Abstract:
The disclosure generally relates to color combiners, and in particular color combiners useful in small size format projectors such as pocket projectors. The disclosed color combiners include a tilted dichroic plate having at least two reflectors configured with light collection optics to combine at least two colors of light.

Description:
RELATED APPLICATIONS 
       [0001]    This application is related to the following U.S. patent applications, which are incorporated by reference: “Tilted Dichroic Color Combiner I” (Attorney Docket No. 66530US002) and “Tilted Dichroic Color Combiner III” (Attorney Docket No. 66792US002), both filed on an even date herewith. 
     
    
     BACKGROUND 
       [0002]    Projection systems used for projecting an image on a screen can use multiple color light sources, such as light emitting diodes (LED&#39;s), with different colors to generate the illumination light. Several optical elements are disposed between the LED&#39;s and the image display unit to combine and transfer the light from the LED&#39;s to the image display unit. The image display unit can use various methods to impose an image on the light. For example, the image display unit may use polarization, as with transmissive or reflective liquid crystal displays. 
         [0003]    Still other projection systems used for projecting an image on a screen can use white light configured to imagewise reflect from a digital micro-mirror (DMM) array, such as the array used in Texas Instruments&#39; Digital Light Processor (DLP®) displays. In the DLP® display, individual mirrors within the digital micro-mirror array represent individual pixels of the projected image. A display pixel is illuminated when the corresponding mirror is tilted so that incident light is directed into the projected optical path. A rotating color wheel placed within the optical path is timed to the reflection of light from the digital micro-mirror array, so that the reflected white light is filtered to project the color corresponding to the pixel. The digital micro-mirror array is then switched to the next desired pixel color, and the process is continued at such a rapid rate that the entire projected display appears to be continuously illuminated. The digital micro-mirror projection system requires fewer pixelated array components, which can result in a smaller size projector. 
         [0004]    Image brightness is an important parameter of a projection system. The brightness of color light sources and the efficiencies of collecting, combining, homogenizing and delivering the light to the image display unit all affect brightness. As the size of modern projector systems decreases, there is a need to maintain an adequate level of output brightness while at the same time keeping heat produced by the color light sources at a low level that can be dissipated in a small projector system. There is a need for a light combining system that combines multiple color lights with increased efficiency to provide a light output with an adequate level of brightness without excessive power consumption by light sources. 
         [0005]    Such electronic projectors often include a device for optically homogenizing a beam of light in order to improve brightness and color uniformity for light projected on a screen. Two common devices are an integrating tunnel and a fly&#39;s eye array (FEA) homogenizer. Fly&#39;s eye homogenizers can be very compact, and for this reason is a commonly used device. Integrating tunnels can be more efficient at homogenization, but a hollow tunnel generally requires a length that is often 5 times the height or width, whichever is greater. Solid tunnels often are longer than hollow tunnels, due to the effects of refraction. 
         [0006]    Pico and pocket projectors have limited available space for efficient color combiners, light integrators, and/or homogenizers. As a result, efficient and uniform light output from the optical devices used in these projectors (such as color combiners and polarization converters) can require compact and efficient optical designs. 
       SUMMARY 
       [0007]    The disclosure generally relates to color combiners, and in particular color combiners useful in small size format projectors such as pocket projectors. The disclosed color combiners include a tilted dichroic plate having at least two reflectors configured with light collection optics to combine at least two colors of light. In one aspect, the present disclosure provides a color combiner that includes a first light collection optics having a light input surface and an optical axis; a first and a second light source disposed to inject a first and a second color light into the light input surface; and a dichroic plate disposed facing the first light collection optics opposite the light input surface and disposed at a tilt angle to the optical axis. At least one of the first and second light sources are displaced from the optical axis. The dichroic plate includes: a first dichroic reflector capable of reflecting the first color light and transmitting other color light; and a second reflector capable of reflecting the second color light, wherein the first dichroic reflector and the second reflector are each tilted such that the first and the second color light are both reflected in an output direction, the first and the second color light forming a combined color light beam. 
