EP4702399A1 - Combined fourier filter for projector apertures - Google Patents

Abstract

Combined Fourier filters for projection lens assemblies. One embodiment provides a projection lens assembly comprising lens configured to spatially Fourier transform tri-color light from a modulator onto a Fourier plane, and an optical filter disposed at the Fourier plane and divided into multiple regions. At least a first region of the optical filter is substantially transparent to the tri-color light and at least a second region of the optical filter is substantially opaque to at least one wavelength of the tri-color light while being substantially transparent to at least one other wavelength of the tri-color light.

Description

COMBINED FOURIER FILTER FOR PROJECTOR APERTURES

BACKGROUND

1. Cross-Reference to Related Applications

[0001] This application claims the benefit of priority from U.S. Provisional Application No. 63/499,102, filed on 28 April 2023, which is incorporated by reference herein in its entirety

2. Field of the Disclosure

[0002] This application relates generally to projection systems and, particularly, to a combined Fourier filter for a projector system.

3. Description of Related Art

[0003] Digital projection systems typically utilize a light source and an optical system to project an image onto a surface or screen. The optical system includes components such as mirrors, lenses, waveguides, optical fibers, beam splitters, diffusers, spatial light modulators (SLMs), phase light modulators (PLMs), and the like. Some optical systems include a projector lens aperture. The projector lens aperture is typically a circular shape.

BRIEF SUMMARY OF THE DISCLOSURE

[0004] Contrast of a projector indicates the brightest output of the projector relative to the darkest output of the projector. Contrast ratio is a quantifiable measure of contrast, defined as a ratio of the luminance of the projector’s brightest output to the luminance of the projector’s darkest output. This definition of contrast ratio is also referred to as “static” or “native” contrast ratio.

[0005] Due to visual adaptation of the human visual system, the range of luminances detectable by a viewer corresponds to a contrast ratio of approximately 1,000,000,000:1, even though at any instant the detectable range of luminances corresponds to a contrast ratio less than this value. For example, in scotopic vision, mediated exclusively by rod cells in the human eye, the detectable contrast ratio at any instant may be as high as 1,000,000:1 for some viewers, depending on the observed scene, the user’s state of adaptation, and biological factors.

[0006] Optical filters, such as Fourier filters, may be used to increase the contrast of a projector.

Color projectors may rely on three primary colors channels (red, blue, and green). Traditionally, as each color channel has a different diffraction order, separate Fourier filters are implemented for each color channel. However, embodiments described herein provide a single Fourier filter configured to filter each color channel. For example, filters described herein may have a central region transmissive to first, second, and third diffraction orders, a first intermediate region transmissive to only first and second diffraction orders, a second intermediate region transmissive to only the first diffraction order, and an outer opaque region. The filter may be a dichroic filter, may be coated with an antireflection coating, may include several physical holes, may include holes and aperture portions of different shapes and shape placements, and the like.

[0007] Various aspects of the present disclosure relate to devices, systems, and methods for projection display. One example embodiment provides a projection lens assembly comprising a lens configured to spatially Fourier transform tri-color light from a modulator onto a Fourier plane, and an optical filter disposed at the Fourier plane and divided into multiple regions. A first region of the optical filter is substantially transparent to the tri-color light and at least a second region of the optical filter is substantially opaque to at least one wavelength of the tri-color light while being substantially transparent to at least one other wavelength of the tri-color light.

[0008] According to another example embodiment, provided is a projector comprising a light source configured to emit a tri-color light in response to an image signal, the image signal including image data, a modulator configured to receive the tri-color light from the light source and to apply a spatially-varying modulation on the tri-color light, thereby to steer the tri-color light and to generate a first steered light, and a projection lens assembly including an optical filter configured to spatially Fourier transform the plurality of color channels to generate a filtered light output. The first steered light includes at least a first color channel having a first diffraction pattern and a second color channel having a second diffraction pattern. The optical filter includes a first region configured to transmit the first color channel and block the second color channel, the first region aligned with a diffraction peak of the second diffraction pattern. The optical filter includes a second region configured to block the first color channel and the second color channel, the second region aligned with a diffraction peak of the first diffraction pattern.

[0009] According to another example embodiment, provided is a projector comprising a light source configured to emit a tri-color light in response to an image signal, the image signal including image data, a modulator configured to receive the tri-color light from the light source and to apply a spatially-varying modulation on the tri-color light, thereby to steer the tri-color light and to generate a first steered light, and a projection lens assembly including an optical filter configured to spatially Fourier transform the plurality of color channels to generate a filtered light output. The first steered light includes at least a first color channel having a first diffraction pattern and a second color channel having a second diffraction pattern. The optical filter includes a first region configured to transmit the first color channel and block the second color channel, the first region aligned with a high-contrast diffraction order of the second diffraction pattern. The optical filter includes a second region configured to block the first color channel and the second color channel, the second region aligned with a high-contrast diffraction order of the first diffraction pattern.

[0010] In this manner, various aspects of the present disclosure provide for the display of images having a high dynamic range and high resolution, and effect improvements in at least the technical fields of image projection, holography, signal processing, and the like.

DESCRIPTION OF THE DRAWINGS

[0011] These and other more detailed and specific features of various embodiments are more fully disclosed in the following description, reference being had to the accompanying drawings, in which:

[0012] FIG. 1 illustrates a block diagram of an exemplary image projector display system according to various aspects of the present disclosure;

[0013] FIG. 2 illustrates an optical configuration of an exemplary projector system according to various aspects of the present disclosure;

[0014] FIG. 3 illustrates an optical configuration of another exemplary projector system according to various aspects of the present disclosure;

[0015] FIG. 4A illustrates a plan view of an exemplary spatial light modulator for use with various aspects of the present disclosure;

[0016] FIG. 4B illustrates a cross-sectional view taken along the line II-B of FIG. 4A;

[0017] FIG. 5 illustrates a plan view of an exemplary phase light modulator for use with various aspects of the present disclosure;

[0018] FIG. 6 illustrates a functional diagram of an optical filter that improves contrast of an image generated with a spatial light modulator for use with various aspects of the present disclosure; [0019] FIG. 7A illustrates a cross-sectional side view of a Fourier filter configured to spatially filter modulated light received from a spatial light modulator, according to various aspects of the present disclosure;

[0020] FIGS. 7B-7C illustrate intensity plots of example Fraunhofer diffraction patterns.

[0021] FIGS. 8A-8B illustrate components of an example diffraction pattern from a spatial light modulator.

[0022] FIG. 9 illustrates an example diffraction pattern of a red color channel.

[0023] FIG. 10 illustrates an example diffraction pattern of a green color channel.

[0024] FIG. 11 illustrates an example diffraction pattern of a blue color channel.

[0025] FIG. 12 illustrates an exemplary projection lens according to various aspects of the present disclosure;

[0026] FIG. 13 illustrates a first optical filter according to various aspects of the present disclosure;

[0027] FIG. 14 illustrates a second optical filter according to various aspects of the present disclosure;

[0028] FIG. 15 illustrates a third optical filter according to various aspects of the present disclosure;

[0029] FIG. 16 illustrates a front view of a Fourier filter including the first optical filter, the second optical filter, and the third optical filter of FIGS. 13-15 according to various aspects of the present disclosure;

[0030] FIG. 17 illustrates a side view of the Fourier filter of FIG. 16 according to various aspects of the present disclosure;

[0031] FIG. 18 illustrates a front view of another example Fourier filter according to various aspects of the present disclosure; and

[0032] FIG. 19 illustrates a front view of another example Fourier filter according to various aspects of the present disclosure. DETAILED DESCRIPTION

[0033] This disclosure and aspects thereof can be embodied in various forms, including hardware, devices, or circuits controlled by computer-implemented methods, computer program products, computer systems and networks, user interfaces, and application programming interfaces; as well as hardware-implemented methods, signal processing circuits, memory arrays, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and the like. The foregoing summary is intended solely to give a general idea of various aspects of the present disclosure, and does not limit the scope of the disclosure in any way.

[0034] In the following description, numerous details are set forth, such as optical device configurations, timings, operations, and the like, in order to provide an understanding of one or more aspects of the present disclosure. It will be readily apparent to one skilled in the art that these specific details are merely exemplary and not intended to limit the scope of this application.

[0035] Moreover, while the present disclosure focuses mainly on examples in which the various circuits are used in digital projection systems, it will be understood that this is merely one example of an implementation. It will further be understood that the disclosed systems and methods can be used in any device in which there is a need to project light; for example, cinema, consumer, and other commercial projection systems, heads-up displays, virtual reality displays, and the like.

