Abstract:
A method and apparatus involve a radiation source assembly that outputs radiation along an output path of travel, and that has a support section configured to facilitate support of the assembly so that a position of the assembly can be adjusted approximately pivotally about the output path of travel. According to a different aspect, a method and apparatus involve: generating radiation with a radiation source in a radiation source assembly that is a modular unit; emitting this radiation approximately in a direction; supporting the radiation source near an input port of a radiation guide so that the radiation from the radiation source enters the input port, and so that the radiation source is positionally adjustable toward and away from the input port parallel to the direction; and supplying radiation through the radiation guide from the input port to an output port thereof.

Description:
This application claims the priority under 35 U.S.C. §119 of provisional application No. 61/220,378 filed Jun. 25, 2009, the entire disclosure of which is hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general to optical systems and, more particularly, to techniques for generating monochromatic or polychromatic radiation. 
     BACKGROUND 
     Due to advances in light emitting diode (LED) technology, LED&#39;s are becoming progressively more widely used in many fields. For example, there are image projection systems in which light from one or more LEDs is directed onto a digital micro-mirror device (DMD), and then routed to and displayed on a screen. Although existing LED source assemblies have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects. For example, existing LED source assemblies tend to be bulky rather than compact, do not permit easy and rapid interchange of monochromatic and polychromatic source assemblies, do not permit easy and rapid replacement of a failed LED, often require realignment after LED replacement, do not provide adequate adjustment to maximize coupling of LED light into other optics, and do not provide adequate rotational adjustment to align an output beam with other optics in order to achieve uniform brightness throughout a projected image. Further, existing LED source assemblies may not be entirely suitable for applications where daytime brightness and/or source lifetime are important. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention will be realized from the detailed description that follows, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagrammatic perspective view of an apparatus that is a polychromatic light emitting diode (LED) light source assembly embodying aspects of the invention. 
         FIG. 2  is a diagrammatic sectional side view taken along line  2 - 2  in  FIG. 1 . 
         FIG. 3  is a diagrammatic sectional top view taken along line  3 - 3  in  FIG. 1 . 
         FIG. 4  is a diagrammatic perspective view of a light pipe that is a component of the assembly of  FIG. 1 . 
         FIG. 5  is a diagrammatic perspective view showing the light pipe of  FIG. 4 , with a frame that is another component of the assembly of  FIG. 1 . 
         FIG. 6  is a diagrammatic perspective view of a portion of the assembly of  FIG. 1  that is similar to  FIG. 5 , but that also includes some additional components. 
         FIG. 7  is a diagrammatic perspective view of a portion of the assembly of  FIG. 1  that is similar to  FIG. 6 , but that also includes some additional components. 
         FIG. 8  is a diagrammatic perspective bottom view of an LED module that is a further component of the assembly of  FIG. 1 . 
         FIG. 9  is a diagrammatic fragmentary perspective view showing a projector, with the assembly of  FIG. 1  installed thereon. 
         FIG. 10  is a diagrammatic side view of a monochromatic LED light source assembly that is an alternative embodiment of the polychromatic LED light source assembly of  FIG. 1 . 
         FIG. 11  is a diagrammatic sectional side view taken along the line  11 - 11  in  FIG. 10 . 
         FIG. 12  is a diagrammatic bottom view of the apparatus of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a diagrammatic perspective view of an apparatus that is a polychromatic light emitting diode (LED) light source assembly  10  embodying aspects of the invention.  FIG. 2  is a diagrammatic sectional side view taken along line  2 - 2  in  FIG. 1 .  FIG. 3  is a diagrammatic sectional top view taken along line  3 - 3  in  FIG. 1 .  FIG. 4  is a diagrammatic perspective view of a radiation guide or light pipe  16  that is a component of the assembly  10  of  FIG. 1 . 
     With reference to  FIGS. 2 and 4 , the light pipe  16  includes a horizontally-extending main tube  17  having four walls and a rectangular cross-sectional shape. The main tube  17  has a central opening with a rectangular cross-sectional shape. At one end of the main tube  17 , the central opening serves as an outlet port  19  of the light pipe  16 . The opposite end of the main tube  17  is closed by an inclined end wall  18 . Three spaced, tubular chimneys  22 ,  23  and  24  each extend upwardly from a top wall of the main tube  17 . The chimneys  22 - 24  each have four walls arranged to form the frustrum of a four-sided pyramid. Thus, the chimneys  22 - 24  each have a cross-sectional size that tapers progressively in an upward direction. The chimneys each have therein a vertical opening of rectangular cross-section that tapers in cross-sectional size in an upward direction. The upper ends of the chimneys  22 ,  23  and  24  serve as respective inlet ports  27 ,  28  and  29  for radiation, as explained in more detail later. 
     In the disclosed embodiment, the walls of the main tube  17  and each of the chimneys  22 - 24  are all made of a material that is commonly known as float glass. However, they could alternatively be made of any other suitable material. The inner side of each of these walls has a reflective coating of a known type that is not separately illustrated in the drawings, and that is highly reflective to all radiation within the visible spectrum. The various walls of float glass in the light pipe  16  are fixedly secured to each other by a suitable adhesive. In the disclosed embodiment, the adhesive is a two-part epoxy adhesive, and in particular is ECCOBOND® 45 SC mixed at a ratio of 1:1 with a catalyst that is ECOB #15 SC, both of which are available commercially from Emerson &amp; Cuming of Billerica, Mass. 