         [0008]    In another aspect, the present disclosure provides a color combiner that includes a first lens having a first convex surface, a light input surface opposite the first convex surface, and an optical axis. The color combiner further includes a second lens centered on the optical axis, the second lens having a second surface facing the first convex surface, and a third convex surface opposite the second surface. The color combiner still further includes a first, a second, and a third light source, at least two of the first, the second, and the third light source displaced from the optical axis and disposed to inject a first, a second, and a third color light into the light input surface; and a dichroic plate disposed facing the third convex surface and at a tilt angle to the optical axis. The dichroic plate includes a first dichroic reflector capable of reflecting the first color light and transmitting the second and the third color light; a second dichroic reflector capable of reflecting the second color light and transmitting the third color light; and a third reflector capable of reflecting the third color light. The first dichroic reflector, the second dichroic reflector, and the third reflector are each tilted such that the first, the second, and the third color light are each reflected in an output direction, the first, the second, and the third color light forming a combined color light beam. 
         [0009]    In yet another aspect, the present disclosure provides an image projector that includes a color combiner. The color combiner includes a first light collection optics having a light input surface and an optical axis; a first and a second light source disposed to inject a first and a second color light into the light input surface; and a dichroic plate disposed facing the first light collection optics opposite the light input surface and disposed at a tilt angle to the optical axis. At least one of the first and second light sources are displaced from the optical axis. The dichroic plate includes: a first dichroic reflector capable of reflecting the first color light and transmitting other color light; and a second reflector capable of reflecting the second color light, wherein the first dichroic reflector and the second reflector are each tilted such that the first and the second color light are both reflected in an output direction, the first and the second color light forming a combined color light beam. The image projector further includes a polarization converter disposed to accept the first, the second, and the third color light and output a polarized first, second, and third color light; a spatial light modulator disposed to impart an image to the polarized first, second, and third color light; and projection optics. 
         [0010]    In yet another aspect, the present disclosure provides an image projector that includes a color combiner. The color combiner includes a first lens having a first convex surface, a light input surface opposite the first convex surface, and an optical axis. The color combiner further includes a second lens centered on the optical axis, the second lens having a second surface facing the first convex surface, and a third convex surface opposite the second surface. The color combiner still further includes a first, a second, and a third light source, at least two of the first, the second, and the third light source displaced from the optical axis and disposed to inject a first, a second, and a third color light into the light input surface; and a dichroic plate disposed facing the third convex surface and at a tilt angle to the optical axis. The dichroic plate includes a first dichroic reflector capable of reflecting the first color light and transmitting the second and the third color light; a second dichroic reflector capable of reflecting the second color light and transmitting the third color light; and a third reflector capable of reflecting the third color light. The first dichroic reflector, the second dichroic reflector, and the third reflector are each tilted such that the first, the second, and the third color light are each reflected in an output direction, the first, the second, and the third color light forming a combined color light beam. The image projector further includes a polarization converter disposed to accept the first, the second, and the third color light and output a polarized first, second, and third color light; a spatial light modulator disposed to impart an image to the polarized first, second, and third color light; and projection optics. 
         [0011]    The above summary is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The figures and the detailed description below more particularly exemplify illustrative embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Throughout the specification reference is made to the appended drawings, where like reference numerals designate like elements, and wherein: 
           [0013]      FIG. 1A  shows a cross-section schematic of a color combiner; 
           [0014]      FIG. 1B  shows a cross-section schematic of a color combiner; 
           [0015]      FIG. 1C  shows a cross-section schematic of a color combiner; 
           [0016]      FIG. 2  shows a cross-section schematic appended to section A-A′ of  FIGS. 1A-1C ; and 
           [0017]      FIG. 3  shows a schematic diagram of an image projector. 
       
    
    
       [0018]    The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number. 
       DETAILED DESCRIPTION 
       [0019]    This disclosure generally relates to image projectors, in particular image projectors having an improved uniformity of light by combining the light using a tilted dichroic reflector plate. In one particular embodiment, the tilted dichroic reflector plate includes a plurality of dichroic filters laminated together, wherein each of the dichroic filters can be tilted at an angle to a normal to the dichroic reflector plate. 
         [0020]    In one particular embodiment, a color combiner is described that includes at least two light emitting diodes (LEDs), each with a different color. The light emitted from the two LEDs is collimated into beams that substantially overlap, and the light from the two LEDs is combined and directed into a common area with the combined light beams having a lower etendue and higher brightness than the light emitted by the two LEDs. 
