Abstract:
The present disclosure describes light conversion modules each having a single laser diode or multiple laser diodes. The light conversion modules can be particularly small in size (height and lateral footprint) and can overcome various challenges associated with the high optical power and heat emitted by laser diodes. In some implementations, the light conversion modules include glass phosphors, which, in some instances, can resist degradation caused by the optical power and/or heat generated by the laser diodes. In some instances, the light conversion modules include optical filters which, in some instances, can reduce or eliminate human eye-safety risk.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/348,328, filed on Jun. 10, 2016. The contents of the earlier application are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    Light conversion modules or light converters are configured to convert the wavelength or range of wavelengths of a light emission generated from a light source to another wavelength or range of wavelengths (i.e., a converted light emission). For example, a light conversion module such as a camera flash can include a light-emitting diode (LED) and a phosphor (e.g., Ce + :YAG). In some instances, the phosphor may be suspended in a matrix such as silicone or another polymer, wherein the matrix ideally maintains high optical transmittance over the lifetime of the phosphor or light conversion module. During operation of such a light conversion module, the LED generates a light emission of a particular wavelength. When the light emission illuminates the phosphor, the phosphor can generate a converted light emission of another wavelength or range of wavelengths. In some instances, the converted light emission may be more functionally suited or aesthetically pleasing than the light emission generated by the LED. For example, an LED may be configured to emit ultraviolet light, which is invisible to humans, onto a phosphor configured to convert the ultraviolet light to a longer wavelength (or range of wavelengths), which is visible to humans. Such a process has readily apparent implications for applications such as camera flashes, interior lighting, and automotive headlights. In some instances, light emissions characterized by shorter wavelengths, such as ultraviolet light, permit the use of a wider range of phosphors. Indeed, this can be a distinct advantage for various applications such as camera flashes, interior lighting, and automotive head-lighting. 
         [0003]    Light conversion modules that use LEDs, however, experience a number of limitations. For example, LEDs are typically characterized by low optical power. Accordingly, a light conversion module would need to include a large volume of phosphor in order to achieve a desired optical output. Large phosphor volumes necessarily lead to a corresponding increase in the size (i.e., height and/or lateral footprint) of such a light conversion module. 
         [0004]    Compared to LEDs, other light sources such as laser diodes can exhibit far greater optical power; however, laser diodes implemented in light conversion modules can present a number of significant challenges. For example, in some instances the optical power and heat generated by a laser diode could be sufficient to degrade the phosphor matrix thereby reducing the light conversion efficiency (i.e., quantum yield) of the phosphor or generating an undesirable chromatic shift in the converted light emission. Some of the aforementioned are well-established challenges observed in light conversion modules utilizing LEDs characterized by even moderately low optical power. Further, the aforementioned challenges can be particularly acute for light sources configured to emit ultraviolet light, wherein certain chemical bonds within the matrix molecules (e.g., the bonds in silicone to methyl functional groups) may be particularly susceptible to degradation. Finally, light sources with high optical power, such as laser diodes, may present a human eye-safety risk. 
       SUMMARY 
       [0005]    The present disclosure describes light conversion modules each having a single laser diode or multiple laser diodes. The light conversion modules can be particularly small in size (height and lateral footprint) and can overcome various challenges associated with the high optical power and heat emitted by laser diodes. In some implementations, the light conversion modules include glass phosphors, which, in some instances, can resist degradation caused by the optical power and/or heat generated by the laser diodes. In some instances, the light conversion modules include optical filters which, in some instances, can reduce or eliminate human eye-safety risk. The light conversion modules in the present disclosure can be suitable for a number of applications; for example, a camera flash, as integrated in smartphone, tablet or other portable devices; interior lighting; and automotive head-lighting. 
         [0006]    Other aspects, features and advantages will be readily apparent from the following detailed description, the accompanying drawings and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIGS. 1A-1C  depict an example of a light conversion module including a single laser diode. 
           [0008]      FIGS. 2A-2C  depict an example of a light conversion module including multiple laser diodes. 
           [0009]      FIGS. 3A-3C  depict another example of a light conversion module including a single laser diode. 
           [0010]      FIG. 4A  and  FIG. 4B  depict another example of a light conversion module. 
           [0011]      FIG. 5  depicts yet another example of a light conversion module. 
           [0012]      FIG. 6  depicts still yet another example of a light conversion module. 
           [0013]      FIGS. 7A-7C  depict still yet another example of a light conversion module 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1A - FIG. 1C  depict an example light conversion module  100  including a single laser diode  101 . The laser diode  101  can be implemented, for example, as a vertical-cavity surface-emitting laser diode, an edge-emitting laser, or an array of vertical-cavity surface-emitting laser diodes or edge-emitting diodes. The laser diode  101  is operable to generate a light emission  103  of a particular wavelength or range of wavelengths. For example, in some instances the light emission  103  can be infrared or ultraviolet (e.g., 405 nm). 