Projector Systems

[0036] FIG. 1 illustrates one possible embodiment of a suitable image projector display system. In the illustrated embodiment, the projector display system is constructed as a dual/multi-modulator projection system 100. The projection system 100 employs a light source 102 that supplies the projector system with a desired illumination such that a final projected image will be sufficiently bright for the intended viewers of the projected image. Light source 102 may comprise any suitable light source, such as, but not limited to, Xenon lamps, laser(s), coherent light sources, and partially- coherent light sources. The light source 102 may be a tri-colored light source that projects primary colors (e.g., red, green, and blue). Additionally, optical systems described herein may implement optical fibers to transfer light from the light source 102 to optics within the optical system. [0037] Light 104 from the light source 102 may illuminate a first modulator 106 that may, in turn, illuminate a second modulator 110 via a set of optional optical components 108. Light from the second modulator 110 may be projected by a projection lens 112 (or other suitable optical components) to form a final projected image upon a screen 114. In some instances, the projection lens 112 includes an optical filter for filtering the light from the second modulator 110, as described below in more detail. In some embodiments, additional optical components may be situated between the second modulator 110 and the projection lens 112, such as a wobulator for increasing the resolution of the image output by the second modulator 110. The first modulator 106 and the second modulator 110 may be controlled by a controller 116. The controller 116 may receive input image and/or video data and may perform certain image processing algorithms, gamut mapping algorithms or other such suitable processing upon the input image/video data and output control/data signals to the first modulator 106 and the second modulator 110 in order to achieve a desired final projected image on the screen 114. In addition, in some projector systems, it may be possible, depending on the light source, to modulate light source 102 (control line not shown) in order to achieve additional control of the image quality of the final projected image.

[0038] Light recycling module 103 is depicted in FIG. 1 as a dotted box that may be placed in the light path from the light source 102 to the first modulator 106. It may be appreciated that light recycling may be inserted into the projector system at various points in the projector system. For example, light recycling may be placed between the first and second modulators. In addition, light recycling may be placed at more than one point in the optical path of the display system.

[0039] While the embodiment of FIG. 1 is presented in the context of a dual, multi-modulation projection system, it should be appreciated that the techniques and methods of the present application will find application in single modulation, or other dual, multi-modulation display systems. For example, a dual modulation display system comprising a backlight, a first modulator (e.g., LCD or the like), and a second modulator (e.g., LCD or the like) may employ suitable optical components and image processing methods and techniques to affect the performance and efficiencies discussed herein in the context of the projection systems. If should also be appreciated that, even though FIG. 1 depicts a two-stage or dual modulator display system, the methods and techniques of the present application may also find application in a display system with only one modulator or a display system with three or more modulator (multi-modulator) display systems. The scope of the present application encompasses these various alternative embodiments. [0040] FIG. 2 illustrates an example projection system 200. The projection system 200 includes an illumination assembly 204 (e.g., illumination optics) that receives light from a fiber input 202 and feeds the light into a modulation assembly 206. The modulation assembly 206 includes a prism 208 and a modulator 210 (e.g., a reflector device). The modulator 210 may be configured as a digital light processing (DLP) device, as described below in more detail.

[0041] In some instances, the light from the fiber input 202 is a white light input, and the prism 208 is a white light prism. In such an instance, the prism 208 includes several prism pieces. For example, a spectral filter, such as a yellow notch filter, may be provided in the prism 208.

Additional pieces may function as a T1R prism. In some embodiments, the modulation assembly 206 includes three modulators 210 (e.g., 3-chip) for modulating the received white light. The prism 208 splits the white light into several color beams (e.g., three color channels), one color beam for each modulator 210. A controller (such as the controller 116) may be coupled to each modulator 210 to control modulation of each color beam. The modulators 210 then modulate their respective color beam before combining the modulated color beams in the prism 208. In other embodiments, the modulator 210 modulates the white light directly. In both embodiments, the modulation assembly 206 then relays the output beam into projection optics 214 of the projection system 200. In some embodiments, the projection optics 214 are included in a projection lens (such as the projection lens 112). In other embodiments, a portion or section of the projection optics 214 are included in the projection lens. As the color channels are modulated together as white light, each color channel included in the output beam from the modulation assembly 206 may have the same tilt angle.

[0042] In other instances, the projection system 200 includes several fiber inputs 202 from several color channels, such as a red color channel, a blue color channel, and a green color channel. In such an instance, the illustrated illumination assembly 204 receiving the fiber input 202 corresponds to only a single color channel. Several illumination assemblies 204 may be included to direct the light from the fiber inputs to the prism 208. In such an instance, the prism 208 is a color light prism that receives each fiber input 202 and redirects each color channel to a respective modulator 210. Following modulation, the modulated color channels are combined and directed towards the projection optics 214.

[0043] FIG. 3 illustrates another example projection system 300. The projection system 300 includes several independent color illumination assemblies 3004 that respectively receive a fiber input 302 for each color channel. For example, the projection system includes a first fiber input 302A associated with red light that is provided to a first illumination assembly 304A. A second fiber input 302B is associated with blue light that is provided to a second illumination assembly 304B. A third fiber input 302C is associated with green light that is provided to a third illumination assembly 304C. The color beam output from each illumination assembly 304 is fed into a modulation assembly 306. The modulation assembly 306 includes a nine-piece prism 308 and at least one modulator 310. The modulator 310 may be configured as a digital light processing (DLP) device, as described below in more detail. The nine-piece prism 308 relays each color beam received from each illumination assembly 304 into projection optics 314 (e.g., a projection lens). In some embodiments, each color beam is separately modulated by a respective modulator 310 prior to combination. In some instances, although each color beam is separately modulated, the color beams have the same tilt angle after modulation. The modulated color beams are then combined into the output provided to the projection optics 314. A controller (such as the controller 116) may be coupled to each modulator 210 to control modulation of each color beam. In some embodiments, the projection optics 314 are included in a projection lens. In other embodiments, a portion or section of the projection optics 314 are included in the projection lens.

Exemplary Modulation Devices

[0044] The modulators 210 and 310 (and, in some implementations, the first modulator 106 and the second modulator 110 in FIG. 1) may be configured as a DLP device. In some implementations, the modulator 210, 310 is a digital micromirror device (DMD) composed of a plurality of mirrors used to adjust the angle of incidence of light. To illustrate the effects of the angle of incidence and the DMD mirrors, FIGS. 4A-4B show an exemplary DMD 400 in accordance with various aspects of the present disclosure. In particular, FIG. 4A illustrates a plan view of the DMD 400, and FIG. 4B illustrates partial cross-sectional view of the DMD 400 taken along line I-B illustrated in FIG. 4A. The DMD 400 includes a plurality of square micromirrors 402 arranged in a two-dimensional rectangular array on a substrate 404. Each micromirror 402 may correspond to one pixel of the eventual projection image, and may be configured to tilt about a rotation axis 408, shown for one particular subset of the micromirrors 402, by electrostatic or other type of actuation. The individual micromirrors 402 have a width 412 and are arranged with gaps of width 410 therebetween. The micromirrors 402 may be formed of or coated with any highly reflective material, such as aluminum or silver, to thereby specularly reflect light. The gaps between the micromirrors 402 may be absorptive, such that input light which enters a gap is absorbed by the substrate 404.

[0045] While FIG. 4A expressly shows only some representative micromirrors 402, in practice the DMD 400 may include many more individual micromirrors in a number equal to a resolution of the projection system 200 or projection system 300. In some examples, the resolution may be 2K (2048x1080), 4K (4096x2160), 1080p (1920x1080), consumer 4K (3840x2160), and the like. Moreover, in some examples the micromirrors 402 may be rectangular and arranged in the rectangular array; hexagonal and arranged in a hexagonal array, and the like. Moreover, while FIG. 4A illustrates the rotation axis 408 extending in an oblique direction, in some implementations the rotation axis 408 may extend vertically or horizontally.

[0046] As can be seen in FIG. 4B, each micromirror 402 may be connected to the substrate 404 by a yoke 414, which is rotatably connected to the micromirror 402. The substrate 404 includes a plurality of electrodes 416. While only two electrodes 416 per micromirror 402 are visible in the cross-sectional view of FIG. 4B, each micromirror 402 may in practice include additional electrodes. While not particularly illustrated in FIG. 4B, the DMD 400 may further include spacer layers, support layers, hinge components to control the height or orientation of the micromirror 402, and the like. The substrate 404 may include electronic circuitry associated with the DMD 400, such as complementary metal-oxide semiconductor (CMOS) transistors, memory elements, and the like.

