Patent Description:
This application relates generally to projection systems and projection methods.

Digital projection systems typically utilize a light source and an optical system to project an image onto a surface or screen. The optical system may include components such as mirrors, lenses, waveguides, optical fibers, beam splitters, diffusers, spatial light modulators (SLMs), and the like. The 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," "native," or "sequential" contrast ratio.

Some projection systems are based on SLMs that implement a spatial amplitude modulation, such as a digital micromirror device (DMD) chip. A DMD may utilize a two-dimensional array of mirrors which can be controlled to create an image. If one desires to project an image with a higher resolution than that of the DMD (e.g., an image having a greater number of pixels than the number of mirrors in the DMD), pixel-shifting techniques may be used. In one comparative example of a pixel-shifting technique, sometimes called "wobulation," the system may be controlled to effectively shift the modulator by fractional pixels in a set pattern to create the appearance of displaying additional pixels. <CIT> discloses a known pixelated color management device in a digital display system, having a wobulation control circuit which shifts individually defined pixels of the spatial light modulator from one array of pixel locations to another array of locations on the viewing surface.

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

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:.

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.

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.

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.

The optics of an SLM-based projection system may be broadly categorized into two parts: the optics located on the illumination side (i.e., optically upstream of the SLM) and the optics located on the projection side (i.e., optically downstream of the SLM). The SLM itself includes a plurality of modulating elements arranged in, for example, a two-dimensional array. Individual modulating elements receive light from the illumination optics and convey light to the projection optics. In some examples, the SLM may be implemented as a DMD; this will be discussed in more detail below. Generally, however, a DMD includes a two-dimensional array of reflective elements (micromirrors or simply "mirrors") which selectively reflect light towards the projection optics or discard light based on the position of the individual reflective elements.

<FIG> illustrate various views of an exemplary DMD <NUM> according to various aspects of the present disclosure. In particular, <FIG> illustrates a plan view of the DMD <NUM> and <FIG> illustrates a partial cross-sectional view of the DMD <NUM> taken along line I-B illustrated in <FIG>. The DMD <NUM> includes a plurality of square micromirrors <NUM> arranged in a two-dimensional rectangular array on a substrate <NUM>. In some examples, the DMD <NUM> may be a digital light processor (DLP) device. Each micromirror <NUM> may correspond to one pixel of the eventual projection image, and may be configured to tilt about a rotation axis <NUM>, shown for one particular subset of the micromirrors <NUM>, by electrostatic or other actuation. The individual micromirrors <NUM> have a width <NUM> and are arranged with gaps of width <NUM> therebetween. The micromirrors <NUM> 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 <NUM> may be absorptive, such that input light which enters a gap is absorbed by the substrate <NUM>.

While <FIG> expressly shows only some representative micromirrors <NUM>, in practice the DMD <NUM> may include many more individual micromirrors. The resolution of the DMD <NUM> refers to the number of micromirrors in the horizontal and vertical directions. In some examples, the resolution may be <NUM> (<NUM>×<NUM>), <NUM> (<NUM>×<NUM>), 1080p (<NUM>×<NUM>), consumer <NUM> (<NUM>×<NUM>), and the like. Moreover, in some examples the micromirrors <NUM> may be rectangular and arranged in the rectangular array; hexagonal and arranged in a hexagonal array, and the like. Moreover, while <FIG> illustrates the rotation axis <NUM> extending in an oblique direction, in some implementations the rotation axis <NUM> may extend vertically or horizontally.

As can be seen in <FIG>, each micromirror <NUM> may be connected to the substrate <NUM> by a yoke <NUM>, which is rotatably connected to the micromirror <NUM>. The substrate <NUM> includes a plurality of electrodes <NUM>. While only two electrodes <NUM> per micromirror <NUM> are visible in the cross-sectional view of <FIG>, each micromirror <NUM> may in practice include additional electrodes. While not particularly illustrated in <FIG>, the DMD <NUM> may further include spacer layers, support layers, hinge components to control the height or orientation of the micromirror <NUM>, and the like. The substrate <NUM> may include electronic circuitry associated with the DMD <NUM>, such as CMOS transistors, memory elements, and the like.

