WO2024196742A1 - Niveaux d'affichage pour systèmes à double modulation - Google Patents

Niveaux d'affichage pour systèmes à double modulation Download PDF

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Publication number
WO2024196742A1
WO2024196742A1 PCT/US2024/020099 US2024020099W WO2024196742A1 WO 2024196742 A1 WO2024196742 A1 WO 2024196742A1 US 2024020099 W US2024020099 W US 2024020099W WO 2024196742 A1 WO2024196742 A1 WO 2024196742A1
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WIPO (PCT)
Prior art keywords
modulator
sub
frame
level
during
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PCT/US2024/020099
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English (en)
Inventor
Jerome D. Shields
Trevor Davies
Douglas J. Gorny
Barret Lippey
Christopher John ORLICK
Martin J. Richards
Jon Scott Miller
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Dolby Laboratories Licensing Corporation
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Publication of WO2024196742A1 publication Critical patent/WO2024196742A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3102—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] using two-dimensional electronic spatial light modulators
    • H04N9/312—Driving therefor
    • H04N9/3126—Driving therefor for spatial light modulators in series

Definitions

  • This application relates generally to bit sequences for dual modulation display systems and, particularly, to creating display levels using different bit sequences on dual modulation digital micromirror devices.
  • 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, digital micromirror devices (DMDs) spatial light modulators (SLMs), phase light modulators (PLMs), and the like.
  • DMDs digital micromirror devices
  • SLMs spatial light modulators
  • PLMs phase light modulators
  • a bit sequencing pattern is used to control periods of time that the DMD micromirrors are on, and periods of time that the DMD micromirrors are off. Modulators may switch multiple times within a single frame.
  • Various aspects of the present disclosure relate to devices, systems, and methods for projection display.
  • One example embodiment provides a multi-modulation display system comprising a light source, a first modulator, a second modulator, and a controller.
  • the first modulator is illuminated by the light source and includes a first plurality of mirrors to modulate light from the light source.
  • the second modulator is illuminated by light from the first modulator and includes a second plurality of mirrors to modulate light from the first modulator.
  • the controller includes an electronic processor and a memory.
  • the memory comprises processor-readable instructions such that, when the electronic processor reads the processor- readable instructions, the electronic processor performs instructions including sending control signals to the first modulator such that the first plurality of mirrors are controlled to modulate light during a first sub-frame period of time, and sending control signals to the second modulator such that the second plurality of mirrors are controlled to modulate light during the first sub- frame period of time and during a second sub-frame period of time different from the first subframe period of time.
  • Another example embodiment provides a processor-implemented method for controlling a multi-modulation display system comprising a light source, a first modulator including a first plurality of mirrors, a second modulator including a second plurality of mirrors, and a processor controlling the first modulator and the second modulator.
  • the method includes sending control signals to the first modulator such that the first plurality of mirrors are controlled to modulate light from the light source during a first sub-frame period of time, and sending control signals to the second modulator such that the second plurality of mirrors are controlled to modulate light from the first modulator during the first sub-frame period of time and during a second sub-frame period of time different from the first sub-frame period of time.
  • Another example embodiment provides a multi-modulation display system comprising a light source, a first modulator, a second modulator, and a controller.
  • the first modulator is illuminated by the light source and includes a first plurality of mirrors to modulate light from the light source.
  • the second modulator is illuminated by light from the first modulator and includes a second plurality of mirrors to modulate light from the first modulator.
  • the controller includes an electronic processor and a memory.
  • the memory comprises processor-readable instructions such that, when the electronic processor reads the processor- readable instructions, the electronic processor performs instructions including sending, during a first frame, control signals to the first modulator and the second modulator such that a plurality of first sub-frame periods sum to generate a first portion of a display level, and sending, during the first frame, control signals to the first modulator and the second modulator such that a plurality of second sub-frame periods sum to generate a second portion of the display level.
  • the first portions of the display level When averaged over a first plurality of frames, the first portions of the display level generate an average first portions level.
  • the second portions of the display level When averaged over a second plurality of frames, the second portions of the display level generate an average second portions level.
  • the average first portions level and the average second portions level generate the display level.
  • Another example embodiment provides a method for generating display levels in a dual-modulation system comprising sending, during a first frame, control signals to the first modulator and the second modulator such that a plurality of first sub-frame periods sum to generate a first portion of a display level, wherein the first modulator is illuminated by a light source, and wherein the second modulator is illuminated by light from the first modulator, and sending, during the first frame, control signals to the first modulator and the second modulator such that a plurality of second sub-frame periods sum to generate a second portion of the display level.
