Patent Publication Number: US-11644611-B2

Title: LED light source

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/070,797, filed on Oct. 14, 2020, now allowed, which itself is a continuation of U.S. patent application Ser. No. 16/594,246, filed on Oct. 7, 2019, issued as U.S. Pat. No. 10,859,756 on Dec. 8, 2020, which itself is a continuation of U.S. patent application Ser. No. 15/491,238, filed on Apr. 19, 2017, issued as U.S. Pat. No. 10,514,489 on Dec. 24, 2019, all of which are herein incorporated by reference in their entirety. 
    
    
     FIELD 
     This application relates to the field of LED light sources and apparatus including the same. 
     INTRODUCTION 
     A light-emitting diode (LED) is a semiconductor light source that emits light when activated. Generally, LEDs have lower energy consumption and longer lifespans as compared with traditional light sources, such as incandescent and halogen lights. 
     SUMMARY 
     In one aspect, a LED light source is provided. The LED light source, may include a longitudinally extending first light guide, a housing, and a cartridge. The first light guide having a longitudinally extending light emitting face, the light emitting face having a first end face and a longitudinally spaced apart second end face. The housing having a first recess, the recess having a first side proximate the first end face of the first light guide and a longitudinally spaced apart opposed face, the first recess extending generally transverse to the first light guide from an insertion end to a transversely spaced apart inner end. The cartridge slideably receivable in the first recess and having a plurality of LEDs on a first face of the cartridge, the first face extending generally transverse to the first light guide when the cartridge has been inserted into the first recess, the first face having an inner end and an outer end. The cartridge may be movable from an insertion position in which the inner end of the first face of the cartridge is spaced from the first side of the first recess when the inner end of the first face of the cartridge is positioned at the insertion end, to an inserted position in which the first face of the cartridge is adjacent the first side of the first recess when the cartridge is inserted into the first recess. 
     In some embodiment, the LED light source further includes a biasing member biasing the cartridge to the inserted position. 
     In some embodiments, the first recess includes a cam member whereby, as the cartridge is inserted into the first recess, the cartridge is guided towards the inserted position. 
     In some embodiments, the LED light source may further include a biasing member biasing the cartridge to the inserted position. 
     In some embodiments, the cartridge is rigid and the biasing member is provided at the inner end of the first recess whereby a biasing force provided by the biasing member when the cartridge is in the inserted position biases the outer end of the cartridge to a position proximate the light guide. 
     In some embodiments, the LED light source may further include a driving member moveably mounted in the housing and driving the cartridge from a position in which the first face of the cartridge is spaced from the first side of the first recess to the inserted position. 
     In some embodiments, the LEDs are provided only on the first face of the cartridge. 
     In some embodiments, the LED light source may further include a second light guide having an first end face and a longitudinally extending light emitting face, wherein the first recess has a third side proximate the first end face of the second light guide and the LEDs are also provided on a second face of the cartridge, wherein when the cartridge is in the inserted position, the second face of the cartridge is adjacent the third side of the first recess. 
     In some embodiments, the light guides extend in different directions. 
     In some embodiments, the light guides extend in different directions that re about 90° apart. 
     In some embodiments, the cartridge further includes a heat sink. 
     In some embodiments, the cartridge further includes the heat sink. 
     In some embodiments, the cartridge further includes a substrate, the LEDs are provided on the substrate and the substrate is removable from the heat sink. 
     In some embodiments, the heat sink is provided in the housing and the cartridge has a side in thermal contact with the heat sink when the cartridge is in the inserted position. 
     In some embodiments, the LED light source may further include a second light guide extending in the same direction as the first light guide, the second light guide having a first end face and a longitudinally extending light emitting face oriented in the same direction as the light emitting face of the first light guide, and the housing further includes a second recess which slideably receives another cartridge having LEDs on a face thereof. 
     In some embodiments, the second recess is positioned proximate the first recess and, when inserted the LEDs of the first cartridge face an opposed direction to the LEDs of the second cartridge. 
     In some embodiments, the second recess is positioned spaced from the first recess and, when inserted the LEDs of the first cartridge face a first direction and the LEDs of the second cartridge face the first direction. 
     In some embodiments, the LED light source may further include a second recess positioned at the second end face of the first light emitting member and, when inserted, the LEDs of the first cartridge face an opposed direction to the LEDs of the second cartridge. 
     In another aspect, a LED light source is provided. The LED light source includes a longitudinally extending first light guide, a housing, and a cartridge. The first light guide has a longitudinally extending light emitting face, the light emitting face having a first end face and a longitudinally spaced apart second end face. The housing has a first side proximate the first end face of the first light guide. The cartridge is mountable to the first side of the housing and has at least one LED on a first face of the cartridge, the first face extending generally transverse to the first light guide when the cartridge has been mounted to the housing. When the cartridge is mounted to the first side of the housing, the first face of the cartridge is adjacent the first end face. 
     In some embodiments, the cartridge has mechanical engagement members which are releasably securable to mating mechanical engagement members of the housing. 
     In some embodiments, the LED light source may further include at least one screw member that releasably secures the cartridge to the first side of the housing. 
     In some embodiments, the screw members are non-removably secured to the housing. 
     In another aspect, a LED light bulb is provided. The LED light bulb may include an engagement end electrically connectable to a socket; a housing having a light transmitting surface and an interior; and, a cartridge removably receivable in the interior and having a plurality of LEDs. 
     In some embodiments, the LED light bulb has a first recess, the recess having an insertion end proximate an outer surface of the LED light bulb and a longitudinally spaced apart inner end and the cartridge is slideably receivable in the first recess. 
     In some embodiments, the plurality of LEDs are provided on a first face of the cartridge. 
     In some embodiments, the LEDs are provided on a plurality of faces of the cartridge. 
     In some embodiments, the cartridge is generally cylindrical in shape. 
     In some embodiments, the recess is provided in the engagement end. 
     In some embodiments, the recess is provided in the housing. 
     In some embodiments, the housing includes a light guide and the LEDs are positioned against an end of the light guide when installed in the LED light bulb. 
     In some embodiments, all of an exterior of the housing is made of a material having a light transmitting surface. 
     In some embodiments, the LED light bulb is in the shape of an incandescent or halogen light bulb. 
     In another aspect, a LED light source is provided. The LED light source may include a longitudinally extending light guide having a longitudinally extending light emitting face having a length, a first end face and a longitudinally spaced apart second end face and a LED light source is provided at least at the first end face. The light emitting face has a plurality of light emitting locations provided thereon. The density of the light emitting locations increases from the first end face towards the second end face. 
     In some embodiments, a first LED light source is provided at the first end face and a second LED light source is provided at the second end face wherein the density of the light emitting locations increases from each of the first end face and the second end face to a middle of the light emitting face. 
     In some embodiments, the light emitting locations are positioned to provide a generally even level of illumination along the length of the light emitting surface. 
     In some embodiments, a level of illumination provided at the middle of the light emitting surface is ±20% of a level of illumination provided at the first end face. 
     In some embodiments, a level of illumination provided at the middle of the light emitting surface is ±10% of a level of illumination provided at the first end face. 
     In some embodiments, an image is provided in front of at least a portion of the light emitting face and the light emitting locations are positioned such that a person viewing the image views a generally evenly illuminated image. 
     In some embodiments, the image has at least area that has at least one of a different colour or a different density of the image and the light emitting locations are positioned such that a person viewing the image views a generally evenly illuminated image. 
     In some embodiments, the LED light source is provided only at the first end face wherein the density of the light emitting locations increases from the first end face to the second end face. 
     In some embodiments, the light emitting locations are positioned to provide a generally even level of illumination along the length of the light emitting surface. 
     In some embodiments, a level of illumination provided at the second end face of the light emitting surface is ±20% of a level of illumination provided at the first end face. 
     In some embodiments, a level of illumination provided at the second end face of the light emitting surface is ±10% of a level of illumination provided at the first end face. 
     In some embodiments, the light emitting locations comprise discontinuities provided in the light emitting face. 
     In some embodiments, the light emitting locations comprise a light scattering material applied to the light emitting surface. 
     In some embodiments, the light emitting locations comprise a fluorescent material. 
     In another aspect, a frame for a work of art is provided. The frame may include at least one side panel extending around a perimeter and defining an inner opening in which the work of art is displayable. The at least one side panel may include a longitudinally extending light guide having a longitudinally extending light emitting face that faces inwards towards another portion of the at least one side panel. The longitudinally extending light emitting face has a length, a first end face and a longitudinally spaced apart second end face and a LED light source is provided at least at the first end face. The light emitting face has a plurality of light emitting locations provided thereon. The density of the light emitting locations increases from the first end face towards the second end face. 
     In some embodiments, the fame is in the shape of a parallelogram and includes four side panels, each of which includes a longitudinally extending light guide having a light emitting face that faces onwards. 
     In some embodiments, each light emitting face has an inner side positioned proximate a plane in which the work of art seats when mounted in the frame and a spaced apart outer side and the inner side is position forward of the plane. 
     In some embodiments, the light emitting face has an inner side positioned proximate a plane in which the work of art seats when mounted in the frame and a spaced apart outer side and the inner side is position forward of the plane. 
     In some embodiments, a first LED light source is provided at the first end face and a second LED light source is provided at the second end face wherein the density of the light emitting locations increases from each of the first end face and the second end face to a middle of the light emitting face. 
     In some embodiments, the LED light source is provided only at the first end face wherein the density of the light emitting locations increases from the first end face to the second end face. 
     In another aspect, a backlight frame for a work of art is provided. The backlight frame may include a frame member extending around a perimeter and defining an inner opening in which the work of art is displayable, and a longitudinally extending light guide positioned rearward of the opening and facing towards the opening. The longitudinally extending light guide has a longitudinally extending light emitting face having a length, a first end face and a longitudinally spaced apart second end face and a LED light source is provided at least at the first end face. The light emitting face has a plurality of light emitting locations provided thereon. The density of the light emitting locations increases from the first end face towards the second end face. 
     In some embodiments, a first LED light source is provided at the first end face and a second LED light source is provided at the second end face wherein the density of the light emitting locations increases from each of the first end face and the second end face to a middle of the light emitting face. 
     In some embodiments, the LED light source is provided only at the first end face wherein the density of the light emitting locations increases from the first end face to the second end face. 
     In some embodiments, the work of art that transmits light is provided in front of at least a portion of the light emitting face and the light emitting locations are positioned such that a person viewing the work of art views a generally evenly illuminated work of art. 
     In some embodiments, the work of art has at least area that has at least one of a different colour or a different density of the image and the light emitting locations are positioned such that a person viewing the work of art views a generally evenly illuminated work of art. 
     In some embodiments, the light emitting locations comprise a fluorescent material. 
     In another aspect, a frame for a work of art is provided. The frame may include at least one side panel defining an inner opening in which the work of art is displayable, the inner opening extending in a plane, the at least one side panel including a longitudinally extending light guide having a longitudinally extending light emitting face that faces inwards towards the inner opening in a direction generally parallel to the plane. The light emitting face has an inner side positioned proximate the plane and a spaced apart outer side and at least one LED providing a light source for the light guide. 
     In some embodiments, the inner side of the light emitting face is spaced from the plane. 
     In some embodiments, the inner side of the light emitting face is spaced from 0.25 to 1 inch from the plane. 
     In some embodiments, the light guide has a first end face and a longitudinally spaced apart second end face and the light source is provided at least at the first end face. 
     In some embodiments, a first light source is provided at the first end face and a second light source is provided at the second end face. 
     In some embodiments, the fame is in the shape of a parallelogram and includes four side panels, each of which includes a longitudinally extending light guide having a longitudinally extending light emitting face that faces inwards towards the inner opening in a direction generally parallel to the plane, each light emitting face has an inner side positioned proximate the plane and a spaced apart outer side. 
     In some embodiments, the light emitting faces are positioned forward of the plane. 
     In some embodiments, the fame includes a plurality of side panels which meet at corners, at least some of the side panels comprise a longitudinally extending light guide having a longitudinally extending light emitting face that faces inwards towards the inner opening in a direction generally parallel to the plane, each light emitting face has a first end face and a longitudinally spaced apart second end face and the light source is provided at least at the first end face, wherein the light sources are provided in corners of the parallelogram. 
     In some embodiments, the fame is in the shape of a parallelogram, each of the side panels includes a longitudinally extending light guide and the light sources are provided in the corners of the parallelogram. 
     In some embodiments, the frame may further include a sensor that detects a condition in a space in front of a location in which the frame is located and a controller that adjusts at least one of a level of intensity of light emitted by the light source and the colour of light emitted by the light source based upon a signal provided by the sensor. 
     In some embodiments, the condition includes at least one of a level of illumination, a colour of illumination, motion of a body, a noise level, a signal issued by a person. 
     In some embodiments, the light source includes LEDs of at least two different colours. 
     In some embodiments, the frame may further include a manually actuatable switch operatively connected to the light source wherein operation of the switch adjusts at least one of a level of intensity of light emitted by the light source and the colour of light emitted by the light source based upon a signal provided by the switch. 
     In some embodiments, the frame may further include an energy storage member. 
     In some embodiments, the energy storage member includes a rechargeable battery. 
     In some embodiments, the at least one LED is operable to selectively emit one or more colours of light. 
     In some embodiments, the at least one LED is operable to selectively illuminate part of a work of art placed in the fame. 
     In another aspect, a backlight frame for a work of art is provided. The backlight frame may include a frame member that defines an inner opening in which the work of art is displayable, the inner opening extending in a plane, and a longitudinally extending light guide positioned rearward of the opening and facing towards the opening. The longitudinally extending light guide has a longitudinally extending light emitting face spaced rearward of the plane and having a length, a first end face and a longitudinally spaced apart second end face and a LED light source is provided at least at the first end face. 
     In some embodiments, the light emitting face is spaced rearward from the plane. 
     In some embodiments, the light emitting face is spaced from 0.25 to 1 inch from the plane. 
     In some embodiments, the light guide has a first end face and a longitudinally spaced apart second end face and the LED light source is provided at least at the first end face. 
     In some embodiments, a first light source is provided at the first end face and a second light source is provided at the second end face. 
     In some embodiments, the frame may further include a sensor that detects a condition in a space in front of a location in which the frame is located and a controller that adjusts at least one of a level of intensity of light emitted by the light source and the colour of light emitted by the light source based upon a signal provided by the sensor. 
     In some embodiments, the condition includes at least one of a level of illumination, a colour of illumination, motion of a body, a noise level, a signal issued by a person. 
     In some embodiments, the light source includes LEDs of at least two different colours and 
     In some embodiments, the frame may further include a manually actuatable switch operatively connected to the light source wherein operation of the switch adjusts at least one of a level of intensity of light emitted by the light source and the colour of light emitted by the light source based upon a signal provided by the switch. 
     In some embodiments, the frame may further include an energy storage member. 
     In some embodiments, the energy storage member includes a rechargeable battery. 
     In some embodiments, the at least one LED is operable to selectively emit one or more colours of light. 
     In some embodiments, the at least one LED is operable to selectively illuminate part of a work of art placed in the fame. 
     In another aspect, a LED light source is provided. The LED light source may include a longitudinally extending light guide, at least one LED, and a diffuser. The longitudinally extending light guide may have a first longitudinally extending light emitting face, the first light emitting face having a first end face, a longitudinally spaced apart second end face, and first and second side faces extending between the first and second end faces. The at least one LED is provided at the first end face. The diffuser includes a central panel that is spaced from and facing the first light emitting face. 
     In some embodiments, the central panel of the diffuser is positioned from 0.25 to 3 inches from the light emitting surface. 
     In some embodiments, the diffuser is composed of at least one of acrylic, polypropylene and polycarbonate, wherein the diffuser is at least translucent. 
     In some embodiments, the diffuser extends over the first and second side faces and the light emitting face. 
     In some embodiments, the diffuser is white. 
     In some embodiments, the central panel has a first end, a longitudinally spaced apart second end, and first and second sides each of which extends longitudinally between the first and second ends, and the diffuser further includes a first side panel extending between the first and second ends the central panel and provided on the first side of the central panel and a second side panel extending between the first and second ends the central panel and provided on the second side of the central panel. 
     In some embodiments, the light guide has a second light emitting face spaced from and opposed to the first light emitting face and facing in a direction opposed to a direction that the first light emitting member faces. 
     In some embodiments, the light guide has a longitudinally extending rear face spaced from and opposed to the first light emitting face, and the LED light source further includes a reflector facing the rear face. 
     In some embodiments, the reflector is spaced from the rear face. 
     In some embodiments, the reflector abuts the rear face. 
     In some embodiments, the reflector has a surface facing the rear face, wherein the surface is provided with a white coating. 
     In some embodiments, the white coating includes titanium dioxide. 
     In some embodiments, the LED light source may further include an image provided in front of the light emitting face, the image having at least one portion that has one or more of a different colour or light transmissivity, wherein a surface of the reflector facing the light guide has more than one colour and the colours are positioned to enhance the image when viewed by a user. 
     In some embodiments, a portion of the reflector has a colour selected to increase the visibility of the portion of the image. 
     In some embodiments, the reflector has a surface facing the rear face, wherein the surface is provided with a UV paint or fluorescent paint. 
     In some embodiments, the at least one LED is operable to selectively emit one or more colours of light. 
     In another aspect, a LED light source is provided. The LED light source includes a longitudinally extending light guide, at least one LED, and a reflector. The longitudinally extending light guide having a first longitudinally extending light emitting face, a longitudinally extending rear face spaced from and opposed to the first light emitting face, the first light emitting face having a first end face, a longitudinally spaced apart second end face, and first and second side faces extending between the first and second end faces. The at least one LED is provided at the first end face. The reflector faces the rear face. 
     In some embodiments, the reflector is spaced from the rear face. 
     In some embodiments, the reflector abuts the rear face. 
     In some embodiments, the reflector has a surface facing the rear face, wherein the surface is provided with a white coating. 
     In some embodiments, the white coating includes titanium dioxide. 
     In some embodiments, the white reflector has a surface facing the rear face, wherein the surface is provided with a UV paint. 
     In some embodiments, the LED light source may further include an image provided in front of the light emitting face, the image having at least one portion that has one or more of a different colour or light transmissivity, wherein a surface of the reflector facing the light guide has more than one colour and the colours are positioned to enhance the image when viewed by a user. 
     In some embodiments, a portion of the reflector has a colour selected to increase the visibility of the portion of the image. 
     In some embodiments, the at least one LED is operable to selectively emit one or more colours of light. 
     In another aspect, a LED light source is provided including a longitudinally extending light guide, and a power supply. The longitudinally extending light guide has a first end face and a longitudinally spaced apart second end face and at least one LED provided at the first end face. The power supply includes a plurality of batteries operatively connected to the at least one LED in a first mode in which the power supply provides a first power to the at least one LED and a second mode in which the power supply provides a second power different to the first power to the at least one LED. 
     In some embodiments, in the first mode, two or more of the batteries are connected in series. 
     In some embodiments, in the second mode, two or more of the batteries are connected in parallel. 
     In some embodiments, the plurality of batteries comprise a first battery and a second battery and, in the first mode, the first and second batteries are connected in series. 
     In some embodiments, in the second mode, the first and second the batteries are connected in parallel. 
     In some embodiments, the LED light source may further include a circuit which includes a sensor and the power supply whereby, when the sensor senses a condition, the sensor issues a signal which causes the power supply to change from the first mode to the second mode. 
     In some embodiments, the sensor includes a motion sensor. 
     In some embodiments, the sensor includes a noise sensor. 
     In some embodiments, the sensor includes a light intensity sensor. 
     In some embodiments, the LED light source may further include a manually operable switch operatively connected to the power supply, the switch having a first position in which the power supply is in the first mode and a second position in which the power supply is in the second mode. 
     In another aspect, a LED light source is provided. The LED light source includes a circuit including a plurality of LEDs. The LEDs are connected in parallel and each of the plurality of LEDs is individually electrically connected to the circuit by a meltable electrically conductive member. 
     In some embodiments, the meltable electrically conductive member includes fuse wire. 
     In some embodiments, the meltable electrically conductive member melts at a temperature corresponding to a temperature produced by a current drawn by a failed LED through the meltable electrically conductive member. 
     In some embodiments, the meltable electrically conductive member melts at a temperature above about 80C. 
     In some embodiments, the meltable electrically conductive member includes fuse wire. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an LED light source in accordance with an embodiment; 
         FIG.  2    is an exploded view of the LED light source of  FIG.  1   ; 
         FIG.  3    is an exploded view of a housing end member of the LED light source of  FIG.  1   ; 
         FIG.  4    is a cross-sectional view taken along line  4 - 4  in  FIG.  1   ; 
         FIG.  5    is a cross-sectional view taken along line  5 - 5  in  FIG.  1    and showing a cartridge in an inserted position; 
         FIG.  6    is a cross-sectional view taken along line  5 - 5  in  FIG.  1    and showing the cartridge in an insertion position; 
         FIG.  7    is a cross-sectional view taken along line  5 - 5  in  FIG.  1    and showing the cartridge being removed; 
         FIG.  8    is an exploded view of a housing end member in accordance with another embodiment; 
         FIG.  9    is a cross-sectional view of the housing end member of  FIG.  8   , showing the cartridge in an inserted position; 
         FIG.  10    is a cross-sectional view of the housing end member of  FIG.  8   , showing the cartridge in an insertion position; 
         FIG.  11    is a cross-sectional view of the housing end member of  FIG.  8   , showing the cartridge being removed; 
         FIG.  12    is a cross-sectional view of an LED light source having the housing end member of  FIG.  8   , and showing the cartridge in an inserted position. 
