Background

Projection systems used for projecting an image on a screen can use multiple color light sources, such as light emitting diodes (LED's), with different colors to generate the illumination light. Several optical elements are disposed between the LED's and the image display unit to combine and transfer the light from the LED'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.

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 projector systems decrease, 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.

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's eye array (FEA) homogenizer. Fly'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.

Pico and pocket projectors have limited available space for efficient illuminators, light integrators, and/or homogenizers. As a result, efficient and uniform light output from the optical devices used in these projectors (such as illuminators and polarization converters) can require compact and efficient optical designs. Summary

The disclosure generally relates to reflective fly-eye arrays, compact illuminators for projecting an image, and in particular illuminators that use a reflective fly-eye array (FEA) to enable the uniform illumination of a spatial light modulator such as a Liquid Crystal on Silicon (LCoS) reflective imager. The illuminators use collimation optics, a polarizing beamsplitter, and the reflective FEA to convert small aperture unpolarized Light Emitting Diode (LED) input light to polarized light that can uniformly illuminate the spatial light modulator.

In one aspect, the present disclosure provides a reflective fly-eye array that includes a substrate having a fly-eye array on a first major surface; and a reflector adjacent a second major surface opposite the first major surface, wherein a partially collimated input light beam that enters the fly-eye array is focused onto the reflector, reflects from the reflector, and exits the fly- eye array as a partially collimated output light beam.

In another aspect, the present disclosure provides an illuminator that includes light collection optics disposed to inject a partially collimated input light beam into a polarizing beam splitter (PBS), the PBS configured to output a partially collimated polarized light beam; and a reflective fly-eye array that includes a substrate having a fly-eye array on a first major surface; and a reflector adjacent a second major surface opposite the first major surface. The illuminator further includes a quarter-wave retarder disposed between the PBS and the reflector, wherein the partially collimated polarized light beam that leaves the PBS, enters the fly-eye array, is focused onto the reflector, reflects from the reflector, and exits the fly-eye array to re-enter the PBS as a partially collimated orthogonally polarized output light beam.

In yet another aspect, the present disclosure provides an image projector that includes a light illuminator; a spatial light modulator; and projection optics. The illuminator includes light collection optics disposed to inject a partially collimated input light beam into a polarizing beam splitter (PBS), the PBS configured to output a partially collimated polarized light beam; and a reflective fly-eye array that includes a substrate having a fly-eye array on a first major surface; and a reflector adjacent a second major surface opposite the first major surface. The illuminator further includes a quarter-wave retarder disposed between the PBS and the reflector, wherein the partially collimated polarized light beam that leaves the PBS, enters the fly-eye array, is focused onto the reflector, reflects from the reflector, and exits the fly-eye array to re-enter the PBS as a partially collimated orthogonally polarized output light beam. The spatial light modulator is disposed to intercept and image the substantially uniform partially collimated orthogonally polarized output light beam, and to direct the imaged light beam to the projection optics.

In yet another aspect, the present disclosure provides an illuminator that includes a light collection optics having a light input surface, a first and a second condenser lens, and a light output surface on 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 first face of a polarizing beam splitter (PBS) facing the light collection optics and adjacent the light output surface, the PBS including a first reflective polarizer disposed at a polarizer angle to the optical axis. The illuminator further includes a second reflective polarizer disposed between the light output surface and the first face of the

PBS, the first and second reflective polarizers aligned to reflect a second polarization direction; a reflective fly-eye array disposed on the optical axis and having a first major surface adjacent a third face of the PBS, the third face of the PBS opposite the first face of the PBS; a third condenser lens disposed on the optical axis between the third face of the PBS and the reflective fly-eye array; and a retarder disposed on the optical axis between the PBS and the reflector. The reflective fly-eye array includes a substrate having a fly-eye array on the first major surface; and a reflector adjacent a second major surface opposite the first major surface, wherein the first and second color light are focused on the reflector after passing through the fly-eye array, reflect from the reflector, and reflect from the first reflective polarizer to exit a second face of the PBS perpendicular to the first and second faces of the PBS as a substantially uniform first and second color light having the second polarization direction. In another aspect, the illuminator further includes a third light source disposed to inject a third color light into the light input surface and wherein the first, the second, and the third color light are focused on the reflector after passing through the fly-eye array, reflect from the reflector, and reflect from the first reflective polarizer to exit a second face of the PBS perpendicular to the first and second faces of the PBS as a substantially uniform first, second, and third color light having the second polarization direction.