         [0015]    The light conversion module  100  further includes a light conversion assembly  105 . The light conversion assembly  105  includes a holder  107 , at least one optically active surface  109 , and a light conversion material  111 . The holder  107  can be configured to hold or contain the light conversion material  111  and at least one interior surface of the holder  111  can be an optically active surface  109 . The optically active surface  109  can be reflective and/or diffusive. For example, in some instances the optically active surface  109  can be a metal with particularly high reflectivity. In some instances the optically active surface  109  can be composed, at least partially, of a white material such as titanium or zinc oxide. Further, the holder  107  and/or optically active surface  109  can be configured to transmit the light emission  103  such that the light emission  103  illuminates the light conversion material  111 . 
         [0016]    The light conversion material  111  can be any material that is capable of converting the light emission  103  to a converted light emission  113  of another wavelength. For example, the light conversion material  111  can be a phosphor, a fluorescent material, luminescent material, and/or any other organic or inorganic semiconductor. Further, the light conversion material  111  can include a matrix composed, at least in part, from material such as silicone or another polymer in some implementations. In some implementations the light conversion material  111  can include a matrix composed, at least in part, from inorganic glasses such as silicate-, sodium-, borate-, and/or tellurite-glasses. Other matrixes are within the scope of the present disclosure such as matrices composed, at least in part, of materials exhibiting good optical transmittance, thermal stability, high thermal conductivity, and low thermal expansion coefficients. In some instances the light conversion material  111  can be Ce 3+ :YAG doped sodium glass (CE YDG). 
         [0017]    The holder  107  can be disposed relative to the laser diode  101 , such that the light emission illuminates the light conversion material  111 , wherein the light conversion material  111  generates the converted light emission  113 . Further, the holder  107  and/or the optically active surface  109  can be operable to transmit the converted light emission  113 . In some implementations the holder  107  can be composed of epoxy or another polymer, and can be formed via a wafer-level process such as vacuum injection molding, injection molding, or other molding techniques. The holder  107  can be coated, in some implementations, with a layer of metal to form the optically active surface  109 . The holder  107  and/or the optically active surface  109  are operable to direct (e.g., focus) the light emission  103  and/or the converted light emission  113  through the holder  107  in order to achieve high conversion efficiency. For example, in some implementations, the holder  107  and/or the optically active surface  109  can be parabolic or trough shaped as depicted in  FIGS. 1A-1C , wherein the parabolic or trough shape permits recycling of the light emission  103  throughout the light conversion assembly  105  and/or focusing of the light emission  113  to an optical assembly  116 . 
         [0018]    Accordingly, the converted light emission  113  is incident on the optical assembly  116  as illustrated in  FIG. 1B  and  FIG. 1C . The optical assembly  116  can be operable to direct the converted light emission  113  over a pre-defined field-of-illumination as a directed light emission  118 . In some implementations the optical assembly  116  is operable to focus the converted light emission  113  while in other instances the optical assembly  116  is operable to de-magnify the converted light emission  113 . The optical assembly  116  can include refractive and/or diffractive optical elements and/or array of refractive and/or diffractive optical elements (e.g., a microlens array), in some implementations. In some implementations the optical assembly  116  can be a diffuser. 
         [0019]      FIG. 2A - FIG. 2C  depict an example light conversion module  200  including multiple laser diodes  201 ,  202 . The laser diodes  201 ,  202  can be implemented, for example, as vertical-cavity surface-emitting laser diodes, edge-emitting lasers, or arrays of vertical-cavity surface-emitting laser diodes or edge-emitting diodes. The laser diodes  201 ,  202  are each operable to generate light emissions  203 ,  204 , respectively, each of a particular wavelength or range of wavelengths. For example, in some instances the light emissions  203 ,  204  can be infrared or ultraviolet (e.g., 405 nm). In some implementations, the lasers diodes  201 ,  202  can each be operable to generate light emissions  203 ,  204 , respectively, each having the same or different wavelengths or ranges of wavelengths. The light conversion module of the present disclosure is not limited to two lasers diodes as depicted in  FIG. 2  and could include more than two laser diodes in other implementations. 