         FIG.  13 A  is a perspective view of a housing end member in accordance with another embodiment; 
         FIG.  13 B  is an exploded view of the housing end member of  FIG.  13 A ; 
         FIG.  14    is a cross-sectional view taken along line  14 - 14  in  FIG.  13 A , showing a cartridge in an inserted position and a driving member in a first position; 
         FIG.  15    is a cross-sectional view taken along line  14 - 14  in  FIG.  13 A , showing the cartridge in an insertion position and the driving member in a second position; 
         FIG.  16    is a perspective view of the housing end member of  FIG.  13 A  showing the driving member in the second position and the cartridge removed; 
         FIG.  17    is an exploded view of a housing end member in accordance with another embodiment; 
         FIG.  18    is a cross-sectional view of the housing end member of  FIG.  17   , showing a cartridge in an inserted position and a driving member in a first position; 
         FIG.  19    is a cross-sectional view of the housing end member of  FIG.  17   , showing the cartridge in an insertion position and the driving member in a second position; 
         FIG.  20    is a cross-sectional view of an LED light source in accordance with another embodiment; 
         FIG.  21    is an exploded view of a housing end member of the LED light source of  FIG.  20   ; 
         FIG.  22    is a cross-sectional view of the housing end member, taken along line  22 - 22  in  FIG.  20   , showing a cartridge in an inserted position and a driving member in a first position; 
         FIG.  23    is a cross-sectional view of the housing end member, taken along line  23 - 23  in  FIG.  20   , showing the cartridge in the inserted position and the driving member in the first position; 
         FIG.  24    is a cross-sectional view of the housing end member, taken along line  23 - 23  in  FIG.  20   , showing the cartridge in the inserted position and the driving member in an intermediate position; 
         FIG.  25    is a cross-sectional view of the housing end member, taken along line  23 - 23  in  FIG.  20   , showing the cartridge in the inserted position and the driving member in a second position; 
         FIG.  26    is a perspective view of the housing end member of the LED light source of  FIG.  20   , showing the driving member in the second position and the cartridge removed; 
         FIG.  27    is a cross-sectional view of an LED light source in accordance with another embodiment; 
         FIG.  28    is an exploded view of a housing end member of the LED light source of  FIG.  27   ; 
         FIGS.  29 - 30    are cross-sectional views of the housing end member, taken along line  29 - 29  in  FIG.  27   , showing a cartridge in the inserted position and a driving member in a first position; 
         FIG.  31    is a cross-sectional view of the housing end member, taken along line  29 - 29  in  FIG.  27   , showing the cartridge in the inserted position and the driving member in a second position; 
         FIG.  32    is a perspective view of the housing end member of the LED light source of  FIG.  27   , showing the driving member in the second position and the cartridge removed; 
         FIG.  33    is a cross-sectional view of an LED light source in accordance with another embodiment; 
         FIG.  34    is an exploded view of a housing end member of the LED light source of  FIG.  33   ; 
         FIG.  35    is a perspective view of the housing end member of  FIG.  34    in an open condition; 
         FIG.  36    is a perspective view of a housing end member in a closed condition in accordance with another embodiment; 
         FIG.  37    is a perspective view of the housing end member of  FIG.  36    in an open condition; 
         FIG.  38    is a cross-sectional view of an LED light source including the housing end member of  FIG.  36   ; 
         FIG.  39    is a perspective view of a housing end member in a closed condition, in accordance with another embodiment; 
         FIGS.  40 - 41    are perspective views of the housing end member of  FIG.  39    in an open condition; 
         FIG.  42    is a cross-sectional view of an LED light source in accordance with another embodiment; 
         FIG.  43    is an exploded view of a housing end member of the LED light source of  FIG.  42   ; 
         FIG.  44    is a cross-sectional view of the housing end member of  FIG.  43    showing a cartridge in an inserted position; 
         FIG.  45    is a cross-sectional view of the housing end member of  FIG.  43    showing the cartridge in an insertion position; 
         FIG.  46    is a cross-sectional view of the housing end member of  FIG.  43    showing the cartridge being removed; 
         FIG.  47    is a schematic view of a LED light source including one cartridge in one housing end member, in accordance with an embodiment; 
         FIG.  48    is a schematic view of a LED light source including one cartridge in each of two housing end members, in accordance with an embodiment; 
         FIG.  49    is a schematic view of a LED light source including two cartridges in one housing end member, in accordance with an embodiment; 
         FIG.  50    is a schematic view of a LED light source including four cartridges in three housing end members, in accordance with an embodiment; 
         FIG.  51    is a schematic view of a LED light source including four cartridges in four housing end members, in accordance with an embodiment; 
         FIG.  52    is a schematic view of a LED light source including four cartridges in two housing end members, in accordance with an embodiment; 
         FIG.  53    is a schematic view of a LED light source including eight cartridges in two housing end members, in accordance with an embodiment; 
         FIG.  54    is a schematic view of a LED light source including four cartridges in two housing end members, each housing end member including a heat sink, in accordance with an embodiment; 
         FIG.  55    is a perspective view of a LED light source formed as a lightbulb in accordance with an embodiment; 
         FIG.  56    is an exploded view of the LED light source of  FIG.  55   ; 
         FIG.  57    is a cross-sectional view taken along line  57 - 57  in  FIG.  55    showing an open condition and a cartridge removed; 
         FIG.  58    is a cross-sectional view taken along line  57 - 57  in  FIG.  55    showing a closed condition; 
         FIG.  59    is a cross-sectional view taken along line  57 - 57  in  FIG.  55    showing the open condition; 
         FIG.  60    is a perspective view of a LED light source formed as a light bulb in accordance with another embodiment; 
         FIG.  61    is a perspective view of the LED light source of  FIG.  60    with a cartridge removed; 
         FIG.  62    is a cross-sectional view taken along line  62 - 62  in  FIG.  60   ; 
         FIG.  63    is a perspective view of a LED light source formed as a light bulb in accordance with another embodiment; 
         FIG.  64    is a perspective view of the LED light source of  FIG.  63    with a cartridge removed; 
         FIG.  65    is a cross-sectional view taken along line  65 - 65  in  FIG.  63   ; 
         FIG.  66    is a perspective view of a LED light source formed as a light bulb in accordance with another embodiment; 
         FIG.  67    is a perspective view of the LED light source of  FIG.  66    with a cartridge removed; 
         FIG.  68    is a cross-sectional view taken along line  68 - 68  in  FIG.  66   ; 
         FIG.  69    is a perspective view of a LED light source formed as a light bulb in accordance with another embodiment; 
         FIG.  70    is a perspective view of the LED light source of  FIG.  69    with a cartridge removed; 
         FIG.  71    is a cross-sectional view taken along line  71 - 71  in  FIG.  69   ; 
         FIG.  72    is a perspective view of a LED light source formed as a light bulb in accordance with another embodiment; 
         FIG.  73    is a perspective view of the LED light source of  FIG.  72    with a diffuser removed; 
         FIG.  74    is a cross-sectional view taken along line  74 - 74  in  FIG.  72   ; 
         FIG.  75    is a perspective view of a LED light source formed as a light bulb in accordance with another embodiment; 
         FIG.  76    is a perspective view of the LED light source of  FIG.  75    with a diffuser removed; 
         FIG.  77    is a cross-sectional view taken along line  77 - 77  in  FIG.  75   ; 
         FIG.  78    is a perspective view of a LED light source formed as a light bulb in accordance with another embodiment; 
         FIG.  79    is a perspective view of the LED light source of  FIG.  78    with a cartridge removed; 
         FIG.  80    is a cross-sectional view taken along line  80 - 80  in  FIG.  78   ; 
         FIG.  81    is a perspective view of a LED light source formed as a light bulb in accordance with another embodiment; 
         FIG.  82    is a perspective view of the LED light source of  FIG.  81    with a cartridge removed; 
         FIG.  83    is a cross-sectional view taken along line  83 - 83  in  FIG.  81   ; 
         FIG.  84    is a perspective view of a LED light source formed as a light bulb in accordance with another embodiment; 
         FIG.  85    is a perspective view of the LED light source of  FIG.  84    with a cartridge removed; 
         FIG.  86    is a cross-sectional view taken along line  86 - 86  in  FIG.  84   ; 
         FIG.  87    is a perspective view of a LED light source formed as a light bulb in accordance with another embodiment; 
         FIG.  88    is a perspective view of the LED light source of  FIG.  87    with two cartridges removed; 
         FIG.  89    is a cross-sectional view taken along line  89 - 89  in  FIG.  87   ; 
         FIG.  90    is a perspective view of a LED light source in accordance with an embodiment; 
         FIG.  91    is a perspective view of the LED light source of  FIG.  90    with a cartridge removed; 
         FIG.  92    is a cross-sectional view taken along line  92 - 92  in  FIG.  90   ; 
         FIG.  93    is a cross-sectional view taken along line  93 - 93  in  FIG.  90   ; 
         FIG.  94    is a perspective view of a LED light source in accordance with an embodiment; 
         FIG.  95    is a perspective view of the LED light source of  FIG.  94    with three cartridges removed; 
         FIG.  96    is a cross-sectional view taken along line  96 - 96  in  FIG.  94   ; 
         FIG.  97    is a cross-sectional view taken along line  97 - 97  in  FIG.  94   ; 
         FIG.  98    is a perspective view of a LED light source in accordance with an embodiment; 
         FIG.  99    is a perspective view of the LED light source of  FIG.  98    with three cartridges removed; 
         FIG.  100    is a cross-sectional view taken along line A-A in  FIG.  98   ; 
         FIG.  101    is a perspective view of a LED light source including a mounting member, in accordance with an embodiment; 
         FIG.  102    is a cross-sectional view taken along line B-B in  FIG.  101   ; 
         FIG.  103    is an exploded view of the cross-section of  FIG.  102   ; 
         FIG.  104    is a perspective view of a LED light source including a mounting member in accordance with another embodiment; 
         FIG.  105    is a perspective view of a LED light source including a mounting member in accordance with another embodiment; 
         FIG.  106    is a cross-sectional view taken along line C-C in  FIG.  101    in accordance with an embodiment; 
         FIG.  107    is a cross-sectional view of a LED light source including a mounting member in accordance with another embodiment; 
         FIG.  108    is an exploded view of the cross-section of  FIG.  107   ; 
         FIG.  109    is a perspective view of a frame in accordance with an embodiment; 
         FIG.  110    is a rear perspective view of the frame of  FIG.  109    with a backing removed; 
         FIG.  111    is an exploded view of the frame of  FIG.  109   ; 
         FIG.  112    is a cross-sectional view taken along line D-D in  FIG.  109   , in accordance with an embodiment; 
         FIG.  113 A  is a partial cross-sectional view taken along line D-D in  FIG.  109   , in accordance with an embodiment; 
         FIG.  113 B  is a partial cross-sectional view taken along line D-D in  FIG.  109    in accordance with another embodiment; 
         FIG.  114    is a schematic view of a frame in accordance with an embodiment; 
         FIG.  115    is an enlarged portion of one of the corners of the schematic of  FIG.  114   ; 
         FIGS.  116 - 132    are partial cross-sectional and cross-sectional perspective views taken along line E-E in  FIG.  109   , in accordance with various embodiments; 
         FIG.  133    is an exploded view of the frame of  FIG.  109    in accordance with another embodiment; 
         FIG.  134    is a cross-sectional view taken along line E-E in  FIG.  109    in accordance with an embodiment; 
         FIG.  135    is a partial cross-sectional view taken along line E-E in  FIG.  109   , in accordance with an embodiment; 
         FIG.  136    is a partial cross-sectional view taken along line E-E in  FIG.  109   , in accordance with an embodiment; 
         FIGS.  137 - 139    are schematic views of a frame in accordance with various embodiments; 
         FIG.  140    is an exploded view of the frame of  FIG.  139   ; 
         FIG.  141    is a cross-sectional view of a LED light source in accordance with an embodiment; 
         FIG.  142    is a cross-sectional view of a LED light source in accordance with another embodiment; 
         FIG.  143    is an exploded view of a LED light source in accordance with another embodiment; 
         FIG.  144    is an exploded view of a LED light source in accordance with another embodiment; 
         FIG.  145    is a side view of a LED light source in accordance with another embodiment; 
         FIG.  146    is a side view of a LED light source in accordance with another embodiment; 
         FIG.  147    is an exploded view of a frame in accordance with another embodiment; 
         FIG.  148    is a partial cross-sectional view of the frame of  FIG.  147   ; 
         FIG.  149    is another partial cross-sectional view of the frame of  FIG.  147   ; 
         FIG.  150    is a partial cross-sectional view of a frame showing a cartridge in an inserted position, in accordance with another embodiment; 
         FIG.  151    is the partial cross-section of  FIG.  150    showing the cartridge being removed; 
         FIG.  152    is a schematic illustration of a circuit of an LED light source in accordance with an embodiment; 
         FIG.  153 A  is a schematic illustration of another circuit of an LED light source, showing energy storage members connected in parallel; 
         FIG.  153 B  is the schematic illustration of  FIG.  153    showing the energy storage members connected in series; 
         FIG.  154    is a perspective view of a frame in accordance with another embodiment; 
         FIG.  155    is a schematic view of a circuit of a LED light source in accordance with another embodiment; 
         FIG.  156    is a perspective cross-sectional view of a shelving unit in accordance with an embodiment; 
         FIG.  157    is a cross-sectional view of a shelving unit in accordance with another embodiment; 
         FIG.  158    is a cross-sectional view of a shelving unit in accordance with another embodiment; 
         FIG.  159    is a perspective cross-sectional view of a shelving unit showing a door in a closed position in accordance with an embodiment; 
         FIG.  160    is the perspective cross-section of  FIG.  159    showing the door in an open position; 
         FIG.  161    is a perspective cross-sectional view of a shelving unit showing a door in a closed position in accordance with an embodiment; 
         FIG.  162    is the perspective cross-section of  FIG.  161    showing the door in an open position; 
         FIG.  163    is a perspective cross-sectional view of a shelving unit showing a door in an open position and a shelf installed; 
         FIG.  164    is the perspective cross-section of  FIG.  163    showing the shelf removed; 
         FIG.  165    is a perspective cross-sectional view of a shelving unit in accordance with another embodiment; 
         FIG.  166    is a perspective cross-sectional view of the shelving unit of  FIG.  165    showing a door in a closed position; 
         FIG.  167    is a perspective cross-sectional view of the shelving unit of  FIG.  165    showing the door in an open position; 
         FIG.  168    is a perspective view of a shelving unit in accordance with an embodiment; 
         FIG.  169    is a perspective cross-sectional view taken along line F-F in  FIG.  168   ; 
         FIG.  170    is a perspective view of a shelving unit in accordance with another embodiment; 
         FIG.  171    is a perspective cross-sectional view taken along line G-G in  FIG.  170   ; 
         FIG.  172    is a perspective view of a shelving unit in accordance with another embodiment; 
         FIG.  173    is a perspective view of a drawer in accordance with an embodiment; 
         FIG.  174    is a perspective view of a shelving unit in accordance with another embodiment; 
         FIG.  175    is a cross-sectional view taken along line H-H in  FIG.  174   ; 
         FIGS.  176 - 177    are cross-sectional and perspective cross-sectional views of a LED light source in accordance with an embodiment; 
         FIG.  178    is a perspective view of a walkway in accordance with an embodiment; 
         FIG.  179    is a perspective view of a floor tile in accordance with an embodiment; 
         FIG.  180    is a front elevation view of a garage door in accordance with an embodiment; 
         FIG.  181    is a perspective view of a window in accordance with an embodiment; 
         FIG.  182    is a partial cross-sectional view taken along line J-J in  FIG.  181   ; 
         FIG.  183    is a perspective view of a doorway in accordance with an embodiment; 
         FIG.  184    is a cross-sectional view taken along line K-K in  FIG.  183   ; 
         FIG.  185    is a perspective view of a staircase in accordance with an embodiment; 
         FIG.  186    is a partial cross-sectional view taken along line L-L in  FIG.  185   ; 
         FIG.  187    is a perspective cross-sectional view of a closet in accordance with an embodiment; 
         FIG.  188    is a partial cross-sectional view of a closet in accordance with another embodiment; 
         FIG.  189    is a perspective view of a floor mat in accordance with an embodiment; 
         FIG.  190    is a side elevation view of the floor mat of  FIG.  189    in a flat configuration; 
         FIG.  191    is a side elevation view of the floor mat of  FIG.  189    in a partially rolled configuration; 
         FIG.  192    is a cross-sectional view of a food container supported on a supporting member, in accordance with an embodiment; 
         FIG.  193    is a perspective view of an art display in accordance with an embodiment; 
         FIG.  194    is a cross-sectional view taken along line M-M in  FIG.  193   ; 
         FIG.  195    is a perspective view of furniture in accordance with an embodiment; 
         FIG.  196    is a perspective cross-sectional view taken along line N-N in  FIG.  195   , in accordance with an embodiment; 
         FIG.  197    is a perspective cross-sectional view taken along line N-N in  FIG.  195   , in accordance with another embodiment; 
         FIG.  198    is a perspective view of furniture in accordance with another embodiment; 
         FIG.  199    is a perspective cross-sectional view taken along line P-P in accordance with an embodiment; 
         FIG.  200    is a perspective view of a bicycle equipped with an LED light source in accordance with an embodiment; 
         FIG.  201    is a partial cross-sectional view taken along like Q-Q in  FIG.  200   ; 
         FIG.  202    is a perspective view of a bicycle equipped with an LED light source in accordance with another embodiment; 
         FIG.  203    is a partial cross-sectional view taken along line R-R in  FIG.  202   ; 
         FIG.  204    is a side elevation view of a user wearing a helmet having an LED light source in accordance with an embodiment; and, 
         FIG.  205    is a partial side elevation view of the user wearing the helmet of  FIG.  204   , showing a cross-section of the LED light source. 
     
    
    
     DESCRIPTION OF VARIOUS EMBODIMENTS 
     Numerous embodiments are described in this application, and are presented for illustrative purposes only. The described embodiments are not intended to be limiting in any sense. The invention is widely applicable to numerous embodiments, as is readily apparent from the disclosure herein. Those skilled in the art will recognize that the present invention may be practiced with modification and alteration without departing from the teachings disclosed herein. Although particular features of the present invention may be described with reference to one or more particular embodiments or figures, it should be understood that such features are not limited to usage in the one or more particular embodiments or figures with reference to which they are described. 
     The terms “an embodiment,” “embodiment,” “embodiments,” “the embodiment,” “the embodiments,” “one or more embodiments,” “some embodiments,” and “one embodiment” mean “one or more (but not all) embodiments of the present invention(s),” unless expressly specified otherwise. 
     The terms “including,” “comprising” and variations thereof mean “including but not limited to,” unless expressly specified otherwise. A listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms “a,” “an” and “the” mean “one or more,” unless expressly specified otherwise. 
     As used herein and in the claims, two or more parts are said to be “coupled”, “connected”, “attached”, “joined” or “fastened” where the parts are joined or operate together either directly or indirectly (i.e., through one or more intermediate parts), so long as a link occurs. As used herein and in the claims, two or more parts are said to be “directly coupled”, “directly connected”, “directly attached”, “directly joined”, or “directly fastened” where the parts are connected in physical contact with each other. As used herein, two or more parts are said to be “rigidly coupled”, “rigidly connected”, “rigidly attached”, “rigidly joined”, or “rigidly fastened” where the parts are coupled so as to move as one while maintaining a constant orientation relative to each other. None of the terms “coupled”, “connected”, “attached”, “joined”, and “fastened” distinguish the manner in which two or more parts are joined together. 
     General Description of a LED Light Source 
     The following is a general description of a LED light source that may use any of the features disclosed herein and may be of various configurations as disclosed herein. 
       FIGS.  1  and  2    exemplify a LED light source  100  which includes a housing  104 , a light guide  108  having a light emitting face  112 , and a cartridge  116  having one or more LEDs. As exemplified herein. housing  104  may be of various designs which position cartridge  116  so as to emit light into an end face  144  of light guide  108 . Light guide  108  may be any light guide known in the art. The light reflects internally as it travels longitudinally within light guide  108  and re-emits from light emitting locations  114  on light guide light emitting face  112  towards a subject to be illuminated, such as artwork, advertising media, furniture, or an area of an indoor or outdoor space. 
     Light emitting locations  114  may be formed in any manner suitable for causing at least a portion of light that internally strikes the light emitting locations  114  to emit from light guide light emitting face  112 , or that causes light emission in response to light internally striking the light emitting locations  114 . In some examples, light emitting locations  114  may be spaced apart discontinuities (e.g. bumps or divots) or light scattering material that interrupt the internal reflection of light within light guide  108 , or photoluminescent spots (e.g. fluorescent or phosphorescent spots) that absorb internally incident light and then emit light outwardly. 
     Unidirectional Light Source 
     In accordance with one aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a LED light source  100  is provided wherein light is inhibited from being emitted in one or more directions. Accordingly, in some embodiments, LED light source  100  may preferentially emit light in particular directions. For example, LED light source  100  may preferentially emit light in light emitting directions  120 , and emit substantially no light in non-light emitting directions  124 . An advantage of this design is that it allows the light emitted by the LED light source  100  to be concentrated towards a subject to be illuminated. 
