Display system, head-mounted display, and method

Abstract

The display system comprises an illumination system configured to emit at least partially coherent light, a spatial light modulator SLM illuminated by the illumination system and for applying a modulation pattern to the illumination light, the SLM configured to form a single modulation pattern H that simultaneously represents multiple image fields, where the information associated with each of the multiple image fields occupies a different portion of the Fourier transform F(H) of H, an optical system that receives the light modulated by the SLM and is arranged to create a Fourier plane of the SLM, and a spatial filter substantially positioned in the Fourier plane of the SLM, the spatial filter comprising multiple regions, each region corresponding to a portion of F(H) representing an image field, and each region configured to allow light associated with the image field corresponding to that region to pass through. In some examples, in a single modulation pattern, the information associated with the image field having the greatest perceptual significance to the viewer occupies the largest portion of F(H).

Description

[Technical Field]

[0001] The present invention relates to a display system, a spatial filter that can be used in the display system, and a method for operating the display system. More specifically, the present invention relates to a display system capable of displaying multiple image fields using a single modulation pattern of a modulator. [Background technology]

[0002] Display systems typically have a refresh rate, expressed in frames per second or Hz, which indicates the number of frames that can be displayed per unit of time. A higher refresh rate allows for smoother perceived motion, for example.

[0003] Higher refresh rates not only result in smoother motion, but can also enable other operating modes. For example, in holographic display systems, a higher refresh rate can enable techniques such as noise averaging and eyebox expansion.

[0004] The display system should ideally be able to display more image fields per unit of time. [Overview of the project]

[0005] This disclosure utilizes the observation that a single modulation pattern on a modulator can encode multiple image fields that target or occupy different parts of a spatial frequency domain, such as the Fourier domain. Throughout this specification, “Fourier domain” refers to the spatial frequency domain of the pattern displayed on the modulator. “Image field” may also be called image information or graphic information. An image field may be, but is not limited to, a 2D image, a 3D image, a hologram, individual views of a 3D scene, multiple or sequential views of a 3D scene, a color channel, an image with a noise profile, an image with additional constraint data, or one of any of the above components. As long as these image fields do not interfere coherently or have partial coherence, they can all be combined and perceived by the viewer with the human eye without significantly affecting the quality of the perceived image. Spatial filters targeting regions corresponding to image fields in the spatial frequency domain can prevent coherent interference. In this way, it is possible to display two or more image fields on a modulator simultaneously using a single modulation pattern, thereby increasing the number of image fields that can be displayed per unit time.

[0006] According to a first aspect of the present invention, a display system is provided, the display system comprising: an illumination system configured to emit at least partially coherent light; a spatial light modulator SLM illuminated by the illumination system and for applying a modulation pattern to the illumination light, the SLM configured to form a single modulation pattern H representing a plurality of image fields simultaneously, wherein the information associated with each of the plurality of image fields occupies a different portion of the Fourier transform F(H) of H; an optical system that receives the light modulated by the SLM and is arranged to create a Fourier plane of the SLM; and a spatial filter substantially positioned in the Fourier plane of the SLM, the spatial filter comprising a plurality of regions, each region corresponding to a portion of F(H) representing an image field, and each region configured to allow light associated with the image field corresponding to that region to pass through. In a single modulation pattern, the information associated with the image field having the greatest perceptual significance to the viewer occupies the largest portion of F(H).

[0007] Generally, the Fourier transform F(H) of H can be divided or decomposed into multiple parts, each part representing information from a single image field, and each part is substantially filtered by spatial filters to prevent perceptible interference between that part and the rest for the viewer. The independent image fields corresponding to each part can then be coherently added by the eye. Furthermore, by assigning larger parts of F(H) to the image field with the greatest perceptual significance for the viewer, the quality of the perceived image can be improved using the characteristics of the human eye.

[0008] Please understand that the information associated with each image field in F(H) does not necessarily need to correspond precisely to the Fourier transform of the image field, for example, by performing possible cropping and / or adding a focal term.

[0009] Individual regions of a spatial filter may overlap. For example, due to wavelength-dependent diffraction effects, regions in a spatial filter may overlap each other. The color of the spatial filter may differ where regions overlap; for example, if a red region overlaps with a green region, the overlap may appear yellow. References to light in the image field corresponding to the regions of the spatial filter include such arbitrary overlaps; for example, a red region may include a portion of the spatial filter that appears red and a portion of the spatial filter that appears yellow where the red region overlaps with the green region.

[0010] References to spatial filters, which are configured to "allow light to pass through," are used in the sense of filters with respect to light that may pass through downstream optical elements. Light can "pass through" by transmission or reflection.

[0011] Each image field can be a color channel of an image. Here, throughout this disclosure, references to “color” include not only colors that can be represented by light of a single wavelength, but also perceptual colors. Perceptual colors are those that a viewer can perceive through a combination of wavelengths. Thus, a color channel may be a color such as magenta, which is composed of red and blue wavelengths of light. Similarly, a color channel may be white, which is the viewer’s perception of light with wavelengths that span the entire visible spectrum. It should be understood that a spectral distribution of a light source within a certain range can be perceived as white; that is, there is no single, inherent specification for “white light.”

[0012] Multiple image fields may include at least three image fields. At least three image fields may allow the most perceptually significant color field (which may be white, as mentioned above in some examples) to occupy the largest portion of F(H), for example, to enable the display of a color image and improve the perceived quality of the image.

[0013] In one example, multiple image fields include a red image field, a green image field, and a blue image field, with the information associated with the green image field accounting for the largest portion of F(H). By allocating the largest portion of F(H) to the green image field, the color to which the human eye has the greatest sensitivity receives proportionally more information than the red and blue image fields.

[0014] Similarly, in another example, multiple image fields include a substantially white light field, and the white or substantially white light field accounts for the largest portion of F(H). When a substantially white field is included in the display system, the human eye is most sensitive to the overall brightness provided by the substantially white field. In this case as well, it receives proportionally more information than the other fields. The reference to "substantially" white here allows for colors that are generally perceived as white.

[0015] If there is a white image field, the multiple image fields may further include a red image field, a green image field, and a blue image field. Full color may still be provided through the red, green, and blue image fields. In that case, the information associated with the red image field, the information associated with the green image field, and the information associated with the blue image field occupy the same portion of F(H). Each field may be relatively small compared to the white field, since the majority of the luminance information is provided by the white field. Alternatively, the green image field may occupy a larger portion of F(H) than the red and blue image fields.

[0016] It may be advantageous for multiple image fields to include a yellow image field and / or a cyan image field. The human eye is sensitive to variations in chromaticity and can therefore detect variations in yellow and / or cyan when formed from combinations of red, green, and blue. By providing yellow and / or cyan light sources, a more uniform perceived chromaticity of those colors may be provided, potentially improving image quality. Further light sources and image fields corresponding to other colors such as magenta and orange may also be provided.

[0017] In these and other examples, white light can have wavelengths in the range of 450 nm to 750 nm. Red light can have wavelengths in the range of 610 nm to 750 nm, such as 617 nm or 635 nm. Blue light can have wavelengths around 400 nm to 495 nm, for example, 450 nm. Green light can have wavelengths in the range of 495 nm to 570 nm or 520 nm to 560 nm, such as about 520 nm. Yellow light can have wavelengths in the range of 565 nm to 590 nm, such as about 580 nm. Cyan light can have wavelengths in the range of 485 nm to 505 nm, such as about 505 nm.

[0018] Illumination systems can be provided in any suitable manner. In some examples, an illumination system includes multiple light sources, such as from separate discrete light sources having the required wavelengths. Multiple light sources can also be provided from a single light source by a suitable optical system, such as by forming multiple images of the light sources. In other examples, an illumination system may include a single light source, such as a white light source that can also provide white light, as well as red, green, blue, and / or other colored light. When white light, or light in other broader wavelength ranges, is used to provide light in a narrower bandwidth, that light can be filtered before or after the SLM in the optical path. For example, filtering of a white light source to a specific color channel may be combined with a spatial filter. Other combinations are also possible.

[0019] As discussed in WO2023 / 227902, incorporated herein by reference for all purposes, the coherence level of the illumination system can limit the perceived depth it provides in a holographic display. Therefore, a holographic display may provide a dedicated green light source to convey a wider range of depth information, or derive red and blue light sources from a white light source with a reduced range of depth information. Other combinations are also possible.

[0020] According to a second aspect of the present invention, a display system, wherein the display system is A lighting system configured to emit at least partially coherent light, A spatial light modulator (SLM) illuminated by a lighting system and for applying a modulation pattern to the illumination light, An optical system that receives light modulated by an SLM and is arranged to create the Fourier plane of the SLM, A spatial filter effectively placed in the Fourier plane of an SLM, Includes, The SLM is configured to form a single modulation pattern H that simultaneously represents at least a first image field occupying a first portion of the Fourier transform F(H) of a single modulation pattern H, and a second image field occupying a different second portion of F(H). A display system is provided in which the spatial filter is configured such that the light corresponding to the first part of F(H) does not coherently interfere with the light corresponding to the second part of F(H), or partially interferes with it.

[0021] Generally, the Fourier transform F(H) of H is split or decomposed into multiple parts, each part contains information from a single image field, and each part is prevented from coherent interference with others by a spatial filter. The corresponding independent image fields of each part can then be coherently added by eye. In some embodiments, partial coherent interference between parts of different wavelengths or overlapping wavelengths, such as the overlap points of the spatial filter, may be acceptable. There may also be partial coherent interference between the white region and other color regions of the spatial filter. These have been found not to have a significant impact on the perceived image quality.

[0022] Such a display system enables the use of a single modulation pattern of the SLM to display multiple image fields because the spatial filter ensures that the image fields do not interfere coherently with each other. The viewer's eye receives the multiple image fields but can perceptually combine them into a single image. For example, the multiple image fields may be different renderings of the same scene with different noise patterns, and the viewer's eye can combine them to average and reduce the perception of noise. In another example, the multiple image fields may be separate color fields of the same scene, and the viewer's eye can combine them to perceive a color image. In a further example, the multiple image fields may be of the same scene, but the viewer's eye can expand the field in which the image can be perceived (sometimes called "eyebox expansion").

[0023] The second part may occupy a larger area of F(H) than the first part. For example, the area of the second part of F(H) is larger than the area of the first part of F(H). This enables giving a larger effective resolution to one color than to another color. For example, a higher effective resolution can be provided by occupying a larger area of F(H) for a perceptually more important color, such as green in the RGB representation of an image or white in the RGBW representation of an image. The diffraction and wavelength scaling effects may mean that the corresponding region in the Fourier plane of the SLM is not necessarily larger. A lower wavelength (such as red) occupies a relatively wider region in the Fourier plane than it does in the mathematical Fourier space.

[0024] It should be understood that the lack of coherent interference can be achieved in several ways, including physically blocking the passage of all light outside the desired region of the Fourier plane by blocking or permitting light of a specific frequency, and in a time - series manner by selectively activating the region of the spatial filter between blocking and permitting the passage of light. In other words, the spatial filter can be configured such that the display of multiple image fields is simultaneous and / or involves a time - series display over the period during which the SLM forms a single modulation pattern.

[0025] Advantageously, this technique has been found to result in at least a two - fold increase in the number of image fields that can be displayed per unit time compared to a display system that relies on displaying a single image field per modulation pattern of the SLM. This can be advantageous when the display system includes an architecture with a relatively slow refresh rate, such as liquid crystal on silicon (LCoS). A further advantage is that it may be easier to increase the resolution of the SLM than to increase its refresh rate. Representing multiple image fields simultaneously with a single modulation pattern reduces the effective resolution of the SLM per image field, but increasing the resolution to compensate for this is relatively easier than increasing the frame rate.

[0026] The display system can offer further advantages over color holographic displays by enabling precise mutual registration of color channels through simultaneous display of color channels. Furthermore, holographic display systems typically use "sequential color" displays, where color fields are displayed sequentially in time, requiring, for example, three modulation patterns of SLMs for a single color image. While such systems are more compact and cost-effective than including an SLM for each color, sequential color displays are known to suffer from "colour-breakup," a problem where the viewer perceives separate images due to changes in the viewer's eye position over time. This display system can mitigate the effects of color-breakup.

[0027] An illumination system may include one or more light sources. These light sources may be, for example, lasers or other coherent light sources, or at least partially coherent light sources including light-emitting diodes (LEDs). One or more light sources may include a single emitter or multiple emitters, and may emit light having a single or multiple wavelengths (and thus act as multiple light sources). A light source may be a physical emitter or an image of an emitter. Some examples may include an optical system configured such that one or more “master” light sources provide multiple light sources, each of which is an image of the “master” light source. In some examples, this is achieved by a microlens array. An illumination system may behave as one or more point light sources. Light sources may be somewhat magnified, but they are localized to some extent by their property of being at least partially (spatially) coherent. A light source point may be a physical point emitter (such as an LED or laser diode), an image of a point emitter, or another form of at least partially coherent illumination such as a laser cavity. The light source can be in front of the SLM (i.e., divergent illumination), at infinity (i.e., collimated illumination), or as a virtual point after the SLM (i.e., convergent illumination).

[0028] The lighting system may include a white light source, such as a white LED. This may provide a white light source directly, or it may provide a color light source through filtering, which may occur before the SLM, such as within the lighting system, or after the SLM, such as a spatial filter. In other words, light sources of different wavelengths (colors) may be provided by a single physical emitter (e.g., a white LED), but different parts of its spectrum (e.g., the red band, the green band, and the blue band) can be treated as separate non-coherent light sources. In this case, the single physical emitter has first and second spectra, but behaves in the same way as having first and second non-coherent light sources whose emission areas coincide.

[0029] SLM can be any modulator or modulation means suitable for modulating the amplitude and / or phase of coherent light, quasi-coherent light, or at least partially coherent light. This includes LCoS devices, digital micromirror devices (DMDs), and liquid crystals. In some embodiments, the SLM is an amplitude-modulated LCoS.

[0030] The optical system may include lenses. The lenses are preferably Fourier lenses and may be formed from multiple elements. In some embodiments, the lenses may be lens arrays, and the lenses, including the arrays, extend across the imaging area. The optical system may form a plane containing the image of the light source(s) after modulation by the SLM. This plane is called the Fourier plane of the SLM. The modulation amplitude in this plane is related to the Fourier transform of the modulation pattern, F(H), but the scale and position of the modulation amplitude further depend on factors including the wavelength of light and the angle of illumination.

[0031] The SLM, optical system, and spatial filter can be aligned along the optical path. For example, in some embodiments, they may be substantially coaxial. Other arrangements are possible, for example, a bent optical path with mirrors and / or prism elements in the optical path to allow for the most compact possible arrangement.

[0032] A spatial filter can have any suitable configuration, such as using the principle of transmission or reflection. A transmission spatial filter can define a set of apertures through which light can pass and which generally block or otherwise prevent light from passing outside the aperture (for example, a spatial filter may be configured to absorb light outside the aperture or to reflect it elsewhere outside the optical path). A reflection spatial filter may include a region that reflects light toward the optical path to allow light to pass through, or a region that reflects light away from the optical path to block the passage of light.

[0033] The illumination system may include a first light source and a second light source, the first and second light sources being non-coherent to each other, with light passing through a first region defined by a spatial filter and corresponding to a first portion of F(H) originating from the first light source, and light passing through a second region defined by a spatial filter and corresponding to a second portion of F(H) originating from the second light source. Thus, the display system may be able to display multiple images simultaneously using light of the same or different wavelengths.

[0034] Each image field may correspond to each color channel of a multicolor image, meaning that each of the multiple image fields is associated with the same scene. The first light source may have a first wavelength, and the second light source may have a second wavelength different from the first. The first image field is for display at the first wavelength, and the second image field is for display at the second wavelength. The first region defined by the spatial filter includes a spectral filter that allows the first wavelength to pass through. The second region defined by the spatial filter includes a spectral filter that allows the second wavelength to pass through. That is, multiple image fields at each wavelength can be separated in the Fourier plane using spectral filters. In this way, a color image can be displayed. The SLM displays multiple image fields simultaneously that are simultaneously filtered by spatial filters. Problems such as color breakup and color registration are greatly reduced or eliminated.

