Abstract:
Discrete light fiber inputs for high powered image projector display systems are disclosed herein. Various embodiments disclosed herein may employ a bundle of light fiber inputs, a diffuser and reducing relay optic to convert the fiber input array into a smaller pattern of spots that may be interfaced to a projector display system that may perform light recycling. Many embodiments herein may facilitate higher power laser light for illumination and, possibly, recycling. In these embodiments, laser fibers may be individually collimated and illuminate a diffuser. The diffuser spots may be then imaged through a common path relay that can be resized to allow room for the individual lasers and collimation lenses. The diffuser spots may be imaged through holes in a mirror that is on the input side of an integration rod which recycles the light.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Patent Application No. 62/127,098, filed on Mar. 2, 2015 and U.S. Provisional Patent Application No. 62/099,066, filed on Dec. 31, 2014, each of which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to projector systems and, particularly, to improved light conduits for laser-based image projection systems. 
       BACKGROUND 
       [0003]    Projector systems are now being architected with improvements in dynamic range. Many of these types of improvements are in the area of laser projection systems. Some such laser projections systems may also comprise dual and multi-modulator projector display systems. It may be desirable to improve the performance of these improved image projection systems. 
       SUMMARY 
       [0004]    Conventional fibers and their associated connectors typically may not be grouped together in a small enough pattern to interface with a projector display system that performs light recycling. Discrete light fiber inputs for high powered image projector display systems are disclosed herein. Various embodiments disclosed herein may employ a bundle of light fiber inputs, a diffuser and reducing relay optic to convert the fiber input array into a smaller pattern of spots that may be interfaced to a projector display system that may perform light recycling. Many embodiments herein may facilitate higher power laser light for illumination and, possibly, recycling. In these embodiments, laser fibers may be individually collimated and illuminate a diffuser. The diffuser spots may be then imaged through a common path relay that can be resized to allow room for the individual lasers and collimations lenses. The diffuser spots may be imaged through holes in a mirror that is on the input side of an integration rod which recycles the light. 
         [0005]    In one embodiment, an optical system is disclosed, said system comprising a bundle of light fibers, said bundle transmitting light from at least one light source to an integrating rod, said optical system further comprising: a plurality of light fibers, each light fiber receiving light from a light source; a collimating lens, the collimating lens receiving light from the plurality of light fibers; a diffuser, the diffuser receiving light from the collimating lens; a lens assembly, the lens assembly receiving light from the diffuser; and an optical element, the optical element providing at least one aperture to receive light from the lens assembly to input light into an integrating rod. 
         [0006]    In another embodiment, an image projection display system is disclosed, comprising: a light source; a plurality of light fibers, each light fiber receiving light from the light source; a collimating lens, the collimating lens receiving light from the plurality of light fibers; a diffuser, the diffuser receiving light from the collimating lens; a lens assembly, the lens assembly receiving light from the diffuser; and an optical element, the optical element providing at least one aperture to receive light from the lens assembly; an integration rod module, the integration rod module receiving light from the optical element and transmitting light from said light source to a modulator; and wherein the integration rod module further comprises: a first integrating rod; a second integrating rod; a strap, said strap mechanically mated to the first integrating rod and the second integrating rod, such that the end of the first integrating rod is proximal to the end of the second integrating rod; and further wherein, the strap is glued to the first integrating rod and the second integrating rod. 
         [0007]    Other features and advantages of the present system are presented below in the Detailed Description when read in connection with the drawings presented within this application. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive. 
           [0009]      FIG. 1  depicts one schematic embodiment of an image projector display system as may be suitable for the purposes of the present application. 
           [0010]      FIG. 2  depicts one embodiment of a light conduit module that suffices for the purposes of the present application. 
           [0011]      FIG. 3  depicts another embodiment of a light conduit module that may suffice for the purposes of the present application. 
           [0012]      FIG. 4  depicts one embodiment of a bundle of discrete light fiber input as made in accordance with the principles with the present application. 
           [0013]      FIG. 5A  shows a side view of the embodiment of  FIG. 4 . 
           [0014]      FIG. 5B  depicts one example of ray tracing with improved integrating rod  600  as made in accordance with the principles of the present application. 
           [0015]      FIG. 6  depicts one embodiment of an improved integrating rod module as made in accordance with the principles of the present application. 
           [0016]      FIGS. 7A, 7B and 7C  depict various embodiments of integrating rods. 