     In one embodiment, light may not be emitted from a rear surface. Accordingly, as exemplified, light guide  108  may have a rear face  128  opposed to light emitting face  112 , and an opaque member, which may have a reflective surface, such as reflector  132 , may overlie rear face  128 . Reflector  132  may reflect light emitted from light guide rear face  128 . For example, an LED light source  100  may be suspended from a ceiling to illuminate a room, and have a reflector  132  that prevents the LED light source  100  from illuminating the ceiling. Reflector  132  may also improve the power efficiency of LED light source  100  by intensifying the light directed in light emitting directions  120 . 
     Reflector  132  has a reflective surface  134  that faces light guide rear face  128  to reflect light escaping light guide rear face  128 . Reflective surface  134  can be made of any reflective material. In some embodiments, reflective surface  134  includes a white coating. An advantage of this design is that it allows reflector  132  to provide a neutral reflection with little or no effect on the color of the reflected light. In some embodiments, reflective surface  134  is coated with a highly reflective coating (e.g. greater than 90% reflectivity), such as titanium oxide. This can reduce light attenuation at the point of reflection to improve the efficiency of the LED light source  100 . As shown in  FIG.  4   , reflector  132  may be positioned with reflective surface  134  abutting light guide rear face  128 . This can allow reflector  132  to reflect all light emitting from light guide rear face  128 . In some embodiments, reflective surface  134  is in physical contact with light guide rear face  128 . 
     Returning to  FIG.  4   , reflector  132  may be a component of housing  104 . For example, reflector  132  may provide a rear wall of housing  104 . Alternatively, reflector  132  may be a discrete component (separate from housing  104 ) that is positioned behind light guide rear face  128 . In some embodiments, reflector  132  is a reflective coating (e.g. paint) applied to light guide rear face  128 . 
     In some embodiments, LED light source  100  does not include reflector  132 . An advantage of this design is that it allows LED light source  100  to emit light in more directions, which can be desirable in some cases such as to simultaneously illuminate a room below and ceiling art above. For example, light guide  108  may include light emitting locations  114  on both of faces  112  and  128  so that light is emitted from both of faces  112  and  128 . 
     Diffuser 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a LED light source  100  may be provided with a diffuser to soften the point effect of light emitted from light emitting face  112 . While the use of light emitting locations  114  on light emitting face  112  may reduce the point effect of light provided by a LED (as compared with the LED facing directly towards the area to be illuminated) a diffuser may provide a more even distribution of light. 
     Accordingly, as exemplified in  FIG.  2   , LED light source  100  may include a light transmitting surface  136  (also referred to herein as a diffuser) that overlays light guide  108  to further diffuse and soften the light emitted by LED light source  100 . Diffuser  136  is at least translucent (i.e. at least semi-transparent). In other words, diffuser  136  is not completely opaque. In the illustrated example, at least a portion of diffuser  136  is formed as a cover that is spaced apart from light guide  108 . This can allow the diffuser  136  to be relatively larger in area than light guide light emitting face  112 , which can thereby enhance the light diffusion capability of diffuser  136 . In the illustrated example, diffuser  136  is shown having a central panel  138  which is spaced apart from light guide light emitting face  112 , and which extends longitudinally between first and second diffuser ends  142  and  146 . Diffuser central panel  138  may be spaced apart from light guide light emitting face  112  by any distance sufficient to allow the light from light guide light emitting face  112  to disperse over central panel  138 . For example, referring to  FIG.  4   , diffuser central panel  138  may be spaced apart from light guide light emitting face  112  by a distance  150  of between about 0.25 to 3 inches. 
     Returning to  FIG.  2   , in some embodiments, diffuser  136  may be non-planar (e.g. curved or angular) which can further enhance the light diffusion capability of diffuser  136  with additional surface area and light emitting directions  120 . In the illustrated embodiment, diffuser  136  includes first and second sides  154  and  158  including first and second diffuser side panels  162  and  170 , each of which extends between the first and second diffuser ends  142  and  146 . As shown, first and second diffuser sides  154  and  158  are oriented at a (non-zero) angle to diffuser central panel  138 . Together, diffuser central panel  138  and diffuser sides  154  and  158  may form a concave inner diffuser surface  174  that extends over the light guide light emitting face  112  and over longitudinally extending light guide sides  178  and  182 . An advantage of this design is that it can allow diffuser  136  to capture and diffuse light emitted by light guide  108  through face  112  and light that may escape through light guide sides  178  and  182 . 
     Diffuser  136  can be made of any material suitable for diffusing light emitted by light guide  108 . For example, diffuser  136  may be made of at least one of acrylic, polypropylene, and polycarbonate. In some embodiments, the diffuser  136  may be white in color. This can reduce or eliminate the effect the diffuser  136  has on the color of the diffused light. In other embodiments, diffuser  136  may be intentionally non-white to provide a desired color effect. 
     In alternative embodiments, LED light source  100  may not include a diffuser  136  or other member that overlays light guide light emitting face  112 . An advantage of this design is that it allows unfiltered light to be focused on an object to be illuminated. A further advantage of this design is that it mitigates the light attenuation associated with diffuser  136 , and therefore improves the lighting efficiency of the LED light source  100 . 
     Light Source with a Removable LED Cartridge 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a LED light source is provided wherein the LEDs are removable so that they may be replaced when, e.g., one or more of the LEDs fails. For example, as exemplified herein, the LED light source may removable receive a cartridge  116  which comprises one or more LEDs. 
     As exemplified in  FIG.  3   , cartridge  116  may be removably receivable in housing  104 . An advantage of this design is that it allows cartridge  116  to be removed, for repair or disposal, and replaced. This contrasts with traditional light fixtures in which a disposable light tube is removably connected to a ceiling ballast. The light tube includes not only an LED or fluorescent lighting module but also a diffusing covering, and other components. LED light source  100  provides a reusable light guide  108  ( FIG.  2   ) and optional diffuser  136  which need not be disposed with cartridge  116 . As a result, cartridge  116  is smaller, lighter, less expensive, and more environmentally friendly than the disposable light tubes of traditional light fixtures. Cartridge  116  also provides greater flexibility to the shape and physical configuration of LED light source  100  because LED light source  100  need not be designed around accommodating a long cylindrical light tube. 
     Cartridge  116  can be removably receivable in housing  104  in any manner that allows cartridge  116  to be powered and positioned to emit light into light guide  108  ( FIG.  2   ). In the illustrated embodiment, housing  104  includes a recess  140  provided on an outer surface of the light source into which cartridge  116  is slideably receivable. This allows cartridge  116  to be conveniently inserted and removed from LED light source  100 , without the need to disassemble the light source which can be particularly significant where LED light source  100  is positioned in difficult-to-reach (e.g. high-up) areas or where there are many (e.g. dozens to thousands) of LED light sources  100  to maintain in a facility (e.g. an office building). 
     Returning to  FIG.  2   , light guide  108  extends longitudinally from a first end face  144  to a second end face  148 . Light guide  108  has a longitudinal length  152 , a transverse width  156 , and a thickness  160 . As shown in  FIGS.  4  and  5   , cartridge  116  may include a plurality of LEDs  164  which are positioned and oriented on a first cartridge face  166  that extends transversely to light guide  108  to emit light into light guide first face  144  when cartridge  116  is received in housing  104 . The light travels along longitudinal length  152  of light guide  108  and is re-emitted from light guide light emitting face  112  at light guide light emitting locations. An advantage of this design is that cartridge  116  may be sized according to light guide transverse width  156  instead of light guide longitudinal length  152 . This allows cartridge  116  to be smaller, lighter, and less expensive as compared with traditional disposable light tubes that are sized to extend substantially the longitudinal length of the light fixture. 
     As exemplified in  FIGS.  4  and  5   , cartridge  116  may be slideably receivable in housing recess  140 . As shown, housing recess  140  may extend from an insertion end  168  transversely of light guide  108  to an inner end  172 , and from a first side  176  longitudinally away from light guide  108  to an opposed face  180 . Housing recess insertion end  168  may define an insertion opening  184  sized to receive cartridge  116 . In use, cartridge  116  may be moved transversely relative to the longitudinal length  152  of the light guide  108  from an insertion position ( FIG.  6   ) to an inserted position ( FIG.  5   ) and vice versa. As shown in  FIG.  4   , in the inserted position, light guide first end face  144  and cartridge first face  166  abut housing recess first side  176  and face each other so that LEDs  164  are oriented and positioned to emit light into light guide  108 . As shown in  FIG.  6   , in the insertion position, cartridge first face  166  is at least partially spaced apart from housing recess first side  176 . From the insertion position ( FIG.  6   ), cartridge  116  can be moved longitudinally towards light guide  108  to the inserted position (FIG.  5 ), or withdrawn from the housing  104  transversely through the housing insertion opening  184  as seen in  FIG.  7   . It will be appreciated that, in the inserted position, the LEDs or the face of cartridge  116  facing the light guide may contact the face of the light guide. Alternately, they may be spaced apart. 
     Returning to  FIGS.  4  and  5   , housing  104  may be configured to retain cartridge  116  in the inserted position, whereby LEDs  164  are positioned in close proximity to light guide first end face  144  for efficient transmission of light from LEDs  164  into light guide  108 . In some embodiments, when cartridge  116  is in the insertion position ( FIG.  6   ), housing  104  may bias cartridge  116  to move to the inserted position ( FIG.  5   ). For example, housing  104  may include a biasing member  188  that urges cartridge  116  to move from the insertion position to the inserted position. An advantage of this design is that it allows the housing recess  140  to provide greater clearance for easy insertion of the cartridge  116  into housing recess  140 . For example, housing recess opening  184  may have a longitudinal width  192  that is substantially wider than the corresponding dimension  196  of cartridge  116 , and biasing member  188  may be relied upon to move cartridge  116  toward housing recess first side  176 , away from housing recess opposed face  180 , to close the gap between LEDs  164  and light guide first end face  144 . 
     Referring to  FIGS.  4  and  7   , in some embodiments, housing recess  140  may narrow in longitudinal width between housing recess insertion opening  184  and housing recess inner end  172 . An advantage of this design is that allows for a wide housing recess insertion opening  184  for easy insertion of cartridge  116 , and also guides cartridge  116  to move toward the inserted position as the cartridge  116  is moved inwardly. In the illustrated example, the narrowing width of housing recess  140  is effected by a cam  204  that defines a portion of housing recess opposed face  180  and that rises towards housing recess first side  176  between housing recess insertion opening  184  and housing recess inner end  172 . It will be appreciated that cartridge  116  may be moved manually into the inserted position shown in  FIG.  5    or alternately a drive member, as discussed hereinafter, may be used. 
     As exemplified in  FIGS.  5  and  6   , cartridge  116  may be prevented from being withdrawn from housing recess  140  when in the inserted position. Instead, it may be required to move cartridge  116  to the insertion position to release cartridge  116  from housing recess  140 . An advantage of this design is that cartridge  116  is prevented from accidental withdrawal. Biasing member  188  may retain cartridge  116  in the inserted position, whereby withdrawal of cartridge  116  is prevented, until a deliberate action (e.g. manual user action) is taken to move cartridge  116  to the insertion position. In the insertion position, cartridge  116  can be freely withdrawn. 
     Cartridge  116  may be prevented from withdrawal when in the inserted position, in any manner. For example, each of housing  104  and cartridge  116  may include a locking member  208 ,  212 . Locking members  208  and  212  can be any components which interact when cartridge  116  is in the inserted position to inhibit withdrawal of cartridge  116  from housing recess  140 . As exemplified, locking members  208  and  212  may include faces that abut in the inserted position to obstruct withdrawal of cartridge  116  from housing recess  140 . In the illustrated example, housing locking member  208  is formed as a protrusion including an inner end face  216 , cartridge locking member  212  is formed as a slot including an inner end face  218 , and end faces  216  and  218  abut when housing locking member  208  is received in cartridge locking member  208  in the inserted position ( FIG.  5   ) to prevent withdrawal of cartridge  116  from housing recess  140 . 
     Referring to  FIGS.  5  and  6   , biasing member  188  can take any form that urges cartridge  116  from the insertion position to the inserted position. In the illustrated embodiment, biasing member  188  is an electrical contact that supplies electricity from a power source (e.g. an electrical wire  214  connected to an energy storage member or an electrical wall plug) to cartridge  116  for powering LEDs  164 . An advantage of this design is that the biasing member  188  performs double duty as a biasing member and electrical conductor thereby avoiding the complexity, weight, and expense of having a separate component act as a biasing member. 
     Still referring to  FIGS.  5  and  6   , biasing member  188  can apply a biasing force to any portion of cartridge  116  that is suitable for urging cartridge  116  to the inserted position ( FIG.  5   ). In the illustrated embodiment, biasing member  188  is positioned in housing recess  140  proximate housing recess inner end  172  to apply a biasing force to an inner end portion  216  of cartridge  116 . An advantage of this design is that biasing member  188  does not act upon cartridge  116  until cartridge  116  is moved into the insertion position within housing recess  140 . This allows LEDs  164  to align with light guide first end face  144  ( FIG.  4   ) before biasing member  188  urges cartridge  116  into the inserted position, for example. 
     In the illustrated example, cartridge  116  is substantially rigid. For example, cartridge  116  may include a rigid substrate  220  (e.g. a printed circuit board) that defines cartridge first face  166 , on which LEDs  164  are arranged. As shown, biasing member  188  may urge cartridge first face  166  to lay flat against housing recess first side  176 . As a result, cartridge  116  is urged to rotate about cartridge inner end portion  216  towards housing recess first side  176  (and light guide first end face  144 ,  FIG.  4   ). Thus, the rigidity of cartridge  116  may cooperate with biasing member  188  to move cartridge  116  into the inserted position ( FIG.  5   ) by application of the biasing force to cartridge inner end portion  216 . Referring to  FIG.  6   , it can be seen that housing recess cam  204  helps to guide cartridge inner end portion  216  into engagement with biasing member  188 . This helps to prevent misalignment of cartridge  116  when it is inserted into housing recess  140 . 
     Referring to  FIGS.  3  and  4   , LED light source  100  can include any housing  104  suitable for holding light guide  108  and cartridge  116 , and optionally hold one or both of a reflector  132  and a diffuser  136 . For example, housing  104  may hold these components in relative positions that allow for efficient transmission and distribution of light from cartridge LEDs  164  to light emitting directions  120 . In the illustrated example, housing  104  includes first and second end members  224  ( FIG.  1   ). Each housing end member  224  may include a light guide retention slot  228  sized to receive an end portion  232  of light guide  108 . In the illustrated example, retention slot  228  is sized to receive light guide end portion  232  and a reflector end portion  236 . An advantage of this design is that it allows housing  104  to hold reflector  132  against light guide  108  for efficient light reflection. In the illustrated example, housing end member  224  includes a transversely extending sidewall  240  and a transversely extending inner wall  250 , which are spaced apart to define retention slot  228 . 
     Referring to  FIG.  2   , LED light source  100  can include any number of cartridges  116 . For example, LED light source  100  may include a cartridge  116  removably receivable in each of the housing end members  224 . An advantage of this design is that it allows cartridges  116  to emit light into both light guide end faces  144  and  148 , which may help to more evenly distribute light emitted from light guide light emitting face  112 , and reduce the average number of internal reflections in light guide  108  for greater light transmission efficiency. In other embodiments, LED light source  100  includes just one cartridge  116  that is removably receivable in just one of housing end members  224 . An advantage of this design is that LED light source  100  has only one cartridge  116  to replace which can reduce replacement time and maintenance costs considerably in environments that have hundreds or thousands of LED light sources  100  installed (e.g. office buildings). 
     Turning to  FIG.  3   , housing end member  224  may include an end wall  248  that defines housing recess opposed face  180 . As shown, housing end wall  248  may be connected to housing sidewall  240  in opposition to retention slot  228 . Housing end wall  248  may include housing recess cam  204  and biasing member  188 . Housing end wall  248  may be integrally formed with housing sidewall  240 , or discretely formed as shown and then permanently or removably connected to housing sidewall  240 . In the illustrated example, housing end wall  248  is connected to housing sidewall  240  with fasteners  252  (e.g., screws). 
     In several of the examples, the housing recess  140  is illustrated as having a housing insertion opening  184  on a lateral side of housing sidewall  240 , which allows cartridge  116  to be inserted and removed in a transverse direction parallel to light guide light emitting face  112 . However, it will be appreciated that housing insertion opening  184  may be positioned elsewhere on housing sidewall  240  and that cartridge  116  may be insertable in different directions. The position of housing insertion opening  184  and cartridge insertion direction may be selected based on, for example the orientation of the LED light source  100  when installed. For example, in some applications it may be preferable to position housing insertion opening  184  for easiest user accessibility (for removing or inserting cartridge  116 ) or alternatively to conceal cartridge  116  (for aesthetics or to avoid tampering). 
     As exemplified in  FIGS.  42 - 46   , insertion opening  184  may be positioned on an upper side  368  of housing sidewall  240 . As shown, cartridge  116  is moveable from an inserted position ( FIG.  44   ) to an insertion position ( FIG.  45   ), and then withdrawable through housing insertion opening  184  in a direction normal to light guide light emitting face  112 . 
     Heat Sink 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a heat sink may be provided to assist in withdrawing head produced by the LEDs. As exemplified in  FIG.  7   , the LED light source may include a heat sink  256  thermally connected to cartridge substrate  220 . The heat sink may be part of the cartridge  116  (see for example the embodiment of  FIG.  7   ) or, alternately, it may be thermally connected to the cartridge  116  when the cartridge  116  is in the inserted position (e.g., it may abut the cartridge  116  when cartridge  116  is in the inserted position). Heat sink  256  can have any design suitable for dissipating heat generated by cartridge  116 , and in particular LEDs  164 . In the illustrated example, heat sink  256  is thermally connected to cartridge second face  260 , which is opposed to cartridge first face  166 . As shown, heat sink  256  may have a plurality of fins extending away from cartridge substrate  220  to increase convective surface area for efficient heat dissipation. 
     In the illustrated embodiment, cartridge  116  includes heat sink  256 , such that heat sink  256  is removable from housing  104  with cartridge  116 , and optionally disposable with cartridge  116 . For example, heat sink  256  may be integrally formed with cartridge  116 , or discretely formed and permanently or removably attached to cartridge  116 . An advantage of including heat sink  256  in cartridge  116  is that it may promote better thermal contact between heat sink  256  and substrate  220  which can lead to better thermal conduction. This thermal contact may be improved by interposing thermal compound (e.g. high thermal conductivity paste or gel) between heat sink  256  and substrate  220 . By allowing heat sink  256  to be disposable with cartridge  116 , the user may avoid having to ensure proper thermal contact or reapply thermal compound between heat sink  256  and substrate  220 . 
     Referring to  FIG.  8   , heat sink  256  may be a separate component from cartridge  116  in some embodiments. For example, heat sink  256  may be a component of housing  104 . Cartridge  116  may be free of heat sinks. An advantage of this design is that heat sink  256  may be a reusable non-disposable component that is retained with housing  104  as cartridge  116  is removed and replaced. This further reduces number of components in disposable cartridge  116 , which can make cartridge  116  less expensive, smaller, and lighter (and consequently less expensive to ship and easier to store). Turning to  FIGS.  9 - 11   , cartridge  116  makes thermal contact with heat sink  256  in the inserted position ( FIG.  9   ), and is thermally disconnected and physically separated from heat sink  256  when removed from housing  104  ( FIG.  11   ). 
     Referring to  FIGS.  9 - 12   , heat sink  256  may be urged into physical contact with cartridge  116  as cartridge  116  is biased into the inserted position ( FIGS.  9  and  12   ). An advantage of this design is that the pressure at the interface of cartridge  116  and heat sink  256  can collapse small particles (e.g. dust or dirt), and thereby promote better thermal contact between cartridge  116  and heat sink  256 . As exemplified, cartridge substrate  220  and heat sink  256  have complimentary faces  260  and  264 , which make flush physical contact when cartridge  116  is in the inserted position ( FIGS.  9  and  12   ). Faces  260  and  264  can have any complimentary surface profiles that promote efficient heat transfer when in flush physical contact. In the illustrated example, cartridge substrate face  260  and heat sink face  264  are flat planar surfaces. 
     Optionally, one or both of faces  260  and  264  includes thermal compound that accommodate surface defects to enhance the thermal contact. In some embodiments, the thermal compound is pre-applied to cartridge substrate face  260  (e.g. in the retail package). An advantage of this design is that the user is not required to apply the thermal compound, which avoids potential complications associated with misapplication of the thermal compound. In other embodiments, the thermal compound is user applied to heat sink face  264 . An advantage of this design is that the cartridge  116  can be provided free of thermal compound, and therefore at a lower weight and cost. Manufacturing and packaging of cartridge  116  are also simplified. Also, the thermal compound applied to heat sink face  264  may remain effective for use in connection with several cartridges  116  before reapplication is required, such that less thermal compound may used overall. 