[0035] The number of image fields can be extended to any number of component color image fields, such as three, four, or more. It is common to represent a color image for display as a combination of three component image fields. Thus, a single modulation pattern may also simultaneously represent a third image field that occupies a third portion of F(H) distinct from the first and second portions. In this case, the spatial filter may be further configured to filter the light corresponding to at least the third portion. In some embodiments, the illumination system includes a third light source having a third wavelength, and the spatial filter defines a third region corresponding to the third portion of F(H), and the third region includes a spectral filter that allows the third wavelength to pass through. In some embodiments, the first, second, and third wavelengths correspond to red light, green light, and blue light (also called RGB), respectively. Red may have wavelengths between 610 nm and 750 nm, such as 617 nm or 635 nm. Blue light may have wavelengths around 400 nm to 495 nm, for example, 450 nm. Green light can have wavelengths in the range of 495nm to 570nm or 520nm to 560nm, such as approximately 520nm. While an example of RGB is shown, other component colors may also be used. Such a three-color display system offers a threefold improvement in the number of image fields per unit time compared to a sequential color display.

[0036] Another example may use four image fields, each of which may correspond to a distinct color. In this case, a single modulation pattern also simultaneously represents a fourth image field occupying a fourth portion of F(H) distinct from the first, second, and third portions, and the spatial filter is further configured to filter out light corresponding to at least the fourth portion, with each of the first, second, third, and fourth image fields corresponding to a distinct color. The term "distinct" is used to mean that each of the first, second, third, and fourth image fields corresponds to a color distinct from the others. In some embodiments, one of the first, second, third, and fourth image fields corresponds to a white image field. In other embodiments, the distinct color may be red, green, blue, and yellow, or other distinct chromaticities.

[0037] The second part may occupy a larger area of ​​F(H) than the third part. The area of ​​the second part of F(H) may be larger than the area of ​​the third part of F(H). Therefore, the second part may have a larger area than both the first and third parts.

[0038] In this embodiment, the first portion corresponds to the red image field, the second portion to the green image field, and the third portion to the blue image field. For example, the first wavelength corresponds to red light, the second wavelength to green light, and the third wavelength to blue light. In this case, the first portion may occupy a larger area F(H) than the second portion. The area of ​​the second portion may be larger than the combined areas of the first and third portions. Unlike sequential color displays, displays that simultaneously display multiple color image fields do not need to display equal areas (in the Fourier plane) for each color, as occurs in sequential color displays. In this case, the spatial filter allows more green light to be transmitted than red and blue light. This gives green light, which is perceptually more important than red and blue light, a larger allocation of the available "information bandwidth". Similarly, the second portion may correspond to white light in an RGBW representation, allowing for a larger allocation of "information bandwidth" to white light, which is the most perceptually important. In some embodiments, the area of ​​the second portion is approximately twice the combined area of ​​the first and third portions. In the RGB example, this prioritizes the transmission of green light over the transmission of red and blue light. Other configurations are also possible. In some embodiments, the area of ​​the second portion is greater than twice the combined area of ​​the first and third portions. In embodiments that do not use red, green, and blue light, a larger area may be allocated to the color that is most perceptually important.

[0039] The area of ​​the first part of F(H) may be larger than the area of ​​the third part of F(H). That is, in the RGB example, the spatial filter may allow more Fourier transform area to be used for red light than for blue light. This can improve the image quality of the display system because red light, which is perceptually more important than blue light, is given priority. In embodiments that do not use red, green, and blue light, a larger area may be allocated to the color that is perceptually most important.

[0040] The region of the spatial filter corresponds to the F(H) portion. In the spatial filter, the size of the region may be affected by wavelength scaling and / or diffraction effects. The area of ​​the second region corresponding to the second portion may be larger than the combined areas of the first and third regions corresponding to the first and third portions. That is, the area of ​​the second region may be larger than the first and third regions even after taking wavelength scaling and / or diffraction effects into account.

[0041] In some embodiments, the second region may correspond to the green image field, and the first region may correspond to the red image field, and therefore the second region is no larger than the first region, solely due to wavelength and / or diffraction effects. In other words, in such embodiments, the green region being larger in area than the red region of the spatial filter means that it corresponds to a larger portion of F(H) than the first portion of F(H). In some embodiments, the second portion may correspond to the white image field.

[0042] A first region corresponding to a first portion of F(H) and a second region corresponding to a second portion of F(H) may overlap. Due to wavelength scaling and possibly differences in the arrangement of the first and second light sources within the illumination system, the physical positions of the first and second regions in the spatial filter may overlap. This does not adversely affect image quality if there is no coherent interference effect between the first and second light sources where they overlap, such as when the first and second light sources are non-coherent with respect to each other due to having different wavelengths. Such overlap can also be beneficial. Firstly, the overlap reduces the area of ​​the Fourier plane corresponding to different portions of F(H). This can enable other techniques such as time-series eyebox magnification. Secondly, alignment between individual colors and the viewer's pupil may also become easier to achieve and maintain. In one embodiment, the illumination system includes a first and second light source arranged such that the first region in the spatial filter is substantially contained within the second region.

[0043] If the first and second light sources are configured to emit light having different first and second wavelengths, the spatial filter may include a spectral filter for each, as described above. In the overlapping region, the spectral filter may allow transmission of a portion(s) of the visible spectrum that includes both the first and second wavelengths. If the first, second, and third regions substantially overlap in the Fourier plane, the spatial filter may define an aperture in the overlap to allow transmission of all colors. In other words, if all three colors overlap in the Fourier plane, a spectral filter may not be necessary.

[0044] A spatial filter can define a region having a shape with a maximum dimension aligned with the direction of consecutive horizontal and / or vertical diffraction orders in the Fourier plane. “Maximum dimension” is used to refer to the longest continuous straight line that can be contained within the shape. For example, in squares and rectangles, the diagonal is the maximum dimension. Many SLMs feature an array of nearly square pixels. Illumination of an SLM results in a diffraction pattern containing a central zero-order diffraction peak and regularly spaced higher-order diffraction peaks that together form a grid of diffraction peaks in the Fourier plane. By aligning the maximum dimension of the aperture with the direction of consecutive horizontal and / or vertical diffraction orders, higher horizontal and / or vertical spatial frequencies can be transmitted by the spatial filter. In other words, horizontal and / or vertical spatial frequencies may be filtered less. This is useful when the image field contains high horizontal and / or high vertical spatial frequencies, as well as when the image field contains text.

[0045] The region may be a square, or a square rotated by 45 degrees such that its diagonal aligns with the direction of the consecutive horizontal and / or vertical diffraction orders of the Fourier plane. The region may have an "I" or "H" shape, rotated so that its maximum dimensions align with the direction of the consecutive horizontal and / or vertical diffraction orders of the Fourier plane. In this case, the "I" or "H" shape is for perceptually most important colors, such as green. Less perceptually important colors, such as red and blue image fields, are smaller squares, rotated by 45 degrees and cut out from a larger square to form an "I" or "H" shape for the perceptually most important shape.

[0046] In embodiments where the spatial filter defines three apertures, the first, second, and third apertures can form a shape having all of their respective maximum dimensions aligned with the directions of consecutive horizontal and / or vertical diffraction orders in the Fourier plane.

[0047] Some embodiments may use a spatial filter that selectively allows light corresponding to the first and second parts to pass through at different times. This is useful when the same light source is used for each part. In this case, coherent interference can be prevented by activating a single region of the spatial filter, or a set of regions with mutually non-coherent light sources, at any given time. Manufacturing such shutters for fast switching may be easier than with SLMs. By switching the first and second shutters sequentially between states, the first and second parts of F(H) can be transmitted within the period during which a single modulation pattern is formed by the SLM.

[0048] A spatial filter may include a spectral filter. A spectral filter may have regions corresponding to image fields, each having a passband corresponding to the wavelength(s) of each image field. In some embodiments, the spectral filter may be combined with the shutter so that the shutter and / or spectral filter can define regions of the spatial filter that light selectively allows to pass through.

[0049] In a third embodiment, the display system includes an illumination system configured to emit at least partially coherent light; a spatial light modulator SLM illuminated by the illumination system for applying a modulation pattern to the illumination light; an optical system for receiving the light modulated by the SLM and arranged to create a Fourier plane of the SLM; and a spatial filter substantially located in the Fourier plane of the SLM. The SLM is configured to form a single modulation pattern H that simultaneously represents at least a first image field occupying a first portion of the Fourier transform F(H) of H and a second image field occupying a different second portion of F(H). The spatial filter includes a first shutter and a second shutter that can be switched between a state that allows light to pass through and a state that blocks light, the first shutter corresponding to a first portion of F(H) and the second shutter corresponding to a second portion of F(H). During use, the system is configured such that one of the first and second shutters is in a state that allows light to pass through at any given time, and both the first and second shutters are in a state that allows light to pass through during each period within the period in which the SLM forms a single modulation pattern. The light associated with the first portion of F(H) cannot coherently interfere with the light associated with the second portion of F(H) because the light associated with the second portion of F(H) is blocked by the spatial filter, and vice versa.

[0050] A single modulation pattern H may be a first modulation pattern generated in a first time, in which case the SLM may be configured to form a second single modulation pattern H' in a second time, different from the first time. The second single modulation pattern simultaneously represents a first and a second further image field, each occupying a different portion of the Fourier transform F(H') of H'. The spatial filter is configured to allow at least a first portion of F(H) to pass through in the first time, and the spatial filter is further configured to allow at least a first portion of F(H') corresponding to the further first image field to pass through in the second time. In allowing portions of F(H) and F(H') to pass through, the spatial filter may block at least a portion of F(H) that is not needed, such as zero-order diffraction peaks and higher diffraction orders. In other embodiments, conjugate terms may be blocked additionally or alternatively, such as when the SLM is an amplitude SLM. The spatial filter may also be further configured such that F(H') is blocked by the spatial filter in the first time and F(H) is blocked by the spatial filter in the second time.

[0051] Displaying images sequentially in different regions of the Fourier plane increases the effective size of the eyebox. By rapidly and sequentially displaying light fields at different positions at a relatively high speed, the viewer perceives one larger image through visual persistence. The spatial filter may include one or more blocking elements or controllable shutters configured to allow selective passage and blocking of light from each portion of F(H) and F(H') at any given time.

[0052] In some embodiments, the illumination system is a first illumination system, and the display system further includes a second illumination system configured to emit light that is at least partially coherent and spatially offset from the first illumination system. A single modulation pattern H may be a first modulation pattern generated in a first time, and the SLM may be configured to form a second single modulation pattern H' in a second time different from the first time, the second single modulation pattern simultaneously representing a first further image field and a second further image field, each occupying a different portion of the Fourier transform F(H') of H'. A spatial filter may be configured to allow at least a portion of the light from the first illumination system to pass through in the first time, and to allow at least a portion of the light from the second illumination system to pass through in the second time. In allowing portions of F(H) and F(H') to pass through, the spatial filter may block at least a portion of F(H) that is not needed, such as zero-order diffraction peaks and higher diffraction orders. Other embodiments may additionally or alternatively block conjugate terms, such as when the SLM is an amplitude SLM. The spatial filter may also be further configured such that, in a first time, light from the second illumination system is not allowed to pass through, and in a second time, light from the first illumination system is not allowed to pass through.

[0053] The spatial filter may include first and second shutters that can be switched between a state that allows light to pass through and a state that does not allow light to pass through. At a first time, the first shutter may be in a state that allows at least a portion of the light from a first illuminating system to pass through, and the second shutter may be in a state that does not allow light from a second illuminating system to pass through; at a second time, the second shutter may be in a state that allows at least a portion of the light from a second illuminating system to pass through, and the first shutter may be in a state that does not allow light from a first illuminating system to pass through.

[0054] The first and second lighting systems may each include one or more light sources (e.g., RGB light sources), and by spatially offsetting the first and second lighting systems, images are formed at different positions in the viewer's pupil plane. This makes it possible to change the position of the image in this plane by changing the lighting system used.

[0055] In some embodiments, the display system may further include a pupil tracking system configured to determine the position of the viewer's pupil, and a processing system configured to determine which of a first or second lighting system corresponds to the determined position of the viewer's pupil, and to control the first and second lighting systems based on the determined pupil position. This enables pupil tracking in a simpler way with fewer (perhaps none) moving components. The pupil tracking system is used to determine the position of the pupil so that the appropriate lighting system(s) are activated to produce an image at that position. Different lighting systems may be activated as the viewer's pupil moves. In some embodiments, the processing system may be a dedicated processing system associated with the pupil tracking system, or it may be part of the pupil tracking system. In other embodiments, the processing system may be a general processing system for the display system.

[0056] The display system may include one or more master light sources, where the first illumination system includes a first image from one or more master light sources, and the second illumination system includes a second image from one or more master light sources. In some embodiments, the display system further includes a lens array, where the light source of the first illumination system is an image from one or more master light sources formed by a first lens of the lens array, and the light source of the second illumination system is an image from a master light source formed by a second lens of the lens array.

[0057] The display system may include additional spatial filters positioned after the lens array to control which of the first and second lighting systems illuminates the SLM.

[0058] According to a fourth aspect of the present invention, a spatial filter for placement in the Fourier plane of a spatial light modulator in a display system, the spatial filter defines a first region through which a first subset of the visible electromagnetic spectrum can pass, and a second region through which a second subset of the visible electromagnetic spectrum can pass, wherein the first subset of the visible electromagnetic spectrum differs from the second subset of the visible electromagnetic spectrum, and the first and second regions at least partially overlap.

[0059] A spatial filter according to the fourth embodiment may be used in a display system according to the first, second, or third embodiment. The spatial filter makes it possible to display two image fields at different wavelengths simultaneously for a single modulation pattern formed by the SLM.

[0060] The spatial filter may define a third region that allows transmission of a third subset of the visible electromagnetic spectrum, distinct from the first and second subsets of the visible electromagnetic spectrum, to pass through, wherein the first subset of the visible electromagnetic spectrum includes red light, the second subset includes green light, and the third subset includes blue light, and the area of ​​the second region is greater than the combined area of ​​the first and third regions.

[0061] In other words, the spatial filter can allow more green light to be transmitted than red and blue light. This gives more of the available "information bandwidth" to green light, which is perceptually more important than red and blue light. In some embodiments, the area of ​​the second part is about twice the combined area of ​​the first and third parts. This gives priority to the transmission of green light over the transmission of red and blue light.

[0062] The area of ​​the first region may be larger than the area of ​​the third region. That is, the spatial filter may allow more red light to be transmitted than blue light. As a result, the transmission of red light, which is perceptually more important than blue light, is prioritized, improving the image quality of the display system and, as mentioned above, potentially increasing the effective frame rate.

[0063] It should be understood that the spatial filter may also have any of the features described above for the first, second, or third embodiment. The spatial filter may form part of a display system.

[0064] The display systems described above have many potential applications, including head-mounted displays and head-up displays. The increase in effective frame rate also makes them useful for holographic displays, enabling techniques such as time-series noise averaging and eyebox expansion.

[0065] A fifth aspect of the present invention provides a method comprising: determining a first modulation pattern H1 corresponding to a first image field, wherein the Fourier transform F(H1) of H1 occupies a first portion of the Fourier domain; determining a second modulation pattern H2 corresponding to a second image field, wherein the Fourier transform F(H2) of H2 occupies a second portion of the Fourier domain different from the first portion; simultaneously displaying H1 and H2 on an SLM by a single modulation pattern; illuminating the SLM with at least partially coherent light to produce a modulated output; and filtering the modulated output using a spatial filter substantially positioned in the Fourier plane of the SLM and configured such that the light corresponding to F(H1) does not coherently interfere with the light corresponding to F(H2), or partially interferes with it. The second portion may be larger than the first portion.

[0066] The method offers the aforementioned advantage of allowing more image fields to be displayed within the period during which the SLM is forming a single modulation pattern. The method may be particularly advantageous when used in SLM architectures with relatively low refresh rates, such as LCoS. Additional image fields (per unit time) can be used in conjunction with techniques such as different color image fields, noise averaging, and eyebox expansion.

[0067] The first image field may correspond to a first subset of the visible electromagnetic spectrum. The second image field may correspond to a second subset of the visible electromagnetic spectrum, where the first subset is different from the second subset. That is, the method may use light of different wavelengths to produce a single polychromatic image perceived by the viewer. The different wavelengths may also overlap, such as overlapping but different wavelength ranges. In other words, the different wavelengths may or may not be mutually exclusive.