         [0021]    The LEDs may be used to illuminate projectors. Since LEDs emit light over an area with a near Lambertian angular distribution, the brightness of a projector is limited by the etendue of the source and the projection system. One method for reducing the etendue of the LED light source is to use dichroic reflectors to make two or more colors of LEDs spatially overlap, such that they appear to be emitting from the same region. Ordinarily, color combiners use the dichroic reflectors at an angle of about 45 degrees. This causes a strong reflective band shift, and limits the useful spectra and angular range of the dichroic reflector. In one particular embodiment, the present disclosure describes an article that combines different color LEDs using dichroic reflectors that are at near normal angles to the incident light beam. 
         [0022]    In one aspect, the disclosure provides a compact method of efficiently combining the output from different color light sources. This can be particularly useful for producing illuminators for compact projection systems that are etendue limited. For example, a linear array of red, green, and blue LEDs, where the output of each LEDs is partially collimated by a set of primary optics, is incident on a tilted reflector plate assembly that contains dichroic reflector plates that reflect the red, green, and blue light at different angles. The reflected light is then output as a collimated combined color light beam. 
         [0023]    The configuration of the 3 LEDs can be expanded to other colors, including yellow and infrared light, as understood by one of skill in the art. The LEDs can be arranged in various patterns, including linear arrays and triangular arrays. The light sources may include lasers combined with LEDs, and may be also be based on an all laser system. The LEDs may consist of a set emitting at least primary colors on short wavelength range of red, green, and blue, and a second set emitting the primary colors on the long wavelength range of red, green, and blue. Further, the aperture at which point the light is mixed may incorporate a Fly Eye Array (FEA) to provide further color integration. This may consist of a one or two dimensional array of lenses, with at least one dimension having 2 to about 20 lenses, as described elsewhere. 
         [0024]    LCoS-based portable projection systems are becoming common due to the availability of low cost and high resolution LCoS panels. A list of elements in an LED-illuminated LCoS projector may include LED light source or sources, optional color combiner, optional pre-polarizing system, relay optics, PBS, LCoS panel, and projection lens unit. For LCoS-based projection systems, the efficiency and contrast of the projector is directly linked to the degree of polarization of light entering the PBS. For at least this reason, a pre-polarizing system that either utilizes a reflection/recycling optic or a polarization-conversion optical element, is often required. 
         [0025]    Polarization conversion schemes utilizing polarizing beam splitters and half-wave retarders are one of the most efficient ways to provide polarized light into the PBS. One challenge with polarization-converted light is that it may suffer from spatial nonuniformity, leading to artifacts in the displayed image. Therefore, in systems with polarization converters, a homogenization system can be desirable, as described elsewhere. 
         [0026]    In one particular embodiment, an illuminator for an image projector includes a light source in which emitted unpolarized light is directed into a polarization converter. The polarization converter separates the light into two paths, one for each polarization state. The path length for each of the two polarization states are approximately equal, and the polarized beams of light can then pass through to a monolithic FEA integrator. The monolithic FEA integrator can cause the light beams to diverge, and the light beams are then directed for further processing, for example, by using a spatial light modulator to impart an image to the light beams, and projection optics to display the image on a screen. 
         [0027]    In some cases, optical projectors use a non-polarized light source, such as a light emitting diode (LED) or a discharge light, a polarization selecting element, a first polarization spatial modulator, and a second polarization selecting element. Since the first polarization selecting element rejects 50% of the light emitted from the non-polarized light source, polarization-selective projectors can often have a lower efficiency than non-polarized devices. 
         [0028]    One technique of increasing the efficiency of polarization-selective projectors is to add a polarization converter between the light source and the first polarization selecting element. Generally, there are two ways of designing a polarization converter used in the art. The first is to partially collimate the light emitting from the light source, pass the partially collimated beam of light through an array of lenses, and position an array of polarization converters at each focal point. The polarization converter typically has a polarizing beam splitter having polarization selective tilted film (for example MacNeille polarizer, a wire grid polarizer, or birefringent optical film polarizer), where the reflected polarization is reflected by a tilted reflector such that the reflected beam propagates parallel to the beam that is transmitted by the tilted polarization selective film. Either one or the other beams of polarized light is passed through half-wave retarders, such that both beams have the same polarization state. 