           [0017]      FIG. 8  depicts one embodiment of the mechanical mating of a plurality of integrating rods. 
           [0018]      FIG. 9  depicts that the mechanical mating at the straps ( 806 ) should not substantially disturb the critical angle 
           [0019]      FIGS. 10A, 10B and 10C  gives a perspective view, a perspective cut-view and a front, cut-view of one embodiment of additional mechanical supports for the improved integrating rod. 
           [0020]      FIGS. 11, 12 and 13  give plots depicting the potential performance of the glue when applied in different thicknesses. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    As utilized herein, terms “component,” “system,” “interface,” and the like are intended to refer to a computer-related entity, either hardware, software (e.g., in execution), and/or firmware. For example, a component can be a process running on a processor, a processor, an object, an executable, a program, and/or a computer. By way of illustration, both an application running on a server and the server can be a component. One or more components can reside within a process and a component can be localized on one computer and/or distributed between two or more computers. A component may also be intended to refer to a communications-related entity, either hardware, software (e.g., in execution), and/or firmware and may further comprise sufficient wired or wireless hardware to affect communications. 
         [0022]    Throughout the following description, specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense. 
         [0023]    Introduction 
         [0024]    In the field of projector and other display systems, it is desirable to improve both image rendering performance and system efficiency. Several embodiments of the present application describe systems, method and techniques to affect these improvements by employing light field modeling for dual, or multi-modulation display systems. In one embodiment, light source models are developed and used to advantageous effect. Camera pictures of displayed images of known input images may be evaluated to improve light models. In some embodiments, an iterative process may accumulate improvements. In some embodiments, these techniques may be used on moving images to make live adjustments to improve image rendering performance 
         [0025]    Dual modulation projector and display systems have been described in commonly-owned patents and patent applications, including:
       (1) U.S. Pat. No. 8,125,702 to Ward et al., issued on Feb. 28, 2012 and entitled “SERIAL MODULATION DISPLAY HAVING BINARY LIGHT MODULATION STAGE”;   (2) United States Patent Application 20130148037 to Whitehead et al., published on Jun. 13, 2013 and entitled “PROJECTION DISPLAYS”;   (3) United States Patent Application 20110227900 to Wallener, published on Sep. 22, 2011 and entitled “CUSTOM PSFs USING CLUSTERED LIGHT SOURCES”;   (4) United States Patent Application 20130106923 to Shields et al., published on May 2, 2013 and entitled “SYSTEMS AND METHODS FOR ACCURATELY REPRESENTING HIGH CONTRAST IMAGERY ON HIGH DYNAMIC RANGE DISPLAY SYSTEMS”;   (5) United States Patent Application 20110279749 to Erinjippurath et al., published on Nov. 17, 2011 and entitled “HIGH DYNAMIC RANGE DISPLAYS USING FILTERLESS LCD(S) FOR INCREASING CONTRAST AND RESOLUTION” and   (6) United States Patent Application 20120133689 to Kwong, published on May 31, 2012 and entitled “REFLECTORS WITH SPATIALLY VARYING REFLECTANCE/ABSORPTION GRADIENTS FOR COLOR AND LUMINANCE COMPENSATION”.
           all of which are hereby incorporated by reference in their entirety.   
               
 
         [0033]    One Exemplary Physical Architecture 
         [0034]      FIG. 1  shows one possible embodiment of a suitable image projector display system. In this embodiment, the projector display system is constructed as a dual/multi-modulator projector display system  100  that may suffice for the purposes of the present application. Projector system  100  employs a light source  102  that supplies the projector system with a desired illumination such that a final projected image will be sufficiently bright for the intended viewers of the projected image. Light source  102  may comprise any suitable light source possible—including, but not limited to: Xenon lamp, laser(s), coherent light source, partially coherent light sources. As the light source is a major draw of power and/or energy for the entire projector system, it may be desirable to advantageously use and/or re-use the light, so as to conserve the power and/or energy during the course of its operation. 
         [0035]    Light  104  may illuminate a first modulator  106  that may, in turn, illuminate a second modulator  110 , via a set of optional optical components  108 . Light from second modulator  110  may be projected by a projection lens  112  (or other suitable optical components) to form a final projected image upon a screen  114 . First and second modulators may be controlled by a controller  116 —which may receive input image and/or video data. Controller  116  may perform certain image processing algorithms, gamut mapping algorithms or other such suitable processing upon the input image/video data and output control/data signals to first and second modulators in order to achieve a desired final projected image  114 . In addition, in some projector systems, it may be possible, depending on the light source, to modulate light source  102  (control line not shown) in order to achieve additional control of the image quality of the final projected image. 