[0068] The spatial filter may include a first region corresponding to a first portion of F(H) and a second region corresponding to a second portion of F(H), wherein the first and second regions partially overlap. In this case, the light allowed to pass through the first region may originate from a first at least partially coherent light source, and the light allowed to pass through the second region may originate from a second at least partially coherent light source, wherein the first and second at least partially coherent light sources may be noncoherent to each other, and the first and second at least partially coherent light sources are arranged such that the first and second regions at least partially overlap in the Fourier plane.

[0069] H1 and H2 may be displayed in a first time, and a first illumination system including at least partially coherent light sources illuminates the SLM in a first time, the method further includes determining a third modulation pattern H3 corresponding to a third image field, determining a fourth modulation pattern H4 corresponding to a fourth image field, simultaneously displaying H3 and H4 on the SLM by a further single modulation pattern in a second time different from the first time, and illuminating the SLM with a second illumination system including a second at least partially coherent light source, the second illumination system being spatially offset from the first illumination system. A spatial filter is further configured to allow light corresponding to H1 and H2 to pass through in a first time, and to allow light corresponding to H3 and H4 to pass through in a second time. In allowing H1 and H2 and portions of H3 and H4 to pass through, the spatial filter may block at least some unwanted parts, such as zero-order diffraction peaks and higher diffraction orders. Other embodiments may additionally or alternatively block conjugate terms, such as when the SLM is an amplitude SLM. The spatial filter may be further configured such that, in a first time, light corresponding to H3 and H4 is not allowed to pass through, and in a second time, light corresponding to H1 and H2 is not allowed to pass through.

[0070] This method may further include determining the position of the viewer's pupil and controlling first and second lighting systems based on the determined pupil position.

[0071] According to a sixth aspect of the present invention, a display system is provided comprising first and second illumination systems, a spatial light modulator (SLM), an output optical system, a pupil tracking system, and a processing system. The first illumination system is configured to generate a first set of at least partially coherent beams of light. The second illumination system is configured to generate a second set of at least partially coherent beams of light and is spatially offset from the first illumination system. The SLM is positioned to be illuminated by the first set of light beams and the second set of light beams. Each of the first and second sets of light beams is incident on the SLM at a different angle. The output optical system is positioned to receive the light modulated by the SLM. The pupil tracking system is configured to determine the position of the viewer's pupil. The processing system is configured to determine at least one active beam from the first and second sets of beams corresponding to the determined position of the viewer's pupil and to control the first and second illumination systems so that at least one active beam is used to illuminate the SLM.

[0072] The first set of light beams and the second set of light beams, each at least partially coherent, may each include one or more light beams.

[0073] Such a display system enables pupil tracking without complex mechanical mechanisms. By generating multiple light beams, the display system can display images over a wider area. Specifically, by illuminating the SLM at different angles, the generated images are distributed across the plane where the viewer's pupil is located, and which image to use can be selected based on the user's pupil position.

[0074] The pupil tracking system is used to determine the position of the pupil and activate the appropriate beam(s) to create an image at that location, rather than covering an entire large area simultaneously. Based on the determined pupil position, specific individual light beams, or subsets of light beams, may be selected so that the image(s) are generated at the pupil, or at least near the pupil.

[0075] The display system may also include a spatial filter, as described with reference to at least the first to fourth embodiments. The illumination system may be controllable so that at least one of the beams is emitted at any given time. The illumination system is spatially separated so as to be incident on the SLM at different angles.

[0076] In some embodiments, the first and second illumination systems may each include a set of light sources, each set of which may include as few as one light source. Each light source from the first and second sets of light sources may be configured to produce a single beam of light that is at least partially coherent. The first and second illumination systems may also be parts of an array of light-emitting diodes (LEDs). Since the light originates from the corresponding light sources, each image produced in the pupil is relatively bright.

[0077] However, multiple light sources / illumination systems may not be suitable, perhaps for cost and / or space reasons. The display system may further include one or more master light sources, where the first set of light sources is one or more first images of one or more master light sources, and the second set of light sources is one or more second images of one or more master light sources. In some embodiments, the display system may include a lens array, where the first image is formed by a first lens of the lens array, and the second image is formed by a second lens of the lens array. The display system may include a spatial filter positioned after the lens array to control whether the first or second illumination system illuminates the SLM. This provides an alternative method to using multiple light sources and can overcome the difficulties of managing a large number of light sources.

[0078] The shutter of the spatial filter can be switched between a state that allows light to pass through and a state that does not allow light to pass through. The shutter may be controllable by the processing system and therefore may be switched based on a determined pupil position.

[0079] The processing system may be further configured to control the first and second illumination systems such that light from one of the first and second sets of light beams is incident on the SLM at any given time.

[0080] Further features and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention, given only as examples, with reference to the accompanying drawings. [Brief explanation of the drawing]

[0081] [Figure 1] An example of a display system is shown. [Figure 2] Figure 1 shows an exemplary decomposition of a Fourier domain into parts for use in a display system. [Figure 3]Figure 1 shows an exemplary decomposition of a Fourier domain into parts for use in a display system. [Figure 4] This is an example of a physical space filter for placement in the Fourier plane of the SLM in the display system shown in Figure 1. [Figure 5] This is an example of a physical space filter for placement in the Fourier plane of the SLM in the display system shown in Figure 1. [Figure 6] Figure 1 shows an exemplary decomposition of a Fourier domain into parts for use in a display system. [Figure 7] This is an example of a physical space filter for placement in the Fourier plane of the SLM in the display system shown in Figure 1. [Figure 8] Figure 1 shows an exemplary decomposition of a Fourier domain into parts for use in a display system. [Figure 9] This is an example of a physical space filter for placement in the Fourier plane of the SLM in the display system shown in Figure 1. [Figure 10] Another exemplary display system is shown. [Figure 11] Figure 10 shows an exemplary physical space filter for placement in the Fourier plane of the SLM in the display system. [Figure 12] This is another exemplary physical space filter for positioning in the Fourier plane of an SLM in a display system containing six light sources. [Figure 13] Figure 1 shows an exemplary decomposition of a Fourier domain into parts for use in a display system. [Figure 14] Figure 1 shows an exemplary decomposition of a Fourier domain into parts for use in a display system. [Figure 15] This is an example of a physical space filter for placement in the Fourier plane of the SLM in the display system shown in Figure 1. [Figure 16] Figure 1 shows an exemplary decomposition of a Fourier domain into parts for use in a display system. [Figure 17A] This is an example of a physical space filter for placement in the Fourier plane of the SLM in the display system shown in Figure 1. [Figure 17B] These are diagrams of the physical space filter regions shown in Figures 17A and 19A, through which light corresponding to a portion of the Fourier domain in Figures 16 and 18 passes. [Figure 18] Figure 1 shows an exemplary decomposition of a Fourier domain into parts for use in a display system. [Figure 19A] This is an example of a physical space filter for placement in the Fourier plane of the SLM in the display system shown in Figure 1. [Figure 19B] These are diagrams of the physical space filter regions shown in Figures 17A and 19A, through which light corresponding to a portion of the Fourier domain in Figures 16 and 18 passes. [Figure 20] The method is shown by the example. [Figure 21] An exemplary virtual reality display system is shown. [Figure 22] Further exemplary display systems are shown. [Figure 23] Further exemplary display systems are shown. [Figure 24] An exemplary holographic optical engine is shown. [Modes for carrying out the invention]

[0082] In many display systems, it is desirable to display more image fields per unit of time. For example, displaying more image fields per unit of time can improve the smoothness of the appearance of a video and / or allow the use of image quality enhancement techniques such as noise averaging and eyebox expansion.

[0083] Image quality is crucial in display systems, and therefore, some display systems include display devices that contribute to improved static image quality. For example, liquid crystal on silicon (LCoS) devices often have relatively high contrast ratios, can reproduce deep blacks, and do not produce rainbow artifacts. However, LCoS devices typically suffer from relatively low refresh rates, especially compared to other display architectures such as digital micromirror devices (DMDs). Augmented reality (AR) and virtual reality (VR) displays typically benefit from higher refresh rates than static displays due to the user's head movements. Therefore, using LCoS devices in AR and VR can result in unacceptable stuttering of the displayed image, which can lead to disorientation and nausea.

[0084] The technology described herein increases the number of image fields that can be displayed per unit time in any SLM-based display system. This increase in the number of image fields can be used to provide, for example, smoother video content, further noise averaging, and eyebox expansion, one or more of these effects. The technology can also reduce issues such as color breakup. The technology described herein is not limited to use in AR and VR systems, but is also relevant to static displays such as HUDs and projectors.

[0085] Figure 1 shows a display system 100 in general terms. The display system 100 includes an illumination system 102 configured to emit at least partially coherent light. The illumination system 102 is configured to produce light that is at least partially coherent at one or more wavelengths (for example, corresponding to red, green, and blue). The illumination system 102 may include one or more light sources. Each of the one or more light sources may be configured to produce at least partially coherent light at one or more wavelengths. The one or more light sources may include, for example, a laser module or an LED.

[0086] The condenser lens 104 is positioned to generate quasi-collimated light 106 from the illumination system 102. “Quasi-collimated” should be understood as meaning that the light does not need to be perfectly collimated, but may diverge slightly or converge slightly. The SLM 108 is positioned to be illuminated by the quasi-collimated light 106. The SLM 108 is a device that generates a modulation pattern H by manipulating the properties of the incident light to change spatially. The SLM 108 may be configured to modulate at least one of the phase and amplitude of the light. The SLM 108 may be, for example, a digital micromirror device (DMD), a liquid crystal display (LCD), and an LCoS such as amplitude LCoS or phase LCoS. In Figure 1, the SLM 108 is shown as a transmissive type for simplicity of explanation, but it should be understood that it can be either transmissive or reflective.

[0087] The optical system 110 is configured to generate the Fourier transform, F(H), of the modulation pattern generated by the SLM 108. Generally, the optical system 110 may include any optical element(s) that generate the Fourier transform of the incident light field. For example, the optical system can function as a Fourier lens and generate the Fourier transform of the light field in a given plane in the optical path. The plane in which the Fourier transform of the light field is generated is called the Fourier plane. Referring to Figure 1, the Fourier plane can be thought of as the position of the image of a point light source generated by the illumination source 102.

[0088] The spatial filter 112 is positioned in the Fourier plane of the optical system. More generally, the spatial filter 112 is positioned in or near the Fourier plane of the SLM 108. The configuration of the display 100 is such that the Fourier transform F(H) of the modulation pattern from the SLM is formed in a plane that coincides with the position of the spatial filter 112. This plane is the Fourier plane of the SLM 108, which is imaged by the optical system 110.

[0089] The SLM 108 is configured to form a modulation pattern H from quasi-collimated light 106 received from an illumination source via a condenser lens 104. In this disclosure, a single modulation pattern of the SLM simultaneously generates two or more image fields such that F(H) contains portions corresponding to two or more image fields. As will be described in more detail below, each image field may correspond to light received from its own light source (included in the illumination system 102), or it may be formed using a single light source.

[0090] The spatial filter 112 essentially demultiplexes multiple image fields so that they can be added non-coherently to the viewer's eye, and is arranged and / or configured to allow the passage of each portion of F(H) associated with each image field. Multiple independent image fields can be viewed while the SLM 108 forms a single modulation pattern. Thus, the display system is not limited by the refresh rate of the SLM 108, and the number of image fields per unit time is defined by a combination of the refresh rate of the SLM 108 and the number of image fields that can be displayed simultaneously using a single modulation pattern of the SLM 108. Some specific examples will be described later.

[0091] Here, we will describe in more detail how multiple image fields can be displayed simultaneously by a single modulation pattern of the SLM, and how multiple image fields can be demultiplexed using a spatial filter placed in the Fourier plane of the SLM. [Simultaneous image generation]

[0092] The Fourier transform of a target modulation pattern can be easily computed, and therefore its range within the Fourier plane can also be computed. Algorithms such as Gerchberg-Saxton, Fienup, Fidoc, Input-Output, Liu-Tagizadeh, and the Hybrid Iterative Fourier Transform (HIFTA) algorithm are known, and these algorithms can compute or determine modulation patterns targeting specific regions of the Fourier plane.

[0093] The complexity lies in the fact that SLMs can only generate quantized representations of the desired target light field. For example, consider a hologram for a display, typically calculated first as a "fully complex" modulation pattern, containing an array of values ​​corresponding to each element (pixel) on the surface of the display device. Each value is a complex number with its own phase and amplitude. However, many display systems used for computer-generated holographic images, such as DMDs and LCoS SLMs, have a finite range of values ​​they can reproduce.

[0094] Quantized modulation pattern, H Q It is displayed by quantizing an initial all-complex hologram, which is calculated or determined using known techniques for display. Holographic display systems typically include lenses that, when viewed, cause the viewer's eye to perform an inverse Fourier transform, creating the Fourier transform of the modulation pattern displayed on the SLM.

[0095] This disclosure is based on the position called the Fourier plane of the SLM. Q The Fourier transform of F(H Q This utilizes the observation that an optical system can be used to form a plane in which the complex amplitude is described by the Fourier transform of the complex amplitude in the SLM, potentially scaling the multiplicative spherical phase term, or including its modulo.

[0096] The Fourier transform of a spatial function (for example, the target light field, H, is a spatial function H≡H(x,y)) is its respective frequency component, k x and k y Decompose the function into its constituent parts.

[0097] This disclosure utilizes the fact that an SLM can form a single modulation pattern that simultaneously represents two or more image fields, each targeting a different region of the Fourier plane. Spatial filters are used in this process to prevent coherent interference in the target regions. Thus, F(H) includes portions corresponding to each of the two or more image fields, which can be filtered so that the individual image fields reach the viewer's eye without coherent interference.

[0098] The display system is configured to prevent coherent interference between parts, so modulation patterns for each image field displayed simultaneously can simply be added. The effects of other image fields are filtered out in the Fourier domain, for example, by using a spatial filter in the Fourier plane formed by the optical system.

[0099] Light associated with multiple image fields must not interfere coherently, or only partially. Otherwise, the interference effect will render multiple images illegible. Coherent interference can be avoided by altering the temporal and / or spatial coherence of the light sources in the illumination system. In some embodiments, each of the multiple image fields may be illuminated by light from each light source in the illumination system. Multiple light sources can be used if they are non-coherent to each other, i.e., the light from each light source does not undergo coherent interference.

[0100] To prevent this coherent interference, spatial filters may be used, positioned in the Fourier plane and defining a specific configuration of a region or aperture. An exemplary spatial filter 112 is shown in a side view of Figure 1. The region of the spatial filter has a physical extent corresponding to the region of the Fourier plane that each of the multiple image fields is targeting. The spatial filter restricts the transmission of specific spatial frequencies. Each region allows light corresponding to each part of the Fourier domain to pass through the filter and thus reach the viewer's eye, with the image fields added non-coherently.

[0101] The single modulation pattern determined in this way does not require partitioning or tiling the surface of the SLM to form sub-modulation patterns corresponding to each image field. Figure 1 shows that because the filtering is in the Fourier plane, the light corresponding to each image field can occur across the surface of the SLM108. The relative position of the portion corresponding to each image field within the Fourier domain determines the modulation pattern formed by the SLM. [Increased effective frame rate through spatial filtering]

[0102] Figure 2 shows an exemplary resolution of a portion of the spatial frequency domain, where the horizontal direction represents the spatial frequency k x The axis is represented, and the vertical direction is the spatial frequency k. y This represents the axis. The spatial frequency domain is sometimes called the Fourier domain or frequency space. The center point 202 represents the zero-order diffraction peak. Higher-order diffraction peaks form the grid of the unit cell in the Fourier domain. The distance 206 between consecutive horizontal (and vertical) diffraction peaks is called the interorder distance 206, and in physical space it is equal to λf / p, where λ is the wavelength of light illuminating the SLM, f is the focal length of the lens, and p is the pixel pitch of the display.

[0103] In this example, two parts of Fourier space, the first part 208 and the second part 210, are targeted by their respective image fields. In this example, the lower left corner of the second part 210 is aligned with the zero-order diffraction peak 202, and the upper right corner of the first part 208 is aligned with the first horizontal and vertical diffraction peaks 204. The first part 208 and the second part 210 have equal areas, do not overlap, and together occupy a (square) space bounded by the unit cell of the Fourier domain. In this example, the first part 208 and the second part 210 form a continuous rectangle, each with a horizontal length equal to the inter-order distance 206 and a height equal to half the inter-order distance 206.