     With reference to  FIG. 2 , the top wall of the main tube  17  has three spaced, rectangular openings  31 ,  32  and  33  extending vertically through it, where the openings  31 - 33  are each aligned with the lower end of a respective one of the chimneys  22 ,  23  and  24 . The opening  33  has nothing in it. The openings  31  and  32  each have a respective dichroic mirror  37  or  38  adhesively secured therein. The dichroic mirror  37  is transmissive to blue light, but is reflective to light of other colors propagating within the main tube  17 , including green and red light. The dichroic mirror  38  is transmissive to green light, but is reflective to light of other colors propagating within the main tube  17 , including blue and red light. 
     Two further dichroic mirrors  42  and  43  are adhesively secured within the main tube  17  at spaced locations along a centerline  51  of the central opening through the main tube. The mirrors  42  and  43  each extend at an angle of 45° with respect to the centerline  51 . The mirror  42  is located directly below opening  31 , and the mirror  43  is located directly below opening  32 . The dichroic mirror  42  is transmissive to green light and red light, and is reflective to blue light. The dichroic mirror  43  is transmissive to red light, and is reflective to green light. In the disclosed embodiment, the mirrors  31 - 32  and  42 - 43  are each fixedly secured in place with an optical adhesive that, in the disclosed embodiment, is available commercially under the tradename NORLAND 61 from Norland Products, Inc. of Cranbury, N.J. The NORLAND 61 adhesive cures when exposed to ultraviolet light. Alternatively, the mirrors  31 - 32  and  42 - 43  could be secured in place using any other suitable adhesive. 
     Blue radiation is generated in a manner discussed later, is divergent, propagates downwardly along a path of travel  46 , and enters the inlet port  27 . Green radiation is generated in a manner discussed later, is divergent, travels downwardly along a path of travel  47 , and enters the inlet port  28 . Red radiation is generated in a manner discussed later, is divergent, travels downwardly along a path of travel  48 , and enters the inlet port  29 . 
     With reference to  FIG. 2 , the red radiation traveling downwardly through chimney  24  passes through the opening  33 , is reflected by the reflective coating on the end wall  18 , and then travels horizontally through the main tube  17 , where it passes successively through the dichroic mirrors  43  and  42 , and then exits through the outlet port  19  along a path of travel  49  ( FIG. 4 ). The path of travel  49  is coincident with the centerline  51 . Green radiation traveling downwardly through chimney  23  passes through the dichroic mirror  38 , is reflected by the dichroic mirror  43 , and then travels horizontally through the main tube  17 , where it passes through the dichroic mirror  42 , and then exits through the outlet port  19  along the path of travel  49 . Blue radiation traveling downwardly through chimney  22  passes through the dichroic mirror  37 , is reflected by the dichoric mirror  42 , and then travels horizontally through the main tube  17  and exits through the outlet port  19  along the path of travel  49 . 
     As discussed above, all walls of the light tube  16  have a highly reflective coating on the inner side thereof. Thus, to the extent radiation traveling through any of the chimneys  22 - 24  or through the main tube  17  strikes any wall of the light tube, virtually all of that radiation will be reflected and continue traveling through the light pipe to the outlet port  19 . The dichroic mirrors  37 - 38  and  42 - 43  also help to keep radiation within the main tube  17 , and moving along the main tube  17  toward the outlet port  19 . In addition, reflections from the walls and mirrors help to thoroughly mix or homogenize the blue light, green light and red light traveling to the outlet port  19  from the respective inlet ports  27 - 29 . 
       FIG. 5  is a diagrammatic perspective view showing the light pipe  16  of  FIG. 4 , with a frame  56  that is another component of the assembly  10  of  FIG. 1 . In the disclosed embodiment, the frame  56  is made of commercially-available aluminum alloy 6061-T6, but could alternatively be made of any other suitable material. As shown in  FIG. 5 , the frame  56  has in an underside thereof a channel or groove  58  that extends the entire length of the frame. The frame  56  thus has an approximately U-shaped cross-sectional shape, including a horizontal top wall and two parallel, spaced side walls that extend vertically downwardly from opposite side edges of the top wall. The frame  56  also has three spaced rectangular openings through the top wall thereof that each communicate with the channel  58 . 
     With reference to  FIG. 3 , an inner side of one side wall of the frame has four spaced, coplanar reference surfaces  66 ,  67 ,  68  and  69 . With reference to  FIG. 2 , an underside of the top wall has two spaced, coplanar reference surfaces  72  and  73 . Referring again to  FIG. 5 , the side wall with reference surfaces  66 - 69  also has two threaded openings  76  and  77  that are near one end, that are horizontally spaced, and that extend horizontally into this side wall from the outer side thereof. Above the openings  76  and  77 , there is a downwardly facing edge surface  78 . A similar edge surface  79  is provided on the opposite side of the frame  56 . With reference to  FIG. 5 , the frame  56  has six threaded openings  81 ,  82 ,  83 ,  84 ,  85  and  86  that extend vertically downwardly into the top wall. The openings  81  and  82  are disposed on opposite sides of the opening  61 , the openings  83  and  84  are disposed on opposite sides of the opening  62 , and the openings  85  and  86  are disposed on opposite sides of the opening  63 . 