Depending on the particular operation and control of the electrodes <NUM>, the individual micromirrors <NUM> may be switched between an "on" position, an "off' position, and an unactuated or neutral position. If a micromirror <NUM> is in the on position, it is actuated to an angle of, e.g., -<NUM>° (that is, rotated counterclockwise by <NUM>° relative to the neutral position) to specularly reflect input light <NUM> into on-state light <NUM>. If a micromirror <NUM> is in the off position, it is actuated to an angle of, e.g., +<NUM>° (that is, rotated clockwise by <NUM>° relative to the neutral position) to specularly reflect the input light <NUM> into off-state light <NUM>. The off-state light <NUM> may be directed toward a light dump that absorbs the off-state light <NUM>. In some instances, a micromirror <NUM> may be unactuated and lie parallel to the substrate <NUM>. The particular angles illustrated in <FIG> and described here are merely exemplary and not limiting. In some implementations, the on- and off-position angles may be between ±<NUM> and ±<NUM> degrees (inclusive), respectively.

In some implementations, the resolution of the DMD <NUM> may be lower than the desired resolution of the projected image. For example, one may desire to project an image having a <NUM> resolution, but DMDs having a <NUM> resolution may have limited or no commercial availability, prohibitive costs, and so on. In such implementations, it may be possible to control the relatively-low-resolution DMD <NUM> to effectively display additional pixels in the projected image. For example, a <NUM> mirror array may be controlled to display a <NUM> projected image, or a 1080p mirror array may be controlled to display a consumer <NUM> projected image. Pixel-shift techniques may be used to effect this control.

One exemplary pixel-shift technique (wobulation) uses some method (e.g., an optical method) to effectively shift the DMD <NUM> by fractional pixels in a set pattern to display additional pixels. One example of such a pixel-shift technique is illustrated in <FIG>. In the pixel-shift technique of <FIG>, a frame display period T (generally one divided by the projector frame rate) into four sub-periods each having a duration of T/<NUM>. At a time t<NUM> corresponding to the start of the first sub-period and thus the start of the frame display period T, an image is projected onto the screen. In <FIG>, only a <NUM>×<NUM> subset of the pixels in the first resulting image <NUM> are shown; however, the first resulting image <NUM> in practice has a resolution corresponding to the relatively-lower resolution of the DMD <NUM>. At a time t<NUM> corresponding to the start of the second sub-period, the image is shifted a half-pixel to the right, thus generating the second resulting image <NUM> on the screen. At a time t<NUM> corresponding to the start of the third sub-period, the image is shifted a half-pixel down, thus generating the third resulting image <NUM> on the screen. At a time t<NUM> corresponding to the start of the fourth sub-period, the image is shifted a half-pixel left, thus generating the fourth resulting image <NUM> on the screen. At the end of the frame display period T, the image may be shifted a half-pixel up, thus corresponding to the original position to begin display of the next frame. As can be seen from <FIG>, each shift increases the effective display resolution. The direction of shifting is not limited to the column and row directions of the pixel array (i.e., up, down, left, and right), but may instead be in an oblique direction (e.g., diagonal). Moreover, while <FIG> shows a pixel-shifting technique which shifts the image in two dimensions, in certain implementations pixel-shifting may only occur in one dimension in a back-and-forth manner.

This pixel-shift technique, taken alone, may not be sufficient to properly reproduce the desired high-resolution images. For example, the pixels at the lower resolution are four times as large as would be used to display a true image at the higher resolution. Thus, while this technique, taken alone, allows for the display of more pixel data, the overlap prevents a complete reproduction of high-resolution images. In the most extreme example, where the image for display is a full-resolution black/white checkerboard pattern, the above technique, taken alone, will display a flat gray field instead of a checkerboard due to the overlap between every adjacent white and black pixel in the checkerboard. To counteract the effects of the overlap, the design of various physical components of the projector system itself may be modified.

Some projection systems are based on SLMs that implement a spatial amplitude modulation. In such a system, the light source may provide a light field that embodies the brightest level that can be reproduced on the image, and light is attenuated or discarded in order to create the desired scene levels. Some high contrast examples of projection systems based on this architecture use a semi-collimated illumination system and Fourier stop in the projection optics to improve contrast. An example of a projector or other display system including or relating to a Fourier plane and aperture have been described in commonly-owned patents and patent applications, including WIPO Pub. No. <CIT>, titled "Systems and Methods for Digital Laser Projection with Increased Contrast Using Fourier Filter.