[0104] The SLM may be configured to form a single modulation pattern H corresponding to two image fields H1 and H2. The Fourier transforms of the two image fields, F(H1) and F(H2), are determined such that F(H1) targets the portion of the Fourier domain corresponding to the first portion 208, and F(H2) targets the portion of the Fourier domain corresponding to the second portion 210. F(H1) and F(H2) are inverse Fourier transformed in the viewer's eye to form H1 and H2 corresponding to the first and second image fields. Furthermore, H1 and H2 are added non-coherently so that the viewer receives the two image fields for a single modulation pattern of the SLM.

[0105] In this way, at the cost of halving the resolution (because the amount of transmitted light corresponding to each image is halved), the number of image fields that the display system can display per unit time doubles. This allows for a certain degree of design flexibility, enabling designers to trade off resolution for more image fields per unit time, a possibility that was previously unavailable.

[0106] The properties of the first portion 208 and the second portion 210 depend on the light source(s) used to illuminate the SLM. In the first embodiment, two light sources are used to illuminate the SLM by emitting light at different wavelengths (this avoids coherent interference between the light from the two light sources). The physical spatial filter, positioned in the Fourier plane and corresponding to the resolution 200 in the Fourier domain, may include a first spectral filter region, corresponding to the first portion 208 and positioned to allow the passage of a first subset of the visible electromagnetic spectrum, including the wavelengths of light emitted by the first light source. Similarly, the physical spatial filter may include a second spectral filter region, corresponding to the second portion 210 and positioned to allow the passage of a second subset of the visible electromagnetic spectrum, including the wavelengths of light emitted by the second light source. In this first embodiment, multiple image fields generated by a single modulation pattern of the SLM can be simultaneously transmitted by the spatial filter without the need to switch the aperture over time.

[0107] The first and second image fields may correspond to the respective color channels of a color image. The advantage here is that two color channels can be displayed simultaneously. Further embodiments below describe the simultaneous display of three image fields corresponding to the respective color fields of an RGB color image, but this can be extended to simultaneously display multiple channels of any arbitrary color space.

[0108] A spectral filter allows a specific range of wavelengths to pass through. Spectral filters with defined nominal wavelengths and full width at half maximum (FWHM, a measure of passband) characteristics are commercially available from companies such as Thorlabs. Spectral filters can also be fabricated using colored inks. Additionally, diffraction gratings or holographic optical elements (HOEs) designed to diffract specific wavelengths or wavelength ranges can also function as spectral filters.

[0109] In the second embodiment, a single monochromatic light source may be used to illuminate the SLM. In this second embodiment, in order to prevent coherent interference of the light corresponding to the two image fields, it is necessary to limit the portion of light transmitted at one time by a physical filter corresponding to the resolution 200. As in the first embodiment, the first portion 208 of F(H) in the Fourier domain may correspond to light associated with a first image field that covers a first region of the Fourier plane. Similarly, the second portion 210 of F(H) in the Fourier domain may correspond to light associated with a second image field that covers a second region of the Fourier plane.

[0110] Such a physical space filter may include a first shutter and a second shutter corresponding to portions 208 and 210, respectively. The first and second shutters may be controllable by a controller (not shown) between a substantially transparent state that allows light to pass through and a substantially opaque state that prevents light from passing through. (Other embodiments may use other types of shutters, such as reflective shutters instead of transparent ones.) The first and second shutters may be configured to allow light to pass through only one of the first and second shutters at any given time. Furthermore, the first and second shutters may be configured to allow light to pass through at some point in time within the period during which a single modulation pattern is formed by the SLM. The shutters may be configured to allow light corresponding to the first portion 208 of F(H) to be transmitted for the same amount of time as light corresponding to the second portion 210 of F(H).

[0111] A controllable shutter can be manufactured in various ways. For example, such a shutter can be made from liquid crystals and operate to either substantially allow light to pass through or substantially block light. The liquid crystals can have a high switching speed, such as in a pi cell or a ferroelectric liquid crystal display (FLCD). Other embodiments may use a digital micromirror device (DMD) as a spatial filter, where the DMD is controlled to control which portions of the modulated light are allowed to pass through. Another embodiment may use a rotating chopper wheel, which rotates to define each of a plurality of apertures and a laser synchronized to the chopper wheel. The chopper wheel can use, for example, a stepper motor or the like to control the rotational position. Of course, a controllable shutter can utilize any suitable shutter technology, examples of which include molecule-based shutters, quantum optical shutters, and plasmonic metamaterial shutters.

[0112] FIG. 3 shows another exemplary decomposition 300 of a portion of the spatial frequency domain that can be used with the display system 100 shown in FIG. 1. FIG. 3 shows the position 302 of the zero-order diffraction peak, the first-order horizontal and vertical diffraction peaks 304, and the inter-order distance 306, which are defined in the same manner as described above with respect to FIG. 2. Similar to FIG. 2, FIG. 3 shows the decomposition 300 in the spatial frequency domain, where the horizontal direction represents the spatial frequency k x axis, and the vertical direction represents the spatial frequency k y axis.

[0113] The decomposition 300 defines a first portion 308 of F(H), a second portion 310 of F(H), and a third portion 312 of F(H). Figure 3 shows the decomposition 300 for use with light having first, second, and third wavelengths, which can be produced by first, second, and third light sources, respectively. As described above, each of the multiple image fields displayed by the modulation pattern of the SLM may correspond to light of a specific wavelength, such that light of a first wavelength forms a first image field corresponding to the first portion 308 of F(H) in the Fourier domain, light of a second wavelength forms a second image field corresponding to the second portion 310 of F(H) in the Fourier domain, and light of a third wavelength forms a third image field corresponding to the third portion 312 of F(H) in the Fourier domain.

[0114] In this embodiment, resolution 300 is intended for use with amplitude-modulated SLM. As an amplitude-modulating device, F(H) must not overlap with the Fourier transform of the complex conjugate of H, F(H*), in order to reduce the effects of noise. Thus, the sum of parts 308, 310, and 312 occupies an area equal to half the unit cell of the Fourier domain.

[0115] During operation, the first portion 308 of F(H) corresponds to a first region of the spatial filter substantially positioned in the Fourier plane of the SLM, the second portion 310 of F(H) corresponds to a second region of the spatial filter, and the third portion 312 of F(H) corresponds to a third region of the spatial filter 12. The portion 314 of the resolution 300 corresponds to a cutoff region of the spatial filter that prevents light from passing through. The spatial filter includes a first spectral filter corresponding to the first portion of F(H) that allows transmission of a first wavelength, a second spectral filter corresponding to the second portion of F(H) that allows transmission of a second wavelength, and a third spectral filter corresponding to the third portion of F(H) that allows transmission of a third wavelength. The spectral filters may be the same as those described above with reference to Figure 2 when the spatial filter is configured to filter polychromatic light. In this way, the first, second, and third image fields can be displayed simultaneously in the viewer's pupil without requiring time-series synchronization of the spatial filter's illuminator and / or shutter.

[0116] In the embodiment, the first, second, and third wavelengths correspond to red light, green light, and blue light, respectively. Red light may have wavelengths between 610 nm and 750 nm, such as 635 nm. Blue light may have wavelengths around 400 nm to 495 nm, for example, 450 nm. Green light may have wavelengths in the range of 495 nm to 570 nm or 520 nm to 560 nm, such as approximately 520 nm.

[0117] The second section 310 is larger than the first section 308 and the third section 312. This means that the spatial filter allows more green light to pass through compared to red and blue light. Since the receptors in the eye are most sensitive to green light, and green light has a higher effective resolution than red and blue light, this configuration effectively improves the display quality perceived by the viewer.

[0118] In this embodiment, the second portion 310 is a rectangle with a width equal to 2 / 3 of the interorder distance 306 and a height equal to 1 / 2 of the interorder distance 306. Therefore, the area occupied by the second portion 310 is 1 / 3 of the area of ​​the unit cell of the Fourier domain. The first portion 308 and the third portion 312 are rectangles of equal size with a height equal to 1 / 4 of the interorder distance 306 and a width equal to 1 / 3 of the interorder distance 306. Therefore, the area occupied by the first portion 308 and the third portion 312 is 1 / 12 of the area of ​​the unit cell of the Fourier domain.

[0119] Figure 3 shows the resolution in the Fourier domain. Figure 4 shows an exemplary physical (real-world) spatial filter 400 corresponding to the resolution 300 in Figure 3 in physical space (the Fourier plane of the optical system). Thus, the arrangement of the first region 404, the second region 406, and the third region 408 corresponds to the physical positions of the first portion 308, the second portion 310, and the third portion 312 shown in the frequency domain of Figure 3. The position of the zero-order diffraction peak 402 is shown, and the cutoff region 410 of the spatial filter 400, which always prevents light from passing through, is shown. As shown, in physical space, the blue region 408 partially overlaps with the green region 406 and the red region 404. In the overlap, the spatial filter allows blue light and green light, and blue light and red light, to pass through simultaneously.

[0120] In the example in Figure 4, the light source is positioned such that the zero-order diffraction peaks 402 corresponding to each color are aligned in the Fourier plane. In one embodiment, the light source is provided by a white light emitter with appropriate spectral filtering, either before or after the SLM. In another embodiment, the light source may be provided by a separate emitter having an appropriate wavelength. Wavelength scaling adjusts the relative position and size of the aperture.

[0121] Figure 5 shows a physical space filter 500 having an alternative arrangement of three regions 508, 510, and 512, compared to the arrangement of regions 404, 406, and 408 of the spatial filter 400 shown in Figure 4, and also corresponding to the resolved 300 of Figure 3 in physical space. In this embodiment, the illumination angles of the three light sources incident on the SLM are set such that the green zero-order diffraction peak 502, the red zero-order diffraction peak 504, and the blue zero-order diffraction peak 506 are positioned to result in a nearly aligned result for the regions corresponding to green, red, and blue light, thereby the centers of each aperture 508, 510, and 512 are nearly coincidental. Referring to the display system 100 shown in Figure 1, this can be achieved by adjusting the offset and / or angle of the light sources (in the illumination system 102) in front of the condenser lens 104.

[0122] The spatial filter 500 includes a second region 510 corresponding to a second portion that allows the transmission of green light. The spatial filter 500 further includes a first region 508 corresponding to a first portion that allows the transmission of red light. A third region 512 allows the transmission of blue light. When these regions 510, 508, and 512 overlap, the filter has the total color of the required colors. Thus, in the outer portion of the filter where region 510 does not overlap with any other region, only green light is allowed to pass through, and the physical filter appears green. In the intermediate portion where 510 and 508 overlap each other, the physical filter allows green and red light to pass through but blocks blue light, so the filter appears yellow. Furthermore, in the central portion of the filter where all of the green, red, and blue regions overlap, the filter allows green, red, and blue light to pass through, so the filter appears white or transparent. Thus, the central portion of the spatial filter that appears white can be realized as an aperture without a spectral filter. In other words, the portions corresponding to the overlap of regions 508, 510, and 512 may simply be holes in the spatial filter 500, or transparent or clear portions. As previously stated, the blocking region 514 prevents the passage of light outside the first region, the second region, and the third region.

[0123] Aligning regions 508, 510, and 512 as shown in Figure 5 reduces the area of ​​the Fourier plane occupied by the sum of regions 508, 510, and 512. This can enable more effective eyebox alignment. By aligning the light transmitted through overlapping regions 508, 510, and 512 with the viewer's pupil, the viewer is ensured to receive light of each color. In contrast, aligning the spatial filter 400 shown in Figure 4 so that red, green, and blue light are all received by the viewer's eye can be more difficult. Furthermore, the arrangement of regions 508, 510, and 512 within the spatial filter 500 shown in Figure 5 allows for the use of more of the Fourier plane for other purposes. An example of this will be discussed later with reference to Figure 12.

[0124] Figure 6 shows a further exemplary resolution 600 of a portion of the spatial frequency domain. Resolution 600 defines the zero-order diffraction peak 602, the first horizontal and vertical diffraction peaks 604, and the first portion 608, the second portion 610, and the third portion 612, which are arranged with respect to the interorder distance 606.

[0125] The second portion 610, corresponding to green light, is larger than the first portion 608 and the third portion 612, corresponding to red and blue light, respectively, in order to prioritize the perceptually more important green light, as described above. Furthermore, the first portion 608 is larger than the third portion 612. This allows more red light to pass through than blue light. Since red light is perceptually more important than blue light to the human eye, this configuration of portions within the Fourier domain can improve the image quality of the arrangement in Figure 3 where red and blue light occupy equal areas. As previously mentioned, portion 614 corresponds to a blockage region that prevents light transmission.

[0126] The sum of portions 608, 610, and 612 also occupies an area equal to half the unit cell of the Fourier domain, in order to avoid any overlap between F(H) and the noise component when using amplitude-modulated SLM. In this embodiment, the second portion 610 is a rectangle with a width equal to 3 / 4 of the interorder distance 606 and a height equal to 1 / 2 of the interorder distance 606. Thus, the area occupied by the second portion 610 is 3 / 8 of the area of ​​the unit cell of the Fourier domain. The first portion 608 is a rectangle with a height equal to 3 / 10 of the interorder distance 606 and a width equal to 1 / 4 of the interorder distance 606. Thus, the area occupied by the first portion 608 is 3 / 40 of the area of ​​the unit cell of the Fourier domain. The third portion 612 is a rectangle with a height equal to 1 / 5 of the interorder distance 606 and a width equal to 1 / 4 of the interorder distance 606. Therefore, the area occupied by the third portion 612 is 1 / 20 of the area of ​​the unit cell of the Fourier domain.

[0127] Figure 7 shows a real-world physical space filter 700 corresponding to the resolved 600 shown in Figure 6 in physical space, where the zero-order diffraction peaks 702 for the green light source, 704 for the red light source, and 706 for the blue light source are positioned such that the region corresponding to green 708, the region corresponding to red 710, and the region corresponding to blue 712 are approximately aligned, similar to Figure 5. In the display system 100 shown in Figure 1, this can be achieved by adjusting the position and / or angle of the light sources (of the illumination system 102) in front of the condenser lens 104. In this case as well, the cutoff region 714 of the spatial filter 700 is shown.

[0128] Aligning the green region 708, the red region 710, and the blue region 712 has similar advantages to the spatial filter 500 shown in Figure 5. However, the spatial filter 700 shown in Figure 7 has the further advantage of improving overall image quality because the image field corresponding to red light is displayed at a higher resolution than the image field corresponding to blue light, and red light is perceptually more important to the human eye than blue light.

[0129] As explained above, the maximum dimensions of a portion within the Fourier domain (and the corresponding region within the physical filter for positioning in the Fourier plane of the optical system) are not aligned with either the direction of consecutive horizontal or vertical diffraction orders. “Maximum dimensions” refers to the longest straight line that can fit within that region; for example, in the case of a rectangle or square, this is the diagonal. This may mean that some higher horizontal and vertical spatial frequencies are filtered out. While this is often acceptable, there are some image fields where allowing transmission of higher spatial frequencies can be beneficial. An example of this is the display of text content, typically composed of higher horizontal and vertical spatial frequencies.

[0130] Figure 8 shows an exemplary resolution 800 in the Fourier domain. In this case as well, the resolution 800 defines the zero-order diffraction peak 802, the first horizontal and vertical diffraction peaks 804, and the first portion 808, the second portion 810, and the third portion 812, which are positioned with respect to the interorder distance 806. The resolution 800 can be used to transmit an RGB image field simultaneously in a manner similar to that described above for Figure 3. As in those examples, portion 814 corresponds to a cutoff region that prevents light transmission. This example is also suitable for use with amplitude-modulated SLM so that F(H) does not overlap with its conjugate F(H*).

[0131] Each of the first part 808, the second part 810, and the third part 812 has a shape with maximum dimensions aligned with the directions of consecutive horizontal and vertical diffraction orders in the Fourier plane. In particular, the first part 808 and the third part 812 are squares rotated by 45 degrees so that their diagonals are aligned with the directions of consecutive horizontal and vertical diffraction orders. The second part 810 has an "I" or "H" shape tilted so that the maximum dimensions of its shape are aligned with the directions of consecutive horizontal and vertical diffraction orders. In addition, the sum of the parts forms a square rotated by 45 degrees. Resolution 800 allows higher vertical and horizontal frequencies to be transmitted, which can be beneficial when displaying images composed of higher spatial frequencies, such as text content, as described above.

