Patent Publication Number: US-2009219491-A1

Title: Method of combining multiple Gaussian beams for efficient uniform illumination of one-dimensional light modulators

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/999,622 filed Oct. 18, 2007, which is hereby incorporated by reference herein in its entirety, including but not limited to those portions that specifically appear hereinafter, this incorporation by reference being made with the following exception: In the event that any portion of the above-referenced provisional application is inconsistent with this application, this application supersedes said above-referenced provisional application. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND 
     1. The Field of the Invention. 
     The present disclosure relates generally to visual display devices, and more particularly, but not entirely, to illumination systems for use with display systems and other systems requiring illumination. 
     2. Description of Related Art 
     Display devices, such as televisions and image projectors, are increasingly using light modulators employing micro-electro-mechanical (“MEMS”) technology. MEMS-based light modulators are currently available in one-dimensional and two-dimensional varieties. Texas Instruments, for example, introduced a MEMS integrated circuit chip having a two-dimensional array formed from millions of tiny MEMS mirrors disposed on a substrate. Each mirror corresponds to a pixel in an image and electronic signals in the chip cause the mirrors to move and reflect light in different directions to form bright or dark pixels. See, for example, U.S. Pat. No. 4,710,732, which is hereby incorporated herein by this reference. One-dimensional light modulators, typically comprising a linear array of MEMS light modulating structures, may also be used to form a two-dimensional image through the use of appropriate magnifying optics and scanning mirrors. See for example, U.S. Pat. Nos. 5,982,553 and 7,054,051, which are hereby incorporated herein by this reference. 
     Both one-dimensional and two-dimensional light modulators require a light source to illuminate their light modulating surfaces. In order to accurately display an image using a two-dimensional light modulator, the intensity of the illumination provided by the light source should be uniform across its two-dimensional array of light modulating elements so that the generated pixels on a viewing surface are evenly illuminated. The illumination requirements for a one-dimensional light modulator may be slightly different from that of a two-dimensional light modulator. In particular, it has been found that the best images are formed on a viewing surface when the illumination of the light modulating elements of the one-dimensional light modulator is uniform along a first axis and non-uniform, such as Gaussian, along a second axis. 
     Halogen incandescent bulbs have been used in the past as light sources for at least two-dimensional light modulators. While halogen bulbs will produce a significant lumen output, they are known to be extremely inefficient in terms of converting electrical power to visible light. Further, due to their inherent inefficiency, halogen bulbs produce excessive heat, which requires the engineering of complex heat removal systems to prevent heat damage to surrounding components. Disadvantageously, halogen bulbs also have a relatively short life span and require frequent replacement. Halogen bulbs have, however, proven unsuitable for use with one-dimensional light modulators. 
     Coherent light sources, such as lasers, have been used in the past as light sources for illuminating one-dimensional light modulators. But, even coherent light sources also have their drawbacks. For example, achieving high amounts of lumen output from coherent light sources may require large and expensive amplification systems. Further, light beams emitted from coherent light sources typically have a non-uniform intensity distribution, such as a Gaussian distribution, that are generally unsuitable for use with light modulators. 
     In the past, one well-known method for converting a laser beam having a non-uniform distribution into a beam having a uniform, or top-hat distribution, was accomplished by employing a special type of lens, known as a Powell lens. In fact, Powell lenses are widely known to produce an efficient line pattern that overcomes the limits of Gaussian patterns. 
     Recent advances in the development of diode lasers have attempted to address the need for expensive amplifiers with coherent light sources. However, while more energy efficient, an individual diode laser does not have sufficient output for use with most image projection systems. To overcome this drawback, multiple diode lasers may be grouped together into an array. However, because of the spatial distribution inherent with diode-laser arrays, it is not always possible to use a single Powell lens in order to convert the Gaussian distributions of the beams emitted from a diode-laser array into a uniform, or top-hat, distribution. Another drawback to the use of a diode-laser array is that the differences in the output of each of the diode lasers may cause irregularities in the intensity of the spatial distribution. 