     Heat sink  256  can be permanently connected or integrally formed with housing  104 , or removably connected to housing  104 . In the illustrated embodiment, heat sink  256  is positioned in housing recess  140 . As shown, heat sink  256  may be connected to housing end wall  248  by biasing members  188   b . Biasing members  188   b  urge heat sink  256  in the longitudinal direction towards cartridge  116  to move cartridge  116  from the insertion position ( FIG.  10   ) to the inserted position ( FIGS.  9  and  12   ). To remove cartridge  116 , the user may apply force to cartridge  116  in opposition to biasing members  188  to move cartridge  116  from the inserted position ( FIGS.  9  and  12   ) to the insertion position ( FIG.  10   ), and then pull cartridge  116  transversely out of housing recess  140  through housing insertion opening  184  ( FIG.  11   ). 
     Housing  104  can include any number of biasing members  188   b , which can be any type of biasing member suitable for urging heat sink  256  against cartridge  116 . In the illustrated example, housing  104  includes two spaced apart biasing members  188   b , which as shown may take the form of helical compression springs. This configuration can allow biasing members  188   b  to provide distributed biasing force against heat sink  256  for more even pressure at the interface of heat sink  256  and cartridge  116 . In alternative embodiments, housing  104  may include just one biasing member  188   b , or more than two biasing members  188   b . Moreover, biasing member  188   b  may take another form, such as a resiliently deformable pad for example. 
     Referring to  FIG.  8   , in some embodiments, housing end wall  248  may be removably connected or movably connected (e.g. pivotally connected) to housing  104 . An advantage of this design is that it can provide access to heat sink  256  (e.g. for repair or replacement of heat sink  256 , or for application of thermal compound to heat sink  256 ). Housing end wall  248  can be removable connected or movably connected to housing  104  in any manner. For example, housing end wall fasteners  252  may be removable to release housing end wall  248  from housing  104 . 
     Driving Member 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a driving member may be provided to assist in moving, or to move, the cartridge to the inserted position. As exemplified in  FIGS.  13 A and  13 B , driving member  268  may be movably mounted in housing  104 , and operable to drive cartridge  116  from the insertion position to the inserted position. The driving member  268  can drive a heat sink  256  against cartridge  116  as shown, or can drive a cartridge  116  including an integrated heat sink. 
     Referring to  FIGS.  14 - 16   , driving member  268  may be movable between a first position ( FIG.  14   ) in which the driving member  268  acts to drive and retain cartridge  116  in the inserted position ( FIG.  14   ), and a second position ( FIGS.  15 - 16   ) in which driving member  268  releases cartridge  116  from the inserted position, whereby cartridge  116  can move to the insertion position ( FIG.  15   ) and then be withdrawn from housing recess  140  ( FIG.  16   ). 
     Referring to  FIGS.  13 B and  14   , driving member  268  can have any construction suitable for selectively driving cartridge  116  between the insertion position and the inserted position. In the illustrated embodiment, driving member  268  is formed as a movable shaft having an inner end  272  pivotally mounted to housing  104 . Driving member  268  may also have an outer end  276  which protrudes from housing  104 , and provides a handle for a user to grasp to manually move the driving member  268  between its first and second positions. As shown, a driving cam  280  may be positioned between the driving member  268  and the cartridge  116 . Driving cam  280  may include a cam surface  284  that interacts with driving member  268  as driving member  268  moves to the first position, whereby the driving cam  280  is moved longitudinally to drive cartridge  116  to the inserted position. 
     Driving member inner end  272  may be pivotally connected to housing  104  in any manner. In the illustrated embodiment, driving member inner end  272  and housing  104  form a ball and socket joint. In other embodiments, driving member inner and  272  and housing  104  may form another type of pivotal connection, such as a hinged joint. 
     Cam surface  284  can have any configuration that allows driving member  268  to move driving cam  280  towards cartridge  116  as driving cam  280  is moved to the first position ( FIG.  14   ). In the illustrated embodiment, cam surface  284  is planar and sloped relative to vertical and horizontal, and driving member  268  is vertically movable between the second and first positions. Driving member  268  rides along cam surface  284  as driving member  268  is moved upwardly to the first position, which causes driving cam  280  to slide longitudinally towards cartridge  116 . In other embodiments, cam surface  284  may be non-planar, which may provide a different movement profile. 
     As shown, heat sink  256  may be connected to housing  104  and positioned between driving cam  280  and cartridge  116 . In this embodiment, moving driving member  268  to the first position ( FIG.  14   ) drives driving cam  280  and heat sink  256  against cartridge  116 , thereby urging cartridge  116  to move to the inserted position. The pressure that forms at the interface of heat sink  256  and cartridge  116  may help to improve thermal contact between them. In alternative embodiments, cartridge  116  includes heat sink  256 , or LED light source  100  includes no heat sink. 
     Referring to  FIGS.  13 A- 16   , LED light source  100  may include one or more biasing members  288 , which act against driving member  268  to retract driving cam  280  when driving member  268  is in the second position ( FIG.  15   ). An advantage of this design is that it allows cartridge  116  to be easily removed ( FIG.  16   ) once driving member  268  is moved to the second position. Biasing member  288  can have any configuration suitable for urging driving cam  280  away from cartridge  116  when driving member  268  is moved to the second position ( FIG.  15   ). In the illustrated example, housing  104  includes two spaced apart biasing members  288 , formed as tensile springs, which are connected to heat sink  256  and housing end wall  248 . As shown, when driving member  268  is moved to the second position ( FIG.  15   ), biasing members  288  pull heat sink  256 , along with driving cam  280 , longitudinally towards housing end wall  248  away from cartridge  116 . This provides clearance for cartridge  116  to move longitudinally to the insertion position ( FIG.  15   ), and then removed from housing  104  ( FIG.  16   ). 
     Referring to  FIGS.  13 A and  16   , housing  104  may include one or more retention members  292  that act to retain driving member  268  in the first or second positions. For example, retention members  292  may retain driving member  268  in position against the force of gravity or biasing members. Retention members  292  can have any configuration suitable for retaining driving member  268  in position. In the illustrated embodiment, driving member outer end  276  extends through a guide slot  296 . The guide slot may guide and constrain the movement of driving cam  280  ( FIG.  13 B ) to a path between the first position ( FIG.  13 A ) and the second position ( FIG.  16   ). As shown, guide slot  296  may include retention members  292  formed as inward protrusions, which narrow a small portion of guide slot  296 . Driving member  268  can be moved along guide slot  296  past the retention members  292  into or out of the first or second position with a bit of force. Consequently, retention members  292  impede driving member  268  from moving out of the first or second positions until a user deliberately applies sufficient force to move driving member  268  past the retention member  292 . 
     Reference is now made to  FIGS.  17 - 19   . In alternative embodiments driving member  268  may be slideably mounted to housing  104 . Driving member  268  may be slideably mounted to housing  104  in any manner that allows driving member  268  to move between the first and second positions. In the illustrated example, housing  104  includes a track  304 , and driving member inner end  272  is slideably mounted to track  304  for movement between the first position ( FIG.  18   ) and the second position ( FIG.  19   ). 
     Reference is now made to  FIGS.  20 - 22   . In some embodiments, driving member  268  is rotationally mounted to housing  104 . For example, driving member  268  may be rotated (e.g. around an axis  308  of driving member  268 ) to drive cartridge to the inserted position. In the illustrated example, driving member inner end  272  is rotatably connected to housing  104 , and driving member  268  is rigidly connected to driving cam  280 , such that they rotate together. 
     Driving cam  280  can have any shape that can drive cartridge  116  towards the inserted position ( FIG.  22   ) when driving cam  280  is rotated to a particular rotary position. For example, driving cam  280  may have a cross-sectional shape normal to rotary axis  308  that is either non-circular (e.g. oblong), or non-centered on rotary axis  308 , or both. Consequently, the distance between cam surface  284  and housing recess  140  changes as driving cam  280  is rotated. In the illustrated example, driving cam  280  has an oblong cross-sectional shape centered on rotary axis  308 . As shown in  FIGS.  23 - 26   , driving cam  280  can rotate (by rotating driving member  268 ) between a first position ( FIG.  23   ) in which driving cam  280  drives cartridge into the inserted position, through an intermediate position ( FIG.  24   ), to a second position ( FIG.  25   ) in which driving cam  280  releases cartridge  116  from the inserted position. In the second position, cartridge  116  is free to move to the insertion position ( FIG.  25   ), and then be removed from the housing  104  ( FIG.  26   ). 
     Turning to  FIG.  22   , driving member outer end  276  may extend through an opening  312  in housing  104  to provide user accessibility to manipulate driving member outer end  276  for rotating driving member  268  about driving member axis  308 . In the illustrated embodiment, housing  104  includes a retention member  292  that acts to resist rotation of driving member  268  from the first position to the second position. As shown, retention member  292  may be a protrusion from housing  104  that makes contact with a protrusion  312  on driving member  268  to resist rotation of driving member  268  to the second position. When in the first position, the user may deliberately apply a force to driving member outer end  276  that overcomes the resistance by retention member  292  to rotate driving member  268  to the second position (and vice versa). Thus, retention member  292  may retain driving member  268  in the first position against, e.g. the force of biasing members  288  ( FIG.  21   ) or resilient compressibility of cartridge  116 . 
     Reference is now made to  FIGS.  27 - 29   . In some embodiments, driving member  268  includes a toggle joint  316 . As shown, toggle joint  316  may include first and second pivotally connected arms  320 . Driving member  268  may also include an arm  324  that extends from toggle joint  316 , and that is manually user operable to articulate the toggle joint  316 . 
     Referring to  FIGS.  29 - 32   , driving member  268  is movable between a first position ( FIGS.  29  and  30   ) in which driving member  268  drives cartridge  116  to the inserted position, and a second position ( FIG.  31   ) in which driving member  268  releases cartridge  116  from the inserted position, which allows cartridge  116  to be moved to the insertion position and then withdrawn from housing  104  ( FIG.  32   ). As shown, moving driving member  268  between the first position ( FIGS.  29  and  30   ) and the second position ( FIG.  31   ) includes articulating the toggle joint  316 . Toggle joint arms  320  are pivotally connected to each other end-to-end, and oriented so that a longitudinal length  328  of the toggle joint  316  changes as the toggle joint  316  is articulated (i.e. as the pivotal connection between the toggle joint arms  320  is articulated). The longitudinal length  328  of toggle joint  316  governs the longitudinal separation of cartridge  116  and housing end wall  248 , whereby increasing longitudinal length  328  moves cartridge  116  towards the inserted position. 
     In the first position ( FIGS.  29  and  30   ), the toggle joint arms  320  may be parallel or nearly parallel (e.g. within 15 degrees of parallel). The longitudinal length  328  of toggle joint  316  drives the cartridge  116  (and heat sink  256  in the example shown) away from housing end wall  248  into the inserted position. In the second position ( FIG.  31   ), the toggle joint arms  320  are substantially folded (i.e. collapsed) into a V-shape, such that the longitudinal length  328  of toggle joint  316  is reduced as compared to the first position. This provides the cartridge  116  (and heat sink  256 ) with longitudinal clearance to move to the insertion position. 
     In some embodiments, moving the driving member  268  between the first and second positions may include inflecting the toggle joint  316 . Toggle joint  316  may have a maximum longitudinal length  328  at an intermediary position between the first and second positions. An advantage of this design is that the inflection operates to retain the toggle joint  316  in the first position ( FIG.  30   ) until a deliberate force is applied to overcome the inflection and move the toggle joint  316  to the second position ( FIG.  31   ). The force required to overcome the inflection may be based on a resilient compression or deformation of cartridge  116  or toggle joint arms  320  at the point of inflection, or a biasing member  332  for example. 
     Still referring to  FIGS.  30  and  31   , in the illustrated example, biasing member  332  is connected to toggle joint  316  and acts to resist longitudinal lengthening of toggle joint  316 . In some embodiments, biasing member  332  may also bias toggle joint  316  to the second position ( FIG.  31   ). Biasing member  332  can be any biasing device, such as a tensile spring or elastic band for example. 
     Openable End Wall 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the housing  104  may have an openable end wall to assist in moving the cartridge to the inserted position. As exemplified in  FIGS.  33 - 35   , housing end wall  248  may be movable (e.g. removable or openable) to provide access to housing recess  140  to insert and remove cartridge  116 , and closeable to hold cartridge  116  in the inserted position. In this regard, housing end wall  248  may be considered a driving member in that movement of housing end wall  248  may drive cartridge  116  into the inserted position. 
     Housing end wall  248  may be connected to housing  104  in any manner that allows housing end wall  248  to be moved (e.g. removed or opened) to provide access to housing recess  140  for inserting and removing cartridge  116 . For example, housing end wall  248  may be translatable (e.g. slidably connected to housing  104 ), or rotatable (e.g. pivot ably connected to housing  104 ) while remaining connected to housing  104 , or completely removable from housing  104  as shown. In the illustrated example, housing end wall  248  is removably connected to housing  104  by housing end wall fasteners  252 . 
     Fasteners  252  may be any fastener suitable for removably connecting housing end wall  248  to housing  104 . Further, housing  104  may include any number of fasteners  252 . In the example shown, fasteners  252  include magnets  336 . Each magnet  336  aligns with a magnetically attractable component  338  (e.g. another magnet or a ferromagnetic component) to form a mating magnetic pair, which connects housing end wall  248  to housing  104 . The mating magnetic pairs may include a magnet  336  on housing end wall  248  and a magnetically attractable component  338  on housing  104 , or vice versa. There can be any number of magnetic pairs. In the illustrated example, there are two magnetic pairs. In other embodiments, there may be just one, or greater than two magnet pairs. 
     In use, the user may disconnect fasteners  252  to move housing end wall  248  to obtain access to cartridge  116  in housing recess  140 . For example, the user may manually (i.e. by hand) apply a removing force to housing end wall  248 , which overcomes the closure force of magnets  336 , to remove housing end wall  248  from housing  104 . Cartridge  116  may then be removed for repair or replacement by a new cartridge. 
     Optionally, as exemplified, heat sink  256  may be provided with a housing having an openable end wall. In such a case, heat sink  256  may be connected to housing end wall  248 . Heat sink  256  may be permanently connected to housing end wall  248 . Alternatively, heat sink  256  may be removably connected to end wall  248 . This can allow heat sink  256  to be easily cleaned, repaired, or replaced. In other embodiments, heat sink  256  is not connected to housing end wall  248 , and instead removably positioned in housing recess  140  after cartridge  116  is inserted, before housing end wall  248  recloses housing recess  140 . In other embodiments, cartridge  116  includes a heat sink  256 . 
     Reference is now made to  FIGS.  36 - 38   . In some embodiments, the housing end wall fastener  252  may be a threaded fastener and housing  104  may include a threaded receptacle  340  to receive the threaded fastener  252 . In use, threaded fastener  252  may be aligned with threaded receptacle  340  and rotated (e.g. using a tool or by hand) to drive the threaded fastener  252  into threaded receptacle  340 , thereby joining housing end wall  248  to housing  104 . In the reverse case, threaded fastener  252  may be rotated to withdraw threaded fastener  252  from threaded receptacle  340 , whereby housing end wall  248  can be separated from housing  104 . 
     Threaded fastener  252  may be configured to remain connected to housing end wall  248  when housing end wall  248  is removed from housing  104 . An advantage of this design is that it avoids having to separately handle and store threaded fastener  252  and housing end wall  248  while, e.g. cartridge  116  is removed and replaced. This can be a real convenience where, for example there are hundreds or thousands of LED light sources  100  to service in a facility. As shown, threaded fastener  252  may be connected to housing end wall  248  in any manner that allows threaded fastener  252  freedom to rotate. In the illustrated example, housing end wall  248  includes a shoulder  344 , which is received in a groove  346  formed in threaded fastener  252  to rotatably connect threaded fastener  252  to housing end wall  248 . 
     Threaded fastener  252  may be rotatable by hand or using a tool (e.g. screw driver). An advantage of a hand rotatable threaded fastener  252  is that no tool is required. An advantage of a tool rotatable threaded fastener  252  is that it can be smaller and more tamper resistant. In the illustrated example, threaded fastener  252  includes a handgrip  352  which is readily grasped by hand and torqued to rotate threaded fastener  252  to tighten or loose threaded fastener  252 . It will be appreciated that threaded fastener may alternately use a bayonet mount. 
     Reference is now made to  FIGS.  39 - 41   . In some embodiments, fasteners  252  may be formed as buckles. An advantage of this design is that the buckles  252  may be easily integrally formed (e.g. molded or cast) with housing end wall  248 , which can reduce the number of components and assembly costs. Buckles  252  may take any form that is selectively user operable to connect and disconnect housing end wall  248  and housing  104 . In the illustrated example, each buckle  252  includes a resiliently flexible spring arm  356  including a hook  360  at a free end thereof. Housing sidewall  240  includes a recess  364  (e.g. an aperture) to receive each hook  360 . In use, spring arms  356  are deflected inwardly and moved to align hooks  360  with their corresponding recesses  364 , and then released to spring back outwardly whereby hooks  360  insert into recesses  364 . In this state, buckles  252  connect housing end wall  248  to housing  104 . To remove housing end wall  248  from housing  104 , spring arms  356  may be again deflected inwardly to remove hooks  360  from their corresponding recesses  364 , thereby freeing housing end wall  248  from connection to housing  104 . 
     Use of Multiple Cartridges 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a single light source  100  may include a plurality of cartridges  116 , which may be the same or different.  FIG.  47    shows an example including one light guide  108 , which receives light from one cartridge  116  received in one housing recess  140  of one housing end member  224 . However, LED light source  100  can have any number of light guides  108  and any number of cartridges  116  in these and other embodiments.  FIGS.  48 - 54    illustrate exemplary configurations of LED light source  100  having a plurality of light guides  108  and/or a plurality of cartridges  116 . 
       FIG.  48    exemplifies an embodiment of LED light source  100  including one light guide  108  and two cartridges  116 . As shown, each housing end member  224  may include a housing recess  140 , and a cartridge  116  may be receivable in each housing recess  140  to emit light into the light guide  108 . Each cartridge  116  is shown emitting light into a different one of light guide end faces  144  or  148 . An advantage of this design is that it can allow for more even illumination and/or more control over the illumination of light guide  108 . For example, cartridges  116  may be substantially identical and illuminate both of light guide end faces  144  and  148  with the same light intensity to provide more even illumination of light guide  108  across its longitudinal length  152 . Alternatively, cartridges  116  may be different from each other to provide differential lighting intensity across light guide longitudinal length  152 . In the illustrated example, cartridge  116   1  has three LEDs  164 , and cartridge  116   2  has two LEDs  164 . All else being equal, this may allow cartridge  116   1  to illuminate light guide end face  144  with greater light intensity than the illumination of light guide end face  148  by cartridge  116   2 . This pattern of side-illumination may provide a desired light emission pattern from light guide  108  for the purpose of illuminating a subject in a desired manner (e.g. for better readability or visibility, or more dramatic effect). 
       FIG.  49    exemplifies an embodiment of LED light source  100  including two light guides  108  and two cartridges  116 . As shown, housing end member  224  includes a housing recess  140  that holds two cartridges  116 . Alternatively, housing end member  224  may include two separate recesses  140 , each of which holds one cartridge  116 . The light guides  108  are shown extending from opposite longitudinal ends  266  and  270  of housing end member  224 . Cartridge  116   1  and  116   2  include LEDs  164  oriented to shine in opposite longitudinal directions so that cartridge  116   1  emits light into light guide  108   1 , and cartridge  116   2  emits light into light guide  108   2 . An advantage of this design is that cartridges  116  are centralized, which can simplify cartridges replacement. For example, where LED light source  100  is mounted high on a ceiling, a ladder may not need to be repositioned to access both cartridges  116 . Instead, the central location of cartridges  116  in the same housing end member  224  may allow both cartridges  116  to be accessed (e.g. for repair or replacement) from one ladder position. Also, this design may be more compact and simpler to manufacture and assemble in that fewer housing end members  224  may be required, all else being equal. 
       FIG.  50    exemplifies an embodiment of LED light source  100  including two light guides  108  and four cartridges  116 . As shown, housing  104  includes an inner end member  224   1  between two outer end members  224   2  and  224   3 . The first light guide  108   1  is connected to end members  224   1  and  224   2 , and the second light guide  108   2  is connected to end members  224   1  and  224   3 . Inner end member  224   1  is shown carrying two cartridges  116  which have LEDs  164  oriented to direct light in longitudinally opposite directions into light guide end faces  144  or  148 , substantially as described with respect to  FIG.  49   . Outer end members  224   2  and  224   3  are shown each carrying a cartridge  116  having LEDs  164  oriented to direct light into the light guide end face  144  or  148  of light guides  108   1  and  108   2  respectively. An advantage of this design is that it provides a central location in end member  224   1  for two of the cartridges as discussed above with reference to  FIG.  49   , and also provides two sided illumination of light guides  108  for more even illumination and/or more control over the illumination of light guides  108  as discussed above with reference to  FIG.  48   . Also as discussed above with reference to  FIG.  48   , cartridges  116  may be identical to one another, or one or more (or all) of cartridges  116  may be different. In the illustrated example, cartridges  116  in inner end member  224   1  are shown having five LEDs  164  each, and cartridges  116  in outer end members  224   2  and  224   3  are shown having three LEDs  164  each. 