[0132] Figure 9 shows the physical spatial filter 900 corresponding to the resolved 800 shown in Figure 8. The zero-order diffraction peaks 902 of the green light source, 904 of the red light source, and 906 of the blue light source are positioned such that the region corresponding to green 908, the region corresponding to red 910, and the region corresponding to blue 912 are approximately aligned. As previously mentioned, this can be achieved in the display system 100 shown in Figure 1 by adjusting the position and / or angle of the light source (in the illumination system 102) in front of the condenser lens 104. In this case as well, the cutoff region 914 of the spatial filter 900 is shown.

[0133] Aligning the green region 908, the red region 910, and the blue region 912 has similar advantages to the spatial filters 500 and 700 shown in Figures 5 and 7, respectively, in terms of more effective eyebox alignment and lower Fourier plane occupancy. However, the spatial filter 900 shown in Figure 9 has the further advantage of transmitting higher horizontal and vertical spatial frequencies compared to those filters, making it better for text display.

[0134] Figure 10 is a schematic diagram of an exemplary display system configuration 1000, illustrating how multiple light sources can illuminate an SLM from different angles to achieve spatially separated zero-order diffraction peaks, as shown in Figures 5, 7, and 9. Two light sources are shown for clarity, but the principle described herein applies to any number of light sources. The display system 1000 includes a first light source 1002 and a second light source 1004. The display system 1000 further includes a condenser lens 1006 arranged to produce quasi-collimated light from the first light source 1002 and the second light source 1004 and illuminate the SLM 1008. The SLM 1008 is configured to form a modulation pattern H that generates a light field. The optical system 1010 is arranged to produce the Fourier transform F(H) of the light field generated by the SLM 1008 in the Fourier plane of the SLM 1008. A spatial filter 1016 is located in the Fourier plane.

[0135] The first light source 1002 and the second light source 1004 may be configured to produce light that is at least partially coherent at different or nearly the same wavelengths. The SLM 1008 is configured to form a single modulation pattern that simultaneously represents two image fields. Each of the two image fields corresponds to light emitted by one of the first light source 1002 and the second light source 1004. Therefore, it is important that the first light source 1002 and the second light source 1004 are non-coherent with respect to each other so that coherent interference between the light emitted by the different light sources 1002 and 1004 is avoided. This can be achieved when the light sources emit light at different wavelengths due to differences in spatial and temporal coherence, and when the light sources emit light at nearly the same wavelength but are spatially non-coherent with respect to each other.

[0136] The first light source 1002 and the second light source 1004, the condenser lens 1006, the SLM 1008, and the optical system 1010 are arranged such that the zero-order diffraction peaks 1012 and 1014 of the light emitted by the different light sources 1002 and 1004 are located in spatially distinct regions of the Fourier plane where the spatial filter 1016 is positioned. The positions and / or illumination angles of the first light source 1002 and the second light source 1004 can be adjusted so that the zero-order peak of each light source is located in a desired position in the Fourier plane, as shown in Figures 5, 7, and 9.

[0137] So far, spatial filters featuring partitions of the Fourier domain have been described, and mutual non-coherence is achieved either by using a controllable time-series aperture for a single wavelength or by using spectral filters for multiple wavelengths. The configuration shown in Figure 10 provides a further means of partitioning the Fourier plane in a mutually non-coherent manner using light of a single wavelength. In this example, two light sources 1002 and 1004 may be configured to produce light of approximately the same wavelength in a mutually non-coherent manner.

[0138] Figure 11 shows an exemplary display system, for example, a physical space filter 1100 in the display system 1000 shown in Figure 10. The spatial filter 1100 also corresponds in physical space to the spatial frequency domain resolution 200 in Figure 2. The display system is configured such that the zero-order diffraction peak of light from the first light source 1102 targets a first position in the Fourier plane, and the zero-order diffraction peak of light from the second light source 1104 targets a second position in the Fourier plane, different from the first position. The unit cell of the Fourier domain, defined by consecutive diffraction orders, is the same size for each light source (because each light source emits light of the same wavelength) and is defined by the inter-order distance 1106.

[0139] The SLM is configured to generate a single modulation pattern representing two image fields (as described throughout). In this embodiment, the image fields are separated by a gap in the Fourier plane. The first region 1108 of the spatial filter, corresponding to the first portion 208 of F(H) (corresponding to the first image field), is located in the upper half of the unit cell with respect to the zero-order diffraction peak of light from the first light source 1102, and the second region 1110, corresponding to the second portion 210 of F(H) (corresponding to the second image field), is located in the lower half of the unit cell with respect to the zero-order diffraction peak of light from the second light source 1102. The spatial filter 1100 further includes a cutoff region to prevent light from passing through other regions.

[0140] The shapes of regions 1108 and 1110 correspond to the resolution 200 shown in Figure 2, but it should be understood that this principle applies to any shape. Furthermore, more than two light sources can be used, and the light sources do not need to emit light of nearly the same wavelength. A controllable shutter similar to that discussed with respect to Figure 2 can be used to increase the area of ​​the Fourier plane used to enlarge the eyebox of the display system for the light emitted by each of the light sources. Further techniques for eyebox enlargement are described below. [Enlarge eyebox]

[0141] Increasing the number of image fields that can be displayed per unit of time provides more capacity for expanding the eyebox over time. This offers an opportunity to expand the size of the display system's eyebox by using unused space near the Fourier plane to display different frames of the SLM over time.

[0142] In this example, the spatial filter defines sets of regions, each associated with a switchable shutter, allowing light to pass through a single set of regions at any given time. Each set of regions may have an associated light source (or set of light sources), which may be configured to emit light only when the switchable shutter of the corresponding set of regions is set to allow light to pass through. The switchable shutter may use a technique similar to that described for the controllable shutter in the example of Figure 2. In some examples, the switchable shutter may actually be a controllable shutter, used for both time-series Fourier plane partitioning of a single SLM frame and eyebox expansion using multiple SLM frames.

[0143] An example of eyebox expansion using a time-series controllable shutter is described here with reference to Figure 12. Figure 12 shows an exemplary spatial filter 1200 in physical space, defining a first set of regions 1208 and a second set of regions 1218. Each of the region sets 1208 and 1218 corresponds to the arrangement of regions 508, 510, and 512 in Figure 5. This is for illustrative purposes only. It should be understood that each set of apertures can contain any arrangement of apertures and does not necessarily have to be the same. In some examples, the sets of regions may overlap if the colors are compatible. For example, the green regions 1208 and 1218 corresponding to region 510 in Figure 5 may overlap. In this case, the switchable shutters may overlap accordingly.

[0144] Both the first set of apertures 1208 and the second set of apertures 1218 include spectral filters similar to those described with reference to Figure 5, so that green, red, and blue light are selectively filtered. Six light sources are used to achieve relative objectification of green, red, and blue light for each of the sets of regions 1208 and 1218. For the first set of apertures, the first, second, and third light sources are configured such that the zero-order diffraction peaks 1202 for green light, 1204 for red light, and 1206 for blue light are positioned to produce specific alignments of the apertures corresponding to their respective colors. Similarly, for the second set of apertures, the fourth, fifth, and sixth light sources are configured such that the zero-order diffraction peaks 1212 for green light, 1214 for red light, and 1216 for blue light are positioned to produce specific alignments of the apertures corresponding to their respective colors.

[0145] The first set of regions 1208 and the second set of regions 1218 are surrounded by their respective shutter boundaries 1210 and 1220, and light from outside the sets of regions cannot pass through the blocking portion 1222 of the spatial filter 1200.

[0146] During operation, at a first time, a first controllable shutter associated with the first set of regions 1208 allows light to pass through the first set of regions 1208. At a first time, a second controllable shutter associated with the second set of regions 1218 is in a state where light cannot pass through the second set of regions 1218. At a second time, the first controllable shutter associated with the first set of regions 1208 prevents light from passing through. At a second time, a second controllable shutter associated with the second set of regions 1218 allows light to pass through the second set of regions 1218.

[0147] In the first time period, the SLM is configured to form a first modulation pattern that generates a first light field containing first, second, and third image fields. The first light field is generated by first, second, and third light sources and is targeted such that the portion targeted for Fourier domains corresponds to the first set of regions 1208. In the second time period, the SLM is configured to form a second modulation pattern that generates a first light field containing fourth, fifth, and sixth light fields. The second light field is generated by fourth, fifth, and sixth light sources and is targeted such that the portion targeted for Fourier domains corresponds to the second set of regions 1218.

[0148] It should be understood that this example can be extended to any number of apertures and associated controllable shutters. Furthermore, this technique is not limited to the simultaneous display of multi-color light, but can be used in conjunction with any of the non-coherent partition examples described herein to increase the effective size of the eyebox. [Use of different parts of the spatial frequency domain]

[0149] As described above, the proposed spatial filter uses an area of ​​the spatial frequency domain, such as the Fourier domain, and this is the same for each single modulation pattern formed on the SLM. In other words, all the single modulation patterns and corresponding spatial filters described above target the same portion of the spatial frequency domain each time. However, this disclosure is not limited thereto, and here we describe an example in which different portions of the spatial frequency domain are targeted by different single modulation patterns on the SLM. For example, a first single modulation pattern includes a first set of image fields targeting a first portion of the spatial frequency domain, and a second single modulation pattern includes a second set of image fields targeting a second portion of the spatial frequency domain, which is different from the first portion.

[0150] Referring to Figure 13, two decompositions in the Fourier domain are shown. Both decompositions are similar in configuration to Figure 2 and include the zero-order diffraction peak 1302. Higher-order diffraction peaks, such as the first-order diffraction peak 304, form the grid of the unit cell in the Fourier domain. As in Figure 2, there is an inter-order distance of 1306. As shown, two unit cells are used for the image field of interest. The first set of parts 1308a, 1310a corresponds to parts 208 and 210 in Figure 2. A different unit square is used for the second set of parts 1308b, 1310b, which target different parts of the Fourier domain. Part 1312 is not used and is cut off entirely.

[0151] Each set of parts can be controlled to allow light to pass through or be blocked, for example, by using a liquid crystal shutter or other structures as described above. During use, the SLM forms a first single modulation pattern in two component image fields targeting the first set of parts 1308a, 1310a. Light from the second set of parts 1308b, 1310b is blocked, and light from the first set of parts is allowed to pass through. Next, the SLM forms a second single modulation pattern in two component image fields targeting the second set of parts 1308b, 1310b. Light from the first set of parts 1308a, 1310a is blocked, and light from the second set of parts 1308b, 1310b is allowed to pass through. As described above with respect to Figure 2, the parts within each set may be non-coherent to each other in various ways, for example, by using spatial filters with different wavelengths and spectral filtering, or by time-domain shuttering within each set during the display period of a single modulation pattern.

[0152] The example in Figure 13 allows the same light source to target different parts of the spatial frequency domain, such as expanding the eyebox, while retaining the advantage of increasing the image field per unit time.

[0153] Now moving on to Figures 14 and 15, the principle of Figure 13 is applied to the RGB portions and regions of Figures 3 and 4 above. Figure 14 shows how these portions are targeted in the spatial frequency domain or Fourier domain, and Figure 15 shows the resulting physical spatial filter for placement in the Fourier plane of the optical system, taking wavelength scaling and diffraction effects into account.

[0154] Referring to Figure 14, the Fourier domain has a zero-order diffraction peak 1402, a first-order diffraction peak 1404, and an interorder spacing 1406. Resolution 1400 includes two sets of parts: a first set 1408a, 1410a, 1412a and a second set 1408b, 1410b, 1412b. Within each set, the first parts 1408a, 1408b are for red light, the second parts 1410a, 1410b are for green light, and the third parts 1412a, 1412b are for blue light. The remaining part 1414 is always blocked.

[0155] The corresponding physical filters for placement in the Fourier plane of the optical system are shown in Figure 15. The boundary of the first set is shown at 1501, and the boundary of the second set is shown at 1503. Within each set, the spectral filter regions 1508a, 1510a, 1512a and 1508b, 1510b, 1512b ensure that each wavelength targets the relevant portion of the Fourier plane. Each set also includes shutters or other structures that are controlled to allow or block the passage of light, for example, shutters that extend over the entire area of ​​each set of spectral filter regions indicated by boundaries 1501 and 1503, respectively.

[0156] During use, the SLM forms a first single modulation pattern in three component image fields targeting the first set of portions 1408a, 1410a, and 1412a. The second set of regions 1503 is controlled to block light, and the first set of regions 1501 is controlled to allow light to pass through. Next, the SLM forms a second single modulation pattern in three component image fields targeting the second set of portions 1408b, 1410b, and 1412b. The first set of regions 1501 of the physical space filter 1500 is controlled to block light, and the second set of regions 1503 is controlled to allow light to pass through.

[0157] In this way, the advantage of increasing the number of light fields per unit time can be combined with increased coverage in the spatial frequency domain or the Fourier domain, such as expanding the eyebox, without requiring additional light sources.

[0158] The examples in Figures 13–15 are based on the examples in Figures 2–4, but the principle of expanding coverage of the spatial frequency or Fourier domain through different single modulation patterns targeting different parts of the spatial frequency domain without additional illumination sources can be applied to any of the embodiments described herein. [White image field]

[0159] The filter in the example above considers decomposing an image into red, green, and blue (RGB) image fields. This disclosure is not limited thereto, and here we describe an example that includes a decomposition with a white image field. Including a white image field may improve the image quality of white and gray areas. This is because there is less variation in chromaticity than when white is formed by adding only red, green, and blue fields. Since the human eye is more sensitive to variations in chromaticity than to variations in luminance, reducing variations in chromaticity improves the perceived image quality.

[0160] Figure 16 shows an exemplary resolution of the Fourier domain 1600 into red, green, blue, and white (RGBW) image fields. It has a zero-order diffraction peak 1602, a first-order diffraction peak 1604, and an interorder spacing 1606. The resolution 1600 consists of four parts: the first part 1608 for red light, the second part 1609 for white light, the third part 1610 for green light, and the fourth part 1612 for blue light. The remaining part 1614 is always blocked.

[0161] Figure 17A shows the color portion of the physical filter corresponding to the decomposition in Figure 16. The physical filter is intended to be substantially positioned in the Fourier plane of the optical system. Figure 17B is a diagrammatic representation of the region of the physical filter that allows light to pass through, corresponding to the portion of the Fourier domain.

[0162] Referring to Figure 17B, the red, green, and blue regions of the Fourier domain correspond to the square regions 1708, 1710, and 1712 in Figure 17B. Since the white region of the Fourier domain is for white light, its broadband nature means that diffraction wavelength effects should be considered, and the corresponding region of the physical filter will be larger for longer wavelengths. In this example, the filter is determined by considering the white region to contain red instance 1709a, green instance 1709b, and blue instance 1709c, with each instance being appropriately scaled. In other words, the white region corresponding to the white region of the Fourier domain consists of instances 1709a, 1709b, and 1709c. The largest instance 1709a allows red light corresponding to the white region of the Fourier domain to pass through, the medium-sized instance 1709b allows green light corresponding to the white region of the Fourier domain to pass through, and the smallest instance 1709c allows blue light corresponding to the white region of the Fourier domain to pass through. When these various regions 1708, 1710, 1712 and instances 1709a, 1709b, 1709c overlap, the filter has the sum of the overlapping colors. Thus, the physical filter includes not only the red, green, blue, and white portions, but also the yellow and cyan portions. Referring to Figure 17A, the filter includes the red portion 1701, the green portion 1702, the blue portion 1703, the white portion 1704, the yellow portion 1705, the magenta portion 1706, and the cyan portion 1707.

[0163] The filter in Figure 17A can be fabricated in any suitable way, such as by printing red, green, and blue inks individually or in combination on a slide to define the colored areas. Similarly, cyan, magenta, and yellow inks can be used to block red, green, and blue light, respectively, for subtractive color mixing systems. Dedicated inks for the colors required in each area can also be used. Other methods for fabricating the filter are possible, such as dielectric coating or surface treatment.

[0164] Figure 18 shows another exemplary decomposition of the Fourier domain, this time into red, green, blue, white, and yellow regions. The red, green, and blue regions are the same as in Figure 16, and the yellow region is added by reducing the area of ​​the white region compared to Figure 16. The red, blue, green, and yellow regions all have the same area in the Fourier domain (as shown).