         [0029]    Another technique of converting the unpolarized light beam to a light beam having a single polarization state is to pass the entire beam of light through a tilted polarization selector, and the split beams are conditioned by reflectors and half-wave retarders such that a single polarization state is emitted. Illuminating a polarization selective spatial light modulator directly with a polarization converter can result in illuminance and color non-uniformity. 
         [0030]    In one particular embodiment, a polarization converter can incorporate a fly&#39;s eye array (FEA) to homogenize the light in a projection system. The output side of the polarization converter includes a monolithic FEA to homogenize the light. The input and output side of the monolithic FEA include the same number of lenses, with each lens on the output side centered approximately at the focal point of a matching lens at the input side. The lenses can be cylindrical, bi-convex, spherical, or aspherical; however, in many cases spherical lenses can be preferred. The fly&#39;s eye integrator and polarization converter can significantly improve the illuminance and color uniformity of the projector, as described elsewhere. 
         [0031]      FIGS. 1A-1C  shows a cross-section schematic of a color combiner  100  according to one aspect of the disclosure presented in co-pending U.S. patent application entitled TILTED DICHROIC COLOR COMBINER I (Attorney Docket Number 66530US002) filed on an even date herewith. In  FIGS. 1A-1C , the color combiner  100  includes a first light collection optics  105  including a first lens element  110  and a second lens element  120 . The first light collection optics  105  includes a light input surface  114  and an optical axis  102  perpendicular to the light input surface  114 . A first light source  140 , a second light source  150 , and an optional third light source  160  are each disposed on a light injection surface  104  that faces the light input surface  114 . A light output region  170  is located on the optical axis  102  and disposed on the light injection surface  104 . Each of the first, the second, and the optional third light sources  140 ,  150 ,  160 , are displaced from the optical axis  102 . Each of the first, the second, and the optional third light sources  140 ,  150 ,  160 , are disposed to inject a first color light  141 , a second color light  151 , and an optional third color light  161 , respectively, into the light input surface  114 , as described elsewhere. 
         [0032]    In one particular embodiment, color combiner  100  further includes a dichroic plate  130  disposed facing the first light collection optics  105  along the optical axis  102 , such that the first lens element  110  and the second lens elements  120  are between the dichroic plate  130  and the light input surface  114 . The dichroic plate  130  can be disposed at a tilt angle φ to the optical axis, and includes a first dichroic reflector  132  capable of reflecting the first color light  141  and transmitting all other colors of light. The dichroic plate  130  further includes a second dichroic reflector  134  capable of reflecting the second color light  151  and transmitting all other colors of light. The dichroic plate  130  still further includes an optional third dichroic reflector  136  that is capable of reflecting the optional third color light  161 . In some cases, for example when only a first and a second light source  140 ,  150  are included (that is, optional third light source  160  is omitted), second dichroic reflector can be instead a generic reflector such as a broadband mirror, since there is no need to transmit other wavelengths (that is, colors) of light. In some cases, for example when optional third light source  160  is included, optional third dichroic reflector  136  can also be a reflector such as a broadband mirror, since all other colors of light are already reflected by the other dichroic reflectors, prior to reaching the third dichroic reflector  136 . 
         [0033]    The dichroic plate  130  is fabricated such that each of the first, second, and optional third dichroic reflectors  132 ,  134 ,  136 , are tilted at a first dichroic tilt angle α 1 , a second dichroic tilt angle α 2 , and a third dichroic tilt angle α 3 , respectively, to the optical axis  102 . In some cases, as shown for example in  FIGS. 1A-1C , the first dichroic tilt angle α 1  can be the same as dichroic plate tilt angle φ, although it can also be different. Each of the first, second, and third dichroic tilt angles α 1 , α 2 , α 3 , can be selected to direct the reflected beams from each of the first, second, and optional third light sources  140 ,  150 ,  160 , through the light output region  170 , as described elsewhere. 
         [0034]    In one particular embodiment, first light collection optics  105  can be a light collimator that serves to collimate the light emitted from the first, second, and optional third light sources  140 ,  150 ,  160 . First light collection optics  105  can include a one lens light collimator (not shown), a two lens light collimator (shown), a diffractive optical element (not shown), or a combination thereof. The two lens light collimator has first lens element  110  that includes a first convex surface  112  disposed opposite the light input surface  114 . Second lens element  120  includes a second surface  122  facing the first convex surface  112 , and a third convex surface  124  opposite the second surface  122 . Second surface  122  can be selected from a convex surface, a planar surface, and a concave surface. 