     As exemplified in  FIGS.  51 - 52   , housing  104  may include any number light guides  108  connected longitudinally in series by any number of inner end members  224   1 . An advantage of this design is that this can allow for a compact and substantially continuous arrangement of light guides  108 , such as for ceiling-mounted lighting of a large area room (e.g. office space). There may be one or two outer end members  224   2  and  224   3  as seen in  FIG.  51   , or these outer end members may be omitted as in  FIG.  52   .  FIGS.  51 - 52    illustrate embodiments of LED light source  100  including three light guides  108 . However, in alternative embodiments, there may be four or more light guides  108  arranged in series. 
       FIG.  51    exemplifies an example where each inner end member  224   1  holds a cartridge  116  having LEDs  164  that collectively direct light into one of the adjacent light guides  108 . Alternatively or in addition, one or more of inner end members  224   1  may contain a plurality of cartridges  116  that together direct light in opposite longitudinal directions to illuminate both adjacent light guides  108  as in  FIG.  52   . As exemplified, each inner end member  224   1  may include two housing recesses  140  arranged back-to-back to receive cartridges  116  with LEDs  164  oriented to face opposite longitudinal directions. 
     As exemplified in  FIG.  53   , LED light source  100  may include a plurality of cartridges  116  which are arranged to emit light into a single light guide end face  144  or  148 . In other words, LED light source  100  may include a many-to-one relationship of cartridges  116  to illuminated light guide end face  144  or  148 . An advantage of this design is that it allows one cartridge  116  containing a subset of the LEDs  164  which illuminate the end face  144  or  148  to be replaced, instead of replacing a cartridge  116  containing all of the LEDs  164  illuminating that end face  144  or  148 . As a result, the number of working LEDs  164  that are removed when a cartridge  116  is replaced due to one or more failed LEDs  164  may be reduced. 
     Any number of cartridges  116  may be positioned to illuminate a light guide end face  144  or  148 . In the illustrated embodiment, each housing end member  224  is configured to receive four cartridges  116  that in pairs emit light into the same light guide end faces  144  or  148 . Cartridges  116  may be positioned transversely side-by-side as shown, and/or stacked in the thickness dimension of light guide  108 . 
     As exemplified in  FIG.  54   , an inner end member  224   1  holding a plurality of cartridges  116  may include a heat sink  256  thermally connected to the plurality of cartridges  116  to dissipate heat generated by the plurality of cartridges  116 . As shown, the heat sink  256  may be positioned between the cartridges  116 . An advantage of this design is that it allows one heat sink  256  to service a plurality of cartridges  116 , which can reduce the number of heat sinks  256  in LED light source  100 . As a result, LED light source  100  may be lighter, less expensive, and easier to assemble than an LED light source  100  having a discrete heat sink  256  for each cartridge  116 , all else being equal. 
     Non-Planar Light Guides 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the light guide  108  may have a light emitting surface  112  that is not planar. For example, the light emitting face may be round. 
     As exemplified in  FIGS.  55 - 56   , LED light source  100  is formed in the shape of a typical incandescent lightbulb having an engagement end  380  for insertion into a light fixture socket. Engagement end  380  may be any type of bulb base known in the art for electrical engagement with a light fixture socket. For example, engagement end  380  may be a screw base as shown (e.g. a medium base E27), a twist &amp; lock base (e.g. a 10 mm GU10), or a pin base (e.g. a 9 mm G9). Similar to other embodiments, LED light source  100  includes a removable cartridge  116  that allows many or most components of LED light source  100  to be reused. 
     As shown, LED light source  100  may include a diffuser  136 , a light guide  108 , a cartridge  116 , a housing  104 , and a bulb engagement end  380 . Cartridge  116  is removably mounted to housing  104  to emit light into light guide first end face  144 , and light guide  108  re-emits the light from light emitting locations  114  towards diffuser  136  which radiates light outwardly. Cartridge  116  is electrically connected (e.g. by wires or wirelessly) to engagement end  380  to power the cartridge LED(s)  164 . Engagement end  380  delivers power to cartridge  116  from an external power source when connected to a light fixture socket. 
     Light guide  108  can take any shape that allows light to propagate longitudinally through internal reflection and emit through light emitting locations  114  on a light emitting face  112 . Earlier embodiments of light guide  108  (see, e.g.  FIG.  2   ) show a light guide  108  formed as a thin sheet. An advantage of this design is that it allows light guide  108  to emit light across a large area light emitting face  112 , which may be desirable for providing even lighting over large rooms (e.g. offices) for example.  FIG.  56    exemplifies an alternative embodiment including a light guide  108  formed as a rod. An advantage of this design is that it provides a light emitting face  112  facing many directions at once (e.g. 360 degree coverage). This can be desirable where LED light source  100  is formed as a lightbulb for use in light fixtures designed for lightbulbs that emit light in all directions (as in a traditional incandescent lightbulb). In the illustrated embodiment, light guide  108  is formed in the shape of a cylindrical rod having a circularly curved light emitting face  112 . In other embodiments, light guide  108  may be formed in the shape of a rod having a different cross-section, such as triangular, rectangular, oval, or another regular or irregular cross-sectional shape, which may be solid or hollow. 
     Diffuser  136  can take any shape suitable for receiving and radiating light from light guide  108 . For example, diffuser  136  may be shaped according to any known light bulb shape, such as a standard incandescent light bulb shape (bulb shape “A”) as shown. In other examples, diffuser  136  may have a bulb shape with a North American letter designation, such as A, B, BT, BR, C, CA, CW, CP, E, ER, F, G, HK, K, MB, MR, P, PAR, PS, R, S, and T among others. As discussed previously, diffuser  136  is at least partially translucent, and may be completely transparent. 
     As exemplified in  FIGS.  101 - 103   , LED light source  100  includes a diffuser  136  held between two housing end members  224 . As show, light transmitting surface  136  has a substantially rectangular (e.g. square) cross-sectional shape.  FIG.  105    shows another embodiment including a light transmitting surface  136  having a substantially circular cross-sectional shape. In other embodiments, light transmitting surface  136  can have any other regular or irregular cross-sectional shape. 
     Referring to  FIGS.  56  and  57   , light guide  108  extends within diffuser  136  to emit light towards diffuser  136  to be radiated outwardly. Light guide  108  may be secured within diffuser  136  in any manner. In the illustrated embodiment, LED light source  100  includes a light guide mount  384 , which connects light guide  108  to diffuser  136 . As shown, light guide mount  384  may be connected to diffuser  136  proximate diffuser lower end  388 , and hold a lower portion  392  of light guide  108 , whereby an upper portion  396  of light guide  108  extends upwardly away from light guide mount  384  into diffuser  136 . 
     Light guide mount  384  may be secured to diffuser  136  in any manner. In the illustrated embodiment, light guide mount  384  is removably secured to diffuser  136 . An advantage of this design is that is allows light guide mount  384  to be removed to access diffuser  136  for repair or replacement (e.g. replacement with a similar to different light guide  108 ). As shown, light guide mount  384  has external threads  398  which are sized to mate with internal threads  404  within light guide lower end  388 . Alternatively, light guide mount  384  may be removably or permanently secured to diffuser  136  by a fastener (e.g. screws, bolts, rivets, hooks and loops, magnets, snaps), welds, or adhesives. 
     Light guide mount  384  can have any configuration suitable for holding light guide  108  within diffuser  136 . In the illustrated embodiment, light guide mount  384  includes a recess or aperture  410  which is sized to receive light guide lower portion  392  with a press fit. Alternatively or in addition, light guide mount  384  may be connected to light guide  108  by screws, straps, adhesive, or welds for example. In some embodiments, light guide mount  384  may be integrally formed with light guide  108 . 
     Still referring to  FIGS.  56  and  57   , cartridge  116  may be removably connected to housing  104  in any manner. In the illustrated example, housing  104  includes a housing recess  140  sized to receive cartridge  116 . Cartridge  116  may fit into housing recess  140  with a press fit. Alternatively or in addition, cartridge  116  may be connected to housing  104  by a releasable fastener (e.g. screws, bolts, hooks and loops, magnets, or snaps). 
     Optionally, a heat sink may be provided. As exemplified, housing  104  includes a heat sink  256  that is thermally connected to cartridge  116  when cartridge  116  is connected to housing  104 . As discussed previously, heat sink  256  can have any design suitable for removing heat from cartridge  116 . In the example shown, heat sink  256  includes a plurality of fins  412  which extend outwardly from housing  104 . 
     Housing  104  may be connected to diffuser  136  in any manner that holds the LED(s)  164  of cartridge  116  in close proximity (abutting or even in contact) with light guide first end face  144 . Preferably, housing  104  is removably connected to diffuser  136 . As exemplified in  FIGS.  57 - 59   , removing diffuser  136  can provide access to cartridge  116  for repair or replacement. Returning to  FIGS.  56 - 57   , housing  104  may have a removable threaded connection to diffuser  136 . For example, housing  104  may include external threads  416  that are removably engageable with diffuser threads  404 . Alternatively or in addition, housing  104  may be removably connected to diffuser  136  by another releasable fastener (e.g. screws, bolts, hooks and loops, magnets, bayonet mount, or snaps). 
     Controller 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, LED light source  100  may include a controller  420 , which is communicatively coupled to cartridge  116 . Controller  420  may provide programmable and/or remote control of one or more aspects of the light emitted by the light source  100 , (e.g., one or more of the light intensity, the number of LEDs that are energized, the color of the LEDs that are energized, the length of time that the LEDs are energized, the sequence in which the LEDs are energized). For example, controller  420  may be electrically interposed between bulb engagement end  380  and cartridge  116  to control the electrical power to cartridge  116 . 
     Controller  420  may be integrated with cartridge  116 . Alternatively, controller  420  may be a discrete component separate from cartridge  116 , as shown in the illustrated embodiment. An advantage of this design is that it allows controller  420  to be reused as cartridge  116  is replaced, and allows controller  420  to be shielded from heat that cartridge  116  may generate. For example, a heat shield  424  formed of heat insulating material may be positioned between cartridge  116  and controller  420  to shield controller  420  from heat generated by cartridge  116 . Heat shield  424  may be made of any thermally insulating material suitable for shielding controller  420  from the heat generated by cartridge  116  (e.g. having a thermal conductivity of less than 1 W/mK at 20° C.). 
       FIGS.  58 ,  59 , and  57    illustrate a method of removing cartridge  116  from LED light source  100 , such as for repair or replacement. As shown, diffuser  136  may be disconnected from housing  104  to expose cartridge  116 , and then cartridge  116  may be removed from housing  104  and optionally replaced with a new or repaired cartridge  116 . 
       FIGS.  60 - 62    illustrate an alternate method of removing cartridge  116 . In the illustrated embodiment, LED light source  100  is formed as a light bulb including a bulb engagement end  380  and a housing  104 . The housing  104  includes a diffuser  136  (also referred to as a light transmitting surface), and defines an interior  428 . A cartridge  116  is receivable in the housing interior  428 , and removable such as for repair or replacement. As exemplified, housing  104  includes a housing recess  140  having an insertion end  168  for inserting and removing cartridge  116  and light guide  108 . When cartridge  116  and light guide  108  are inserted into housing recess  140 , cartridge  116  is electrically connected to bulb engagement end  380  to receive power from a light fixture socket, and LED(s)  164  of cartridge  116  are oriented to emit light into light guide end face  144 . 
     It will be appreciated that, in any embodiment, cartridge  116  and light guide  108  may together form a disposable and replaceable unitary component of LED light source  100 . An advantage of this design is that it allows cartridge  116  to be well aligned and permanently connected to light guide  108 , ensuring efficient transmission of light from cartridge  116  into light guide  108 . Alternatively, cartridge  116  may be separable from light guide  108  so that light guide  108  can be reused in connection with many cartridges  116 . An advantage of this design is that it allows more of LED light source  100  to be reused and less of LED light source  100  to be disposed, thus decreasing the cost of operating LED light source  100  and decreasing the size, weight, and environmental impact of the disposable components of LED light source  100 . 
     Still referring to  FIGS.  60 - 62   , recess insertion opening  184  may be positioned anywhere proximate an outer surface of LED light source  100  that allows for user access to remove and replace cartridge  116 . In the illustrated example, insertion opening  184  is provided on diffuser  136 . An advantage of this design is that it provides user access to insertion opening  184  to remove and replace cartridge  116  while bulb engagement end  380  remains inserted in a light fixture socket. Reference is now made to  FIGS.  63 - 65   . In alternative embodiments, insertion opening  184  is provided on bulb engagement end  380 . An advantage of this design is that cartridge  116  is prevented from being removed (accidentally or intentionally) while bulb engagement end  380  is inserted in a light fixture socket. This may be an important consideration in some environments, such as factories with heavy machinery that produce vibrations that may cause a cartridge to fall out. Also, this design allows diffuser  136  to have a contiguous outer surface without openings or holes that can allow dirt or liquids to enter. This may be advantageous for outdoor uses of LED light source  100 . 
     Recess  140  can have any shape suitable for receiving light guide  108  and cartridge  116 .  FIGS.  60 - 65    illustrate embodiments having rod shaped light guides  108 , including a cylindrical light guide  108  ( FIGS.  60 - 62   ), and a square cross-section light guide ( FIGS.  63 - 65   ). Recess  140  may be a bore hole in LED light source  100  shaped to correspond with light guide  108 . For example, FIGS.  60 - 62  show a cylindrical recess  140 , and  FIGS.  63 - 65    show a square cross-section recess  140 . 
     Referring to  FIGS.  60 - 62   , light guide second end face  148  may define a portion of LED light source outer surface  432  when inserted in recess  140 . An advantage of this design is that it can allow easy access to remove light guide  108  to access cartridge  116  for repair or replacement.  FIGS.  66 - 68    illustrate an alternative embodiment where LED light source  100  includes an end cap  440  that closes light guide  108  and cartridge  116  within recess  140 , and which defines a portion of the LED light source outer surface  432 . An advantage of this design is that end cap  440  may allow for better control over the character of the light emitted through light guide second end face  148 . For example, end cap  440  may be constructed with similar or identical light transmission properties as diffuser  136  (diffusivity, color, etc.) such that light emitted from light guide second end face  148  through end cap  440  is characteristically similar to light emitted by light guide light emitting face  112  through diffuser  136 . 
     Cartridge  116  may be positioned anywhere within recess  140  that allows cartridge LEDs  164  to emit light into a light guide end face  144  or  148 .  FIGS.  60 - 62    show an example in which cartridge  116  is positioned at recess inner end  172  proximate bulb engagement end  380 . An advantage of this design is that it shortens the electrical connection distance between cartridge  116  and bulb engagement end  380 , which may simplify the electrical wiring within LED light source  100 .  FIGS.  66 - 68    exemplify an alternate example in which cartridge  116  is positioned proximate recess insertion end  168  when inserted in recess  140 . As shown, light guide  108  is positioned inwardly of cartridge  116 . An advantage of this design is that it can allow access to cartridge  116  (e.g. for repair or replacement) without having to remove light guide  108 . 
       FIGS.  69 - 71    illustrate another embodiment including a first cartridge  116   1  positioned proximate recess inner end  172 , a second cartridge  116   2  positioned proximate recess insertion end  168 , and a light guide  108  positioned between the first and second cartridges  116   1  and  116   2 . Cartridge  116   1  emits light into light guide first end face  144 , and cartridge  116   2  emits light into light guide second end face  148 . An advantage of this design is that it allows for relatively greater and more even or controlled illumination of light guide  108 . Cartridges  116   1  and  116   2  may be permanently connected to light guide  108 , and disposable with light guide  108 . Alternatively, cartridges  116   1  and  116   2  may be separable from light guide  108  so that light guide  108  can be reused with new or repaired cartridges  116 . 
     Direct Emission of Light from an LED 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a light guide  108  may not be used. Instead, as exemplified in  FIGS.  72 - 74   , LED light source  100  may not include a light guide  108 . An advantage of this design is that the light attenuation, cost, and complexity associated with including a light guide  108  is mitigated. In the illustrated example, cartridge  116  is removably connected to housing  104  beneath a diffuser  136 . As shown, diffuser  136  may be removable to provide access to remove or replace cartridge  116 . 
     Diffuser  136  can have any shape suitable for radiating light from cartridge  116  onto a subject to be illuminated. In the illustrated embodiment, diffuser  136  is dome-shaped, such that LED light source  100  has the shape of a typical incandescent light bulb.  FIGS.  75 - 77    illustrate an alternate embodiment where diffuser  136  is substantially flat (e.g. planar), such that LED light source  100  has the shape of a halogen light bulb. As shown, housing  104  includes a recess  140  to accommodate cartridge  116  beneath the flat diffuser  136 . 
     Reference is now made to  FIGS.  78 - 80   . As shown, LED light source  100  may include a cartridge  116 , containing a plurality of LEDs  164 , which is removably receivable in housing interior  428 . As shown, LED light source  100  may be free of light guides in some embodiments. Instead, cartridge  116  may emit light directly towards light transmitting surface  136 . An advantage of this design is that it may reduce light attenuation associated with light transmission through a light guide. 
     LEDs  164  may be provided on any one or more faces of cartridge  116 . In the illustrated embodiment, LEDs  164  are provided on a plurality faces, namely opposed cartridge faces  166  and  260 . An advantage of this design is that it allows LEDs  164  to emit light in opposite directions, and thereby better illuminate light transmitting surface  136 , which radiates the light onto the subject to be illuminated. 
     Each cartridge face  166  and  260  may include any number of LEDs  164  arranged in any configuration. In the illustrated embodiment, LEDs  164  are distributed and spaced apart longitudinally along the bulb axis  444 . An advantage of this design is that it allows cartridge  116  to have a narrower width  448 , and therefore require a smaller insertion opening  184  to be formed in light transmitting surface  136 . 
       FIGS.  81 - 83    illustrate an embodiment of LED light source  100  similar to  FIGS.  75 - 77   , except, for example that LED light source  100  has the shape of a halogen light bulb. Also, housing  104  is shown including a heat sink  256 . As shown, heat sink  256  may define an outer surface of housing  104  and may encircle cartridge  116  when cartridge  116  is received in housing interior  428 . An advantage of this design is that it may provide an enlarged area heat sink  256 , which can allow heat produced by cartridge  116  to be dissipated more efficiently. 
     Reference is now made to  FIGS.  84 - 86   . In some embodiment, cartridge  116  may not include an end cap  440 . As shown, this can substantially reduce cartridge width  448 , and consequently allow recess width  192  and insertion opening width  452  to be narrowed. As a result, light transmitting surface  136  may have a greater surface area, all else being equal. 
     In some embodiment, cartridge outer end portion  456  may extend outboard of light transmitting surface  136 . An advantage of this design is that cartridge  116  may be more easily grasped by hand for removal and replacement. In other embodiments, cartridge  116  is wholly positioned within housing  104 . 
     Reference is now made to  FIGS.  87 - 89   . In some embodiments, LED light source  100  may accommodate a plurality of cartridges  116  within housing  104 . An advantage of this design is that it may allow just one cartridge  116  containing a subset of the LED light source&#39;s LEDs  164  to be replaced (while keeping the other cartridge(s)  116  in place), instead of having to replace a single cartridge  116  containing all of the LEDs  164  within light source  100 . Consequently, fewer working LEDs  164  may be disposed when a cartridge  116  is removed due to one or more failed LEDs  164 . 
     In the illustrated embodiment, housing  104  includes two recesses  140 , each of which is sized to receive a cartridge  116 . In alternative embodiments, housing  104  may include a recess  140  which can accommodate a plurality of cartridges  116 . Cartridges  116  may be positioned and oriented anywhere within housing  104 . In the illustrated embodiment, each cartridge  116  is aligned parallel with and spaced apart from bulb axis  444 . An advantage of this design is that cartridges  116  may evenly illuminate light transmitting surface  136 . 
     Reference is now made to  FIGS.  90 - 93   . Cartridge  116  may include any number of faces  166 , each of which may include any number of LEDs  164 . In the illustrated example, cartridge  116  has a cross-shape including eight cartridges faces  166 , and each cartridge face  166  is shown including two LEDs  164 . Thus, an advantage of having a cartridge  116  with many faces  166  is that it can accommodate a greater number of LEDs  164 , which may collectively be capable of emitting greater light intensity, all else being equal. 
     In some embodiment, cartridge  116  may include a heat sink  256  positioned behind and between adjacent cartridge faces  166 . For example, behind each cartridge front face  166  may be a cartridge rear face  260  which is thermally coupled to a heat sink  256 . As shown, heat sink  256  may have a cross-shaped cross-section with outer faces  264  in thermal contact with cartridge rear faces  260 . An advantage of this design is that it may provide a compact arrangement of cartridge faces  166  and effective dissipation of heat generated by LEDs  164 . 
     Reference is now made to  FIGS.  94 - 97   . Recess  140  may be formed in any portion of housing  104 , and may be oriented in any direction. In the illustrated embodiment, housing recesses  140  are oriented transversely (e.g. perpendicularly) to bulb axis  444 . As shown, this allows cartridges  116  to be inserted laterally into housing  104 . An advantage of this design is that depending on the shape of LED light source  100 , this may allow housing  104  to accommodate more cartridges  116  bearing more LEDs  164 . 
     As shown, each cartridge  116  may be shaped and inserted like a tray bearing one or more LEDs  164  on one or more of its surfaces  166  and  260 . In the illustrated example, there are three cartridges  116  and each cartridge includes one or more LEDs  164  on its upper surface  166 .  FIGS.  98 - 100    illustrate another embodiment including cartridges  116  having LEDs  164  provided on their lower surfaces  260 . Alternatively, or in addition, one or more of cartridges  116  may have LEDs  164  on both surfaces  166  and  260 . 