     With reference to  FIGS. 2 ,  3  and  5 , the main tube  17  of the light pipe  16  is received within the channel  58  of the frame  56 , except that the end with outlet port  19  projects outwardly beyond one end of the frame  56 . The chimneys  22 - 24  each extend upwardly through a respective one of the openings  61 - 63 . The openings  61 - 63  are larger in size than the lower ends of the chimneys, such that the edges of the openings  61 - 63  do not contact the chimneys. As shown in  FIG. 3 , one side wall of the main tube  17  engages the four reference surfaces  66 - 69  on the frame, in order to align the main tube with the frame in one horizontal direction. As shown in  FIG. 2 , the top wall of the main tube  17  engages the two reference surfaces  72  and  73  on the frame, in order to align the main tube with the frame in a vertical direction. This cooperation between the main tube  17  and the reference surfaces  66 - 69  and  72 - 73  ensures that that centerline  51  of the main tube  17  is very accurately positioned at a particular location in relation to the frame  56 . With reference to  FIG. 5 , a not-illustrated assembly jig is used to accurately position the frame with respect to the light pipe  16  in another horizontal direction, so that the main tube  17  extends outwardly a specific distance  91  beyond an end of the frame  56 . A quantity of the above-mentioned ECCOBOND® epoxy adhesive is then injected into gaps between outer surfaces of the main tube  17  and inner surfaces of the channel  58  in the frame  56 , and then is allowed to harden, in order to fixedly secure the light pipe  16  in place with respect to the frame  56 , with very accurate alignment therebetween. 
       FIGS. 1 ,  2  and  3  show a mounting part  101 . In the disclosed embodiment, the mounting part  101  is made of commercially-available aluminum alloy 6061-T6, but could alternatively be made of any other suitable material. The mounting part  101  includes an approximately circular plate or disk  103  having a flat  104  on one side thereof. The disk  103  can also be considered to be an annular flange. One side of the disk is disposed adjacent an end surface of the frame  56 . On the opposite side of the disk, an annular planar surface  105  faces axially away from the frame  56 . A cylindrical projection  106  extends outwardly beyond the surface  105  from the center of the disk in a direction away from the frame  56 . The cylindrical projection  106  is approximately concentric with and of smaller diameter than the disk  103 . The projection  106  has a radially-outwardly facing annular cylindrical surface  107  thereon. 
     The mounting part  101  has a rectangular opening  108  that extends axially through the disk  103  and the projection  106 , and the main tube  17  of the light pipe  16  extends through this opening  108 . The dimensions of the opening  108  are somewhat larger than the dimensions of the main tube  17 , so that the edges of the opening  108  do not contact the main tube. The disk  103  has three arcuate slots  111 ,  112  and  113  that open axially therethrough, that each extend approximately circumferentially, and that are angularly spaced with respect to each other. 
     Two spaced, parallel legs  116  and  117  project axially from the side of disk  103  opposite the projection  106 , and are disposed on opposite sides of the frame  56 . The top edges of the legs  116  and  117  respectively engage the downwardly-facing edge surfaces  78  and  79  on the frame, in order to accurately position the mounting part  101  in two dimensions with respect to the frame  56  and the main tube  17  of the light pipe. The leg  116  has two openings  118  and  119  that are horizontally spaced, that extend horizontally through the leg, and that are respectively aligned with the openings  77  and  76  in the side wall of the frame  56 . Two screws  122  and  123  have threaded shanks that respectively extend through the openings  118  and  119 , and engage the threaded openings  77  and  76 . The openings  118  and  119  have diameters larger than the diameters of the screw shanks, thereby permitting the legs  116  and  117  to move transversely with respect to the screws  122  and  123 . As a result, the legs are positioned through the engagement of their top edges with the edge surfaces  78  and  79  on the frame  56 , and not by engagement of the screws with edges of the openings  76  and  77 . The screws  122  and  123  urge an inner surface of the leg  116  against a surface on the outer side of frame  56 , which also helps to accurately position the mounting part  101  in a third dimension with respect to the frame  56 . In the disclosed embodiment, the screws  122  and  123  are each made of stainless steel, but they could alternatively be made of any other suitable material. The cylindrical surface  107 , the approximately circular disk  103  and the arcuate slots  111 - 113  are all substantially concentric to the centerline  51  of the main tube  17 . 