In yet another aspect, the present disclosure provides an image projector that includes an illuminator; a spatial light modulator disposed to impart an image to the substantially uniform first and second color light having the second polarization direction; and projection optics disposed to project the image. The illuminator includes a light collection optics having a light input surface, a first and a second condenser lens, and a light output surface on 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 first face of a polarizing beam splitter (PBS) facing the light collection optics and adjacent the light output surface, the PBS including a first reflective polarizer disposed at a polarizer angle to the optical axis. The illuminator further includes a second reflective polarizer disposed between the light output surface and the first face of the PBS, the first and second reflective polarizers aligned to reflect a second polarization direction; a reflective fly-eye array disposed on the optical axis and having a first major surface adjacent a third face of the PBS, the third face of the PBS opposite the first face of the PBS; a third condenser lens disposed on the optical axis between the third face of the PBS and the reflective fly-eye array; and a retarder disposed on the optical axis between the PBS and the reflector. The reflective fly-eye array includes a substrate having a fly-eye array on the first major surface; and a reflector adjacent a second major surface opposite the first major surface, wherein the first and second color light are focused on the reflector after passing through the fly-eye array, reflect from the reflector, and reflect from the first reflective polarizer to exit a second face of the PBS perpendicular to the first and second faces of the PBS as a substantially uniform first and second color light having the second polarization direction.

In yet another aspect, the present disclosure provides an image projector that includes an illuminator; a spatial light modulator disposed to impart an image to the substantially uniform first, second, and third color light having the second polarization direction; and projection optics disposed to project the image. The illuminator includes a light collection optics having a light input surface, a first and a second condenser lens, and a light output surface on 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 first face of a polarizing beam splitter (PBS) facing the light collection optics and adjacent the light output surface, the PBS including a first reflective polarizer disposed at a polarizer angle to the optical axis. The illuminator further includes a second reflective polarizer disposed between the light output surface and the first face of the PBS, the first and second reflective polarizers aligned to reflect a second polarization direction; a reflective fly-eye array disposed on the optical axis and having a first major surface adjacent a third face of the PBS, the third face of the PBS opposite the first face of the PBS; a third condenser lens disposed on the optical axis between the third face of the PBS and the reflective fly-eye array; and a retarder disposed on the optical axis between the PBS and the reflector. The reflective fly-eye array includes a substrate having a fly-eye array on the first major surface; and a reflector adjacent a second major surface opposite the first major surface, wherein the first and second color light are focused on the reflector after passing through the fly-eye array, reflect from the reflector, and reflect from the first reflective polarizer to exit a second face of the PBS perpendicular to the first and second faces of the PBS as a substantially uniform first and second color light having the second polarization direction. The illuminator further includes a third light source disposed to inject a third color light into the light input surface and wherein the first, the second, and the third color light are focused on the reflector after passing through the fly-eye array, reflect from the reflector, and reflect from the first reflective polarizer to exit a second face of the PBS perpendicular to the first and second faces of the PBS as a substantially uniform first, second, and third color light having the second polarization direction.

In yet another aspect, the present disclosure provides a projection system that includes an illuminator having a light collection optics comprising a light input surface, a first and a second condenser lens, and a light output surface on an optical axis; a first, a second, and a third 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 first face of a polarizing beam splitter (PBS) facing the light collection optics and adjacent the light output surface, the PBS including a first reflective polarizer disposed at a polarizer angle to the optical axis. The illuminator further includes a second reflective polarizer disposed between the light output surface and the first face of the PBS, the first and second reflective polarizers aligned to reflect a second polarization direction; a reflective fly-eye array disposed on the optical axis and having a first major surface adjacent a third face of the PBS, the third face of the PBS opposite the first face of the PBS. The reflective fly-eye array includes a substrate having a fly-eye array on the first major surface; and a reflector adjacent a second major surface opposite the first major surface. The illumination system still further includes a third condenser lens disposed on the optical axis between the third face of the PBS and the reflective fly-eye array; and a retarder disposed on the optical axis between the PBS and the reflector, wherein the first, second, and third color light are focused on the reflector after passing through the fly-eye array, reflect from the reflector, and reflect from the first reflective polarizer to exit a second face of the PBS perpendicular to the first and second faces of the PBS as a substantially uniform first, second, and third color light having the second polarization direction. The projection system further includes a reflective imager disposed to intercept the substantially uniform first, second, and third color light having the second polarization direction, wherein the substantially uniform first, second, and third color light having the second polarization direction is reflected and rotated from the reflective imager into the second face of the PBS as an imaged first, second, and third color light having a first polarization direction orthogonal to the second polarization direction; and projection optics disposed to project the imaged first, second, and third color light having a first polarization direction that exits a fourth face of the PBS opposite the second face of the PBS.