     Weather Sealing 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, in some embodiments LED light source  100  may be weather-sealed. An advantage of this design is that it may allow LED light source  100  to be safely used in outdoor environments. As exemplified in  FIGS.  75 - 77   , housing  104  is shown including a seal  436  (e.g. a resiliently deformable member, such as an O-ring) that engages with diffuser  136  (e.g. by physical contact) when diffuser  136  is connected to housing  104 . As shown, seal  436  may be provided on an outer surface  368  of housing  104  surrounding cartridge  116 , and engage with a rear surface  174  of diffuser  136 . Alternatively, or in addition, diffuser  136  may include a seal  436  that engages housing  104  when diffuser  136  is connected to housing  104 . In any case, seal  436  may inhibit the passage of liquid, dirt, and/or air through the interface of diffuser  136  and housing  104 , thereby protecting cartridge  116  within. 
     Energy Storage Member and/or Energy Generating Member 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, in some embodiments, LED light source  100  may include an energy storage member  460  and/or an energy generating member  476  (see for example  FIGS.  101 - 103   ). Energy storage member  460  may be any device suitable for powering cartridge  116 . In some embodiments, energy storage member  460  has sufficient power capacity when charged to power cartridge LEDs  164  to at least 60% power rating for at least an hour. For example, energy storage member  460  may be one or more batteries or supercapacitors. An advantage of this design is that it can allow LED light source  100  to operate while untethered to an external power source, such as mains electric power. Further, it may be useable as an emergency lighting source when there is a power outage. 
     The energy storage member may be provided at any location. For example, the energy storage member may be provided in the apparatus itself, for example, a lighting fixture, a frame as discussed subsequently or any other apparatus that has the LED light source. Alternately, the energy storage member may be part of a power cord that electrically connects the apparatus to a power outlet (e.g., a household power outlet). Therefore, the energy storage member may be provided in or as part of the electrical plug that is plugged into a wall outlet or in line with the power cord that extends between the electrical plug and the apparatus. 
     As exemplified, energy storage member  460  may be positioned within housing  104 . For example, housing  104  may include an energy storage recess  464  sized to accommodate energy storage member  460 . In some embodiments, as discussed previously, energy storage recess  464  may be weather sealed to inhibit entry of water, snow, and dirt into storage recess  464  when closed. An advantage of this design is that it can allow LED light source  100  to be used outdoors or in other hazardous environments. For example, energy storage recess  464  may include an insertion opening  472  for inserting energy storage member  460  into energy storage recess  464 , and an energy storage recess cover  468  which closes and seals insertion opening  472 . 
     Energy storage recess cover  468  may be movable between a closed position in which energy storage recess cover  482  closes insertion opening  472 , and an open position in which energy storage recess cover  482  is moved away from insertion opening  472  to allow access to energy storage member  460 . An advantage of this design is that it can allow access to energy storage member  460  for repair or replacement. In other embodiments, energy storage recess cover  468  is permanently connected or integrally formed with insertion opening  472 , prohibiting energy storage recess  464  from opening once closed. An advantage of this design is that it can provide a more robust seal between recess cover  468  and insertion opening  472 . 
     In some embodiments, LED light source  100  may alternately or in addition include an energy generating member  476  that is electrically connected to energy storage member  460  and/or the LEDs. An advantage of this design is that it can continuously or periodically recharge energy storage member  460  to allow LED light source  100  to operate autonomously (i.e. without user interaction) for a prolonged period of time. In the illustrated embodiment, energy generating member  476  is a solar panel. As shown, solar panel  476  may form or be incorporated into energy storage recess cover  482 . In other embodiments, energy generating member  476  may include a wind generator (not shown). In other embodiments, LED light source  100  may not include an energy generating member  476 , and instead depend upon energy storage member  460  being recharged by other means or being replaced. 
     Mounting Member 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, LED light source  100  may include a mounting member  480  (see for example  FIGS.  101 - 103   ). Mounting member  480  can be any device that can secure LED light source  100  onto a surface. An advantage of this design is that it allows LED light source  100  to be more versatile in its placement. In the illustrated embodiment, LED light source  100  includes a spike  480  connected to and extending outwardly of housing  104 . Spike  480  may be pushed into a ground surface (e.g. soil) to support LED light source  100  in an upright orientation on that ground surface.  FIG.  104    shows another embodiment including a suction cup  480  that can be suctioned onto a smooth surface, such as a window or tile. 
     Returning to  FIGS.  101 - 103   , mounting member  480  can extend from any portion of LED light source  100 . In the illustrated embodiment, mounting member  480  extends longitudinally outwardly from housing end member  224   1  and energy storage member  460  is positioned within housing end member  224   2 . An advantage of this design is that it can provide ample space for an energy generating member  476  at the end member  224   2  where energy storage member  460  is located.  FIGS.  107 - 108    exemplify another embodiment in which mounting member  480  extends longitudinally from housing end member  224   1  and energy storage member  460  is positioned within housing end member  224   1 . An advantage of this design is that it can shift the weight of the energy storage member  460  to proximate the mounting member  480 , which can improve the mounting stability of LED light source  100 . 
     Partial Emission of Light 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a light guide having a non-planar emission surface may be provided with a diffuser which emits light in only one or more directions. An advantage of this aspect is that light may be directed to illuminate a portion of the space surrounding the light source  100 . As exemplified in  FIG.  106   , light transmitting surface  136  includes a light emitting portion  484 , and an opaque portion  488  (identified with crosshatching). Light emitting portion  484  is at least translucent (i.e. translucent or transparent) to permit light from light guide  108  to pass therethrough and illuminate the surrounding volume. Opaque portion  488  is opaque and in some cases reflective to light from light guide  108 . An advantage of this design is that it allows LED light source  100  to focus light emissions in some directions (i.e. through light emitting portion  484 ) and to block light emissions in other directions (i.e. through opaque portion  488 ). In the illustrated embodiment, light transmitting surface  136  includes one contiguous light transmitting portion  484  and one contiguous opaque portion  488 , which are substantially equal in size. In other embodiments, light transmitting portion  484  and opaque portion  488  may be discontiguous (e.g. striped or spotted) and may be represented in different proportions. It will also be appreciated that the opaque portion  488  may allow some light therethrough and accordingly may not be fully opaque. 
     An inner surface  174  of opaque portion  488  may be reflective (e.g. mirrored) to reflect light from light guide  108  to light emitting portion  484 . An advantage of this design is that at least a portion of light that strikes opaque portion  488  may be emitted outwardly from light emitting portion  484 . 
     Frame 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a frame, such as for art, may be provided with uses a light source having any one or more of the features set out herein. As exemplified in  FIG.  109    to  FIG.  111   , a frame  500  for artwork  504  is provided. The artwork  504  maybe a substantially planar ‘picture-type’ artwork, such as a photo, a print, a painting, or the like. Frame  500  includes one or more LED light source  100  to illuminate artwork  504 . As shown, LED light source  100  may include one or more light guides  108  which are endwise illuminated by LEDs and which emit light from a light emitting face  112  towards artwork  504  through light transmitting surface  136 . An advantage of frame  500  is that it can provide energy efficient and controllable illumination of an artwork  504 . 
     Frame  500  includes one or more side panels  508  that together define an inner opening  512  through which the artwork  504  is viewable. Inner opening  512  may extend in a plane  516 . Alternately, the frame may define an opening that extends in 3 dimensions. Inner opening  512  may be of any shape. For example, frame  500  may have the shape of a parallelogram (e.g. rectangle) having four side panels  508  connected end-to-end as shown. An advantage of this design is that most artwork is parallogrammatic so that a parallelogrammatic frame is widely compatible. In other embodiments, frame  500  may have any other regular or irregular shape formed by any other number of side panels  508 . For example, frame  500  may include just one side panel  508  formed in a circle, three side panels  508  connected end to end in a triangle, or a plurality of side panels  508  configured in the shape of a dog. Thus, frame  500  can have side panel(s)  508  shaped to accommodate artwork  504  of any shape. 
     As exemplified, frame  500  may also include one or more backing layers  520 , which cover a rear face  524  of artwork  504 . As shown, artwork  504  may be positioned between backing layer(s)  520  and the front face of frame side panels  508 . In the illustrated embodiment, frame  500  includes a rigid backer  5201  (e.g. chip board) and a flexible backer  5202  (e.g. paper). Artwork  504  may be attached directly to frame side panels  508 , or held in place against frame side panels  508  by backing layer(s)  520 . Frame  500  may also include a hanger  528  (e.g. wire hanger) secured to frame side panel(s)  508  or frame backing layer(s)  520 . 
     As discussed previously, and as exemplified in  FIGS.  112 - 113 A , LED light source  100  may include one or more endwise-illuminated light guide  108  wherein each light guide  108  may extend longitudinally along part or all of any one or more of frame side panels  508 . For example, each light guide  108  may have a longitudinal length  152  that is at least 40%, 50%, 60%, 70%, 80% or 90% of the corresponding side length  532  of the frame inner opening  512 . An advantage of this design is that it allows light guides  108  to emit light over all or substantially the entire artwork  504 . In the illustrated embodiment, light guide  108  extends along each frame side panel  508 , and each light guide longitudinal length  152  is approximately equal to frame inner opening longitudinal length  532 . 
     As discussed previously, and as exemplified, LED light source  100  may include a plurality of LEDs  164  which are positioned to emit light into light guide end faces  144 . A diffuser  136  may be spaced inwardly towards an opposed side panel  508  of each light guide  108 . As exemplified, diffusers  136  may be formed as planar members that are end wise connected to form a closed perimeter around frame inner opening  512 . An advantage of this design is that it can allow diffusers  136  to diffuse all light emitted towards artwork  504  by light guides  108 . In other embodiments, LED light source  100  may not include a diffuser  136 . For example, the light emitted by light guide  108  may be sufficiently diffuse for the particular artwork  504  being illuminated. Alternately, a diffuser may overlie part or all of a light guide  108 . It will be appreciated that the diffuser may be non-planar (e.g., convex). 
     Referring to  FIG.  111   , frame side panels  508  may be connected in any manner, such as by fasteners (e.g. screws, bolts, nails, rivets), magnets, snaps, press fits, or integral forming. In some embodiments, frame side panels  508  are removably connected. An advantage of this design is that it can allow for at least some disassembly to access LED light source  100  or other components that may require repair or replacement. In the illustrated embodiment, frame side panels  508  are connected by frame corner members  540 . As shown, each frame corner member  540  may removably connect the two adjacent frame side panels  508 . Removing a frame corner member  540  may provide access to, e.g. LEDs, which may be carried on a removable cartridge or a housing end member  224  located adjacent the frame corner member  540 . 
     As exemplified in  FIG.  112   , LED light source  100  may include any arrangement of LEDs  164  suitable to emit light into light guide end faces  144  and/or  148 . In the illustrated example, each light guide  108  has an end face  144  endwise illuminated by an LED  164  (or group of LEDs  164 ) proximate a different corner of frame  500 . As exemplified, one housing end member  224  holding the LEDs  164  is positioned proximate a different corner of the frame  500 . An advantage of this design is that it can provide a relatively large space within frame  500  for the housing end member  224 , LEDs  164 , and any associated heat sink, wiring and/or electronics. 
     Referring to  FIG.  113 B , in some embodiments, there may be two housing end members  224  holding LEDs  164 , which illuminate light guide end faces  144  or  148  of different light guides  108  associated with different frame side panels  508 , located proximate one frame corner  540 . An advantage of this design is that two (sets) of LEDs  164  may be accessible from one corner, such as by moving frame corner member  540 . In some embodiments, one or more (or all) light guides  108  within frame  500  may be illuminated from both of their end faces  144  and  148 , by positioning LEDs  164  that illuminate in two directions within or proximate each frame corner member  540 . An advantage of this design is that it can provide greater, more even, or better controlled illumination of each light guide  108 . 
     As exemplified in  FIGS.  114  and  115   , in some embodiments, one or more LEDs  164  may be positioned and oriented to each emit light simultaneously into two light guide end faces  144  or  148 . An advantage of this design is that it can reduce the number of LEDs  164  and associated components of LED light source  100 . In the illustrated embodiment, an LED  164  is positioned within each of two frame corner members  540  and oriented to emit light into light guide end faces  144  of the two light guides  108  that meet at that corner  540 . As shown, LED  164  emits light into light guides  108  at an angle that results in internal reflection and longitudinal propagation of the light along the longitudinal length of each light guide  108 . 
     As exemplified in  FIG.  116   , in some embodiments, frame side panel  508  may be configured to hold LED light source  100 , or components thereof, in position. As shown, frame side panel  508  may include diffuser retention slots  544  which retain diffuser  136 , and light guide retention slots  548  which retain light guide  108 . Light guide retention slots  548  may also hold reflector  132  in contact with light guide rear face  128 . 
     Frame  500 , including LED light source  100 , may be powered by any power source. In the illustrated embodiment, LED light source  100  includes an energy storage member  460 , positioned, e.g., within an energy storage recess  464 , for supplying power to frame  500 . An advantage of this design is that it allows frame  500  to operate where an external power connection may be unavailable or inconvenient.  FIG.  117    shows an example including a power cord  552  which is electrically connectable to external power. An advantage of this design is that it does not rely on an internal energy storage member which can require periodic replacement or recharging.  FIG.  118    shows another example including a power cord  552  and an energy storage member  460 . An advantage of this design is that the external power source through power cord  552  can charge energy storage member  460 , which can supply power to frame  500  during power outages. 
     If there is a power outage, the LED light source of the frame may alternately operate as emergency lighting. It will be appreciate that if a power cord is provided as in  FIG.  118   , then the energy storage member may be charged from the power cord at any time the power cord is plugged in. Accordingly, if the power cord is plugged in at all times (or hard wired to an electrical supply) then the LED light source may be available as a fully charged emergency lighting source. 
     As exemplified in  FIG.  116   , in some embodiments, light emitted by LED light source  100  (whether directly from light guide  108  or radiated through diffuser  136 ) may directly illuminate artwork  504 . As shown, there may not be provided any covering that overlays the artwork front face  556 . An advantage of this design is that it allows the artwork  504  to receive light unattenuated by a covering, and may permit users to physically touch the artwork  504  if appropriate. For example, the artwork front face  556  may include media (e.g. paint) which creates an uneven surface texture with which users can interact.  FIG.  119    shows an alternative embodiment including a transparent cover  560  (e.g. transparent glass or plastic) which overlays artwork front face  556 . An advantage of this design is that it can protect artwork  504  from user contact and the environment (e.g. liquids and humidity). In some embodiments, cover  560  is configured to reflect, absorb, or otherwise obstruct passage of specific light wavelength bands. For example, cover  560  may be substantially opaque to UV light that may damage artwork  504 . Cover  560  may be positioned rearwardly of LED light source  100  as shown, or outwardly of LED light source  100  as in  FIG.  120   . An advantage of positioning cover  560  outwardly of LED light source  100  is that it can also provide protection for light source  100 . 
     As exemplified in  FIGS.  121  and  122   , in some embodiments, LED light source  100  may be spaced forwardly of the artwork  504  and/or frame opening plane  516 . For example, light guide rear side  178  and/or diffuser rear side  154  may be outwardly spaced apart from the plane  516  of frame inner opening  512  by a distance  536  of, e.g., 0.25 to 1 inches. An advantage of this design is that it can increase the angle of incidence between light emitted by LED light source  100  and artwork  504 , which can allow the emitted light to better distribute across the artwork front face  556 . As exemplified, frame  500  may include a spacer  560  that abuts artwork  504  to retain the rearward spacing between LED light source  100  and artwork  504 . Spacer  560  may be an integral component of frame side panels  508  as shown, or a separate component from frame side panels  508 . 
     As exemplified in  FIG.  123   , in some embodiments, light guide light emitting face  112  may be angled to face rearwardly from vertical, and non-parallel to frame opening plane  516  (and therefore artwork  504 ). An advantage of this design is that it can allow light emitted by LED light source  100  to be directed towards frame opening plane  516 , so that a greater portion of the emitted light strikes artwork  504 , and therefore provides greater illumination of artwork  504 , all else being equal. 
     Light guide light emitting face  112  can have any surface profile suitable for illuminating artwork  504 . In the illustrated example, light guide light emitting face  112  is substantially planar and angled to face rearwardly from vertical towards opening plane  516 .  FIGS.  124  and  125    show other examples including a light guide light emitting face  112  that is convexly ( FIG.  124   ) and concavely ( FIG.  125   ) curved between light guide rear side  178  and front side  182 .  FIG.  126    shows another example including a light guide light emitting face  112  that has a rear concave portion  564  and a front convex portion  568 . 
     Light guide light emitting face  112  may be at a non 0 degree angle to an axis that is perpendicular to the front face of the artwork, e.g., non-parallel with diffuser  136  as exemplified in  FIGS.  124 - 126   , or parallel with an axis that is perpendicular to the front face of the artwork. In some embodiments, diffuser  136  may be angled to face rearwardly from vertical towards opening plane  516 . An advantage of this design is that it can allow light radiated by diffuser  136  to be focused towards frame opening plane  516 , so that a greater portion of the radiated light strikes artwork  504 , and therefore provides greater illumination of artwork  504 , all else being equal. Similar to light guide light emitting face  112 , diffuser  136  may be substantially planar, concave ( FIG.  127   ), or convex ( FIG.  128   ).  FIG.  129    shows another example including a diffuser  136  having a rear concave portion  572  and a front convex portion  576 . 
     As exemplified in  FIG.  130   , in some embodiments, LED light source  100  may not include a diffuser. As shown, light emitted from light guide light emitting face  112  may emit light inwardly towards frame inner opening plane  516  without passing through a diffuser. In this case, light guide  108  may emit sufficiently diffuse light for the particular artwork  504  being illuminated so that a diffuser is unnecessary or unwanted. An advantage of this design is that it avoids the cost, weight, and light attenuation associated with a diffuser. As exemplified, the light emitting face  112  faces towards the artwork and is curved so as to emit light so as to spread out across the front face of the artwork. 
     As previously discussed, LED light source  100  may include any number of reflectors  132  associate with any faces of light guide  108 . For example, LED light source  100  may include reflector(s)  132  positioned so that collectively they reflect light emitted from two or more faces of light guide  108  other than light guide light emitting face  112 . An advantage of this design is that less light propagating through light guide  108  may be lost through faces other than light emitting face  112 . As a result, the efficiency of LED light source  100  may be improved. In the illustrated embodiment, LED light source  100  includes reflectors  132  positioned adjacent light guide bottom face  128 , light guide rear side  178 , and light guide front side  182 . The reflectors  132  may be one contiguous reflector or three discrete reflectors. The reflectors  132  may be in contact with or spaced apart from their respective faces  128 ,  178 , and  182 . In some embodiments, reflector  132  of light guide front side  182  may extend inwardly beyond light emitting face  112 . An advantage of this design is that it allows reflector  132  to reflect stray light emitted from light emitting face  112  back towards frame inner opening  512  (and artwork  504 ). 
     The artwork may be secured in the frame by any method known in the art. For example, the artwork may be unmounted and stretched when mounted in the frame. As exemplified in  FIG.  131   , frame  500  holds artwork  504  in a manner that conceals a peripheral portion  580  of artwork  504 . An advantage of this design is that it hides the unsightly peripheral portion  580  which is fastened to frame  500  (e.g. for the purpose of stretching the artwork  504  flat). In the illustrated embodiment, a rear portion  584  of frame side panel  508  includes an artwork retention slot  588  sized to receive and firmly grasp artwork peripheral portion  580 . As shown, artwork retention slot  588  is positioned rearward of LED light source  100  and therefore hidden from view. 
     Artwork retention slot  588  can hold artwork peripheral portion  580  in any manner. In the illustrated embodiment, artwork retention slot  588  includes a resiliently deformable member  592  that allows artwork peripheral portion  580  to be wedged into artwork retention slot  588 . An advantage of this design is that it provides a non-destructive, selectively removable manner of holding artwork peripheral portion  580 . 
       FIG.  132    exemplifies another embodiment in which artwork  504  is applied to (e.g. bonded to) a canvas backing  596 , and a peripheral portion  604  of canvas backing  596  is held in artwork retention slot  588 . 
     Alternately or in addition to using light sources in one or more of the side panels, the light source  100  may back light part or all of the artwork. Backlighting may be used if the artwork is, e.g., translucent. As with the light source  100  used in the side panels, the light source used for back lighting may use a light source having any one or more of the features set out herein. As exemplified in  FIG.  133 - 135   , frame  500  includes an LED light source  100  that backlights artwork  504 . LED light source  100  can include any number of light guides  108 , which have light emitting faces  112  that collectively underlay (are positioned rearward of the artwork and have a light emitting face  112  that faces towards the artwork) any portion (or all) of the area of frame inner opening  512 . In the illustrated embodiment, LED light source  100  includes two spaced apart light guides  108 , each endwise-illuminated by LEDs held by a housing end member  224 . As shown, light guides  108  are positioned rearward of frame inner opening plane  516  and artwork  504 . Light guides  108  can have any shape and orientation. In the illustrated embodiment, light guides  108  extend longitudinally in a horizontal direction, and are spaced apart in a vertical direction. In other embodiments, light guides  108  may extend longitudinally in a vertical direction or another direction, and may be spaced apart in any direction or side-by-side. 
