Display system and light control element thereof

Abstract

Display systems and waveguide pupil extenders are described. A display system includes an optical component having first and second major surfaces and one or more sub-surfaces, each sub-surface defining an edge face of the optical component. One or more of the first and second major surfaces of the optical component are reflective. The light control layer is disposed on the first major surface of the optical member. The light control layer includes a louver structure including a louver array arranged to suppress reflection of sunlight received on an optical path to the first major surface. At least one edge face of the optical component is arranged to suppress specular reflection of light incident thereon. In an embodiment, the optical component is a waveguide pupil expander.

Description

Technical Field

[0001] The present disclosure relates to display systems. More specifically, the present disclosure relates to display systems including waveguide pupil expanders, and to pupil expansion methods using waveguides. The present disclosure also relates to suppressing reflections of sunlight and other stray light associated with optical components of a display system. In some embodiments, the optical components include a waveguide pupil expander including a light control element. Some embodiments relate to a picture generation unit and a head-up display, such as an automotive head-up display (HUD). Background Art

[0002] Light scattered from an object contains both amplitude and phase information. This amplitude and phase information can be captured, for example, on a photographic plate by well-known interference techniques to form a holographic recording or "hologram" comprising interference fringes. The hologram can be reconstructed by illumination with appropriate light to form a two-dimensional or three-dimensional holographic reconstruction or replay image representing the original object.

[0003] Computer generated holography can numerically simulate interference processes. Computer generated holograms can be calculated by techniques based on mathematical transformations such as Fresnel or Fourier transforms. These types of holograms may be referred to as Fresnel / Fourier transform holograms or simply Fresnel / Fourier holograms. Fourier holograms may be considered as Fourier domain / plane representations of objects or frequency domain / plane representations of objects. Computer generated holograms may also be calculated, for example, by coherent ray tracing or point cloud techniques.

[0004] The computer generated hologram may be encoded on a spatial light modulator arranged to modulate the amplitude and / or phase of the incident light. For example, the light modulation may be achieved using electrically addressable liquid crystals, optically addressable liquid crystals or micromirrors.

[0005] A spatial light modulator typically includes a plurality of individually addressable pixels, which may also be referred to as cells or elements. The light modulation scheme may be binary, multi-level, or continuous. Alternatively, the device may be continuous (i.e., not including pixels), and thus the light modulation may be continuous across the device. A spatial light modulator may be reflective, meaning that the light is modulated to be output in reflection. A spatial light modulator may also be transmissive, meaning that the light is modulated to be output in transmission.

[0006] Using the system described here, a holographic projector can be provided. Such projectors are already used in head-up displays "HUD". Summary of the invention

[0007] Various aspects of the disclosure are defined in the accompanying independent claims.

[0008] A display system is provided, comprising an optical component having first and second major surfaces and one or more minor surfaces. It can be said that each minor surface forms an edge or edge face of the optical component. One or more of the first and second major surfaces are reflective. A light control layer is disposed on the first major surface of the optical component. The light control layer comprises a louver structure. The louver structure comprises an array of louvers arranged to suppress reflection of sunlight received on a light path to the first major surface. At least one edge / edge face of the optical component is arranged to suppress specular reflection of light incident thereon.

[0009] In some embodiments, at least one edge face of the optical component is arranged to attenuate and / or diffusely reflect / scatter light incident thereon. For example, at least one edge face may include a material, element or component that attenuates and / or diffusely reflects or scatters light. Therefore, light directly or indirectly incident on at least one edge face is diffusely reflected / scattered and / or attenuated, thereby suppressing the reflection of light. The technician will understand that the surface of diffusely reflected / scattered light also attenuates light. However, other technologies for attenuating incident light are also possible and expected.

[0010] In other embodiments, at least one edge face of the optical component is arranged to absorb light incident thereon. For example, at least one edge face of the optical component may include a light absorbing material or include a light absorbing element or component. In an example, at least one edge face is coated with a light absorbing coating, such as a black coating. Therefore, light directly or indirectly incident on at least one edge face is absorbed, thereby suppressing reflection of light.

[0011] In examples, at least one edge face of the optical component is coated with a light attenuating coating, such as an opaque coating, or at least one edge of the optical component is processed, such as by etching, to attenuate and / or diffusely reflect / scatter light incident thereon.

[0012] In other examples, at least one edge face of the optical component includes a boundary, wherein the boundary is arranged to diffusely reflect / scatter and / or attenuate light incident thereon. For example, the boundary may include a sheet having diffuse light reflection / scattering properties, or may include a sheet having a coating or film having diffuse light reflection / scattering properties.

[0013] In some embodiments, the first major surface of the optical component includes an exit surface for outputting image light of the display system to an observation area. The optical component may include a light redirecting element for controlling the direction of the output image light from the exit surface. In some embodiments, the light redirecting element includes a first major surface and one or more sub-surfaces, each sub-surface defining an edge surface thereof. The first major surface of the light redirecting element may form an interface with the exit surface of the optical component. At least one edge surface of the light redirecting element may be arranged to suppress specular reflection of light incident thereon. In some examples, the light redirecting element is a light redirecting film, such as a film including a prism array having an inclined surface opposite to the first major surface. In some embodiments, at least one edge of the light redirecting element is arranged to absorb light incident thereon or to attenuate or diffusely reflect / scatter light.

[0014] In some embodiments, the display system includes an opaque border or frame around one or more sub-surfaces forming an edge face of the optical component. The opaque border or frame is also used to suppress specular reflection of light, such as by blocking, attenuating and / or diffusely reflecting / scattering light directly incident on the edge face of the optical component.

[0015] In an embodiment of the display system, the optical component comprises a waveguide pupil expander. In an example, the first and second major surfaces are opposing / parallel reflective surfaces arranged to provide internal reflection and waveguiding of image light therebetween. For example, the first major surface comprises a partially reflective-partially transmissive surface forming an exit surface of the waveguide pupil expander. In an example, at least one edge face arranged to suppress specular reflection of light incident thereon comprises an edge face at a first end of the waveguide pupil expander, wherein the pupil expansion is from the first end to the second end of the waveguide pupil expander.

[0016] A waveguide pupil expander for a display system is also provided.

[0017] In an embodiment, the optical component is a waveguide pupil expander. The light control layer is disposed on an exit surface of the waveguide pupil expander, which forms an output port for image light from a display system toward its viewing area. For example, the waveguide pupil expander may include a pair of parallel reflective surfaces arranged for internal reflection and waveguiding of image light for the display system. The pair of parallel reflective surfaces includes a first total reflection surface and a second partially reflective-partially transmissive surface forming an exit surface. The exit surface may be a planar surface, a reflective surface of the optical component, or both.

[0018] In the present disclosure, the term "replica" is used only to reflect that the spatially modulated light is split so that the composite light field is directed along multiple different optical paths. The word "replica" is used to refer to each occurrence or instance of the composite light field after a replication event - such as a partial reflection-transmission of a pupil expander. Each replica propagates along a different optical path. Some embodiments of the present disclosure relate to the propagation of light encoded with a hologram rather than an image - that is, light that is spatially modulated with a hologram of an image rather than the image itself. Therefore, it can be said that multiple replicas of the hologram are formed. Those skilled in the art of holography will understand that the composite light field associated with the propagation of light encoded with a hologram will vary with the propagation distance. The term "replica" as used herein is independent of the propagation distance, so two light branches or paths associated with a replication event are still referred to as "replicas" of each other, even if the branches have different lengths, so that the composite light field evolves differently along each path. That is, according to the present disclosure, even if two composite light fields are associated with different propagation distances, they are still considered "replicas" - assuming that they originate from the same replication event or series of replication events.

[0019] According to the present disclosure, a "diffraction light field" is a light field formed by diffraction. A diffraction light field can be formed by illuminating a corresponding diffraction pattern. According to the present disclosure, an example of a diffraction pattern is a hologram, and an example of a diffraction light field is a holographic light field or a light field of a holographic reconstruction that forms an image. The holographic light field forms a (holographic) reconstruction of an image on a playback plane. The holographic light field propagated from the hologram to the reproduction plane can be said to include light encoded with the hologram or light in the holographic domain. The diffraction light field is characterized by a diffraction angle determined by the minimum characteristic size of the diffraction structure and the wavelength of the light (of the diffraction light field). According to the present disclosure, it can also be said that the "diffraction light field" is a reconstructed light field formed on a plane spatially separated from the corresponding diffraction structure. An optical system for propagating a diffraction light field from a diffraction structure to an observer is disclosed herein. The diffraction light field can form an image.

