Patent ID: 12189126

In the figures, like reference numerals designate like elements.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As mentioned above, we have developed new families of projection systems and components thereof that are well suited to miniaturization. These systems and components may use one or more of the following features: a folded optical path, as in a reflective cavity or a (e.g. polarizing) beamsplitter; an illumination beam that is converging at the place where it impinges upon the spatial light modulator; a beamsplitter that uses opposed prisms of substantially different sizes; a beamsplitter whose obliquely disposed partial reflector defines a first rectangular reference space, and where at least a portion of the light source or at least a portion of the projector lens is disposed within such first rectangular reference space; a system in which a ratio of areas of the first rectangular reference space and a second rectangular reference space is within a range from 30% to 70% or 40% to 70%, where the second rectangular reference space is just large enough to encompass the optical components of the projector such as a beamsplitter, the light source, the spatial light modulator, and the projector lens; a system in which the projector lens is small compared to the active area of the spatial light modulator, e.g., a lateral dimension of the projector lens, and/or one or more of its individual lenses, may be no more than 30% or 50% or 70% of the corresponding lateral dimension of the spatial light modulator; a system in which the collection efficiency of the projector lens is substantially uniform over the area of the spatial light modulator.

Turning then toFIG.1, we see there a schematic top view of a compact projector110. For reference purposes, the projector110is drawn in the context of a Cartesian x-y-z coordinate system, where it is assumed that the x-z plane defines a horizontal plane and the y-axis is a vertical axis, but other conventions may also be used. The projector110includes an illuminator140, a spatial light modulator150, and a projector lens160. The z-axis of the coordinate system is assumed to be parallel to an optical axis142of the projector110and its component parts. The illuminator140produces an output illumination beam172that impinges upon the spatial light modulator150. In exemplary embodiments, the output illumination beam172is substantially spatially uniform over the entire active area of such modulator150, so that the brightness of the projected image is also substantially uniform.

A conventional electronic controller (not shown) couples to the spatial light modulator150and controls the states of the individual elements (pixel elements)152in an image-wise fashion. The pixel elements152are usually arranged in a grid of rows and columns to provide a rectangular active area. A given pixel element152may have two states—“on” or “off”, as in the case of a monochrome display—or it may have red, green, and blue sub-elements to provide a full color image. Other conventional configurations of the spatial light modulator150are also contemplated. In the embodiment ofFIG.1, the spatial light modulator150is a transmissive-type modulator. The spatial light modulator150thus converts the output illumination beam172into a transmitted patterned light beam174which contains the image-wise or spatially patterned information from the electronic controller. The modulator150may be a non-polarized transmissive device, such as a microelectromechanical system (MEMS), or it may be a liquid crystal based modulator. In the latter case, the modulator150selectively rotates the polarization of the light exiting the array of pixels, and further in that case a polarizer (not shown) is inserted into the projector110after the spatial light modulator to filter out “on” pixels from “off” pixels.

The patterned light beam174is then intercepted by the projector lens160to produce a projected output beam176. The output beam176may produce a real image, e.g. an image that can be displayed on a physical surface or substrate remotely disposed relative to the projector110, or it may produce a virtual image, e.g. one that may be viewed directly by the eye of a user. The projector lens160typically, but not in all cases, is a module that includes a plurality of individual lenses arranged in series. In the embodiment ofFIG.1, the projector lens160includes individual lenses161,162,163,164, and165. These lenses are drawn schematically, but the reader will understand that the individual lenses have curved surfaces, suitable thicknesses, and are composed of suitable optical glasses or plastics, to provide high quality optical performance. In one exemplary embodiment, the projector lens is a five-element module containing five individual lenses as set forth in the table provided further below. In an alternative embodiment, a four-element projector lens can be obtained by omitting the fifth lens (lens5) from referenced five-element projector lens. The scale ofFIG.1is accurate in the sense that the projector lens160, and its individual lenses, each have a lateral dimension (e.g. parallel to the x-axis, or parallel to the y-axis, or along a diagonal of the spatial light modulator150) that is substantially smaller than a corresponding lateral dimension of the spatial light modulator150. This is made possible by the fact that the output illumination beam172is a converging beam. For example, the lateral dimension of the projector lens160, and/or one or more of its individual lenses, may be no more than 30% or 50% or 70% of the corresponding lateral dimension of the spatial light modulator150. In an exemplary embodiment based on the projector lens table provided further below, the lateral dimension of the (five-element) projector lens is 2.88 mm and the length of the diagonal of the 5:4 spatial light modulator is 6 mm, for a percentage of 48%. The lateral dimension of the individual lens closest to the spatial light modulator is 2.8 mm, for a percentage of 47%.

The purpose of the illuminator140is to illuminate the active area of the spatial light modulator150so that an optical image or pattern can be produced. In many, but not all, cases, it is desirable for the output illumination beam172to be a converging light beam at the place where it impinges upon the spatial light modulator150, as suggested by light ray144. It is also often desirable for the output illumination beam172to be relatively uniform in brightness over the active area of the spatial light modulator150. Furthermore, it is often desirable to accomplish this illumination in a package that is physically small, and that uses high efficiency, high brightness light sources in order to keep heat generation low and device size small. A logical option for high efficiency, high brightness sources is one or more discrete, solid state light sources such as light emitting diodes (LEDs). However, other suitable light sources can also be used.

In this regard, “light emitting diode” or “LED” refers to a diode that emits light, whether visible, ultraviolet, or infrared, although in most practical embodiments the emitted light will have a peak wavelength in the visible spectrum, e.g. from about 400 to 700 nm. The term LED includes incoherent encased or encapsulated semiconductor devices marketed as “LEDs”, whether of the conventional or super radiant variety, as well as coherent semiconductor devices such as laser diodes, including but not limited to vertical cavity surface emitting lasers (VCSELs). An “LED die” is an LED in its most basic form, i.e., in the form of an individual component or chip made by semiconductor processing procedures. For example, the LED die may be formed from a combination of one or more Group III elements and of one or more Group V elements (III-V semiconductor). The component or chip can include electrical contacts suitable for application of power to energize the device. Examples include wire bonding, tape automated bonding (TAB), or flip-chip bonding. The individual layers and other functional elements of the component or chip are typically formed on the wafer scale, and the finished wafer can then be diced into individual piece parts to yield a multiplicity of LED dies. The LED die may be configured for surface mount, chip-on-board, or other known mounting configurations. Some packaged LEDs are made by forming a polymer encapsulant over an LED die and an associated reflector cup. Some packaged LEDs also include one or more phosphor materials that are excited by an ultraviolet or short wavelength visible LED die, and fluoresce at one or more wavelengths in the visible spectrum. An “LED” for purposes of this application should also be considered to include organic light emitting diodes, commonly referred to as OLEDs.

At the heart of the illuminator140is a light source120, which may include one or more LEDs, including in some cases one or more laser diodes. Several such LEDs can be combined to produce a desired spectral distribution of light. For example, the outputs of red-, green-, and blue-emitting LEDs may be combined to provide nominally white light, or white-emitting LEDs may be used instead or additionally. Alternatively, one or more LEDs of a specific non-white color may be used to produce colored (non-white) illumination, e.g., red, or green, or blue illumination, in which case the projected image will be monochrome rather than full color. In the schematic drawing ofFIG.1, the light source120is drawn as a single LED die122disposed behind a polarizer124. The light source120is assumed to emit white light, as in the case where the LED die emits blue or UV light and is covered with a thin coating (not shown) of a yellow- or white-emitting phosphor. The polarizer124, which may be any suitable polarizer including an absorbing linear polarizer, a multilayer polymeric reflective polarizer, or a laminate of a reflective polarizer and an absorbing polarizer, predominantly transmits only one polarization state of light, causing the light emitted by the source120to be polarized. In alternative embodiments, a light guide, lens, or color combiner may be inserted between the LED die122and the polarizer124to allow the LED die (or other active light source, if desired) to be mounted remotely from the polarizer. In other alternative embodiments, the polarizer124may be omitted, such that the light emitted by the source120is unpolarized. In still other cases, the polarizer124may be retained and a retarder film, such as a quarter wave retarder, may be added atop the polarizer124such that the source120emits rotationally polarized (circularly or elliptically polarized) light. However, in the particular embodiment shown inFIG.1, the light source120emits polarized light because the polarizer124is included in front of the LED die122. The arrow170schematically represents an input light beam emitted by the light source120into a reflective cavity, which is also part of the illuminator140and is discussed further below. The input light beam170is assumed to comprise broad band (and polarized) white light, and is assumed to cover a distribution of propagation directions, e.g. in a Gaussian distribution of angles centered about the optical axis142. For illustrative purposes, a representative light ray144is shown originating from the light source120and propagating through the projector110. A first ray portion144ais part of the input light beam170, and it is shown to have a polarization state P1 as a result of the polarizer124.