     As exemplified, light emitting faces  112  are spaced rearwardly of artwork  504 . An advantage of this design is that it allows light emitted by light guides  108  to spread-out across a wider area before striking artwork  504 . For example, light emitting faces  112  may be spaced rearwardly of frame inner opening plane  516  by, e.g., 0.25 to 1 inches. In some embodiments, LED light source  100  may not include a diffuser between light emitting face  112  and artwork  504 . For example, the substrate of artwork  504  (e.g. canvas) may behave as a suitable diffuser for the art thereon. 
     As discussed previously and as exemplified, LED light source  100  may include a reflector  132  positioned rearwardly of light guides  108 . Reflector  132  may have a size that corresponds to the light guide rear faces  128  as in previous examples, or may extend over an area greater than light guide rear faces  128 . In the illustrated example, reflector  132  is sized to overlay substantially the entire frame inner opening  512 . An advantage of this design is that it allows reflector  132  to reflect light emitted (e.g. by reflection or otherwise) from artwork  504 , and therefore improve the lighting efficiency of frame  500 . 
     Frame  500  may include a LED light source  100  that provides side lighting, backlighting, or both.  FIG.  136    shows an example of a frame  500  including an LED light source  100  which includes a light guide  108  rear of frame inner opening plane  516  to provide backlighting, and a light guide  108  positioned forward of frame inner opening plane  512  to provide side lighting. 
     As exemplified in  FIGS.  137 - 138   , LED light source  100  may include backlighting light guides  108  illuminated from one or both end faces  144  and  148 . For example,  FIG.  137    shows light guides  108  illuminated from one end face  144  or  148  each. As discussed previously and as exemplified, light guides  108  may be illuminated from opposite end faces  144  or  148 . An advantage of this design is that it can provide more even illumination by spacing apart LEDs  164  on opposite sides of frame  500 .  FIG.  138    shows another example including light guides  108  each illuminated at both of their respective end faces  144  and  148 . 
     LED light source  100  may include any number of light guides  108  of any longitudinal length  152  and transverse width  156 , so that collectively light guides  108  underlay any portion or all of the area of frame inner opening  512 . The illustrated example includes two light guides  108  that collectively underlay approximately 15% of the area of frame inner opening  512 .  FIG.  139    shows another example including four light guides  108  that collectively underlay approximately 75% of the area of frame inner opening  512 . In some cases, it may be preferable to have light guide(s)  108  that collectively underlay a wide area (e.g. at least 25%) of frame inner opening  512  to more evenly backlight artwork  504 . 
     Alternatively or in addition, LED light source  100  may include a plurality of light guides  108  each having only one light emitting face  112 . An advantage of this design is that each artwork may be backlit by a light guide  108  illuminated by different LEDs  164  selected particularly for that artwork  504 . This can allow for greater variation in the backlighting of the two artworks  504 . 
     As exemplified in  FIGS.  150 - 151   , in any of the embodiments of frame  500  described or shown herein, LEDs  164  of LED light source  100  may be carried on a removable cartridge  116  in accordance with any embodiment of cartridge  116  described or shown herein. The illustrated embodiment shows an example in which a cartridge  116  is insertable into and removable from a recess  140 , and when inserted the LED(s)  164  of cartridge  116  are positioned and oriented to emit light into a light guide first end face  144  or  148 . Recess  140  may include a recess opening  184  formed in frame corner  540  as shown, or a frame side panel  508 . 
     Light Mask 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a light mask  608  may be positioned between LED light source  100  and artwork  504 . Mask  608  can be any element that overlays only a portion of artwork  504  (i.e. does not overlay another portion of artwork  504 ) and which alters the extent to which the LED light source  100  illuminates part of the artwork (e.g., inhibits, diminishes, filters, alters the colour of the light or otherwise alters light emitted by LED light source  100 ). For example, as exemplified in  FIG.  40   , mask  608  may be a discrete disc of material, or a coating (e.g. UV or fluorescent paint) applied to artwork rear face  524  or light guide light emitting face  112  or a further substrate. An advantage of this design is that it can provide fine control over the color and/or intensity of light that backlights different portions of artwork  504 . For example, it may be desirable to position a mask  608  behind a solid-black portion of artwork  504  to inhibit LED light source  100  from backlighting this portion and causing the black to appear as grey. In another example, it may be desirable to position a colored or fluorescent mask  608  under a similarly colored portion of artwork  504  to enhance the color of that portion of artwork  504 , which may otherwise tend to lose color saturation when backlit. In another example, it may be desirable to position a mask  608  behind a lighter portion of artwork  504  to reduce the backlighting of this portion and thereby enabling more backlighting of darker portions of the artwork. It will be appreciated that the mask  608  may be applied to one or more portions of a clear substrate (e.g., glass, plastic) which is of the same size as the artwork and may be separately mounted in the frame. 
     Positioning of the Light Emitting Locations 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the light emitting locations  114  may be distributed over the surface of light guide light emitting face  112  in any manner that provides a desired distribution of light output. In some embodiments, a density of light emitting locations  114  is substantially equal across the whole of light guide light emitting face  112 . An advantage of this design is that it allows large sheets of light guide material to be manufactured and divided arbitrarily for use in LED light sources  100  without concern over registering the light emitting locations  114  to particular portions of each light guide  108  cut from the sheet. 
     As exemplified in  FIG.  141   , light guide  108  may have light emitting locations  114  unevenly distributed over light guide light emitting face  112 . An advantage of this design is that it can allow light guide  108  to emit light at a level of illumination that is substantially the same across light guide light emitting face  112 , or to emit light with a higher level of illumination in some areas compared to others, depending on the arrangement of light emitting locations  114 . For example,  FIG.  141    shows a light guide  108  illuminated from light guide first end face  144  by LED(s)  164 . The quantum of light within light guide  108  decreases from first end face  144 , where no light has yet been deflected out or absorbed by light emitting locations  114 , to light guide second end face  148 , by which point much of the light traveling from light guide first end face  144  has been deflected out or absorbed by light emitting locations  114 . As shown, light guide  108  may have light emitting locations  114  that increase in density longitudinally from the first end face  144  to the second end face  148 . An advantage of this design is that this can allow light guide  108  to emit light at a level of illumination that is substantially the same along the longitudinal length  152  of light guide  108 . For example, the level of illumination emitted at the longitudinal middle  612  of light emitting face  112  may be ±20% of a level of illumination emitted proximate light guide first end face  144 , and in some examples ±10% of a level of illumination emitted proximate light guide first end face  144 . 
       FIG.  142    exemplifies another embodiment including a light guide  108  illuminated from both of light guide first and second end faces  144  and  148  by LEDs  164 . As shown, light guide  108  may have light emitting locations  114  that increase in density longitudinally from the first and second end faces  144  and  148  to the light guide longitudinal middle  612 . Once again, this can allow light guide  108  to provide a generally even level of illumination along the longitudinal length  152  of light emitting face  112 . 
       FIG.  123    exemplifies an example including a light guide  108  that is illuminated by LEDs from a longitudinal end face. In this example, the light emitting locations  114  proximate light guide rear side  178  may contribute illumination to a relatively smaller portion of artwork  504  than the light emitting locations  114  proximate light guide front side  182  due to their closer proximity to artwork  504 . In the illustrated example, light emitting locations  114  increase in density transversely from light guide rear side  178  to light guide front side  182 . An advantage of this design is that it can allow light guide  108  to provide more even illumination across the height of artwork  504  by allowing greater light to emit from the front portion of light guide light emitting face  112  which directs light to a relatively greater area of artwork  504 . As a result, a person viewing the artwork  504  may view a generally evenly illuminated image. 
       FIG.  143    exemplifies another embodiment including an LED light source  100  which illuminates an image  504  having a region  616  of a different color and/or density (e.g. color density) and/or light transmissivity. In some cases, the difference in color, density, or light transmissivity of the image region  616  may result in uneven illumination from image front face  556  when the entire image  504  is evenly backlit through image rear face  524 . In the illustrated example, light guide light emitting face  112  has light emitting locations  114  positioned to enhance the illumination of image region  616  so that a person viewing the image front face  556  views a generally evenly illuminated image, or optionally an enhanced illumination in one or more portions of the artwork. As shown, light guide light emitting face  112  may have a greater density of light emitting locations  114  aligned behind image region  616  than elsewhere on light guide light emitting face  112 . This can allow light guide  108  to provide greater illumination to image region  616  so that image region  616  may appear brighter or, if image region  616  is a darker colour than the rest of the artwork, then to enable image region to, e.g., have about the same level or illumination. 
     Variable Reflection 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, reflector  132  may provide different levels of reflection to thereby provide more light and/or different coloured lights in one or more regions. 
       FIG.  144    exemplifies another embodiment including an LED light source  100  which illuminates an image  504  having a region  616  of a different color, density, and/or light transmissivity. As shown, reflector  132  may include a reflector region  620 , which is aligned with the image region  616 . Reflector region  620  differs from the remainder of reflector  132  in that it is configured to reflect or emit (e.g. photoluminescently) light having a different color. For example, reflector region  620  may be colored, include (e.g. overlaid by) a filter material, or include (e.g. overlaid by) a photoluminescent material (e.g. fluorescent or phosphorescent material). For example, reflector region  620  may comprise UV or fluorescent paint. The color of light reflected or emitted by reflector region  620  may correspond with or compliment the color of image region  616 . This can help improve the color (e.g. color saturation or color accuracy) of image region  616  when backlit by LED light source  100 . 
     Variable Thickness of the Light Guide 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the thickness of the light guide may be varied so as to adjust the level of illumination emitted by one or more portions of the light guide. 
       FIG.  145 - 146    exemplify a light guide  108  having a thickness  160 . As shown in  FIG.  145   , thickness  160  may be substantially constant along a dimension (such as longitudinal length  152  as shown, or transverse width) of light guide  108 .  FIG.  146    exemplifies an embodiment in which thickness  160  varies along a dimension (such as longitudinal length  152  as shown, or transverse width) of light guide  108 . In the illustrated example, light guide thickness  160  decreases from the illuminated light guide end faces  144  and  148  to light guide longitudinal middle  612 . The variation in thickness can be used as an alternative to or in addition to variation in light emitting location density to control the level of illumination emitted from light guide light emitting face  112 , such as to attain generally even illumination emitted across light emitting face  112 . In other embodiments, light guide thickness  160  may increase or decrease in a different manner, such as increasing from longitudinal end faces  144  and  148  to light guide longitudinal middle  612  or decreasing from an illuminated light guide end face  144  to a non-illuminated light guide end face  148 . 
     Double Sided Frames 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, frame  500  may be “double-sided” in that it provides support for two artworks  504  within frame inner opening  512  (see for example  FIG.  147   ). As exemplified, the artwork rear faces  524  face each other, and the artwork front faces  556  face outwardly in opposite directions. An LED light source  100  may be positioned between artwork rear faces  524  to provide backlighting to both artworks  504 . An advantage of this design is that it provides a compact arrangement for displaying two backlit artworks  504  (e.g. as compared with two separate frames  500  each containing one artwork  504 ). 
     As shown in  FIG.  148   , frame  500  may include first and second artwork retention slots  588   1  and  588   2  which hold peripheral portions  580   1  and  580   2  of first and second artworks  504   1  and  504   2  respectively. For example, frame side panels  508  may include first and second artwork retention slots  588   1  and  588   2  which face inwardly from proximate the first and second sides  6241  and  6242  of frame side panels  508 . 
     Double Sided Light Guide 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, a light guide may have more than one light emitting face  112 . Therefore, a planar light guide may have opposed front and rear light emitting surfaces, As exemplified in  FIG.  149   , LED light source  100  may include one or more light guides  108  including dual light emitting faces  112  and  128  which emit light in opposite directions towards artwork rear faces  524   1  and  524   2  of artworks  504   1  and  504   2  respectively. As shown, both light emitting faces  112  and  128  may include light emitting locations  114 . Accordingly, LED light source  100  may not include a reflector  132  positioned to reflect light emitted from either of light emitting faces  112  and  128 . As shown, light emitting faces  112  and  128  are spaced apart from the artwork rear face  524   1  or  524   2  they illuminate respectively. 
     In some embodiments, the light emitting locations  114   1  on light guide light emitting face  112  be the same or identical to the light emitting locations  114   2  on light guide light emitting face  128 . An advantage of this design is that substantially identical backlighting may be provided to both of artwork  504   1  and  504   2  from the light guide  108 . In the illustrated embodiment, the light emitting locations  114   1  on light guide light emitting face  112  differ from the light emitting locations  114   2  on light guide light emitting face  128 . An advantage of this design is that it allows dissimilar artwork  504   1  and  504   2  to be provided with different backlighting (e.g. so that a person viewing the artwork front faces  556   1  and  556   2  views generally evenly illuminated artwork). The differences in the light emitting locations  114  may be one of pattern (e.g. location density), type (e.g. discontinuities vs. light scattering material vs. photoluminescent spots), size or shape, color, or combinations thereof. 
     Alternate Modes of Operation 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, frame  500  may include an LED light source that can be operated to emit light in a selected one of a plurality of modes. The plurality of modes may differ by color (e.g. select activation of LEDs of certain colors), level of illumination (e.g. power to the LEDs), region of illumination (e.g. select illumination of a subset of light guides), sequence of illumination, duration of illumination of a region or combinations thereof. 
       FIG.  152    is a schematic illustration of a circuit  628  of LED light source  100  in accordance with an embodiment. As shown, circuit  628  may include a controller  632  that receives input from one or more user inputs  636 , and/or one or more sensors  640  (also seen in  FIG.  109   ), and in response directs the mode of operation of LEDs  164 . An advantage of this design is that it allows LEDs  164  to operate responsive to environmental conditions or user inputs, which can result in better power efficiency or better user experience. 
     Controller  632  can be any device suitable for directing the mode of LEDs  164  responsive to input from user inputs  636  and/or sensors  640 . For example, controller  632  may include a processor or microcontroller, or may be an integrated circuit, or a logical arrangement of conductors (e.g. wires) and other components (e.g. logic gates, transistors, etc.) that can perform the functionality described herein. Sensor  640  may be a motion sensor, or it may detect levels of sound, illumination in a room or the sound of voices, 
     In some embodiments, controller  632  is operable to change the level of illumination produced by LED(s)  164  in response to inputs from one or more sensor(s)  640  and/or user input(s)  636 . For example, controller  632  may be operable to vary the power delivered from the energy storage member  460  to the LED(s)  164 . The power may be varied by voltage (e.g. reducing the voltage to reduce the level of illumination) or by varying the pulse width modulation (e.g. reducing the duty cycle to reduce the level of illumination). As an example,  FIGS.  153 A and  153 B  exemplify a power supply circuit  628  that can be toggled between a first mode in which batteries  460  can are connected in parallel ( FIG.  153 A ) and a second mode in which batteries  460  are connected in series ( FIG.  153 B ), in response to input from sensor(s)  640 . In the series connection ( FIG.  153 B ), the LEDs  164  receive greater voltage and therefore generate greater illumination than in the parallel connection ( FIG.  153 A ). Power supply circuit  628  can be toggled between the parallel and series connection configurations by moving a switch  630  in response to input from sensor(s) (or by manual operation) between a first position ( FIG.  153 A ) and a second position ( FIG.  153 B ). 
     Returning to  FIGS.  109  and  152   , sensor  640  can be any device that can detect an environmental condition. For example, sensor  640  may be a presence sensor, such as a sound sensor, heat sensor or a motion sensor. An advantage of this design is that it can allow controller  632  to operate LEDs  164  in a different mode (e.g. at an increased level of illumination or by turning the light source on) when sensor  640  indicates nearby human presence (e.g. detects motion or sound indicative of human presence). In the context of an artwork frame  500 , this can provide greater power efficiency where, for example controller  632  increases the level of illumination of LEDs  164  when a person is nearby to view the artwork  504 , and decreases the level of illumination of LEDs  164  (and thus conserving energy) when no one is detected nearby. 
     Alternatively or in addition, sensor(s)  640  may include a light sensor that can detect ambient light. For example, sensor  640  may sense the intensity and color of light shining on frame  500  (and artwork  504  by extension). In the context of artwork frame  500 , this can provide greater visibility and color accuracy to artwork  504  where, for example controller  632  changes the level of illumination and color of LEDs  164  to compliment the sensed intensity and color of light shining on frame  500 . Variations in light intensity and color may be especially prevalent where frame  500  is exposed to natural daylight. 
     User input  636  may be any device suitable for sensing manual user interaction. For example, user input  636  may include a switch such as a button (e.g. mechanical, resistive, or capacitive button), or slider for example. In some embodiments, user input  636  may be operatively connected to energy storage member  460  (or another power supply), and movable between a first position in which the energy storage member  460  is in a first power mode (e.g. series connected batteries) and a second position in which the energy storage member  460  is in a second power mode (e.g. parallel connected batteries). 
     Referring to  FIG.  154   , frame  500  can include any number of sensors  640 . For example, frame  500  is shown including four spaced apart sensors  640 . Sensors  640  can be positioned anywhere on frame  500 . For example, sensors  640  may positioned at different frame corner member  540 . Referring to  FIGS.  152  and  154   , sensors  640  may be light sensors that provide input to controller  632 . In response, controller  632  may direct the mode of LEDs  164 . For example, where frame  500  includes a plurality of light guides  108  (see, e.g.  FIG.  139   ), controller  632  may separately control power to the LEDs  164  illuminating those different light guides  108  in accordance with input from sensors  640  proximate those light guides  108 . As an example, if sunlight is shining on the top half of artwork  504  (and thus detected by the upper two sensors  640 ), controller  632  may direct the LEDs  164  for the light guides that illuminate the top half of artwork  504  to reduce their level of illumination (e.g. by reducing the power level to those LEDs  164 ). 
     Meltable Electrically Conductive Member 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the LEDs may be provided in a circuit such that if one LED were to fail, the remaining LEDs may continue to operate. As exemplified in  FIG.  155   , each LED  164  (or grouping of LEDs  164 ) may be electrically connected in parallel with energy storage member  460  (or other power source). An advantage of this design is that it allows electrical power to pass through each LED  164  independently of the other parallel connected LEDs  164 . For example, if one LED  164  was to fail, an interruption of electrical power across this failed LED  164  would not interrupt the flow of electrical power across the other parallel connected LEDs  164 . 
     In the illustrated embodiment, each LED  164  is electrically connected to the circuit by a meltable electrically conductive member  644 . An advantage of this design is that it can allow the LED  164  to be automatically electrically disconnected if the LED  164  fails in a way that causes the LED  164  to generate heat (e.g. due to electrical resistance of the failed LED  164 ). This can help prevent the failed LED  164  from causing heat damage to the remainder of the circuit  628 , or worse causing a fire. Further, this can eliminate further power consumption by a failed LED  164 . 
     Meltable electrically conductive member  644  can be any electrically conductive device that melts at a temperature corresponding to a temperature of a failed LED  164  receiving the rated current of that LED  164 . For example, meltable electrically conductive member  644  may melt at a temperature above 80° C. In some examples, meltable electrically conductive member  644  may include fuse wire. 
     Shelving Unit or Drawer or Wall Panel or Ceiling Tile 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the light source may be incorporated into part of a shelving unit, drawer, wall panel or ceiling tile. The light source may use any one or more features disclosed herein. 
     As exemplified in  FIG.  156   , a shelving unit  652  (e.g. kitchen cabinet) includes an LED light source  100 . As exemplified, LED light source  100  may be incorporated into a shelf  656  to provide lighting above, below, or both above and below the shelf  656 . In the illustrated embodiment, shelf  656  includes a light guide  108  extending horizontally within an interior of the shelf  656  and having light emitting locations  114  on both an upper surface  112 , and a lower surface  128 . An advantage of this design is that LED light source  100  can provide illumination both above and below shelf  656 . 
     In some embodiments, LED light source  100  defines an exterior surface of shelf  656 . For example, LED light source  100  may include an upper diffuser  1361  defining an upper surface  660  of shelf  656 , and a lower diffuser  136   2  defining a lower surface  664  of shelf  656 . As shown in  FIG.  157   , LED light source  100  may include LEDs  164  positioned within an interior of shelf  656  and oriented to illuminate light guide end face  144 .  FIG.  158    shows an example in which shelf  656  includes a recess  140  for receiving a removable cartridge  116  bearing LEDs  164 . In the illustrated example, recess  140  has an insertion opening  184  in shelf lower surface  664  for upwardly inserting cartridge  116  into recess  140 . In other embodiments, recess  140  may have a recess in shelf upper surface  660  or another shelf surface for inserting cartridge  116  downwardly or horizontally for example. 
     As exemplified in  FIGS.  156 ,  159  and  160   , shelving unit  652  may include a door  668  that is movable (e.g. sliding or hinged) between a closed position ( FIG.  159   ) and an open position ( FIG.  160   ). Moving door  668  from the closed position to the open position may activate LED light source  100  (e.g. cause LED light source  100  to illuminate). For example, shelving unit  652  may include a sensor  672  (e.g. push switch, optical encoder, infrared movement sensor, light sensor, etc.) that detects when door  668  is moved to the open position, and in response activates LED light source  100 . An advantage of this design is that it can allow LED light source  100  to reduce or cease consuming power when shelving unit door  668  is closed. As a result, electrical power consumption is reduced, and the time to failure for the LEDs of LED light source  100  may be extended. 