         [0036]    Light recycling module  103  is depicted in  FIG. 1  as a dotted box that may be placed in the light path from the light source  102  to the first modulator  106 , as will be discussed below. While the present discussion will be given in the context of this positioning, it will be appreciated that light recycling may be inserted into the projector system at various points in the projector system. For example, light recycling may be placed between the first and second modulators. In addition, light recycling may be placed at more than one point in the optical path of the display system. While such embodiments may be more expensive due to an increase in the number of components, that increase may be balanced off against the energy cost savings as a result of multiple points of light recycling. 
         [0037]    While the embodiment of  FIG. 1  is presented in the context of a dual, multi-modulation projection system, it should be appreciated that the techniques and methods of the present application will find application in single modulation, or other dual, multi-modulation display systems. For example, a dual modulation display system comprising a backlight, a first modulator (e.g., LCD or the like), and a second modulator (e.g., LCD or the like) may employ suitable blurring optical components and image processing methods and techniques to affect the performance and efficiencies discussed herein in the context of the projection systems. 
         [0038]    It should also be appreciated that—even though  FIG. 1  depicts a two-stage or dual modulator display system—the methods and techniques of the present application may also find application in a display system with only one modulator or a display system with three or more modulator (multi-modulator) display systems. The scope of the present application encompasses these various alternative embodiments. 
       One Light Recycling Embodiment 
       [0039]      FIG. 2  depicts one embodiment of a light conduit subsystem and/or module  200 , as may be suitable for the purposes of the present application. As discussed above, this light conduit subsystem/module may be placed in the projector system primarily between the light source  102  and a first modulator  221 . Light from light source  102  may be input to the optical path via an integrating rod/tube/box  202 . In one embodiment, integrating rod/tube/box  202  may comprise a substantially reflected surface in its interior, so that light that is incident on its surface may be reflected (e.g., possibly multiple times) until the light exits its extreme right end  203 . Once the light exits the integrating rod/tube/box, the light may be placed into an optical path that is defined by a set of optical elements—e.g., lens  204 ,  214  and  216  and a set of filters and/or polarizers  206 ,  208 ,  210  and  212 . This embodiment may also be constructed to perform light recycling, if desired for the design of this projector system. 
         [0040]    First modulator  221  may comprise a number of prisms  218   a,    218   b  and a reflector  220 . Reflector  220  may comprise a DMD array of reflectors, or a MEMS array—or any other suitable set of reflectors possible that may reflect light in at least two or more paths. One such path is depicted in  FIG. 2 . As may be seen, reflectors  220  direct the light onto the interface of prisms  218   a  and  218   b,  such that the light is thereby reflected into lens assembly  222  and thereafter to second modulator  229  (e.g., comprising lens assembly  224 , prisms  226  and  230  and reflector  228 ). This light may be employed to form the finally projected image to be viewed by an audience. 
         [0041]    However, at certain time during the rendering of the final projected image, the full power/energy of the light source  102  may not be needed. If it is not possible to module the power of light source  102  (or if it is difficult or if there is additional opportunity to conserve light), then it may be desired to recycle the light from light source  102 . In this case, and as may be seen in  FIG. 2 , it may be possible to align reflector  220  from its current position as shown (i.e., where the light is directed to travel the path down to the second modulator—to position instead where the light would be substantially reflected back to the integrating rod/tube/box  202 , along substantially the same path as described as traveling from right-to-left direction. 
         [0042]    In another embodiment, a third (optional) path (not shown) allows the reflectors to direct light from the light source to a light “dump”—i.e., a portion of the projector system where the light is absorbed. In this case, the light is wasted as heat to be dissipated from the projector system. Thus, the projector system may have multiple degrees of freedom when it comes to directing the light as desired. 
         [0043]      FIG. 3  is yet another embodiment of a light conduit module  300 —which may serve to transmit light from at least one laser and/or partially coherent colored light source and ports (e.g., through fiber launch  302 , collimator  304 , diffuser  306 ). Light from such a source may transmit through a first optical subsystem/diffuser relay  308  to condition the light to be input into integrating rod  312 —which may comprise the reflecting proximal end  310  (e.g., recycling mirror), such as in  FIG. 3 . A second optical subsystem/recycling relay  314  may further condition the light as desired prior to input into a first modulator  316 . As with  FIG. 2  above, this first leg of the module  300  may affect a light recycling mode, as discussed. 