     One previous attempt to transform a non-uniform intensity distribution of a beam emitted from a laser into a beam with a uniform intensity distribution is disclosed in U.S. Pat. No. 4,744,615 (granted May 17, 1988 to Fan et al.). Fan et al. discloses directing a coherent laser beam having a non-uniform spatial intensity distribution into a light tunnel to thereby produce a beam having a substantially uniform spatial intensity distribution. The light tunnel of the Fan et al. device includes a polygonal cross-section such that the image produced at the exit of the light tunnel will have a substantially uniform intensity distribution in two-dimensions. While the Fan et al. device is suitable for its intended purpose of illuminating a mask for the fabrication of microcircuits as disclosed therein; it is not suitable for illuminating a one-dimensional light modulator. In particular, the Fan et al. device cannot generate a line image with a substantially uniform distribution along a first axis and a non-uniform distribution along a second axis, as is necessary for the most effective use of one-dimensional light modulators. 
     Thus, there exists a need for an optical system that is able to efficiently convert the non-uniform distribution of laser beams generated by a diode-laser array into a uniform distribution along a first axis and a non-uniform distribution along a second axis, especially when such diode-laser arrays are used to illuminate one-dimensional light modulators. The features and advantages of this disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the disclosure without undue experimentation. The features and advantages of the disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and upon payment of the necessary fee. 
       The features and advantages of the disclosure will become apparent from a consideration of the subsequent detailed description presented in connection with the accompanying drawings in which: 
         FIG. 1  is a diagram illustrating an optical system pursuant to an embodiment of the present disclosure; 
         FIG. 2  is a top view of a light modulation device illuminated with a line image produced by the optical system shown in  FIG. 1 ; 
         FIG. 3  depicts a spatial intensity distribution in both the Y-axis and the X-axis of the line image produced by the optical system shown in  FIG. 1 ; 
         FIG. 4  depicts a display system pursuant to an embodiment of the present invention; and 
         FIGS. 5A-5C  depict a perspective view, a top view, and an end view, respectively, of a light tunnel. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles in accordance with the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications of the inventive features illustrated herein, and any additional applications of the principles of the disclosure as illustrated herein, which would normally occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the disclosure claimed. 
     It must be noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Further, as used herein, the terms “comprising,” “including,” “containing,” “having,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps. 
     Applicants have discovered an illumination system for transforming an image generated by an array of coherent light sources with a non-uniform intensity distribution into an image having a uniform distribution, or top-hat distribution, along a first axis, and a non-uniform intensity distribution along a second axis. The present disclosure may be particularly adapted for use with one-dimensional light modulators that require a line image of light with a uniform intensity distribution over the long dimension of the array of light modulating elements on the light modulator. 
     The present disclosure may further preserve a Gaussian intensity distribution in an axis orthogonal to the long dimension of the one-dimensional array of light modulating elements on the light modulator. It will be appreciated by those having ordinary skill in the art that the preservation of the non-uniform, or Gaussian, intensity distribution along this orthogonal axis helps to achieve narrower line widths (i.e., improved image resolution in the orthogonal direction) since Gaussian beams focus to smaller spot sizes as compared to the spot sizes achieved with uniform-intensity beams. The present disclosure is further unique in that it may be aligned to maintain the polarization state of the original laser beams. 
     Referring now to  FIG. 1 , there is depicted an optical system, generally designated at  10 , according to an embodiment of the present disclosure. The optical system  10  includes an array of light sources  100  that generate coherent beams of light  101 . In an embodiment of the present disclosure, each of the light sources  100  is a semiconductor laser having an array of high-power surface emitting diode lasers disposed on a chip. It will be noted that the colors represented in  FIG. 1  are not intended to represent any particular wavelength of beams of light  101 , in fact the wavelengths of the beams of light  101  may all be the same (as explained below), but the colors represented in  FIG. 1  are intended to clarify the function of the exemplary embodiment of the present disclosure. 