[0020] The term "hologram" is used to refer to a record containing amplitude information or phase information or some combination thereof about an object. The term "holographic reconstruction" is used to refer to the optical reconstruction of an object formed by illuminating a hologram. The system disclosed herein is described as a "holographic projector" because the holographic reconstruction is a real image and is spatially separated from the hologram. The term "replay field" is used to refer to the 2D area in which the holographic reconstruction is formed and is fully focused. If the hologram is displayed on a spatial light modulator including pixels, the replay field will be repeated in the form of multiple diffraction orders, each of which is a replica of the zero-order replay field. The zero-order replay field usually corresponds to the preferred or main replay field because it is the brightest replay field. Unless otherwise explicitly stated, the term "replay field" should be considered to refer to the zero-order replay field. The term "replay plane" is used to refer to a plane in space that contains all replay fields. The terms "image", "replay image" and "image area" refer to the area of ​​the replay field illuminated by the light of the holographic reconstruction. In some embodiments, an "image" may include discrete points, which may be referred to as "image points," or, for convenience only, "image pixels."

[0021] The terms "encoding", "writing" and "addressing" are used to describe the process of providing a plurality of pixels of the SLM with a corresponding plurality of control values ​​that respectively determine the modulation level of each pixel. It can be said that the pixels of the SLM are configured to "display" a light modulation distribution in response to receiving the plurality of control values. Thus, the SLM can be said to "display" a hologram, and a hologram can be considered to be an array of light modulation values ​​or levels.

[0022] It has been found that holographic reconstructions of acceptable quality can be formed from "holograms" containing only phase information related to the Fourier transform of the original object. Such holographic recordings may be referred to as pure phase holograms. The embodiments relate to pure phase holograms, but the disclosure is equally applicable to pure amplitude holography.

[0023] The present disclosure is also equally applicable to forming a holographic reconstruction using amplitude and phase information related to the Fourier transform of the original object. In some embodiments, this is achieved by using complex modulation of a so-called fully complex hologram that contains amplitude and phase information related to the original object. Because the value (gray level) assigned to each pixel of the hologram has an amplitude and a phase component, such a hologram may be referred to as a fully complex hologram. The value (gray level) assigned to each pixel can be represented as a complex number with an amplitude and a phase component. In some embodiments, a fully complex computer-generated hologram is calculated.

[0024] Reference may be made to the phase value, phase component, phase information, or simply phase, of a pixel of a computer-generated hologram or spatial light modulator as shorthand for "phase delay". That is, any phase value described is actually a number (e.g., in the range of 0 to 2π) representing the amount of phase delay provided by that pixel. For example, a pixel of a spatial light modulator described as having a phase value of π / 2 will delay the phase of the received light by π / 2 radians. In some embodiments, each pixel of the spatial light modulator may be operated at one of a plurality of possible modulation values ​​(e.g., phase delay values). The term "grayscale" may be used to refer to a plurality of available modulation levels. For example, the term "grayscale" may be used for convenience to refer to a plurality of available phase levels in a pure phase modulator, even though the different phase levels do not provide different shades of gray. For convenience, the term "grayscale" may also be used to refer to a plurality of available complex modulation levels in a complex modulator.

[0025] Thus, a hologram comprises an array of gray levels, i.e. an array of light modulation values, such as phase delay values ​​or an array of complex modulation values. A hologram is also considered to be a diffraction pattern, since it is a pattern that causes diffraction when displayed on a spatial light modulator and illuminated with light of a wavelength relative to (usually less than) the pixel pitch of the spatial light modulator. Reference is made herein to combining a hologram with other diffraction patterns, such as a diffraction pattern used as a lens or a grating. For example, a diffraction pattern used as a grating may be combined with a hologram to shift the replay field on the replay plane, or a diffraction pattern used as a lens may be combined with a hologram to focus the holographic reconstruction on the replay plane in the near field.

[0026] Although different embodiments and embodiment groups may be disclosed separately in the following detailed description, any feature of any embodiment or embodiment group may be combined with any other feature or combination of features of any embodiment or embodiment group. That is, all possible combinations and permutations of the features disclosed in this disclosure are contemplated. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Specific embodiments are described by way of example only with reference to the following drawings:

[0028] Figure 1 is a schematic diagram showing a reflective SLM producing a holographic reconstruction on a screen;

[0029] Figure 2 An image for projection is shown, comprising eight image regions / components V1 to V8, and corresponding cross-sections of hologram channels H1-H8;

[0030] Figure 3 shows a hologram displayed on an LCOS that directs light to multiple discrete areas;

[0031] Figure 4 Shown includes display such as Figure 2 and Figure 3 A system for displaying a computer generated hologram as shown;

[0032] FIG5 shows a perspective view of a first example two-dimensional pupil expander comprising two replicators;

[0033] Fig. 6A and Figure 6B is a schematic diagram of an automotive head-up display system showing potential areas of sunlight glare;

[0034] Figure 7 is a schematic diagram of a light control layer formed on a transmissive surface of a pupil expander of an automotive head-up display system;

[0035] Figure 8 is a polar plot showing a simulation of solar glare from different sun elevation angles at the center of a viewing area of ​​an automotive head-up display including a waveguide pupil expander according to a comparative example;

[0036] Fig. 9 is with Figure 8 an equivalent polar plot showing a simulation of solar glare from different sun elevation angles at the center of a viewing area of ​​an automotive heads-up display including a waveguide pupil expander with reflection suppression, according to an embodiment;

[0037] Fig.10 is a schematic diagram of a waveguide pupil expander for a display system showing examples of sunlight that may be received and reflected toward a viewing area, and

[0038] Fig.11A and Fig. 11B According to an embodiment of the present disclosure, the Fig.10 Schematic diagram of a waveguide pupil expander.

[0039] The same reference numbers will be used throughout the drawings to refer to the same or like parts. DETAILED DESCRIPTION

[0040] The present invention is not limited to the embodiments described below, but extends to the full scope of the appended claims. That is, the present invention can be implemented in different forms and should not be construed as limited to the described embodiments, which are set forth for illustrative purposes.

[0041] Unless otherwise stated, terms in the singular may include plural forms.

[0042] A structure described as being formed on / under another structure or above / below another structure should be construed to include the case where the structures are in contact with each other and, further, also include the case where a third structure is provided therebetween.

[0043] Optical components may comprise primary surfaces and secondary surfaces. For example, in the case of a (bulk optical) waveguide pupil expander, the longitudinally extending first and second parallel reflective surfaces for waveguiding light therebetween form the primary surfaces, while the other surfaces - edge faces at its side walls and end walls - form secondary surfaces, and are typically in planes orthogonal to the planes of the primary surfaces.

[0044] When describing a temporal relationship, for example, when the temporal order of events is described as "after," "subsequently," "next," "before," etc., the present disclosure should be considered to include both sequential and non-sequential events unless otherwise specified. For example, unless terms such as "just," "immediately," or "directly" are used, the description should be considered to include non-sequential situations.

[0045] Although the terms "first", "second", etc. may be used herein to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish between various elements. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the appended claims.

[0046] The features of different embodiments may be coupled or combined with each other in part or in whole, and may interoperate with each other in different ways. Some embodiments may be performed independently of each other, or may be performed together in a mutually dependent relationship.

[0047] In the present disclosure, the term "substantially" when applied to a structural unit of a device may be interpreted as a technical feature of the structural unit produced within the technical tolerance of the method for manufacturing it.

[0048] Traditional optical configuration for holographic projection

[0049] Figure 1 An embodiment is shown in which a computer generated hologram is encoded on a single spatial light modulator. The computer generated hologram is a Fourier transform of the object used for reconstruction. Therefore, it can be said that the hologram is a Fourier domain or frequency domain or spectral domain representation of the object. In this embodiment, the spatial light modulator is a reflective liquid crystal on silicon "LCOS" device. The hologram is encoded on the spatial light modulator and a holographic reconstruction is formed at a playback field, such as a light receiving surface such as a screen or diffuser.

[0050] A light source 110, such as a laser or laser diode, is arranged to illuminate the SLM 140 via a collimating lens 111. The collimating lens causes a substantially planar wavefront of light to be incident on the SLM. Figure 1 In some embodiments, the direction of the wavefront is off-normal (e.g., two or three degrees from a plane that is truly normal to the transparent layer). However, in other embodiments, a substantially planar wavefront is provided at normal incidence and a beam splitter arrangement is used to separate the input and output optical paths. Figure 1In the embodiment shown, the arrangement is such that light from the light source reflects from the mirrored rear surface of the SLM and interacts with the light modulating layer to form an exit wavefront 112. The exit wavefront 112 is applied to an optical device including a Fourier transform lens 120, the focus of which is located at a screen 125. More specifically, the Fourier transform lens 120 receives the modulated light beam from the SLM 140 and performs a frequency-space transform to produce a holographic reconstruction at the screen 125.