         [0044]    After first modulation, light may be transmitted through a third optical subsystem/PSF relay  318  prior to input into a second modulator  320 —which modulates the light for transmission through a projector optical subsystem  322  to project a final image for viewing. continued reference to  FIG. 3 , there is shown a relay optical system  318  that is placed in between a first modulator  316  (e.g., a pre-modulator) and a second modulator  320  (e.g., a primary modulator/nine piece prism). Such a relay optical system may be desirable to both reduce the amount of artifacts in the image processing—as well as increasing the contrast of the projected image. 
         [0045]    As discussed herein in the context of one embodiment, it may be desirable for the first modulator/pre-modulator to produce a blurred and/or de-focused image based upon image data values, such as the halftone image mentioned herein. In many embodiments, it may be desirable to have a relay optical system that tends to produce a uniformly blurred/de-focused image from the pre-modulator to the primary modulator. In addition, it may be desirable to have a desired, defocused spot shape for this embodiment. 
         [0046]    In many embodiments, the relay optical system may comprise lenses or other optical elements that effectively moves the focal plane, corrects for any coma, and adjusts the spread (e.g., by creating defocus/blur and adding spherical aberration to some desired amount). 
       Light Fiber Bundle Embodiments 
       [0047]      FIG. 4  depicts one embodiment ( 400 ) of an optical system comprising a set of discrete light fibers ( 402 ). In one embodiment, these multiple fibers may be spaced out—for example, to allow for manual assembly. This set of fibers feed light into relay optics (e.g.,  306 ) for input—e.g., into an integrating rod ( 312 ). The light may be from a set of lasers, partially coherent light and/or high powered lamps In one embodiment, for each light fiber, there may be a corresponding light source—e.g., a laser, an LED, a partially coherent light source, a high powered lamp or the like. In another embodiment, there may be one (or a less number than the number of light fibers) light sources that are supplying light to be transmitted by the bundle of light fibers. 
         [0048]    At the end of each such bundle, there may be a corresponding collimating lens  402   a.  Light from the collimating lenses may be input into a diffuser  404 . In one embodiment, diffuser  404  may be spinning and/or rotating to further reduce artifacts. In addition, spinning the diffuser may be desirable for thermal spreading/distribution reasons. In one embodiment, a spinning diffuser may create turbulent air that may then be evacuated from the housing through a convoluted route to reduce light leakage and dust ingress. Lens assembly  406  and  408  provide sufficient focus of the light into the mirrored element  410 . In another embodiment, there may be provide one (or a few number of than the number of light fibers) collimating lens(es) that through which the light from the light fibers enter into the diffuser. 
         [0049]    Mirrored element  410  may be at the proximal end of integrating rod  312 —and may be mirrored on the side facing the integrating rod in order to provide multiple traversals of light within the integrating rod—e.g., to help facilitate light recycling. As may be seen, there may be a plurality of holes  412   a,  which may be in one-to-one correspondence with the number of light fibers within the bundle. In another embodiment, there may be one (or a few—but less than the number of light fibers) hole(s)/aperture(s) in the mirrored element to allow the light from the bundle of fibers to enter the integrating rod. In embodiments that may not perform light recycling, it may be possible to use an element  410  that is not mirrored.  FIG. 5A  is a side view of the embodiment as shown in  FIG. 4 . 
         [0050]      FIG. 5B  is one exemplary ray tracing of light that may be focused by the lens assembly of  406 / 408  onto the mirrored element  410 . As may be seen, it may be desirable to design the lens assembly to focus the light from the diffuser onto the holes/apertures in such a manner as to minimize any light loss. 
       Improved Integrating Rod Embodiment 
       [0051]    As discussed above, light from the discrete light fibers may be focused onto holes and/or apertures into a integrating rod. In many embodiments, an improved, lengthened integrating rod may be employed by the projector display system. It may be desirable to increase the length of the integrating rods placed in the optical path of the projector system—e.g., to improve the uniformity of the image. To increase the length of the integrating rod, it may be possible to place and affix a plurality of conventional integrating rods together in a fashion that the performance of the final lengthened integrating rod performs well. 