     Each of the light sources  100  may emit a light beam  101  that is the same wavelength as the light beams  101  emitted by the other light sources  100 . That is, the light beams  101  may all be of the same color, such as red, green or blue. It will be appreciated that the light sources  100  may be grouped into an array to generate the necessary output suitable for use with the optical system  10 . Each of the beams  101  may be generated from an array of diode emitters or just a single emitter. 
     Novalux, Inc. currently manufactures diode laser platforms suitable for use with the present disclosure. However, the present disclosure may be used with single laser beams such as those taught in U.S. Pat. No. 6,763,042, which is hereby incorporated by reference in its entirety. It should be further noted that the present disclosure may include only one of the light sources  100  and beams  101 . 
     As mentioned, each of the beams  101  may be generated from one of the light sources  100 . The beams  101  may each have a divergence a, which is not explicitly shown in  FIG. 1 , when emitted from their respective light sources  100 . Each of the beams  101  may initially have a non-uniform intensity distribution. The non-uniform distribution of each of the beams  101  may consist of a circular Gaussian distribution. 
     In an embodiment of the present disclosure, reflective mirrors (not explicitly shown) may reduce the spatial distances and angular separations between the beams  101  emitted from the light sources  100 . These mirrors may be operable to direct the beams  101  into a set of injector optics  102 . It will be noted that the multiple beams  101  together form an apparent object with a height of H just prior to entering the set of injector optics  102 . Furthermore, because the beams  101  are lasers, they may have a relatively small divergence a (typically, 0&lt;α&lt;0.01 radians, although much greater values of a are permissible). 
     The set of injector optics  102  may comprise lenses  102 A,  102 B,  102 C and  102 D. It will be appreciated that the overall purpose of the injector optics  102  may be to reduce the size of the object of height H formed by the beams  101  to a new image having a lesser height of h. Furthermore, the injector optics  102  may increase the divergence of the beams  101  from α to α′, which is also not explicitly shown in  FIG. 1 , prior to the beams  101  entering a light tunnel  103 , with α′ increasing in direct proportion to the decrease in size from H to h. 
     In an embodiment of the present disclosure, the injector optics  102  may reduce the image size of the beams  101  between about 5 and about 50 times. In an embodiment of the present disclosure, the injector optics  102  may reduce the image size of the beams  101  between about 18 and about 22 times. In an embodiment of the present disclosure, the injector optics  102  may reduce the image size of the beams  101  approximately by about 20 times. That is, 
     
       
         
           
             
               H 
               h 
             
             ≅ 
             20 
           
         
       
     
     The injector optics  102  may be collectively referred herein as an “optical reducer” since the injector optics  102  are operable to reduce the size of the apparent object of the beams  101 . 
     At the same time the object height H is reduced to an image height h, the injector optics  102  increase the divergence α of the beams  101  to divergence α′. In an embodiment of the present disclosure, the divergence is increased between about 5 and about 50 times. In an embodiment of the present disclosure, the divergence is increased between about 18 and about 22 times. In another embodiment of the present disclosure, the divergence is increased between about 5 times to about 30 times. In yet another embodiment of the present disclosure, the divergence is increased about 20 times. That is, 
       α=20×α 
     Turning now to the optics  102 A,  102 B,  102 C, and  102 D, each will now be described pursuant to an embodiment of the present disclosure. Optic  102 A may comprise a spherical or cylindrical optic having a clear aperture such that it can transmit all of the light from an object of height H. Optic  102 B may comprise a spherical or cylindrical optic having a clear aperture such that it can transmit all of the light transmitted by optic  102 A. Optic  102 C may comprise a spherical or cylindrical optic having a clear aperture such that it can transmit all of the light transmitted through optics  102 A and  102 B. Optics  102 A,  102 B, and  102 C may cause the beams  101  of apparent object size H to be collimated such that the chief rays of each of the beams  101  passes through a common focal point. In an embodiment of the present disclosure, the beams  101  are also collimated such that a common pupil is formed in the focal plane of the system consisting of optics  102 A,  102 B, and  102 C. 