The input light beam170is emitted into a reflective cavity130formed by a reflective polarizer134and a reflector132. The reflector132has a high specular reflectivity (for example, in some cases at least 70%, or at least 80%, or at least 90%, or at least 95%) for light within the spectral range of the input light beam170, and for all polarization states, and in some cases it also substantially preserves the degree of the polarization of an incident light ray in the reflected ray. Any known structure or material that can supply these characteristics can be used. Metal coatings, optically enhanced metal coatings, multilayer interference structures or films, whether stacks of alternating inorganic materials, or stacks of coextruded polymers appropriately oriented or processed to provide a high reflectivity over a range of angles and over the spectral range of interest and for all polarizations, may be used for this purpose. See for example U.S. Pat. No. 5,882,774 (Jonza et al.). Alternatively, a simple metal coating such as a layer of aluminum or a layer of silver may in some cases be used for the reflector132. The reflective polarizer134provides a high reflectivity (for example, in some cases at least 70%, or at least 80%, or at least 90%) for one polarization state of light within the spectral range of interest, while also providing a low reflectivity (for example, in some cases less than 30%, or less than 20%, or less than 10%) and corresponding high transmission for light of an orthogonal polarization state in such spectral range. Any known structure or material that can supply these characteristics can be used. A wire grid polarizer, cholesteric reflective polarizer, or multilayer polymeric reflective polarizing film (comprising an interference stack of coextruded polymers appropriately oriented or processed to provide a high reflectivity for one polarization state and low reflectivity for an orthogonal polarization state) may be used for the reflective polarizer134. As a specific example, Advanced Polarizer Film (APF) available from 3M Company, St. Paul, MN may be used for the reflective polarizer134. Given an appropriate reflector132and reflective polarizer134, light of one polarization state can reflect back and forth within the reflective cavity130as illustrated by the light ray144. In the embodiment illustrated, the reflective polarizer134is oriented to provide high reflectivity for light of the first polarization state P1, and thus it will provide low reflectivity and high transmission for light of an orthogonal second polarization state P2.

In order for the polarized light emitted by the light source120to emerge from the illuminator140, the polarization state should be rotated from the first polarization state P1 (which is highly reflected by the reflective polarizer134) to the orthogonal second polarization state P2 (which is highly transmitted by the reflective polarizer134). To accomplish this rotation, we include a retarder film136in the reflective cavity130. The retarder film136may be located near, and may be substantially coextensive with, the reflector132as shown in the figure, but the retarder film136may alternatively be located elsewhere in the reflective cavity130. The amount of retardation provided by the retarder film136is selected to provide the desired rotation of the polarization state based on the number of passes of a representative light ray through the retarder film. In the depicted embodiment, light passes through the retarder film two times, which would lead one to select a (single-pass) retardance of a quarter-wave of light for the retarder film136. Thus, in reference to the light ray144, upon reflection at the reflective polarizer134, the first polarization state P1 is maintained in the reflected ray portion144b. This ray portion144bpasses through the retarder film136, and is reflected at the reflector132. The resulting reflected ray portion144cpasses again through the retarder film136, after which it acquires the second polarization state P2 (orthogonal to the state P1) as a result of the two passes through the retarder film. This ray portion144cis thus highly transmitted by the reflective polarizer134and emerges from the illuminator140as ray portion144d, still having the second polarization state P2. The ray portion144cis one of the many light rays that make up the output illumination beam172discussed above.

The reflector132and the reflective polarizer134may have the same or similar lateral dimensions, e.g., parallel to the x-axis, or parallel to the y-axis, or along a diagonal of the spatial light modulator150. Furthermore, the reflector132and reflective polarizer134may be shaped to have convex or concave curvatures as appropriate to focus the light from the light source to produce an output illumination beam172that is converging at the place where such beam impinges on the spatial light modulator150. One example of such curvatures is illustrated inFIG.1. The curvatures may be simple spherical curvatures, or they may be aspherical. The curvatures may also in some cases be anamorphic, i.e., more highly or strongly curved in one plane (e.g. the y-z plane) than in an orthogonal plane (e.g. the x-z plane). In other cases the curvatures may be rotationally symmetric about the optical axis142.

In order for light from the light source120to enter the reflective cavity130, an aperture138is provided in the reflector132. Note, however, that a light ray within the input light beam170that travels parallel to the optical axis142(as well as light rays within a narrow angular cone centered about the optical axis142) will be reflected by the reflective polarizer134but then will not be reflected by the reflector132due to the absence of the reflector132in the region of the aperture138, and such light therefore also will not become part of the output illumination beam172. This may give rise to a darkened area in the vicinity of the optical axis142in the output illumination beam172, at the position of the spatial light modulator150, such darkened area roughly analogous to a shadow of the aperture138. To reduce this shadowing effect, it is helpful to make the aperture138, as well as the light source120, as small as possible.

One or more scattering elements may also be included in the illuminator140to help further reduce the shadowing effect and make the output illumination beam172more spatially uniform. One example of such a scattering element is a grooved, textured, or otherwise roughened surface included as part of the reflective cavity130. To the extent the reflective cavity130makes uses of lenses or other optical bodies to which the various reflectors or films are applied, such optical bodies may be made by single point diamond turning, where the tooling pattern creates a series of grooves that scatter a fraction of the incident light toward the optical axis142. Another example of a scattering element is a layer of scattering material that is disposed within the reflective cavity130. Such a layer may for example be or comprise a microparticle filled adhesive layer of film, and/or a microstructured surface coated with a layer of a different refractive index. Regardless of which type of scattering element is used, it or they should substantially preserve the polarization state of light so as not to detract from the operation of the illuminator as already described. In some cases, the scattering element(s) may provide a spatially uniform scattering, i.e., a scattering that is the same as a function of the radial distance from the optical axis142. In other cases, the scattering element(s) may be designed to provide a spatially non-uniform scattering, e.g., a maximum amount of scattering at or near the optical axis142, and reduced scattering at increased radial distances from the optical axis142.

By inspection ofFIG.1, one can see that it is important to preserve the polarization state of light propagating within the reflective cavity130—except, of course, for the deliberate change in polarization caused by the retarder film136. If a lens or other optical body substantially filled the space between the reflector132and the reflective polarizer134, and if such optical body was made of a material that had a residual optical birefringence, such residual birefringence could change the polarization state of a given light ray as it traversed the reflective cavity130, such that, for example, the ray portion144awas not substantially reflected at the reflective polarizer134, or the ray portion144cwas not substantially transmitted at the reflective polarizer134. For this reason, it is desirable to substantially fill the volume of the reflective cavity130with a material or medium having little or no birefringence so that proper operation of the illuminator140can be maintained. In one class of examples, referred to herein as “solid cavity”, a majority of the cavity volume, and in some cases substantially the entire cavity volume, comprises one or more solid light-transmissive materials having very low birefringence, such as PMMA, cyclic polyolefins, inorganic glass, or silicones. In another class of examples, referred to herein as “hollow cavity”, a majority of the cavity volume, and in some cases substantially the entire cavity volume, comprises air or vacuum. Some advantages of the hollow cavity approach include no measurable birefringence, reduced weight, and improved masking of the shadowing effect, as discussed further below.

In the embodiment ofFIG.1, the aperture138is provided not only in the reflector132but also in the retarder film136. Because of this, as the light ray144travels from the light source120to the spatial light modulator150, it passes through the retarder film136exactly two times. In an alternative embodiment, the aperture in the retarder film136could be omitted, such that the retarder film136was intact and continuous, with no central hole. In that case, the light ray144would pass through the retarder film136once in the ray portion144a, and once again in the ray portion144band again in the ray portion144c, for a total of three passes through the retarder film136. The performance of such an embodiment may not be optimal but may be adequate for some applications. The single pass retardation of the retarder film136in such embodiments would be selected to provide the desired rotation of the polarization state based on three passes of a representative light ray through the retarder film, which would give a result somewhat less than a quarter-wave of light.

FIG.2is taken from a different perspective to illustrate possible outer boundaries or shapes of the reflective cavity130and its constituent parts. In particular,FIG.2is a front view of a reflector232which may be the same as or similar to reflector132, the reflector232being a part of a projector that may be the same as or similar to the projector110already described. An aperture238is provided in the reflector232, the aperture238likewise being the same as or similar to the aperture138inFIG.1. From the perspective ofFIG.2, the entire aperture can clearly be seen. The aperture238is typically but not necessarily centered on an optical axis242of the reflective cavity. In some cases, the reflector232may have a round (circular) outer boundary or edge232aas would be typical for a conventional round lens. In other cases, the projector size and weight may be decreased by truncating the reflector232to have a reduced boundary or edge232b. The boundary232bdrawn inFIG.2is a rectangle whose aspect ratio is about 5:4. This 5:4 aspect ratio is intended to substantially match the aspect ratio of the active area of the spatial light modulator150for efficient matching of the illumination optics to the spatial light modulator, although the actual length and width dimensions of the reflector232may be somewhat larger than those of the spatial light modulator. Note that although only the reflector232is depicted inFIG.2, the other chief components of the reflective cavity130, such as the reflective polarizer134and the retarder film136, may be provided with boundaries or edges that match or substantially match that of the reflector232, e.g., edge232aor edge232b.