         [0052]    As discussed further herein, such improved integrating rods may be oriented in a number of potential different orientations within a given projector system. Such different orientations may not be practical with standard, solid integration rods due to weak retention methods. Hollow rods might be used, but may not be practical due to power handling limitations and light reflection losses. Thus, many present embodiments may tend to combine the robust mounting option of a hollow rod with the efficiency of a solid rod. In some embodiments, straps may be solidly mechanically restrained without interfering with the light path. Such straps may also be applied to more standard integration rods but allow robust mounting. The straps may also reinforce the structural integrity of multiple rod assemblies which are butt joined to create longer integration length and/or which are joined length wise to combine multiple small integration rods. In some embodiments, the small cross sectional area rods may create more bounces down the length vs a single larger cross section integration rods. The bond line thickness and index of glue may be critical to not disturbing the Total Internal Reflectance (TIR) of the integration rod. In some embodiments, these improvements may not be limited to laser illumination alone, but the high f/# of a laser system may tend to ease the requirement for critical angle achieved by the bond line thickness and glue index. 
         [0053]      FIG. 6  depicts one embodiment of an improved integrating rod module  600  as made in accordance with the principles of the present application. Integrating rod  600  may comprise a plurality of smaller individual integrating rods—e.g.,  602   a  and  602   b —that are held together by one or more joining sections (aka “straps”)—e.g.,  604   a,    605   b  and  604   c.  It should be appreciated that the number of integrating rods may be more than two, as desired for the final design of the projector system. Integrating rod  600  may be employed in the various embodiments mentioned herein (e.g., at  312  in  FIG. 3, 202  in  FIG. 2 —or in other projector display systems, such as single modulation systems or multi-modulation systems). 
         [0054]      FIGS. 7A, 7B and 7C  depict various integrating rods and their construction. In  FIG. 7A , a single integrating rod  702  is shown being placed between two straps  704   a  and  704   b.  In  FIG. 7B , two single integrating rods  702   a  and  702   b  are shown being joined together by strap  704   a.  As these two integrating rods are in optical communication with each other, the interface  706  provides such optical communication, as is discussed further herein.  FIG. 7C  depicts yet another embodiment wherein a plurality of small cross-section rods (e.g.  708   a,    708   b,    708   c  and  708   d ) (e.g.  708   a  and  708   b ) are joined together to form a larger integrating rod  708 . Strap  710  is shown, providing mechanical stability and aiding optical communication between the various sections of the rods and at the interface  706 . Such interfaces may be glue bonded faces that create a substantially seamless bond. Alternatively, such interfaces may be accomplished through optical contacting. 
         [0055]    End views of the rod constructions are afforded as  710   a,    710   b  and  710   c.  In the case of end view  710   c,  it may be seen that the plurality of rods ( 708   a,    708   b,    708   c  and  708   d ) are shown and that  709  depicts the interfaces between the various rods. 
         [0056]    The improved integrating rods shown herein have a cumulative greater length than a single, conventional integrating rod. For example, lengthened integrating rods may have a variety of lengths—e.g., from 150 mm long to 450 mm long or longer, as desired. This may be desirable in order to provide an appropriate f-number for the optical system—e.g., to provide for a desired number of light bounces in the rod for good uniform illumination of the modulator distal to the integrating rod. For merely one example (and in reference to  FIG. 3 ), some exemplary f-numbers may be F/5 for the diffuser relay  308 , F/2.5 for the integrating rods  312 , F/3.8 for the primary modulator  316  and F/4/5 for the second modulator  320 . 
         [0057]    In some cases, the improved integrating rods constructed from mating/cementing together multiple rods (instead of making one long rod) may be desirable from the standpoint of ease of manufacturing and cost. In addition, using longer rods (however constructed) may be desirable when used for laser illumination because lasers allow a high f/#—which makes better contrast and transmission—and the longer rods may tend to achieve sufficient uniformity. 
         [0058]    During manufacturing, single longer rods may not fit in conventional vacuum chambers used to coat the end faces of the integration rods. This coating is required for throughput and recycling efficiency. Custom chambers could be made to handle the longer rods, but may use a larger capital investment at 3 rd  party supplier. Thus, manufacturing with multiple rods to make a longer rod, (e.g., limiting the rod size to standard sizes) may tend to allow the supplier to process the rods through normal methods for blocking, polishing, and coating. The additional combination step at the end tends to fit in with methods that are used to assemble prisms. 
