and reflects majority of output light with incident angle larger than the pre-defined angle. The angle selective optics can be implemented as a thin film filter with alternative dielectric material coating or an optical filter with defined micro-optics geometries or nano-optics structures to provide the angle sensitive properties. 
         [0040]    In implementations shown in  FIGS. 10 and 11 , a reflective polarizer and/or wave-plate  13  can be disposed adjacent the wavelength conversion material  1  control optical polarization of the output light of the device. 
         [0041]    In implementations shown in  FIGS. 2 ,  3 ,  6 ,  7 ,  8 ,  9 ,  10  and  11 , a wavelength division multiplexing optics  4  is provided between the light source  3  and the luminescent material  1  and combine output of excitation solid-state light sources with different excitation wavelengths into a combined beam  1 . 
         [0042]    A method for generating multicolor light and dissipating heat from luminescent material is provided. This method includes: generating an excitation light using a light source; directing the excitation light onto wavelength conversion part, the wavelength conversion part is luminescent layer sandwiched by two transparent solid plates with good thermal conductivity, wherein the luminescent material capable of absorbing the excitation light and emitting light having wavelengths different from that of the excitation light; heat that generated in luminescent material is dissipated into two transparent solid plates with good thermal contact due to the liquid or gel form of luminescent layer, a metal sheet that also sandwiched by the solid plates provides further heat dissipation channel and serve as spacer to control the thickness of luminescent layer, a heat-sink that contacts both transparent solid plates and metal sheet removes heat from wavelength conversion part. 
         [0043]    Only a few implementations are disclosed. Enhancements and variations of the disclosed implementations and other implementations can be made based on what is described and illustrated.