FIG.3schematically illustrates a front view of a spatial light modulator350, which may be the same as or similar to the spatial light modulator150inFIG.1. Alternatively, the spatial light modulator350may represent a reflective-type spatial light modulator, as discussed in some of the embodiments below. The active area of the modulator350is filled with rows and columns of individual pixel elements352, only some of the rows and columns being shown inFIG.3for simplicity. The length and width of the active area is typically substantially rectangular, and the rectangle often has a length-to-width aspect ratio of 5:4. Of course, other aspect ratios may be used, but it is sometimes desirable to match the relative shape (e.g. as characterized by an aspect ratio) of the illumination optics to that of the spatial light modulator. An electronic controller couples to the spatial light modulator350and controls the states of all of the individual pixels, as explained above. The spatial light modulator350may be configured such that the difference between “on” pixels and “off” pixels is given by a rotation in the polarization of the outgoing light ray, and/or an angular deflection of the outgoing light ray.

FIG.4illustrates a portion of a compact projection system including a compact illuminator, the illuminator comprising a “solid cavity” type reflective cavity as explained above. Thus, inFIG.4, an illuminator440includes a light source420and a reflective cavity430. The light source420includes an LED die422and a polarizer424, but the light source420may alternatively be or comprise any of the variations discussed above with regard to light source120. The illuminator440and light source420, as well as a spatial light modulator450(having pixel elements452), are arranged along an optical axis442. The light source injects an input light beam470into the reflective cavity430, which is defined by a reflective polarizer434and a reflector432. Disposed within the reflective cavity is a retarder film436. The retarder film436is located adjacent the reflector432, and an aperture438is provided in both the reflector and the retarder film. Light from the polarized light source420exits the reflective cavity430as output illumination beam472, which illuminates the active area of the spatial light modulator450. The spatial light modulator450converts the beam472into a transmitted patterned light beam474, the beam474containing image-wise or spatially patterned information. All of the foregoing elements of the embodiment ofFIG.4may be the same as or similar to the corresponding elements discussed above in connection withFIG.1, and the embodiment ofFIG.4may be used in a projector the same as or similar to that ofFIG.1. Similarly, the manner in which polarized light from the light source420reflects back and forth within the cavity430, and its polarization rotated to allow it to emerge as output illumination beam472, is the same as or similar to the operation of the illuminator140, and need not be repeated here.

However, the particular construction of the reflective cavity430is worthy of some additional observations. The space between the reflector432and the reflective polarizer434defines a cavity volume, and substantially all of that cavity volume is occupied by one or more solid light-transmissive materials, in particular, a first optical lens or body431and a second optical lens or body433. The bodies431,433are cemented together along an interface435with a suitable optical adhesive or other optical bonding material. For ease of manufacture the interface435may be planar. The bodies431,433are composed of suitable very low birefringence optical materials as discussed in more detail above, and they may be composed of different such optical materials or the same optical material. In an alternative embodiment the two optical bodies431,433may be replaced with a single unitary optical body without any interface435therein but having the same outer surfaces. The optical body431has an outer curved surface431ato which the retarder film436is applied directly or by a suitable optical bonding material. The reflector432is applied atop the retarder film so that the retarder film is properly positioned between the reflector432and the reflective polarizer434. The reflective polarizer434, in turn, is applied to an outer curved surface433aof the optical body433. Central portions of the reflector432and the retarder film436are etched, cut, or otherwise omitted to define the aperture438, which is appropriately sized to the light source420. At the aperture438, the outer surface431aof the optical body431may be exposed.

FIG.5illustrates a portion of a compact projection system similar toFIG.4, but for the opposite case in which the illuminator comprises a hollow cavity type reflective cavity rather than a solid cavity. Thus, inFIG.5, an illuminator540includes a light source520and a reflective cavity530. The light source520includes an LED die522and a polarizer524, but the light source520may alternatively be or comprise any of the variations discussed above with regard to light source120. The illuminator540and light source520, as well as a spatial light modulator550(having pixel elements552), are arranged along an optical axis542. The light source injects an input light beam570into the reflective cavity530, which is defined by a reflective polarizer534and a reflector532. Disposed within the reflective cavity is a retarder film536. The retarder film536is located adjacent the reflector532, and an aperture538is provided in both the reflector and the retarder film. Light from the polarized light source520exits the reflective cavity530as output illumination beam, which illuminates the active area of the spatial light modulator550. The spatial light modulator550converts the illumination beam into a transmitted patterned light beam574, the beam574containing image-wise or spatially patterned information. All of the foregoing elements of the embodiment ofFIG.5may be the same as or similar to the corresponding elements discussed above in connection withFIG.1, and the embodiment ofFIG.5may be used in a projector the same as or similar to that ofFIG.1. Similarly, the manner in which polarized light from the light source520reflects back and forth within the cavity530, and its polarization rotated to allow it to emerge as an output illumination beam, is the same as or similar to the operation of the illuminator140, and need not be repeated here.

However, the particular construction of the reflective cavity530is worthy of some additional observations. The space between the reflector532and the reflective polarizer534defines a cavity volume, and substantially all of that cavity volume is occupied by air, or vacuum, rather than any solid light-transmissive materials. This is made possible by supporting the opposed reflectors and retarder film on the inward-facing major surfaces of two optical bodies that are spaced apart from each other. In particular, a first optical lens or body531has a curved major surface531athat faces a second optical lens or body533, and the second body533has a curved major surface533athat faces the first body531. The bodies531,533may be held firmly and stably in their relative positions by a suitable substrate or framework attached to the outer edges of the bodies. The bodies531,533may be composed of suitably transparent optical materials to allow light from the light source520to pass through the body531, and light exiting the reflective cavity530to pass through the body533. The bodies531,533may also be composed of relatively low birefringence optical materials so that the polarization state of light passing through the body531, as well as the polarization state of light passing through the body533, is not significantly rotated. But the amount of birefringence that can be tolerated in the bodies531,533is substantially greater than that of bodies431,433, due to the substantially shorter optical path lengths for light rays passing through the bodies531,533than for light rays passing through bodies431,433. This is a result of being able to design the bodies531,533to have thicknesses (the dimension measured along the z-axis) that are substantially less than the on-axis thickness of the reflective cavity530. The optical body531has an inner curved surface531ato which the reflector532is applied directly or by a suitable optical bonding material. The retarder film536is applied atop the retarder film so that the retarder film is properly positioned between the reflector532and the reflective polarizer534when the optical bodies531,533are properly mounted. The reflective polarizer534, in turn, is applied to an inner curved surface533aof the optical body533. Central portions of the reflector532and the retarder film536are etched, cut, or otherwise omitted to define the aperture538, which is appropriately sized to the light source520. At the aperture538, the inner surface531aof the optical body531may be exposed.

Some advantages of hollow cavity-type illuminators may include one or more of: reduced weight; no measurable birefringence in the reflective cavity, including no birefringence resulting from thermally induced stress, as may occur in a solid optical body; the curved surfaces531a,533acan be formed in thin substrates by microreplication, reducing stray birefringence concerns and reducing any absorptive losses; and improved masking of the shadowing effect, i.e., improved spatial uniformity of the output illumination beam, as demonstrated below in connection withFIGS.10A and10B.

FIGS.6A through6Dillustrate various views of a particular optical body637that has been found to be useful in at least some of the disclosed compact illuminators and projectors.FIG.6Ais a perspective view,FIG.6Bis a rear view,FIG.6Cis a side view, andFIG.6Dis a top view of the optical body637. TheFIGS.6A-6Dare at least approximately to scale with regard to relative lengths, widths, and thicknesses of the various illustrated features. The optical body637is composed of a first optical body631attached to a second optical body633along a planar interface635. The bodies631,633are analogous to the optical bodies432,433ofFIG.4, and those optical bodies ofFIG.4can be designed precisely as set forth here in connection with the optical body637.

The first and second optical bodies631,633are assumed to be made of the same very low birefringence optical material, in particular, annealed PMMA, which has a refractive index of about 1.49 at a visible wavelength of 550 nm. The first optical body631has an outer major convex surface631aand the second optical body633has an outer major concave surface633a, and both of these surface curvatures are oriented along the same optical axis642of the optical body637. These two surface curvatures are each also aspherical, but are rotationally symmetric about the optical axis642(ignoring the rectangular outer boundary or edge of the bodies637,631,633).

The surface631ahas a radius of curvature of 11.156 mm, a conic constant of 0.11055, and the following polynomial aspheric coefficients:4thorder aspheric coefficient: 0.00012286;6thorder aspheric coefficient: −1.3845E-06; and8thorder aspheric coefficient: 5.2850E-08,where exponential notation is used for numbers of very small magnitude. The aspheric coefficients and other information relating to the curvature of surfaces631a(and633a) is provided herein using the nomenclature of LightTools™ illumination design software.