         [0020]    The light conversion module  200  further includes light conversion assemblies  205 ,  206 . The light conversion assemblies  205 ,  206  each include holders  207 ,  208 , respectively, at least one optically active surface  209 ,  210 , respectively, and light conversion materials  211 ,  212 , respectively. The holders  207 ,  208  can each be configured to hold or contain light conversion materials  211 ,  212 , respectively; and at least one interior surface of each of the holders  211 ,  212 , respectively can be optically active surfaces  209 ,  210 , respectively. The optically active surfaces  209 ,  210  can each be reflective and/or diffusive. For example, in some instances the optically active surfaces  209 ,  210  can each be metal with particularly high reflectivity. In some instances the optically active surfaces  209 ,  210  can each be composed, at least partially, of a white material such as titanium or zinc oxide. Further, the holders  207 ,  208  and/or respective optically active surfaces  209 ,  210  can each be configured to transmit the light emissions  203 ,  204 , respectively, such that the light emissions  203 ,  204  each illuminate the light conversion materials  211 ,  212 , respectively. 
         [0021]    The light conversion materials  211 ,  212  can each be any material that is capable of converting the light emissions  203 ,  204  to converted light emissions  213 ,  214 , respectively, of another wavelength. For example, the light conversion materials  211 ,  212  can each be a phosphor, a fluorescent material, luminescent material, and/or any other organic or inorganic semiconductor. Further, the light conversion materials  211 ,  212  can each include a matrix composed, at least in part, from material such as silicone or another polymer in some implementations. In some implementations the light conversion materials  211 ,  212  can each include a matrix composed, at least in part, from inorganic glasses such as silicate-, sodium-, borate-, and/or tellurite-glasses. Other matrixes are within the scope of the present disclosure such as matrices composed, at least in part, of materials exhibiting good optical transmittance, thermal stability, high thermal conductivity, and low thermal expansion coefficients. In some instances the light conversion materials  211 ,  212  can each be Ce 3+ :YAG doped sodium glass (CE YDG). 
         [0022]    The holders  207 ,  208  can each be disposed relative to the laser diodes  201 ,  202 , respectively, such that each of the light emissions  203 ,  204  illuminate the light conversion materials  211 ,  212 , respectively, wherein the light conversion materials  211 ,  212  each generate the converted light emissions  213 ,  214 , respectively. Further, each of the holders  207 ,  208  and/or the respective optically active surfaces  209 ,  210  can be operable to transmit the converted light emissions  213 ,  214 , respectively. In some implementations each of the holders  207 ,  208  can be composed of epoxy or another polymer, and can be formed via a wafer-level process such as vacuum injection molding, injection molding, or other molding techniques. Each of the holders  207 ,  208  can be coated, in some implementations, with a layer of metal to form the optically active surfaces  209 ,  210 , respectively. The holders  207 ,  208  and/or the optically active surfaces  209 ,  210  are operable to respectively direct (e.g., focus) the light emissions  203 ,  204  and/or the converted light emissions  213 ,  214  through the holders  207 ,  208  in order to achieve high conversion efficiency. For example, in some implementations, the holders  207 ,  208  and/or the optically active surfaces  209 ,  210  can be parabolic or trough shaped as depicted in  FIGS. 2A-2C , wherein the parabolic or trough shape permits recycling of the light emissions  203 ,  204  throughout the light conversion assemblies  205 ,  206  and/or focusing of the light emissions  213 ,  214  to an optical assembly  216 . 
         [0023]    Accordingly, the converted light emissions  213 ,  214  are each incident on the optical assembly  216  as illustrated in  FIG. 2B  and  FIG. 2C . The optical assembly  216  can be operable to direct the converted light emissions  213 ,  214  over a pre-defined field-of-illumination as a directed light emission  218 . In some implementations the optical assembly  216  is operable to focus the converted light emission  213  while in other instance the optical assembly  216  is operable to de-magnify the converted light emission  213 . The optical assembly  216  can include refractive and/or diffractive optical elements or/and array of refractive and/or diffractive optical elements (e.g., microlens array), in some implementations. In some implementations the optical assembly  216  can be a diffuser. In some implementations the optical assembly can homogenize the converted light emissions  213 ,  214 . 
         [0024]      FIGS. 3A-3C  depict another example of a light conversion module  300  including a single laser diode  301 . The light conversion module  300  operates in a similar way to the light conversion modules disclosed above. Accordingly, the light conversion module includes a laser diode  301  operable to generate a light emission  303 , a light conversion assembly  305 , a holder  307 , an optically active surface  309 , a light conversion material  311  operable to convert the light emission  303  to a converted light emission  313 , an optical assembly  316 , and a directed light emission  318 . However, the light conversion module  300  illustrated in  FIGS. 3A-3C  includes an optical filter  315 . The optical filter  315  can be implemented as a long-pass optical filter wherein light of a long wavelength (e.g., converted light emission  313 ) is permitted to pass and illuminate the optical assembly  316  in some implementations. The optical filter  315  can reflect light of a short wavelength (e.g., the light emission  303 ). The optical filter  315  can improve efficiency in some instances by recycling portions of the light emission  303  that are not converted to the converted light emission  313 . In some instances the optical filter  315  can improve eye-safety. 