  • the first portions of the display level When averaged over a first plurality of frames, the first portions of the display level generate an average first portions level.
  • the second portions of the display level When averaged over a second plurality of frames, the second portions of the display level generate an average second portions level.
  • the average first portions level and the average second portions level generate the display level.
  • Another example embodiment provides a non-transitory computer-readable medium storing instructions that, when executed by a processor of a projection system, cause the projection system to perform operations comprising sending, during a first frame, control signals to the first modulator and the second modulator such that a plurality of first sub-frame periods sum to generate a first portion of a display level, wherein the first modulator is illuminated by a light source, and wherein the second modulator is illuminated by light from the first modulator, and sending, during the first frame, control signals to the first modulator and the second modulator such that a plurality of second sub-frame periods sum to generate a second portion of the display level.
  • the first portions of the display level When averaged over a first plurality of frames, the first portions of the display level generate an average first portions level. When averaged over a second plurality of frames, the second portions of the display level generate an average second portions level. When summed, the average first portions level and the average second portions level generate the display level.
  • 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.
  • FIG. 1 illustrates a block diagram of an exemplary image projector display system according to various aspects of the present disclosure.
  • FIG. 2A illustrates a plan view of an exemplary spatial light modulator for use with various aspects of the present disclosure.
  • FIG. 2B illustrates a cross-sectional view taken along the line I-B of FIG. 2 A.
  • FIG. 3 illustrates a high-level diagram of a switching scheme that matches a bitsequence repeating pattern.
  • FIG. 4A illustrates an example bit sequence for a pre-modulator.
  • FIG. 4B illustrates an example bit sequence for a primary modulator.
  • FIG. 4C illustrates the transmittance resulting from the bit sequences of FIGS. 4A and 4B.
  • FIG. 5 A illustrates another example bit sequence for a pre-modulator.
  • FIG. 5B illustrates another example bit sequence for a primary modulator.
  • FIG. 5C illustrates the transmittance resulting from the bit sequences of FIGS. 5 A and 5B.
  • FIG. 6A illustrates another example bit sequence for a pre-modulator.
  • FIG. 6B illustrates another example bit sequence for a primary modulator.
  • FIG. 6C illustrates the transmittance resulting from the bit sequences of FIGS. 6A and 6B.
  • FIG. 7 illustrates bit sequence levels for various PQ code values.
  • FIG. 8 illustrates an example of achieved display levels with two layers of precision.
  • FIG. 9 illustrates an example of achieved display levels with four layers of precision.
  • FIG. 10 illustrates a block diagram of a method for generating display levels.
  • 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.
  • ASICs application specific integrated circuits
  • FPGAs field programmable gate arrays
  • FIG. 1 illustrates one possible embodiment of a suitable image projector display system.
  • the projector display system is constructed as a dual/multi-modulator projection system 100.
  • the projection system 100 employs a light source 102 that supplies the projector system with a desired illumination such that a final projected image will be sufficiently bright for the intended viewers of the projected image.
  • Light source 102 may comprise any suitable light source, such as, but not limited to, Xenon lamps, laser(s), coherent light sources, and partially-coherent light sources. Additionally, optical systems described herein may implement optical fibers to transfer light from the light source 102 to optics within the optical system.
  • Light 104 from the light source 102 may illuminate a first modulator 106 (for example, a pre-modulator) that may, in turn, illuminate a second modulator 110 (for example, a primary modulator) via a set of optional optical components 108.
  • a first modulator 106 for example, a pre-modulator
  • a second modulator 110 for example, a primary modulator
  • Light from the second modulator 110 may be projected by a projection lens 112 (or other suitable optical components) to form a final projected image upon a screen 114.
  • the projection lens 112 includes an optical filter for filtering the light from the second modulator 110, as described below in more detail.
  • the first modulator 106 and the second modulator 110 may be controlled by a controller 116.
  • the controller 116 may receive input image and/or video data and may perform certain image processing algorithms, gamut mapping algorithms or other such suitable processing upon the input image/video data and output control/data signals to the first modulator 106 and the second modulator 110 in order to achieve a desired final projected image on the screen 114.