[0047] Depending on the particular operation and control of the electrodes 416, the individual micromirrors 402 may be switched between an “on” position, an “off’ position, and an unactuated or neutral position. If a micromirror 402 is in the on position, it is actuated to an angle of (for example ) -12° (that is, rotated counterclockwise by 12° relative to the neutral position) to specularly reflect input light 406 into on-state light 418. If a micromirror 402 is in the off position, it is actuated to an angle of (for example) +12° (that is, rotated clockwise by 12° relative to the neutral position) to specularly reflect the input light 406 into off-state light 420. The off-state light 420 may be directed toward a light dump that absorbs the off-state light 420. In some instances, a micromirror 402 may be unactuated and lie parallel to the substrate 404. The particular angles illustrated in FIGS. 4A-4B and described here are merely exemplary and not limiting. In some implementations, the on- and off-position angles may be between ±11 and ±13 degrees (inclusive), respectively. In other implementations, the on- and off-position angles may be between ±10 and ±18 degrees (inclusive), respectively. [0048] In some implementations, the modulator 210, 310 is a phase light modulator (PLM) configured to impart a spatially-varying phase modulation to the light. The PLM may be a reflective type, in which the PLM reflects incident light with a spatially-varying phase; alternatively, the PLM may be of a transmissive type, in which the PLM imparts a spatially-varying phase to light as it passes through the PLM. In some aspects of the present disclosure, the PLM has a liquid crystal on silicon (LCOS) architecture. In other aspects of the present disclosure, the PLM has a microelectromechanical system (MEMS) architecture.

[0049] FIG. 5 illustrates one example of the modulator 210, 310, implemented as a reflective LCOS PLM 500 and shown in a partial cross-sectional view. As illustrated in FIG. 5, the PLM 500 includes a silicon backplane 510, a first electrode layer 520, a second electrode layer 530, a liquid crystal layer 540, a cover glass 550, and spacers 560. The silicon backplane 510 includes electronic circuitry associated with the PLM 500, such as CMOS transistors and the like. The first electrode layer 520 includes an array of reflective elements 521 disposed in a transparent matrix 522. The reflective elements 521 may be formed of any highly optically reflective material, such as aluminum or silver. The transparent matrix 522 may be formed of any highly optically transmissive material, such as a transparent oxide. The second electrode layer 530 may be formed of any optically transparent electrically conductive material, such as a thin film of indium tin oxide (ITO). The second electrode layer 530 may be provided as a common electrode corresponding to a plurality of the reflective elements 521 of the first electrode layer 520. In such a configuration, each of the plurality of the reflective elements 521 will couple to the second electrode layer 530 via a respective electric field, thus dividing the PLM 500 into an array of pixel elements. Thus, individual ones (or subsets) of the plurality of the reflective elements 521 may be addressed via the electronic circuitry disposed in the silicon backplane 510, thereby to modify the state of the corresponding reflective element 521.

[0050] The liquid crystal layer 540 is disposed between the first electrode layer 520 and the second electrode layer 530, and includes a plurality of liquid crystals 541. The liquid crystals 541 are particles which exist in a phase intermediate a solid and a liquid; in other words, the liquid crystals 541 exhibit a degree of directional order, but not positional order. The direction in which the liquid crystals 541 tend to point is referred to as the “director.” The liquid crystal layer 540 modifies incident light entering from the cover glass 550 based on the birefringence An of the liquid crystals 541, which may be expressed as the difference between the refractive index in a direction parallel to the director and the refractive index in a direction perpendicular to the director. From this, the maximum optical path difference may be expressed as the birefringence multiplied by the thickness of the liquid crystal layer 540. This thickness is set by the spacer 560, which seals the PLM 500 and ensures a set distance between the cover glass 550 and the silicon backplane 510. The liquid crystals 541 generally orient themselves along electric field lines between the first electrode layer 520 and the second electrode layer 530. As illustrated in FIG. 5, the liquid crystals near the center of the PLM 500 are oriented in this manner, whereas the liquid crystals 541 near the periphery of the PLM 500 are substantially non-oriented in the absence of electric field lines. By addressing individual ones of the plurality of reflective elements 521 via a phase-drive signal, the orientation of the liquid crystals 541 may be determined on a pixel-by-pixel basis.

Example Projection Lens System and Filter

[0051] FIG. 6 provides an example optical filter 610 configured to improve contrast of an image generated with a spatial light modulator. FIG. 6 shows optical filter 610 in one use scenario, wherein optical filter 610 is implemented in a digital projector 600 to increase a contrast of an image projected by digital projector 600. In some embodiments, the digital projector 600 may be substantially similar to the projector system 100 in FIG. 1. The digital projector 600 includes a spatial light modulator (SLM) 602 that modulates input light 606 into modulator light 604 according to inputted data representative of an image to be projected by digital projector 600.

[0052] Optical filter 610 filters modulated light 604 by blocking a portion 614 of modulated light 604. Blocked portion 614 includes light that digital projector 600, in the absence of optical filter 610, would project onto screen 616 even when SLM 602 is controlled to output no light toward screen 616. Optical filter 610 outputs, as filtered light 608, a transmitted portion of modulated light 604. Digital projector 600 includes a projection lens 612 that projects filtered light 608 onto screen 616. In the absence of optical filter 610, blocked portion 614 of modulated light 604 corresponds to a lower bound of a luminous intensity of digital projector 600, and therefore determines how dark the projected image is. By blocking blocked portion 614 of modulated light 604, optical filter 610 reduces the lower bound, thereby increasing contrast of digital projector 600. The blocked portion 614 of modulated light 604 corresponds to one or more diffraction orders of modulated light 604 produced by input light 606 diffracting off of SLM 602. For example, the optical filter 610 may be configured to block diffraction orders above a set diffraction order threshold, and transmit diffraction orders below the diffraction order threshold, as described below in more detail. [0053] SLM 602 may be any type of spatial light modulator that (1) has a periodic structure acting as a diffraction grating, and (2) modulates the optical phase of input light 606 so as to steer the light between two states (e.g., ON and OFF states). In one example, SLM 602 is a DMD, such as DMD 400. In another example, SLM 602 is a reflective LCOS modulator, such as PLM 500.

[0054] FIG. 7A is a side view of one optical filter 700 configured to spatially filter modulated light 702 from the DMD 400, so as to increase the projected contrast ratio (PCR) of digital projector 600. Optical filter 700 is one example optical filter 610. In optical filter 700, DMD 400 may be replaced by another type of SLM (e.g., reflective LCOS or transmissive LC phase modulator). Optical filter 700 includes a lens 704 that spatially Fourier transforms modulated light 702 by focusing modulated light 702 onto a Fourier plane 708. Modulated light 702 is shown in FIG. 7A as a plurality of arrows, each corresponding to one diffraction order and pointing in a unique direction along which the one diffraction order propagates. In one embodiment, DMD 400 is centered on an optical axis 722 defined by lens 704, as shown in FIG. 7A. In another embodiment, DMD 400 is off-centered from optical axis 722. Lens 704 has a focal length 710, and Fourier plane 708 lies at a focal plane of lens 704. An optical filter mask 712 located at Fourier plane 708 spatially filters modulated light 702, as Fourier transformed by lens 704. The spatial Fourier transform imposed by lens 704 converts the propagation angle of each diffraction order of modulated light 702 to a corresponding spatial position on Fourier plane 708. Lens 704 thereby enables selection of desired diffraction orders, and rejection of undesired diffraction orders, by spatial filtering at Fourier plane 708. The spatial Fourier transform of modulated light 702 at Fourier plane 708 is equivalent to a Fraunhofer diffraction pattern of modulated light 702.

[0055] Optical filter mask 712 has at least one transmissive region 716 that fully or partially transmits at least one diffraction order of modulated light 702 through optical filter mask 712 as filtered light 714. In certain embodiments, optical filter mask 712 is opaque where undesired diffraction orders of modulated light 702 are incident. In some embodiments, optical filter mask 712 is opaque where optical filter mask 712 does not have a transmissive region 716. In other embodiments, optical filter mask 712 is configured to reflect, as opposed to transmit, desired diffraction orders to spatially separate desired diffraction orders from undesired diffraction orders.

[0056] In one embodiment, optical filter 700 includes a collimating lens 718 that collimates filtered light 714 into collimated light 720. Collimation lens 718 may ease integration of optical filter 700 with other optical elements or systems. For example, lens 718 may couple filtered light 714 to additional optics located after optical filter 700. Collimating lens 718 has a focal length 724, and is positioned such that a focal plane of collimated lens 718 coincides with Fourier plane 708. While focal lengths 710 and 724 are shown in FIG. 7A as being equal, focal lengths 710 and 714 may differ from each other without departing from the scope hereof. In another embodiment, optical filter 700 includes a lens similar to collimating lens 718 that optically couples filtered light 714 to additional optics located after optical filter 700.