         [0035]    Turning to  FIG. 1A , the path of the first color light  141  from first light source  140  can be traced through color combiner  100 . First color light  141  includes a first central light ray  142  travelling in the first light propagation direction, and a cone of rays within first input light collimation angle θ 1   i , the boundaries of which are represented by first boundary light rays  144 ,  146 . The first central light ray  142  is injected from first light source  140  into light input surface  114  in a direction generally parallel to the optical axis  102 , passes through first lens element  110 , second lens element  120 , and reflects from first dichroic reflector  132  such that the reflected beam is coincident with the optical axis  102  as shown. Each of the first boundary light rays  144 ,  146  are injected into the light input surface  114  in a direction generally at the first input light collimation angle θ 1   i  to the optical axis  102 , passes through first lens element  110 , second lens element  120 , and reflects from first dichroic reflector  132  such that the reflected beams are generally parallel to the optical axis  102  as shown. As can be seen from  FIG. 1A , the light collection optics  105  serve to collimate the first color light  141  passing from the first light source  140  to the dichroic plate  130 . 
         [0036]    Each of the first central light ray  142  and the first boundary light rays  144 ,  146 , reflect from the first dichroic reflector  132  and travel back through the light collection optics  105  as collimated light rays parallel to, and centered upon, the optical axis  102 . In one particular embodiment as shown in  FIG. 1A , the collimated light rays converge to exit the color combiner  100  through the light output region  170  as a first color light beam  148  having a first output collimation angle θ 2   o.    
         [0037]    Turning to  FIG. 1B , the path of the second color light  151  from second light source  150  can be traced through color combiner  100 . Second color light  151  includes a second central light ray  152  travelling in the second light propagation direction, and a cone of rays within second input light collimation angle θ 2   i , the boundaries of which are represented by second boundary light rays  154 ,  156 . The second central light ray  152  is injected from second light source  150  into light input surface  114  in a direction generally parallel to the optical axis  102 , passes through first lens element  110 , second lens element  120 , and reflects from second dichroic reflector  134  such that the reflected beam is coincident with the optical axis  102  as shown. Each of the second boundary light rays  154 ,  156  are injected into the light input surface  114  in a direction generally at the second input light collimation angle θ 2   i  to the optical axis  102 , passes through first lens element  110 , second lens element  120 , and reflects from second dichroic reflector  134  such that the reflected beams are generally parallel to the optical axis  102  as shown. As can be seen from  FIG. 1B , the light collection optics  105  serve to collimate the second color light  151  passing from the second light source  150  to the dichroic plate  130 . 
         [0038]    Each of the second central light ray  152  and the second boundary light rays  154 ,  156 , reflect from the second dichroic reflector  134  and travel back through the light collection optics  105  as collimated light rays parallel to, and centered upon, the optical axis  102 . In one particular embodiment as shown in  FIG. 1B , the collimated light rays converge to exit the color combiner  100  through the light output region  170  as a second color light beam  158  having a second output collimation angle θ 2   o.    
         [0039]    Turning to  FIG. 1C , the path of the optional third color light  161  from optional third light source  160  can be traced through color combiner  100 . Optional third color light  161  includes a third central light ray  162  travelling in the third light propagation direction, and a cone of rays within third input light collimation angle θ 3   i , the boundaries of which are represented by third boundary light rays  164 ,  166 . The third central light ray  162  is injected from optional third light source  160  into light input surface  114  in a direction generally parallel to the optical axis  102 , passes through first lens element  110 , second lens element  120 , and reflects from third dichroic reflector  136  such that the reflected beam is coincident with the optical axis  102  as shown. Each of the third boundary light rays  164 ,  166  are injected into the light input surface  114  in a direction generally at the third input light collimation angle θ 3   i  to the optical axis  102 , passes through first lens element  110 , second lens element  120 , and reflects from third dichroic reflector  136  such that the reflected beams are generally parallel to the optical axis  102  as shown. As can be seen from  FIG. 1C , the light collection optics  105  serve to collimate the optional third color light  161  passing from the optional third light source  160  to the dichroic plate  130 . 