[0051] It is important to note that in this type of hologram, every pixel of the hologram contributes to the entire reconstruction. There is no one-to-one correlation between a specific point on the replay field (or image pixel) and a specific light modulation element (or hologram pixel). In other words, the modulated light leaving the light modulation layer is distributed over the entire replay field.

[0052] In these embodiments, the position of the holographic reconstruction in space is determined by the power (focus) of the Fourier transform lens. Figure 1 In the illustrated embodiments, the Fourier transform lens is a physical lens. That is, the Fourier transform lens is an optical Fourier transform lens and performs a Fourier transform optically. Any lens can act as a Fourier transform lens, but the performance of the lens will limit the accuracy of the Fourier transform it performs. The skilled person understands how to use a lens to perform an optical Fourier transform. In some embodiments of the present disclosure, the lens of the observer's eye performs the conversion of the hologram to the image.

[0053] Hologram computing

[0054] In some embodiments, the computer generated hologram is a Fourier transform hologram, or simply a Fourier hologram or a Fourier-based hologram, where the image is reconstructed in the far field by utilizing the Fourier transform properties of a positive lens. The Fourier hologram is calculated by Fourier transforming the desired light field in the replay plane back to the lens plane. The computer generated Fourier hologram can be calculated using the Fourier transform. By way of example only, the embodiments relate to Fourier holography and Gerchberg-Saxton type algorithms. The present disclosure is equally applicable to Fresnel holography and Fresnel holograms that can be calculated by similar methods. In some embodiments, the hologram is a phase or pure phase hologram. However, the present disclosure is also applicable to holograms calculated by other techniques, such as techniques based on point cloud methods.

[0055] In some embodiments, the hologram engine is arranged to exclude from the hologram calculation the contribution of light blocked by the limiting aperture of the display system. UK patent application 2101666.2, filed on February 5, 2021 and incorporated herein by reference, discloses a first hologram calculation method in which eye tracking and ray tracing are used to identify sub-areas of a display device for calculating a point cloud hologram that eliminates ghost images. The sub-areas of the display device correspond to the aperture of the present disclosure and are used to exclude light paths from the hologram calculation. UK patent application 2112213.0, filed on August 26, 2021 and incorporated herein by reference, discloses a second method based on a modified Gerchberg-Saxton type algorithm, which includes a step of performing light field clipping according to the pupil of the optical system during the hologram calculation. The clipping of the light field corresponds to the determination of the limiting aperture of the present disclosure. UK patent application 2118911.3, filed on 23 December 2021 and also incorporated herein by reference, discloses a third method of computing a hologram, the method comprising the step of determining the area of ​​a so-called extended modulator formed by a hologram replicator. According to the present disclosure, the area of ​​the extended modulator is also the aperture.

[0056] In some embodiments, a real-time engine is provided that is arranged to receive image data and calculate a hologram in real time using an algorithm. In some embodiments, the image data is a video comprising a sequence of image frames. In other embodiments, the hologram is pre-calculated, stored in a computer memory and called up as needed for display on the SLM. That is, in some embodiments, a repository of predetermined holograms is provided.

[0057] Large field of view and / or eye box using small display devices

[0058] In general, the present disclosure relates to image projection. It relates to a method of image projection and an image projector including a display device. The present disclosure also relates to a projection system including an image projector and an observation system, wherein the image projector projects or relays light from the display device to the observation system. The present disclosure is equally applicable to monocular and binocular observation systems. The observation system may include one or more eyes of an observer. The observation system includes an optical element with optical focal length (e.g., a lens of a human eye) and an observation plane (e.g., a retina of a human eye). The projector may be referred to as a "light engine". The display device and the image formed (or perceived) using the display device are spatially separated from each other. The observer forms or perceives the image on the display plane. In some embodiments, the image is a virtual image, and the display plane may be referred to as a virtual image plane. In other examples, the image is a real image formed by holographic reconstruction, and the image is projected or relayed to the observation plane. In these other examples, the spatially modulated light of the intermediate holographic reconstruction formed in free space or on a screen or other light receiving surface between the display device and the observer is propagated to the observer. In both cases, the image is formed by illuminating a diffraction pattern (eg a hologram or kinoform) displayed on a display device.

[0059] The display device includes pixels. The pixels of the display can display a diffraction pattern or structure of diffracted light. The diffracted light can form an image on a plane that is spatially separated from the display device. According to well-known optical principles, the magnitude of the maximum diffraction angle is determined by the size of the pixel and other factors such as the wavelength of the light.

[0060] In an embodiment, the display device is a spatial light modulator, such as a liquid crystal on silicon ("LCOS") spatial light modulator (SLM). Light is transmitted from the LCOS to a viewing entity / system such as a camera or eye within a range of diffraction angles (e.g., from zero to a maximum diffraction angle). In some embodiments, amplification techniques can be used to increase the range of available diffraction angles beyond the conventional maximum diffraction angle of the LCOS.

[0061] In some embodiments, (the light of) the hologram itself is transmitted to the eye. For example, the spatially modulated light of the hologram (not yet fully converted to a holographic reconstruction, i.e., an image) - which can be informally referred to as being "encoded" with / by the hologram - is transmitted directly to the eye of the observer. The observer can perceive a real or virtual image. In these embodiments, no intermediate holographic reconstruction / image is formed between the display device and the observer. It is sometimes said that in these embodiments, the lens of the eye performs the conversion or transformation of the hologram to the image. The projection system or light engine can be configured so that the observer effectively looks directly into the display device.

[0062] The "light field" mentioned here is a "composite light field". The term "light field" simply means a light pattern with finite size in at least two orthogonal spatial directions, such as x and y. The term "light field" simply means a light pattern with finite size in at least two orthogonal spatial directions (x and y). The word "complex" used here simply means that the light at each point in the light field can be defined by an amplitude value and a phase value, and can therefore be represented by a complex number or a pair of values. For the purpose of hologram calculation, the composite light field can be a two-dimensional array of complex numbers, where the complex numbers define the intensity and phase of light at multiple discrete locations within the light field.

[0063] According to well-known optical principles, the angular range of light propagating from a display device that can be observed by an eye or other viewing entity / system varies with the distance between the display device and the viewing entity. For example, at a viewing distance of 1 meter, only a small range of angles from the LCOS can propagate through the pupil of the eye to form an image on the retina at a given eye position. The angular range of light propagating from the display device that can successfully propagate through the pupil of the eye to form an image on the retina at a given eye position determines the portion of the image that is "visible" to the observer. In other words, not all portions of the image are visible from any point on the viewing plane (e.g., any one eye position within an viewing window such as an eye box).

[0064] In some embodiments, the image perceived by the observer is a virtual image that appears upstream of the display device, that is, the observer perceives the image as being farther away from them than the display device. Therefore, conceptually, the observer can be thought of as observing the virtual image through a "window the size of the display device", which can be very small, such as 1 cm in diameter, and at a relatively large distance, such as 1 meter. And the user will be observing the display device-sized window through the pupil of their eye, which can also be very small. Therefore, at any given time, the field of view becomes smaller, and the specific range of angles that can be seen depends heavily on the eye position.

[0065] Pupil expanders address how to increase the angular range of light propagating from a display device and that can successfully propagate through the pupil of the eye to form an image. Display devices are typically (relatively) small and have (relatively) large projection distances. In some embodiments, the projection distance is at least one order of magnitude, such as at least two orders of magnitude, larger than the diameter or width of the entrance pupil and / or aperture of the display device (i.e., the size of the pixel array).

[0066] The use of a pupil expander increases the viewing area (i.e., the user's eye box) laterally, thereby enabling some eye movement while still enabling the user to see the image. As will be appreciated by the skilled artisan, in an imaging system, the viewing area (the user's eye box) is the area where the viewer's eye can perceive the image. The present disclosure encompasses non-infinite virtual image distances - i.e., near-field virtual images.

[0067] Traditionally, a two-dimensional pupil expander comprises one or more one-dimensional optical waveguides, each formed using a pair of opposing reflective surfaces, wherein the output light from the surfaces forms an observation window or eye box. Light received from a display device (e.g., spatially modulated light from an LCOS) is replicated by the or each waveguide to increase the field of view (or observation area) in at least one dimension. In particular, the waveguide enlarges the observation window due to the generation of additional light rays or "copies" by dividing the amplitude of the incident wavefront.

[0068] The display device may have an active or pixel display area having a first dimension of less than 10 cm, such as less than 5 cm or less than 2 cm. The propagation distance between the display device and the viewing system may be greater than 1 m, such as greater than 1.5 m or greater than 2 m. The optical propagation distance within the waveguide may be up to 2 m, such as up to 1.5 m or up to 1 m. The method is capable of receiving an image and determining a corresponding hologram of sufficient quality in less than 20 m, such as less than 15 m or less than 10 m.