[0057] For clarity, FIG. 7A only shows diffracted beams diffracting in one direction (e.g., the x- direction). However, DMD 400 diffracts in two dimensions, such that modulated light 702 also includes diffracted beams that have been diffracted, by DMD 400, in a second direction perpendicular to optical axis 722 (e.g., the y-direction). Each diffracted beam in a two-dimensional diffraction pattern may be labeled by a pair of integers identifying the diffraction order of the diffracted beam for each of the two dimensions. Herein, “zeroth order” refers to the one diffracted beam that has order zero in both of the two dimensions. Also without departing from the scope hereof, each arrow depicted in FIG. 7A as part of modulated light 702 may indicated a group of neighboring diffraction orders, such as the group consisting of the zeroth diffraction order and a plurality of first and higher diffraction orders.

[0058] FIGS. 7B and 7C are intensity plots of example Fraunhofer diffraction patterns 730 and 750 of ON- and OFF-modulated light from the DMD 400, respectively. Diffraction patterns 730 and 750 correspond to Fourier transforms produced by one example of lens 704 and optical filter 700 (FIG. 7 A) at Fourier plane 708. Diffraction patterns 730 and 750 are examples of diffraction patterns produced at Fourier plane 708 when optical filter 700 is implemented in a dual-modulation system.

[0059] Each of diffraction patterns 730 and 750 includes a plurality of equally-spaced diffraction peaks that each corresponds to diffracted beams from DMD 400. A horizontal axis 734 and a vertical axis 736 of FIGS. 7B and 7C indicate direction cosines of diffracted peaks related to x and y axes, respectively, of a coordinate system defined by the plurality of micromirrors 402. FIGS. 7B and 7C indicate intensities of diffraction patterns 730 and 750 according to an intensity scale 738.

[0060] Circles 732 of FIGS. 7B and 7C represent an aperture. Diffraction peaks lying within circle 732 represent diffraction beams that, in the absence of optical filter 600, would be projected by projection lens 612 as ON- and OFF- projected light, respectively. In FIG. 7B, a brightest (e.g., highest intensity) diffraction peak 740 at a center of circle 732 corresponds to an ON-diffraction beam and/or a zeroth order of ON-modulation light. Diffraction peaks lying outside of circle 732 will not be projected onto the projection screen 616.

[0061] In FIG. 7C, a brightest diffraction peak 752, corresponding to an OFF-diffracted beam, is at higher values of directional cosines outside circle 732, and therefore will not be projected onto the projection screen 614. However, at least in the absence of optical filter 600, a plurality of low- power diffraction peaks 754 in circle 732 would be projected onto the projection screen 614 as OFF- projected light, increasing OFF luminous intensity and decreasing PCR.

[0062] FIGS. 8A-8B illustrate additional individual components of a diffraction pattern from the DMD 400. FIG. 8A, in particularly, illustrates a cloud 800 of the diffraction pattern of a micromirror 402. The cloud 800 is related to the shape of the micromirrors 402. However, the size of the cloud 800 may not directly correlate with a size of the micromirror 402 and the size of the DMD 400. The cloud 800 includes a diffraction peak 805 situated at a center of the cloud 800. The cloud 800 also includes a plurality of diffraction orders, such as a first order 810, a second order 815, and a third order 820. While the first order 810, the second order 815, and the third order 820 are labelled only in a single direction (positive x-axis), the first order 810, the second order 815, and the third order 820 also extend in other directions (e.g., negative x-axis, positive y-axis, and negative y-axis) as a two-dimensional sine function. A position of the cloud 800 is dependent on the tilt angle of the respective micromirror 402, and moves in relation to the set tilt angle. FIG. 8B illustrates a diffraction pattern 850 of the grid of micromirrors 402 on the DMD 400 if every micromirror 402 is ON. The diffraction pattern 850 is comprised of “dots” of light, and therefore is comprised of zeroth order light.

[0063] Diffraction patterns of light modulated by the DMD 400 is a combination of the cloud 800 and the diffraction pattern 850. Particularly, the cloud 800 and the diffraction pattern 850 arc multiplied together to yield a diffraction pattern captured in pictures. As the grid of the plurality of micromirrors 402 is set and docs not change, the diffraction pattern 850 is the same for all images. However, as the micromirrors 402 themselves more, the cloud 800 may move depending on how the micromirrors 402 are tilted.

[0064] Additionally, the cloud 800 may vary for different color channels (for example, different wavelengths of light). For example, FIG. 9 illustrates a diffraction pattern 900 associated with a red color channel. The red diffraction pattern 900 includes a red diffraction peak 905. First and higher diffraction orders extend outward from the red diffraction peak 905. In the example red diffraction pattern 900, the intensity of the diffraction pattern 900 is spread across the first four orders (e.g., is anti-blazed). In some embodiments, the red diffraction pattern 900 may instead be blazed (e.g., centered on one diffraction order), or spread across fewer or greater diffraction orders.

[0065] FIG. 10 illustrates a diffraction pattern 1000 associated with a green color channel. The green diffraction pattern 1000 includes a green diffraction peak 1005. First and higher diffraction orders extend outward from the green diffraction peak 1005. In the example green diffraction pattern 1000, the intensity of the diffraction pattern 1000 is spread across the first four orders (e.g., is anti -blazed). In some embodiments, the green diffraction pattern 1000 may instead be blazed (e.g., centered on one diffraction order), or spread across fewer or greater diffraction orders.

[0066] FIG. 11 illustrates a diffraction pattern 1100 associated with a blue color channel. The blue diffraction pattern 1100 includes a blue diffraction peak 1105. First and higher diffraction orders extend outward from the blue diffraction peak 1105. In the example blue diffraction pattern 1100, the intensity of the diffraction pattern 1100 is centered primarily on the blue diffraction peak 1105. In some embodiments, the blue diffraction pattern 1100 may instead be anti-blazed and spread across multiple diffraction orders.

[0067] As previously described, modulated light from the modulation assembly is directed towards projection optics 214, 314. In some implementations, the projection optics 214, 314 is provided within a projection lens architecture. FIG. 12 is an exploded view of an exemplary projection lens system 1200 according to various aspects of the present disclosure. The projection lens system 1200 has a modular design. The projection lens system 1200 includes a Fourier part 1201 (for example, a Fourier lens assembly) configured to form a Fourier transform of an object at an exit pupil, an aperture 1202 (illustrated as a square aperture), and a zoom pail 1203 (also referred to as a zoom lens assembly). The spatial Fourier transform imposed by the Fourier part 1201 converts the propagation angle of each diffraction order of the modulated light to a corresponding spatial position on the Fourier plane. The Fourier pail 1201 thereby enables selection of desired diffraction orders, and rejection of undesired diffraction orders, by spatial filtering at the Fourier plane. The spatial Fourier transform of the modulated light at the Fourier plane is equivalent to a Fraunhofer diffraction pattern of the modulated light. [0068] The Fourier part 1201 includes a first attachment section 1204, which may include threads, fasteners, and the like. The zoom part 1203 includes a second attachment section 1205, which may include complementary threads, fasteners, and the like to allow for mating with the first attachment sections 1204. In one example, the first attachment section 1204 includes a male threaded portion and the second attachment section 1205 includes a female threaded portion, or vice versa. In another example, the first attachment section 1204 and the second attachment section 1205 are configured for a friction fit, in which case one or more fastening elements such as screws, cams, flanges, and so on may be provided. In yet another example, the first attachment section 1204 may include one or more radial pins and the second attachment section 1205 may include a corresponding number of L- shaped slots, or vice versa, to thereby connect the Fourier part 1201 and the zoom part 1203 using a bayonet connection. By these examples, the Fourier part 1201 may be removably attached to the zoom pail 1203 to provide a modular assembly.

[0069] While FIG. 12 illustrates the Fourier part 1201 and the zoom part 1203 as being entirely separable, the present disclosure is not so limited. In some implementations, the Fourier pail 1201 and the zoom part 1203 are only partially separable, for example by provided an access portion in one of the Fourier part 1201 and the zoom part 1203. The access portion may be a slot, a door, a window, and the like, such that an operator may access and/or swap the aperture 1202 via the access portion. In such implementations, the Fourier part 1201 and the zoom part 1203 may be bonded (e.g., via an adhesive on the first attachment section 1204 and/or the second attachment section 1205) to prevent full separation. Alternatively, the Fourier part 1201 and the zoom pail 1203 may be provided with an integral housing that includes the attachment portion.