         [0040]    Each of the third central light ray  162  and the third boundary light rays  164 ,  166 , reflect from the third dichroic reflector  136  and travel back through the light collection optics  105  as collimated light rays parallel to, and centered upon, the optical axis  102 . In one particular embodiment as shown in  FIG. 1C , the collimated light rays converge to exit the color combiner  100  through the light output region  170  as an optional third color light beam  168  having a third output collimation angle θ 3   o.    
         [0041]    In one particular embodiment, each of the first, the second, and the third input collimation angles θ 1   i , θ 2   i , θ 3   i  can be the same, and injection optics (not shown) associated with each of the first, the second, and the optional third input light sources  140 ,  150 ,  160 , can restrict these input collimation angles to angles between about 10 degrees and about 80 degrees, or between about 10 degrees to about 70 degrees, or between about 10 degrees to about 60 degrees, or between about 10 degrees to about 50 degrees, or between about 10 degrees to about 40 degrees, or between about 10 degrees to about 30 degrees or less. In some cases, the light collection optics  105  and the dichroic plate  130  can be fabricated such that each of the first, the second, and the third output collimation angles θ 1   o , θ 2   o , θ 3   o  can be the same, and also substantially equal to the respective input collimation angles. In one particular embodiment, each of the input collimation angles ranges from about 60 to about 70 degrees, and each of the output collimation angles also ranges from about 60 to about 70 degrees. 
         [0042]    The disclosure in  FIGS. 1A-1C  describes the color combiner  100  where the output first, second, and third color light beams  148 ,  158 ,  168  (that is, the combined output light) reflects from the dichroic plate  130 , then passes back through light output region  170  of light input surface  114 . In  FIGS. 1A-1C , the color combiner  100  further includes a section A-A′ designated on second lens element  120 , which will be described with reference to  FIG. 2  below. The present disclosure provides for an output light path that retains the collimated nature of the light leaving the second lens element  120 , and the combined output light does not pass through the light output region  170 , but instead is directed toward other optical components outside of first collection optics  105 . In this particular embodiment, each of the first, the second, and the optional third light sources  140 ,  150 ,  160 , can be disposed anywhere on light injection surface  104 , and in particular, at least one of the light sources can be disposed on the optical axis  102 , since the combined output light no longer passes thought the light input surface  114 . 
         [0043]      FIG. 2  shows a cross-section schematic appended to section A-A′ of  FIGS. 1A-1C  of color combiner element  200 , according to one aspect of the disclosure. Each of the elements  102 - 136  shown in  FIG. 2  correspond to like-numbered elements  102 - 136  shown in  FIGS. 1A-1C , which have been described previously. A portion of the third convex lens surface  124  of the second lens element  120  of  FIGS. 1A-1C  is shown, and the dichroic plate  130  is shown to be tilted at a tilt angle φ to the optical axis  102 . As can be seen in  FIG. 2 , the tilt angle φ has been increased so that the light reflected from the dichroic plate  130  does not return through the first collection optics  105 . In some cases, the tilt angle φ can be approximately 45 degrees, and is positioned such that each of the first, second, and optional third color light  141 ,  151 ,  161 , are reflected from the respective first, second, or third dichroic reflector  132 ,  134 ,  136  in an output direction  281  that retains the collimation of the output color combined light beam  280 . The pupil  128  of the color combiner  200  is shown to be located between the third convex lens surface  124  and the first dichroic reflector  132 . 
         [0044]      FIG. 3  shows a schematic diagram of an image projector  1 , according to one aspect of the disclosure. Image projector  1  includes a color combiner module  10  that is capable of injecting a partially collimated combined color light output  24  into a homogenizing polarization converter module  30  where the partially collimated combined color light output  24  becomes converted to a homogenized polarized light  45  that exits the homogenizing polarization converter module  30  and enters an image generator module  50 . The image generator module  50  outputs an imaged light  65  that enters a projection module  70  where the imaged light  65  becomes a projected imaged light  80 . 
         [0045]    In one aspect, color combiner module  10  includes different wavelength spectrum input light sources that are input through color combiner  200 , as described elsewhere. The color combiner  200  produces a partially collimated combined color light output  24  that includes the different wavelength spectrum lights, as described elsewhere. 