[0165] Similar to the resolution illustrated in Figure 16, the resolution 1800 in Figure 18 shows the zero-order diffraction peak 1802, the first-order diffraction peak 1804, and the inter-order spacing 1806. The resolution 1800 consists of four parts: the first part 1808 for red light, the second part 1809 for white light, the third part 1810 for green light, the fourth part 1812 for blue light, and the fifth part 1813 for yellow light. The remaining part 1814 is always blocked.

[0166] Figure 19A shows the color portions of the physical filters corresponding to the decomposition in Figure 18, and the color portions of the physical filters placed in the Fourier plane of the optical system. Figure 19B is a graphical representation of the region of the physical filter that allows light to pass through, corresponding to the portion of the Fourier domain. The red, green, and blue portions correspond to the square regions 1908, 1910, and 1912 in Figure 17B. In this example, the filter region corresponding to the white portion of the Fourier domain is again determined by considering it to contain instances of red, green, and blue, each instance being appropriately scaled as described above for Figure 17B. Thus, the largest instance 1909a allows red light to pass through, the medium-sized instance 1909b allows green light to pass through, and the smallest instance 1909c allows blue light to pass through. Similarly, in this example, the filter region corresponding to the yellow portion of the Fourier domain is considered to contain red instance 1913a and green instance 1913b, respectively. In a different example, the filter region corresponding to the yellow portion of the Fourier domain may be considered as a single instance and scaled by the dominant yellow wavelength. When these various regions 1908, 1910, 1912 and instances 1909a, 1909b, 1909c, 1913a, 1913b overlap, the filter has the total color of the required colors. Thus, the physical filter includes not only the red, green, blue, white, and yellow portions, but also the cyan and magenta portions. Referring to Figure 19A, the filter includes the red portion 1901, the green portion 1902, the blue portion 1903, the white portion 1904, the yellow portion 1905, the magenta portion 1906, and the cyan portion 1907.

[0167] Unlike the region in Figure 17, if the yellow area corresponds to the need to pass red and green light, then in the filter of Figure 19A, the yellow area may exist due to different base colors. For example, (i) A portion of the filter containing the overlap of the red and green regions (which may appear yellow) must transmit wavelengths corresponding to both the red and green regions, but may completely or partially block wavelengths corresponding to the potentially yellow region. (ii) The portion of the filter that includes the yellow region must transmit the wavelengths corresponding to the yellow portion (but may completely or partially block the wavelengths corresponding to the red and / or green portions).

[0168] When using a spectral filter printed with a CMY printing process, a single Y ink can significantly transmit light corresponding to the red, green, and yellow portions, thereby satisfying both requirements. Other examples also allow for the use of different inks for two different filtering requirements.

[0169] In some cases, spectral filters may be used, printed with inks that have properties matching the filtering requirements of specific parts of a physical slide. In this case, the inks may include (i) a dedicated yellow ink, such as a slide that allows certain yellow wavelengths to pass through; (ii) a specific ink that allows red and green wavelengths to pass through but (possibly) blocks some intermediate yellow wavelengths (which increases the saturation of red and green); and (iii) an ink that allows all red wavelengths and various levels of orange / yellow / green / cyan wavelengths to pass through and improves transmission efficiency, for use in areas corresponding to the wavelength-dependent effect in the white area.

[0170] In the example above, the physical filter is designed by considering several regions, such as the white and yellow regions, as sums of other colors, so that diffraction effects are correctly accounted for. Other examples could utilize different approaches, such as modeling more constituent colors or considering a continuum of colors and their corresponding scaled components for diffraction effects. However, the design process here has been shown to provide a good balance between filter complexity and image quality.

[0171] In the example above, the Fourier domain decomposition is shown to be continuous with the zeroth order. Other examples may have a cutoff region near the zeroth order to block more of the zeroth order.

[0172] Considering the design of the Fourier domain section, the physical filters shown in Figures 17A and 19A are primarily designed for systems displaying red, green, and blue wavelengths. It should be understood that illumination systems containing additional major wavelength peaks or significant bandwidths (e.g., yellow corresponding to wavelengths between green and red) may have additional appropriately scaled components. [Example of operation]

[0173] The theory and overall structure of the display system described herein are explained, and the general operation method is described here. Figure 20 shows a method 2000 for displaying multiple image fields for a single modulation pattern of an SLM. Method 2000 can be performed, for example, by the controller of the display systems 100, 1000 shown in Figures 1 and 10. That is, method 200 provides exemplary procedures for operating the display systems 100, 1000 shown in Figures 1 and 10.

[0174] In step 2002, a first modulation pattern H1 corresponding to the first image field is determined. As described above, the first modulation pattern has a Fourier transform F(H1) that targets a first region of the Fourier plane.

[0175] In 2004, a second modulation pattern H2 corresponding to the second image field is determined. The second modulation pattern has a Fourier transform F(H2) that targets a second region of the Fourier plane.

[0176] In Block 2006, the SLM is configured or controlled to display H1 and H2 simultaneously, for example, by summing H1 and H2.

[0177] In block 2008, the SLM is illuminated by a light source that is at least partially coherent in order to generate a light field that simultaneously represents the first and second image fields.

[0178] In block 2010, the output is filtered by a spatial filter that defines a first aperture corresponding to F(H1) and a second aperture corresponding to F(H2). An exemplary spatial filter for this purpose is described above. [Example of determining image fields for simultaneous display]

[0179] It should be understood that there are various ways in which the image fields for simultaneous display can be determined for use with the above-described apparatus and method. Some of the above examples use color images, and the image fields for simultaneous display may be separate color fields such as red, green, and blue image fields.

[0180] Another example is the use of multiple image fields to reduce image noise by generating multiple image fields that contain the same image information (such as the same scene from the same viewpoint), but where different noise patterns averaged out to the viewer's eye improve image quality.

[0181] If a shutter is provided, image fields may be displayed sequentially for motion smoothing techniques. Multiple image fields may be collected from an image source for direct display if they are generated sequentially at a sufficiently fast rate (computer games can typically generate very high frame rates, and videos may be pre-recorded or rendered at high frame rates). If the source frame rate is lower than the number of image fields displayed per unit time, additional image fields may also be generated through interpolation, prediction, and / or machine learning techniques. [Pupil tracking]

[0182] The above concept has many applications in holographic and non-holographic display systems. One such example is virtual reality (VR) headsets. VR headsets are wearable devices that immerse users in a simulated three-dimensional environment and typically consist of a head-mounted display (HMD) that covers the user's eyes and provides visual stimuli, creating the illusion of being in a virtual world.

[0183] To ensure that content is always displayed in the viewer's pupil, eye-tracking systems combined with eye-box steering mechanisms are commonly used. One reason eye tracking is necessary is that the eye boxes of some holographic light fields are relatively small compared to the average viewer's pupil size. Without eye tracking and eye-box steering, viewers may not be able to see the image at pupil position. The concepts described herein offer a simpler alternative to eye-box steering as described here.

[0184] Figure 21 shows an exemplary VR display system 2100, which includes a combination of a holographic display 2102 and a conventional display 2104. The conventional display 2104 is configured to produce a conventional two-dimensional image and may be, for example, an LCD, LED, or OLED display. A combiner 2106 combines the outputs of the holographic display 2102 and the conventional display 2104 and is positioned to direct them toward a lens 2108 or eyepiece, which focuses the outputs toward the viewer's pupil 2110. The combiner 2106 allows the output of the conventional display 2104 to pass through without significantly affecting the output, while substantially reflecting the output of the holographic display 2102 toward the lens 2108. The combiner 2108 may include a beam splitter such as a semi-transparent mirror, a recessed beam splitter, or a non-replicating waveguide.

[0185] As illustrated, the holographic portion of the displayed image occupies a smaller field of view compared to the output of the conventional display 1704. Therefore, the holographic content is present only in the center of the field of view, while the lower-quality conventional 2D content is present around the periphery of the field of view.

[0186] The pupil tracking system 2112 is configured to determine the position of the pupil 2110. The determined position can be used by the display system 2100 to adjust the position of the eye box of the holographic display to correspond to the pupil 2110, i.e., to be positioned above the pupil 2110. In this way, the viewer receives image content while using the display system 2100, even when the position of the pupil changes.

[0187] This disclosure provides a method for orienting the eyebox of a holographic display 2102 without requiring a mechanically complex steering mechanism. Returning to Figure 10, the spatial separation between the first light source 1002 and the second light source 1004 causes their respective diffraction peaks 1012 and 1014 to be spatially separated in the Fourier plane. This can result in the eyebox occupying different positions in the pupillary plane corresponding to the light from the first light source 1002 and the second light source 1004. Thus, the location where the eyebox is positioned can be controlled using a configuration of the holographic display 2102 similar to that shown in Figure 10. Although Figure 10 has two light sources, increasing the number of light sources makes it possible to cover more positions. This will be explained in more detail with reference to Figures 22 and 23.

[0188] Figure 22 shows an exemplary display system 2200, which includes three illumination systems 2202, 2204, and 2206. The display system 2200 further includes a condenser lens 2208 arranged to produce quasi-collimated light from the first illumination system 2202, the second illumination system 2204, and the third illumination system 2206 to illuminate the SLM 2210. The SLM 2210 is configured to form a modulation pattern H that generates a light field. The optical system 2212 is arranged to generate the Fourier transform F(H) of the light field generated by the SLM 1810 in the Fourier plane of the SLM 2210. A spatial filter 2220 is located in the Fourier plane.

[0189] The first illumination system 2202, the second illumination system 2204, and the third illumination system 2206 are spatially offset from each other. In the plane of Figure 22, the spatial offset is in the vertical direction, but it should also be understood that the spatial offset can be in any direction away from the plane of the figure. In other words, if we define the optical axis as a virtual line passing through at least the condenser lens 2208 and the SLM 2210, the spatial offset of illumination systems 2202, 2204, and 2206 in some embodiments may include being spatially offset in a direction at least perpendicular to the optical axis. By spatially offsetting illumination systems 2202, 2204, and 2206, the light emitted from each illumination system 2202, 2204, and 2206 is incident on the SLM 2210 at different positions and / or angles.

[0190] The first illumination system 2202, the second illumination system 2204, and the third illumination system 2206 may each include one or more light sources. For example, at least one of the first illumination system 2202, the second illumination system 2204, and the third illumination system 2206 may include three light sources, each configured to produce red light, green light, and blue light.

[0191] Unlike the embodiments described above, the SLM2210 does not necessarily have to be configured to form a single modulation pattern that simultaneously represents multiple image fields, although this is certainly possible. Instead, in some embodiments, the SLM2210 may be configured to form a modulation pattern that represents a single image field at any given time.

[0192] The first illumination system 2202, the second illumination system 2204, and the third illumination system 2206, the condenser lens 2208, the SLM 2210, and the optical system 2212 are arranged such that the zero-order diffraction peaks 2214, 2216, and 2218 of the light emitted by the different illumination systems 2202, 2204, and 2206 are located in spatially distinct regions of the Fourier plane where the spatial filter 2220 is located. The positions and / or illumination angles of the first illumination system 2202, the second illumination system 2204, and the third illumination system 2206 can be adjusted so that the zero-order peak of each light source is located at a desired position in the Fourier plane, as shown in Figures 5, 7, and 9. This adjustment of position and / or angle can also be determined based on where each image needs to be formed.

[0193] The display system 2200 includes a further optical system 2222 to generate an inverse Fourier transform of the field in the spatial filter 2220 in a plane 2230 where the viewer's pupil 2232 may be positioned. This configuration yields a first image 2224, a second image 2226, and a third image 2228 at different positions in the plane 2230. The further optical system 2222 may be called an eyepiece or a main lens. The further optical system 2222 may include a conventional lens, a Fresnel lens, a type of hybrid Fresnel lens having a conventional lens profile in the central portion and a Fresnel profile in the outer portion (for example, characterized by a concentric annular cross-section), or a lens having a folded optical path, sometimes called a "pancake" lens.

[0194] The first illumination system 2202, the second illumination system 2204, and the third illumination system 2206 may be switchable individually. For example, they may be controllable to operate in an "on" state where at least partially coherent light is emitted, and an "off" state where no light is emitted. The "on" state may allow the intensity of the illumination system to be changed. During use, one of the illumination systems 2202, 2226, and 2228 may be turned on at any given time such that only one image among images 2224, 2226, and 2228 is generated in the plane 2230. Alternatively, a further filter may exist near the first illumination system 2202, the second illumination system 2204, and the third illumination system 2206, comprising a shutter that selectively allows light from only one of the first illumination system 2202, the second illumination system 2204, and the third illumination system 2206 to pass through at any given time. This transmits the switching capability of the illumination systems to the switching capability of the shutter, which may be faster. In this case as well, the result is that only a single image from images 2224, 2226, and 2228 is generated on plane 2230.

[0195] The spatial filter 2220 includes controllable or switchable first, second, and third shutters. The switchable shutters may utilize techniques similar to those described for the shutters in the embodiments of Figures 2 and 12. Each switchable shutter corresponds to a first illumination system 2202, a second illumination system 2204, and a third illumination system 2206, respectively. In other words, the first switchable shutter may have a shape corresponding to F(H) corresponding to the light emanating from the first illumination system 2202. The second switchable shutter may have a shape corresponding to F(H) corresponding to the light emanating from the second illumination system 2204. The third switchable shutter may have a shape corresponding to F(H) corresponding to the light emanating from the third illumination system 1806.

[0196] The switchable shutters are configured to operate in sync with the "on" states of the first illumination system 2202, the second illumination system 2204, and the third illumination system 2206. Specifically, when the first illumination system is in the "on" state (i.e., when its light is allowed to pass through), the corresponding switchable shutter of the spatial filter 2220 is in a state that allows light to pass through, while all other switchable shutters are in a state that prevents light from passing through. Preventing light from passing through may include processes such as blocking, absorbing, or reflecting light away from the optical path. Thus, as with illumination systems 2202, 2204, and 2206, a single shutter among the shutters may be in a state that allows light to pass through at any given time.

[0197] If the lighting system includes more than one light source, the switchable shutter may include multiple sub-shutters corresponding to portions of F(H) associated with each light source in the lighting system. Furthermore, the sub-shutters may be positioned or configured so that the light corresponding to the first portion of F(H) does not coherently interfere with the light corresponding to the second portion of F(H). If each light source in the lighting system is configured to emit light at different wavelengths, the different sub-shutters may include respective spectral filters that allow light of each wavelength to pass through. In other embodiments, the sub-shutters may be configured to allow light from each of the light sources in a single lighting system to pass through in a time series.

[0198] An eye-tracking system 2234, or pupil-tracking system, is used to determine the position of the viewer's pupil 2232 in the plane 2230 in a manner similar to that described with respect to Figure 21. In one embodiment, one of the first illumination systems 2202, the second illumination system 2204, and the third illumination system 2206, which are positioned closest to the determined pupil position for each of the images 2224, 2226, and 2228, may be selected and activated, and the corresponding shutter of the spatial filter 2220 may be switched to a state that allows light to pass through. The determination of which illumination system produces the image closest to the determined pupil position may be performed by a processing system coupled to or forming part of the display system 2200. The processing system may also be remote from the display system 2200. The processing system may also be configured to control the operation of the illumination systems and / or the spatial filter 2220 in synchronization with the determined pupil position.

[0199] As the viewer's pupils 2232 move, different lighting systems can be activated based on the determined pupil position. Thus, effective eyebox positioning can be achieved.

[0200] In some embodiments, the viewer's pupil may be positioned across or straddling images so that the viewer can see both of the images formed by each illumination system. In these embodiments, once the pupil position is determined, a subset of the first illumination system 2202, the second illumination system 2204, and the third illumination system 2206, fewer than all of them, located near the determined pupil position (and the corresponding switchable shutter), may be activated chronologically at a speed fast enough for the viewer to receive multiple images but perceive a single light field for visual persistence. This may provide a larger effective eye box by rapidly utilizing adjacent or at least nearby images 2224, 2226, and 2228 in succession to give the viewer the perception of a single larger image. As the viewer's pupil 2232 moves, different subsets of the first illumination system 2202, the second illumination system 2204, and the third illumination system 2206 may be activated. Therefore, this display system 2200 provides a simpler alternative to a mechanical system that physically moves the elements of the display system.