[0069] In some embodiments described only by examples of diffraction or holographic light fields according to the present disclosure, the hologram is configured to route light into multiple channels, each corresponding to a different portion (i.e., sub-region) of the image. The channels formed by the diffraction structure are referred to here as "hologram channels" simply to reflect that they are light channels encoded by holograms with image information. It can be said that the light of each channel is in the holographic domain, rather than in the image or spatial domain. In some embodiments, the hologram is a Fourier or Fourier transform hologram, so the hologram domain is the Fourier or frequency domain. The hologram can also be a Fresnel or Fresnel transform hologram. The hologram can also be a point cloud hologram. The hologram is described herein as routing light into multiple hologram channels to reflect that the image that can be reconstructed from the hologram has a finite size and can be arbitrarily divided into multiple image sub-regions, where each hologram channel will correspond to each image sub-region. Importantly, the hologram of this example is characterized by how it distributes the image content when it is illuminated. Specifically and uniquely, the hologram divides the image content by angle. That is, every point on the image is associated with a unique ray angle in the spatially modulated light formed by the hologram when illuminated - at least a unique pair of angles, since the hologram is two-dimensional. For the avoidance of doubt, this holographic behavior is not conventional. When illuminated, the spatially modulated light formed by this particular type of hologram can be separated into multiple hologram channels, each of which is defined by a range of ray angles (in two dimensions). It will be understood from the above that any hologram channel (i.e., a sub-range of ray angles) that can be considered in the spatially modulated light will be associated with a corresponding portion or sub-region of the image. That is, all of the information required to reconstruct that portion or sub-region of the image is contained within the angular sub-range of the spatially modulated light formed by the hologram of the image. When the spatially modulated light is observed as a whole, there is not necessarily any evidence of multiple discrete light channels.

[0070] Nevertheless, the hologram can still be recognized. For example, if only continuous portions or sub-regions of the spatially modulated light formed by the hologram are reconstructed, only sub-regions of the image should be visible. If different continuous portions or sub-regions of the spatially modulated light are reconstructed, different sub-regions of the image should be visible. Another identifying feature of this type of hologram is that the shape of the cross-section of any hologram channel substantially corresponds to the shape of the entrance pupil (i.e., substantially the same), although the size may be different—at least at the correct plane where the hologram is calculated. Each light / hologram channel propagates from the hologram at a different angle or range of angles. Although these are example ways to characterize or identify this type of hologram, other ways may also be used. In summary, the holograms disclosed herein are characterized and identified by how the image content is distributed within the light encoded by the hologram. In addition, to avoid any doubt, references herein to holograms configured to guide light or to angularly divide an image into multiple hologram channels are only by way of example, and the present disclosure is equally applicable to any type of holographic light field or even any type of diffraction or pupil expansion of a diffracted light field.

[0071] The system can be provided in a compact and streamlined physical form. This makes the system suitable for a wide range of practical applications, including those where space is limited and asset value is high. For example, it can be implemented in a head-up display (HUD), such as a vehicle or automotive HUD.

[0072] According to the present disclosure, a pupil expansion is provided for diffracted light, which may include a diverging bundle of light rays. The diffracted light field may be defined by a "light cone". Thus, the size of the diffracted light field (as defined in a two-dimensional plane) increases with propagation distance from the corresponding diffractive structure (i.e., the display device). It can be said that the pupil expander replicates the hologram or forms at least one replica of the hologram to convey that the light transmitted to the observer is spatially modulated according to the hologram.

[0073] In some embodiments, two one-dimensional waveguide pupil expanders are provided, each of which is arranged to effectively increase the size of the exit pupil of the system by forming multiple copies or replicas of the exit pupil (or the light of the exit pupil) of the spatial light modulator. The exit pupil can be understood as the physical area where the system outputs light. It can also be said that each waveguide pupil expander is arranged to expand the size of the exit pupil of the system. It can also be said that each waveguide pupil expander is arranged to expand / increase the size of the eye box in which the observer's eyes can be located in order to see / receive the light output by the system.

[0074] Optical channels in the holographic domain

[0075] Holograms formed in accordance with some embodiments angularly divide the image content to provide multiple hologram channels that may have a cross-sectional shape defined by the aperture of the optical system. The hologram is calculated to provide this guidance of the diffracted light field. In some embodiments, this is achieved by taking into account the aperture (virtual or real) of the optical system during the calculation of the hologram, as described above.

[0076] Figure 2 and Figure 3 An example of this type of hologram is shown, which can be used in conjunction with the pupil expander disclosed herein. However, this example should not be viewed as limiting the present disclosure.

[0077] Figure 2 An image 252 is shown for projection, comprising eight image regions / components V1 to V8. By way of example only, Figure 2 Eight image components are shown, and image 252 may be separated into any number of components. Figure 2 Also shown is a coded light pattern 254 (ie, hologram) that can reconstruct image 252 - for example, when transformed by a lens of a suitable viewing system. Coded light pattern 454 includes first through eighth sub-holograms or components H1 through H8, corresponding to first through eighth image components / regions V1 through V8. Figure 2 It further shows how a hologram breaks down the image content by angle. Therefore, a hologram is characterized by its guidance of light. Figure 3 Specifically, the hologram in this example directs light into multiple discrete regions. In the example shown, the discrete regions are disks, but other shapes are also contemplated. After propagation through the waveguide, the size and shape of the optimal disk can be related to the size and shape of the aperture of the optical system (e.g., the entrance pupil of the observation system).

[0078] Figure 4 A system 400 is shown, including a display such as Figure 2 and Figure 3 A display device for a computed hologram is shown.

[0079] The system 400 comprises a display device which in this arrangement comprises an LCOS 402. The LCOS 402 is arranged to display a modulation pattern (or "diffraction pattern") comprising a hologram and projects light which has been holographically encoded to an eye 405 which comprises a pupil acting as an aperture 404, a lens 409 and a retina (not shown) acting as an observation plane. There is a light source (not shown) arranged to illuminate the LCOS 402. The lens 409 of the eye 405 performs the conversion of the hologram to an image. The light source may be of any suitable type. For example, it may comprise a laser source.

[0080] The viewing system 400 also includes a waveguide 408 located between the LCOS 402 and the eye 405. The presence of the waveguide 408 enables all angular content from the LCOS 402 to be received by the eye, even at the relatively large projection distance shown. This is because the waveguide 408 acts as a pupil expander in a well-known manner and is therefore only briefly described here.

[0081] in short, Figure 4 The waveguide 408 shown comprises a substantially elongated structure. In this example, the waveguide 408 comprises an optical plate of a refractive material, but other types of waveguides are also well known and can be used. The waveguide 408 is positioned to intersect the light cone (i.e., the diffracted light field) projected from the LCOS 402, for example, at an oblique angle. In this example, the size, position, and positioning of the waveguide 408 are configured to ensure that light from each of the eight light beams within the light cone enters the waveguide 408. The light from the light cone enters the waveguide 408 via a first planar surface of the waveguide 408 (positioned closest to the LCOS 402) and is guided at least partially along the length of the waveguide 408 before being emitted via a second planar surface of the waveguide 408 that is substantially opposite to the first surface (positioned closest to the eye). It is easy to understand that the second planar surface is partially reflective and partially transmissive. In other words, when each light ray propagates from the first planar surface within the waveguide 408 and strikes the second planar surface, some of the light will be transmitted out of the waveguide 408 and some of the light will be reflected back to the first planar surface by the second planar surface. The first planar surface is reflective so that all light striking it from within the waveguide 408 will be reflected back toward the second planar surface. Thus, some light may simply be refracted between the two planar surfaces of the waveguide 408 before being transmitted, while other light may be reflected and may therefore experience one or more reflections (or "bounces") between the planar surfaces of the waveguide 408 before being transmitted.

[0082] Figure 4 A total of nine "bounce" points B0 to B8 are shown along the length of waveguide 408. Figure 2 As shown, light associated with all points of the image (V1-V8) is transmitted out of the waveguide at each "bounce" from the second planar surface of the waveguide 408, but only light from one angular portion of the image (e.g., light from one of V1 to V8) has a trajectory that enables it to reach the eye 405 from each corresponding "bounce" point B0 to B8. In addition, light from different angular portions of the image (V1 to V8) reaches the eye 405 from each corresponding "bounce" point. Therefore, at Figure 4 In the example of FIG. 4 , each angular channel of coded light reaches the eye from waveguide 408 only once.