  • Light recycling module 103 is depicted in FIG. 1 as a dotted box that may be placed in the light path from the light source 102 to the first modulator 106. It may be appreciated that light recycling may be inserted into the projector system at various points in the projector system. For example, light recycling may be placed between the first and second modulators. In addition, light recycling may be placed at more than one point in the optical path of the display system.
  • FIG. 1 depicts a single light channel
  • the first and second modulators may be replicated for each of a series of color channels within the projector such that each color channel includes two optically offset reflective modulators.
  • the series of color channels may comprise a red channel, a green channel, and a blue channel.
  • the light source may comprise, for example, a plurality of colored laser light sources.
  • the light sources may be modulated either globally (in brightness) and/or spatially (locally) dimmed according to signals (not shown) from a controller (e.g., 116).
  • the intermediate signals to the second modulator may be, for example, based on a light field simulation comprising a point spread function of light reflected by the first modulator and the offset.
  • the intermediate signals to the second modulator may be based on a point spread function of light reflected by the first modulator in each channel and the offset in each channel.
  • the offset in the channels may be the same, or the offset of at least two channels is different and the intermediate signals to the second modulator in each channel is based on at least one of the offset and differences in offset between channels.
  • FIG. 1 While the embodiment of FIG. 1 is presented in the context of a dual, multimodulation projection system, it should be appreciated that the techniques and methods of the present application will find application in other dual, multi-modulation display systems.
  • a dual modulation display system comprising a backlight, a first modulator (e.g., LCD or the like), and a second modulator (e.g., LCD or the like) may employ suitable optical components and image processing methods and techniques to affect the performance and efficiencies discussed herein in the context of the projection systems.
  • the first modulator 106 and the second modulator 110 may be configured as digital micromirror devices (DMDs) composed of a plurality of mirrors used to adjust the angle of incidence of light.
  • DMDs digital micromirror devices
  • FIGS. 2A-2B show an exemplary DMD 200 in accordance with various aspects of the present disclosure.
  • FIG. 2A illustrates a plan view of the DMD 200
  • FIG. 2B illustrates partial cross-sectional view of the DMD 200 taken along line LB illustrated in FIG. 2A.
  • the DMD 200 includes a plurality of square micromirrors 202 arranged in a two-dimensional rectangular array on a substrate 204.
  • Each micromirror 202 may correspond to one pixel of the eventual projection image, and may be configured to tilt about a rotation axis 208, shown for one particular subset of the micromirrors 202, by electrostatic or other type of actuation.
  • the individual micromirrors 202 have a width 212 and are arranged with gaps of width 210 therebetween.
  • the micromirrors 202 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 202 may be absorptive, such that input light which enters a gap is absorbed by the substrate 204.
  • FIG. 2A expressly shows only some representative micromirrors 202
  • the DMD 200 may include many more individual micromirrors in a number equal to a resolution of the projection system 100.
  • the resolution may be 2K (2048x 1080), 4K (4096x2160), 1080p (1920x 1080), consumer 4K (3840x2160), and the like.
  • the micromirrors 202 may be rectangular and arranged in the rectangular array; hexagonal and arranged in a hexagonal array, and the like.
  • FIG. 2A illustrates the rotation axis 208 extending in an oblique direction, in some implementations the rotation axis 208 may extend vertically or horizontally.
  • each micromirror 202 may be connected to the substrate 204 by a yoke 214, which is rotatably connected to the micromirror 202.
  • the substrate 204 includes a plurality of electrodes 216. While only two electrodes 216 per micromirror 202 are visible in the cross-sectional view of FIG. 2B, each micromirror 202 may in practice include additional electrodes. While not particularly illustrated in FIG. 2B, the DMD 200 may further include spacer layers, support layers, hinge components to control the height or orientation of the micromirror 202, and the like.
  • the substrate 204 may include electronic circuitry associated with the DMD 200, such as complementary metal-oxide semiconductor (CMOS) transistors, memory elements, and the like.
  • CMOS complementary metal-oxide semiconductor
  • the individual micromirrors 202 may be switched between an “on” position, an “off’ position, and an unactuated or neutral position. If a micromirror 202 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 206 into on-state light 218. If a micromirror 202 is in the off position, it is actuated to an angle of (for example) +12° (that is, rotated clockwise by 12° relative to the neutral position) to specularly reflect the input light 406 into off-state light 220.
  • the off-state light 220 may be directed toward a light dump that absorbs the off-state light 220.