<FIG> illustrates an exemplary high contrast projection system <NUM> according to various aspects of the present disclosure. In particular, <FIG> illustrates a projection system <NUM> which includes a light source <NUM> configured to emit a first light <NUM>; illumination optics <NUM> configured to receive the first light <NUM> and redirect or otherwise modify it, thereby to generate a second light <NUM>; a DMD <NUM> configured to receive the second light <NUM> and selectively redirect and/or modulate it as a third light <NUM>; first projection optics <NUM> configured to receive the third light <NUM> and redirect or otherwise modify it, thereby to generate a fourth light <NUM>; a filter <NUM> configured to filter the fourth light <NUM>, thereby to generate a fifth light <NUM>; and second projection optics <NUM> configured to receive the fifth light <NUM> and project it as a sixth light <NUM> onto a screen <NUM>. The DMD <NUM> may be the same as or similar to the DMD <NUM> illustrated in FIGS. The first projection optics <NUM> may include at least one lens configured to spatially Fourier transform the third light <NUM> onto a plane (also referred to as the Fourier plane). The filter <NUM> may be a Fourier aperture (also referred to as a Fourier filter); that is, an aperture located at or near the plane at which a Fourier transform of an object is formed. Micromirrors and gaps of DMD <NUM> may cooperate to form a two-dimensional grating that diffracts input light. Therefore, modulated light propagating away from DMD <NUM> may form a plurality of diffraction orders observable as a Fraunhofer diffraction pattern in a far-field region of DMD <NUM> or at a focal plane of a lens. Each diffraction order corresponds to one light beam propagating away from DMD <NUM> in a unique respective direction. By design, most of the optical power of modulated light from DMD <NUM> may be in the zeroth diffraction order.

While <FIG> illustrates the first projection optics <NUM>, the filter <NUM>, and the second projection optics <NUM> as separate entities, in some implementations the filter <NUM> may be incorporated as part of a larger optical system including the first projection optics <NUM> and the second projection optics <NUM>. Various elements of the projection system <NUM> may be operated by or under the control of a controller <NUM>; for example, one or more processors such as a central processing unit (CPU) of the projection system <NUM>. As illustrated in <FIG>, the light source <NUM> and the DMD <NUM> are controlled by the controller <NUM>. In some implementations, the controller <NUM> may additionally or alternatively control other components of the projection system <NUM>, including but not limited to the illumination optics <NUM>, the first projection optics <NUM>, and/or the second projection optics <NUM>. In one particular example, the controller <NUM> may control components of the illumination optics <NUM> to ensure the second light <NUM> is incident on the DMD <NUM> at the appropriate location and/or angle.

In 3D or 3D-capable projection implementations, a physical projector may include two projection systems <NUM> disposed side-by-side, with each individual projection system <NUM> projecting an image corresponding to one eye of the viewer. Alternatively, a physical projector may utilize one combined projection system <NUM> to project individual images corresponding to both eyes of the viewer.

In practical implementations, the projection system <NUM> may include fewer optical components or may include additional optical components such as mirrors, lenses, waveguides, optical fibers, beam splitters, diffusers, and the like. With the exception of the screen <NUM>, the components illustrated in <FIG> may be integrated into a housing to provide a projection device. Such a projection device may include additional components such as a memory, input/output ports, communication circuitry, a power supply, and the like.

The light source <NUM> may be, for example, a laser light source, an LED, and the like. Generally, the light source <NUM> is any light emitter which emits coherent light. In some aspects of the present disclosure, the light source <NUM> may comprise multiple individual light emitters, each corresponding to a different wavelength or wavelength band. The light source <NUM> emits light in response to an image signal provided by the controller <NUM>. The image signal includes image data corresponding to a plurality of frames to be successively displayed. The image signal may originate from an external source in a streaming or cloud-based manner, may originate from an internal memory of the projection system <NUM> such as a hard disk, may originate from a removable medium that is operatively connected to the projection system <NUM>, or combinations thereof.

Although <FIG> illustrates a generally linear optical path, in practice the optical path is generally more complex. For example, in the projection system <NUM>, the second light <NUM> from the illumination optics <NUM> is steered to the DMD chip <NUM> (or chips) at a fixed angle, determined by the steering angle of the DMD mirrors.

To counteract the effects of overlap caused by pixel-shifting as noted above, the design of the first projection optics <NUM>, the filter <NUM>, and/or the second projection optics <NUM> may be modified. Preferably, the configuration of the filter <NUM> is particularly selected to counteract such effects. To illustrate the effects on the image of the filter configuration, <FIG> shows an exploded view an exemplary projection lens system <NUM> according to various aspects of the present disclosure. The projection lens system <NUM> is one example of the combination of the first projection optics <NUM>, the filter <NUM>, and the second projection optics <NUM> illustrated in <FIG>. In some aspects of the present disclosure, the performance of the complete projection lens system <NUM> meets Digital Cinema Initiatives (DCI) image specifications; for example, the DCI Digital Cinema System Specification (DCSS) Version <NUM> or newer.

The projection lens system <NUM> includes first projection optics <NUM> configured to form a Fourier transform of an object at an exit pupil thereof as will be described in more detail below (also referred to as a Fourier part or a Fourier lens assembly), an filter <NUM>, and second projection optics <NUM> (also referred to as a zoom part or a zoom lens assembly). The first projection optics <NUM>, the filter <NUM>, and the second projection optics <NUM> may respectively correspond to the first projection optics <NUM>, the filter <NUM>, and the second projection optics <NUM> illustrated in <FIG> As used herein, "Fourier part" or "Fourier lens assembly" refers to an optical system that spatially Fourier transforms modulated light (e.g., light from the DMD <NUM>) by focusing the modulated light onto a Fourier plane. The first projection optics <NUM> and the filter <NUM> collectively operate as a Fourier lens with a spatial filter that may also be used as a fixed throw projection lens. The spatial Fourier transform imposed by the first projection optics <NUM> converts the propagation angle of each diffraction order of the modulated light to a corresponding spatial position on the Fourier plane. The first projection optics <NUM> 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. Both the first projection optics <NUM> and the second projection optics may include a plurality of individual lens elements.

To allow access to the Fourier aperture when setting up the projection system <NUM> and/or to allow the filter <NUM> to be interchangeable, the projection lens system <NUM> may have a modular design. In such instances, the first projection optics <NUM> may be provided with a first attachment part <NUM> and the second projection optics <NUM> may be provided with a second attachment part <NUM>. The first attachment part <NUM> and the second attachment part <NUM> may include complementary mating fasteners such as screws, threads, pins, slots, and the like. In other implementations, the housings for the first projection optics <NUM> and the second projection optics <NUM> may be integral.

The filter <NUM> is configured to block a portion of light and to transmit a portion of the light (e.g., to transmit modulated light corresponding to at least one diffraction order) in the projection lens system <NUM>. In some implementations, the diffraction order transmitted by the filter <NUM> may be a unitary diffraction order (i.e., the entirety of the transmitted order); alternatively, the diffraction order transmitted by the filter <NUM> may be an aggregate diffraction order (i.e., a part of one order and a complementary part from another order or orders). As illustrated in <FIG>, the filter <NUM> has a square opening having sides of, for example, <NUM> in length. <FIG> also illustrates an optical axis <NUM> of the projection lens system <NUM>. When assembled, the first projection optics <NUM> and the second projection optics are substantially coaxial with one another and with the optical axis <NUM>. In some implementations (for example, depending on the illumination angle), the filter <NUM> is further substantially coaxial with the optical axis <NUM>.

The projection lens system <NUM> 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 filter <NUM> may block, and thus absorb, approximately <NUM>% or more of incident light and therefore the heat sink or cooling fins may be positioned and configured so as to appropriately dissipate heat from the filter <NUM>. In some implementations, the filter <NUM> is thermally isolated from other parts of the projection lens system <NUM>.

While <FIG> illustrates the opening of the filter <NUM> as having a square shape, the present disclosure is not so limited. In some implementations, the filter <NUM> may have a differently-shaped opening, such as a circle, an ellipse, a rounded square, a rectangle, a rounded rectangle, a hexagon, a rounded hexagon, a pincushion, and the like, so long as the shape is dimensioned to cover an appropriate angular passband. The appropriate angular passband may be approximately <NUM>%-<NUM>% of a size of a (e.g., zeroth, first, second, etc.) diffraction order in the Fourier plane; for example, approximately <NUM>%. In some implementations, the dimensions and shape of the opening of the filter <NUM> may be particularly selected such that, when utilized with a pixel-shifting method, the operation of the projector is enhanced. For example, because the filter <NUM> acts as a Fourier filter, it has an effect on which angular frequency components from the DMD are displayed on a screen. Thus, modifications to the opening of the filter <NUM> result in changes to the size and/or shape of the pixels displayed on the screen. In one example, the size of the pixels can effectively be reduced such that they are smaller on the screen than the projected size of the physical mirrors of the DMD. When combined with a pixel-shifting technique, this may create higher resolution images. To achieve this, the light source of the projection system (e.g., the light source <NUM> illustrated in <FIG>) is selected to have sufficiently high coherence and low etendue to employ Fourier filtering effectively. Thus, the light sources may be laser light sources.

The effects of the dimensions and shape of the filter aperture are illustrated in <FIG>. <FIG> illustrates the effects of pixel-shifting with no filter (or with a filter having a large aperture), assuming adequate illumination by the light source. In <FIG>, the aperture <NUM> is superimposed on a plurality of diffraction orders <NUM>. The aperture <NUM> may correspond to the projection lens aperture (e.g., of a projection lens in the first projection optics <NUM> illustrated in <FIG>) or, in the case where a Fourier filter having a large aperture is used, to the opening of the Fourier filter (e.g., of the filter <NUM> and/or the filter <NUM> illustrated in <FIG>). Diffraction orders <NUM> which are all or mostly blocked are illustrated using dashed lines, and diffraction orders <NUM> which are all or mostly transmitted are illustrated using solid lines.

<FIG> corresponds to a particular example in which the light emitted from the light source has a wavelength of <NUM>, the illumination angle of the light incident on the DMD (e.g., the angle of the input light <NUM> illustrated in <FIG>, measured relative to the normal of a micromirror in the unactuated or neutral position) is <NUM>°, the on-position angle of the mirrors of the DMD (e.g., the angle of the surface of the micromirror <NUM> in the on state illustrated in <FIG>, measured relative to the plane of the substrate <NUM>) is <NUM>°, the off-position angle of the mirrors of the DMD (e.g., the angle of the surface of the micromirror <NUM> in the off state illustrated in <FIG>, measured relative to the plane of the substrate <NUM>) is -<NUM>°, the width of the mirrors of the DMD (e.g., the width <NUM> illustrated in <FIG>) is <NUM>, and the gap between the mirrors of the DMD (e.g., the width <NUM> illustrated in <FIG>) is <NUM>.

<FIG> illustrates the effects of pixel-shifting with a particularly-sized filter having a square aperture of a size (e.g., being of a diameter or height and/or width, or area) that is <NUM>% of a size of a diffraction order (e.g., of a respective diameter or height and/or width, or area, of a zeroth or higher diffraction order), assuming adequate illumination by the light source. In <FIG>, the aperture <NUM> is superimposed on a plurality of diffraction orders <NUM>. The aperture <NUM> may correspond to the opening of the Fourier filter (e.g., of the filter <NUM> and/or the filter <NUM> illustrated in <FIG>). Diffraction orders <NUM> which are blocked are illustrated using dashed lines, and the diffraction order <NUM> which is transmitted is illustrated using solid lines. As shown in <FIG>, aperture <NUM> passes light from a diffraction order <NUM> that is illustrated using solid lines and that corresponds to a zeroth diffraction order.

<FIG> corresponds to the same projection system parameters as <FIG>; that is, the particular example in which the light emitted from the light source has a wavelength of <NUM>, the illumination angle of the light incident on the DMD (e.g., the angle of the input light <NUM> illustrated in <FIG>, measured relative to the normal of a micromirror in the unactuated or neutral position) is <NUM>°, the on-position angle of the mirrors of the DMD (e.g., the angle of the surface of the micromirror <NUM> in the on state illustrated in <FIG>, measured relative to the plane of the substrate <NUM>) is <NUM>°, the off-position angle of the mirrors of the DMD (e.g., the angle of the surface of the micromirror <NUM> in the off state illustrated in <FIG>, measured relative to the plane of the substrate <NUM>) is -<NUM>°, the width of the mirrors of the DMD (e.g., the width <NUM> illustrated in <FIG>) is <NUM>, and the gap between the mirrors of the DMD (e.g., the width <NUM> illustrated in <FIG>) is <NUM>.

In <FIG>, because many diffraction orders, amounting to a large portion of the DMD angular Fourier spectrum, are captured by the lens, many of the high-spatial-frequency details (e.g., mirror edges) are reproduced on the screen, resulting in square pixels corresponding to the size of the mirrors in the physical device. In <FIG>, the filter corresponds to capturing the central lobe of the mirror diffraction (i.e., a sinc function) cloud. Because the pass-band of the filter in <FIG> is reduced compared to the system in <FIG>, high angular frequencies will not be transmitted. As the pass-band of the filter becomes smaller, sharp details such as the edges of the mirrors will be lost and, at one particular point shown in <FIG>, only the image content frequencies will be allowed to pass. If the size of the opening of the filter is further reduced, the filter will begin to low-pass image content, which may result in image blurring on the screen. The effects of the particular size of the opening is illustrated in <FIG>.

Each of <FIG> illustrate a single pixel projected by a projection system having the same characteristics and components, except that in each illustration the size of the filter aperture is different. Moreover, each of <FIG> are presented on the same scale. In <FIG>, the filter has a square aperture that is <NUM>% of a diffraction order in size; in <FIG>, the filter has a square aperture that is <NUM>% of a diffraction order in size; and in <FIG>, the filter has a square aperture that is <NUM>% of a diffraction order in size. Compared to <FIG> does not exhibit unwanted high-spatial-frequency details. Compared to <FIG> is brighter in the middle and dimmer towards the corner of the mirror. <FIG> illustrates the point at which the image data and nothing else passes through the filter. When combined with a pixel-shift technique, the smaller pixel of <FIG> has less overlap. Thus, according to the invention, in a projection system which includes a Fourier filter and utilizes a pixel-shift technique, the filter has a square filter that is approximately <NUM>%-<NUM>% of a diffraction order in size, and most preferably has a square filter that is approximately <NUM>% of a diffraction order in size.

One particular implementation of a pixel-shift technique in a projection system having a Fourier filter, such as the projection system <NUM> illustrated in <FIG>, is illustrated in <FIG>. The method <NUM> of <FIG> may be performed by the controller <NUM> of <FIG>, and may be implemented using hardware, software, firmware, or combinations thereof. In some examples, the method <NUM> is implemented as instructions stored in a non-transitory computer-readable medium, such as a hard disk or other storage medium contained in or associated with the projection system <NUM>.

In the method <NUM>, a series of images are displayed using image data which includes a series of frames. The image data is divided into a plurality of frame periods each corresponding to the duration T of a frame; for example, a <NUM> display has a frame period T of (<NUM>/<NUM>) sec. At operation <NUM>, the frame period is divided into N subperiods, with N being an integer larger than <NUM>. Preferably, N is four to implement a pixel-shifting pattern similar to that illustrated in <FIG>; however, in other implementations N may be six or another number other than four. At operation <NUM>, a counter I is initialized to <NUM>. Subsequently, at operation <NUM>, an image is projected through the filter aperture for the Ith subperiod. Operation <NUM> may include sub-operations, such as causing a light source of the projection system to emit light, controlling the spatial light modulator (e.g., the DMD <NUM> of <FIG>) to modulate the light and form the image, and so on. This image is maintained for a duration of T / N. In the example of a <NUM> display using four subperiods per frame, this subperiod duration is (<NUM>/<NUM>) sec.

At the end of the subperiod at operation <NUM>, the counter I is compared to N to determine if the subperiod is the last subperiod of the frame. If the counter I does not equal N, at operation <NUM> the counter I is incremented by <NUM> and at operation <NUM> the pixels are shifted. In the example where four subperiods are provided per frame and the pixel-shifting follows a square pattern as in <FIG>, this corresponds to a half-pixel shift. Alternatively, four subperiods may be provided per frame and the pixel-shifting may follow a diamond or rectangle pattern; six subperiods may be provided per frame and the pixel-shifting may follow a rectangle or hexagon pattern; three subperiods may be provided per frame and the pixel-shifting may follow a triangle pattern; two subperiods may be provided per frame and the pixel-shifting may follow a linear (back-and-forth) pattern; and so on. In some implementations, the number of subperiods may be on the order of tens (or greater) and the pixel-shifting may approximate a circular pattern or a complex shape. Thereafter, operation <NUM> is repeated for the next subperiod until the time when the counter I is equal to N. At this point, at operation <NUM> the frame is incremented and the method <NUM> returns to operation <NUM>. Operations <NUM> through <NUM> are repeated for the duration of image display, and may continue until the endpoint of the media content has been reached, an operation issues a pause or stop instruction, and so on.