         [0046]    In one aspect, the input light sources are unpolarized, and the partially collimated combined color light output  24  is also unpolarized. The partially collimated combined color light output  24  can be a polychromatic combined light that comprises more than one wavelength spectrum of light. The partially collimated combined color light output  24  can be a time sequenced output of each of the received lights. In one aspect, each of the different wavelength spectra of light corresponds to a different color light (for example, red, green and blue), and the combined light output is white light, or a time sequenced red, green and blue light. For purposes of the description provided herein, “color light” and “wavelength spectrum light” are both intended to mean light having a wavelength spectrum range which may be correlated to a specific color if visible to the human eye. The more general term “wavelength spectrum light” refers to both visible and other wavelength spectrums of light including, for example, infrared light. 
         [0047]    According to one aspect, each input light source comprises one or more light emitting diodes (LED&#39;s). Various light sources can be used such as lasers, laser diodes, organic LED&#39;s (OLED&#39;s), and non solid state light sources such as ultra high pressure (UHP), halogen or xenon lamps with appropriate collectors or reflectors. Light sources, light collimators, lenses, and light integrators useful in the present invention are further described, for example, in Published U.S. Patent Application No. US 2008/0285129, the disclosure of which is herein included in its entirety. 
         [0048]    In one aspect, homogenizing polarization converter module  30  includes a polarization converter  40  that is capable of converting unpolarized partially collimated combined color light output  24  into homogenized polarized light  45 . Homogenizing polarization converter module  30  further can include a monolithic array of lenses  42 , such as a optional monolithic FEA of lenses described elsewhere that can homogenize and improve the uniformity of the partially collimated combined color light output  24  that exits the homogenizing polarization converter module  30  as homogenized polarized light  45 . Representative arrangements of optional FEA associated with the homogenizing polarization converter module  30  are described, for example, in co-pending U.S. Patent Ser. Nos. 61/346,183 entitled FLY EYE INTEGRATOR POLARIZATION CONVERTER (Attorney Docket No. 66247US002, filed May 19, 2010); 61/346,190 entitled POLARIZED PROJECTION ILLUMINATOR (Attorney Docket No. 66249US002, filed May 19, 2010); and 61/346,193 entitled COMPACT ILLUMINATOR (Attorney Docket No. 66360US002, filed May 19, 2010). 
         [0049]    In one aspect, image generator module  50  includes a polarizing beam splitter (PBS)  56 , representative imaging optics  52 ,  54 , and a spatial light modulator  58  that cooperate to convert the homogenized polarized light  45  into an imaged light  65 . Suitable spatial light modulators (that is, image generators) have been described previously, for example, in U.S. Pat. Nos. 7,362,507 (Duncan et al.), 7,529,029 (Duncan et al.); in U.S. Publication No. 2008-0285129-A1 (Magarill et al.); and also in PCT Publication No. WO2007/016015 (Duncan et al.). In one particular embodiment, homogenized polarized light  45  is a divergent light originating from each lens of the optional FEA. After passing through imaging optics  52 ,  54  and PBS  56 , homogenized polarized light  45  becomes imaging light  60  that uniformly illuminates the spatial light modulator. In one particular embodiment, each of the divergent light ray bundles from each of the lenses in the optional FEA illuminates a major portion of the spatial light modulator  58  so that the individual divergent ray bundles overlap each other. 
         [0050]    In one aspect, projection module  70  includes representative projection optics  72 ,  74 ,  76 , that can be used to project imaged light  65  as projected light  80 . Suitable projection optics  72 ,  74 ,  76  have been described previously, and are well known to those of skill in the art. 
         [0051]    Following are a list of embodiments of the present disclosure. 
         [0052]    Item 1 is a color combiner, comprising: a first light collection optics having a light input surface and an optical axis; a first and a second light source disposed to inject a first and a second color light into the light input surface, at least one of the first and second light sources displaced from the optical axis; and a dichroic plate disposed facing the first light collection optics opposite the light input surface and disposed at a tilt angle to the optical axis, the dichroic plate including: a first dichroic reflector capable of reflecting the first color light and transmitting other color light; and a second reflector capable of reflecting the second color light, wherein the first dichroic reflector and the second reflector are each tilted such that the first and the second color light are both reflected in an output direction, the first and the second color light forming a combined color light beam. 