  • a micromirror 202 may be unactuated and lie parallel to the substrate 204.
  • the particular angles illustrated in FIGS. 2A-2B and described here are merely exemplary and not limiting.
  • 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.
  • the first modulator 106 and/or the second modulator 110 may be different suitable modulation devices, such as MEMS arrays or other devices including a plurality of analog mirrors or digital mirrors.
  • bit sequence refers to how the micromirrors 202 are turned on and off.
  • a frame period is partitioned into bit-times, or bitplanes, such that pixels may be on or off for each bit-time.
  • the bit sequence may be modified such that the higher order bits are spread across the frame period, and therefore, they may be repeated multiple times.
  • the top bits e.g., the top 12 bits of 16 bits
  • the top bits may be repeated for each subframe. This would allow a pattern with the top 12 bits to repeat - e.g., 16 times (in a 1/16 subframe subdivision embodiment). The lower significant bits would remain unaffected (e.g., spread across the entire frame period).
  • the beam steering device e.g., mirrors or other elements
  • the first modulator 106 switch quickly and/or at a desired rate (e.g., 10-100 microseconds). This may be desirable so that the first modulator 106 may switch in a “dark” time between sequence repeats. During such a dark time, the display system may not be outputting any light to be rendered and/or projected. This may help to avoid noticeable and/or undesired visual effects.
  • the fraction of time a pixel is on determines the level that is made. Bit-times are short enough that the bit on-times are not seen distinctly, and the level seen is the average on-time for the frame period.
  • the frame rate for bit-sequencing may be different than the video frame rate.
  • the bit-sequencing frame rate for a 24 fps video could be four times that rate, at 96 fps.
  • the number of levels that can be made by bit sequencing is limited by the portioning of the frame period into bit-times. The shortest duration bit-time determines the precision of the levels.
  • FIG. 3 depicts a high level switching scheme 300 that matches the bit-sequence repeating pattern.
  • Pattern 302 depicts the time periods (e.g., 302a and 302b) during which the bit sequence is repeating. Between these time periods is a period of dark time 303 between sequence repeats.
  • the first modulator is able to switch multiple times (e.g., 304a, 304b, . . ., 304n) during the entire period and the dark time.
  • Dual modulation DMDs such as the first modulator 106 and the second modulator 110, may use synchronized bit sequencing to make display levels.
  • the bit sequencing uses the same bit sequences for both the first modulator 106 and the second modulator 110 such that they are both on or off at the same time.
  • different bit sequences are used such that both the first modulator 106 and the second modulator 110 are on, both the first modulator 106 and the second modulator 110 are off, or only one of the first modulator 106 and the second modulator 110 are on at any time.
  • the fraction of a frame time that both the first modulator 106 and the second modulator 110 are on determines the display level that is created.
  • the contribution to the display level is non-zero, but is instead a very small display level that may be significant only when both the first modulator 106 and the second modulator 110 are off for the whole frame time. For example, let F be the display level and let both on time be the fraction of a frame time that both the first modulator 106 and the second modulator 110 are on.
  • Y on be the display level when both the first modulator 106 and the second modulator 110 are on.
  • Y off be. the display level when a single modulator is off such that, with dual modulation, both the first modulator 106 and the second modulator 110 are off and create a display level of Y off. It should be understood that to simplify these examples, Y off is chosen to be the same for both modulators, and that Eq. 1 and Eq. 2 would be appropriately modified if Y off were different for the two modulators. Accordingly, the created display level for a particular bit sequence is provided by Equation 1 :
  • the second term (1-both on time) *Y off , is likely insignificant compared to the first term, except for when establishing a black level when the first term is zero.
  • FIGS. 4A-4C illustrate an example bit sequence that partitions a frame into ten equal-sized sub-intervals. In other embodiments, the bit sequences may have significantly more sub-intervals or sub-intervals of different sizes.
  • FIG. 4A provides the bit sequence for the first modulator 106 over the frame.
  • FIG. 4B provides the bit sequence for the second modulator 110 over the frame.
  • FIG. 4C provides the dual-modulation transmittance level over the frame. As referred to herein, transmittance level may be interpreted as normalized display level.
  • transmittance level may be interpreted as normalized display level.
  • the same bit sequence is used for both the first modulator 106 and the second modulator 110.
  • the value of Y on is 1 (full transmittance), and the value of Y off is 1/3000 (minimal transmittance). These values are merely examples.