[0070] The aperture 1202 is configured to block a portion of light (e.g., modulated light corresponding to one or more diffraction orders) in the projection lens system 1200 (e.g., modulated light provided via the modulation assembly 206, 306). As illustrated in FIG. 12, the aperture 1202 is a square opening having sides of, for example, 6 mm in length. FIG. 12 also illustrates an optical axis 1210 of the projection lens system 1200. When assembled, the Fourier part 1201 and the zoom pail 1203 are substantially coaxial with one another and with the optical axis 1210. In some implementations (for example, depending on the illumination angle), the aperture 1202 is not coaxial with the optical axis 1210.

[0071] The projection lens system 1200 may include or be associated with one or more non-optical elements, including a thermal dissipation device such as a heat sink (or cooling fins), one or more adhesives (or fasteners), and so on. In some implementations, the aperture 1202 may block, and thus absorb, approximately 15% of incident light and therefore the heat sink or cooling fins may be positioned and configured so as to appropriately dissipate heat from the aperture 1202. In some implementations, the aperture 1202 is thermally isolated from other parts of the projection lens system 1200.

[0072] The Fourier part 1201 and the aperture 1202 collectively operate as a Fourier lens with a spatial filter that may also be used as a fixed throw projection lens. The zoom part 1203 illustrated in FIG. 12 may be one of a family of zoom lens assemblies configured to attach to the Fourier part 1201, thereby to create the family of projection zoom lens systems and adapt to different theaters. In other words, the Fourier part 1201 and the aperture 1202 may be applicable to any theater setting, while the zoom part 1203 provides a specific projection light pattern tailored to a particular theater. Therefore, by selecting a particular zoom part 1203 from the family of zoom lens assemblies, and attaching the selected zoom part 1203 to the Fourier part 1201 and the aperture 1202, a projection lens system 1200 may be achieved which is adapted to the particular theater. Additionally, both the Fourier part 1201 and the zoom part 1203 may include a plurality of individual lens elements.

Example Fourier Filters

[0073] Color projectors typically rely on three primary color channels, such as red, green, and blue. However, as each color channel has a different diffraction pattern, what may be a suitable Fourier filter for one color channel may be ineffective for another color channel. As an example, a Fourier filter that passes only the zeroth order for one color channel may pass the zeroth and at least one first or higher order for one of the other color channels, which may be undesired in some situations. Accordingly, Fourier filters described herein combine several Fourier filters into one fdter (at or near the Fourier plane of the projection lens). In some implementations, the Fourier filters are integrated onto a single substrate. In other implementations, the Fourier filters are integrated on individual substrates and are situated in successive order to receive modulated white light. The Fourier filters may be dichroic filters.

[0074] FIG. 13 illustrates a first filter 1300, according to one example. The first filter 1300 includes a first transmission region 1305 configured to transmit all received light (for example, transmits light from the blue, green, and red color channels). In some instances, the first transmission region 1305 is coated with an anti-reflective coating. In other instances, the first transmission region 1305 is a hole in the substrate of the first filter 1300. The first transmission region 1305 has a diameter of x, which may transmit all light that passes through the first transmission region 1305. The first filter 1300 also includes a first aperture region 1310. The first aperture region 1310 may be configured to block light from the blue color channel, while transmitting light from the green and red color channels. For example, the first aperture region 1310 may be transparent for green and red color channels, but opaque for a blue color channel. The diameter x of the first transmission region 1305 may be selected such that only a desired amount of the blue color channel is transmitted by the first filter 1300. For example, the diameter x of the first transmission region 1305 may be a size that allows only the blue diffraction peak 1105 to be transmitted by the first filter 1300 while blocking other diffraction orders of the blue color channel. In another instance, the diameter x of the first transmission region 1305 is a size that allows both the blue diffraction peak 1105 and a first diffraction order of the blue color channel to be transmitted by the first filter 1300. The size of the diameter x may be considered as a diffraction threshold for the blue color channel, and may be increased or decreased based on a number of desired diffraction orders for the blue color channel. The first filter 1300 includes an outer circle 1315 configured to block light from all of the color channels. In some embodiments, the outer circle 1315 is a light dump that receives and directs, or alternatively receives and absorbs, undesired light.

[0075] FIG. 14 illustrates a second filter 1400, according to one example. The second filter 1400 includes a second transmission region 1405 configured to transmit all received light. The diameter y of the second transmission region 1405 may be larger than the diameter x of the first transmission region 1305 of the first filter 1300. The second transmission region 1405 may transmit all light that passes through the second transmission region 1405. In some instances, the second transmission region 1405 is coated with an anti-reflective coating. In other instances, the second transmission region 1405 is a hole in the substrate of the second filter 1400. The second filter 1400 includes a second aperture region 1410 configured to block light from the blue color channel and the green color channel, while transmitting light from the red color channel. For example, the second aperture region 1410 is transparent for the red color channel and opaque for the blue and green color channels. The diameter y of the second transmission region 1405 may be selected such that only a desired amount of the green color channel is transmitted by the second filter 1400. For example, the diameter y of the second transmission region 1405 may be a size that allows only the green diffraction peak 1005 to be transmitted by the second filter 1400 while blocking other diffraction orders of the green color channel. In another instance, the diameter y of the second transmission region 1405 is a size that allows both the green diffraction peak 1005 and a first diffraction order of the green color channel to be transmitted by the second filter 1 00. The size of the diameter y may be considered as a diffraction threshold for the green color channel, and may be increased or decreased based on a number of desired diffraction orders for the green color channel. The second filter 1400 includes the outer circle 1315.

[0076] FIG. 15 illustrates a third filter 1500, according to one example. The third filter 1500 includes a third transmission region 1505 configured to transmit all received light. The diameter z of the third transmission region 1505 may be larger than the diameter y of the second transmission region 1405 of the second filter 1400. In some instances, the third transmission region 1505 is coated with an anti-reflective coating. In other instances, the third transmission region 1505 is a hole in the substrate of the third filter 1500. The third filter 1500 includes a third aperture region 1510 configured to block light from the blue color channel, the green color channel, and the red color channel. For example, the third aperture region 1510 is opaque for the blue, green, and red color channels. The diameter z of the third transmission region 1505 may be selected such that only a desired amount of the red color channel is transmitted by the third filter 1500. For example, the diameter z of the third transmission region 1505 may be a size that allows only the red diffraction peak 905 to be transmitted by the third filter 1500 while blocking other diffraction orders of the red color channel. In another instance, the diameter z of the third transmission region 1505 is a size that allows both the red diffraction peak 905 and a first diffraction order of the red color channel to be transmitted by the third filter 1500. The size of the diameter z. may be considered as a diffraction threshold for the red color channel, and may be increased or decreased based on a number of desired diffraction orders for the red color channel. The third filter 1500 includes the outer circle 1315.

[0077] The first filter 1300, the second filter 1400, and the third filter 1500 may be combined to form a single Fourier filter 1600, shown in FIGS. 16-17. FIG. 16 illustrates a front view of the Fourier filter 1600. The first filter 1300, the second filter 1400, and the third filter 1500 may be formed onto a single substrate. In FIG. 16, the first transmissive region 1305, the second transmissive region 1405, and the third transmissive region 1505 are configured as holes. The third filter 1500 is stacked on top, covering the second filter 1400. The second filter 1400 covers the first filter 1300. As the third filter 1500 is on top, the entirety of the third aperture region 1510 is completely revealed. [0078] As the third transmission region 1505 has a diameter of z which is larger than the diameter y of the second transmission region 1405, a portion of the second aperture region 1410 is exposed. Additionally, as the second transmission region 1405 has a diameter y which is larger than the diameter x of the first transmission region 1305, a portion of the first aperture region 1310 is exposed. Accordingly, with reference to FIG. 16 and beginning in the center of the Fourier filter 1600 and moving outwards, the Fourier filter 1600 includes a first transmission region 1305 in which light from all color channels is transmitted, a first aperture region 1 10 in which light of the first and second color channels (for example, red and green color channels) are transmitted and light of the third color channel (for example, a blue color channel) is blocked, a second aperture region 1410 in which light of the first color channel (for example, a red color channel) is transmitted and light of the second and third color channels (for example, green and blue color channels) are blocked, a third aperture region 1510 in which all color channels are blocked, and an outer circle 1315.