     In the illustrated example, sensor  672  is a push switch that disconnects LED light source  100  from power source  126  (which may be a power cord  552  or energy storage member  460 ) when door  668  is in the closed position, and that reconnects LED light source  100  to power source  126  when door  668  is in the open position.  FIGS.  161  and  162    show another example including an energy storage member  460  (e.g. batteries) as the power source that sensor  672  disconnects and reconnects to LED light source as shelving unit door  668  is closed and opened. An advantage of this design is that an electrical connection to mains power is not required allowing simpler installation, and reduced energy consumption provides prolonged battery life. 
       FIGS.  163  and  164    illustrate an example in which shelving unit shelf  656  is removable from shelving unit  652 . An advantage of this design is that it can allow shelf  656  to be sold independently (e.g. in standard shelf sizes) and easily inserted (e.g. retrofitted) into a shelving unit that did not before have such lighting functionality. Embodiments of shelf  656  including an internal energy storage member  460  ( FIG.  161   ) as a power source can make installation and shelf height adjustment very simple by avoiding any issues related to external electrical wiring. 
       FIG.  165 - 167    show an example of an LED light source  100  incorporated into the lowermost shelf  656  of shelving unit  652 . LED light source  100  may illuminate in one direction (e.g. upwards or downwards) or in two directions (e.g. upwards and downwards). In the illustrated embodiment, LED light source  100  includes an upper diffuser  136 , which may define shelf upper surface  660 , and a lower reflector  132 , such that LED light source  100  emits light upwardly into the interior of shelving unit  652  and not downwardly.  FIGS.  168 - 169    exemplify another embodiment, in which diffuser  136  and reflector  132  are reversed so that LED light source  100  emits lights downwardly (e.g. onto a kitchen counter below). As shown, LED light source  100  may be recessed from a lower end of shelving unit  652 , which may be formed by under-cabinet molding  684  as shown. An advantage of this design is that it can help focus the light downwardly, which can mitigate shining light directly towards user&#39;s eyes. In still other embodiments, reflector  132  is replaced by a diffuser  136  so that LED light source  100  emits light both upwardly and downwardly. 
     As exemplified in  FIGS.  170 - 171   , any portion of shelving unit  652  may incorporate an LED light source  100  which can be configured to illuminate inside and/or outside of shelving unit  652 . In the illustrated example, shelving unit  652  includes a front face  676  formed by LED light source  100 . Front face  676  may be part of under-cabinet molding as shown or positioned elsewhere on shelving unit  652  (e.g. part of above-cabinet molding). As exemplified, light guide  108  may extend laterally across front face  676  between a front diffuser  136  that radiates light forwardly and a rear reflector  132 . 
     As exemplified in  FIG.  172   , a plurality of LED light sources  100  may share a common power supply  688 . An advantage of this design is that each LED light source  100  is not required to have its own independent source of power. In the illustrated example, a plurality of shelving units  652  are shown, each including at least one LED light source  100 , and one common power supply  688  which is electrically connected to all of the LED light sources  100 . Power supply  688  may be any device suitable for distributing power to the plurality of LED light sources  100 . For example, power supply  688  may include an energy storage member (e.g. batteries) and/or may be electrically connected to mains power. 
     In some embodiments, power supply  688  may be remotely controlled. An advantage of this design is that the electronics to control the plurality of LED light sources  100  may be centralized into one device, which can coordinate their operation. For example, power supply  688  may receive control signals by wire or wirelessly (e.g. over Bluetooth or by infrared) from a control device such as a smartphone, a remote control, or a wall mounted control panel. The control signals may direct power supply  688  to vary the illumination intensity or color of the LED light sources  100  individually or as a group. 
     As exemplified in  FIG.  173   , a drawer  692  may include an LED light source  100 . LED light source  100  may be incorporated into any one or more of the bottom wall  696 , or side walls  704  of drawer  692 . An advantage of this design is that it can provide illumination into a drawer which may be in shadow relative to the light source in the room. In the illustrated example, LED light source  100  includes a light guide  108  (and optionally a front diffuser and rear reflector) incorporated into each of the four side walls  704 . 
     As exemplified in  FIGS.  174  and  175   , a shelving unit  652  may include an LED light source  100  incorporated into the shelving unit doors  668 . An advantage of this design is that it can provide additional illumination to open drawers  692 , to objects withdrawn from the shelving unit  652  (e.g. clothing), and to the user using the objects withdrawn from the shelving unit  652  (e.g. the user trying on clothing). As shown, LED light source  100  emits light from an inside face  712  of shelving unit door  668 . In the illustrated example, shelving unit  652  is shown including a shelving unit sensor  672  that can activate LED light source  100  in response to sensing that shelving unit doors  668  are open. 
     As exemplified in  FIGS.  176  and  177   , the LED light source  100  shown may form or be incorporated into a wall panel or ceiling tile. As shown, LED light source  100  includes a light guide  108  and diffuser  136  which are held spaced apart by a plurality of longitudinally spaced apart spacers  716 . An advantage of this design is that spacers  716  can support loads applied to diffuser  136  (e.g. weight of a standing person) to hold diffuser  136  spaced apart from light guide light emitting face  112 . 
     Spacers  716  may be integrally formed with light guide  108  as shown, or discrete components that are positioned between light emitting face  112  and diffuser  136 . In some embodiments, spacers  716  and diffuser  136  may include mating mechanical or locking connectors  720 . An advantage of this design is that it can make it easy to assemble diffuser  136  with spacers  716 . In some embodiments, mechanical connectors  720  may be removably connectable. This can allow diffuser  136  to be removed, such as to access light guide  108  for repair or replacement. In the illustrated embodiment, mechanical connectors  720  include male connectors  7201  which are securely receivable in female connectors  7202 . 
     In the illustrated embodiment, housing  104  surrounds light guide  108  (including light emitting face  112 ) and diffuser  136 . In some embodiments, housing  104  is sealed to diffuser  136  to inhibit the passage of liquid and dirt. An advantage of this design is that it can allow LED light source  100  to be used outdoors.  FIG.  176    shows an example of LED light source  100  having a reflector  132  and one light emitting face  112 .  FIG.  177    shows an example of LED light source  100  having no reflector and two light emitting faces  112  and  128 . As shown in  FIG.  177   , spacers  716  may be spaced apart and longitudinally distributed between light emitting face  112  and diffuser  1361 , and between light emitting face  128  and diffuser  136   2 . 
     Floor Tile, Window Frame, Stair Case and Closet, Floor Mat 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the light source may be incorporated into part or all of a floor tile or window frame or s stair case or closet or floor tile. The light source may use any one or more features disclosed herein. 
     Reference is now made to  FIGS.  178 - 179   . As shown, LED light source  100  (e.g. as shown and described with respect to  FIG.  176   ) may be formed as or incorporated into a floor tile  722  for an indoor or outdoor walkway  728 . In the illustrated example, walkway  728  includes a plurality of floor tiles  722  incorporating LED light source  100 , and a plurality of traditional floor tiles  724  (e.g. absent any lighting function). 
     In some embodiments, floor tile  722  may include a mounting member  732  that helps to join the floor tile  722  to adjacent floor tiles  722  or  724 , and/or to the mounting substrate (e.g. dirt, gravel, or mortar). As shown, floor tile  722  may include one or more fasteners  736  that join diffuser  136  to housing  104 , and which can be selectively released to remove diffuser  136 , such as to access light guide  108  or other components of LED light source  100  within housing  104 . Floor tiles  722  may be powered in any manner disclosed herein. In the illustrated embodiment, floor tiles  722  are electrically connected to each other, and receive electrical power from a solar panel  476 . 
     As exemplified in  FIGS.  180 - 182    window frame  744  is similar to frame  500  shown and described elsewhere in the application, except for example that window frame  744  holds a window pane  748  instead of artwork and a backing layer. As shown, window frame  744  includes frame side panels  508  that surround a frame inner opening  512  and hold a window pane  748 . LED light source  100  may be incorporated into any one or more (or all) of frame side panels  508 . Window frame  744  may be powered in any manner disclosed herein. In the illustrated embodiment, window frame  744  includes solar panels  476  that are electrically connected to LED light source  100  for providing power to the same. Window frame  744  may be part of any structure, such as a garage door  752  as shown, or a fixed building structure (e.g. a wall). 
     As exemplified in  FIGS.  183 - 184   , doorway  756  may include a door  760  and a door frame  764 . As shown, door frame  764  may include an LED light source  100 . An advantage of this design is that door frame  764  can provide illumination to the area near door frame  764 . For example, door frame  764  may provide some initial illumination to a dark room on the opposite side of door  760 , which can make finding and activating a light switch for the dark room easier and safer. Door frame  764  includes one or more frame side panels  508  which collectively define a frame inner opening  512  for door  760 . In the illustrated example, door frame  764  includes two vertical frame side panels  5081  connected at their upper ends  768  by a horizontal frame side panel  580   2 . 
     LED light source  100  may form or be incorporated into any one or more of frame side panels  508 , which can provide illumination in any direction(s). For example, LED light source  100  may provide illumination through any one or more (or all) of the front face  772 , outer face  776 , and inner face  780  of frame side panel  508 . In the illustrated embodiment, LED light source  100  includes a light guide  108  having a light guide light emitting face  112  oriented to emit light inwardly towards a diffuser  136  which defines frame side panel inner face  772 , which borders frame inner opening  512 . 
     As exemplified in  FIGS.  185 - 186   , a staircase  784  in accordance is provided. As shown, staircase  784  may include an LED light source  100 . For example, LED light source  100  may form or be incorporated into any one or more (or all) of stair risers  788  and stair treads  792  of staircase  784 . An advantage of this design is that it can provide illumination (e.g. at night) for a user climbing or descending staircase  784 . In the illustrated example, LED light source  100  includes a light guide  108  having a light guide light emitting face  112  oriented to emit light forwardly towards a diffuser  136  which defines riser front surface  796 . 
     As exemplified in  FIG.  187   , closet  804 , closet  804  may include a shelf  656  formed by or incorporating an LED light source  100 . An advantage of this design is that shelf  656  can provide illumination to an interior of closet  804 , which may be shadowed from the light source in the room when accessed by a user. In the illustrated embodiment, shelf  656  is positioned above (i.e. at a higher elevation) than closet rod  808 . Shelf  656  may be mounted in positioned to one or more (or all) of closet rear wall  812  and closet side walls  816 . 
     As exemplified in  FIG.  188   , closet  804  may include an illuminated closet rod  808 . Closet rod  808  may be formed by or incorporate an LED light source  100  as shown. For example, light guide  108  may be formed as a rod. An advantage of this design is that it provides a light emitting face  112  facing many or all directions at once (e.g. 360 degree coverage). In the illustrated embodiment, light guide  108  is formed in the shape of a cylindrical rod having a circularly curved light emitting face  112 . In other embodiments, light guide  108  may be formed in the shape of a rod having a different cross-section, such as triangular, rectangular, or another regular or irregular cross-sectional shape. As shown, diffuser  136  may be shaped as a hollow tube which surrounds light guide  108 . Similar to light guide  108 , diffuser  136  may have any cross-sectional shape, such as a circular, triangular, rectangular, or other regular or irregular cross-sectional shape. 
     As exemplified in  FIGS.  189 - 191   , floor mat  820  may include an LED light source  100  that shines light upwardly, and a power supply  688  that supplies power to the LED light source  100 . An advantage of this design is that floor mat  820  can provide visibility to a user walking over or near the floor mat  820 , such as in a dark bathroom or hallway at night. As shown, diffuser  136  may have an outer surface  824  that provides a supporting surface for a user to walk over. 
     In some embodiments, floor mat  820  may be flexible. For example, floor mat  820  may be at least sufficiently flexible to roll into a tubular configuration. An advantage of this design is that it can allow floor mat  820  to take on a more compact configuration for easier shipping or storage. As shown, light guide  108  may be composed of a thin flexible material such as polycarbonate having a thickness of 0.0625 in to 0.125 in. 
     Diffuser 
     In some embodiments, diffuser  136  may include a plurality of discrete projections  828  from light guide  108 . Diffuser projections  828  may be arranged side-by-side overlaying light guide  108  according to any pattern. In the illustrated example, diffuser projections  828  are arranged in a grid pattern. Diffuser  136  can include any number of projections  828 . For example, diffuser  136  may include 10 or more projections  828 . In the illustrated embodiment, diffuser  136  includes 65 projections. As shown, diffuser projections  828  may angle away from each other when floor mat  820  is rolled into a tubular configuration. An advantage of this design is that it reduces tensile stress on the diffuser  136  when floor mat  820  is rolled. 
     Diffuser projections  828  can be made of any material suitable for walking over. In some embodiments, projections  828  are made of an elastomeric material, such as silicone. An advantage of this design is that it may be more comfortable for walking over, and may be able to resiliently accommodate deformations (e.g. stretching) caused by rolling floor mat  820 . 
     Food Container 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the light source may be incorporated into a food container. 
     Reference is now made to  FIG.  192   , which shows a food container  832  supported on a supporting member  836 . Food container  832  may be any article made to support food or drink, such as a cup, a bowl, or a plate for example. Supporting member  836  may be any article made to support food container  832 , such as a counter tabletop, a serving tray, or a coaster. As shown, supporting member  836  may be formed by or incorporate an LED light source  100  that shines light towards food container  832 . Further, food container  832  may function as a light guide, being composed of at least translucent material which conducts light from LED light source  100  through internal reflection, and including light emitting locations  114  associated with an exterior light emitting face  112  which shines light outwardly. An advantage of this design is that it allows food container  832  to shine light without having to incorporate a light source (e.g. LEDs  164 ) into the food container  832 . Instead, LED light source  100  is incorporated into supporting member  836 , which can allow food container  832  to be made dishwasher safe for example. 
     Art Display 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the light source may be incorporated into an art supply. 
     Reference is now made to  FIGS.  193 - 194   , which show an art display  840  which illuminates a supported artwork  844 . Artwork  844  may be a three-dimensional artwork, such as a statue, a figurine, a trophy, a framed image, or any other object a user may wish to display and illuminate. As shown, art display  840  may include a base  848  formed by or incorporating an LED light source  1001  and an overhead LED light source  1002 . The base  848  includes an upper surface  852  that supports artwork  844 . An advantage of this design is that it can illuminate an artwork  844  from multiple directions. LED light source  1001  may shine light upwardly from base upper surface  852  to illuminate artwork  844  from below. LED light source  1002  may shine light downwardly to illuminate artwork  844  from above. 
     Furniture 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the light source may be incorporated into a furniture. 
     Reference is now made to  FIGS.  195 - 196    which show furniture  856  in accordance with an embodiment. Furniture  856  may be any type of furniture, such as a chair as shown, a stool, a couch, a table ( FIGS.  198 - 199   ), a desk, or a bed for example. Furniture  856  can incorporate an LED light source  100  to provide illumination from one or more furniture portions  860 . An advantage of this design is that it can improve the visibility of the furniture  856  and/or the furniture surroundings, such as in the dark or low lighting conditions. Chair  856  includes a seat  864  supported on legs  868 , and a backrest  872  extending upwardly from seat  864 . 
     Any one or more of seat  864 , legs  868 , and backrest  872  may be an illuminated portion  860 . In the illustrated embodiment, chair backrest  872  is an illuminated portion  860 . Chair backrest  872  includes an illuminated light guide  108 . Light guide  108  may be configured to illuminate in any direction, such as forwardly towards a seated user as shown, rearwardly, or both. In the example shown, LED light source  100  includes a diffuser  136  which forms a front surface  876  of chair backrest  872 , and light guide  108  extends in a plane parallel to backrest front surface  876 . 
       FIG.  197    shows another embodiment of chair  856  in which seat  864  is another illuminated portion  860 . As shown, chair seat  864  includes an illuminated light guide  108   2 . Light guide  108   2  may be configured to illuminate in any direction, such as downwardly towards the ground as shown, upwardly towards a seated user, or both. In the example shown, LED light source  100  includes a diffuser  136   2  which forms a lower surface  880  of chair seat  864 , and light guide  108   2  extends in a plane parallel to seat lower surface  880 . 
       FIGS.  198 - 199    show another example of furniture  856  incorporating an LED light source  100 . In this example, furniture  856  is a table having legs  868  and a tabletop  884 . As shown, tabletop  884  may be an illuminated portion  860  of table  856 . In the example shown, tabletop  884  includes an illuminated light guide  108 . Light guide  108  may be configured to illuminate in any direction, such as upwardly as shown, downwardly towards the ground, or both. In the example shown, LED light source  100  includes a diffuser  136  which forms an upper surface  888  of tabletop  884 , and light guide  108  extends in a plane parallel to tabletop upper surface  888 . 
     Returning to  FIG.  195   , LED light source  100  can be powered in any suitable manner, including any manner disclosed herein. In the illustrated example, furniture  856  includes a solar panel  476  and an energy storage member  460 , which are electrically connected to LED light source  100  to supply power to the same. In some embodiments, solar panel  476  may operate to charge energy storage member  460 . In other embodiments, solar panel  476  may supplement or replace energy storage member  460  as the power source of LED light source  100  when there is sufficient solar energy, and energy storage member  460  may be the sole supply of power to LED light source  100  when solar panel  476  generates insufficient power. 
     Solar panel  476  and energy storage member  460  may be attached to or incorporated into any portion of furniture  856 . In the illustrated embodiment, solar panel  476  has a light collection face  892  positioned to form an upper surface  896  of chair backrest  872 , and energy storage member  460  is positioned within one of chair legs  868 . An advantage of this design is that it avoids adding bulk to chair  856 . 
     Bicycle and Helmut 
     In accordance with another aspect of this disclosure, which may be used with one or more other aspects disclosed herein, the light source may be incorporated into a bicycle and/or a helmet. 
     As exemplified in  FIGS.  200 - 201   , bicycle  900  may include a frame  908 , and a seat  912 , wheels  916 , and handlebars  920  mounted to frame  908 . LED light source  100  may have a tubular configuration that can be mounted to any one or more of frame  908 , seat  912 , wheels  916 , and handlebars  920  to provide outward illumination. An advantage of this design is that it can improve the visibility of bicycle  900  to motorists, which can make bicycle  900  safer to ride, especially at night. 
     In the illustrated example, LED light source  100  is mounted to handlebars  920 . As shown, LED light source  100  (including light guide  108  and optionally a diffuser  136 ) may surround a portion of handlebars  920  in cross-section, and have an outward light emitting direction  120 . To facilitate mounting, LED light source  100  may include two or more parts  924  which are movable (e.g. separable) to allow LED light source  100  to open and enclose around handlebars  920 . In the illustrated embodiment, LED light source  100  includes two parts  924  which are removably connected by mechanical connectors  720 , as shown. In other embodiments, LED light source  100  may include three or more parts  924 . Alternatively, LED light source  100  may have a single part  924  with a seam  928 , and which is sufficiently resiliently flexible to allow the seam  928  to be temporarily widened enough to insert or remove handlebars  920 . 
     LED light source  100  can have a tubular shape that defines an inner opening  932  having any cross-sectional shape. For example, the cross-sectional shape of inner opening  932  may be circular as shown in  FIG.  201   , triangular, square, hexagonal, or another regular or irregular shape.  FIGS.  202 - 203    illustrate an embodiment in which LED light source  100  has an inner opening  932  with a substantially square shape to accommodate a substantially square cross-section of bicycle frame  908 . 
     LED light source  100  can be powered in any suitable manner, including any manner disclosed herein.  FIG.  201    illustrates an example including an energy storage member  460 .  FIGS.  202 - 203    illustrate an example including an energy generating member  476 . As shown, energy generating member  476  may be connected to rear wheel  916  to generate power from the rotation of rear wheel  916 . An advantage of this design is that it can provide power to illuminate LED light source  100  whenever bicycle  900  is in motion, which may account for the most critical moments to have illumination. 
     As exemplified in  FIGS.  204 - 205   , a helmet  934  may be any suitable type of helmet, such as a bicycle helmet as shown, a motorcycle helmet, or a ski helmet for example. Helmet  934  may include an LED light source  100  which provides illumination to one or more illuminated portions  936 . An advantage of this design is that it can provide helmet  934  with greater visibility to others (e.g. motorists, skiers) which can provide additional safety to the wearer. Depending on the light emitting direction and brightness, LED light source  100  may also be effective for illuminating the wearer&#39;s surroundings for enhanced visibility by the wearer. 
     In the illustrated example, helmet  934  includes an illuminated portion  936  at rear end  944 . This can make helmet  934  highly visible to others (e.g. motorists) behind the wearer. As shown, a light guide  108  may be incorporated into helmet  934  with a rearward light emitting direction  120 . 
     Alternatively or in addition, helmet  934  may include an illumination portion at front end  948 . This can allow helmet  934  to illuminate the environment ahead of the wearer. 
     While the above description provides examples of the embodiments, it will be appreciated that some features and/or functions of the described embodiments are susceptible to modification without departing from the spirit and principles of operation of the described embodiments. Accordingly, what has been described above has been intended to be illustrative of the invention and non-limiting and it will be understood by persons skilled in the art that other variants and modifications may be made without departing from the scope of the invention as defined in the claims appended hereto. The scope of the claims should not be limited by the preferred embodiments and examples, but should be given the broadest interpretation consistent with the description as a whole.