     In an embodiment of the present disclosure, the optic  102 D may comprise a spherical or cylindrical optic having a different focal length than optics  102 A,  102 B, and  102 C. The focal point of optic  102 D may be placed at approximately the same position of the focal point of the system consisting of optics  102 A,  102 B, and  102 C, wherein a reduction in size of the apparent object of height H formed by the beams  101  is reduced to an image having a height of h upon exiting the injector optics  102 . The optic  102 D now finishes the injection of the light beams  101  into the light tunnel  103 . It will be appreciated by one having ordinary skill in the art that the divergence of the beams  101  in the system will increase by the same factor with which the height of the object is reduced as determined by the equation H/h. 
     The light tunnel  103  may comprise two opposing sides having walls  103 A and  103 B, respectively, and extend along a Z-axis. The walls  103 A and  103 B may be substantially parallel to each other and include a reflective coating on their inner surfaces. The walls  103 A and  103 B may be orthogonal to a Y-axis and parallel to an X-axis. The light tunnel  103  may have a hollow interior passageway with a light entrance at one end and a light exit at the other end. The walls  103 A and  103 B may extend from the light entrance to the light exit. In addition, the remaining two sides of the light tunnel  103 , the sides orthogonal to the X-axis and parallel to the Y-axis, may be left open or constructed from a material that will not interact with light, such as clear glass or a material with a light absorbing capability. 
     The light tunnel  103  operates to convert the non-uniform distribution of the beams  101  into a beam with a uniform distribution along a Y-axis and a non-uniform distribution along an X-axis. This may be accomplished as the beams  101  are repeatedly reflected between the inner surfaces of the walls  103 A and  103 B. It will be appreciated by those having ordinary skill in the art that the greater the increase in divergence of the beams  101  as caused by the injector optics  102 , the more numerous such multiple internal reflections are for a given propagation distance within the light tunnel  103 . Further, without the increased divergence imparted to the beams  101  by the optics  102 , or, without substantially increasing the length of the light tunnel  103 , the light tunnel  103  would be less effective in converting the non-uniform distribution to a uniform distribution along the Y-axis of the beams  101 . 
     Furthermore, the Gaussian profile of the beams  101  along their X-axis, which is orthogonal to the Y-axis, remains substantially unchanged by the light tunnel  103  due to the fact that the light tunnel  103  is constructed such that its width in the direction of the X-axis is always greater than that of the Gaussian distribution of the beams  101 , so that the corresponding sides of the light tunnel  103  never interact with the beams  101  in the X-axis. For this reason, the sides of the light tunnel  103  adjacent the sides  103 A and  103 B may be left open or constructed from a material that does not interact with light, such as glass or a light absorbing material. In an embodiment of the present disclosure, sides parallel to the Y-axis are present on the light tunnel  103 , but they do not interact meaningfully with the beams  101 . 
     Referring now to  FIGS. 5A-5C , there is depicted a more detailed view of the light tunnel  103  suitable for use with the system  10  depicted in  FIG. 1 . As previously discussed, the light tunnel  103  comprises opposing walls  103 A and  103 B extending from a light entrance  103 C to a light exit  103 D. As further previously described, the internal surfaces of the walls  103 A and  103 D may be reflective and form the sides of a light passageway through the light tunnel  103 . Disposed between each of the walls  103 A and  103 B may be walls  103 E and  103 F. Walls  103 E and  103 F may be spaced apart to thereby form sides of the light passageway through the light tunnel  103 . However, the internal surfaces of the walls  103 E and  103 F may not interact with light passing through the internal passageway of the light tunnel  103 . In this regard, the walls  103 E and  103 F may be formed from glass, a light absorbing material, or any other material that will not cause or reduce internal reflections from the walls  103 E and  103 F. 
     In an embodiment of the present disclosure, the walls  103 E and  103 F may be omitted entirely and the sides of the internal passageway may be left open. It will be appreciated however, that even though the walls  103 E and  103 F do not interact with light passing through the light tunnel  103 , that it is convenient to use walls  103 E and  103 F to maintain the proper spacing between, and to support the walls  103 A and  103 B. 