[0079] This configuration provides for a different effective size of the Fourier filter 1600 for each color channel. For example, light traveling through the Fourier filter 1600 includes a red color channel, a green color channel, and a blue color channel. The first transmission region 1305 transmits light of each color channel. The first aperture region 1310 transmits light of the red color channel and the green color channel. However, the first aperture region 1310 blocks light of the blue color channel. Accordingly, the effective size of the Fourier filter 1600 experienced by the blue color channel is a circle having a diameter of x. Next, the second aperture region 1410 transmits light of the red color channel, but blocks light of both the green color channel and the blue color channel. Accordingly, the effective size of the Fourier filter 1600 experienced by the green color channel is a circle having a diameter of y. Finally, the third aperture region 1510 blocks light of the red color channel, the green color channel, and the blue color channel. Accordingly, the effective size of the Fourier filter 1600 experienced by the red color channel is a circle having a diameter of z.

[0080] Additionally, the size of each transmission region may be adjusted based on which diffraction orders of each color channel are desired. For example, altering the diameter x alters which diffraction orders of the blue color channel are transmitted. Altering the diameter y alters which diffraction orders of the green color channel are transmitted. Altering the diameter z alters which diffraction orders of the red color channel are transmitted. [0081] In some implementations, the first aperture region 1310, the second aperture region 1410, and the third aperture region 1510 are each coated with a dichroic (or trichroic) coating. Dichroic coatings are thin-film coatings that selectively pass one or more color bands while reflecting other color bands. Accordingly, dichroic coatings may be configured to transmit zeroth order light of certain color channels and block first and higher order light of other color channels. For example, a dichroic coating applied to the first aperture region 1310 may be configured to transmit a red color channel and a green color channel while blocking a blue color channel. A dichroic coating applied to the second aperture region 1410 may be configured to transmit a red color channel while blocking a green color channel and a blue color channel. A dichroic coating applied to the third aperture region 1510 may be configured to block a red color channel, a green color channel, and a blue color channel.

[0082] In some embodiments, rather than applying a coating that reflects particular color channels, an absorptive coating is applied to each aperture region that absorbs particular color channels while transmitting other color channels. In one implementation, to configure the absorptive coating for each aperture region, a thickness of the absorptive coating is varied for to alter the filtering characteristics of each aperture region. In some examples, a refractive technique is used for creating the first aperture region 1310, the second aperture region 1410, and/or the third aperture region 1510. For example, a surface of a lens forming the Fourier filter 1600 may be altered to direct undesired light towards a light dump (for example, the outer region 1315). Each aperture region directs a different color channel towards the light dump.

[0083] While FIG. 16 illustrates the first aperture region 1310, the second aperture region 1410, and the third aperture region 1510 as three discrete regions, in some embodiments, the aperture regions are applied as a gradient to smoothly transition between what color channels are filtered. For example, the dichroic coating may be configured as a gradient coating to smooth the edges between each aperture region. In another implementation, a half-toning laser method is applied to the Fourier filter 1600 to create the first aperture region 1310, the second aperture region 1410, and the third aperture region 1510.

[0084] In some instances, rather than being provided on a single substrate, the first filter 1300, the second filter 1400, and the third filter 1500 may be separated on individual substrates to form the Fourier filter 1600, as shown in FIG. 17. FIG. 17 provides a side view of the Fourier filter 1600 according to another example. While the first filter 1300, the second filter 1400, and the third filter 1500 are on separate substrates, a front view of the Fourier filter 1600 would be substantially similar to that shown in FIG. 16 for the example of the single substrate. In the example of FIG. 17, the third filter 1500 and the second filter 1400 are separated by a distance of a, and the second filter 1400 and the first filter 1300 are separated by a distance of b. Distance a and distance b are merely examples, and other distances may be implemented. In some implementations, the controller 116 may vary the values of distance a and distance b by moving the first filter 1300, the second filter 1400, and/or the third filter 1500 based on applications of the projection system 100.

[0085] A light beam 1705 includes the red color channel, the green color channel, and the blue color channel. As the light beam 1705 travels through the Fourier filter 1600, the light beam 1705 first contacts the third filter 1500. The third aperture portion 1510 blocks all color channels included in the light beam 1705, and the third transmission portion 1505 transmits all color channels included in the light beam 1705.

[0086] Next, the remaining light beam 1705 contacts the second filter 1400. The second aperture portion 1410 blocks the blue color channel and the green color channel included in the light beam 1705, but transmits the red color channel (transmitted as a first filtered light beam 1710). The second transmission portion 1405 transmits each color channel included in the light beam 1705.

[0087] Lastly, the remaining light beam 1705 contacts the first filter 1300. The first aperture portion 1310 blocks the blue color channel included in the light beam 1305, but transmits the red color channel and the green color channel (transmitted as a second filtered light beam 1715). The first transmission portion 1305 transmits each color channel included in the light beam 1305. The final light output by the Fourier filter 1600 includes the remaining light beam 1705, the first filtered light beam 1710, and the second filtered light beam 1715. The effective size of the Fourier filter 1600 is smallest for the blue color channel, as the blue color channel is transmitted by each transmission portion, but is blocked by the first aperture region 1310, the second aperture region 1410, and the third aperture region 1510. Accordingly, the effective size of the Fourier filter 1600 experienced by the blue color channel is equal to the size of the first transmission region 1305. The effective size of the Fourier filter 1600 is larger for the green color channel compared to the blue color channel, as the green color channel is transmitted by each transmission portion and the first aperture portion 1310. Accordingly, the effective size of the Fourier filter 1600 experienced by the green color channel is equal to the size of the second transmission region 1405. The effective size of the Fourier filter 1600 is largest for the red color channel compared to the green and blue color channels, as the red color channel is transmitted by each transmission portion, the first aperture portion 1310, and the second aperture portion 1410. Accordingly, the effective size of the Fourier filter 1600 experienced by the red color channel is equal to the size of the third transmission region 1505.

[0088] While embodiments described herein have primarily referred to filters with circular transmission portions, the transmission portions may also be other shapes. For example, FIG. 18 provides an example Fourier filter 1800 having square transmission and filtering portions. The Fourier filter 1800 includes a first transmission portion 1805, a first filtering portion 1810, a second filtering portion 1815, an aperture portion 1820, and an outer edge 1825. The first transmission portion 1805 is configured to transmit all color channels. The first filtering portion 1810 is configured to transmit light of a first color channel and a second color channel (for example, red and green color channels), but block light of a third color channel (for example, a blue color channel). The second filtering portion 1815 is configured to transmit light of the first color channel (for example, a red color channel), but block light of the second color channel and the third color channel (for example, green and blue color channels). The aperture portion 1820 is configured to block all color channels. The Fourier filter 1800 may be formed on a single substrate or may be formed across multiple substrates, as previously described with respect to Fourier filter 1600. In addition to squares and circles, the transmission and filtering portions may be formed of other shapes, such as triangles, diamonds, ovals, and the like.

[0089] Additionally, embodiments described herein have primarily illustrated example Fourier filters where each filter forming the Fourier filter share a same center point. However, in some implementations, the filters forming the Fourier filter may be offset from one another. For example, FIG. 19 provides an example Fourier filter 1900. Similar to the Fourier filter 1800 of FIG. 18, the Fourier filter 1900 includes a first transmission portion 1905, a first filtering portion 1910, a second filtering portion 1915, an aperture portion 1920, and an outer edge 1925. The first transmission portion 1905 is configured to transmit all color channels. The first filtering portion 1910 is configured to transmit light of a first color channel and a second color channel (for example, red and green color channels), but block light of a third color channel (for example, a blue color channel). The second filtering portion 1915 is configured to transmit light of the first color channel (for example, a red color channel), but block light of the second color channel and the third color channel (for example, green and blue color channels). The aperture portion 1920 is configured to block all color channels. The Fourier filter 1900 may be formed on a single substrate or may be formed across multiple substrates, as previously described with respect to Fourier filter 1600.

[0090] The first transmission portion 1905 has a first center 1950. The first center 1950 is shared by the outer edge 1925. The first filtering portion 1910 has a second center 1955 offset from the first center 1950. Specifically, in the example illustrated by FIG. 19, the second center 1955 is offset along the x-axis from the first center 1950. Additionally, the second filtering portion 1915 has a third center 1960 offset from the first center 1950. Specifically, in the example illustrated by FIG. 19, the third center 1960 is offset along the y-axis from the first center 1950. In some embodiments, the shapes of the filtering portions may vary in addition to varying the positions. For example, the first transmission portion 1905 may be a circle instead of a square. In some implementations, the first center 1950 is aligned with a center of the red diffraction peak 905, the second center 1955 is aligned with a center of the green diffraction peak 1005, and the third center 1960 is aligned with a center of the blue diffraction peak 1105.