[0201] The exemplary display system 2200 shown in Figure 22 includes three lighting systems, but it should be understood that the above description is generalizable to any number of lighting systems, at least two.

[0202] In some embodiments, the display system may include an array of light sources, and each of the lighting systems may form a part of the array of light sources. The array of light sources may be, for example, an LED array. This can be advantageous because the lighting system remains compact, while the addressable eyebox expands over a two-dimensional area.

[0203] To cover a large area within plane 2230 in Figure 22, a sufficient number of illumination systems (e.g., light sources) are required. As more illumination systems are needed, if each illumination system contains one or more light sources, this number may become too costly or occupy too much space. An alternative is to replace the physical light sources within the illumination systems with images of the light sources. Thus, the images of light sources in different illumination systems can be images of the same physical light source (hereinafter referred to as the “master light source”). An exemplary embodiment of this includes a lens array, where each lens in the lens array forms an image of the “master light source” set. Other examples are possible, such as diffractive optical elements and collimators, or image replication combiners. In each of these cases, images of one or more master light sources may form multiple illumination systems.

[0204] Figure 23 shows a further exemplary display system 2300. The display system 2300 includes a set of one or more master light sources 2302 configured to emit at least partially coherent light. The set of one or more master light sources 2302 may include a red light source, a green light source, and a blue light source. An optical system 2304 (e.g., lenses) is arranged to receive light from the set of one or more master light sources 2302 and produce quasi-collimated light that illuminates a lens array 2306. The lens array 2306 may be a microlens array, such as those manufactured by Thorlabs®. The lens array 2306 shown in Figure 19 includes three vertically dispersed lenses, each of which is arranged to produce a corresponding copy of the light that illuminates the lens array 2306.

[0205] The lens array 2306 forms multiple images of one or more sets of master light sources 2302, represented by the external rays in Figure 19. The first image 2306A is shown by a medium dashed line, the second image 2306B by a long dashed line, and the third image 2306C by a short dashed line. Each of the images 2306A, 2306B, and 2306C can be understood as an illumination system as described herein. Thus, the display system 2300 includes three illumination systems 2306A, 2306B, and 2306C formed from the set of master light sources 2302, and each lens of the lens array 2306. The light beams emitted by each of the illumination systems are shown using different line styles for illustrative purposes.

[0206] The display system 2300 further includes a filter 2307, which includes multiple controllable or switchable shutters, which may use techniques similar to those described for shutters in the examples of Figures 2 and 12. Each shutter corresponds to a single light beam. Thus, the filter 2307 determines which of the light beams produced by the lens array 2307 reaches the SLM 2310. In this way, the light source(s) 2302, optical system 2304, lens array 2306, and filter 2307 operate in a similar manner to the multiple physical light sources of the illumination systems 2202, 2204, and 2206 in Figure 22.

[0207] The display system 2300 further includes a condenser lens 2308, an SLM 2310, a first further optical system 2312, a spatial filter 2320, a second further optical system 2322, and an eye-tracking system 2234, which are identical to the condenser lens 2208, SLM 2210, optical system 2212, spatial filter 2220, further optical system 2222, and eye-tracking system 2234 of the display system 2200 shown in Figure 22. The SLM 2310 can form a modulation pattern representing one or more image fields, as described in detail above.

[0208] The eye-tracking system 2334 is used to determine the position of the viewer's pupil 2332 in the plane 2330 in the same manner as described above with respect to Figures 21 and 22. In one embodiment, one of the lenses of the lens array 2306 that is closest to the determined pupil position for each of the images 2324, 2326, and 2328 may be selected and activated by the filter 2307, and the corresponding shutter of the spatial filter 2320 may be switched to allow light to pass through. As the viewer's pupil 2332 moves, different shutters may be switched in filters 2307 and 2320 based on the determined pupil position. Thus, effective eyebox localization can be achieved.

[0209] In some examples, a subset of the light beams emanating from the lens array 2306 may be selected and activated chronologically to create an image in plane 2330, similar to that described above for Figure 22.

[0210] The exemplary display system 2300 shown in Figure 23 includes one or more sets of master light sources 2302 arranged substantially in the same position, and a lens array 2306 including three lenses, although the lens array 2306 may include at least two lenses arranged in any pattern, and it should be understood that the above description is generalized to any number of spatially separated sets of light sources and lens arrays, each having at least two lenses.

[0211] In some examples, the filter 2307 may be placed on either side of the lens array 1906 to block the transmission of a particular light beam.

[0212] In some examples, either filter 2307 or 2320 may be omitted. For example, for spatial separation in the Fourier plane 2320, filter 2307 may be omitted, in which case filter 2320 is effective in allowing only the desired beam to pass to the viewer, filtering out the influence of other beams as described in more detail above. This is because these other beams occupy different positions in the Fourier plane, as mentioned above. If it is only necessary to form a single image on the SLM at any one time, filter 2320 may be omitted, and filter 2307 may operate to allow a single beam to pass through the SLM 2308.

[0213] The above description of VR displays is for illustrative purposes only. It should be understood that the display systems 2200 and 2300 shown in Figures 22 and 23, respectively, can be used with different display architectures. For example, display systems 2200 and 2300 are also suitable for augmented reality (AR) display systems, which can be understood from Figure 21 by omitting the conventional display 2104 so that holographic content is combined with light received from the viewer's environment. Needless to say, other examples are possible.

[0214] In conclusion, an exemplary holographic optical engine 2400, also called a holographic display system, for displaying color holographic content and using the principles of Figures 21, 22, and 23, is described here with reference to Figure 24. The holographic optical engine 2400 includes a set of master light sources 2402, including a first master light source 2404, a second master light source 2406, and a third master light source 2408, each of which may be configured to produce light that is at least partially coherent at its respective wavelength. In one example, the master light sources 2402, 2406, and 2408 may be configured to emit red light, green light, and blue light, respectively. The holographic optical engine 2400 is similar to the display system 2300 shown in Figure 23, in that it includes a first lens 2410, a lens array 2412, a condenser lens 2414, and an SLM 2424. Each lens in the lens array 2412 is positioned to produce an image of the light emitted by each of the master light sources 2404, 2406, and 2408. In this example, the lens array 2412 is shown as having three lenses along a particular axis, thereby producing three images of each of the master light sources 2404, 2406, and 2408 along that axis. Exemplary rays emitted by each of the master light sources 2404, 2406, and 2408 are shown using their respective ray styles and, for illustrative purposes, are shown as passing through the central lens of the lens array 2412, which is producing one image of each of the master light sources 2404, 2406, and 2408.

[0215] Each set of images produced by each lens of the lens array 2412 can be understood as an illumination system as described herein. Further rays are emitted by the second master light source 2406, passing through the upper lens of the lens array 2412 to create a further image of the light source 2406. In practice, it should be understood that rays from master light sources 2404, 2406, and 2408 pass through each lens of the lens array 2412 to create images of master light sources 2404, 2406, and 2408, respectively.

[0216] The condenser lens 2414 and the first further lens 2422 are arranged to produce images in the SLM2424, with each image corresponding to an image produced by the lens array 2412.

[0217] The holographic optical engine 2400 further includes a switchable shutter 2418 and a second additional lens 2420. The switchable shutter 2418 may include a liquid crystal (LC) shutter and a CMYK printed slide. In one example, the printed slide includes a digitally printed transparent film sandwiched between two optical flats, but other forms of printing directly onto glass are also possible. In one embodiment, the LC shutter may be an n-segment (n~15~30) LC shutter.

[0218] The beam splitter 2416 is used to separate the light reflected by the SLM2424 from the light incident on the SLM2424. [Further Features]

[0219] The above embodiments are to be understood as exemplary examples of the present invention. Further embodiments of the present invention are conceivable. For example, the principles described above may be combined with the principles relating to noise reduction through specific shapes of spatial filters described in WO2023 / 002175A1, which are incorporated herein by reference for all purposes.

[0220] When displaying holographic images using the technology of this disclosure, quantization resulting from the encoding scheme for display on an SLM may degrade display quality and introduce crosstalk between regions during display. While any suitable method may be used, an amplitude encoding scheme such as that described in WO2023 / 180693, incorporated herein by reference for all purposes, has been found to work well.

[0221] Furthermore, the techniques described herein decompose or partition the Fourier domain into different regions for different image fields. When determining the holograms corresponding to those regions, “flat phase” or “unit phase” algorithms may work well. These algorithms assign phases according to a flat gradient, creating one or more peaks or spikes in the Fourier domain. Each peak may be aligned with a region for display, helping to avoid crosstalk between regions. “Multi-spike” algorithms, such as those described in UK Patent Application No. 2400478.0, filed January 12, 2024, and incorporated herein by reference for all purposes, may also work well. In these examples, more spikes may be created within larger regions. Other examples may also use random phase algorithms to determine the hologram for display.

[0222] Any feature described in relation to any one embodiment may be used alone or in combination with other features described, or in combination with one or more features of any other embodiment, or in any combination of any other embodiment. Furthermore, the above equivalents and modifications may be adopted without departing from the scope of the invention as defined in the appended claims.

[0223] Examples of implementations are described in the following clauses. [Clause 1] A display system, wherein the display system is A lighting system configured to emit at least partially coherent light, A spatial light modulator SLM, which is illuminated by the aforementioned illumination system and applies a modulation pattern to the illumination light, An optical system that receives the light modulated by the SLM and is arranged to create the Fourier plane of the SLM, A spatial filter substantially arranged in the Fourier plane of the SLM, Equipped with, The SLM is configured to form a single modulation pattern H that simultaneously represents a first image field and a second image field, wherein each of the first image field and the second image field occupies a different portion of the Fourier transform F(H) of H. The display system wherein the spatial filter is configured such that the light corresponding to the first portion of F(H) corresponding to the first image field does not coherently interfere with the light corresponding to the second portion of F(H) corresponding to the second image field. [Clause 2] The aforementioned lighting system includes a first light source and a second light source, The first light source and the second light source are non-coherent with respect to each other. Light passing through the first region defined by the spatial filter, and corresponding to the first portion of F(H), originates from the first light source. The display system according to Clause 1, wherein light passing through a second region defined by the spatial filter and corresponding to the second portion of F(H) originates from the second light source. [Clause 3] The first light source has a first wavelength, and the second light source has a second wavelength different from the first wavelength. The first image field is for display at the first wavelength, and the second image field is for display at the second wavelength. The first region defined by the spatial filter includes a spectral filter that allows the first wavelength to pass through, The display system according to Clause 2, wherein the second region defined by the spatial filter includes a spectral filter that allows the second wavelength to pass through. [Clause 4] The display system according to Clause 3, wherein the area of ​​the second portion of F(H) is greater than the area of ​​the first portion of F(H). [Clause 5] The single modulation pattern occupies a portion of F(H) different from the first and second image fields, and further simultaneously represents a third image field for display at a third wavelength different from the first and second wavelengths. The illumination system includes a third light source having the third wavelength, The display system according to Clause 3 or 4, wherein the spectral filter defines a third region corresponding to a third portion of F(H), and the third region includes a spectral filter that allows the third wavelength to pass through. [Clause 6] The display system according to Clause 5, wherein the area of ​​the second portion of F(H) is greater than the area of ​​the third portion of F(H). [Clause 7] The display system according to Clause 5 or 6, wherein the first wavelength corresponds to red light, the second wavelength corresponds to green light, and the third wavelength corresponds to blue light. [Clause 8] The display system according to Clause 7, wherein the area of ​​the first portion of F(H) is greater than the area of ​​the third portion of F(H). [Clause 9] The display system according to any one of the clauses 5 to 8, wherein the area of ​​the second portion of F(H) is approximately twice the sum of the areas of the first portion of F(H) and the third portion of F(H). [Clause 10] The display system according to any one of the clauses 5 to 8, wherein the area of ​​the second region is greater than the combined area of ​​both the first region and the third region. [Clause 11] The display system according to any one of the clauses 2 to 10, wherein the first light source and the second light source are arranged in the spatial filter such that the first region and the second region overlap. [Article 12] The display system according to Clause 11, wherein the first light source and the second light source are arranged in the spatial filter such that the first region is substantially contained within the second region. [Clause 13] The display system according to any one of the clauses 1 to 12, wherein the spatial filter defines a region having a shape of maximum dimensions aligned with the directions of continuous horizontal and / or vertical diffraction orders of the Fourier plane. [Clause 14] The aforementioned spatial filter is A first shutter and a second shutter that can be switched between a state that allows light to pass through and a state that blocks light, wherein the first shutter corresponds to a first part of F(H), and the second shutter corresponds to a second part of F(H), and when in use, The state in which one of the first shutter and the second shutter is in which light can pass through at any given time, The display system according to Clause 1, comprising a first shutter and a second shutter, both configured such that the first shutter and the second shutter are in the state that allows light to pass through during each period within the period in which the SLM is forming the single modulation pattern. [Article 15] The single modulation pattern H is a first modulation pattern generated in a first time, The SLM is configured to form a second single modulation pattern H' at a second time different from the first time, the second single modulation pattern simultaneously representing a first further image field and a second further image field, each of which occupies a different portion of the Fourier transform F(H') of H'. The spatial filter is configured to allow at least a first portion of F(H) to pass through during the first time period, and to block F(H') by the spectral filter. The display system according to any one of the clauses 1 to 14, wherein the spatial filter is further configured to allow, at the second time, F(H) to be blocked and at least a first portion of F(H') corresponding to the further first image field to pass through. [Clause 16] The lighting system is a first lighting system, and the display system is The system further comprises a second lighting system configured to emit at least partially coherent light, which is spatially offset from the first lighting system. The single modulation pattern H is a first modulation pattern generated in a first time, The SLM is configured to form a second single modulation pattern H' at a second time different from the first time, the second single modulation pattern simultaneously representing a first further image field and a second further image field, each of which occupies a different portion of the Fourier transform F(H') of H'. The aforementioned spatial filter is During the first time, it is permitted that at least a portion of the light from the first lighting system may pass through, and that the light from the second lighting system may not pass through. A display system according to any one of the clauses 1 to 14, configured such that, during the second time, at least a portion of the light from the second lighting system is allowed to pass through, but the light from the first lighting system is not allowed to pass through. [Article 17] A pupil tracking system configured to determine the position of the viewer's pupils, A processing system, Determine which of the first and second lighting systems corresponds to the position of the viewer's pupil, The display system according to Clause 16, comprising: a processing system configured to control the first illumination system and the second illumination system based on the determined position of the pupil. [Clause 18] Further comprising one or more master light sources, The first illumination system includes a first image of one or more master light sources. The display system according to clause 16 or 17, wherein the second lighting system includes a second image of the one or more master light sources. [Article 19] With an additional lens array, The first image is formed by the first lens of the lens array, The display system according to Clause 18, wherein the second image is formed by the second lens of the lens array. [Clause 20] The display system according to Clause 19, further comprising a further spatial filter positioned after the lens array to control whether the first illumination system or the second illumination system illuminates the SLM. [Article 21] A spatial filter for substantially positioning in the Fourier plane of a spatial light modulator in a display system, wherein the spatial filter is A first region that allows a first subset of the visible electromagnetic spectrum to pass through, A second region is defined that allows a second subset of the visible electromagnetic spectrum to pass through, The spatial filter wherein the first subset of the visible electromagnetic spectrum differs from the second subset of the visible electromagnetic spectrum, and the first region and the second region overlap at least partially. [Article 22] A third region is defined that allows transmission of a third subset of the visible electromagnetic spectrum, which is different from the first and second subsets of the visible electromagnetic spectrum, to pass through. The first subset of the visible electromagnetic spectrum includes red light, the second subset of the visible electromagnetic spectrum includes green light, and the third subset of the visible electromagnetic spectrum includes blue light. The spatial filter according to Clause 21, wherein the area of ​​the second region is greater than the combined area of ​​the first region and the third portion. [Article 23] The spatial filter according to Clause 22, wherein the area of ​​the first region is greater than the area of ​​the third region. [Article 24] A display system including a spatial filter as described in any of clauses 21 to 23. [Article 25] A head-mounted display or head-up display comprising a display system as described in any of clauses 1-20 and 24. [Article 26] A method, wherein the said method is Determine the first modulation pattern H1 corresponding to the first image field, To determine the second modulation pattern H2 corresponding to the second image field, To display H1 and H2 simultaneously on the SLM using a single modulation pattern, To produce a modulated output, the SLM is illuminated with at least a partially coherent light source, This includes filtering the modulated output using a spatial filter, The aforementioned spatial filter is The SLM is substantially arranged in the Fourier plane, We define a first region corresponding to the Fourier transform F(H1) of H1, We define a second region corresponding to the Fourier transform F(H2) of H2, The method is configured such that the light corresponding to F(H1) does not interfere coherently with the light corresponding to F(H2). [Article 27] The first image field corresponds to the first portion of the visible electromagnetic spectrum, The second image field corresponds to the second portion of the visible electromagnetic spectrum, The method according to Clause 26, wherein the first portion of the visible electromagnetic spectrum is different from the second portion of the visible electromagnetic spectrum. [Article 28] The light that is allowed to pass through the first region originates from a first at least partially coherent light source, and the light that is allowed to pass through the second region originates from a second at least partially coherent light source. The first light source described above, which is at least partially coherent, and the second light source described above, which is at least partially coherent, are non-coherent to each other. The method according to clause 26 or 27, wherein the first at least partially coherent light source and the second at least partially coherent light source are arranged such that the first region and the second region at least partially overlap in the Fourier plane. [Article 29] H1 and H2 are displayed in the first time, and the first illumination system, which includes the at least partially coherent light source, illuminates the SLM in the first time, and the method is To determine the third modulation pattern H3 corresponding to the third image field, Determine the fourth modulation pattern H4 corresponding to the fourth image field, At a second time different from the first time, H3 and H4 are simultaneously displayed on the SLM by a further single modulation pattern, Illuminating the SLM with a second illumination system comprising the second at least partially coherent light source, wherein the second illumination system is spatially offset from the first illumination system, further comprising: The aforementioned spatial filter is During the first time period, the light corresponding to H1 and H2 is allowed to pass through, but the light corresponding to H3 and H4 is not allowed to pass through, The method according to any one of the clauses 26 to 28, further configured such that, during the second time, light corresponding to H3 and H4 is allowed to pass through, but light corresponding to H1 and H2 is not allowed to pass through. [Clause 30] Determining the position of the viewer's pupils, The method according to clause 29, further comprising controlling the first illumination system and the second illumination system based on the determined position of the pupil. [Clause 31] A display system comprising: A first illumination system configured to generate a first set of beams of at least partially coherent light; A second illumination system configured to generate a second set of beams of at least partially coherent light and spatially offset from the first illumination system; A spatial light modulator (SLM) arranged to be illuminated by the first set of beams of light and the second set of beams of light, wherein each of the first set of beams of light and the second set of beams of light is incident on the SLM at a different angle; An output optical system arranged to receive the light modulated by the SLM; A pupil tracking system configured to determine the position of a viewer's pupil; A processing system comprising: Determining at least one active beam of the first set of beams and the second set of beams corresponding to the determined position of the viewer's pupil; The processing system configured to control the first illumination system and the second illumination system such that the at least one active beam is used to illuminate the SLM. [Clause 32] The display system according to clause 31, wherein the first illumination system includes a first set of light sources and the second illumination system includes a second set of light sources. [Clause 33] Comprising a light emitting diode (LED) array, The first illumination system includes a first portion of the LED array, The display system according to clause 31 or 32, wherein the second illumination system includes a second portion of the LED array. [Clause 34] Further comprising one or more master light sources, The set of the first light sources is one or more first images of the one or more master light sources, The display system according to clause 32, wherein the set of the second light sources is one or more second images of the one or more master light sources. [Clause 35] Further comprising a lens array, The one or more first images are formed by the first lenses of the lens array, The display system according to clause 34, wherein the one or more second images are formed by the second lenses of the lens array. [Clause 36] The display system according to clause 35, comprising a spatial filter arranged behind the lens array for controlling which of the first illumination system and the second illumination system illuminates the SLM.