     The leg  116  has a small opening  126  that extends horizontally therethrough between the screws  122  and  123 , and the leg  117  has two horizontally-spaced openings  127  and  128  that extend horizontally therethrough. After the mounting part  101  has been secured to the frame  56  with the screws  122  and  123 , a quantity of an adhesive is injected through the openings  126 ,  127  and  128  in order to fill gaps between the inner surfaces of legs  116 - 117  and the outer surfaces of frame  56 , and then is allowed to harden to help fixedly secure the mounting part to the frame. In the disclosed embodiment, the adhesive is the above-mentioned ECCOBOND® epoxy adhesive, but could alternatively be any other suitable adhesive. 
       FIG. 6  is a diagrammatic perspective view of a portion of the assembly  10  of  FIG. 1  that is similar to  FIG. 5 , but that also includes some additional components. With reference to  FIGS. 2 and 6 , the assembly  10  includes three cylindrical collector tubes  141 ,  142  and  143 . In the disclosed embodiment, the collector tubes  141 - 143  are each made of commercially-available aluminum alloy 6061-T6, but they could alternatively be made of any other suitable material. The collector tubes  141 - 143  each have a lower end that engages the top surface of the frame  56 , and each have two tabs that project radially outwardly from the lower end on opposite sides thereof, four of these six tabs being visible in the drawings at  146 - 149 . The six tabs each have a hole that extends vertically therethrough, but that is not visible in the drawings. The holes in the tabs are each aligned with a respective one of the six holes  81 - 86  ( FIG. 5 ) in the frame  56 . 
     The collector tubes  141 - 143  are held in place by six screws, four of which are visible in the drawings at  156 - 159 . In the disclosed embodiment, the six screws  156 - 159  are all made of stainless steel, but they could alternatively be made of any other suitable material. The six screws  156 - 159  each have a threaded shank that extends vertically downwardly through the hole in a respective one of the six tabs  146 - 149 , and threadedly engages a respective one of the six holes  81 - 86  ( FIG. 5 ) in the frame  56 . The holes in the six tabs have diameters that are somewhat larger than the diameters of the threaded shanks of the screws, thereby allowing a limited amount of movement of the collector tubes  141 - 143  in horizontal directions with respect to the frame  56  when the six screws  156 - 159  are in place but not yet fully tightened. This allows independent positioning of the collector tubes with respect to each other and with respect to the input ports  27 - 29  of the chimneys  22 - 24 . The two screws for each collector tube can be tightened in order to fixedly secure that collector tube in a selected position with respect to the frame. 
     Each of the collector tubes  141 ,  142  and  143  has a respective threaded hole  167 ,  168  or  169  that extends horizontally into a side wall thereof. These holes are located approximately halfway between the upper and lower ends of the collector tubes  141 - 143 . The collector tube  141  has, on diametrically opposites sides thereof, two recesses  171  and  172  that extend downwardly into the tube wall from an upper end thereof. The collector tubes  142  and  143  have similar recesses at  173 ,  174 ,  175  and  176 . 
     Fixedly secured within the upper end of each collector tube  141 ,  142  and  143  is a respective cup-shaped support part  181 ,  182  or  183 . In the disclosed embodiment, the support parts  181 - 183  are each made of commercially-available aluminum alloy 6061-T6, but could alternatively be made of any other suitable material. Each of the support parts  181 - 183  has a circular top wall with a respective rectangular opening  186 - 188  extending vertically through the center thereof. The circular top walls of the support parts  181 - 183  each have a top surface that is approximately flush with the bottom surfaces of the two adjacent recesses  171 - 172 ,  173 - 174  or  175 - 176 . Each of the support parts  181 - 183  also has a respective annular flange  191 - 193  that extends downwardly from a peripheral edge of the circular top wall. 
     Each annular flange  191 - 193  has a cylindrical exterior surface that snugly engages a cylindrical inner surface of the associated collector tube  141 - 143 . As can be seen in  FIG. 2 , the cylindrical exterior surfaces of the flanges  191 - 193  each have a shallow circumferential recess therein. An adhesive is injected into each of these circumferential recesses using not-illustrated holes through the walls of the collector tubes  141 - 143 , in order to fixedly bond the support parts  181 - 183  to the collector tubes  141 - 143 , respectively. In the disclosed embodiment, the adhesive is the above-mentioned ECCOBOND® epoxy adhesive, but could alternatively be any other suitable adhesive. 
     The chimneys  22 - 24  of the light pipe  16  have upper ends that each extend upwardly through a respective opening  186 - 188  in a respective support part  181 - 183 . The openings  186 - 188  have a size larger than the portions of the chimneys disposed therein, so that the edges of the openings do not engage the chimneys. In this regard, with each of the six screws  156 - 159  slightly loosened, a not-illustrated assembly jig is used to position the collector tubes  141 - 143  relative to the frame  56  and the light pipe  16 , so that the chimneys  22 - 24  are each accurately positioned within the associated collector tube  141 - 143 . The six screws  156 - 159  are then each tightened in order to fixedly secure the collector tubes in position with respect to the frame. An adhesive is then applied in the gap between each of the chimneys  22 - 24  and the edges of the corresponding opening  186 - 188 , in order to help support each of the chimneys  22 - 24  in the proper position relative to the corresponding collector tube  141 - 143 . In the disclosed embodiment, the adhesive is the above-mentioned ECCOBOND® epoxy adhesive, but could alternatively be any other suitable adhesive. 