[0091] Optical filters disclosed herein may be altered for various scenarios. For example, to minimize a pixel size output of the projector system 100, the transmission portions of the optical filters may be configured to align with a center of the cloud of each color channel. For example, with reference to FIG. 16, a center of the first transmission region 1305 may be aligned with a center of the diffraction pattern of the blue color channel (e.g., aligned with the blue diffraction peak 1105), a center of the first aperture region 1310 may be aligned with a center of the diffraction pattern of the green color channel (e.g., aligned with the green diffraction peak 1005), and a center of the second aperture region 1410 may be aligned with a center of the diffraction pattern of the red color channel (e.g., aligned with the red diffraction peak 905). Additionally, each micromirror 402 has approximately the same tilt angle to align the diffraction patterns of each color channel. The output pixel size is reduced by aligning the diffraction patterns and transmitting only the brightest portions of each diffraction pattern. Such an implementation increases the efficiency of the projector system 100, and may increase the effectiveness of a wobulator increasing the resolution of an image output by the projector system 100.

[0092] Another example includes configuring the transmission portions of the optical filters to increase contrast of the projector system 100. For example, the contrast may be highest for particular diffraction orders of each color channel. Rather than centering the transmission portions to align with the center of the cloud of each color channel, as described above, the transmission portions may instead be centered on the highest-contrast diffraction orders. For example, to determine the contrast of diffraction orders, the ratio of intensity across the Fourier part 1201 when all of the plurality of micromirrors 202 are on may be compared to the intensity across the Fourier part 1201 when all of the plurality of micromirrors 202 arc off. As one example with reference to FIG. 19, the first transmission region 1905 may be centered on a first diffraction order of the blue color channel, the first aperture region 1910 may be centered on a second diffraction order of the green color channel, and the second aperture region 1915 may be centered on a third diffraction order of the red color channel. These diffraction orders may be offset from the diffraction peak of each respective color channel. Additionally, the transmission regions may be configured to transmit a range of diffraction orders for each color channel. For example, the first transmission region 1905 transmits a first range of diffraction orders for the blue color channel, the first aperture region 1910 transmits a second range of diffraction orders for the green color channel, and the second aperture region 1915 transmits a third range of diffraction orders for the red color channel. In instances where the color channels are separately modulated, the micromirrors 402 may have different tilt angles for each color channel.

[0093] Systems, methods, and devices in accordance with the present disclosure may take any one or more of the following configurations.

[0094] (1) A projection lens assembly, comprising: an optical filter configured to spatially Fourier transform a tri-colored light to generate a filtered light output, wherein, when traveling through the optical filter, each color channel included in the tri-colored light experiences a different effective size of the optical filter.

[0095] (2) The projection lens assembly according to (1), wherein the tri-colored light includes at least a first color channel and a second color channel, wherein the optical filter includes a first region configured to transmit the first color channel and the second color channel, and wherein the first region is located centrally on the optical filter.

[0096] (3) The projection lens assembly according to (2), wherein the optical filter includes a second region configured to transmit the first color channel and block the second color channel and wherein a diameter of the second region is greater than a diameter of the first region. [0097] (4) The projection lens assembly according to (3), wherein the optical filter includes a third region configured to block the first color channel and block the second color channel, and wherein a diameter of the third region is greater than the diameter of the second region.

[0098] (5) The projection lens assembly according to any one of (1) to (4), wherein the optical filter includes an absorptive coating, and wherein a thickness of the absorptive coating varies across a diameter of the optical filter.

[0099] (6) The projection lens assembly according to any one of (1) to (5), wherein the optical filter includes a first filter region and a second filter region, wherein a center of the first filter region is situated at a center of the optical filter, and wherein a center of the second filter region is offset from the center of the optical filter.

[00100] (7) The projection lens assembly according to any one of (1) to (6), wherein each color channel included in the tri-colored light has a same illumination angle.

[00101] (8) The projection lens assembly according to any one of (1) to (7), wherein the optical filter includes a plurality of dichroic coatings, and wherein each dichroic coating of the plurality of dichroic coatings is configured to transmit a different range of wavelengths.

[00102] (9) The projection lens assembly according to any one of (1) to (8), wherein the optical filter includes a gradient dichroic coating, and wherein a range of wavelengths reflected by the gradient dichroic coating varies across a diameter of the optical filter.

[00103] (10) A method of filtering light with an optical filter, the method comprising: receiving, at the optical filter, a light beam comprised of a plurality of color channels; transmitting, with a transmission portion of the optical filter, a first color channel and a second color channel of the plurality of color channels; blocking, with a first filtering portion of the optical filter, the first color channels ; transmitting, with the first filtering portion of the optical filter, the second color channel; and blocking, with a second filtering portion of the optical filter, the first color channel and the second color channel.

[00104] (11) The method according to (10), wherein each of the plurality of plurality of color channels have a same illumination angle. [00105] (12) The method according to any one of (10) to (11), wherein the first filtering portion includes a first dichroic coating configured to transmit a first range of wavelengths, and wherein the second filtering portion includes a second dichroic coating configured to transmit a second range of wavelengths.

[00106] (13) The method according to any one of (10) to (11), wherein the optical filter includes an absorptive coating, and wherein a thickness of the absorptive coating varies across a diameter of the optical filter.

[00107] (14) The method according to any one of (10) to (11), wherein the optical filter includes a gradient dichroic coating, and wherein a range of wavelengths reflected by the gradient dichroic coating varies across a diameter of the optical filter.

[00108] (15) A projector comprising: a light source configured to emit light in response to an image signal, the image signal including image data; a modulator configured to receive the light from the light source and to apply a spatially-varying modulation on the light, thereby to steer the light and to generate a first steered light, wherein the first steered light includes a plurality of color channels; and a projection lens assembly including an optical filter configured to spatially Fourier transform the first steered light to generate a filtered light output, wherein, when traveling through the optical filter, each of the plurality of color channels experiences a different effective size of the optical filter.

[00109] (16) The projector according to (15), wherein the plurality of color channels includes a first color channel and a second color channel, wherein the optical filter includes a first region configured to transmit the first color channel and the second color channel, and wherein the first region is located centrally on the optical filter.

[00110] (17) The projector according to (16), wherein the optical filter includes a second region configured to transmit the first color channel and block the second color channel, and wherein a diameter of the second region is greater than a diameter of the first region.

[00111] (18) The projector according to (17), wherein the optical filter includes a third region configured to block the first color channel and block the second color channel, and wherein a diameter of the third region is greater than the diameter of the second region. [00112] (19) The projector according to any one of (15) to (18), wherein the optical filter includes a first transmissive region and a second transmissive region, wherein a center of the first transmissive region is situated at a center of the optical filter, and wherein a center of the second transmissive region is offset from the center of the optical filter.

[00113] (20) The projector according to any one of (15) to (19), wherein the optical filter includes a plurality of dichroic coatings, wherein each dichroic coating of the plurality of dichroic coatings is configured to transmit a different range of wavelengths.

[00114] (21) A projector lens assembly, comprising: a lens configured to spatially Fourier transform tri-color light from a modulator onto a Fourier plane; and an optical filter disposed at the Fourier plane and divided into multiple regions, wherein a first region of the optical filter is substantially transparent to the tri-color light and wherein at least a second region of the optical filter is substantially opaque to at least one wavelength of the tri-color light while being substantially transparent to at least one other wavelength of the tri-color light.

[00115] (22) The projector lens assembly according to (21), wherein the first region is located centrally on the optical filter.

[00116] (23) The projector lens assembly according to (22), wherein a diameter of the second region is greater than a diameter of the first region.

[00117] (24) The projector lens assembly according to (23), wherein at least a third region of the optical filter is substantially opaque to the tri-color light.

[00118] (25) The projector lens assembly according to any one of (21) to (24), wherein the optical filter includes an absorptive coating, and wherein a thickness of the absorptive coating varies across a diameter of the optical filter.

[00119] (26) The projector lens assembly according to any one of (21) to (25), wherein a center of the first region is situated at a center of the optical filter, and wherein a center of the second region is offset from the center of the optical filter.

[00120] (27) The projector lens assembly according to any one of (21) to (26), wherein each wavelength of the tri-color light has a same illumination angle. [00121] (28) The projector lens assembly according to any one of (21) to (27), wherein the optical filter includes a dichroic coating on each of the multiple regions, each dichroic coating configured to transmit a different range of wavelengths of the tri-color light.