     Still referring to  FIGS. 5A-5C , in another embodiment of the present disclosure, the internal passageway in the light tunnel  103  has a height, indicated by the reference numeral  150 , of about 2.8 mm, a width, indicated by the reference numeral  152 , sufficient such that there is no reflection from the beams in the X-axis (such as about between about 14 mm and about 20 mm, or greater), and a length, indicated with the reference numeral  154 , of about 100 mm. It will be understood that the length of the walls  103 A and  103 B of the light tunnel  103  is relatively short because of the “fast” divergence of the beams  101  created by the injector optics  102  (see  FIG. 1 ). 
     Referring now to FIGS.  1  and  5 A- 5 C, in order to cause a relatively uniform image in the Y-axis suitable for use with a one-dimensional light modulator, each beam  101  may need to be internally reflected between the walls  103 A and  103 B (in the Y-axis) at least five (5) times in the light tunnel  103 . More than five (5) reflections inside of the light tunnel  103  is typically not required to achieve a uniform distribution, i.e., the distribution is completely uniform within five (5) reflections as the beams  101  propagate through the tunnel  103 . Increasing the divergence will cause the beams  101  to reflect more often, thereby causing the length of the light tunnel  103  needed to achieve a uniform distribution to be relatively short. If the divergence of the beams  101  were smaller or “slower,” the length of the light tunnel  103  would need to be increased. As mentioned, the light tunnel  103  need not have sides to reflect a beam in the X-axis and, therefore, the light tunnel  103  may consist of just two parallel mirrors. 
     It will be appreciated that other light-mixing devices can also be utilized with the present disclosure. For example, a light rod constructed of a transmissive material such as glass or plastic with similar dimensions may also be utilized. Thus, it will be appreciated that any light-mixing device operable to generate a uniform distribution from a non-uniform beam, such as a beam with a Gaussian distribution, falls within the scope of the present disclosure. 
     With sufficient length of the light tunnel  103  for a given divergence α′ of the beams  101 , the output of the light tunnel will be uniform in intensity along an axis (hereafter referred to as the “Y-axis”) that is normal to both of the internal reflective surfaces of walls  103 A and  103 B. Thus, any faithful image of the output of the light tunnel  103  will also exhibit a uniform intensity distribution along this same Y-axis. 
     The light from each individual beam of beams  101  will be uniformly distributed along the Y-axis at the output of the light tunnel  103 , so that any image of this output will cause light from each individual beam to be uniformly distributed over the entire image. Consequently, it is convenient to treat the output plane of the light tunnel  103  as an object O for the remaining optics  104  of the illumination system. 
     Referring now primarily to just  FIG. 1 , imaging optics, designated by the bracket  104 , cause the apparent object O formed by the output plane of the light tunnel  103  to be magnified and telecentrically re-imaged along a surface  105  to form an image O′. In particular, imaging optics  104  image the object O having a height of approximately 2.8 mm in the Y-axis onto the surface  105  such that an image O′ is formed with a new height of approximately 31 mm (approximately the length of an active area of a light modulator). As mentioned, the new image O′ formed from the object O by the imaging optics  104  is a telecentric image. 
     Along the axis perpendicular to the Y-axis (hereafter referred to as the “X-axis”), the imaging optics  104  cause an image P, not explicitly shown in  FIG. 1 , to be focused into an image P′ at the surface  105  such that image P′ is contained in the same plane as image O′. Image P, however, is not co-located with the object O. Image P is located at the focal point of optic  102 D where object O is located at end of the light tunnel  103 . 
     Furthermore, it should be noted that, as drawn in  FIG. 1 , cylindrical optics may be used to form an image of O at O′ in the Y-axis, and that cylindrical optics may be used to form an image of the beam waists in the X-axis at O′ Thus, at O′, in the Y-axis there is an image of the output of the light tunnel  103  and in the X-axis there is an image of the beam waists. In other words, the optical system may be “anamorphic” wherein the focus in one axis may be different or nonexistent in the other axis. 