       FIG. 7  is a diagrammatic perspective view of a portion of the assembly  10  of  FIG. 1  that is similar to  FIG. 6 , but that also includes some additional components. With reference to  FIGS. 2 and 7 , the assembly  10  includes three cup-shaped adjust tubes  201 ,  202  and  203 . In the disclosed embodiment, the adjust tubes  201 - 203  are each made of commercially-available aluminum alloy 6061-T6, but could alternatively be made of any other suitable material. The adjust tubes  201 - 203  each have a respective circular top wall  206 ,  207  or  208 , and a respective cylindrical flange  211 ,  212  or  213  that extends downwardly from the peripheral edges of the top wall. The adjust tubes  201 - 203  are respectively placed over the collector tubes  141 - 143 . The flanges  211 - 213  of the adjust tubes  201 - 203  each have a cylindrical inner surface that slidably engages a cylindrical outer surface on the associated collector tube  141 - 143 , in order to permit vertical sliding movement of each adjust tube  201 - 203  in relation to the associated collector tube  141 - 143 . 
     The cylindrical flanges  211 - 213  of the adjust tubes  201 - 203  have respective slots  216 - 218  that extend vertically, and that open horizontally through the flanges. In addition, the flanges  211 - 213  each have four holes extending horizontally therethrough at circumferentially spaced locations, but only three of these holes are visible in the drawings at  221 - 223 . These holes each communicate at the inner end with a shallow circumferential recess provided in the cylindrical inner surface of the associated flange  211 - 213 . The top walls  206 - 208  of the adjust tubes  201 - 203  each have extending vertically therethrough a respective opening  226 - 228  of approximately rectangular shape. These openings  226 - 228  receive the upper ends of the respective chimneys  221 - 224  of the light pipe  16 , and are sufficiently large so that the edges of the openings do not contact the chimneys. 
     The top wall  206  of the adjust tube  201  has two threaded openings  231  and  232  that extend vertically downwardly into it, on diametrically opposite sides of the rectangular opening  226 . The top wall  207  of the adjust tube  202  has two similar threaded holes  233  and  234 , and the top wall  208  of the adjust tube  203  has two similar threaded holes  235  and  236 . Two cylindrical locating pins  241  and  242  have lower ends that are snugly received with a friction fit in respective cylindrical holes provided in the top of the adjust tube  201 , and have upper ends that project upwardly beyond the planar top surface of the top wall  206  of the adjust tube  201 . The adjust tube  202  has two similar locating pins  243  and  244 , and the adjust tube  203  has two similar locating pins  245  and  246 . In the disclosed embodiment, the locating pins  241 - 246  are each made of stainless steel, but they could alternatively be made of any other suitable material. 
     A shallow recess  251  is provided in the top wall  206  of the adjust tube  201 , on one side thereof. Similar recesses  252  and  253  are respectively provided in the top walls  207  and  208  of the adjust tubes  202  and  203 . Three screws  256 - 258  each have a threaded shank that extends through a respective one of the vertical slots  216 - 218 , and threadedly engages a respective one of the threaded holes  167 - 169  ( FIG. 6 ) in the collector tubes  141 - 143 . In the disclosed embodiment, the screws  256 - 258  are each made of stainless steel, but they could alternatively be made of any other suitable material. When the screws  256 - 258  are not fully tightened, each of the adjust tubes  201 - 203  can move vertically with respect to the associated collector tube  141 - 143 . When the adjust tubes  201 - 203  are in a suitable vertical position, the screws  256 - 258  can be tightened to releasably secure the adjust tubes against vertical movement with respect to the collector tubes  141 - 143 . An adhesive can be injected through the twelve openings  221 - 223  and into the circumferential recesses in the flanges  211 - 213 , and then allowed to harden, in order to help fixedly secure the adjust tubes  201 - 203  against vertical movement with respect to the collector tubes  141 - 143 . In the disclosed embodiment, the adhesive is the above-mentioned ECCOBOND® epoxy adhesive, but could alternatively be any other suitable adhesive. 
     With reference to  FIGS. 1 and 2 , three LED modules  281 - 283  are each supported on top of a respective one of the adjust tubes  201 - 203 . The LED module  281  generates blue light and emits it downwardly into the chimney  22 , the LED module  282  generates green light and emits it downwardly into the chimney  23 , and the LED module  283  generates red light and emits it downwardly into the chimney  24 . In the disclosed embodiment, the LED modules  281 - 283  are parts that are each obtained commercially under the tradename PHLATLIGHT® as part number PT 85 from Luminus Devices, Inc. of Billerica, Mass. Aside from the fact that they produce different colors, the LED modules  281 - 283  are effectively identical, and therefore only the LED module  281  will be described in greater detail below. 