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

Throughout the specification reference is made to the appended drawings, where like reference numerals designate like elements, and wherein:

FIGS. 1A-1C show a cross-sectional schematic of a reflective fly-eye array illuminator and paths of light through the reflective fly-eye array illuminator; and

FIG. 2 shows a cross-sectional schematic of a portion of reflective fly-eye illuminator and paths of light through the reflective fly-eye array illuminator.

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

The disclosure generally relates to reflective fly-eye arrays, compact illuminators for projecting an image, and in particular illuminators that use a reflective fly-eye array (FEA) to enable the uniform illumination of a spatial light modulator such as a Liquid Crystal on Silicon (LCoS) reflective imager. The illuminators use collimation optics, a polarizing beamsplitter, and the reflective FEA to convert small aperture unpolarized Light Emitting Diode (LED) input light to polarized light that can uniformly illuminate the spatial light modulator.

In the following description, reference is made to the accompanying drawings that forms a part hereof and in which are shown by way of illustration. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

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 in all instances 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.

As used in this specification and the appended claims, the singular forms "a," "an," and

"the" encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

Spatially related terms, including but not limited to, "lower," "upper," "beneath," "below," "above," and "on top," if used herein, are utilized for ease of description to describe spatial relationships of an element(s) to another. Such spatially related terms encompass different orientations of the device in use or operation in addition to the particular orientations depicted in the figures and described herein. For example, if an object depicted in the figures is turned over or flipped over, portions previously described as below or beneath other elements would then be above those other elements.

As used herein, when an element, component or layer for example is described as forming a "coincident interface" with, or being "on" "connected to," "coupled with" or "in contact with" another element, component or layer, it can be directly on, directly connected to, directly coupled with, in direct contact with, or intervening elements, components or layers may be on, connected, coupled or in contact with the particular element, component or layer, for example. When an element, component or layer for example is referred to as being "directly on," "directly connected to," "directly coupled with," or "directly in contact with" another element, there are no intervening elements, components or layers for example.

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.

Also for the purposes of the description provided herein, the term "aligned to a desired polarization state" is intended to associate the alignment of the pass axis of an optical element to a desired polarization state of light that passes through the optical element, that is, a desired polarization state such as s-polarization, p-polarization, right-circular polarization, left-circular polarization , or the like. In one embodiment described herein with reference to the Figures, an optical element such as a polarizer aligned to the first polarization state means the orientation of the polarizer that passes the p-polarization state of light, and reflects or absorbs the second polarization state (in this case the s-polarization state) of light. It is to be understood that the polarizer can instead be aligned to pass the s-polarization state of light, and reflect or absorb the p-polarization state of light, if desired.

Also for the purposes of the description provided herein, the term "facing" refers to one element disposed so that a perpendicular line from the surface of the element follows an optical path that is also perpendicular to the other element. One element facing another element can include the elements disposed adjacent each other. One element facing another element further includes the elements separated by optics so that a light ray perpendicular to one element is also perpendicular to the other element.

In one particular embodiment, an illuminator 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.

In one aspect, the disclosure provides a compact method of efficiently homogenizing the light output to an imaging device that arises 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 polarizing beam splitter (PBS) and passes one polarization of the light to a reflective fly-eye array (FEA) assembly. The reflective FEA then can focus the light onto a reflector and return the light back through the

FEA, spreading and homogenizing the beam as it enters the PBS. The PBS can then reflect the red, green, and blue light to the imaging device as a homogenized light beam of each of the three colors. Time sequential activation of each of the LEDs can be used with the imaging device to generate a colored image that can be subsequently directed through to imaging optics.

In one particular embodiment, a illuminator is disclosed that reduces the combined etendue of two different colored light sources, where light emitted from the light sources are at least partially collimated into substantially overlapping beams of light. The beams of light are split into polarized beams by a polarizing beam splitter, each polarized beam focused using the FEA onto a reflector either before or after conversion to circularly polarized light with a ¼ wave retarder, and the reflected circularly polarized light expands and passes back through the FEA back into the PBS. The reflected circularly polarized light is converted to linearly polarized light with the polarization state orthogonal to the or incident polarized beam as it passes again through the ¼-wave plate, and the combined beams of light have a reduced etendue.

In some cases, the LEDs may be used to illuminate reflective LCDs such as Liquid Crystal on Silicon (LCoS) imagers and sent back through the PBS to projection optics. In some cases, the LEDs may be used to illuminate transmissive LCSs and sent directly through to projection optics. 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 reflective FEAs to make two or more colors of LEDs spatially overlap, such that they appear to be emitting from the same region. In one particular embodiment, the present disclosure describes an article that combines different color LEDs using reflective FEAs that are at near normal angles to the incident light beam.

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 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. The reflective FEA may consist of a one or two dimensional array of lenses, with at least one dimension having 2 to about 20 or more lenses, as described elsewhere.

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 illuminator, 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 can be 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.

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 non-uniformity, leading to artifacts in the displayed image. Therefore, in systems with polarization converters, a homogenization system can be desirable, as described elsewhere.

In one particular embodiment, an illuminator for an image projector includes a light source in which emitted unpolarized light is directed into collimating optics and pass though a reflective or absorptive polarizer. The polarized light beams can then pass through a PBS to a reflective FEA. A retarder, such as a quarter-wave retarder, can be positioned between the PBS and the reflector of the FEA to convert the polarized light to circularly polarized light. The reflective FEA then causes the light beams to diverge and rotate to the orthogonal polarization direction, and pass back through the retarder and PBS, and the light beams are then reflected from the polarizer in the PBS and pass though 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.

In one particular embodiment, the reflective FEA is used to homogenize the light in a projection system. The lenses of the reflective FEA can be cylindrical, bi-convex, spherical, or aspherical; however, in many cases spherical lenses can be preferred. The fly's eye lenses focus the input light to a reflector, and output the reflected light back through the lens to spatially homogenize the light intensity, and also rotate the polarization direction such that the light can be directed toward imaging and projection devices, as described elsewhere. Light collimation optics can provide a technique for inputting several colors of light to be combined, and the reflective FEA can compensate for lights that are input at positions removed from the optical axis of the light collimation optics. The incorporation of the reflective FEA into the light path can significantly improve the illuminance and color uniformity of the projector, as described elsewhere.

FIG. 1A-1C shows a cross-sectional schematic of a reflective fly-eye array illuminator 100 and paths of light through the reflective fly-eye array illuminator 100, according to one aspect of the disclosure. Illuminator 100 includes a light collection optic 105 including a first lens element 110 and a second lens element 120. The 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. 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 a third color light 161 , respectively, into the light input surface 114, as described elsewhere.

In one particular embodiment, 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. 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 light output surface 123 opposite the second surface 122. Second surface 122 can be selected from a convex surface, a planar surface, and a concave surface, as known to one of skill in the art.

Illuminator 100 further includes a polarizing beam splitter (PBS) 130 that has a first prism 135, a second prism 136, and a reflective polarizer 137 disposed on a diagonal face between them. The first prism 135 includes a first prism face 131 and a second prism face 132, and the second prism 136 includes a third prism face 133 opposite the second prism face 132 and a fourth prism face 134 opposite the first prism face 131.

The PBS includes an input surface shown in FIGS. 1A-1C as second prism face 132, an output surface shown in FIGS. 1A-1C as fourth prism face 134, and a reflective polarizer 137. In one embodiment, the reflective polarizer 137 can be aligned to a first polarization direction 139. The reflective polarizer 137 is positioned so that light from the first, the second, and the optional third light source 140, 150, 160, input to the PBS 130 intercepts the reflective polarizer 137 at approximately a 45 degree angle. In one embodiment, the intercept angle ranges from 35 to 55 degrees; from 40 to 50 degrees; from 43 to 48 degrees; or from 44.5 to 45.5 degrees.

The reflective polarizer 137 can be any known reflective polarizer such as a MacNeille polarizer, a wire grid polarizer, or a multilayer optical film polarizer. According to one embodiment, a multilayer optical film polarizer can be a preferred first reflective polarizer. The first reflective polarizer can be disposed between the diagonal faces of two prisms, or it can be a free-standing film such as a pellicle. In some embodiments, the PBS light utilization efficiency is improved when the first reflective polarizer is disposed between two prisms. In this embodiment, some of the light traveling through the PBS which would otherwise be lost from the optical path can undergo Total Internal Reflection (TIR) from the prism faces and rejoin the optical path. For at least this reason, the following description is directed to PBSs where first reflective polarizers are disposed between the diagonal faces of two prisms; however, it is to be understood that the PBS can function in the same manner when used as a pellicle. In one aspect, all of the external faces of the PBS prisms are highly polished so that light entering the PBS undergoes TIR. In this manner, light is contained within the PBS and the light is partially homogenized while still preserving etendue. The illuminator 100 can also include an optional pre-polarizer 107 that can restrict light that enters the PBS 130 to a single polarization state, such as p-polarized light, such that the illuminator 100 exhibits improved contrast. The pre-polarizer 107 can be the same as the reflective polarizer 137, or it can be different, such as an absorptive polarizer. In one particular embodiment, a reflective polarizer can be preferred.

In one particular embodiment, illuminator 100 further includes a third lens 125 positioned along the optical axis 102 and has a third input face 124 adjacent the third prism face 133, and a third surface 127 adjacent a reflective FEA 170. Third surface 127 can be selected from a convex surface, a planar surface, and a concave surface; in some cases, collimation of the light entering the reflective FEA 170 can be desired and can specify the curvature of third surface 127, as known to one of skill in the art.

The reflective FEA 170 includes a FEA 172 having a plurality of lenses 171 opposite a first major surface 173. The first major surface 173 can coincide with a focal point of the FEA, and a reflector 176 is disposed adjacent the first major surface 173. The reflector 176 can be positioned adjacent a second major surface 175 of a supporting substrate 174, as shown in the figure.

A retarder 109, such as a quarter- wave retarder, is positioned between the reflective polarizer 137 and the reflector 176. The retarder 109 participates with the reflective polarizer 137 and the reflector 176 to change the polarization state of light reflecting back into the PBS 130, as described elsewhere. The retarder can be positioned in any desired location between the reflective polarizer 137 and the reflector 176, for example: immediately adjacent the reflective polarizer 137 (not shown); between the third lens 125 and the third prism face 133 (shown); between the third lens 125 and the reflective FEA 170 (not shown); or between the first major surface 173 of the FEA 172 and the reflector 176 (not shown). The position of the retarder 109 can reduce the impact of birefringence on the optical components of the FEA 172, as known to one of skill in the art.

The retarder can provide any desired retardation, such as an eighth-wave retarder, a quarter-wave retarder, and the like. In embodiments described herein, there is an advantage to using a quarter-wave retarder and the associated reflective polarizer. Linearly polarized light is changed to circularly polarized light as it passes through a quarter- wave retarder aligned at an angle of 45° to the axis of light polarization. Subsequent reflections from the reflector 176 and transmission through the quarter- wave retarder 109 in the illuminator result in efficient combined light output from the light combiner. In contrast, linearly polarized light is changed to a polarization state partway between s-polarization and p-polarization (either elliptical or linear) as it passes through other retarders and orientations, and can result in a lower efficiency of the illuminator.

According to one embodiment described below, the illuminator receives unpolarized light from different color unpolarized light sources, and produces a light output that is polarized. According to one particular embodiment, the retarder is a quarter-wave retarder having a slow- axis aligned at 45 degrees to the first polarization direction 139. Further, as known to one of skill in the art, light input surface 114, light output surface 123, and third input face 124, can each be selected individually from a convex surface, a planar surface, and a concave surface; however, in some cases a planar surface can be preferred.

The path of first, second, and third color light 141, 151, 161, can be traced through the illuminator 100, with reference to FIGS. 1A-1C. FIG. 1A shows the first light source 140, disposed along the optical axis 102, injecting first color light 141 into the light input surface 114. First color light 141 includes a central first color light ray 142 and two boundary first color light rays 144, 146, that represent the light within a first input collimation angle Θ1. Each of the first color light rays 142, 144, 146, pass through light collection optics 105 and optional pre-polarizer 107 and enter second prism face 132 of PBS 130 as an at least partially collimated first color light beam having the first polarization direction, for example, p-polarized light. Each of the first color p-polarized light rays 142p, 144p, 146p intercept and pass through reflective polarizer 137, and exit PBS 130 through third prism face 133. Each of the first color p-polarized light rays 142p, 144p, 146p, pass through quarter- wave retarder 109 becoming circular polarized first color light rays 142c, 144c, 146c which pass through FEA 172, are focused on and reflect from reflector 176, changing the direction of circular polarization. Circular polarized first color light rays 142c, 144c, 146c then are expanded back through FEA 172 and pass again through quarter- wave retarder 109 becoming s-polarized first color light rays 142s, 144s, 146s, re-enter PBS 130 through third prism face 133, reflect from reflective polarizer 137, and exit PBS 130 through fourth prism face 134 as s-polarized first color light rays 142s, 144s, 146s.

The s-polarized first color light rays 142s, 144s, 146s that exit the PBS 130 intercept spatial light modulator (SLM) 180 uniformly, and depending on the nature of the SLM 180, are either directed back into the PBS 130 as the first color portion of a reflected p-polarized imaged light 185 (for example, for a reflective LCoS SLM), or transmitted through the SLM 180 to transmission imaging optics (not shown) as the first color portion of a transmitted imaged light 189 (for example, for a transmissive LC display). Reflected p-polarized imaged light 185 passes unchanged through PBS 130 and enters projection optics 190 where it is directed as projected image 199 to a projection screen (not shown).

FIG. IB shows the second light source 150, disposed such that it is displaced from the optical axis 102, injecting second color light 151 into the light input surface 114. Second color light 151 includes a central second color light ray 152 and two boundary second color light rays 154, 156, that represent the light within a second input collimation angle Θ2. Each of the second color light rays 152, 154, 156, pass through light collection optics 105 and optional pre-polarizer 107 and enter second prism face 132 of PBS 130 as an at least partially collimated second color light beam having the first polarization direction, for example, p-polarized light. Each of the second color p-polarized light rays 152p, 154p, 156p intercept and pass through reflective polarizer 137, and exit PBS 130 through third prism face 133. Each of the second color p- polarized light rays 152p, 154p, 156p, pass through quarter- wave retarder 109 becoming circular polarized second color light rays 152c, 154c, 156c which pass through FEA 172, are focused on and reflect from reflector 176, changing the direction of circular polarization. Circular polarized second color light rays 152c, 154c, 156c then are expanded back through FEA 172 and pass again through quarter- wave retarder 109 becoming s-polarized second color light rays 152s, 154s, 156s, re-enter PBS 130 through third prism face 133, reflect from reflective polarizer 137, and exit PBS 130 through fourth prism face 134 as s-polarized second color light rays 152s, 154s, 156s. The s-polarized second color light rays 152s, 154s, 156s that exit the PBS 130 intercept spatial light modulator (SLM) 180 uniformly, and depending on the nature of the SLM 180, are either directed back into the PBS 130 as the second color portion of the reflected p-polarized imaged light 185 (for example, for a reflective LCoS SLM), or transmitted through the SLM 180 to transmission imaging optics (not shown) as the second color portion of the transmitted imaged light 189 (for example, for a transmissive LC display). Reflected p-polarized imaged light 185 passes unchanged through PBS 130 and enters projection optics 190 where it is directed as projected image 199 to a projection screen (not shown).

FIG. 1C shows the third light source 160, disposed such that it is displaced from the optical axis 102, injecting third color light 161 into the light input surface 114. Third color light 161 includes a central third color light ray 162 and two boundary third color light rays 164, 166, that represent the light within a third input collimation angle Θ3. Each of the third color light rays 162, 164, 166, pass through light collection optics 105 and optional pre-polarizer 107 and enter second prism face 132 of PBS 130 as an at least partially collimated third color light beam having the first polarization direction, for example, p-polarized light. Each of the third color p- polarized light rays 162p, 164p, 166p intercept and pass through reflective polarizer 137, and exit PBS 130 through third prism face 133. Each of the third color p-polarized light rays 162p, 164p, 166p, pass through quarter- wave retarder 109 becoming circular polarized third color light rays 162c, 164c, 166c which pass through FEA 172, are focused on and reflect from reflector 176, changing the direction of circular polarization. Circular polarized third color light rays

162c, 164c, 166c then are expanded back through FEA 172 and pass again through quarter- wave retarder 109 becoming s-polarized third color light rays 162s, 164s, 166s, re-enter PBS 130 through third prism face 133, reflect from reflective polarizer 137, and exit PBS 130 through fourth prism face 134 as s-polarized third color light rays 162s, 164s, 166s.

The s-polarized third color light rays 162s, 164s, 166s that exit the PBS 130 intercept spatial light modulator (SLM) 180 uniformly, and depending on the nature of the SLM 180, are either directed back into the PBS 130 as the third color portion of the reflected p-polarized imaged light 185 (for example, for a reflective LCoS SLM), or transmitted through the SLM 180 to transmission imaging optics (not shown) as the third color portion of the transmitted imaged light 189 (for example, for a transmissive LC display). Reflected p-polarized imaged light 185 passes unchanged through PBS 130 and enters projection optics 190 where it is directed as projected image 199 to a projection screen (not shown). In one particular embodiment, at least one of the first input collimation angle Θ1, the second input collimation angle Θ2, and the third input collimation angle Θ3 can be the same, and injection optics (not shown) associated with each of the first, the second, and the optional third 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 one particular embodiment, each of the input collimation angles ranges from about 60 to about 70 degrees, and each of the output collimation angles can range from less than about 20 degrees, or less than about 15 degrees, or even less than about 12 degrees; that is, the output light can be well collimated.

FIG. 2 shows a cross-sectional schematic of a portion of reflective fly-eye illuminator 200 and paths of light through the reflective fly-eye array illuminator 200, according to one aspect of the disclosure. Each of the elements 209-276 shown in FIG. 2 correspond to like- numbered elements 109-176 shown in FIGS. 1 A-IC, which have been described previously. For example, second prism 236 shown in FIG. 2 corresponds to second prism 136 shown in FIGS. 1A-1C, and so on. In FIG. 2, the position of the retarder 209 has been moved from that shown in FIGS. 1A-1C, to a new position as retarder 209' between the FEA 272 and reflector 276. In this manner, p-polarized light, such as, for example, first color p-polarized central ray 242p enters FEA 272, reflects and rotates from retarder 209' and reflector 276, and exits FEA 272 as first color s-polarized central ray 242s. In this manner, it can be possible to use a birefringent material for the FEA 272 and still retain efficient performance of the illuminator 200. The remainder of the path of light rays is unchanged from that described with reference to FIGS. 1A- 1C.

Following are a list of embodiments of the present disclosure.

Item 1 is a reflective fly-eye array, comprising: a substrate having a fly-eye array on a first major surface; and a reflector adjacent a second major surface opposite the first major surface, wherein a partially collimated input light beam that enters the fly-eye array is focused onto the reflector, reflects from the reflector, and exits the fly-eye array as a partially collimated output light beam. Item 2 is the reflective fly-eye array of item 1, wherein the fly-eye array comprises a plurality of lenses, each of the plurality of lenses capable of intercepting and focusing a portion of the partially collimated input light beam onto the reflector.

Item 3 is the reflective fly-eye array of item 1 or item 2, further comprising a quarter- wave retarder disposed between the second major surface and the reflector.

Item 4 is the reflective fly-eye array of item 3, wherein the partially collimated input light beam is polarized in a first polarization direction, and the quarter-wave retarder is aligned such that the partially collimated output light beam is polarized in a second polarization direction orthogonal to the first polarization direction.

Item 5 is an illuminator, comprising: light collection optics disposed to inject a partially collimated input light beam into a polarizing beam splitter (PBS), the PBS configured to output a partially collimated polarized light beam; a reflective fly-eye array, comprising: a substrate having a fly-eye array on a first major surface; a reflector adjacent a second major surface opposite the first major surface; and a quarter-wave retarder disposed between the PBS and the reflector, wherein the partially collimated polarized light beam that leaves the PBS, enters the fly-eye array, is focused onto the reflector, reflects from the reflector, and exits the fly-eye array to re-enter the PBS as a partially collimated orthogonally polarized output light beam.

Item 6 is the light illuminator of item 5, wherein the quarter- wave retarder is disposed within the reflective fly-eye array, between the second major surface and the reflector.

Item 7 is the light illuminator of item 5, wherein the quarter- wave retarder is disposed between the PBS and the reflective fly-eye array.

Item 8 is the light illuminator of item 5 to item 7, wherein the partially collimated orthogonally polarized output light beam reflects from a reflective polarizer and exits the PBS as a substantially uniform partially collimated orthogonally polarized output light beam.

Item 9 is an image projector, comprising: the light illuminator of item 5 to item 8; a spatial light modulator; and projection optics, wherein the spatial light modulator is disposed to intercept and image the substantially uniform partially collimated orthogonally polarized output light beam, and to direct the imaged light beam to the projection optics.

Item 10 is the image projector of item 9, wherein the spatial light modulator comprises a liquid crystal on silicon (LCoS) imager or a transmissive liquid crystal display (LCD).

Item 11 is an illuminator, comprising: a light collection optics comprising a light input surface, a first and a second condenser lens, and a light output surface on 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; a first face of a polarizing beam splitter (PBS) facing the light collection optics and adjacent the light output surface, the PBS including a first reflective polarizer disposed at a polarizer angle to the optical axis; a second reflective polarizer disposed between the light output surface and the first face of the PBS, the first and second reflective polarizers aligned to reflect a second polarization direction; a reflective fly-eye array disposed on the optical axis and having a first major surface adjacent a third face of the PBS, the third face of the PBS opposite the first face of the PBS, the reflective fly-eye array comprising: a substrate having a fly-eye array on the first major surface; a reflector adjacent a second major surface opposite the first major surface; a third condenser lens disposed on the optical axis between the third face of the PBS and the reflective fly-eye array; and a retarder disposed on the optical axis between the PBS and the reflector, wherein the first and second color light are focused on the reflector after passing through the fly-eye array, reflect from the reflector, and reflect from the first reflective polarizer to exit a second face of the PBS perpendicular to the first and second faces of the PBS as a substantially uniform first and second color light having the second polarization direction.

Item 12 is the illuminator of item 11 , wherein the light collection optics comprises light collimation optics.

Item 13 is the illuminator of item 12, wherein the light collimation optics comprises a one lens design, a two lens design, a diffractive optical element, or a combination thereof.

Item 14 is the illuminator of item 11 to item 13, wherein the first condenser lens includes a first convex surface opposite the light input surface, and the second condenser lens includes a second convex surface facing the first convex surface, the light output surface opposite the second convex surface.

Item 15 is the illuminator of item 11 to item 14, wherein each of the first and second color light include a first divergence angle less than about 25 degrees, and the substantially uniform first and second color light having the second polarization direction includes a second divergence angle that comprises an angle less than about 25 degrees.

Item 16 is the illuminator of item 11 to item 15, wherein the reflector comprises a broadband mirror.