     Still referring primarily to  FIG. 1 , each of the individual components of the imaging optics  104  will now be described. Optic  104 A may comprise a spherical or cylindrical lens for receiving the object O from the output end of light tunnel  103 . Optics  104 B and  104 C work in conjunction with the rest of the optics in imaging optics  104  in order to re-image two different planes onto the same image surface  105 . The line marked with the reference numeral  104 D represents a pupil formed by the previous optics. Optics  104 E and  104 F are spherical or cylindrical optics that continue to work with the rest of the optics in the imaging optics  104  to form a telecentric magnified image of O, that is, O′ on the surface  105 . The surface  105  may be disposed on, and be part of, a light-modulating device. 
     Referring now to  FIG. 2 , there is depicted a light-modulating device  200  suitable for use in conjunction with the system  10 . The light-modulation device  200  may be a one-dimensional light modulator having a one-dimensional array  202  of light modulation elements arranged in a column along the Y-axis. In particular, the array  202  may comprise a plurality of reflective and deformable ribbons  204  suspended over a substrate  206  and extending in the direction of the X-axis. These ribbons  204  are arranged in a column of parallel rows and may be deflected, i.e., pulled down, by applying a bias voltage between the ribbons  204  and the substrate  206 . 
     In an embodiment of the present disclosure, the light modulation device  200  may modulate light via diffraction. In particular, a first group of the ribbons  204  may comprise alternate rows of the ribbons. The ribbons  204  of the first group may be collectively driven by a single digital-to-analog controller (“DAC”) such that a common bias voltage may be applied to each of them at the same time. For this reason, the ribbons  204 A of the first group are sometimes referred to as “bias ribbons.” A second group of ribbons  204  may comprise those alternate rows of ribbons  204  that are not part of the first group. Each of the ribbons  204 B of the second group may be individually addressable or controllable by its own dedicated DAC device such that a variable bias voltage may be independently applied to each of them. For this reason, the ribbons  204  of the second group are sometimes referred to as “active ribbons.” 
     The bias and active ribbons may be sub-divided into separately controllable picture elements referred to herein as “pixel elements.” Each pixel element contains, at a minimum, a bias ribbon and an active ribbon. When the reflective surfaces of the bias and active ribbons of a pixel element are co-planar, incident light directed onto the pixel element is reflected. By blocking the reflected light from a pixel element, a dark spot is produced on the viewing surface at a corresponding display pixel. When the reflective surfaces of the bias and active ribbons of a pixel element are not co-planar, incident light may be both diffracted and reflected off of the pixel element. By separating the diffracted light from the reflected light, the diffracted light produces a bright spot on the corresponding display pixel. 
     The intensity of the light produced on the viewing surface by a given pixel element may be controlled by varying the separation between the reflective surfaces of its active and bias ribbons. Typically, this is accomplished by varying the voltage applied to the active ribbon while holding the bias ribbon at a common bias voltage. It has been previously determined that the maximum light intensity output for a pixel element may occur in a diffraction based system when the distance between the reflective surfaces its active and bias ribbons is λ/4, where λ is the wavelength of the light incident on the pixel element. The minimum light intensity output for a pixel element may occur when the reflective surfaces of its active and bias ribbons are co-planar. Intermediate light intensities may be output from the pixel element by varying the separation between the reflective surfaces of the active and bias ribbons between co-planar and λ/4. 
     It will be appreciated that although a limited number of ribbons  204  are depicted for the light modulation device  200  for purposes of convenience and clarity, that the light modulation device  200  may include a column of several hundred or thousand ribbons  204  extending along the Y-axis. In this manner, the ribbons  204  may form several hundred or thousand pixel elements. It will be further appreciated that the light modulation device  200  is best suited for display systems that employ a line-scan architecture. Display systems that employ a line-scan architecture typically scan an entire column, or row, of pixels across a viewing surface using a single scanning mirror. 