Claims

1. A display system, wherein the display system is A lighting system configured to emit at least partially coherent light, A spatial light modulator SLM illuminated by the illumination system and for applying a modulation pattern to the illumination light, wherein the SLM is configured to form a single modulation pattern H that simultaneously represents multiple image fields, and the information associated with each of the multiple image fields occupies a different portion of the Fourier transform F(H) of H, An optical system is provided to receive the light modulated by the SLM and to create a Fourier plane for the SLM. A spatial filter substantially arranged in the Fourier plane of the SLM, wherein the spatial filter comprises a plurality of regions, each region corresponding to a portion of F(H) representing an image field, and each region is configured to allow light related to the image field corresponding to the region to pass through; Equipped with, A display system in which, in the aforementioned single modulation pattern, the information related to the image field having the greatest perceptual significance to the viewer occupies the largest portion of F(H).

2. The display system according to claim 1, wherein each image field is a color channel of an image.

3. The display system according to claim 1 or 2, wherein the plurality of image fields include at least three image fields.

4. The plurality of image fields include a red image field, a green image field, and a blue image field. The display system according to any one of claims 1 to 3, wherein the information related to the green image field occupies the largest portion of F(H).

5. The aforementioned plurality of image fields include a substantially white light field, The display system according to any one of claims 1 to 3, wherein the substantially white light field occupies the largest portion of F(H).

6. The display system according to claim 5, wherein the plurality of image fields further include a red image field, a green image field, and a blue image field.

7. The display system according to claim 6, wherein the information related to the red image field, the information related to the green image field, and the information related to the blue image field occupy portions of F(H) of the same size.

8. The display system according to any one of claims 3 to 7, wherein the plurality of image fields further include a yellow image field.

9. The display system according to any one of claims 3 to 8, wherein the plurality of image fields further include a cyan image field.

10. A display system, wherein the display system is A lighting system configured to emit at least partially coherent light, A spatial light modulator (SLM) for applying a modulation pattern to the illumination light, which is illuminated by the aforementioned illumination system, An optical system is provided to receive the light modulated by the SLM and to create a Fourier plane for the SLM. A spatial filter substantially arranged in the Fourier plane of the SLM, Equipped with, The SLM is configured to form a single modulation pattern H that simultaneously represents at least a first image field occupying a first portion of the Fourier transform F(H) of a single modulation pattern H, and a second image field occupying a different second portion of F(H). A display system in which the spatial filter is configured such that the light corresponding to the first portion of F(H) does not coherently interfere with the light corresponding to the second portion of F(H), or partially coherently interferes with it.

11. The display system according to claim 10, wherein the second portion occupies a larger area F(H) than the first portion.

12. The display system according to claim 10 or 11, wherein the second image field is perceptually more important to the viewer than the first image field.

13. The display system according to any one of claims 10 to 12, wherein at least one of the first image field and the second image field corresponds to a white image field.

14. The single modulation pattern further simultaneously represents a third image field that occupies a third portion of F(H) that is different from the first and second portions, The display system according to any one of claims 10 to 13, wherein the spatial filter is further configured to filter light corresponding to at least the third portion.

15. The single modulation pattern further simultaneously represents a fourth image field that occupies a fourth portion of F(H) that is different from the first portion, the second portion, and the third portion. The spatial filter is further configured to filter out light corresponding to at least the fourth portion, The display system according to claim 14, wherein each of the first image field, the second image field, the third image field, and the fourth image field corresponds to a different color.

16. The display system according to claim 15, wherein one of the first image field, the second image field, the third image field, and the fourth image field corresponds to a white image field.

17. The display system according to any one of claims 14 to 16, wherein the second portion occupies a larger area F(H) than the third portion.

18. The display system according to any one of claims 14 to 17, wherein the first portion corresponds to a red image field, the second portion corresponds to a green image field, and the third portion corresponds to a blue image field.

19. The display system according to claim 18, wherein the first portion occupies an area F(H) larger than the third portion.

20. The second portion corresponds to a white image field, and is the display system according to any one of claims 10 to 17.

21. The display system according to any one of claims 14 to 20, wherein the area of ​​the second portion of F(H) is approximately twice the sum of the areas of the first portion of F(H) and the third portion of F(H).

22. The display system according to any one of claims 14 to 21, wherein the area of ​​the second region is greater than the combined area of ​​both the first region and the third region.

23. The display system according to any one of claims 10 to 22, wherein in the spatial filter, a first region corresponding to a first portion of F(H) and a second region corresponding to a second portion of F(H) overlap.

24. The display system according to claim 23, wherein the lighting system includes a first light source and a second light source, arranged in the spatial filter such that the first region substantially includes the second region.

25. The display system according to any one of claims 10 to 24, wherein the spatial filter defines a region having a shape of maximum dimensions aligned with the directions of continuous horizontal and / or vertical diffraction orders of the Fourier plane.

26. The display system according to any one of claims 10 to 25, wherein the spatial filter includes a spectral filter.

27. A display system, wherein the display system is A lighting system configured to emit at least partially coherent light, A spatial light modulator (SLM) for applying a modulation pattern to the illumination light, which is illuminated by the aforementioned illumination system, An optical system is provided to receive the light modulated by the SLM and to create a Fourier plane for the SLM. A spatial filter substantially arranged in the Fourier plane of the SLM, Equipped with, The SLM is configured to form a single modulation pattern H that simultaneously represents at least a first image field occupying a first portion of the Fourier transform F(H) of H and a second image field occupying a different second portion of F(H), The aforementioned spatial filter is A first shutter and a second shutter that can be switched between a state that allows light to pass through and a state that blocks light, wherein the first shutter corresponds to a first portion of F(H), and the second shutter corresponds to a second portion of F(H), and when in use, The state in which one of the first shutter and the second shutter is in which light can pass through at any given time, A display system comprising a first shutter and a second shutter, both configured such that the first shutter and the second shutter are in the state that allows light to pass through during each period within the period in which the SLM forms the single modulation pattern.

28. The single modulation pattern H is a first modulation pattern generated in a first time, The SLM is configured to form a second single modulation pattern H' at a second time different from the first time, the second single modulation pattern simultaneously representing a first further image field and a second further image field, each of which occupies a different portion of the Fourier transform F(H') of H'. The spatial filter is configured to allow at least a first portion of F(H) to pass through during the first time period. The display system according to any one of claims 1 to 27, wherein the spatial filter is further configured to allow at least a first portion of F(H') corresponding to the first further image field to pass through at the second time.

29. The display system according to claim 28, wherein the spatial filter is further configured such that F(H') is blocked by the spatial filter at the first time and F(H) is blocked by the spatial filter at the second time.

30. The lighting system is a first lighting system, and the display system is The present invention further comprises a second lighting system configured to emit at least partially coherent light, which is spatially offset from the first lighting system. The single modulation pattern H is a first modulation pattern generated in a first time, The SLM is configured to form a second single modulation pattern H' at a second time different from the first time, the second single modulation pattern simultaneously representing a first further image field and a second further image field, each of which occupies a different portion of the Fourier transform F(H') of H'. The aforementioned spatial filter is During the first time period, at least a portion of the light from the first lighting system is allowed to pass through. The display system according to any one of claims 1 to 29, configured to allow at least a portion of the light from the second lighting system to pass through during the second time.

31. The display system according to claim 30, wherein the spatial filter is further configured such that light from the second lighting system is not allowed to pass through during the first time period, and so that light from the first lighting system is not allowed to pass through during the second time period.

32. A pupil tracking system configured to determine the position of the viewer's pupils, A processing system, Determine which of the first and second lighting systems corresponds to the position of the viewer's pupil, A processing system configured to control the first and second illumination systems based on the determined pupil position, The display system according to claim 30 or 31, comprising:

33. The system further comprises one or more master light sources, The first illumination system includes a first image of one or more master light sources. The display system according to any one of claims 30 to 32, wherein the second lighting system includes a second image of the one or more master light sources.

34. With an additional lens array, The first image is formed by the first lens of the lens array, The display system according to claim 33, wherein the second image is formed by the second lens of the lens array.

35. The display system according to claim 34, further comprising a further spatial filter positioned after the lens array to control whether the first illumination system or the second illumination system illuminates the SLM.

36. A head-mounted display or head-up display comprising the display system described in any one of claims 1 to 35.

37. It is a method, A first modulation pattern H corresponding to the first image field １ The decision is to determine H １ The Fourier transform F(H) １ ) occupies the first part of the Fourier domain, and to determine, Second modulation pattern H corresponding to the second image field ２ The decision is to determine H ２ The Fourier transform F(H) ２ ) occupies a second part of the Fourier domain that is different from the first part described above, A single modulation pattern over the SLM １ and H ２ Displaying them simultaneously, To produce a modulated output, the SLM is illuminated with at least partially coherent light, Substantially disposed on the Fourier plane of the SLM, light corresponding to F(H １ ) does not interfere coherently with light corresponding to F(H ２ ), or filtering the modulated output using a spatial filter configured to interfere partially coherently, Methods that include...

38. The method according to claim 37, wherein the second portion is larger than the first portion.

39. The first image field corresponds to a first subset of the visible electromagnetic spectrum, The second image field corresponds to a second subset of the visible electromagnetic spectrum, The method according to claim 37 or 38, wherein the first subset of the visible electromagnetic spectrum is different from the second subset of the visible electromagnetic spectrum.

40. The method according to any one of claims 37 to 39, wherein the spatial filter includes a first region corresponding to the first portion of F(H) and a second region corresponding to the second portion of F(H), and the first region and the second region at least partially overlap.

41. The light that is allowed to pass through the first region originates from a first at least partially coherent light source, and the light that is allowed to pass through the second region originates from a second at least partially coherent light source. The first light source that is at least partially coherent and the second light source that is at least partially coherent are non-coherent to each other. The method according to claim 40, wherein the first at least partially coherent light source and the second at least partially coherent light source are arranged such that the first region and the second region at least partially overlap in the Fourier plane.

42. H １ and H ２ The first illumination system, which includes the at least partially coherent light source, illuminates the SLM during the first time, and the method is Third modulation pattern H corresponding to the third image field ３ To decide, The fourth modulation pattern H corresponding to the fourth image field ４ To decide, At a second time different from the first time, a further single modulation pattern is applied to the SLM by H ３ and H ４ Displaying them simultaneously, Illuminating the SLM with a second illumination system comprising a second, at least partially, coherent light source, wherein the second illumination system is spatially offset from the first illumination system. It further includes, The aforementioned spatial filter is At the first time, H １ and H ２ This allows light corresponding to the light to pass through. At the second time mentioned above, H ３ and H ４ The method according to any one of claims 37 to 41, further configured to allow light corresponding to pass through.

43. The spatial filter, at the first time, H ３ and H ４ The light corresponding to is not allowed to pass through, and at the second time, H １ and H ２ The method according to claim 42, further configured so as not to allow light corresponding to the torrent to pass through.

44. Determining the position of the viewer's pupils, The method according to claim 42 or 43, further comprising controlling the first illumination system and the second illumination system based on the determined position of the pupil.

45. It is a display system, A first illumination system configured to generate a first set of at least partially coherent beams of light, A second illumination system, configured to generate a second set of at least partially coherent beams of light, and spatially offset from the first illumination system, A spatial light modulator SLM arranged to be illuminated by a first set of light beams and a second set of light beams, wherein each of the first set of light beams and the second set of light beams is incident on the SLM at different angles, An output optical system arranged to receive light modulated by the SLM, A pupil tracking system configured to determine the position of the viewer's pupils, A processing system, Determine at least one active beam from the first set of beams and the second set of beams that corresponds to the determined pupil position of the viewer, The processing system is configured to control the first illumination system and the second illumination system so that at least one active beam is used to illuminate the SLM, A display system equipped with the following features.

46. The display system according to claim 44, wherein the first lighting system includes a set of first light sources, and the second lighting system includes a set of second light sources.

47. Equipped with a light-emitting diode (LED) array, The first lighting system includes a first portion of the LED array, The display system according to claim 44 or 45, wherein the second lighting system includes a second portion of the LED array.

48. The system further comprises one or more master light sources, The first set of light sources is one or more first images of one or more master light sources, The display system according to claim 45, wherein the set of second light sources is one or more second images of the one or more master light sources.

49. With an additional lens array, The one or more first images are formed by the first lens of the lens array. The display system according to claim 47, wherein the one or more second images are formed by the second lens of the lens array.

50. The display system according to claim 48, further comprising a spatial filter positioned after the lens array for controlling whether the first illumination system or the second illumination system illuminates the SLM.

Images