The surface633ahas a paraxial radius of curvature of 58.562 mm, a conic constant of 29.052, and the following polynomial aspheric coefficients:4thorder aspheric coefficient: 2.2997E-05;6thorder aspheric coefficient: 1.2025E-05; and8thorder aspheric coefficient: 7.0933E-08.

The overall length (dimension along the x-axis) and width (dimension along the y-axis) of the optical body637and its component bodies631,633is 9.2 millimeters and 7.4 millimeters, respectively. The 9.2 mm length and 7.4 mm width are substantially in the proportion of 5:4. The axial thickness of the optical body637, i.e., the physical thickness (dimension along the z-axis) of the optical body637measured at the optical axis642, is 4.38 millimeters.

The performance of a compact projection system utilizing the optical body637, in an embodiment similar to that ofFIG.4, was modeled with commercial optical modeling software. Such modeling is discussed below in connection withFIGS.8and9A through9E.

FIG.7is a schematic side view of another compact projection system, this one using an illuminator having a hollow cavity type of reflective cavity similar toFIG.5. InFIG.7, a projector includes a compact illuminator740, a spatial light modulator750(having pixel elements752), and a projector lens760(a lens module having individual lenses761,762,763,764, and765). The illuminator740includes a light source720and a reflective cavity730. The light source720includes an LED die722and a polarizer724, but the light source720may alternatively be or comprise any of the variations discussed above with regard to light source120. The illuminator740and light source720, as well as the spatial light modulator750and the projector lens760, are arranged along an optical axis742. The light source injects an input light beam770into the reflective cavity730, which is defined by a reflective polarizer734and a reflector732. Disposed within the reflective cavity is a retarder film736. The retarder film736is located adjacent the reflector732, and an aperture738is provided in both the reflector and the retarder film. Light from the polarized light source720exits the reflective cavity730as output illumination beam, which illuminates the active area of the spatial light modulator750. The spatial light modulator750converts the illumination beam into a transmitted patterned light beam774, the beam774containing image-wise or spatially patterned information. All of the foregoing elements of the embodiment ofFIG.7may be the same as or similar to the corresponding elements discussed above in connection withFIGS.1and5. Similarly, the manner in which polarized light from the light source720reflects back and forth within the cavity730, and its polarization rotated to allow it to emerge as an output illumination beam, is the same as or similar to the operation of the illuminator140. In brief, referring to representative light ray744: a first ray portion744a, which is part of the input light beam770, has a polarization state P1; a second ray portion744bis generated by reflection from reflective polarizer734; a third ray portion744cis generated by reflection from reflector732, and has a rotated second polarization state P2 due to two passes of the light ray through the retarder film736; a fourth ray portion744d, which is part of the output illumination beam, also has the second polarization state P2 and impinges upon the spatial light modulator750; a fifth ray portion744e, which is spatially modulated by the modulator750as a function of whether the particular pixel752through which the beam passes is in an “on” or “off” state. If we assume the ray portion744eis passed by the modulator750, it then goes on to be captured by the projector lens760and emitted to a remote surface or user.

Similar to the embodiment ofFIG.5, the projector and illuminator ofFIG.7utilize a hollow cavity type reflective cavity730. A first optical lens or body731has a curved major surface731athat faces a second optical lens or body733, and the second body733has a curved major surface733athat faces the first body731. These bodies731,733are analogous to the optical bodies531,533described above, except the curvatures of the respective major surfaces have been changed. Relative to theFIG.5embodiment, the curvature of the surface731ahas been reduced (greater radius of curvature), and the curvature of the surface733ahas been flipped from convex to concave. In this regard, there is substantial design flexibility in selecting the curvatures of the reflectors that form the reflective cavity in the disclosed embodiments (both hollow cavity types and solid cavity types), and even non-curved or planar shapes can be used. But in many cases it is nevertheless desirable to select a set of curvatures that will produce an illumination beam that is converging at the place where it impinges upon the spatial light modulator.

As mentioned above, the performance of a compact projection system utilizing the optical body637was modeled with commercial optical modeling software. One added feature that was investigated as part of the modeling was the addition of surface roughness on one of the curved outer surfaces of the optical body, as illustrated generally inFIG.8, to introduce controlled amounts of light scattering. In that figure, an optical body837is composed of a first optical body831and a second optical body833joined together along a planar interface835, and aligned along an optical axis842. The first optical body831has an outer curved surface831a, and the second optical body833has an outer curved surface833a. For ease of illustration, a reflector, a reflective polarizer, and a retarder film are omitted fromFIG.8, but the reader will understand that such optical elements are applied to the surfaces831a,833ain the same fashion as they are applied to the respective curved surfaces431a,433aas described above, to form a reflective cavity using the optical body837. Specifically, the retarder film and reflector (with suitable apertures) are applied to the curved surface831a, and the reflective polarizer is applied to the curved surface833a. A light source820, having an LED die822and a polarizer824, injects an input light beam870into the reflective cavity, and an output illumination beam872emerges from the other side of the reflective cavity to illuminate the spatial light modulator, represented schematically inFIG.8by reference number854. Propagation of light back and forth within the reflective cavity is substantially as described inFIG.1.

The optical modeling was able to create a controlled amount of surface roughness along the curved surface831a, while otherwise maintaining the original nominal curvature of that surface. The same controlled surface roughness was also imputed to the reflector (see e.g. reflector432inFIG.4), which was assumed to be applied to such surface. The modeling assumed the curvatures, thicknesses, and material properties discussed above for the optical body637ofFIG.6. The optical modeling also assumed:the reflector (refer again to reflector432inFIG.4) had a reflectivity of 100% for all polarizations of light;the reflective polarizer (refer e.g. to reflective polarizer434inFIG.4) had a 100% reflectivity for a first polarization state and 0% reflectivity (100% transmission) for an orthogonal second polarization state;the size of the aperture (refer e.g. to aperture438inFIG.4) was 0.3 by 0.5 millimeters;a spatial light modulator having a 5:4 length-to-width aspect ratio and diagonal measuring 6.0 millimeters;a projector lens module that included five individual lenses arranged in series as shown in the following table, where lens1refers to the individual lens that is farthest from the spatial light modulator and lens5refers to the individual lens that is closest to the spatial light modulator, where a negative radius (R1, R2) denotes a concave curvature, a positive radius denotes a convex curvature, CT denotes center thickness, RICH denotes R1 center height, and DIA denotes the lens diameter:

5-element Projector Lens DetailsLensMaterialR1  (mm)R2  (mm)CT  (mm)R1CH  (mm)DIA  (mm)1LAFN212.5732−8.09980.67.87382.82SF5−9.5469−2.4540.557.07382.553SF27.6121−2.85150.256.22382.114NBFD32.85155.3930.755.97382.065SF5−26.82315.8940.54.3552.88
Note from the table that the overall lateral dimension (diameter) of the projector lens is only 2.88 millimeters, and the diameter of the individual lens that is nearest the spatial light modulator (lens1) is only 2.8 mm.

The optical modeling simulated the distribution of light produced by the output illumination beam as imaged by the projector lens onto a far-field detector plane, and calculated the brightness or intensity (irradiance) of that far field image as a function of position. The modeling was repeated for different amounts of surface roughness on the curved surface831a, and the results are shown inFIGS.9Athrough9E. InFIGS.9A,9B,9C,9D, and9E, surface roughnesses corresponding to Gaussian diffusion angles of 0.01 degrees, 0.1 degrees, 1 degree, 2 degrees, and 4 degrees respectively were assumed. In the figures, the solid curves902a,902b,902c,902d, and902erepresent the calculated irradiance-versus-position curves along the horizontal or x-axis in the far-field plane, and the dashed curves904a,904b,904c,904d, and904erepresent the calculated irradiance-versus-position curves along the vertical or y-axis in the far-field plane. Inspection and comparison ofFIGS.9A through9Econfirms that increased amounts of surface roughness and light scattering yield a more uniform irradiance distribution and less pronounced dark spot or shadow in the center of the image.

The optical modeling software was then used again to establish a comparison between a solid cavity type illuminator and a hollow cavity type illuminator. The results ofFIGS.9A through9Eall assume a solid cavity type illuminator. We simulated a hollow cavity type illuminator by programming the modeling software to replace all of the annealed PMMA material within the reflective cavity with air (refractive index=1), but keeping everything else including the curvatures, distances, reflectivities, and so forth the same. This comparison was done for the case of a surface roughness corresponding to a Gaussian diffusion angle of 1 degree. The results for the solid cavity type system were shown inFIG.9C, and are reproduced inFIG.10Afor ease of comparison. The results for the corresponding hollow cavity type system are shown inFIG.10B, where solid curve1002brepresents the calculated irradiance-versus-position curves along the horizontal or x-axis in the far-field plane, and the dashed curve1004brepresents the calculated irradiance-versus-position curves along the vertical or y-axis in the far-field plane. Comparison ofFIGS.10A and10Bconfirm the conclusion that a hollow cavity design for the compact illuminator provides improved masking of the shadowing effect and improved spatial uniformity of the output illumination beam.