     Still referring to  FIG. 2 , in an embodiment of the present disclosure, the light modulation device  200  may modulate light using polarization in lieu of diffraction. In particular, the ribbons  204  may be operable to vary path lengths traveled by beams of light to thereby impart a phase shift between two beams of light when they are recombined. A polarization-based light modulator and system suitable for use with the present disclosure is described in U.S. Provisional Patent Application Nos. 61/095,917; 61/097,364; and 61/093,187; which are hereby incorporated by reference in their entireties. It will be further appreciated that the light modulation device  200  may include other MEMS elements, including cantilevers and the like, without departing from the scope of the present disclosure. 
     Still primarily referring to  FIG. 2 , a line image  208  may be formed on the ribbons  204  by the system  10  depicted in  FIG. 1 . The line image  208  formed by the system  10  may extend along the Y-axis such that a portion of each of the ribbons  204  is evenly illuminated. In particular, as shown in  FIG. 3 , a graph representing a spatial intensity distribution  210  along the Y-axis of the line image  208  is depicted as well as a graph representing a spatial intensity distribution  212  along the X-axis of the line image  208 . As may be observed, the spatial intensity distribution  210  of the line image  208  along the Y-axis comprises a uniform intensity. In this manner each of the ribbons  204  (see  FIG. 2 ) is evenly illuminated. As may be further observed, the spatial intensity distribution  212  of the line image  208  along the X-axis comprises a non-uniform distribution. In an embodiment of the present disclosure, the spatial intensity distribution  212  of the line image  208  along the X-axis comprises a Gaussian distribution. As previously discussed, the use of a non-uniform distribution along the X-axis allows a line image formed from light modulated by the light modulation device  200  to be more precisely focused in the X-direction. 
     The optical system  10  shown in  FIG. 1  and the light modulation device  200  shown in  FIG. 2  may be part of a display system  300  as shown in  FIG. 4 . An optical assembly may direct beams of light, indicated by the dashed lines, from the plurality of light sources  100  into the optical system  10 . A line image, such as the line image  208  shown in  FIGS. 2 and 3 , exiting the system  10  is directed onto the light modulation device  200 . The line image may include a uniform distribution along a first axis and a non-uniform distribution along a second axis. A modulated line image is directed from the light modulation device  200  to a scanning mirror  302  and a projection lens  304  such that the display system  300  may employ a line-scan architecture for scanning an image onto a viewing surface  306 . 
     It will be appreciated that the use of a light tunnel, with two open or non-light interactive sides, as described herein, e.g., light tunnel  103  represented in FIGS.  1  and  5 A- 5 C, also provides another benefit relating to the polarization of the light. In particular, the use of a four-sided light tunnel, i.e., a tunnel whose four-side walls all interact with a light beam, fails to maintain the polarization of the light passing through it. For example, when a light tunnel with four (4) reflective sides is used by a LCOS-based projector, additional optical devices are utilized in an attempt to restore the linear polarization lost through the use of the four-sided light tunnel. Thus, an unexpected result to the use of a light tunnel with only two light reflective sides as described herein is that it may maintain the linear polarization of the incoming light beams. 
     Those having ordinary skill in the relevant art will appreciate the advantages provided by the features of the present disclosure. For example, it is a feature of the present disclosure to provide a system for converting the non-uniform distribution from a plurality of laser beams into a uniform distribution along a first axis of each of the laser beams and a non-uniform distribution along a second axis of the laser beams. Another feature of the present disclosure is a display system that is able to utilize multiple semiconductor lasers as a light source for a one-dimensional light modulator, such that light from each laser will uniformly illuminate an array of light modulating structures. 
     In the foregoing Detailed Description, various features of the present disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby incorporated into this Detailed Description by this reference, with each claim standing on its own as a separate embodiment of the present disclosure. 
     It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present disclosure. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present disclosure and the appended claims are intended to cover such modifications and arrangements. Thus, while the present disclosure has been shown in the drawings and described above with particularity and detail, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein.