High contrast imaging using multi-path projection systems

Abstract

Multi-path projection systems and methods of control for the same. One example projection system includes a first light source configured to emit a first light and a second light source configured to emit a second light. The projection system includes a PLM configured to receive the second light and steer the second light as a modulated light. The projection system also includes a DLP configured to receive the first light and the modulated light. The DLP is configured to modulate received light to generate an image. When the image has an APL value below an APL threshold, the first light source is controlled to an off state and the second light source is controlled to emit the second light. When the image has an APL value above or equal to the APL threshold, both the first light source and the second light source are controlled to emit light.

Description

HIGH CONTRAST IMAGING USING MULTI-PATH PROJECTION SYSTEMSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority from U.S. Provisional Application No. 63 / 670,287, filed on 12 July 2024, and European Patent Application No. 24194883.5, filed on 16 August 2024, each of which is incorporated by reference herein in its entirety.BACKGROUND1. Field of the Disclosure

[0002] This application relates generally to projection systems and, particularly, to multi-path projection systems and control thereof.2. 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.BRIEF SUMMARY OF THE DISCLOSURE

[0004] Dual-path modulation projection systems described herein provide for improved perceived contrast over traditional projection systems. Typical dual-path modulation projection systems include two optical paths. The first optical path resembles a standard single modulation projector where a first light source (e.g., a first laser) projects light onto a digital light processor (DLP) device. The second optical path may be a light-steering dual-modulation stage that improves the contrast of the light-steering path. For example, a second light source (e.g., a second laser) projects light onto a PLM. The PLM modulates the light from the second light source and directs it to the DLP device, adding to the light from the first light source.

[0005] Various aspects of the present disclosure improve upon dual-path modulation projection systems by controlling the two optical paths based on an average picture level (APL) of projected images. For example, for low APL images, only the second light source is controlled to emit light and the desired contrast is fully achieved by the PLM and the DLP. For high APL images, the first light source is also controlled to emit light, adding to the light from the second light source andincreasing the achieved luminance of the projected image. In some instances, the light sources are modulated to vary the luminance of the light projected by the light sources, adding an additional layer of possible contrast.

[0006] In one aspect of the present disclosure, there is provided a dual-modulation laser projection system comprising a first light source configured to emit a first light and a second light source configured to emit a second light. The projection system includes a PLM configured to receive the second light from the second light source and steer the second light as a modulated light. The projection system also includes a DLP configured to receive the first light from the first light source and configured to receive the modulated light from the PLM. The DLP is configured to modulate received light to generate an image. When the image has an APL value below an APL threshold, the first light source is controlled to an off state and the second light source is controlled to emit the second light. When the image has an APL value above or equal to the APL threshold, the first light source is controlled to emit the first light and the second light source is controlled to emit the second light.

[0007] In another aspect of the present disclosure, there is provided a method for controlling a dualmodulation laser projection system, wherein the projection system includes a first optical path comprising a first light source and a DLP, and wherein the projection system includes a second optical path comprising a second light source, a PLM, and the DLP. The method includes determining, based on image data, an APL value of an image to be projected, controlling, in response to the APL value of the image being below an APL threshold, the second light source to project a second light along the second optical path while maintaining the first light source in an off state, and controlling, in response to the APL value of the image being greater than or equal to the APL threshold, the first light source to project a first light along the first optical path and the second light source to project the second light along the second optical path.

[0008] In another aspect of the present disclosure, there is provided a non-transitory computer- readable storage medium storing a program comprising instructions that, when executed by a processor, cause the processor to carry out a method including determining, based on image data, an APL value of an image to be projected, controlling, in response to the APL value of the image being below an APL threshold, the second light source to project a second light along the second optical path while maintaining the first light source in an off state, and controlling, in response to the APL value of the image being greater than or equal to the APL threshold, the first light source to project afirst light along the first optical path and the second light source to project the second light along the second optical path.

[0009] 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

[0010] 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:

[0011] FIGS. 1A-1B illustrate block diagrams of example single path display systems according to various aspects of the present disclosure.

[0012] FIG. 2 illustrates a schematic diagram of an example dual-path projection system according to various aspects of the present disclosure.

[0013] FIG. 3 illustrates a block diagram of an example dual-path projection system according to various aspects of the present disclosure.

[0014] FIG. 4 illustrates a graph of image contrast achieved by example projectors.

[0015] FIG. 5 illustrates a graph representing the contrasts of example projectors within both theoretically ideal environments and realistic environments.

[0016] FIG. 6 illustrates a block diagram of another example dual-path projection system according to various aspects of the present disclosure.

[0017] FIG. 7 illustrates another view of the graph of FIG. 5.

[0018] FIG. 8 illustrates a block diagram of yet another example dual-path projection system according to various aspects of the present disclosure.

[0019] FIG. 9A illustrates a plan view of an example light modulator for use with various aspects of the present disclosure.

[0020] FIG. 9B illustrates a cross-sectional view taken along the line I-B of FIG. 9A.

[0021] FIG. 10 illustrates a plan view of an example phase light modulator for use with various aspects of the present disclosure.

[0022] FIG. 11 illustrates a cross-sectional view of another example phase light modulator for use with various aspects of the present disclosure.

[0023] FIG. 12 illustrates a block diagram of a controller for use with various aspects of the present disclosure.

[0024] FIG. 13 illustrates a block diagram of an example method performed by the controller of FIG. 12.DETAILED DESCRIPTION

[0025] 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.

[0026] 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.

[0027] 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.

[0028] Many display device architectures consist of a single light path. FIGS. 1A-1B illustrate block diagrams of example single path display systems according to various aspects of the present disclosure. FIG. 1 A provides an example single path projector system 100. The projector system100 includes a light source 102, such as a lamp, that emits a light 104 onto a digital light processor (DLP) 106. The DLP 106 modulates the light 104 to generate an image 108. In the example projector system 100, the light 104 has 48 nits of luminance and the DLP 106 has a contrast of 2000: 1. Accordingly, the projector system 100 can produce any image 108 that has a luminance between 48 nits and 48 / 2000 nits (or 0.024 nits).

[0029] FIG. IB provides an example computer display system 120, such as a computer monitor. The computer display system 120 includes a backlight 122 that emits a light 124 onto a liquid crystal display (LCD) 126. The LCD 126 generates an image 128 using the light 124. In the example computer display system 120, the light 124 has 100 nits of luminance and the LCD has a contrast of 800: 1. Accordingly, the computer display system 120 can produce any image 128 that has a luminance between 100 nits and 100 / 800 nits (or 0.125 nits).

[0030] However, single path display systems have a limit on the achievable contrast and black level that has been improved by display systems that implement two paths of light. Projection display systems described herein may include a projector path and a light steering path. In some instances, the projector path includes a first light source that has a relatively low peak luminance and may be used to project a full image. The light steering path includes a second light source that projects concentrated light to boost luminance at particular locations of the image, such as boosting luminance of highlights.

[0031] FIG. 2 illustrates a schematic diagram of an example dual-path projection system 200 according to various aspects of the present disclosure. The projection system 200 includes a first projector 202 having a lens 204 that projects an image 206 onto a screen 208. The screen 208 may be a front-projection screen or a rear-projection screen. The projection system 200 further includes a second projector 210 having a lens 212 which projects an image 206A onto the screen 208.Images 206 and 206A are superposed so that a viewer sees an image resulting from the combination of images 206 and 206A.

[0032] The first projector 202 may comprise, for example, a DLP-based projector, a projector which uses one or more liquid crystal on silicon (LCOS) spatial light modulators, a projector comprising a transmissive LCD panel to modulate light, a cathode ray tube (CRT) projector, or the like.

[0033] The second projector 210 is a projector which can deliver concentrated light to at least some areas within the area of the image 206, preferably without significantly raising the light level inother areas within the image 206. For example, the second projector 210 may comprise one or more scanning beams which can be directed to add further illumination to only selected highlight areas of image 206. The first projector 202 and the second projector 210 may be co-registered such that the second projector 210 can accurately deliver additional light to small highlight areas within the image 206 projected by the first projector 202. As light can be delivered by the second projector 210 to add to highlight areas, light can also be moved away from particular areas by the second projector 210 to lower the luminance and improve the black level in areas within the image 206. In some embodiments, the second projector 210 has a spatial resolution equal to or greater than that of the first projector 202. In other embodiments, the second projector 210 has a spatial resolution less than the first projector 202.

[0034] In the example projection system 200, the optical paths of the first projector 202 and the second projector 210 are independent up until the point at which they are combined on the screen 208. However, in other instances as will be described further, the optical paths of the first projector 202 and the second projector 210 may be only partially independent or may be shared.Additionally, the example projection system 200 illustrates two separate projectors (e.g., the first projector 202 and the second projector 210) having separate housings. However, dual-path projection may occur in projectors having only a single housing. For example, a single projector housing may store more than one light sources configured to project light independently. The light is combined prior to projection onto a screen. In other examples, the single projector housing may include two light outputs such that the light is combined on the screen.

[0035] FIG. 3 illustrates a block diagram of an example dual-path projection system 300 according to various aspects of the present disclosure. The projection system 300 includes a first laser 302, a second laser 304, a phase light modulator (PLM) 306, and a DLP 308. The first laser 302 projects a first light 303 onto the DLP 308. In some instances, the first laser 302 includes global dimming such that a luminance level of the first light 303 is modulated. The second laser 304 projects a second light 305 onto the PLM 306. The PLM 306 modulates the second light 305 and generates a modulated light 307 that is directed to the DLP 308. The DLP 308 receives the first light 303 and the modulated light 307, which are combined at the DLP 308. The DLP 308 modulates the combined first light 303 and modulated light 307 to generate an image 310.

[0036] The projection system 300 can be considered as having two optical paths: a first optical path comprising the first laser 302 and the DLP 308, and a second optical path comprising the secondlaser 304, the PLM 306, and the DLP 308. The first optical path is similar to that of a single-path projector system, such as the single path projector system 100 of FIG. 1A. The second optical path may be a light-steering dual-modulation optical path that improves the contrast of the image 310.

[0037] In embodiments described herein, the first optical path may be implemented as a standalone projector, where global dimming of the first laser 302 is implemented for lower average picture level (APL) images up until global dimming is at its maximum level (e.g., the first light 303 has its maximum luminance). For images above the maximum APL of the first optical path, the second optical path is implemented to boost the light where needed. While the system is less sensitive to PLM light field errors when operating in this manner, significant performance limitations are imposed for high contrast imaging. When dark images (for example, low APL images) are to be achieved, the first optical path is implemented and the first laser 302 is dimmed. However, consider a low APL image such as a star field image that includes bright stars. The global dimming of the first laser 302 is reduced in accordance with the APL to achieve the low black level that dominates the image, but the brightness of the stars is limited.

[0038] To further illustrate this issue, FIG. 4 illustrates a graph 400 of image contrast achieved by example projectors. In the graph 400, the y-axis represents the input APL level of images. The x- axis represents the input maximum contrast of the images. The graph illustrates global dimming solutions for both a 12,000,000: 1 contrast projector and an example global dimming projector. The example global dimming projector has a modulation-stage contrast Pcrof 30,000: 1 and a dimming ratio Ger of 1 :48. As seen in the graph 400, the simultaneous contrast of the global dimming projector is limited to the contrast of the modulator (e.g., 30,000: 1).

[0039] Additionally, projector architecture contrast and the contrast actually perceived by human observers in a given environment are not the same. Viewing environments often have additional components, such as seating and curtains, that reflect light onto a viewing screen. Such reflections limit the perceivable contrast. FIG. 5 illustrates a graph 500 representing the contrasts of example projectors within both theoretically ideal environments and realistic viewing environments. The x- axis of the graph 500 represents APL values on a logarithmic scale, where 10° represents an image at 100% APL. The y-axis of the graph 500 represents the contrast value for the given APL value. The graph 500 includes a first function 502, a second function 504, a third function 506, and a fourth function 508. The first function 502 represents the achieved contrast of a 12,000,000: 1 contrast projector over a plurality of APL values in a theoretically ideal environment. The second function504 represents the achieved contrast of an approximately 1,000,000: 1 contrast projector over a plurality of APL values in a theoretically ideal environment. The third function 506 represents the achieved contrast of a theoretically ideal (infinity: 1 contrast), 108 nit projector in a viewing environment. The fourth function 508 represents the achieved contrast of an approximately 1,000,000:1 contrast projector in the same viewing environment.

[0040] As shown by the third function 506, when placed in a realistic environment, the theoretically ideal, 108 nit projector does not nearly achieve a contrast near infinity: 1. In fact, a 1,000,000: 1 projector at low APL approximately the same perceivable contrast as the theoretically ideal projector.

[0041] Accordingly, embodiments described herein overcome these limitations such that both small bright objects and low black levels are achieved within images in dual-path projection systems. Embodiments described herein also achieve nearly-ideal contrast for projectors within realistic viewing environments.

[0042] FIG. 6 illustrates a block diagram of an example dual-path projection system 600 according to various aspects of the present disclosure. The projection system 600 includes a first laser 602, a second laser 604, a PLM 606, and a DLP 608. The first laser 602 emits a first light 603 onto the DLP 608. In some instances, the first laser 602 includes global dimming such that a luminance level of the first light 603 is modulated. The first light 603 has a maximum luminance value of A nits. The second laser 604 emits a second light 605 onto the PLM 606. In the example projection system 600, the second laser 604 does not include global dimming. Accordingly, the second light 605 has a constant luminance value of B nits. The PLM 606 modulates the second light 605 and generates a modulated light 607 that is directed to the DLP 608.

[0043] An optical filter 610 may be situated between the PLM 606 and the DLP 608 to filter undesired light from the image generated by the PLM 606. For example, the optical filter 610 may be configured to at least partially block unmodulated light reflected from the PLM 606, such as reflected from a transparent cover of the PLM 606. Further details regarding the optical filter 610 can be found in U.S. Patent No. 10,698,302, “Spatial Light Modulator For Reduction Of Certain Order Light”, incorporated herein in its entirety. Light modulated by the PLM 606 is either directed through the optical filter 610 to the DLP 608 or is directed to a light dump 612. For example, a firstportion 607 A of the modulated light 607 is directed to the light dump 612. The modulated light 607 that is directed to the optical filter 610 becomes filtered light 609 that is received by the DLP 608.

[0044] The DLP 608 receives the first light 603 and the filtered light 609, which are combined at the DLP 608. The DLP 608 modulates the combined first light 603 and filtered light 609 to generate an image 614.

[0045] In some examples, the first laser 602 is capable of emitting first light 603 having a maximum luminance of 48 nits. With global dimming, the first laser 602 is capable of 48:1 attenuation. Additionally, the DLP 608 may have a modulation-stage contrast of 30,000:1. The PLM 606 may provide a black level of approximately B / 24. These attenuation values are merely examples, and laser sources, PLMs, and DLPs described herein may have other attenuation values.

[0046] Referring back to the second function 504 within the graph 500 of FIG. 5, the desired contrast is achieved by the 30,000: 1 DLP 608 for the upper 92% (A < 99 nits) of the APL range. The lowest projector black level desired (the leftmost point on the second function 504) may be satisfied by the contrast of the second laser 604, the PLM 606, and the DLP 608 operating without the first laser 602 (as long as B < 75 nits). Accordingly, for relatively low APL values, the projection system 600 may operate the second laser 604 to emit the second light 605 while keeping the first laser 602 off.

[0047] For example, consider a maximum laser utilization efficiency of A + B = 108 nits where B = 27 nits (25% APL) and A = 81 nits (75% APL). Additionally, consider that the first laser 602 combined with the DLP 608 defines a first optical path. The second laser 604 and the PLM 606 combined with the DLP 608 defines a second optical path. Beginning with a full black image, the second optical path alone is capable of creating the image. The use of the second optical path alone (e.g., the first laser 602 maintained off and the second laser 604 emitting light) provides for the creation of all images up to, for example, 25% APL with both the desired black level and peak luminance capabilities of the second optical path. When the desired image is above 25% APL (e.g., an APL threshold), the first laser 602 may be controlled to emit light in addition to the second laser 604. The global dimming of the first laser 602 may be controlled such that the luminance of the first laser 602 is a minimum luminance value for images right above the APL threshold (for example, the first light 603 has a luminance of 1 nit for an image at 26% APL). The global dimming of the first laser 602 may then increase (for example, linearly) for increasing APL values (for example, the firstlight 603 has a luminance of 10 nits for 40% APL, has 20 nits for 55% APL, up to 48 nits, or a maximum luminance value, for 100% APL). In this manner, the global dimming is increased to address the upper portion of the APL range without any perceptually detectable reduction in black performance level. The peak highlight capability is always available, regardless of APL.

[0048] FIG. 7 illustrates another view of the graph 500 of FIG. 5. In the example of FIG. 7, the target projector is the projection system 600 where the DLP 608 is capable of 30,000:1 attenuation. Accordingly, the second optical path is capable of creating all images below APL threshold 700 (e.g., approximately 90% APL). Therefore, only the second laser 604 is controlled to emit the second light 605 for images below 90% APL and the first laser 602 is maintained off. For images above the APL threshold 700, both the first laser 602 and the second laser 604 are controlled to emit light. These APL threshold values are merely examples, and in practice the APL threshold value may vary for different viewing environments.

[0049] In some implementations, the first laser 602 and the second laser 604 emit light of differing etendue values. Etendue is a measurement of the effective spatial and angular size of a light source, and is related to terms such as mm2*sr (steradians), M2factor, or beam parameter product (BPP). For projection systems based on beam steering, the smallest focused spot size (or pixel) of the projected image is dependent on the etendue level. In this manner, the spot size increases with etendue, and high etendue results in a low image quality (e.g., halos around bright objects, reduced maximum brightness, etc.).

[0050] When a fiber-coupled laser is used as the first laser 602 and / or the second laser 604, the etendue is based on the fiber radius and solid angle at the fiber output, as provided in Equation 1 :[Equation 1]Where:G = Etendue;Rfiber = Fiber Radius; and fiber = Solid Angle of the Fiber Output.

[0051] The solid angle at the fiber output is dependent on the numerical aperture of the fiber, as provided in Equation 2:[Equation 2]Where:NA = Numerical Aperture of the Fiber

[0052] In some instances, the first laser 602 and the second laser 604 emits lights (e.g., the first light 603 and the second light 605, respectively) that have different etendue values. For example, the first light 603 emitted by the first laser 602 may have a relatively higher etendue value than the second light 605 emitted by the second laser 604. Accordingly, the first laser 602 may be a high etendue light source and the second laser 604 may be a low etendue light source. In this manner, for images having low APE (e.g., below the APL threshold), the low etendue light source is implemented. For images having high APL (e.g., above or equal to the APL threshold), the high etendue light source is implemented in addition to the low etendue light source.

[0053] FIG. 8 illustrates a block diagram of yet another example dual-path projection system 800 according to various aspects of the present disclosure. The projection system 800 includes a first laser 802, a second laser 804, a PLM 806, and a DLP 808. The first laser 802 emits a first light 803 onto the DLP 808. The first light 803 has a maximum luminance value of A nits. The second laser 804 emits a second light 805 onto the PLM 806. The second light 805 has a maximum luminance value of B nits. In the example projection system 800, both the first laser 802 and the second laser804 include global dimming such that the luminance of both the first light 803 and the second light805 is modulated. Both A and B may have a value of, for example, 48 nits. In other examples, A + B = 108 nits. The PLM 806 modulates the second light 805 and generates a modulated light 807 that is directed to the DLP 608. The projection system 800 may include an optical filter 810 between the PLM 806 and the DLP 808 that filters the modulated light 807, thereby generating a filtered light 809 that is received by the DLP 808. The DLP 808 receives the first light 803 and the filtered light 809, which are combined at the DLP 808. The DLP 808 modulates the combined first light 803 and filtered light 809 to generate an image 814.

[0054] In the example projection system 800, the PLM 806 does not direct light to a light dump, but rather creates the desired image shape by allocating all available illumination energy from the second light 805 in a normalized fashion. As the second laser 804 is capable of global dimming, only the necessary luminance is emitted by the second laser 804. Operation of the projection system 800 may be substantially similar to operation of the projection system 600 in that only the secondlaser 804 may be controlled to emit light for images below an APL threshold and both the first laser 802 and the second laser 804 may be controlled to emit light for images above or equal to the APL threshold.

[0055] The projection system 800 provides several advantages, as the removal of the light dump 612 and the optical filter 610 reduces the number of mechanical components. Additionally, employing global dimming in both the first optical path and the second optical path provides further opportunities for optimization, such as using the same light source with different dimming groups. However, the projection system 800 is more sensitive to thermal changes when compared to the projection system 600. Accordingly, each dual-path projection system may be suitable for different scenarios, having their own advantages and shortcomings.

[0056] Illustrations provided herein are simplified compared to realistic optical systems, and additional optics may be provided between components that are not illustrated. Additionally, embodiments described herein primarily refer to the combination of two optical paths at a DLP (for example, the DLP 608 and the DLP 808). However, in some implementations, the light projected by the first laser 602, 802 and the second laser 604, 804 may be combined prior to the DLP 608, 808 or combined at the PLM 606, 806, such as at a PLM prism structure as understood by one skilled in the art.Exemplary Modulation Devices

[0057] In some implementations, DLP devices described herein are digital micromirror devices (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. 9A-9B show an exemplary DMD 900 in accordance with various aspects of the present disclosure. In particular, FIG. 9A illustrates a plan view of the DMD 900, and FIG. 9B illustrates partial cross-sectional view of the DMD 900 taken along line LB illustrated in FIG. 9A. The DMD 900 includes a plurality of square micromirrors 902 arranged in a two-dimensional rectangular array on a substrate 904. Each micromirror 902 may correspond to one pixel of the eventual projection image, and may be configured to tilt about a rotation axis 908, shown for one particular subset of the micromirrors 902, by electrostatic or other type of actuation. The individual micromirrors 902 have a width 912 and are arranged with gaps of width 910 therebetween. The micromirrors 902 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 902 may be absorptive, such that input light which enters a gap is absorbed by the substrate 904.

[0058] While FIG. 9A expressly shows only some representative micromirrors 902, in practice the DMD 900 may include many more individual micromirrors in a number equal to a resolution of the projection system. 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 902 may be rectangular and arranged in the rectangular array; hexagonal and arranged in a hexagonal array, and the like. Moreover, while FIG. 9A illustrates the rotation axis 908 extending in an oblique direction, in some implementations the rotation axis 908 may extend vertically or horizontally.

[0059] As can be seen in FIG. 9B, each micromirror 902 may be connected to the substrate 904 by a yoke 914, which is rotatably connected to the micromirror 902. The substrate 904 includes a plurality of electrodes 916. While only two electrodes 916 per micromirror 902 are visible in the cross-sectional view of FIG. 9B, each micromirror 902 may in practice include additional electrodes. While not particularly illustrated in FIG. 9B, the DMD 900 may further include spacer layers, support layers, hinge components to control the height or orientation of the micromirror 902, and the like. The substrate 904 may include electronic circuitry associated with the DMD 900, such as complementary metal-oxide semiconductor (CMOS) transistors, memory elements, and the like.

[0060] Depending on the particular operation and control of the electrodes 916, the individual micromirrors 902 may be switched between an “on” position, an “off’ position, and an unactuated or neutral position. If a micromirror 902 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 906 into on-state light 918. If a micromirror 902 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 906 into off-state light 920. The off-state light 920 may be directed toward a light dump that absorbs the off-state light 920. In some instances, a micromirror 902 may be unactuated and lie parallel to the substrate 904. The particular angles illustrated in FIGS. 9A-9B 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.

[0061] Embodiments described herein also include PLMs 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 micro-electromechanical system (MEMS) architecture.

[0062] FIG. 10 illustrates one example PLM, implemented as a reflective LCOS PLM 1000 and shown in a partial cross-sectional view. As illustrated in FIG. 10, the PLM 1000 includes a silicon backplane 1010, a first electrode layer 1020, a second electrode layer 1030, a liquid crystal layer 1040, a cover glass 1050, and spacers 1060. The silicon backplane 1010 includes electronic circuitry associated with the PLM 1000, such as CMOS transistors and the like. The first electrode layer 1020 includes an array of reflective elements 1021 disposed in a transparent matrix 1022. The reflective elements 1021 may be formed of any highly optically reflective material, such as aluminum or silver. The transparent matrix 1022 may be formed of any highly optically transmissive material, such as a transparent oxide. The second electrode layer 1030 may be formed of any optically transparent electrically conductive material, such as a thin film of indium tin oxide (ITO). The second electrode layer 1030 may be provided as a common electrode corresponding to a plurality of the reflective elements 1021 of the first electrode layer 1020. In such a configuration, each of the plurality of the reflective elements 1021 will couple to the second electrode layer 1030 via a respective electric field, thus dividing the PLM 1000 into an array of pixel elements. Thus, individual ones (or subsets) of the plurality of the reflective elements 1021 may be addressed via the electronic circuitry disposed in the silicon backplane 1010, thereby to modify the state of the corresponding reflective element 1021.

[0063] The liquid crystal layer 1040 is disposed between the first electrode layer 1020 and the second electrode layer 1030, and includes a plurality of liquid crystals 1041. The liquid crystals 1041 are particles which exist in a phase intermediate a solid and a liquid; in other words, the liquid crystals 1041 exhibit a degree of directional order, but not positional order. The direction in which the liquid crystals 1041 tend to point is referred to as the “director.” The liquid crystal layer 1040 modifies incident light entering from the cover glass 1050 based on the birefringence An of the liquid crystals 1041, which may be expressed as the difference between the refractive index in adirection 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 1040. This thickness is set by the spacer 1060, which seals the PLM 1000 and ensures a set distance between the cover glass 1050 and the silicon backplane 1010. The liquid crystals 1041 generally orient themselves along electric field lines between the first electrode layer 1020 and the second electrode layer 1030. As illustrated in FIG. 10, the liquid crystals near the center of the PLM 1000 are oriented in this manner, whereas the liquid crystals 1041 near the periphery of the PLM 1000 are substantially non-oriented in the absence of electric field lines. By addressing individual ones of the plurality of reflective elements 1021 via a phasedrive signal, the orientation of the liquid crystals 1041 may be determined on a pixel-by-pixel basis.

[0064] FIG. 11 illustrates another example PLM, implemented as a DMD PLM 1100 and shown in a partial cross-sectional view. As illustrated in FIG. 11, the PLM 1100 includes a backplane 1110 and a plurality of controllable reflective elements as pixel elements, each of which includes a yoke 1121, a mirror plate 1122, and a pair of electrodes 1130. While only two electrodes 1130 are visible in the cross-sectional view of FIG. 11 , each reflective element may in practice include additional electrodes. While not particularly illustrated in FIG. 11, the PLM 1100 may further include spacer layers, support layers, hinge components to control the height or orientation of the mirror plate 1122, and the like. The backplane 1110 includes electronic circuitry associated with the PLM 1100, such as CMOS transistors, a memory array, and the like.

[0065] The yoke 1121 may be formed of or include an electrically conductive material so as to permit a biasing voltage to be applied to the mirror plate 1122. The mirror plate 1122 may be formed of any highly reflective material, such as aluminum or silver. The electrodes 1130 are configured to receive a first voltage and a second voltage, respectively, and may be individually addressable. Depending on the values of a voltage on the electrodes 1130 and a voltage (for example, the biasing voltage) on the mirror plate 1122, a potential difference exists between the mirror plate 1122 and the electrodes 1130, which creates an electrostatic force that operates on the mirror plate 1122. The yoke 1121 is configured to allow vertical movement of the mirror plate 1122 in response to the electrostatic force. The equilibrium position of the mirror plate 1122, which occurs when the electrostatic force and a spring-like force of the yoke 1121 are equal, determines the optical path length of light reflected from the upper surface of the mirror plate 1122. Thus, individual ones of the plurality of controllable reflective elements are controlled to provide a number(as illustrated, three) of discrete heights and thus a number of discrete phase configurations or phase states. As illustrated, each of the phase states has a flat profile. In some aspects of the present disclosure, the electrodes 1130 may be provided with different voltages from one another so as to impart a tilt to the mirror plate 1122. Such tilt may be utilized with a light dump of the type described above.

[0066] The PLM 1100 may be capable of high switching speeds, such that the PLM 1100 switches from one phase state on the order of tens of ps, for example. In order to provide for a full cycle of phase control, the total optical path difference between a state where the mirror plate 1122 is at its highest point and a state whether the mirror plate 1122 is at its lowest point should be approximately equal to the wavelength X of incident light. Thus, the height range between the highest point and the lowest point should be approximately equal to X / 2.

[0067] In some implementations, the PLM 1100 creates fixed diffraction orders, where the mirror plates 1122 produce multiple “copies” of the light impinging onto them. The PLM 1100 steers the light within the extent of each diffraction order, producing multiple image “copies” at the reconstruction plane. An image steered by the PLM 1100 may be formed on an image reconstruction plane at a distance at which the diffraction orders separate without overlapping. In some implementations, the image reconstruction plane is closer to the PLM 1100 to alleviate blurring of the reconstructed image. A Fourier filter is implemented with the PLM 1100 to remove overlap of diffraction orders at the image reconstruction plane. In some implementations, the diffraction patterns constructively interfere with each other to form the reconstructed image. Accordingly, if a portion of the light steered by the PLM 1100 is blocked, the reconstructed image blurs compared to a reconstructed image including all light from the PLM 1100.Light Source Controls

[0068] FIG. 12 illustrates a block diagram of a controller 1200 for use with various aspects of the disclosure. The controller 1200 includes, among other things, an electronic processor 1202, a memory 1204, and an input / output (I / O) interface 1206. The electronic processor 1202, the memory 1204, and the VO interface 1206 communicate over one or more control and / or data buses. FIG. 12 illustrates only one example controller 1200. The controller 1200 may include more or fewer components and may perform functions other than those explicitly described herein.

[0069] In some examples, the electronic processor 1202 is implemented as a microcontroller with a separate memory, such as the memory 1204. In other examples, the electronic processor 1202 may be implemented as a microcontroller with memory 1204 on the same chip. In other examples, the electronic processor 1202 may be implemented partially or entirely as, for example, a field- programmable gate array (FPGA), an applications specific integrated circuit (ASIC), and the like and the memory 1204 may not be needed or may be modified accordingly. In the example illustrated, the memory 1204 includes non-transitory, computer-readable memory (or medium) that stores instructions that are received and executed by the electronic processor 1202 to carry out the functionality of the projection system 600 and / or the projection system 800 described herein. The memory 1204 may include, for example, a program storage area and a data storage area. The program storage area and the data storage area may include combinations of different types of memory, such as non-volatile read-only memory, non-volatile flash memory and volatile randomaccess memory.

[0070] The controller 1200 may be connected to other components of the projection system 600, 800 via the I / O interface 1206, such as the first laser 602, 802, the second laser 604, 804, the PLM 606, 806, and / or the DLP 608, 808. The controller 1200 may control the first laser 602, 802, the second laser 604, 804, the PLM 606, 806, and / or the DLP 608, 808 to perform the operations described herein.

[0071] FIG. 13 illustrates a block diagram of one example method 1300 for controlling a projection system. The method 1300 may be performed by the controller 1200. While described with respect to the projection system 600, the controller 1200 may also perform the method 1300 to control the respective components of the projection system 800.

[0072] At block 1302, the controller 1200 determines the APL value of an image to be projected. For example, the controller 1200 receives image data indicating an image to be projected onto a screen. In some instances, the image data is stored in the memory 1204. In other instances, the controller 1200 receives the image data from an external device.

[0073] At block 1304, the controller 1200 determines whether the APL value is greater than or equal to an APL threshold. For example, the controller 1200 compares the APL value to an APL threshold. When the APL value is less than the APL threshold (“NO” at block 1304), the controller1200 proceeds to block 1306. When the APL value is greater than or equal to the APL threshold (“YES” at block 1308), the controller 1200 proceeds to block 1308.

[0074] At block 1306, the controller 1200 controls only the second laser 604 to emit light. For example, when the APL value of the image is below the APL threshold, the controller 1200 controls the second laser 604 to emit the second light 605 while maintaining the first laser 602 to an off state. Accordingly, the output image is formed with only the second light 605 being modulated by the PLM 606 and the DLP 608.

[0075] At block 1308, the controller 1200 controls both the first laser 602 and the second laser 604 to emit light. For example, when the APL value of the image is greater than or equal to the APL threshold, the controller 1200 controls the first laser 602 to emit the first light 603 and controls the second laser 604 to emit the second light 605. Accordingly, the output image is formed with both the first light 603 being modulated by the DLP 608, and the second light 605 being modulated by the PLM 606 and the DLP 608.

[0076] In some instances, when the APL of the image is relatively high (for example, greater than 97% APL), the image can be formed completely using the first laser 602. Accordingly, in some instances, when the APL of the image is greater than or equal to a second APL threshold, the second laser 604 is controlled to an off state. Accordingly, three states of operation may be present: (i) a first state when the APL is less than a first APL threshold where only the second laser 604 is controlled to emit light, (ii) a second state when the APL is greater than or equal to the first APL threshold and less than a second APL threshold where both the first laser 602 and the second laser 604 are controlled to emit light, and (iii) a third state when the APL is greater than or equal to a second APL threshold where only the first laser 602 is controlled to emit light.

[0077] Systems, methods, and devices in accordance with the present disclosure may take any one or more of the following configurations.

[0078] (1) A dual-modulation laser projection system, comprising: a first light source configured to emit a first light; a second light source configured to emit a second light; a phase light modulator (PLM) configured to receive the second light from the second light source and steer the second light as a modulated light; and a digital light processor (DLP) configured to receive the first light from the first light source and configured to receive the modulated light from the PLM, wherein the DLP is configured to modulate received light to generate an image, wherein, when the image has an averagepicture level (APL) value below an APL threshold, the first light source is controlled to an off state and the second light source is controlled to emit the second light, and wherein, when the image has an APL value above or equal to the APL threshold, the first light source is controlled to emit the first light and the second light source is controlled to emit the second light.

[0079] (2) The projection system according to (1), wherein the first light source is further configured to modulate a luminance of the first light based on the APL value of the image.

[0080] (3) The projection system according to (2), wherein the first light source is further configured to output the first light at a minimum luminance value above zero when the APL value of the image is equal to the APL threshold, wherein the first light source is configured to output the first light at a maximum luminance value when the APL value of the image is 100%, and wherein the first light source is configured to increase the luminance value of the first light for APL values increasing between the APL threshold and 100% APL.

[0081] (4) The projection system according to (3), wherein the first light source is configured to linearly increase the luminance value of the first light for APL values increasing between the APL threshold and 100% APL.

[0082] (5) The projection system according to any one of (2) to (4), wherein the second light source is further configured to modulate a luminance of the second light based on the APL value of the image.

[0083] (6) The projection system according to (5), wherein the first light source and the second light source have a combined maximum luminance of approximately 108 nits.

[0084] (7) The projection system according to any one of (1) to (6), wherein the APL threshold is a first APL threshold, and wherein when the image has an APL above or equal to a second APL threshold greater than the first APL threshold, the first light source is controlled to emit the first light and the second light source is controlled to an off state.

[0085] (8) The projection system according to any one of (1) to (7), further comprising an optical filter situated between the DLP and the PLM, wherein the optical filter is configured to receive the modulated light from the PLM and at least partially block unmodulated light included in the modulated light.

[0086] (9) The projection system according to any one of (1) to (8), wherein the APL threshold is approximately 90% APL.

[0087] (10) The projection system according to any one of (1) to (9), wherein the DLP is a digital micromirror device.

[0088] (11) The projection system according to any one of (1) to (10), wherein the first light and the modulated light are combined on a surface of the DLP.

[0089] (12) The projection system according to any one of (1) to (11), wherein the DLP has a modulation-stage contrast greater than or equal to approximately 30,000: 1.

[0090] (13) The projection system according to any one of (1) to (12), wherein the first light has a greater etendue value than the second light.

[0091] (14) A method for controlling a dual-modulation laser projection system, wherein the projection system includes a first optical path comprising a first light source and a digital light processor (DLP), and wherein the projection system includes a second optical path comprising a second light source, a phase light modulator (PLM), and the DLP, the method comprising: determining, based on image data, an average picture level (APL) value of an image to be projected; controlling, in response to the APL value of the image being below an APL threshold, the second light source to project a second light along the second optical path while maintaining the first light source in an off state; and controlling, in response to the APL value of the image being greater than or equal to the APL threshold, the first light source to project a first light along the first optical path and the second light source to project the second light along the second optical path.

[0092] (15) The method according to (14), further comprising modulating, in response to the APL value of the image being greater than or equal to the APL threshold, a luminance of the first light projected by the first light source based on the APL value of the image.