  • the Y off value may vary based on the contrast of the modulators (e.g. 1/contrast).
  • the first modulator 106 and the second modulator 110 have a contrast value of 3000: 1.
  • the bit sequence has the first modulator 106 and the second modulator 110 on at the sub-intervals 3 and 8. Accordingly, the both on time value is 2/10. Solving for Equation 1 it is found that the display level is:
  • the second term (1-both on time) *Y off is a value visually insignificant compared to the first term, and can be ignored.
  • the display levels increase in tenths (0/10, 1/10, 2/10. . . 10/10) and only provide as many levels as the number of partitioned sub-intervals plus one. These display levels may be referred to as “coarse levels”.
  • both on time may be a value from a limited set of discrete values including zero and some smallest value.
  • the smallest value and the precision of other small values may not be sufficient for making all levels needed for a display.
  • the other needed values may be made using other complimentary schemes such as dithering.
  • bit sequencing may be modified to create additional levels. Rather than limiting the set of bit sequences to those having both the first modulator 106 and the second modulator 110 on or off at the same time, bit sequences may be included that have a single modulator on while the other modulator is off. For example, let one on time be the fraction of a frame time that only one modulator is on. The display level Y for a particular bit sequence is then provided by Equation 2:
  • both on time is low
  • the second term one on time *Y off is not insignificant compared to both on time *Y on, and one on time may be manipulated to create many more bit sequences that make many more display levels.
  • This relationship between both on time*Y on and one on time*Y off may be considered a course level with a fine adjustment, where the fine adjustment is used to make more precise display levels than simply using the course level.
  • the fine adjustment may henceforth be referred to as “fine levels”.
  • FIGS. 5A-5C illustrate another example bit sequence that partitions a frame into ten equal-sized sub-intervals.
  • the bit sequences may have significantly more sub-intervals or sub-intervals of different sizes.
  • FIG. 5A provides the bit sequence for the first modulator 106 over the frame.
  • FIG. 5B provides the bit sequence for the second modulator 110 over the frame.
  • FIG. 5C provides the transmittance level over the frame.
  • a different bit sequence is used for the first modulator 106 than the second modulator 110.
  • the value of Y on is 1, and the value of Y off is 1/3000.
  • a first bit sequence has the first modulator 106 on from 2.5 to 3.5 and 7.5 to 8.5 (or on at the sub-intervals 3 and 8).
  • a second bit sequence has the second modulator 110 on at the subintervals 3, 5, 6, and 8. Accordingly, the both on time is 2/10 and the one on time is 2/10.
  • both the second term one on time*Y off and the third term (1- both on time-one one time) *Y off are visually insignificant compared to the first term both on time *Y on.
  • Fine adjustments have additional benefits when the desired display levels are less than the display level made by both on time set at its minimum non-zero discrete level. To make these lowest display levels with the fine adjustment, both on time is set to zero and one on time is manipulated to create smaller display levels. Fine adjustments may also make other needed levels such as those between both on time first and second non-zero levels, or between other greater but low coarse levels. As coarse levels increase, their precision approaches that needed for a display, and the utility of a fine adjustment diminishes.
  • FIGS. 6A-6C illustrate another example bit sequence that partitions a frame into ten equal-sized sub-intervals.
  • the bit sequences may have significantly more sub-intervals or sub-intervals of different sizes.
  • FIG. 6A provides the bit sequence for the first modulator 106 over the frame.
  • FIG. 6B provides the bit sequence for the second modulator 110 over the frame.
  • FIG. 6C provides the transmittance level over the frame.
  • a different bit sequence is used for the first modulator 106 than the second modulator 110.
  • the value of Y on is 1, and the value of Y off is 1/3000.
  • a first bit sequence maintains the first modulator 106 off, and accordingly both on time is set to zero.
  • a second bit sequence has the second modulator 110 on at the subintervals 5 and 6. Accordingly, one on time is 2/10. Solving for Equation 2, it is found that the display level is:
  • the second term one on time*Y off is visually significant, creating a useful dark level.
  • the second modulator 110 may be manipulated to create eleven useful dark discrete display levels.
  • the eleven dark levels are created by manipulating the second modulator 110 with the first modulator 106 being maintained off. These fine adjustment levels are visually significant, but are much less than the first non-zero coarse level when both the first modulator 106 and the second modulator 110 are on, even if the modulators are on for only one subinterval.
  • the eleven fine adjustment levels alone do not completely fill the gap between coarse level zero and the first non-zero level. To have the fine adjustment fill-in the gaps between coarse levels, the coarse levels may be spaced more closely together.
  • bit sequence for a display that is one bit sequencing method among many. Let the bit sequence be similar to that as previously shown in FIGS. 4A- 4C, 5A-5C, and 6A-6C, but the time frame is portioned into 2 12 sub-intervals such that the coarse levels that are made correspond to the values of a 12-bit number. Accordingly, the smallest coarse level has a value of l/(2 12 ). Another example may make the same 2 12 levels or other similarly precise levels by using a coarser bit sequencing method complimented by other methods such as dither, as described below in more detail.
  • FIG. 7 shows perceptual quantizer (PQ) signal inputs for the display levels Y (in nits) that should be displayed, and the coarse discrete levels that would be displayed by the 12- bit bit sequencing method if the Y value corresponding to the maximum 12-bit number were 108 nits.
  • PQ perceptual quantizer
  • light from the first modulator 106 is cast onto the second modulator 110, but not at pixel -to- pixel precision. Rather, light from a pixel of the first modulator 106 (e.g., a premodulator pixel) is cast onto an adjacent group of pixels of the second modulator 110 (e.g., primary pixels).
  • the frame time may be partitioned into two intervals, one for coarse levels created with both the first modulator 106 and the second modulator 110 on or off at the same time, and another for fine levels made with only either the first modulator 106 or the second modulator 110 on. These two intervals may be further divided into sub-intervals for two bit sequences, one for the coarse levels and another for the fine levels.
  • all premodulator pixels are off, preventing any premodulator pixel from casting light onto a primary pixel that relies on the premodulator pixel being off.
  • the fine levels frame interval is henceforth referred to as the premodulator off time.
  • Dedicating a fraction of the frame interval as a premodulator off time provides for making fine levels while preventing some spatial artifacts.
  • the peak brightness of the display is reduced by the fraction of the frame time that is the premodulator off time. Accordingly, the duration of the premodulator off time may be limited to achieve the necessary level precision while maintaining a sufficient peak brightness level.
  • Dithering is intentionally-applied noise used to randomize quantization error and may also be used to create more display levels. While embodiments described herein primarily refer to the use of DMDs, the use of dithering is not restricted to displays using DMDs as dithering operates on frames made by any display technology. Dithering utilizes discrete levels that are created by some other means, such as the previously-described bit sequencing for DMDs. Dithering alternately shows those discrete levels such that their average over time is an in-between level, providing additional precision to the discrete levels created by bit sequencing.
  • bit-sequencing may show different discrete levels within a frame period to make a level for the frame that is in-between the discrete levels
  • dithering may show frames with discrete levels such that many frames average to levels that are in-between the discrete levels.
  • a dither method may use any number of frames to average those levels. As one example, if 64 frames are used and each frame can be shown at a lesser discrete level and a greater discrete level, then one of 64 more precise levels may be made by showing some of the 64 frames at the lesser discrete level, and the remainder of the 64 frames at the greater discrete level. While 64 frames are used as an example, any number of frames may be used for the dithering method.
  • pixels in a local area of the frame that alternately show the same two discrete levels to make the same intermediate level may operate at different phases, mixing the showing of the discrete levels to minimize visibility.
  • bit sequencing for DMDs and dithering may be used together as complimentary methods of creating or generating display levels.
  • a bit sequence may result in 2 12 discrete display levels that are then used by a dithering method that averages those levels over 64 frames.
  • the dithering method adds 6 bits of precision to the 12 bits of the bit-sequencing, resulting in a total of 2 18 display levels.
  • the bit sequencing creates coarse levels.
  • the dithering creates more precise intermediate levels in between the coarse levels created by bit sequencing.
  • the frame time is partitioned into two parts: (i) a longer interval for making bright levels by operating the first modulator 106 and the second modulator 110 on and off at the same time, and (ii) a shorter premodulator off interval for making dimmer levels by operating the first modulator 106 off while the second modulator 110 is on or off.
  • the longer interval and the shorter interval may also separately be combined with dithering to increase precision, resulting in four layers of precision.
  • FIGS. 8-9 illustrate example display levels of a dual-modulation DMD display with levels created using the four layers of precision. Only lower levels of precision are provided that require the most precision. In FIG.
  • 14-bit coarse linear levels are created during the frame interval when the first modulator 106 and the second modulator 110 are operated both on or off at the same time. Finer precision is created with 25 levels of dither for each coarse level.
  • the 2 -bit premodulator off linear levels are made during the frame interval when the first modulator 106 is off and the second modulator 110 is on or off.
  • FIG. 9 illustrates the precision achieved with 64 levels of dither for each premodulator off linear level, creating all PQ levels.
  • the Y range and level precision for the display are achieved by four layers of increasing precision.
  • the layers of precision include 14 bits of coarse linear levels with 25 levels of dither, and 2 bits of premodulator off linear levels with 64 levels of dither. These values are merely an example, and may be selected based on the physical limitations of devices, light efficiency, artifacts, and other performance characteristics.
  • FIG. 10 One particular implementation of the bit-sequencing technique combined with the dithering technique in a dual -modulation projection system, such as the projection system 100, is illustrated in FIG. 10.
  • the method 1000 of FIG. 10 may be performed by the controller 116 of FIG. 1, and may be implemented using hardware, software, firmware, or combinations thereof.
  • the method 1000 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 100.
  • the method 1000 provides a particular order of operations, in some instances, the steps of the method 1000 may be performed in a different order.
  • the method 1000 includes sending, during a first frame, control signals to the first modulator 106 and the second modulator 110 such that a plurality of first subframe periods sum to generate a first portion of a display level.
  • the micromirrors 202 of the first modulator 106 and the second modulator 110 are controlled to modulate light during first sub-frame periods of time at a first display level.
  • the method 1000 includes sending, during the first frame, control signals to the first modulator 106 and the second modulator 110 such that a plurality of second sub-frame periods sum to generate a second portion of the display level.
  • the micromirrors 202 of the first modulator 106 and the second modulator 110 are controlled to modulate light during second sub-frame periods of time at a second display level.
  • the first modulator 106 is controlled to an off state. Accordingly, the second modulator 110 modulates light during a sub-frame time period in which the first modulator 106 may not modulate light.
  • the method 1000 includes repeating steps 1002 and 1004 for a plurality of image frames.
  • the first portion of the display level and the second portion of the display level combine to form the display level.
  • the first portions of the display level when averaged over a first plurality of frames, the first portions of the display level generate an average first portions level.
  • the second portions of the display level When averaged over a second plurality of frames, the second portions of the display level generate an average second portions level.
  • the average first portions level and the average second portions level generate the display level.
  • first modulator 106 and the second modulator 110 may be controlled on and off separately during different sub-frame periods, providing two levels of precision in creating display levels. Additionally, the display levels created by the first modulator 106 and the second modulator 110 may be averaged over a plurality of frames, providing two additional levels of precision in creating display levels.
  • Systems, methods, and devices in accordance with the present disclosure may take any one or more of the following configurations.
  • a multi-modulation display system comprising: a light source; a first modulator, the first modulator being illuminated by the light source, the first modulator including a first plurality of mirrors to modulate light from the light source; a second modulator, the second modulate being illuminated by light from the first modulator, the second modulator including a second plurality of mirrors to modulate light from the first modulator; and a controller including an electronic processor and a memory, the memory comprising processor- readable instructions such that, when the electronic processor reads the processor-readable instructions, the electronic processor performs instructions including: sending control signals to the first modulator such that the first plurality of mirrors are controlled to modulate light during a first sub-frame period of time, and sending control signals to the second modulator such that the second plurality of mirrors are controlled to modulate light during the first sub-frame period of time and during a second sub-frame period of time different from the first sub-frame period of time.
  • a processor-implemented method for controlling a multi-modulation display system comprising a light source, a first modulator including a first plurality of mirrors, a second modulator including a second plurality of mirrors, and a processor controlling the first modulator and the second modulator, the method comprising: sending control signals to the first modulator such that the first plurality of mirrors are controlled to modulate light from the light source during a first sub-frame period of time, and sending control signals to the second modulator such that the second plurality of mirrors are controlled to modulate light from the first modulator during the first sub-frame period of time and during a second sub-frame period of time different from the first sub-frame period of time.
  • a multi-modulation display system comprising: a light source; a first modulator, the first modulator being illuminated by the light source, the first modulator including a first plurality of mirrors to modulate light from the light source; a second modulator, the second modulate being illuminated by light from the first modulator, the second modulator including a second plurality of mirrors to modulate light from the first modulator; and a controller including an electronic processor and a memory, the memory comprising processor- readable instructions such that, when the electronic processor reads the processor-readable instructions, the electronic processor performs instructions including: sending, during a first frame, control signals to the first modulator and the second modulator such that a plurality of first sub-frame periods sum to generate a first portion of a display level, and sending, during the first frame, control signals to the first modulator and the second modulator such that a plurality of second sub-frame periods sum to generate a second portion of the display level, wherein, when averaged over a first plurality of
  • each of the first sub-frame periods includes a longer bit time interval than each of the second sub-frame periods.
  • a method for generating display levels in a dual-modulation system comprising: sending, during a first frame, control signals to the first modulator and the second modulator such that a plurality of first sub-frame periods sum to generate a first portion of a display level, wherein the first modulator is illuminated by a light source, and wherein the second modulator is illuminated by light from the first modulator; and sending, during the first frame, control signals to the first modulator and the second modulator such that a plurality of second sub-frame periods sum to generate a second portion of the display level, wherein, when averaged over a first plurality of frames, the first portions of the display level generate an average first portions level, wherein, when averaged over a second plurality of frames, the second portions of the display level generate an average second portions level, and wherein, when summed, the average first portions level and the average second portions level generate the display level.
  • each of the first sub-frame periods includes a longer bit time interval than each of the second sub-frame periods.
  • a non-transitory computer-readable medium storing instructions that, when executed by a processor of a projection system, cause the projection system to perform operations comprising the method according to any one of (16) to (20).

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Abstract

L'invention concerne des systèmes et des procédés permettant de créer des niveaux d'affichage à l'aide de différentes séquences de bits sur des dispositifs à micromiroirs numériques à double modulation. Un exemple concerne un système d'affichage à modulation multiple comprenant une source de lumière, un premier modulateur, un second modulateur et un dispositif de commande. Le premier modulateur comprend une première pluralité de miroirs destinés à moduler la lumière provenant de la source de lumière. Le second modulateur comprend une seconde pluralité de miroirs destinés à moduler la lumière provenant du premier modulateur. Le dispositif de commande comprend un processeur électronique et une mémoire. Le processeur électronique exécute des instructions comprenant l'envoi de signaux de commande au premier modulateur de telle sorte que la première pluralité de miroirs soient commandés pour moduler la lumière pendant une première période de sous-trame, et l'envoi de signaux de commande au second modulateur de telle sorte que la seconde pluralité de miroirs soient commandés pour moduler la lumière pendant la première période de sous-trame et pendant une seconde période de sous-trame.
PCT/US2024/020099 2023-03-20 2024-03-15 Niveaux d'affichage pour systèmes à double modulation WO2024196742A1 (fr)

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Application Number Priority Date Filing Date Title
US202363453423P 2023-03-20 2023-03-20
US63/453,423 2023-03-20
US202363596879P 2023-11-07 2023-11-07
US63/596,879 2023-11-07

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Publication number Priority date Publication date Assignee Title
US20050190140A1 (en) * 2004-03-01 2005-09-01 Seiko Epson Corporation Gradation control device, optical display device, gradation control program, optical display device control program, method of controlling gradation and method of controlling optical display device
US20170206822A1 (en) * 2016-01-14 2017-07-20 Carl Zeiss Ag Projector for projecting images
US20180308401A1 (en) * 2015-10-28 2018-10-25 Rockwell Collins, Inc. Image modulation apparatus
JP2021043287A (ja) * 2019-09-10 2021-03-18 日本放送協会 ２重変調方式プロジェクタの制御装置及びそのプログラム、並びに、２重変調方式プロジェクタ

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050190140A1 (en) * 2004-03-01 2005-09-01 Seiko Epson Corporation Gradation control device, optical display device, gradation control program, optical display device control program, method of controlling gradation and method of controlling optical display device
US20180308401A1 (en) * 2015-10-28 2018-10-25 Rockwell Collins, Inc. Image modulation apparatus
US20170206822A1 (en) * 2016-01-14 2017-07-20 Carl Zeiss Ag Projector for projecting images
JP2021043287A (ja) * 2019-09-10 2021-03-18 日本放送協会 ２重変調方式プロジェクタの制御装置及びそのプログラム、並びに、２重変調方式プロジェクタ

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