Turning now toFIG.11, we see there a different type of compact illuminator and projector1110. Rather than using a reflective cavity configuration as depicted inFIG.1, the projector1110uses a polarizing beamsplitter1180, and the beamsplitter uses opposed prisms of substantially different sizes. The projector also comprises a light source1120, which includes an LED die1122and polarizer1124, a spatial light modulator1150(seeFIG.11A), which includes pixel elements1152, and projector lens1160, which includes individual lenses1161,1162,1163,1164. The light source, spatial light modulator, and projector lens may be the same as or similar to the various light sources, spatial light modulators, and projectors discussed in the preceding embodiments, except that the spatial light modulator in the projector1110is designed to operate in reflection rather than in transmission. As a result, the spatial light modulator1150may for example be or comprise a Liquid Crystal on Silicon (LCoS) device. Such devices may be flat (as illustrated schematically), or they may include a curved reflector array that is curved in one or more axes.

The light source1120emits a polarized input light beam1170into the beamsplitter1180towards an obliquely disposed reflective polarizer1184. The reflective polarizer1184may be the same as or similar to the reflective polarizers discussed in the preceding embodiments, except that the reflective polarizer1184may if desired by optimized for oblique angle performance and in an immersed configuration (surrounded by solid light-transmissive optical materials such as glass or plastic). The reflective polarizer is sandwiched between two opposed prismatic bodies to form the beamsplitter1180. A first such prismatic body1190contains two facets1192a,1192bwhich define a relatively small prism1192. The input light beam1170enters the beamsplitter1180through the facet1192a, and spatially patterned light from the spatial light modulator (as explained below) exits the beamsplitter through the facet1192b. For size comparison purposes, the boundaries of the small prism1192can be ascertained by extending the facets1192a,1192bto the reflective polarizer1184to define the labeled points c and b, respectively. A third point, a, lies at the intersection of the facets1192a,1192b, at the apex of the small prism1192. The set of points a, b, c may thus be considered to define the corners of the small prism1192.

The other prismatic body, opposite the first prismatic body1190, is a relatively larger prism1195. The corners of this prism1195are clearly seen as labeled points d, e, and f. Attached to the side surfaces of the prism1195are lenses or other optical bodies having exterior curved surfaces. In alternative embodiments, one or both of these optical bodies may be combined with the prism1195in a unitary prismatic body.

A reflector1182is applied to one of these exterior curved surfaces as shown inFIG.11, and a retarder film1186is disposed between the reflector1182and the reflective polarizer1184. The reflector1182may be the same as or similar to the reflectors132,232,432,532,732discussed above, e.g., the reflector1182may have a high specular reflectivity (for example, in some cases at least 70%, or at least 80%, or at least 90%, or at least 95%) for light within the spectral range of the input light beam1170, and for all polarization states, and in some cases it also substantially preserves the polarization state of an incident light ray in the reflected ray. The retarder film1186may be the same as or similar to the retarding films discussed in the preceding embodiments.

The light source1120in combination with the beamsplitter1180serves as an illuminator. As will be described in relation to a representative light ray1144, light from the light source1120propagates within the beamsplitter1180until it emerges as an output illumination beam1172. The output illumination beam1172illuminates the active area of the spatial light modulator1150(seeFIG.11A) so that an optical image or pattern can be produced. In many, but not all, cases, it is desirable for the output illumination beam1172to be a converging light beam at the place where it impinges on the spatial light modulator1150. It is also often desirable for the output illumination beam1172to be relatively uniform in brightness over the active area of the spatial light modulator1150.

In reference to the light ray1144, a first ray portion1144ais part of the input light beam1170, which enters the beamsplitter1180through the facet1192a. The ray portion1144ais caused by the polarizer1124to have a second polarization state P2. The reflective polarizer1184is configured and oriented to highly transmit light of the second polarization state P2, and highly reflect light of the orthogonal first polarization state P1. Therefore, upon encountering the reflective polarizer1184, the ray portion1144ais highly transmitted through the reflective polarizer1184into the prism1195to become ray portion1144b, still having the second polarization state P2. The ray then passes through the retarder film1186to become ray portion1144c, is reflected by the reflector1182to become ray portion1144d, and passes through the retarder film1186again to become ray portion1144e. As a result of the two passes through the retarder film1186, the ray portion1144ehas the first polarization state P1, orthogonal to the original second polarization state P2. Upon encountering the reflective polarizer1184, the ray portion1144eis highly reflected to become ray portion1144f, and finally emerging from the lower curved surface of the illuminator as ray portion1144g, which can be considered part of the output illumination beam1172.

The spatial light modulator1150(seeFIG.11A) is placed in the output illumination beam1172at the output of the illuminator, and it selectively reflects incident light in an image-wise fashion. For example, pixel elements1152in an “on” state may rotate the polarization state of the reflected light by 90 degrees, whereas pixel elements1152in an “off” state may produce no such polarization rotation, or vice versa. In either case, the spatial light modulator1150converts the output illumination beam1172into a reflected patterned light beam174which is transmitted through the same beamsplitter1180, through the facet1192bto the projector lens1160, as explained below. The projector lens1160then transforms the reflected patterned light beam into a projected output beam1176, analogous to the projected output beams discussed in the preceding embodiments.

One can see that, in connection with the operation of the beamsplitter1180, it is again important to preserve the polarization state of light propagating within the beamsplitter, except for the deliberate change in polarization caused by the retarder film1186. It is therefore desirable for the solid light-transmissive optical materials that make up the prisms1192,1195and other optical bodies connected thereto to be made of very low birefringence materials as explained above.

One design feature of the projector1110that facilitates miniaturization is the substantial size disparity of the prisms1192,1195. By making the prism1192substantially smaller than the other prism, the light source1120, and/or the projector lens1160, can be brought closer to the reflective polarizer1184, thus reducing the overall projector size. Note also however that the small prism1192need not be microscopic in size relative to the larger prism; instead, the small prism1192is large enough so that light that passes through the first prismatic body1190is predominantly, or mostly, also transmitted through the small prism1192. The relative sizes of the opposed prisms can be characterized in terms of their hypotenuse lengths and/or their prism heights. The hypotenuse length of the small prism1192, which we may call HL1, is the distance between the points b and c, and the hypotenuse length of the other prism1195, which we may call HL2, is the distance between the points d and f. The prism heights of the prisms1192,1195, which we may call H1 and H2, respectively, are illustrated inFIG.11as being measured relative to the reflective polarizer1184. To characterize the size disparities of the opposed prisms, we may specify that the ratio HL1/HL2 is in a range from 40% to 70%, and/or that the ratio H1/H2 is similarly in a range from 40% to 70%.

FIG.11Ais a substantial duplicate ofFIG.11, where like reference numbers designate like elements with no further need for discussion, except that the reflective spatial light modulator1150, already described above, is now shown in its proper position to intercept the output illumination beam1172. Superimposed on the figure are two rectangular reference spaces1103,1105. The first reference space1103is a rectangular space defined by the obliquely oriented reflective polarizer1184. More specifically, the reference space1103is a rectangle whose diagonal line is the reflective polarizer1184. This roughly corresponds to the rectangular space occupied by a conventional beamsplitter. On the other hand, the second reference space1105may be described as the smallest rectangular space that encompasses the optical components (exclusive of any mechanical mounting hardware or the like) of the projector. For the projector1110, those optical components are the beamsplitter1180, the light source1120, the spatial light modulator1150, and the projector lens1160.

As a result of our miniaturization efforts, several new relationships can be satisfied by the projector1110and/or other disclosed projectors.

For example, at least a portion of the light source1120, or at least a portion of the projector lens1160, are disposed within the first rectangular reference space1103. In some cases at least a portion of the light source1120and at least a portion of the projector lens1160are both disposed within the first rectangular reference space1103. In some cases, at least a portion of the light source, or at least a portion of the projector lens, but not both, are disposed within the first rectangular reference space1103. The first rectangular reference space1103may be split into two portions, along the diagonal of the reflective polarizer1184. When so split, the at least a portion of the light source1120, or the at least a portion of the projector lens1160, is disposed within one such portion of the first rectangular reference space1103. Furthermore, the at least a portion of the light source and the at least a portion of the projector lens may both be disposed within such portion of the first rectangular reference space1103. If the light source1120comprises an LED die1122, the LED die1122may be entirely disposed within the first rectangular reference space1103. If the projector lens1160comprises a plurality of individual lenses1161,1162,1163,1164, at least one of the individual lenses may be entirely disposed within the first rectangular reference space1103.

Also, the projector can be miniaturized to such an extent that the optical components of the projector (exclusive of any mechanical mounting hardware or the like) can fit within a space that is only slightly larger than the space occupied by a conventional beamsplitter for that projector. Stated differently, if A1 is the area of the first rectangular reference space1103, and A2 is the area of the second rectangular reference space1105, then the ratio of A1/A2 may be in a range from 30% to 70%, or from 40% to 70%.