[0083] Although virtual images have been discussed generally herein, which require the eye to convert received modulated light to form a perceived image, the methods and apparatus described herein can be applied to real images.

[0084] 2D pupil expansion

[0085] Although Figure 4 The arrangement shown includes a single waveguide that provides pupil expansion in one dimension, but pupil expansion may be provided in more than one dimension, for example in two dimensions. Figure 4 The examples in use a hologram that has been calculated to create channels of light, each corresponding to a different portion of an image, but the present disclosure and the systems described below are not limited to this type of hologram.

[0086] FIG. 5A shows a perspective view of a system 500 comprising two replicators 504 , 506 arranged to expand a light beam 502 in two dimensions.

[0087] In the system 500 of FIG. 5A , the first replicator 504 includes a first pair of surfaces stacked parallel to each other, arranged in a manner similar to Figure 4 The first pair of surfaces are similar in size and shape to each other (in some cases identical) and are substantially elongated in one direction. The collimated light beam 502 is directed to an input on a first replicator 504. Due to internal reflection processes between the two surfaces, and partial transmission of light from each of a plurality of output points on one of the surfaces (the upper surface, as shown in FIG. 5A ), which are familiar to the skilled reader, the light of the light beam 502 is replicated in a first direction along the length of the first replicator 504. Thus, a first plurality of replica light beams 508 are emitted from the first replicator 504 toward the second replicator 506.

[0088] The second replicator 506 includes a second pair of surfaces stacked parallel to each other, arranged to receive each collimated beam of the first plurality of beams 508, and further arranged to provide replication or pupil expansion by expanding each of these beams in a second direction substantially orthogonal to the first direction. The size and shape of the first pair of surfaces are similar to each other (in some cases the same), and are substantially rectangular. The rectangular shape is implemented for the second replicator so that it has a length along the first direction to receive the first plurality of beams 508, and has a length along the second orthogonal direction to provide replication in the second direction. Due to the internal reflection process between the two surfaces, and the partial transmission of light from each of the plurality of output points on one of the surfaces (the upper surface as shown in FIG. 5A), the light of each beam within the first plurality of beams 508 is replicated in the second direction. Therefore, a second plurality of beams 510 is emitted from the second replicator 506, wherein the second plurality of beams 510 includes a replica of the input beam 502 along each of the first direction and the second direction. Therefore, the second plurality of beams 510 can be viewed as a two-dimensional grid or array including replica beams.

[0089] Thus, it can be said that the first and second replicators 504, 505 of Figure 5A combine to provide a two-dimensional replicator (or "two-dimensional pupil expander"). Thus, the replica beam 510 can be emitted along an optical path to an expanded eye box of a display system, such as a heads-up display.

[0090] In the system of FIG. 5A , the first replicator 504 is a waveguide comprising a pair of elongated rectilinear reflective surfaces stacked parallel to each other, and similarly, the second replicator 504 is a waveguide comprising a pair of rectangular reflective surfaces stacked parallel to each other. In other systems, the first replicator may be a solid elongated rectilinear waveguide and the second replicator may be a solid planar rectangular waveguide, wherein each waveguide comprises an optically transparent solid material, such as glass. In this case, the pair of parallel reflective surfaces are formed by a pair of opposing major side walls, optionally including corresponding reflective and reflective-transmissive surface coatings, which are familiar to the skilled reader.

[0091] Figure 5B A perspective view of a system 500 is shown, the system comprising two replicators 520 , 540 arranged for replicating a light beam 522 in two dimensions, wherein the first replicator is a solid elongated waveguide 520 and the second replicator is a solid planar waveguide 540 .

[0092] exist Figure 5BIn the system of FIG. 5 , the first replicator / waveguide 520 is arranged such that its pair of elongated parallel reflective surfaces 524a, 524b are perpendicular to the plane of the second replicator / waveguide 540. Thus, the system includes an optical coupler arranged to couple light from the output port of the first replicator 520 to the input port of the second replicator 540. In the arrangement shown, the optical coupler is a plane / folding mirror 530 arranged to fold or redirect the optical path of the light to achieve the desired optical coupling from the first replicator to the second replicator. Figure 5B As shown, a mirror 530 is arranged to receive light from the output port / reflection-transmission surface 524a of the first replicator / waveguide 520, comprising a one-dimensional array of replicas extending in a first dimension. The mirror 530 is tilted so as to redirect the received light at an angle into the optical path of the input port in the (totally) reflective surface of the second replicator 540 to provide waveguide and replica formation along its length in the second dimension. It should be understood that the mirror 530 is one example of an optical element capable of redirecting light in the manner shown, and one or more other elements may alternatively be used to perform this task.

[0093] In the arrangement shown, the (partial) reflection-transmission surface 524a of the first replicator 520 is adjacent to an input port of the first replicator / waveguide 520 that receives the input light beam 522 at an angle to provide waveguide and replica formation along its length in the first dimension. Thus, the input port of the first replicator / waveguide 520 is located at its input end, on the same surface as the reflection-transmission surface 524a. The skilled reader will appreciate that the input port of the first replicator / waveguide 520 may be at any other suitable location.

[0094] therefore, Figure 5B The arrangement enables the first replicator 520 and the mirror 530 to be provided as part of a first relatively thin layer in a first and third dimensional plane (illustrated as the xz plane). Specifically, the size or "height" of the first planar layer (in which the first replicator 520 is located) in the second dimension (illustrated as the y dimension) is reduced. The mirror 530 is configured to direct light away from the first layer / plane (i.e., the "first planar layer") where the first replicator 520 is located, and direct it to the second layer / plane (i.e., the "second planar layer") where the second replicator 540 is located, which is located above the first layer / plane and substantially parallel thereto. Therefore, the overall size or "height" of the system - including the first and second replicators 520, 540 and the mirror 530 in the first and third dimensions (illustrated as the xz plane) - in the second dimension (illustrated as the y dimension) - located in the stacked first and second planar layers - is compact. The skilled reader will understand that the system for implementing the present disclosure is compact and can be used to implement the present disclosure. Figure 5B Many variations of the arrangements are possible and contemplated.

[0095] Suppresses reflections to reduce glare

[0096] In operation, the transmission / exit surface of the second replicator 506 of the two-dimensional pupil expander of FIG. 5 (i.e., the expanded exit pupil) forms an external surface or "output port" from which image light is transmitted through the air to the eye box area for observation. Therefore, the transmission surface may be exposed to sunlight from the environment in which the head-up display is used. If used in conjunction with the pupil expander 506, the received sunlight may cause glare to the observer, particularly due to reflection of sunlight associated with the pupil expander 506 and / or the turning film. For example, glare may occur if sunlight is directly reflected from the external transmission surface or other surface of the pupil expander 506 at a certain angle so that the sunlight reaches the observation area / eye box directly along the optical path. This is described herein as "direct glare". In another example, glare may occur if sunlight is coupled into pupil expander 506 at an angle such that the sunlight rays follow the same optical path as the image rays within the pupil expander, or are reflected by its surface, so as to reach the viewing area / eye box indirectly (e.g., via an optical combiner such as a vehicle windshield). This is described herein as "veil glare".

[0097] Fig. 6A The optical path of a sunlight ray S incident on the transmission / exit surface 642 of a (bulk optical) waveguide pupil expander 640 of a head-up display (HUD) in an automotive application is shown. In particular, sunlight S at a relatively high elevation angle relative to the horizon is incident on the external transmission / exit surface 642 of the pupil expander 640 through the vehicle windshield 630. In this example, the transmission / exit surface 642 is located in a substantially horizontal plane in an aperture of the vehicle dashboard (not shown). Some sunlight rays D may be directly reflected from the pupil expander 640 toward the viewing area / eye box (e.g., through one or more of its reflective layers) and cause "direct glare". Some other rays V may be indirectly reflected from the pupil expander 640 (e.g., through one or more of its reflective layers) via the windshield 730 toward the viewing area / eye box and cause "veil glare". Therefore, the rays V may travel along the same optical path as the image light output from the pupil expander 640. In either case, the glare generated by the reflected sunlight may be harmful to the observer / driver. Figure 6B A view at the viewing area / eyebox is shown, indicating the area of ​​the windshield and instrument panel from which the observer / driver may receive solar glare. An area of ​​direct glare D is seen at the exit / transmission surface of the vehicle instrument panel (not shown), and an area of ​​veil glare V is seen at the vehicle windshield. Those skilled in the art will understand that the presence of glare from different locations within the shown areas D and V at a particular point in time may depend on the elevation angle of the sun and the configuration of the display system (interior and in situ).