       FIG. 8  is a diagrammatic perspective bottom view of the LED module  281 . The LED module  281  has a plate-like body  285  with a generally planar bottom surface  286 . The bottom surface has a rectangular opening with a rectangular transmissive window  287  mounted therein. The window  287  projects downwardly a small distance past the bottom surface  286 , and has horizontal dimensions that are larger than the horizontal dimensions of the rectangular opening  226  through the top of the adjust tube  201 . The LED structure that emits radiation is located just above the window  287 , and the radiation is emitted downwardly through the window  287 . Two spaced cylindrical holes  291  and  292  are disposed on opposite sides of the window  287 , and extend upwardly into the body  285 . Two more cylindrical holes  293  and  294  are disposed on opposite sides of the window  287 , and extend vertically through the body  285 . A block  296  of an electrical insulating material is mounted to an edge portion of the body  285 . The block  296  is vertically thicker than the body  285 , and extends downwardly beyond the bottom surface  286  of the body  285 . Two spaced electrical contacts  297  and  298  project horizontally outwardly from the block  296 . An electrical voltage can be applied between the contacts  297  and  298  through not-illustrated wires, thereby supplying the LED module  281  with electricity that causes it to emit radiation through the window  287 . 
     With reference to  FIGS. 7 and 8 , the LED module  281  rests on top of the adjust tube  201 , with the bottom surface of the module&#39;s window  287  engaging the top surface of the adjust tube  201 , and with the two locating pins  241  and  242  being snugly slidably received within the respective holes  291  and  292 . The cooperation between the pins  241 - 242  and the holes  291 - 292  serves to accurately align the LED module  281  in horizontal directions with respect to the adjust tube  201 , so that the LED structure behind window  287  is aligned with the inlet port  27  at the top of chimney  22 . The recess  251  in the adjust tube  201  receives part of the lower portion of the block  296 . The holes  293  and  294  are aligned with the threaded holes  231  and  232  in the adjust tube  201 . The LED modules  282  and  283  are respectively supported on the adjust tubes  202  and  203  in a similar manner. 
     Three heat sinks  311 ,  312  and  313  are respectively supported on top of the LED modules  281 ,  282  and  283 . In the disclosed embodiment, the heat sinks  311 - 313  are each made of copper, but could alternatively be made of any other suitable material. The heat sinks serve to receive and dissipate heat emitted by the LED modules. The heat sinks  311 ,  312  and  313  include respective heat-conducting plates  316 ,  317  and  318  that each have a bottom surface engaging the top surface of a respective one of the LED modules  281 ,  282  and  283 . To enhance heat transfer from the LED modules to the horizontal plates, a thermally-conducting material is provided between the LED modules  281 - 283  and the corresponding plates  316 - 318 . In the disclosed embodiment, this material is a thermal joint compound available commercially under catalog number 120-2 from Wakefield Solutions, Inc. of Pelham, N.H. Alternatively, however, it would be possible to use any other suitable thermally-conductive material. 
     The heat sink  311  also includes a plurality of parallel and thermally-conductive spines  321  that are fixedly secured at their lower ends to and extend vertically upwardly from the horizontal plate  316 . The heat sinks  312  and  313  each include a plurality of similar spines  322  and  323 , respectively. With reference to  FIG. 2 , two screws  326  and  327  extend through spaced vertical holes in the plate  316  of the heat sink  311 , through the holes  293  and  294  ( FIG. 8 ) in the LED module  281 , and threadedly engage the holes  231  and  232  ( FIG. 7 ) in the adjust tube  201 . The screws  326  and  327  fixedly couple the LED module  281  and the heat sink  311  to the adjust tube  201 . In a similar manner, two screws  328  and  329  fixedly couple the heat sink  312  and the LED module  282  to the adjust tube  202 , and two screws  330  and  331  fixedly couple the heat sink  313  and the LED module  283  to the adjust tube  203 . In the disclosed embodiment, the screws  326 - 331  are each made of stainless steel, but they could alternatively be made of any other suitable material. 
     In the assembled state of the assembly  10 , and as shown in  FIGS. 2 and 8 , the windows  287  of the LED modules  281 ,  282  and  283  are each disposed a small distance above the upper end of the corresponding chimney  22 ,  23  or  24  of the light pipe  16 . The downward beams of radiation emitted by the LED modules  281 - 283  are diverging beams, where the diverging rays are spread over an angle of divergence that can be as high as about 160°. In order to maximize the efficiency with which the emitted light is coupled into the inlet ports at the upper ends of the chimneys  22 - 24 , the assembly  10  provides the capability to independently adjust the position of each of the LED modules  281 - 283  in multiple dimensions relative to the inlet port at the upper end of a respective one of the chimneys  22 - 24 . 
     Assume for the sake of discussion that there is a three-axis reference system having orthogonal X, Y and Z axes, where the X axis extends parallel to the horizontal centerline  51  of the main tube  17 , and the Z axis extends vertically. The screw  256  can be loosened slightly, and then the adjust tube  201  can be moved vertically, or in other words parallel to the Z axis. This allows the LED in module  281  to be moved closer to or further from the inlet port at the upper end of the chimney  22 , in order to maximize the amount of emitted light that is coupled into the chimney. The screw  256  can then be tightened when the adjust tube  201  is in a position that optimizes this coupling. Similarly, the screws  156  and  157  can each be loosened slightly, and the oversize holes in the tabs  146  and  147  permit movement of the collector tube  141 , adjust tube  201  and LED module  281  in horizontal directions corresponding to both the X and Y axes, in order to ensure that the light emitted by LED module  281  is centered over the inlet port  27  at the top of the chimney  22 . In a similar manner, the LED modules  282  and  283  can each be adjusted in three different dimensions. In this manner, the LED modules  281 ,  282  and  283  can each be adjusted entirely independently in three dimensions relative to each other and relative to the frame  56 . 