When a pixel-shifting technique is combined with the filter, the effects of the particular size of the opening are illustrated in <FIG>. <FIG> illustrate the results of a first image test using a checkerboard pattern, and <FIG> illustrate the results of a second image test using a resolution chart.

<FIG> shows the input image for the first image test, which is a full-resolution <NUM> checkerboard pattern shown in close-up. <FIG> shows the result (i.e., the output image) for a projection system which implements a four-subperiod pixel-shifting technique (as shown in <FIG>) but which does not include a Fourier aperture, such as the filter <NUM> of <FIG> or the filter <NUM> of <FIG>. <FIG> shows the result for a projection system which implements a four-subperiod pixel-shifting technique and which includes a Fourier aperture having an opening that is <NUM>% of the diffraction order in size. In <FIG>, the black squares of the checkerboard are indistinguishable from the white squares, as all squares appear to be substantially the same grayish color. In <FIG>, however, the squares of the checkerboard are distinguishable from one another. While the modulation amplitude is not as high as it would be if the projection system used a native full-resolution modulator, the combination of pixel-shifting and the particularly-sized aperture allows for the reproduction of high-resolution details using a lower-resolution modulator. As can be seen by comparing <FIG>, the pixel-shifting technique alone, without the further implementation of the aperture, cannot reproduce such details.

<FIG> shows the input image for the second image test, which is a renormalized quantized resolution chart shown in close-up. <FIG> shows the result for a projection system which implements a four-subperiod pixel-shifting technique and which includes a Fourier aperture having an opening that is <NUM>% of the diffraction order in size. <FIG> shows the result for a projection system which implements a four-subperiod pixel-shifting technique and which includes a Fourier aperture having an opening that is <NUM>% of the diffraction order in size. In practice, the large opening used to project the image in <FIG> is analogous to having no filter at all, as can be seen by comparing the artifacts in <FIG> to similar ones in <FIG>. As such, the lines in the resolution pattern are not resolved in <FIG>. In <FIG>, however, the lines are resolved even in the close-up view.

By comparing <FIG> and <FIG> with <FIG> and <FIG> and in view of <FIG>, it can be seen that the effects of pixel-shifting and the particularly-sized aperture opening (and in particular, the ability to properly render a high-resolution image using a lower-resolution modulator) are unexpectedly greater than merely the sum of pixel-shifting alone and a Fourier aperture alone.

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.

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.

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.

Claim 1:
A projection system, comprising:
a light source (<NUM>) including at least one laser configured to emit input laser light;
a spatial light modulator (<NUM>) configured to receive the input laser light and generate modulated laser light, wherein the modulated laser light comprises a plurality of diffraction orders generated by the input laser light being diffracted by the spatial light modulator;
a lens (<NUM>) configured to Fourier transform the modulated laser light and focusing the modulated laser light as Fourier-transformed by the lens onto a Fourier plane;
a filter (<NUM>) for spatially filtering in the Fourier plane the modulated laser light as Fourier-transformed by the lens, configured to transmit at least one diffraction order of the modulated laser light as Fourier-transformed by the lens and to block a remaining portion of the modulated laser light as Fourier-transformed by the lens; and
a controller (<NUM>) for controlling the spatial light modulator, configured to:
for each of a plurality of subperiods, cause the spatial light modulator to project an image through the lens and the filter, and
between each of the plurality of subperiods, cause the spatial light modulator to shift the position of an image to be projected by the spatial light modulator by a partial pixel distance,
wherein the filter is configured to transmit at least a zeroth diffraction order of the modulated laser light as Fourier-transformed by the lens, and
wherein the filter includes an aperture for passing the at least one diffraction order transmitted by the filter, wherein a size of the aperture is between <NUM>% and <NUM>% of a size of the zeroth diffraction order of the modulated laser light in the Fourier plane.