[0098] Light control layer

[0099] Therefore, the inventors propose to use an optical component including a light control layer on the transmissive surface of the second replicator / pupil expander (or more generally the output port of the HUD) to reduce the risk of glare to the observer. An example light control layer for controlling the direction of received sunlight includes a plurality of parallel louvers formed of light absorbing, light attenuating or similar materials. The inventors have recognized that a one-dimensional array of louvers, typically in the form of longitudinal rectangular louvers, can be used to control the direction and / or suppress reflection of sunlight that may be incident on the transmissive surface / output port of the HUD due to its upward / horizontal orientation in the vehicle dashboard adjacent to the vehicle windshield. The orientation (e.g. sidewall angle), spacing and geometry (e.g. length, width and thickness) of the louvers can be selected to allow image light to be transmitted from the HUD at the desired range of angles required to reach the viewing area / eye box.

[0100] Figure 7 A light control layer in the form of a louver structure 706 is shown for reducing glare due to reflected sunlight. The louver structure 706 includes a plurality of parallel louvers / louvers 710 arranged in a one-dimensional array in a second dimension (illustrated as the y-dimension). Thus, the length (long dimension) of the louvers / louvers 710 is parallel to the first dimension (illustrated as the x-dimension) of the waveguide pupil expander 740 and orthogonal to the second dimension. The louvers 710 include a light absorbing or light attenuating (e.g., light diffusing) material to block light incident thereon.

[0101] In the arrangement shown, the louver structure 706 is disposed on a substantially planar transmissive surface 742 forming an output port of a second replicator / waveguide pupil expander 740 which is arranged to internally reflect and replicate image light I to provide pupil expansion in a second dimension (illustrated as the y-dimension). Figure 7As shown, in use, the transmission surface 742 of the waveguide pupil expander 740 is substantially horizontal and directly faces the windshield 730 of the vehicle, which forms an optical combiner of the HUD display system. In the arrangement shown, the louvers / louvers 710 have a longitudinal straight shape with parallel rectangular side walls. The louvers / louvers 710 (the side walls) of the louver structure 706 are arranged to form an acute angle θ with the surface normal of the transmission surface (i.e., in a non-orthogonal plane). The tilted orientation of the louvers 710 enables the light of the replica of the image light I formed and output by the waveguide pupil expander 740 at the transmission surface 742 to pass between the louvers 710 without deviating from the desired optical path to the observation area / eye box via the windshield 730, as shown by the arrow of the image light I line. Therefore, the angle θ is in the direction of the replica of the image light I, and therefore in the direction of the pupil expansion through the waveguide pupil expander 740 (illustrated from left to right in the y dimension). In other words, the louver is tilted relative to the surface normal of the transmission surface 742 in the same direction as the propagation axis of the replica of the image light I.

[0102] In addition, an optional transparent structure 760 having a longitudinally rectilinear shape similar to the louver plates 710 is arranged at a certain angle between adjacent louver plates 710 (e.g., having a width (or cross-section) extending between near (e.g., substantially) the bottom of one louver plate and near (e.g., substantially) the top of an adjacent louver plate) to provide mechanical robustness to the protective cover of the louver structure 706 and the transmission surface 742. Therefore, the tilt angle of the transparent structure is different from (e.g., greater than) the tilt angle θ of the louver plates. The transparent structure 760 is configured (e.g., shaped) so that the light ray I of the image light output by the waveguide pupil expander 740 does not deviate from the desired optical path (e.g., due to refraction at its surface).

[0103] In the arrangement shown, the light control layer formed by the louver structure 706 can reduce the sun glare for the observer at the viewing area / eye box. In particular, Figure 7 A line of sunlight S1 from the sun at a first elevation angle (relative to the horizon) is shown, which passes through the windshield 730 and is incident on the louver structure 706. Some rays of sunlight S1 (not shown) may be directly incident on the louver plates 710, where the light is absorbed or attenuated without reaching the transmissive surface 742. In addition, some rays of sunlight S1 (shown) may be incident on the transparent structure 760 between the louver plates 710, as shown. Due to the configuration and orientation of the transparent structure 760, these rays of sunlight S1 may be specularly reflected by one or more surfaces of the transparent structure 760 in a direction back through the windshield 730, so that the reflected sunlight S1 is not incident on the windshield 730. 1R The line is directed onto the optical path away from the viewing area / eyebox as indicated by the arrow. Figure 7Also shown is a sunlight line S2 from a second elevation angle of the sun, which is higher / greater than the first elevation angle, and the sunlight also passes through the windshield 730 and is incident on the louver structure 706. Due to the configuration and orientation of the transparent structure 760, the sunlight line S2 may be specularly reflected in a direction by one or more surfaces of the transparent structure 760 onto one of the louvers 710 and thus absorbed or attenuated. This blocks / reduces the sunlight line S 2R The intensity of the reflected light, which may be directed toward the viewing area / eye box as shown by the arrow.

[0104] Sunlight reflection in the optical component below the light management layer

[0105] The light control layer includes a louver structure disposed on a first major surface of an optical component that receives sunlight, such as the transmissive surface of a waveguide pupil expander as described above, and the presence of the light control layer can suppress or reduce many possible sunlight reflections that may be directed along the optical path toward the viewing area of ​​the display system and cause glare. However, the inventors have discovered that there are still some possible sources of sunlight reflections that may be caused by internal reflections within the optical component below the louver structure, which may be able to be emitted through the louver structure and directed along the optical path to the viewing area and cause glare. Fig.10 Examples of reflections of sunlight from these sources are shown.

[0106] refer to Fig.10 , the first potential source of sunlight reflection is from a first type of sunlight S1, which is incident at a position relatively close to the first end 1044 of the waveguide pupil expander 1040—wherein the direction of pupil expansion is from its first end 1044 to the second end 1045. The first sunlight S1 is received in a direction (through the windshield 1030) so that the light is incident on the outer sub-surface (i.e., the outer edge face) at the first end 1044 of the waveguide pupil expander 1040. In the arrangement shown, the waveguide pupil expander 1040 includes a light redirecting layer 1046, including an array of redirecting prisms (herein referred to as a "light redirecting prism layer") disposed on its outer main transmission surface 1042. As described herein, the louver structure includes a one-dimensional array of air-spaced louvers / louvers arranged on (the top of the inclined surface of) the prisms of the light redirecting prism layer 1046. The illustrated first sunlight S1 line is incident on the outer sub-surface / edge face at the first end 1044 of the light redirecting prism layer 1048. As shown Fig.10 As shown, the first sunlight ray S1 is reflected from the inclined surface 1043 of the prism of the light redirecting prism layer 1048, and the reflected first sunlight ray S 1R The light is directed toward the observation area onto the light path between a pair of louvers of the louver structure 1006, as shown by the arrow.

[0107] A second potential source of sunlight reflection is from the second and third types of sunlight S2 and S3, which are received in a direction (through the windshield 1030) so that the light is incident on the louver structure 1006 and transmitted into the light redirecting prism layer 1048 of the waveguide pupil expander 1040. Specifically, the second sunlight ray S2 is shown incident on the louver structure 1006 at an angle substantially the same as the orientation angle θ of the louvers / louvers. Therefore, the second sunlight ray S2 passes between a pair of louvers (optionally through a transparent structure between the louvers / louvers (not shown)) and enters the light redirecting prism layer 1048. The second sunlight ray S2 is shown to undergo several internal reflections within the light redirecting prism layer 1048. Specifically, the second sunlight ray S2 is first reflected from the internal sub-surface / edge face at the first end 1044 of the light redirecting prism layer 1048, and secondly reflected from the transmissive surface 1042 of the waveguide pupil expander 1040 at its interface with the light redirecting prism layer 1046. As a result, the reflected second sunlight ray S2 is shown. 2R The third sunlight ray S3 is directed toward the observation area in the direction indicated by the arrow to the optical path between a pair of louvers of the louver structure 1006. The third sunlight ray S3 shown in the figure is also incident on the louver structure 1006 at an angle substantially the same as the orientation angle θ of the louvers. Therefore, the third sunlight ray S3 passes between a pair of louvers (optionally through a transparent structure between the louvers / louver plates (not shown)) and enters the light redirection layer 1046. The third sunlight ray S3 shown in the figure undergoes several internal reflections in the light redirection prism layer 1048, which are different from the internal reflections of the second sunlight ray S2. Specifically, the third sunlight ray S3 is first reflected from the internal sub-surface / edge face at the first end 1044 of the light redirecting prism layer 1048, secondly reflected from the transmissive surface 1042 of the waveguide pupil expander 1040 at its interface with the light redirecting prism layer 1046, thirdly reflected from the inclined surface 1043 of the prism back into the light redirecting prism layer 1048, and fourthly reflected from the transmissive surface 1042 of the waveguide pupil expander 1040 at its interface with the light redirecting prism layer 1046. As a result, the reflected third sunlight ray S3 is shown in FIG. 2R The direction toward the viewing area indicated by the arrow is also directed to the optical path between a pair of louvers / louver plates of the louver structure 1006. In the case of both the second and third sunlight lines S2, S3, the incident angle on the inner sub-surface / edge surface at the first end 1044 of the light redirecting prism layer 1048 may be higher than the critical angle, resulting in total internal reflection. Therefore, the reflection intensity shown by the second and third sunlight lines S2, S3 may be high and cause glare in the viewing area.