     Assume for the sake of discussion that the LED module  281  eventually fails, and needs to be replaced. The two screws  326  and  327  ( FIG. 2 ) can be removed, the heat sink  311  and LED module  281  can then be removed, and an identical replacement LED module can be installed on top of the adjust tube  201 . The top surface of the adjust tube  201  and the two locating pins  241  and  242  will very accurately position the replacement LED module with respect to the inlet port  27  at the upper end of the chimney  22 . A quantity of the previously-discussed thermal joint compound can then be applied to the top surface of the replacement LED module, the heat sink  311  can be put in position, and the two screws  326  and  327  can be reinstalled in order to fixedly secure the heat sink  311  and replacement LED module to the adjust tube  201 . In this manner, any of the LED modules  281 - 283  can be quickly and easily replaced, and will automatically be accurately positioned with respect to the light pipe  16  so as to provide optimum coupling efficiency for emitted radiation, typically without need for any re-alignment. In the unlikely event that the coupling efficiency of a replaced module is not optimum, the position of that module relative to the associated chimney can be easily adjusted in one or both of the X and Y directions, by simply loosening two screws, by making an adjustment and by then tightening the screws. 
       FIG. 9  is a diagrammatic fragmentary perspective view of a projector  381  having the assembly  10  of  FIG. 1  installed thereon. The projector  381  is merely one example of a variety of different devices with which the assembly  10  can be used. The projector  381  includes a housing  382  with a circular disk  383  fixedly secured thereon. The circular disk  383  can also be considered to be an annular flange. The circular disk  103  of the assembly  10  is disposed against the circular disk  383  of the projector  381 , with the annular surface  105  slidably engaging a complementary annular surface provided on the housing of the projector  381 . The circular disk  383  has a not-illustrated circular opening in the center thereof, with a radially-inwardly facing annular cylindrical surface that is only slightly larger in diameter than and slidably engages the radially-outwardly facing annular cylindrical surface  107  on the mounting part  101 . The sliding engagement of the two surfaces  105  and  107  on the assembly  382  with the two complementary surfaces on the housing  382  serves to accurately position the light source assembly  10  in relation to the housing. In particular, this sliding engagement ensures that that centerline  51  of the main tube  17  is very accurately positioned at a particular location in relation to the housing  382  of the projector  381 . Three screws, two of which are visible in the drawings at  386  and  387 , each extend through a respective one of the slots  111 ,  112  and  113  ( FIG. 1 ) in the circular disk  103 , and engage a respective threaded hole that is provided in the circular disk  383 . In the disclosed embodiment, the three screws  386 - 387  are each made of stainless steel, but could alternatively be made of any other suitable material. 
     The projector  381  has therein a not-illustrated digital micro-mirror device (DMD) of a known type, which includes a rectangular array of micro-mirrors. Light exiting the outlet port  19  ( FIG. 1 ) of the LED light source assembly  10  is a beam of approximately rectangular cross-sectional shape, and it is desirable that this rectangular beam be accurately aligned with the rectangular array of micro-mirrors, in order to provide uniform brightness across images produced by reflections from the micro-mirrors. To achieve this, the three screws  386 - 387  can be loosened slightly, and then the entire assembly  10  can be pivoted or “clocked” in directions  391  about the centerline  51  ( FIG. 2 ) of the main tube  17  of light pipe  16 . The sliding engagement of the two surfaces  105  and  107  on the assembly  10  with the two complementary surfaces on the housing  382  maintains the accurate positioning of the centerline  51  in relation to the housing, even during this clocking movement. When the rectangular beam from the outlet port  19  has been accurately aligned in this manner with the rectangular array of micro-mirrors, the three screws  386 - 387  can be tightened in order to fixedly secure the assembly  10  in that particular angular position with respect to the projector  381 . 
     Due in part to the multi-folded light path provided by the light pipe  16 , the LED light source assembly  10  is a very compact assembly that will readily fit in a limited space. In addition, a number of parts have a generally circular shape that helps to reduce the thickness and amount of material in the assembly  10 , thereby minimizing weight without compromising strength. 
       FIG. 10  is a diagrammatic side view of a monochromatic LED light source assembly  410  that is an alternative embodiment of the polychromatic LED light source assembly  10  of  FIG. 1 .  FIG. 11  is a diagrammatic sectional side view taken along the line  11 - 11  in  FIG. 10 .  FIG. 12  is a diagrammatic bottom view of the apparatus  410  of  FIG. 10 . In the disclosed embodiment, the assembly  410  outputs only green light, but it could alternatively output only some other waveband, such as blue light, red light, white light, or some other selected portion of the spectrum. 