         [0053]    Item 2 is the color combiner of item 1, wherein the first collection optics comprises light collimation optics. 
         [0054]    Item 3 is the color combiner of item 2, wherein the light collimation optics comprises a one lens design, a two lens design, a diffractive optical element, or a combination thereof. 
         [0055]    Item 4 is the color combiner of item 1 to item 3, wherein the first collection optics comprises: a first lens having a first convex surface opposite the light input surface; and a second lens having a second surface facing the first convex surface, and a third convex surface opposite the second surface. 
         [0056]    Item 5 is the color combiner of item 1 to item 4, wherein each of the first and second color light include a first divergence angle, and the combined beam includes a second divergence angle wherein the second divergence angle comprises an angle less than about 20 degrees. 
         [0057]    Item 6 is the color combiner of item 1 to item 5, wherein the second reflector comprises a broadband minor. 
         [0058]    Item 7 is the color combiner of item 1 to item 6, wherein the second reflector comprises a second dichroic reflector capable of reflecting the second color light and transmitting other color light. 
         [0059]    Item 8 is the color combiner of item 1 to item 7, further comprising a third light source disposed to inject a third color light into the light input surface and wherein the dichroic plate further comprises a third reflector capable of reflecting the third color light to exit in the output direction as the combined color light beam. 
         [0060]    Item 9 is the color combiner of item 8, wherein the third reflector comprises a broadband minor. 
         [0061]    Item 10 is the color combiner of item 8, wherein the third reflector comprises a third dichroic reflector capable of reflecting the third color light and transmitting other color light. 
         [0062]    Item 11 is the color combiner of item 5 to item 10, wherein the second divergence angle comprises an angle less than about 15 degrees. 
         [0063]    Item 12 is the color combiner of item 5 to item 11, wherein the second divergence angle comprises an angle less than about 12 degrees. 
         [0064]    Item 13 is a color combiner, comprising: a first lens having a first convex surface, a light input surface opposite the first convex surface, and an optical axis; a second lens centered on the optical axis, the second lens having a second surface facing the first convex surface, and a third convex surface opposite the second surface; a first, a second, and a third light source, at least two of the first, the second, and the third light source displaced from the optical axis and disposed to inject a first, a second, and a third color light into the light input surface; and a dichroic plate disposed facing the third convex surface and at a tilt angle to the optical axis, the dichroic plate, including: a first dichroic reflector capable of reflecting the first color light and transmitting the second and the third color light; a second dichroic reflector capable of reflecting the second color light and transmitting the third color light; and a third reflector capable of reflecting the third color light, wherein the first dichroic reflector, the second dichroic reflector, and the third reflector are each tilted such that the first, the second, and the third color light are each reflected in an output direction, the first, the second, and the third color light forming a combined color light beam. 
         [0065]    Item 14 is the color combiner of item 13, wherein each of the first, the second, and the third color light includes a first divergence angle, and the combined beam includes a second divergence angle wherein the second divergence angle comprises an angle less than about 20 degrees. 
         [0066]    Item 15 is the color combiner of item 13 or item 14, wherein the third reflector is a broadband minor. 
         [0067]    Item 16 is the color combiner of item 13 to item 15, wherein the third reflector is a third dichroic reflector capable of reflecting the third color light and transmitting other color light. 
         [0068]    Item 17 is the color combiner of item 14 to item 16, wherein the second divergence angle comprises an angle less than about 15 degrees. 
         [0069]    Item 18 is the color combiner of item 14 to item 17, wherein the second divergence angle comprises an angle less than about 12 degrees. 
         [0070]    Item 19 is an image projector, comprising: the color combiner of item 1 to item 18; a polarization converter disposed to accept the first, the second, and the third color light and output a polarized first, second, and third color light; a spatial light modulator disposed to impart an image to the polarized first, second, and third color light; and projection optics. 
         [0071]    Item 20 is the image projector of item 19, wherein the spatial light modulator comprises a liquid crystal on silicon (LCoS) imager or a transmissive liquid crystal display (LCD). 
         [0072]    Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. 
         [0073]    All references and publications cited herein are expressly incorporated herein by reference in their entirety into this disclosure, except to the extent they may directly contradict this disclosure. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.