The foregoing relationships relating to reference spaces, locations of elements within or outside of such spaces, comparisons of areas of such spaces, and so forth can be ascertained with reasonable accuracy by reference toFIGS.11and11Adespite the fact that these figures are schematic in nature. Although schematic, the relative sizes and positions of pertinent system components in these figures are believed to be reasonably representative of how such components would appear in an actual scale drawing. This can also be said for at leastFIGS.14,14B,15, and15Abelow. Based onFIG.11A, the ratio of the area of reference space1103to the area of reference space1105(A1/A2) is at least 60%.

FIGS.11B and11Care provided to further illustrate the passage of light through the projector1110after the output illumination beam1172is reflected by the spatial light modulator1150.FIG.11Bcovers the case of light reflected by “on” pixels of the modulator1150, whereasFIG.11Ccovers the case of light reflected by “off” pixels of the modulator. Otherwise, in these figures, like reference numbers to those inFIGS.11and11Arefer to like elements, and need no further explanation.

InFIG.11B, light from the output illumination beam1172is reflected by an on-axis pixel1152aand by an off-axis pixel1152b, both of these pixels assumed to be in an “on” state such that the reflected light has a rotated polarization, i.e., the reflected light has the second polarization state P2 rather than state P1. Light of this polarization state P2 is highly transmitted by the reflective polarizer1184. Thus, the light reflected by the “on” pixels is transmitted through the reflective polarizer1184and exits the beamsplitter1180through the facet1192bof the prism1192, and is collected by the projector lens1160to ultimately form the projected output beam1176.

On the other hand, inFIG.11C, light from the output illumination beam1172is again reflected by the on-axis pixel1152aand by the off-axis pixel1152b, but now these pixels are assumed to be in an “off” state such that the reflected light does not have a rotated polarization, i.e., the reflected light has the first polarization state P1. Light of this polarization state P1 is highly reflected by the reflective polarizer1184. Thus, the light reflected by the “off” pixels is reflected by the reflective polarizer1184and thereafter reflected by the reflector1182towards the left side of the beamsplitter1180, where such rays may be absorbed or otherwise lost. Light reflected by the “off” pixels thus do not get collected by the projector lens1160, and do not substantially contribute to the projected output beam1176.

FIGS.12and13represent modifications to the projector1110, where the first prismatic body1190is replaced by alternative prismatic bodies. These replacements do not substantially change the manner in which light propagates between the light source, spatial light modulator, and projection lens, and thus that description will not be repeated for these figures.

InFIG.12, a projector1210uses a polarizing beamsplitter1280having opposed prisms of substantially different sizes. The projector1210also comprises a light source1220, a spatial light modulator1250which includes pixel elements1252, and a projector lens1260which includes individual lenses, and all of these elements may be the same as or similar to corresponding elements in the projector1110.

The beamsplitter1280includes an obliquely disposed reflective polarizer1284sandwiched between two opposed prismatic bodies: a first such prismatic body1290contains two facets1292a,1292bwhich define a relatively small prism1292, and the other prismatic body is a relatively larger prism1295. Polarized light from the light source1220enters the beamsplitter1280through the facet1292a, and spatially patterned light from the spatial light modulator1250exits the beamsplitter through the facet1292b. The boundaries of the small prism1292can be ascertained by extending the facets1292a,1292bto the reflective polarizer1284to define the labeled points c and b, respectively, and a third point, a, lies at the intersection of the facets1292a,1292b. The corners of the larger prism1295are clearly seen as labeled points d, e, and f. Attached to the side surfaces of the prism1295are lenses or other optical bodies having exterior curved surfaces. A reflector1282is applied to one of these exterior curved surfaces, and a retarder film1286is disposed between the reflector1282and the reflective polarizer1284. The reflector1282and retarder film1286may be the same as or similar to corresponding elements of the projector1110. The light source1220in combination with the beamsplitter1280serves as an illuminator. Light that is reflected by “on” pixels of the spatial light modulator is transmitted through the reflective polarizer1284and exits the beamsplitter1280through the facet1292bof the prism1292, and is collected by the projector lens1260to ultimately form the projected output beam1276.

In this embodiment, the first prismatic body1290covers only a portion of the reflective polarizer1284, and the first prismatic body1290comprises no prisms other than the prism1292. The locations of the points a, b, c, d, e, f may be substantially the same as corresponding points in the projector1110, hence, the prism dimensions H1, H2, HL1, and HL2, and their various ratios may satisfy the same conditions as discussed above.

InFIG.13, a projector1310uses a polarizing beamsplitter1380having opposed prisms of substantially different sizes. The projector1310also comprises a light source1320, a spatial light modulator1350which includes pixel elements1352, and a projector lens1360which includes individual lenses, and all of these elements may be the same as or similar to corresponding elements in the projector1110.

The beamsplitter1380includes an obliquely disposed reflective polarizer1384sandwiched between two opposed prismatic bodies: a first such prismatic body1390contains two facets1392a,1392bwhich define a relatively small prism1392, and the other prismatic body is a relatively larger prism1395. Polarized light from the light source1320enters the beamsplitter1380through the facet1392a, and spatially patterned light from the spatial light modulator1350exits the beamsplitter through the facet1392b. The boundaries of the small prism1392can be ascertained by extending the facets1392a,1392bto the reflective polarizer1384to define the labeled points c and b, respectively, and a third point, a, lies at the intersection of the facets1392a,1392b. The corners of the larger prism1395are clearly seen as labeled points d, e, and f. Attached to the side surfaces of the prism1395are lenses or other optical bodies having exterior curved surfaces. A reflector1382is applied to one of these exterior curved surfaces, and a retarder film1386is disposed between the reflector1382and the reflective polarizer1384. The reflector1382and retarder film1386may be the same as or similar to corresponding elements of the projector1110. The light source1320in combination with the beamsplitter1380serves as an illuminator.

In this embodiment, the first prismatic body1390covers substantially all of the reflective polarizer1384, and the first prismatic body1390comprises two prisms—prism390and prism396—in addition to the prism1392. The locations of the points a, b, c, d, e, f may be substantially the same as corresponding points in the projector1110, hence, the prism dimensions H1, H2, HL1, and HL2, and their various ratios may satisfy the same conditions as discussed above.

FIG.14illustrates still another compact projector1410and illuminator. This projector combines the reflective cavity configuration depicted inFIG.1with the use of a polarizing beamsplitter having opposed prisms of substantially different sizes.

In this case, a light source1420injects an input light beam into a reflective cavity1430formed by a reflector1432and a reflective polarizer1434. A retarder film1436is disposed in the cavity, and an aperture1438is provided in the reflector1432and the retarder film1436. The reflector1432, reflective polarizer1434, and retarder film1436may be applied to the outer surfaces of an optical lens or body1431as shown, and may otherwise be the same as or similar to corresponding components of the reflective cavity430inFIG.4. Light that exits the reflective cavity1430enters a polarizing beamsplitter1480.

The polarizing beamsplitter1480includes an obliquely disposed reflective polarizer1484sandwiched between two opposed prismatic bodies: a first such prismatic body1490contains two facets1492a,1492bwhich define a relatively small prism1492, and the other prismatic body is a relatively larger prism1495. Polarized light exiting the reflective cavity1430enters the beamsplitter1480through a facet of the prism1495, and is reflected by the reflective polarizer1484so that it exits the beamsplitter1480and impinges upon the spatial light modulator1450. Light whose polarization is rotated by “on” pixels of the spatial light modulator1450re-enter the beamsplitter1480and now pass through the reflective polarizer1484, traverse the small prism1492, and exit the beamsplitter1480by the facet1492b. The boundaries of the small prism1492can be ascertained by extending the facets1492a,1492bto the reflective polarizer1484to define the labeled points c and b, respectively, and a third point, a, lies at the intersection of the facets1492a,1492b. The corners of the larger prism1495are clearly seen as labeled points d, e, and f. Attached to the lower side surface of the prism1495is a lens or other optical body having an exterior curved surface for optional focusing or convergence of the exiting illumination beam. In this embodiment, the beamsplitter1480need not contain any retarder film or reflector other than the reflective polarizer1484.

The prisms1492,1495have respective prism heights H1 and H2 as shown, and these parameters, as well as the respective hypotenuse lengths HL1 and HL2, and their various ratios, may satisfy the same conditions discussed above.

With reference to representative light ray1444, a first ray portion1444ahas a first polarization state P1 which is substantially reflected by the reflective polarizer1434, such that the reflected ray portion1444bpasses through the retarder film1436and is reflected by the reflector1432. This reflection results in the ray portion1444cwhich passes again through the retarder film1436, thereupon acquiring the second polarization state P2 which is highly transmitted by the reflective polarizer1434. The ray portion1444cthus passes through the reflective polarizer1434to provide ray portion1444d, which enters the beamsplitter1480and is reflected by the reflective polarizer1484to produce reflected ray portion1444e. This ray exits the beamsplitter1480as ray portion1444f, reflects from an “on” pixel of the spatial light modulator1450(thus rotation the polarization state from P2 back to P1) as ray portion1444g, re-enters the beamsplitter1480as ray portion1444h(still of polarization state P1), now passes through the reflective polarizer1484, traverses the prism1492as ray portion1444i, and exits the beamsplitter1480at facet1492bon its way to the projector lens1460. Such light collected by the projector lens1460ultimately forms the projected output beam1476of the projector1410.