     With reference to  FIGS. 10 and 11 , the portion of the assembly  410  disposed above an imaginary horizontal plane  411  is generally equivalent in structure and function to the portion of the assembly  10  ( FIG. 1 ) disposed above the tabs  146  and  147  of the collector tube  141 . Accordingly, the discussion that follows will focus primarily on the structure below the plane  411 . In more detail, with reference to  FIGS. 10 and 11 , the assembly  410  includes a light pipe  22  that is effectively identical to the chimney  22  of the light pipe  16  ( FIG. 2 ). The light pipe or chimney  22  has a rectangular inlet port  27  at an upper end thereof, and a rectangular outlet port  19  at a lower end thereof. 
     The assembly  410  includes a collector tube  441 . As mentioned above, the portion of collector tube  441  disposed above the imaginary plane  411  is similar to the upper portion of the collector tube  141  in the embodiment of  FIGS. 1-9 . Below the imaginary plane  411 , at the lower end of the collector tube  441 , there is a mounting portion  446  that is an integral part of the collector tube. The mounting portion  446  is similar to the mounting part  101  in the embodiment of  FIGS. 1-9 . With reference to  FIGS. 10-12 , the mounting portion  446  includes a circular plate or disk  447  that has a flat  448  on one side thereof. The disk  447  can also be considered to be an annular flange. The mounting portion  447  has an annular, planar surface  449  that faces axially downwardly in  FIGS. 10 and 11 . The mounting portion  446  includes a cylindrical projection  450  that extends downwardly beyond the surface  449  from the lower side of the disk  447 . The projection  450  has a radially-outwardly facing annular cylindrical surface  452  thereon, which is substantially concentric to a centerline  451  ( FIG. 11 ) of the light pipe  22 . 
     A rectangular opening  453  extends axially through the disk  447  and the projection  450 . The light pipe  22  extends through the rectangular opening  453 , but the opening  453  has a size larger than the associated portion of the light pipe  22 , so that the edges of the opening do not contact the light pipe. Four angularly-spaced openings, only two of which are visible in the drawings at  456  and  457 , extend radially through the projection  450  from the cylindrical surface  452  to the rectangular opening  453 . During assembly, a not-illustrated assembly jig is used to accurately position the lower portion of the light pipe  22  within the rectangular opening  453 , and to position the upper portion of the light pipe within the rectangular opening in the support part  181 . During this positioning, the light pipe  22  is moved in two orthogonal directions (parallel to an X axis and Y axis) with respect to the collector tube  441 , until the centerline  451  of the light pipe  22  is very accurately positioned at a particular location in relation to the collector tube  441 . After the light pipe  22  has been properly positioned in this manner, an adhesive is injected through the four openings  456 - 457  and into the gap between the light pipe  22  and surfaces of the opening  453 , and then is allowed to harden, in order to secure this portion of the light pipe against movement relative to the mounting portion  446 . In addition, the adhesive is used to secure the upper portion of the light pipe  22  in relation to the support part  181 , as described earlier. In the disclosed embodiment, the adhesive is the above-mentioned ECCOBOND® epoxy adhesive, but could alternatively be any other suitable adhesive. With reference to  FIG. 12 , the disk  447  has three arcuate slots that open axially therethrough, that extend circumferentially with respect to the centerline  451 , and that are uniformly angularly spaced about the centerline  451 . 
     At the lower end of the apparatus  410 , there is a mask part  481  that is a bent metal plate. In the disclosed embodiment, the mask part  481  is made of commercially-available aluminum alloy 6061-T6, but could alternatively be made of any other suitable material. The mask part  481  includes a horizontally-extending central portion  482 , and two parallel legs  483  and  484  that each extend upwardly from a respective side of the central portion  482 , and that are disposed on opposite sides of the lower end of the light pipe  22 . An opening  483  extends vertically through the central portion  482 , and is aligned with the outlet port  19  at the lower end of the light pipe  22 . The opening  487  has an approximately rectangular shape, except that the ends are slightly rounded. Alternatively, however, the opening could have some other shape. 
     Two openings  488  and  489  respectively extend horizontally through the legs  483  and  484 . During assembly, a not-illustrated assembly jig is used to accurately position the mask part  481  with respect to the lower end of the light pipe  22 . An adhesive is injected through the openings  488 - 489  and into the gap between each of the legs  483  and  484  and the lower end of light pipe  22 , and then is allowed to harden, in order to fixedly secure the mask part  481  against movement with respect to the light pipe. In the disclosed embodiment, the adhesive is the above-mentioned ECCOBOND® epoxy adhesive, but it could alternatively be any other suitable adhesive. 
     In use, the monochromatic LED light source assembly  410  of  FIG. 11  can be bolted to the projector  381  of  FIG. 9  in place of the polychromatic LED light source assembly  10 , and can be clocked in the directions  391  in the same manner already described above for assembly  10 . It will be recognized that the assembly  410  provides many of the same benefits already described above in association with the assembly  10 . 
     Although selected embodiments have been illustrated and described in detail, it should be understood that a variety of substitutions and alterations are possible without departing from the spirit and scope of the present invention, as defined by the claims that follow.