[0093] (16) The method according to (15), wherein, when the APL value of the image is equal to the APL threshold, the luminance of the first light is at a minimum luminance value above zero, and wherein, when the APL value of the image is 100%, the luminance of the first light is at a maximum luminance value.

[0094] (17) The method according to any one of (15) to (16), further comprising modulating a luminance of the second light based on the APL value of the image.

[0095] (18) The method according to any one of (15) to (17), wherein the APL threshold is a first APL threshold, and wherein the method further comprises controlling, in response to the APL value of the image being greater than or equal to a second APL threshold greater than the first APL threshold, the first light source to project the first light along the first optical path while maintaining the second light source in an off state.

[0096] (19) The method according to any one of (14) to (18), further comprising filtering, with an optical filter situated between the PLM and the DLP, light traveling along the second optical path, wherein the optical filter at least partially blocks unmodulated light included in the light traveling along the second optical path.

[0097] (20) A non-transitory computer-readable storage medium storing a program comprising instructions that, when executed by a processor, cause the processor to carry out the method according to any one of (14) to (19).

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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 are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.

Claims

CLAIMSWhat is claimed is:

1. A dual-modulation laser projection system, comprising: a first light source configured to emit a first light; a second light source configured to emit a second light; a phase light modulator (PLM) configured to receive the second light from the second light source and steer the second light as a modulated light; and a digital light processor (DLP) configured to receive the first light from the first light source and configured to receive the modulated light from the PLM, wherein the DLP is configured to modulate received light to generate an image, wherein, when the image has an average picture level (APL) value below an APL threshold, the first light source is controlled to an off state and the second light source is controlled to emit the second light, and wherein, when the image has an APL value above or equal to the APL threshold, the first light source is controlled to emit the first light and the second light source is controlled to emit the second light.

2. The projection system of claim 1, wherein the first light source is further configured to modulate a luminance of the first light based on the APL value of the image.

3. The projection system of claim 2, wherein the first light source is further configured to output the first light at a minimum luminance value above zero when the APL value of the image is equal to the APL threshold, wherein the first light source is configured to output the first light at a maximum luminance value when the APL value of the image is 100%, and wherein the first light source is configured to increase the luminance value of the first light for APL values increasing between the APL threshold and 100% APL.

4. The projection system of claim 3, wherein the first light source is configured to linearly increase the luminance value of the first light for APL values increasing between the APL threshold and 100% APL.

5. The projection system of any one of claims 2 to 4, wherein the second light source is furtherconfigured to modulate a luminance of the second light based on the APL value of the image.

6. The projection system of claim 5, wherein the first light source and the second light source have a combined maximum luminance of approximately 108 nits.

7. The projection system of any one of claims 1 to 6, wherein the APL threshold is a first APL threshold, and wherein when the image has an APL above or equal to a second APL threshold greater than the first APL threshold, the first light source is controlled to emit the first light and the second light source is controlled to an off state.

8. The projection system of any preceding claim, further comprising an optical filter situated between the DLP and the PLM, wherein the optical filter is configured to receive the modulated light from the PLM and at least partially block unmodulated light included in the modulated light.

9. The projection system of any preceding claim, wherein the APL threshold is approximately 90% APL.

10. The projection system of any preceding claim, wherein the DLP is a digital micromirror device.

11. The projection system of any preceding claim, wherein the first light and the modulated light are combined on a surface of the DLP.

12. The projection system of any preceding claim, wherein the DLP has a modulation-stage contrast greater than or equal to approximately 30,000: 1.

13. The projection system of any preceding claim, wherein the first light has a greater etendue value than the second light.

14. A method for controlling a dual-modulation laser projection system, wherein the projection system includes a first optical path comprising a first light source and a digital light processor (DLP), and wherein the projection system includes a second optical path comprising a second lightsource, a phase light modulator (PLM), and the DLP, the method comprising: determining, based on image data, an average picture level (APL) value of an image to be projected; controlling, in response to the APL value of the image being below an APL threshold, the second light source to project a second light along the second optical path while maintaining the first light source in an off state; and controlling, in response to the APL value of the image being greater than or equal to the APL threshold, the first light source to project a first light along the first optical path and the second light source to project the second light along the second optical path.

15. The method of claim 14, further comprising modulating, in response to the APL value of the image being greater than or equal to the APL threshold, a luminance of the first light projected by the first light source based on the APL value of the image.

16. The method of claim 15, wherein, when the APL value of the image is equal to the APL threshold, the luminance of the first light is at a minimum luminance value above zero, and wherein, when the APL value of the image is 100%, the luminance of the first light is at a maximum luminance value.

17. The method of claim 15 or 16, further comprising modulating a luminance of the second light based on the APL value of the image.

18. The method of any one of claims 15 to 17, wherein the APL threshold is a first APL threshold, and wherein the method further comprising controlling, in response to the APL value of the image being greater than or equal to a second APL threshold greater than the first APL threshold, the first light source to project the first light along the first optical path while maintaining the second light source in an off state.

19. The method of any one of claims 14 to 18, further comprising filtering, with an optical filter situated between the PLM and the DLP, light traveling along the second optical path, wherein the optical filter at least partially blocks unmodulated light included in the light traveling along the second optical path.

20. A non- transitory computer-readable storage medium storing a program comprising instructions that, when executed by a processor, cause the processor to carry out the method of any one of claims 14 to 19.

Images