Item 17 is the illuminator of item 11 to item 16, wherein the retarder comprises a quarter- wave retarder disposed between the PBS and the third condenser lens. Item 18 is the illuminator of item 11 to item 17, wherein the retarder comprises a quarter- wave retarder disposed between the second major surface of the fly-eye array substrate and the reflector.

Item 19 is the illuminator of item 11 to iteml 8, further comprising a third light source disposed to inject a third color light into the light input surface and wherein the first, the second, and the third color light are focused on the reflector after passing through the fly-eye array, reflect from the reflector, and reflect from the first reflective polarizer to exit a second face of the PBS perpendicular to the first and second faces of the PBS as a substantially uniform first, second, and third color light having the second polarization direction.

Item 20 is the illuminator of item 15, wherein the second divergence angle comprises an angle less than about 20 degrees.

Item 21 is the illuminator of item 15, wherein the second divergence angle comprises an angle less than about 15 degrees.

Item 22 is an image projector, comprising: the illuminator of item 11 to item 18; a spatial light modulator disposed to impart an image to the substantially uniform first and second color light having the second polarization direction; and projection optics disposed to project the image.

Item 23 is the image projector of item 22, wherein the spatial light modulator comprises a liquid crystal on silicon (LCoS) imager or a transmissive liquid crystal display (LCD).

Item 24 is an image projector, comprising: the illuminator of item 19 to item 21; a spatial light modulator disposed to impart an image to the substantially uniform first, second, and third color light having the second polarization direction; and projection optics disposed to project the image.

Item 25 is the image projector of item 24, wherein the spatial light modulator comprises a liquid crystal on silicon (LCoS) imager or a transmissive liquid crystal display (LCD).

Item 26 is a projection system, comprising: an illuminator, comprising: a light collection optics comprising a light input surface, a first and a second condenser lens, and a light output surface on an optical axis; a first, a second, and a third 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; a first face of a polarizing beam splitter (PBS) facing the light collection optics and adjacent the light output surface, the PBS including a first reflective polarizer disposed at a polarizer angle to the optical axis; a second reflective polarizer disposed between the light output surface and the first face of the PBS, the first and second reflective polarizers aligned to reflect a second polarization direction; a refiective fly-eye array disposed on the optical axis and having a first major surface adjacent a third face of the PBS, the third face of the PBS opposite the first face of the PBS, the reflective fly-eye array comprising: a substrate having a fly-eye array on the first major surface; a reflector adjacent a second major surface opposite the first major surface; a third condenser lens disposed on the optical axis between the third face of the PBS and the reflective fly-eye array; a retarder disposed on the optical axis between the PBS and the reflector, wherein the first, second, and third color light are focused on the reflector after passing through the fly-eye array, reflect from the reflector, and reflect from the first reflective polarizer to exit a second face of the PBS perpendicular to the first and second faces of the PBS as a substantially uniform first, second, and third color light having the second polarization direction; a reflective imager disposed to intercept the substantially uniform first, second, and third color light having the second polarization direction, wherein the substantially uniform first, second, and third color light having the second polarization direction is reflected and rotated from the reflective imager into the second face of the PBS as an imaged first, second, and third color light having a first polarization direction orthogonal to the second polarization direction; and projection optics disposed to project the imaged first, second, and third color light having a first polarization direction that exits a fourth face of the PBS opposite the second face of the PBS.

Item 27 is the projection system of item 26, wherein the light collection optics comprises light collimation optics.

Item 28 is the projection system of item 26 or item 27, wherein the light collimation optics comprises a one lens design, a two lens design, a diffractive optical element, or a combination thereof.

Item 29 is the projection system of item 26 to item 28, wherein the first condenser lens includes a first convex surface opposite the light input surface, and the second condenser lens includes a second convex surface facing the first convex surface, the light output surface opposite the second convex surface.

Item 30 is the projection system of item 26 to item 29, wherein each of the first and second color light include a first divergence angle less than about 25 degrees, and the

substantially uniform first and second color light having the second polarization direction includes a second divergence angle that comprises an angle less than about 25 degrees. Item 31 is the projection system of item 26 to item 30, wherein the reflector comprises a broadband mirror.

Item 32 is the projection system of item 26 to item 31, wherein the retarder comprises a quarter-wave retarder disposed between the PBS and the third condenser lens.

Item 33 is the projection system of item 26 to item 32, wherein the retarder comprises a quarter-wave retarder disposed between the second major surface of the fly-eye array substrate and the reflector.

Item 34 is the projection system of item 30 to item 33, wherein the second divergence angle comprises an angle less than about 20 degrees.

Item 35 is the projection system of item 30 to item 33, wherein the second divergence angle comprises an angle less than about 15 degrees.

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.

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.