[0108] Fig.10It is also shown how the louver structure 1006 suppresses reflections from the fourth type of sunlight S4, which in this example is incident on the louver structure 1006 at a position away from the first end 1044 of the waveguide pupil expander 1040, and is transmitted through the transmission surface 1042 into the light redirecting prism layer 1048 of the waveguide pupil expander 1040. Specifically, the fourth sunlight S4 line is shown incident on the louver structure 1000 at an angle substantially the same as the orientation angle θ of the louvers / louvers. Therefore, the fourth sunlight S4 line passes between a pair of louvers / louvers (optionally through a transparent structure (not shown) between the louvers) and enters the light redirecting prism layer 1048. Since the fourth sunlight ray S4 is incident on the louver structure 1006, farther from the first end 1044 than the second and third sunlight ray S2, S3, it experiences only a single reflection from the transmission surface 1042 of the waveguide pupil expander 1040 at the interface between the pair of louvers / louvers and the light redirecting prism layer 1046 before leaving the optical component between the pair of louvers / louvers. However, due to the louver arrangement, the fourth sunlight ray S4 is directed to the inclined side wall of one of the pair of louvers / louvers on the optical path, where it is absorbed or attenuated. In addition, any reflection from the side wall of one of the pair of louvers / louvers is reflected to the opposite side wall of the other of the pair of louvers / louvers, thereby further absorbing or attenuating the light. As a result, the reflection of the fourth sunlight ray S4 is suppressed and is not directed to the optical path toward the observation area, thereby causing glare.

[0109] As will be appreciated by those skilled in the art, the above examples of the first, second, third, and fourth types of sunlight depend on the elevation angle of the sun relative to the horizon (or conversely, the azimuth angle relative to the vertical) and other factors associated with the in-situ optical components (e.g., the shape of the windshield 1030 and the position and orientation angle of its transmissive surface 1042). Thus, the presence of these types of sunlight will depend on the time of day, the orientation of the optical components relative to the sun, etc.

[0110] Figure 8 is a polar plot for different solar elevation angles, showing a simulation of solar glare at the center of the viewing area of ​​an automotive head-up display including a waveguide pupil expander according to a comparative example. By convention, the origin of the polar plot (at the center) corresponds to the sun at 0° zenith angle (i.e., 90° elevation angle relative to the horizon) and is therefore vertical / directly above the HUD, and the concentric circles represent decreasing elevation angles at corresponding positions relative to the HUD (depicted at 10° intervals from 10° zenith angle to 90° zenith angle on the outer circle). As will be understood by those skilled in the art, the glare that appears at the center of the viewing area (i.e., eye box) is reasonably representative of the entire eye box. In the comparative example, the simulation is based on an example waveguide pupil expander including a light redirecting prism layer and a louver structure, such as Fig.10 shown.

[0111] Figure 8 Elliptical regions around the polar position of the sun are shown, which are found to produce strong sunlight glare (e.g., above a threshold intensity) in the center of the viewing area. The first, second, and third elliptical regions correspond to reflections S of the first, second, and third types of sunlight S1, S2, and S3. 1R , S 2R and S 3R , as mentioned above Fig.10 The simulation shows that the corresponding elliptical area S 1R , S 2R and S 3R The intensity of these types of reflected sunlight glare within can cause difficulties for observers, such as vehicle drivers or other similar applications where the direction and elevation angle of received sunlight changes dynamically over time.

[0112] Mitigation technology for solar reflection beneath the light control layer

[0113] As described above, the inventors hereby propose measures to solve the glare problem caused by the internal reflection of sunlight in the optical components under the louver structure. Those skilled in the art will understand that these measures are also applicable to the optical components of the display system that do not include the louver structure.

[0114] Fig.11A A first embodiment is shown. According to the first embodiment, the sub-surface of the optical component is arranged to absorb, attenuate and / or diffuse / reflect light. In the embodiment shown, the optical component is a light turning prism layer 1148. Fig.11A Also shown is a light redirecting prism layer 1148 disposed on the waveguide pupil expander 1140, and a louver structure 1106 disposed on the light redirecting prism layer 1148, as described above with reference to Fig.10Described. The subsurface of the optical component is parallel to the longitudinal dimension of the louver. Specifically, the light absorption / attenuation / diffuse reflection subsurface is the edge surface of the light redirecting prism layer 1148 at its first end 1144 (wherein the direction of pupil expansion is from the first end 1144 to the second end 1145). For example, the subsurface of the prism at the first end 1144 of the light redirecting prism layer 1148 may be coated with a light absorption, diffuse reflection / scattering and / or attenuation coating. In one example, the coating may be black paint applied to the outer subsurface / edge surface. In another example, the subsurface of the prism at the first end 1144 of the light redirecting prism layer 1148 may be processed (e.g., etched) or provided with a coating or film that diffusely reflects / scatters light incident thereon. In examples where the subsurface diffusely reflects or scatters incident light, the reflected light is also attenuated. The inventors propose a hemispherical diffuse reflection of less than 10%, optionally less than 4%. This can be achieved through a combination of a light absorbing coating (e.g., black paint) and treating the surface to provide surface roughness (e.g., by etching) to diffusely reflect incident light. Those skilled in the art will appreciate that a variety of alternatives to coating or treatment on the subsurface / edge face are possible, including arrangements that include any other type of material, element, or component that absorbs, attenuates, and / or diffusely reflects / scatters light incident thereon.

[0115] By providing a light absorbing, attenuating or diffusely reflecting / scattering sub-surface / edge face at the first end 1144 of the prisms of the light redirecting prism layer 1148, light corresponding to the second and third sunlight S2, S3 is suppressed. In particular, as Fig.11A As shown, the second and third sunlight S2, S3 lines incident on the louver structure 1106 between the louver pairs are directly or indirectly incident on the internal sub-surface / edge surface at the first end 1144, and are therefore absorbed, attenuated and / or diffusely reflected, as shown by the arrows. Therefore, when the second and third sunlight S2, S3 lines are incident on the sub-surface / edge surface at the first end 1144 of the prism of the light redirecting prism layer 1148 at an angle higher than the critical angle, the intensity of the total internal reflection light is reduced. In the case where the light is diffusely reflected / scattered, a reduced proportion of the second and third sunlight S2, S3 lines reaches the observation area along the light path, thereby reducing the risk of glare for the observer.

[0116] Fig. 11B A second embodiment is shown which is substantially identical to the first embodiment. However, according to the second embodiment, the light absorbing / attenuating / diffuse reflecting sub-surface extends above the prisms of the light redirecting prism layer 1148 at the first end 1144 (e.g., in the region between the prisms and the louver structures). In the case where the inclined surfaces of adjacent prisms of the light redirecting prism layer 1148 are separated by air, this can be achieved by providing a separate opaque boundary adjacent to the (external) sub-surface / edge face at the first end 1144 of the optical component. As in Fig.11AIn the first embodiment, such an opaque border may be included as an alternative or in addition to providing a surface coating (or equivalent), as further described below. For example, the border may include a sheet having light absorbing, diffuse reflecting / scattering and / or attenuating properties, or may include a sheet having a coating or film having light absorbing, diffuse reflecting / scattering and / or attenuating properties.

[0117] By extending the light absorbing, attenuating or diffusely reflecting / scattering subsurface / edge face to include the area above the prisms of the light redirecting prism layer 1148, the light corresponding to the first sunlight S1 is suppressed. Fig. 11B As shown, the first sunlight S1 ray directly incident on the outer sub-surface / edge face of the light redirecting prism layer 1148 at the inclined surface 1143 of the prism (at the top) is absorbed, attenuated or scattered as shown by the arrows.