[00122] (29) The projector lens assembly according to any one of (21) to (28), wherein the optical filter includes a gradient dichroic coating, and wherein a range of wavelengths of the tricolor light reflected by the gradient dichroic coating varies across a diameter of the optical filter.

[00123] (30) A projector comprising: a light source configured to emit a tri-color light in response to an image signal, the image signal including image data; a modulator configured to receive the tri-color light from the light source and to apply a spatially-varying modulation on the tri-color light, thereby to steer the tri-color light and to generate a first steered light, wherein the first steered light includes at least a first color channel having a first diffraction pattern and a second color channel having a second diffraction pattern; and a projection lens assembly including an optical filter configured to spatially Fourier transform the plurality of color channels to generate a filtered light output, the optical filter including: a first region configured to transmit the first color channel and block the second color channel, the first region aligned with a diffraction peak of the second diffraction pattern, and a second region configured to block the first color channel and the second color channel, the second region aligned with a diffraction peak of the first diffraction pattern.

[00124] (31) The projector according to (30), further comprising: a wobulation device configured to increase a resolution of the first steered light.

[00125] (32) The projector according to any one of (30) to (31), wherein the first region is configured to transmit a first range of diffraction orders included in the diffraction pattern less than a first diffraction threshold, and wherein the second region is configured to transmit a second range of diffraction orders included in the diffraction pattern less than a second diffraction threshold.

[00126] (33) The projector according to any one of (30) to (32), wherein the first color channel and the second color channel have a same illumination angle.

[00127] (34) The projector according to any one of (30) to (33), wherein the optical filter further includes: a third region configured to transmit the first color channel and the second color channel, the third region aligned with a center of the optical filter. [00128] (35) A projector comprising: a light source configured to emit a tri-color light in response to an image signal, the image signal including image data; a modulator configured to receive the tri-color light from the light source and to apply a spatially-varying modulation on the tri-color light, thereby to steer the tri-color light and to generate a first steered light, wherein the first steered light includes at least a first color channel having a first diffraction pattern and a second color channel having a second diffraction pattern; and a projection lens assembly including an optical filter configured to spatially Fourier transform the plurality of color channels to generate a filtered light output, the optical filter including: a first region configured to transmit the first color channel and block the second color channel, the first region aligned with a high-contrast diffraction order of the second diffraction pattern, and a second region configured to block the first color channel and the second color channel, the second region aligned with a high-contrast diffraction order of the first diffraction pattern.

[00129] (36) The projector according to (35), wherein the first region is misaligned with a diffraction peak of the second diffraction pattern, and wherein the second region is misaligned with a diffraction peak of the first diffraction pattern.

[00130] (37) The projector according to any one of (35) to (36), wherein the first region is configured to transmit a first range of diffraction orders included in the diffraction pattern less than a first diffraction threshold, and wherein the second region is configured to transmit a second range of diffraction orders included in the diffraction pattern less than a second diffraction threshold.

[00131] (38) The projector according to any one of (35) to (37), wherein the first color channel and the second color channel have a different illumination angles.

[00132] (39) The projector according to any one of (35) to (38), wherein the optical filter further includes: a third region configured to transmit the first color channel and the second color channel, the third region aligned with a center of the optical filter.

[00133] (40) The projector according to any one of (35) to (39), wherein the optical filter includes a dichroic coating on the first region and the second region.

[00134] With regard to the processes, systems, methods, heuristics, etc. described herein, it should be understood that, although the steps of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously, that other steps could be added, or that certain steps described herein could be omitted. In other words, the descriptions of processes herein are provided for the purpose of illustrating certain embodiments, and should in no way be construed so as to limit the claims.

[00135] Accordingly, it is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments and applications other than the examples provided would be apparent upon reading the above description. The scope should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the technologies discussed herein, and that the disclosed systems and methods will be incorporated into such future embodiments. In sum, it should be understood that the application is capable of modification and variation.

[00136] All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those knowledgeable in the technologies described herein unless an explicit indication to the contrary in made herein. In particular’, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.

[00137] The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments incorporate more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims arc hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.

Claims

CLAIMS What is claimed is:

1. A projection lens assembly, comprising: a lens configured to spatially Fourier transform tri-color light from a modulator onto a Fourier plane; and an optical filter disposed at the Fourier plane and divided into multiple regions, wherein a first region of the optical filter is substantially transparent to the tri-color light and wherein at least a second region of the optical filter is substantially opaque to at least one wavelength of the tri-color light while being substantially transparent to at least one other wavelength of the tri-color light.

2. The projection lens assembly of claim 1, wherein the first region is located centrally on the optical filter.

3. The projection lens assembly of claim 2, wherein a diameter of the second region is greater than a diameter of the first region.

4. The projection lens assembly of claim 3, wherein at least a third region of the optical filter is substantially opaque to the tri-color light.

5. The projection lens assembly of any one of claims 1 to 4, wherein the optical filter includes an absorptive coating, and wherein a thickness of the absorptive coating varies across a diameter of the optical filter.

6. The projection lens assembly of any one of claims 1 to 5, wherein a center of the first region is situated at a center of the optical filter, and wherein a center of the second region is offset from the center of the optical filter.

7. The projection lens assembly of any one of claims 1 to 6, wherein each wavelength of the tricolor light has a same illumination angle.

8. The projection lens assembly of any one of claims 1 to 7, wherein the optical filter includes a dichroic coating on each of the multiple regions, each dichroic coating configured to transmit a different range of wavelengths of the tri-color light.

9. The projection lens assembly of any one of claims 1 to 8, wherein the optical filter includes a gradient dichroic coating, and wherein a range of wavelengths of the tri-color light reflected by the gradient dichroic coating varies across a diameter of the optical filter.

10. A projector comprising: a light source configured to emit a tri-color light in response to an image signal, the image signal including image data; a modulator configured to receive the tri-color light from the light source and to apply a spatially-varying modulation on the tri-color light, thereby to steer the tri-color light and to generate a first steered light, wherein the first steered light includes at least a first color channel having a first diffraction pattern and a second color channel having a second diffraction pattern; and a projection lens assembly including an optical filter configured to spatially Fourier transform the plurality of color channels to generate a filtered light output, the optical filter including: a first region configured to transmit the first color channel and block the second color channel, the first region aligned with a diffraction peak of the second diffraction pattern, and a second region configured to block the first color channel and the second color channel, the second region aligned with a diffraction peak of the first diffraction pattern.

11. The projector of claim 10, further comprising: a wobulation device configured to increase a resolution of the first steered light.

12. The projector of claim 10 or 11, wherein the first region is configured to transmit a first range of diffraction orders included in the diffraction pattern less than a first diffraction threshold, and wherein the second region is configured to transmit a second range of diffraction orders included in the diffraction pattern less than a second diffraction threshold.

13. The projector of any one of claims 10 to 12, wherein the first color channel and the second color channel have a same illumination angle.

14. The projector of any one of claims 10 to 13, wherein the optical filter further includes: a third region configured to transmit the first color channel and the second color channel, the third region aligned with a center of the optical filter.

15. A projector comprising: a light source configured to emit a tri-color light in response to an image signal, the image signal including image data; a modulator configured to receive the tri-color light from the light source and to apply a spatially-varying modulation on the tri-color light, thereby to steer the tri-color light and to generate a first steered light, wherein the first steered light includes at least a first color channel having a first diffraction pattern and a second color channel having a second diffraction pattern; and a projection lens assembly including an optical filter configured to spatially Fourier transform the plurality of color channels to generate a filtered light output, the optical filter including: a first region configured to transmit the first color channel and block the second color channel, the first region aligned with a high-contrast diffraction order of the second diffraction pattern, and a second region configured to block the first color channel and the second color channel, the second region aligned with a high-contrast diffraction order of the first diffraction pattern.

16. The projector of claim 15, wherein the first region is misaligned with a diffraction peak of the second diffraction pattern, and wherein the second region is misaligned with a diffraction peak of the first diffraction pattern.

17. The projector of claim 15 or 16, wherein the first region is configured to transmit a first range of diffraction orders included in the diffraction pattern less than a first diffraction threshold, and wherein the second region is configured to transmit a second range of diffraction orders included in the diffraction pattern less than a second diffraction threshold.

18. The projector of any one of claims 15 to 17, wherein the first color channel and the second color channel have a different illumination angles.

19. The projector of any one of claims 15 to 18, wherein the optical filter further includes: a third region configured to transmit the first color channel and the second color channel, the third region aligned with a center of the optical filter.

20. The projector of any one of claims 15 to 19, wherein the optical filter includes a dichroic coating on the first region and the second region.