FIG.14Ais a magnified view of the reflector1432and retarder film1436on the outer surface1431aof the optical body1431.

FIG.14Bis a substantial duplicate ofFIG.14, where like reference numbers designate like elements with no further need for discussion, and where two rectangular reference spaces1403,1405are superimposed on the figure. A first reference space1403is a rectangular space defined by the obliquely oriented reflective polarizer1484. More specifically, the reference space1403is a rectangle whose diagonal line is the reflective polarizer1484. A second reference space1405is the smallest rectangular space that encompasses the optical components of the projector, i.e., the beamsplitter1480, the light source1420, the spatial light modulator1450, and the projector lens1460. The relationships discussed above with respect to corresponding rectangular reference spaces, in connection withFIG.11, can be seen to apply at least in part to the reference spaces1403,1405of the projector1410also. In particular, the ratio of the area of reference space1403to the area of reference space1405(A1/A2) is at least 45%.

The projector1510ofFIG.15is similar to that ofFIG.14insofar as it also combines the reflective cavity configuration depicted inFIG.1with the use of a polarizing beamsplitter. However, the projector1510also makes use of an unused side of the beamsplitter by adding a detector device, such that the projector1510is also capable of functioning as a camera.

A light source1520injects an input light beam into a reflective cavity1530formed by a reflector1532and a reflective polarizer1534. A retarder film1536is disposed in the cavity, and an aperture1538is provided in the reflector1532and the retarder film1536. The reflector1532, reflective polarizer1534, and retarder film1536may be applied to the outer surfaces of an optical lens or body1531as shown, and may otherwise be the same as or similar to corresponding components of the reflective cavity430inFIG.4. Light that exits the reflective cavity1530enters a polarizing beamsplitter1580.

The polarizing beamsplitter1580includes an obliquely disposed reflective polarizer1584sandwiched between two opposed prismatic bodies: a first prismatic body1590and a second prismatic body or prism1595. Polarized light exiting the reflective cavity1530enters the beamsplitter1580through a facet of the prism1595, and is reflected by the reflective polarizer1584so that it exits the beamsplitter1580and impinges upon the spatial light modulator1550. Light whose polarization is rotated by “on” pixels of the spatial light modulator1550re-enter the beamsplitter1480and now pass through the reflective polarizer1584, traverse the prismatic body1590, and exit the beamsplitter1580in a well or hole sized to fit at least a part of the projector lens1560. Attached to the lower side surface of the prism1595is a lens or other optical body having an exterior curved surface for optional focusing or convergence of the exiting illumination beam. In this embodiment, the beamsplitter1580need not contain any retarder film or reflector other than the reflective polarizer1584.

With reference to representative light ray1544, a first ray portion1544ahas a first polarization state P1 which is substantially reflected by the reflective polarizer1534, such that the reflected ray portion1544bpasses through the retarder film1536and is reflected by the reflector1532. This reflection results in the ray portion1544cwhich passes again through the retarder film1536, thereupon acquiring the second polarization state P2 which is highly transmitted by the reflective polarizer1534. The ray portion1544cthus passes through the reflective polarizer1534to provide ray portion1544d, which enters the beamsplitter1580and is reflected by the reflective polarizer1584to produce reflected ray portion1544e. This ray exits the beamsplitter1580as ray portion1544f, reflects from an “on” pixel of the spatial light modulator1550(thus rotation the polarization state from P2 back to P1) as ray portion1544g, re-enters the beamsplitter1580as ray portion1544h(still of polarization state P1), now passes through the reflective polarizer1584, traverses the prismatic body1590as ray portion1544i, and exits the beamsplitter1580on its way to the projector lens1560. Such light collected by the projector lens1560ultimately forms a projected output beam of the projector1510.

Incoming light ray1545represents light originating from a body outside of the projector, but passing through the projector lens1545. A first ray portion1545aenters the projector lens1560, exits the lens1560as ray portion1545b, and enters the beamsplitter1580as ray portion1545c. Assuming the ray portion1545awas originally unpolarized, the ray portion1545cwill also be unpolarized, and will contain both components of the first polarization state P1 and of the second polarization state P2 as shown. When the ray portion1545cencounters the reflective polarizer1584, the P1 polarization state will be transmitted into a ray portion1545d, and the P2 polarization state will be reflected into a ray portion1545e, which then exits the beamsplitter1580at an unused facet thereof, where a detector device1596has been placed. The detector device1596is shown as having an array of detector elements, such as in a charge-coupled device (CCD) detector array, but other known detector arrays or even an individual detector element may also be used. By including the detector device1596in the projector1510, the same projector lens1560that is used to project an image to a remote location can also be used to collect light from the remote location and capture that light as a camera image or the like. Such a detector device can also be incorporated into the projector1410ofFIG.14by placing the same or similar array at the unused facet1492a, or at a spaced distance from such facet1492awith one or more lenses or other optical elements disposed therebetween.

FIG.15Ais a substantial duplicate ofFIG.15, where like reference numbers designate like elements with no further need for discussion, and where two rectangular reference spaces1503,1505are superimposed on the figure. A first reference space1503is a rectangular space defined by the obliquely oriented reflective polarizer1584. More specifically, the reference space1503is a rectangle whose diagonal line is the reflective polarizer1584. A second reference space1505is the smallest rectangular space that encompasses the optical components of the projector, namely, the beamsplitter1580, the light source1520, the spatial light modulator1550, the projector lens1560, and the detector device1596. The relationships discussed above with respect to corresponding rectangular reference spaces, in connection withFIG.11, can be seen to apply at least in part to the reference spaces1503,1505of the projector1510also. In particular, the ratio of the area of reference space1503to the area of reference space1505(A1/A2) is at least 40%.

FIG.16schematically illustrates still another projector and illumination system. The projector1610requires no reflective cavity or beamsplitter. Rather, light from a light source1620, as represented by ray portion1644aof a representative light ray1644, is simply collected by a pair of lenses L1, L2, although more or fewer than two lenses can be used. The lenses focus the light to produce a converging output illumination beam, represented by ray portion1644b. This beam impinges upon a transmissive spatial light modulator1650, producing a spatially patterned beam as represented by ray portion1644c. The spatially patterned beam is then collected and projected to a remote location by a projector lens1660. As a result of the converging illumination beam, the projector lens1660, or at least one of its individual component lenses, may have a maximum lateral dimension LD1 (e.g. as measured along the x-axis, or along the y-axis, or along a diagonal of the spatial light modulator1650) that is less than the corresponding lateral dimension LD2 of the spatial light modulator1650, or that alternatively satisfies the relationship 30%<LD1/LD2<70%

Unless otherwise indicated, all numbers expressing quantities, measurement of properties, and so forth 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 specification and claims are approximations that can vary depending on the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present application. Not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, to the extent any numerical values are set forth in specific examples described herein, they are reported as precisely as reasonably possible. Any numerical value, however, may well contain errors associated with testing or measurement limitations.

The following are embodiments of the present invention.

Embodiment 1 is a compact projector, comprising: a beamsplitter comprising a reflective polarizer, the reflective polarizer obliquely disposed to define a diagonal of a first rectangular reference space; a light source disposed proximate the reflective polarizer, the light source configured to emit an input light beam towards the reflective polarizer; a spatial light modulator disposed to receive an output illumination beam derived from the input light beam, the spatial light modulator adapted to selectively reflect the output illumination beam to provide a patterned light beam; and a projector lens adapted to receive the patterned light beam; wherein the beamsplitter, the light source, the spatial light modulator, and the projector lens are encompassed by a second rectangular reference space; and wherein the first rectangular reference space has an area A1 and the second rectangular reference space has an area A2, and wherein 30%<A1/A2<70%.

Embodiment 2 is the projector of embodiment 1, wherein 40%<A1/A2<70%.

Embodiment 3 is the projector of embodiment 1, wherein the beamsplitter comprises a first prism and a second prism disposed on opposite sides of the reflective polarizer.

Embodiment 4 is the projector of embodiment 3, wherein the first and second prisms have respective first and second hypotenuse lengths HL1 and HL2, and wherein 40%<HL1/HL2<70%.

Embodiment 5 is the projector of embodiment 3, wherein the first and second prisms have respective first and second prism heights H1 and H2, and wherein 40%<H1/H2<70%.

Embodiment 6 is the projector of embodiment 1, wherein the projector lens has a maximum lateral dimension LD1 and the spatial light modulator has a maximum lateral dimension LD2, and wherein LD1 is less than LD2.

Embodiment 7 is the projector of embodiment 6, wherein 30%<LD1/LD2<70%.

Embodiment 8 is the projector of embodiment 1, wherein the light source comprises an LED die and a polarizer, and wherein the input light beam is polarized.

Embodiment 9 is the projector of embodiment 1, wherein the projector further comprises a detector to receive light originating from a body outside of the projector through the projector lens.

Embodiment 10 is a compact projector, comprising: a reflective polarizer obliquely disposed to define a diagonal of a first rectangular reference space; a light source disposed proximate the reflective polarizer, the light source configured to emit an input light beam towards the reflective polarizer; a spatial light modulator disposed to receive an output illumination beam derived from the input light beam, the spatial light modulator adapted to selectively reflect the output illumination beam to provide a patterned light beam; a projector lens adapted to receive the patterned light beam; wherein at least a portion of the light source, or at least a portion of the projector lens, is disposed within the first rectangular reference space.

Embodiment 11 is the projector of embodiment 10, wherein the at least a portion of the light source and the at least a portion of the projector lens are both disposed within the first rectangular reference space.

Embodiment 12 is the projector of embodiment 10, wherein only one of the at least a portion of the light source and the at least a portion of the projector lens is disposed within the first rectangular reference space.

Embodiment 13 is the projector of embodiment 11, wherein the reflective polarizer divides the first rectangular reference space into a first portion and a second portion, and wherein the at least a portion of the light source, or the at least a portion of the projector lens, is disposed within the first portion of the first rectangular reference space.

Embodiment 14 is the projector of embodiment 13, wherein the at least a portion of the light source and the at least a portion of the projector lens are both disposed within the first portion of the first rectangular reference space.

Embodiment 15 is the projector of embodiment 10, wherein the light source comprises an LED die, and wherein the LED die is entirely disposed within the first rectangular reference space.

Embodiment 16 is the projector of embodiment 10, wherein the projector lens comprises a plurality of individual lenses in series, and wherein at least one of the individual lenses is entirely disposed within the first rectangular reference space.

Embodiment 17 is the projector of embodiment 10, wherein the reflective polarizer is part of a beamsplitter that also includes a first and second prism disposed on opposite sides of the reflective polarizer.

Embodiment 18 is the projector of embodiment 17, wherein the first and second prisms have respective first and second hypotenuse lengths HL1 and HL2, and wherein 40%<HL1/HL2<70%.

Embodiment 19 is the projector of embodiment 17, wherein the first and second prisms have respective first and second prism heights H1 and H2, and wherein 40%<H1/H2<70%.

Embodiment 20 is the projector of embodiment 10, wherein the projector lens has a maximum lateral dimension LD1 and the spatial light modulator has a maximum lateral dimension LD2, and wherein LD1 is less than LD2.

Embodiment 21 is the projector of embodiment 20, wherein 30%<LD1/LD2<70%.

Embodiment 22 is the projector of embodiment 10, wherein the projector further comprises a detector to receive light originating from a body outside of the projector through the projector lens.

Embodiment 23 is a polarizing beamsplitter, comprising: a first prismatic body comprising a first prism; a second prismatic body comprising a second prism; and a reflective polarizer sandwiched between the first and second prismatic bodies; wherein the first prism is substantially smaller than the second prism.

Embodiment 24 is the beamsplitter of embodiment 23, wherein the first and second prisms have respective first and second hypotenuse lengths HL1 and HL2, and wherein 40%<HL1/HL2<70%. Embodiment 25 is the beamsplitter of embodiment 23, wherein the first and second prisms have respective first and second prism heights H1 and H2, and wherein 40%<H1/H2<70%.

Embodiment 26 is the beamsplitter of embodiment 23, wherein the beamsplitter is configured such that light that passes through the first prismatic body passes predominantly through the first prism.

Embodiment 27 is the beamsplitter of embodiment 26, wherein the reflective polarizer comprises a first major surface facing the first prismatic body, and wherein the first prismatic body covers most of the first major surface.

Embodiment 28 is the beamsplitter of embodiment 27, wherein the first prismatic body covers substantially all of the first major surface.

Embodiment 29 is the beamsplitter of embodiment 23, wherein the first prismatic body comprises at least one prism other than the first prism.

Embodiment 30 is the beamsplitter of embodiment 23, wherein the first prismatic body comprises no prisms other than the first prism.

Embodiment 31 is a compact polarized illuminator, comprising: a reflector; a reflective polarizer disposed to form a reflective cavity with the reflector; a retarder film disposed within the reflective cavity; and a light source disposed to emit a polarized input light beam into the reflective cavity through an aperture in the reflector; wherein the reflector, the reflective polarizer, and the retarder film are configured to produce an output illumination beam from the input light beam, and wherein the output illumination beam is polarized.

Embodiment 32 is the illuminator of embodiment 31, wherein at least one of the reflector and the reflective polarizer is curved, and wherein the output illumination beam is converging.

Embodiment 33 is the illuminator of embodiment 31, wherein light follows a light path from the light source to the output illumination beam that includes passing through the aperture, reflecting from the reflective polarizer, reflecting from the reflector, passing through the reflective polarizer, and passing at least two times through the retarder film.

Embodiment 34 is the illuminator of embodiment 31, wherein the reflective cavity defines a cavity volume, and a majority of the cavity volume comprises at least one solid light-transmissive material.

Embodiment 35 is the illuminator of embodiment 31, wherein the reflective cavity defines a cavity volume, and a majority of the cavity volume comprises air or vacuum.

Embodiment 36 is the illuminator of embodiment 31, wherein the retarder film is proximate the reflector, and the aperture is also in the retarder film.

Embodiment 37 is the illuminator of embodiment 31, wherein the illuminator further comprises a scattering element to make the output illumination beam more spatially uniform.

Embodiment 38 is the illuminator of embodiment 37, wherein the scattering element comprises a roughened surface, and the roughened surface is part of the reflective cavity.

Embodiment 39 is the illuminator of embodiment 37, wherein the scattering element comprises a layer of scattering material within the reflective cavity.

Embodiment 40 is the illuminator of embodiment 31, wherein the light source comprises an LED and a polarizer.

Embodiment 41 is a compact polarized illuminator, comprising: a reflector; a reflective polarizer disposed obliquely relative to the reflector; a retarder film disposed between the reflector and the reflective polarizer; and a light source disposed to emit an input light beam of a first polarization state through the reflective polarizer towards the reflector; wherein the reflector, the reflective polarizer, and the retarder film are configured to produce an output illumination beam from the input light beam, and wherein the output illumination beam has a second polarization state orthogonal to the first polarization state.

Embodiment 42 is the illuminator of embodiment 41, wherein the reflective polarizer is part of a beamsplitter that also includes a first and second prism disposed on opposite sides of the reflective polarizer.

Embodiment 43 is the illuminator of embodiment 42, wherein the first and second prisms have respective first and second hypotenuse lengths HL1 and HL2, and wherein 40%<HL1/HL2<70%.

Embodiment 44 is the illuminator of embodiment 42, wherein the first and second prisms have respective first and second prism heights H1 and H2, and wherein 40%<H1/H2<70%.

Embodiment 45 is a projector, comprising: the polarized illuminator of embodiment 31; a spatial light modulator disposed to intercept the output illumination beam so as to produce a spatially patterned beam; and a projector lens to receive the spatially patterned beam.

Embodiment 46 is the projector of embodiment 45, wherein the spatial light modulator is a transmissive spatial light modulator.

Embodiment 47 is the projector of embodiment 45, wherein the spatial light modulator is a reflective spatial light modulator.

Embodiment 48 is the projector of embodiment 45, wherein the projector lens has a maximum lateral dimension LD1 and the spatial light modulator has a maximum lateral dimension LD2, and wherein LD1 is less than LD2.

Embodiment 49 is the projector of embodiment 45, wherein the projector further comprises a detector to receive light originating from a body outside of the projector through the projector lens.

Embodiment 50 is a projector, comprising: the polarized illuminator of embodiment 41; a spatial light modulator disposed to intercept the output illumination beam so as to produce a spatially patterned beam; and a projector lens to receive the spatially patterned beam.

Embodiment 51 is the projector of embodiment 50, wherein the spatial light modulator is a reflective spatial light modulator.

Embodiment 52 is the projector of embodiment 50, wherein the projector lens has a maximum lateral dimension LD1 and the spatial light modulator has a maximum lateral dimension LD2, and wherein LD1 is less than LD2.

Embodiment 53 is the projector of embodiment 50, wherein the projector further comprises a detector to receive light originating from a body outside of the projector through the projector lens.

Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the spirit and scope of this invention, and it should be understood that this invention is not limited to the illustrative embodiments set forth herein. The reader should assume that features of one disclosed embodiment can also be applied to all other disclosed embodiments unless otherwise indicated. It should also be understood that all U.S. patents, patent application publications, and other patent and non-patent documents referred to herein are incorporated by reference, to the extent they do not contradict the foregoing disclosure.