[0118] exist Fig.11A and 11B In embodiments, the optical component is a light redirecting prism layer 1048 as disclosed herein. As will be appreciated by the skilled artisan, in other embodiments, the optical component may include a waveguide pupil expander 1140 (e.g., without a light redirecting layer thereon). In this case, the sub-surface / edge face at the first end of the waveguide pupil expander 1140 will be arranged for light absorption, attenuation, or diffuse reflection / scattering. In further embodiments, the optical component may include a combination of a waveguide pupil expander 1140 and a light redirecting layer 1148 thereon. In this case, the sub-surface / edge face at the first end of both the waveguide pupil expander 1150 and the light redirecting prism layer 1148 will be arranged for light absorption, attenuation, or diffuse reflection / scattering. Such embodiments may be suitable for a variety of applications in which features of the optical component, such as the louver structure 1106, allow sunlight to be incident directly or indirectly on the sub-surface / edge face at the first end 1144 of the waveguide pupil expander 1140.

[0119] Those skilled in the art will appreciate that in some other arrangements, two or more sub-surfaces forming respective edge faces of an optical component are arranged to absorb, attenuate or diffusely reflect / scatter light. Fig.11A and 11B The waveguide pupil expander has edge surfaces at its first and second ends 1144, 1145 (parallel to the longitudinal dimension of the louver - at Figure 7 1140 and 1141. The x-dimension is shown in FIG. 1140 and / or its edge face (parallel to the dimension of the louver array—in FIG. 1141 ) at one or both of the first and second sides 1146, 1147. Figure 7 The y-dimension (shown as the y-dimension) can be arranged to absorb, attenuate, or diffusely scatter / reflect light as described herein.

[0120] As a supplement or alternative to the reflection suppression measures of the first or second embodiments, an opaque border may be provided around all sub-surfaces / edge surfaces of the optical component. Specifically, an opaque frame may be provided, surrounding the sides 1046, 1147 and ends 1144, 1145 of the waveguide pupil expander 1040, the light redirecting prism layer 1048 and the louver structure 1106 thereon. Such an opaque border may further prevent sunlight from entering the optical component through the sub-surface / edge surface of the optical component, and may also suppress internal reflections of sunlight incident on the sub-surface / edge surface of the optical component. The opaque border may include a sheet having light absorption, diffuse reflection / scattering and / or attenuation properties, or may include a sheet having a coating or film having light absorption, diffuse reflection / scattering and / or attenuation properties. For example, the opaque border may be processed (e.g., etched or roughened) to diffusely reflect / scatter and / or attenuate the light incident thereon.

[0121] Fig. 9 is equivalent to Figure 8 Polar plot of different solar elevation angles, showing the Fig. 11B A second embodiment of a waveguide pupil expander is shown for simulation of sunlight glare in the center of the viewing area of ​​an automotive head-up display.

[0122] Fig. 9 A central generally circular region is shown within which the polar positions of the sun are found to produce a solar reflection SR at the center of the viewing area. Specifically, at all polar positions within the depicted generally circular region, the solar reflection is a diffuse, low intensity reflection (e.g., below an intensity threshold). Thus, the first, second, and third types of reflection described above are diffuse and indistinguishable from one another in the viewing area. Thus, the simulation surprisingly found that the solar glare in the viewing area was significantly reduced due to the measures and techniques described herein.

[0123] Combiner shape compensation

[0124] An advantage of projecting a hologram to the eyebox is that optical compensation can be encoded in the hologram (e.g. European Patent 2936252, which is incorporated herein by reference). The present disclosure is compatible with holograms that compensate for the complex curvature of an optical combiner used as part of a projection system. In some embodiments, the optical combiner is a windshield of a vehicle. Full details of this approach are provided in European Patent 2936252 and are not repeated here because the detailed features of these systems and methods are not essential to the novel teachings of this disclosure herein and are merely examples of configurations that benefit from the teachings of the present disclosure.

[0125] Controls

[0126] The present disclosure is also compatible with an optical configuration including a control device (e.g., an optical shutter device) to control the delivery of light from the optical channel hologram to the observer. The holographic projector may also include a control device arranged to control the delivery of the angular channel to the eye box position. British patent application 2108456.1, filed on June 14, 2021 and incorporated herein by reference, discloses at least one waveguide pupil expander and a control device. The reader will understand from at least this prior disclosure that the optical configuration of the control device is substantially based on the user's eye box position and is compatible with any hologram calculation method for implementing the optical channel described herein. It can be said that the control device is an optical shutter or aperture device. The optical shutter device may include a 1D array aperture or window, each of which can be independently switched between a light-transmitting and a light-impermeable state to control the delivery of the hologram optical channel and its replica to the eye box. Each aperture or window may include a plurality of liquid crystal cells or pixels.

[0127] Additional Features

[0128] The methods and processes described herein may be embodied on a computer-readable medium. The term "computer-readable medium" includes media arranged to store data temporarily or permanently, such as random access memory (RAM), read-only memory (ROM), buffer memory, flash memory, and cache memory. The term "computer-readable medium" should also be considered to include any medium or combination of media capable of storing instructions for execution by a machine, so that when the instructions are executed by one or more processors, the machine performs, in whole or in part, any one or more of the methods described herein.

[0129] The term "computer-readable medium" also encompasses cloud-based storage systems. The term "computer-readable medium" includes, but is not limited to, one or more tangible and non-transitory data storage repositories (e.g., data volumes) in the example form of solid-state memory chips, optical disks, magnetic disks, or any suitable combination thereof. In some example embodiments, instructions for execution may be conveyed by a carrier medium. Examples of such carrier media include transient media (e.g., propagated signals conveying instructions).

[0130] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope of the appended claims. The present disclosure covers all modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. A display system, comprising: an optical component having first and second major surfaces and one or more minor surfaces, wherein each minor surface forms an edge face of the optical component, wherein one or more of the first and second major surfaces are reflective; a light control layer disposed on the first major surface of the optical component, wherein the light control layer includes a louver structure including an array of louvers arranged to suppress reflection of sunlight received on an optical path to the first major surface; Therein, at least one edge face of the optical component is arranged to suppress specular reflection of light incident thereon.

2. The display system according to claim 1, wherein: The at least one edge face of the optical component is arranged to attenuate and / or diffusely reflect light incident thereon.

3. The display system according to claim 2, wherein: At least one edge surface of the optical component comprises: Materials, elements or components that attenuate light, and / or A material, element or component that diffusely reflects or scatters light.

4. The display system according to claim 2 or 3, wherein: At least one edge face of the optical component is coated with a light attenuating coating, such as an opaque coating.

5. A display system as claimed in claim 2, 3 or 4, wherein: At least one edge face of the optical component is processed, such as by etching, so as to attenuate or diffusely reflect light incident thereon.

6. The display system according to any one of claims 2 to 5, wherein: At least one edge face of the optical component is arranged to diffusely reflect / scatter light with a hemispherical diffuse reflectivity of less than 10%, optionally less than 4%.

7. A display system as claimed in any one of the preceding claims, wherein: At least one edge face of the optical component is arranged to absorb light incident thereon.

8. The display system according to claim 7, wherein: At least one edge face of the optical component comprises a light absorbing material, optionally wherein at least one edge face is coated with a light absorbing coating, such as a black coating.

9. A display system as claimed in any one of the preceding claims, wherein: The first major surface of the optical component includes an exit surface for outputting image light of the display system to an observation area.

10. The display system according to claim 9, wherein: The optical component includes a light redirecting element for controlling the direction of output image light from the exit surface.

11. The display system according to claim 10, wherein: The light redirecting element comprises a first major surface and one or more minor surfaces, each minor surface forming an edge face thereof, wherein at least one edge face of the light redirecting element is arranged to suppress specular reflection of light incident thereon.

12. The display system according to claim 11, wherein: The first major surface of the light redirecting element is an interface with the exit surface of the optical component.

13. The display system according to claim 10, 11 or 12, wherein: The light redirecting element is a light redirecting film, such as a film including an array of prisms having an inclined surface opposite the exit surface of the optical component.

14. The display system according to any one of claims 10 to 13, wherein: At least one edge face of the light redirecting element is arranged to absorb light incident thereon, or to attenuate or diffusely reflect / scatter light incident thereon.

15. A display system as claimed in any preceding claim, comprising an opaque border or frame surrounding one or more sub-surfaces of the optical component.

16. A display system as claimed in any preceding claim, wherein: The optical component comprises a waveguide pupil expander, and the first and second major surfaces are relative / parallel reflective surfaces arranged to provide internal reflection and waveguiding of image light therebetween, optionally wherein the first major surface comprises a partially reflective-partially transmissive surface forming an exit surface of the waveguide pupil expander.

17. The display system according to claim 16, wherein: At least one edge surface arranged to suppress specular reflection of light incident thereon includes an edge surface at the first end of the waveguide pupil expander, or an edge surface of a light redirecting element on the exit surface of the waveguide pupil expander adjacent to its first end, wherein the pupil expansion is from the first end to the second end of the waveguide pupil expander.

18. A waveguide pupil expander for use in a display system as claimed in claim 16 or 17.

Images