         [0025]      FIGS. 4A-4C  depict another example of a light conversion module  400  including a laser diode  401 . The light conversion module  400  operates in a similar way to the light conversion modules disclosed above. However, the laser diode  401  is operable to generate both a first light emission  403  and a second light emission  404 . In some implementations the optical power of the first and second light emissions  403 ,  404  can be different or the same. In some implementations the wavelength or range of wavelengths of the first light emission  403  and second light emission  404  can be different or the same. 
         [0026]    The light conversion module  400  includes light conversion assemblies  405 ,  406 , holders  407 ,  408 , optically active surfaces  409 ,  410 , light conversion materials  411 ,  412  operable to respectively convert the first light emission  403  and the second light emission  404  to respective converted light emissions  413 ,  414 , optical assemblies  416 ,  417  operable to respectively direct the first and second converted light emissions  413 ,  414  thereby generating directed light emissions  418 ,  419 . In some implementations the light conversion materials  411 ,  412  can be different or the same. In implementations where the light conversions materials  411 ,  412  are different (i.e., their respective converted light emissions  413 ,  414  are composed of different wavelengths or ranges of wavelengths), the directed light emissions  418 ,  419  can be tuned to achieve a more functionally suited or aesthetically pleasing affect. 
         [0027]      FIG. 5  depicts another example of a light conversion module  500  including a laser diode  501 . The light conversion module  500  operates in a similar way to the light conversion modules disclosed above, for example, the laser diode  501  is operable to generate a light emission  503 . However, the light conversion module  500  includes a modulator  520 . The light conversion module  500  further includes two light conversion assemblies  505 ,  506 . The modulator  520  is operable to modulate and/or direct the light emission  503  to either one or both the light conversion assemblies  505 ,  506 . Each light conversion assembly  505 ,  506 , respectively include holders  507 ,  508 , optically active surfaces  509 ,  510 , light conversion materials  511 ,  512 , respectively operable to convert light emissions  503 ,  504  into converted light emissions  513 ,  514 . A single contiguous optical assembly disposed over light conversion assemblies  505 ,  506  or two dedicated optical assemblies disposed over light conversion assemblies  505 ,  506 , respectively, are not depicted in  FIG. 5 . In some implementations the light conversion materials  511 ,  512  can be different or the same. In implementations where the light conversion materials  511 ,  512  are different (i.e., their respective converted light emissions  513 ,  514  are composed of different wavelengths or ranges of wavelengths), the directed light emissions (not depicted in  FIG. 5 ) can be tuned via the modulator  520  to achieve a more functionally suited or aesthetically pleasing affect. 
         [0028]      FIG. 6  depicts still yet another example of a light conversion module  600 . The light conversion module  600  operates in a similar way to the light conversion modules disclosed above. Accordingly, during operation the light conversion module includes a laser diode  601  operable to generate a light emission  603 , a light conversion assembly  605 , a holder  607 , an optically active surface  609 , a light conversion material  611  operable to convert the light emission  603  to a converted light emission  613 , an optical assembly  616  operable to direct the converted light emission  613  to a directed light emission  618 . However, the light conversion assembly  605  is configured as an L-shaped light conversion assembly  605 . In some implementations the L-shaped conversion assembly  605  can increase the volume of light conversion material  611  within the light conversion assembly  605  without increasing the lateral footprint of the light conversion module  600 . 
         [0029]      FIGS. 7A-7C  depicts still yet another example of a light conversion module  700 . The light conversion module  700  operates in a similar way to the light conversion modules disclosed above. Accordingly, during operation the light conversion module includes a laser diode  701  operable to generate a light emission  703 , a light conversion assembly  705 , a holder  707 , an optically active surface  709 , and a light conversion material  711  operable to convert the light emission  703  to a converted light emission  713 . The light conversion module  700  further includes an optical assembly  716 , and a directed light emission  718 . In the example depicted in  FIGS. 7A-7C , the light conversion material  711  is adjacent to the optical assembly  716 , and not within the holder  707  as depicted in previous examples. Moreover, the converted emission  713  and the directed light emission  718  are depicted as being coincident in this example as the light conversion material  711  is adjacent to the optical assembly  716 . In some implementations, such a configuration can permit use of a smaller volume of the light conversion material  711 . 
         [0030]    Various modifications can be made within the spirit of the present disclosure. For example, an optical filter could be implemented with any of the implementations disclosed above. Accordingly, other implementations are within the scope of the claims.