       Additional Embodiments 
       [0059]    In the figures of  FIGS. 6, 7A-7C , there are shown straps that used to provide mechanical mating/bonding/attaching/communication/stability or the like for the improved, lengthened integrating rod as discussed. 
         [0060]    Straps may comprise material that are commonly known in the art—e.g. stainless steel, other metals or the like. In one embodiment, the straps may comprise glass and/or some other suitable material that may be a reasonable match of the thermal expansion property/behavior of the material comprising the integrating rod and/or portions thereof. For example, integrating rods may comprise glass or some other suitable transmissive/transparent material. In the context of a laser light (or some other high power light source) image projector system, the integrating rods may inhabit an environment of thermal extremes—and, as such, it may be desirable to have the straps comprising material (e.g., glass, fused silica, or the like) that may match the thermal expansions that the integrating rods may undergo. 
         [0061]      FIG. 8  depicts one embodiment of the mechanical mating ( 800 ) of a plurality of integrating rods ( 802   a,    802   b ). At the proximal end  804  of the first integrating rod, there may be an anti-reflective (AR) coating applied, as shown. At straps  806   a  and  806   b,  a glue may be applied substantially along the length of the strap/rod interface  808 . It may be desirable for this glue to be a mismatch of the index of refraction of the glass of the integrating rod (e.g., it may have a low index—as may be found in commercially available NOA133 adhesive, supplied by Norland Products, Inc.). This mismatch would tend not to disturb the total internal reflection supplied by the integrating rod. If there were such a disturbance, then light loss and other undesirable effects/errors may be introduced into the optical system. The low index adhesive changes the TIR angle relative to air, but with the high f/# of lasers, it tends to produce acceptable results. 
         [0062]    At strap  806   b,  it may be seen that two integrating rods are mated in place to maintain optical integrity. At the interface  810 , another (e.g., different) glue may be applied to aid in the mechanical integrity/stability of the optical system. In some embodiments, the glue may be selected to have a substantial match with the index of refraction with the material comprising the integrating rods.  FIG. 9  depicts that the mechanical mating at the straps ( 806 ) should not substantially disturb the critical angle ( 812 )—and allow the internal reflection to proceed without substantial loss. 
         [0063]      FIGS. 10A, 10B and 10C  gives a perspective view, a perspective cut-view and a front, cut-view of one embodiment of additional mechanical supports for the improved integrating rod 
         [0064]    As seen in these figures, integrating rods  1002   a  and  1002   b  may be mechanically mated by straps  1006 , as discussed herein. These straps and the integrating rods may be held further in place within the projector systems with a set of brackets/braces  1004 ,  1006  and  1008 —that may give further mechanical mating to the rest of the projector system. 
         [0065]    As a result of the improved mating of the integrating rods to straps (and, possibly, also straps to braces and brackets), the orientation of the integrating rod may be held at substantially different angles than horizontal. This may tend to give significant design options for constructing the projector systems. 
       Other Embodiments 
       [0066]    As mentioned above, gluing the integrating rods to the straps may tend to give good mechanical stability to the integrating rods and allow them to be placed within a number of different orientations. As also mentioned, it may be desirable to apply a glue with an index of refraction mismatch with the material comprising the integration rods. 
         [0067]    Another consideration for such bonding is the amount and/or thickness of this glue layer applied to the straps.  FIGS. 11, 12 and 13  give plots depicting the potential performance of the glue when applied in different thicknesses.  FIG. 11 , for example, purports to show the possible electric field intensity and various polarizations through the rod, the glue (e.g. NOA 133) layer and into the strap—for a layer of glue of thickness about 0.5 microns. As may be seen, the electric field may pass substantially through the glue at this level of thickness—which may not be desirable. 
         [0068]      FIGS. 12 and 13  depict the possible reflectance vs. angle performance for thicknesses of glue of about 1 micron and 10 microns, respectively. As may be seen, for about 1 micron, there may be a substantial amount of light less than the critical angle may be transmitted through the glue/adhesive. For about 10 microns, there may be areas of constructive and destructive interference that may be formed within the glue/adhesive layer. Overall, the thickness of the glue should be several multiples thicker than the wavelength of light being transmitted. 
         [0069]    A detailed description of one or more embodiments of the invention, read along with accompanying figures, that illustrate the principles of the invention has now been given. It is to be appreciated that the invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications and equivalents. Numerous specific details have been set forth in this description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured.