Display system and light control element thereof

Abstract

A display system and a waveguide pupil expander are described. The display system includes an optical component having first and second major surfaces and one or more minor surfaces, each of which defines an edge surface of the optical component. One or more of the first and second major surfaces of the optical component are reflective. A light control layer is disposed on the first major surface of the optical component. The light control layer includes a louver structure including an array of louvers arranged to suppress reflections of sunlight received on an optical path to the first major surface. At least one edge surface of the optical component is arranged to suppress specular reflections 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 a waveguide pupil dilator and a method of pupil dilation using a waveguide. The present disclosure further 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 dilator including a light control element. Some embodiments relate to image generation units and head-up displays, such as automotive head-up displays (HUDs). [Background technology]

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

[0003] Computer-generated holography can numerically simulate interference processes. Computer-generated holograms can be calculated using techniques based on mathematical transforms, such as the Fresnel transform or the Fourier transform. These types of holograms are sometimes called Fresnel / Fourier transform holograms, or simply Fresnel / Fourier holograms. Fourier holograms can be viewed as a Fourier domain / planar representation of an object, or a frequency domain / planar representation of an object. Computer-generated holograms can be calculated, for example, using 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 incident light. Light modulation can be achieved using, for example, electrically addressable liquid crystals, optically addressable liquid crystals, or micromirrors.

[0005] Spatial light modulators are typically composed of multiple individually addressable pixels, also called cells or elements. The light modulation scheme may be binary, multilevel, or continuous. Alternatively, the device may be continuous (i.e., not pixelated), and thus the light modulation may be continuous across the device. Spatial light modulators may be reflective, meaning that modulated light is output through reflection. Spatial light modulators may also be transmissive, meaning that modulated light is output through transmission.

[0006] The systems described herein can be used to provide holographic projectors, which have applications in head-up displays (HUDs). Summary of the Invention

[0007] Aspects of the present disclosure are defined in the accompanying independent claims.

[0008] A display system is provided that includes an optical component having first and second major surfaces and one or more minor surfaces. Each minor surface can be said to form an edge or edge surface of the optical component. One or more of the first and second major surfaces is reflective. A light control layer is disposed on the first major surface of the optical component. The light control layer includes a louver structure. The louver structure includes an array of louvers arranged to reduce reflections of sunlight received on a light path to the first major surface. At least one edge / edge surface of the optical component is arranged to reduce specular reflections of light incident thereon.

[0009] In some embodiments, at least one edge of the optical component is arranged to attenuate and / or diffusely reflect / scatter light incident thereon. For example, the at least one edge may include a material, element, or component that attenuates and / or diffusely reflects or scatters light. Thus, light directly or indirectly incident on the at least one edge is diffusely reflected / scattered and / or attenuated to suppress light reflection. Those skilled in the art will understand that surfaces that diffusely reflect / scatter light also attenuate light. However, other techniques for attenuating incident light are possible and contemplated.

[0010] In other embodiments, at least one edge of the optical component is positioned to absorb light incident thereon. For example, at least one edge of the optical component can include a light-absorbing material or a light-absorbing element or component. In an example, at least one edge is coated with a light-absorbing coating, such as a black coating. Thus, light directly or indirectly incident on the at least one edge is absorbed, reducing light reflection.

[0011] In examples, at least one edge 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 treated, such as by etching, to attenuate and / or diffusely reflect / scatter light incident thereon.

[0012] In other examples, at least one edge of the optical component includes a boundary that is configured to diffusely reflect / scatter and / or attenuate light incident thereon. For example, the edge may include a sheet material that has diffuse light-reflecting / scattering properties, or may include a sheet material that includes a coating or film that has diffuse light-reflecting / scattering properties.

[0013] In some embodiments, a first major surface of the optical component includes an exit surface for outputting image light of the display system to a viewing zone. The optical component can include a light turning element for controlling the direction of the image light output from the exit surface. In some embodiments, the light turning element includes a first major surface and one or more minor surfaces, each defining an edge surface. The first major surface of the turning element can form an interface with the exit surface of the optical component. At least one edge surface of the light turning element can be positioned to suppress specular reflection of light incident thereon. In some examples, the light turning element is a light turning film, such as a film including an array of prisms with an angled surface opposite the major surface. In some embodiments, at least one edge of the light turning element is positioned to absorb light incident thereon, attenuate light incident thereon, or diffusely reflect / scatter light incident thereon.

[0014] In some embodiments, the display system comprises an opaque boundary or box that surrounds one or more minor surfaces that form the edge surface of the optical component, and the opaque boundary or box also serves to reduce specular reflection of light, for example by blocking, attenuating, and / or diffusely reflecting / scattering light that is directly incident on the edge surface of the optical component.

[0015] In an embodiment of the display system, the optical component includes 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 includes a partially reflective-partially transmissive surface that forms the exit surface of the waveguide pupil expander. In an example, the at least one edge surface arranged to suppress specular reflection of incident light includes an edge surface at a first end of the waveguide pupil expander, and the pupil expansion is from the first end to the second end of the waveguide pupil expander.

[0016] Also provided is a waveguide pupil expander for a display system. In an embodiment, the optical component is a waveguide pupil expander. The light control layer is disposed at an exit surface of the waveguide pupil expander, forming an output port for image light from the display system toward its display area. For example, the waveguide pupil expander can include a pair of parallel reflective surfaces arranged to internally reflect and guide the image light of the display system. The pair of parallel reflective surfaces includes a first fully reflective surface and a second partially reflective-partially transmissive surface forming an exit surface. The exit surface can be a flat surface, a reflective surface of the optical component, or both.

[0017] In this disclosure, the term "replica" is used solely to reflect that the spatially modulated light is split and 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 partial reflection / transmission by a pupil dilator. Each replica travels along a different optical path. Some embodiments of this disclosure relate to the propagation of light encoded in a hologram rather than an image, i.e., the light spatially modulated with the hologram of the image rather than the image itself. Thus, multiple replicas of a hologram are said to be formed. Those skilled in the art of holography will understand that the composite light field associated with the propagation of holographically encoded light varies with propagation distance. The use of the term "replica" here is independent of propagation distance; therefore, 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. As a result, the composite light field evolves differently along each path. That is, two composite light fields are still considered "replicas" according to this disclosure, even if they are associated with different propagation distances. provided that they originate from the same replication event or series of replication events.

[0018] According to the present disclosure, a "diffracted light field" or "diffracted light field" is a light field formed by diffraction. The diffracted 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 diffracted light field is a holographic light field or a light field that forms a holographic reconstruction of an image. The holographic light field forms a (holographic) reconstruction of an image on a reconstruction plane. The holographic light field propagating from a hologram to a reconstruction plane can be said to contain light encoded in the hologram or light within the hologram region. The diffracted light field is characterized by a diffraction angle determined by the minimum feature size of the diffracting structure and the wavelength of the light (of the diffracted light field). According to the present disclosure, a "diffracted light field" can also be said to be a light field that forms a reconstruction on a plane spatially separated from a corresponding diffracting structure. An optical system for propagating the diffracted light field from a diffracting structure to an observer is disclosed herein. The diffracted light field can form an image.

[0019] The term "hologram" refers to a recording containing amplitude or phase information about an object, or a combination thereof. The term "holographic reconstruction" refers to an 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 spatially separated from the hologram. The term "reconstruction field" refers to the 2D region in which the holographic reconstruction is formed and perfectly focused. When a hologram is displayed on a spatial light modulator containing pixels, the reconstructed field is repeated in multiple diffraction orders, each of which is a replica of the zeroth-order reconstructed field. The zeroth-order reconstructed field is the brightest reconstructed field and therefore generally corresponds to the dominant or primary reconstructed field. Unless explicitly stated otherwise, the term "reconstruction field" is interpreted to refer to the zeroth-order reconstructed field. The term "reconstruction plane" refers to the plane in space that contains all reconstructed fields. The terms "image," "reconstructed image," and "image region" refer to the region of the reconstructed field illuminated by the light of the holographic reconstruction. In some embodiments, the "image" is composed of individual spots, called "image spots" or, for convenience, "image pixels."

[0020] The terms "encoding," "writing," or "addressing" are used to describe the process of providing a plurality of pixels of an SLM with a plurality of control values ​​that respectively determine the modulation level of each pixel. The pixels of the SLM are said to be configured to "display" a light modulation distribution in response to receiving the plurality of control values. The SLM is therefore said to "display" a hologram, and a hologram can be thought of as an array of light modulation values ​​or levels.

[0021] It has been shown that holographic reconstructions of acceptable quality can be formed from "holograms" that contain only phase information related to the Fourier transform of the original object. Such holographic recordings are sometimes referred to as phase-only holograms. Although the embodiments relate to phase-only holograms, the present disclosure is equally applicable to amplitude-only holography.

[0022] The present disclosure is equally applicable to forming a holographic reconstruction using amplitude and phase information associated with the Fourier transform of the original object. In some embodiments, this is achieved by complex modulation using a so-called full complex hologram, which contains both amplitude and phase information associated with the original object. Such holograms are sometimes referred to as full complex holograms because the value (gray level) assigned to each pixel of the hologram has an amplitude and a phase component. The value (gray level) assigned to each pixel can be represented as a complex number having both an amplitude and a phase component. In some embodiments, a full complex computer-generated hologram is calculated.

[0023] The phase of a pixel of a computer-generated hologram or spatial light modulator, referred to as a phase value, phase component, phase information, or simply phase, is sometimes referred to as an abbreviation for "phase delay." That is, the described phase value is actually a number (e.g., ranging from 0 to 2π) representing the amount of phase delay provided by that pixel. For example, a spatial light modulator pixel described as having a phase value of π / 2 delays the phase of received light by π / 2 radians. In some embodiments, each pixel of a spatial light modulator is operable at one of multiple possible modulation values ​​(e.g., phase delay values). The term "gray level" is sometimes used to refer to multiple available modulation levels. For example, the term "gray level" is sometimes used for convenience to refer to multiple phase levels available in a phase-only modulator, even though the different phase levels do not provide different shades of gray. The term "gray level" is sometimes used for convenience to refer to multiple complex modulation levels available in a complex modulator.

[0024] A hologram therefore consists of an array of gray levels, i.e., an array of optical modulation values, such as an array of phase delay values ​​or complex modulation values. A hologram can also be considered a diffraction pattern, since it is a pattern displayed on a spatial light modulator and causes diffraction when illuminated with light of a wavelength comparable to (but usually shorter than) the pixel pitch of the spatial light modulator. Here, we refer to combining holograms with other diffraction patterns, such as diffraction patterns that act as lenses or gratings. For example, a diffraction pattern acting as a grating can be combined with a hologram to transform the reconstruction field on the reconstruction plane, or a diffraction pattern acting as a lens can be combined with a hologram to focus the holographic reconstruction on the reconstruction plane in the near field.

[0025] In the detailed description that follows, different embodiments and groups of embodiments may be disclosed separately, but any feature of any embodiment or group of embodiments may be combined with any other feature or combination of features of any embodiment or group of embodiments, i.e., all possible combinations and permutations of features disclosed in this disclosure are contemplated. [Brief explanation of the drawings]

[0026] Specific embodiments will now be described, by way of example only, with reference to the following figures:

[0027] [Figure 1] FIG. 1 is a schematic diagram showing a reflective SLM generating a holographic reconstruction on a screen. [Figure 2] FIG. 2 shows an image for projection that includes cross sections of eight image regions / components V1-V8 and corresponding hologram channels H1-H8. [Figure 3] Figure 3 shows a hologram displayed on an LCOS that directs light to multiple discrete areas. [Figure 4]FIG. 4 shows a system including a display device that displays the holograms calculated as shown in FIGS. [Figure 5] FIG. 5 shows a perspective view of a first example two-dimensional pupil expander including two replicators. [Figure 6] 6A and 6B are schematic diagrams of an automotive head-up display system showing areas where sunlight glare can occur. [Figure 7] FIG. 7 is a schematic diagram of a light control layer formed on a transmissive surface of a pupil expander in an automotive head-up display system. [Figure 8] FIG. 8 is a polar diagram showing simulations of solar glare from different solar elevation angles at the center of the viewing area of ​​an automotive head-up display equipped with a waveguide pupil dilator according to a comparative example. [Figure 9] FIG. 9 is a polar plot corresponding to FIG. 8 showing simulated solar glare from different solar elevation angles at the center of the viewing area of ​​an automotive head-up display with a waveguide pupil dilator with reflection suppression according to an embodiment. [Figure 10] FIG. 10 is a schematic diagram of a waveguide pupil dilator for a display system showing an example of sunlight being received and reflected towards the display area. [Figure 11] 11A and 11B are schematic diagrams of the waveguide pupil expander of FIG. 10 with reflection suppression in accordance with an embodiment of the present disclosure.

[0028] The same reference numbers are used throughout the drawings to refer to the same or similar parts. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention is not limited to the embodiments described below, but rather encompasses the full scope of the appended claims, i.e., the present invention may be embodied in different forms and should not be construed as being limited to the embodiments set forth for illustrative purposes.

[0030] Singular terms may include plurals unless otherwise specified.

[0031] A structure described as being formed on top / bottom of, or above / below, another structure is to be interpreted as including cases where the structures contact each other and even cases where a third structure is disposed between them.

[0032] An optical component consists of major and minor surfaces. For example, in the case of a (bulk optics) waveguide pupil expander, the major surfaces are formed by first and second longitudinally extending parallel reflective surfaces for guiding light between them, while the other surfaces, i.e., the edge surfaces of the side and end walls, form minor surfaces, usually in planes perpendicular to the plane of the major surfaces.

[0033] When describing temporal relationships, for example, when the temporal order of events is described as "after," "succeeding," "next," "before," etc., the disclosure should be construed as including sequential and non-sequential events unless otherwise specified. For example, unless words such as "just," "immediately," "directly," etc. are used, the description should be construed as including non-sequential cases.

[0034] In this specification, terms such as "first" and "second" may be used to describe various elements, but these elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of the appended claims.

[0035] Features of different embodiments may be partially or wholly combined or combined with one another and may interoperate with one another in various ways, and some embodiments may execute independently of one another or may execute together in an interdependent manner.

[0036] In the present disclosure, the term "substantially" when applied to a structural unit of an apparatus may be interpreted as meaning that the technical characteristics of the structural unit are produced within the technical limits of the method used to manufacture it.

[0037] Conventional optical configuration for holographic projection FIG. 1 illustrates an embodiment in which a computer-generated hologram is encoded onto a single spatial light modulator. The computer-generated hologram is the Fourier transform of the object for reconstruction. Therefore, the hologram can be said to be a Fourier-domain, 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 onto the spatial light modulator, and a holographic reconstruction is formed at a replay field, e.g., a light-receiving surface such as a screen or diffuser.

[0038] A light source 110, e.g., a laser or laser diode, is positioned to illuminate the SLM 140 through a collimating lens 111. The collimating lens directs a nearly planar wavefront of light into the SLM. In FIG. 1, the wavefront direction is not perpendicular (e.g., 2 or 3 degrees away from true orthogonal to the plane of the transparent layer). However, in other embodiments, a nearly planar wavefront is provided at normal incidence, and a beam splitter arrangement is used to separate the input and output optical paths. In the embodiment shown in FIG. 1, light from the light source is arranged to reflect off the back mirror of the SLM and interact with the light modulating layer to form an output wavefront 112. The output wavefront 112 is applied to an optical system including a Fourier transform lens 120 focused onto a screen 125. More specifically, the Fourier transform lens 120 receives the modulated beam of light from the SLM 140 and performs a frequency-space transformation to generate a holographic reconstruction on the screen 125.

[0039] Specifically, in this type of holography, each pixel of the hologram contributes to the overall reconstruction: there is no one-to-one correlation between a specific point on the replay field (or image pixel) and a specific light-modulating element (or hologram pixel). In other words, the modulated light leaving the light-modulating layer is distributed throughout the entire replay field.

[0040] In these embodiments, the position of the holographic reconstruction in space is determined by the refractive power (focusing power) of the Fourier transform lens. In the embodiment shown in FIG. 1 , the Fourier transform lens is a physical lens. That is, the Fourier transform lens is an optical Fourier transform lens, and the Fourier transform is performed optically. Any lens can function as a Fourier transform lens, but the performance of the lens limits the accuracy of the performed Fourier transform. Those skilled in the art understand how to perform an optical Fourier transform using lenses. In some embodiments of the present disclosure, the lens in the observer's eye performs the conversion from hologram to image.

[0041] Hologram Calculation In some embodiments, the computer-generated hologram is a Fourier transform hologram, or simply a Fourier hologram, or a Fourier-based hologram, in which an image is reconstructed in the far field using the Fourier transform properties of a positive lens. A Fourier hologram is calculated by Fourier transforming the desired light field at the reconstruction plane back to the lens plane. A computer-generated Fourier hologram can be calculated using the Fourier transform. The embodiments relate, by way of example only, to Fourier holography and Gerchberg-Saxton-type algorithms. This disclosure is equally applicable to Fresnel holography and Fresnel holograms, which can be calculated in a similar manner. In some embodiments, the hologram is a phase or phase-only hologram. However, this disclosure is also applicable to holograms calculated by other techniques, such as those based on point cloud methods.

[0042] In some embodiments, the hologram engine is configured to exclude from the hologram calculation the contribution of light blocked by the display system's limiting aperture. UK Patent Application No. 2101666.2, filed February 5, 2021, and incorporated herein by reference, discloses a first hologram calculation method that uses eye tracking and ray tracing to identify subareas of a display device for the calculation of point cloud holograms that eliminate ghost images. The subareas of the display device correspond to the apertures of the present disclosure and are used to exclude light paths from the hologram calculation. UK Patent Application No. 2112213.0, filed August 26, 2021, and incorporated herein by reference, discloses a second method based on a modified Gerchberg-Saxton algorithm, including cropping the light field according to the pupil of the optical system during hologram calculation. Cropping the light field corresponds to determining the limiting aperture of the present disclosure. UK Patent Application 2118911.3, filed December 23, 2021, and incorporated herein by reference, discloses a third method for calculating a hologram, which includes determining an area of ​​a so-called extended modulator formed by a hologram replicator. According to this disclosure, the extended modulator area is also an aperture.

[0043] In some embodiments, a real-time engine is provided that is configured to receive image data and use an algorithm to calculate a hologram in real time. In some embodiments, the image data is a video that includes a series of image frames. In other embodiments, the hologram is pre-calculated, stored in computer memory, and recalled for display on the SLM as needed. That is, in some embodiments, a repository of pre-defined holograms is provided.

[0044] Wide field of view and / or eyebox using small display devices Broadly, this disclosure relates to image projection. This disclosure relates to an image projector including a method of image projection and a display device. This disclosure also relates to a projection system including an image projector and a display system. In this projection system, the image projector projects or relays light from a display device to the display system. This disclosure is equally applicable to monocular and binocular display systems. The display system can include a viewer's eye or multiple eyes. The display system includes an optical element having optical power (e.g., a lens in a human eye) and a display surface (e.g., a retina in a human eye). The projector is sometimes 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 image is formed on the display surface or perceived by the viewer. In some embodiments, the image is a virtual image, and the display surface is sometimes referred to as a virtual image surface. In other examples, the image is a real image formed by holographic reconstruction, and the image is projected or relayed to the display surface. In these other examples, spatially modulated light of an intermediate holographic reconstruction formed in free space or on a screen or other light-receiving surface between the display device and the viewer is propagated to the viewer. In both cases, the image is formed by illuminating a diffractive pattern (such as a hologram or kinoform) that is displayed on a display device.

[0045] A display device is made up of pixels. The pixels of a display can display a diffraction pattern or structure that diffracts light. The diffracted light forms an image at a plane spatially separated from the display device. According to well-known optics, the magnitude of the maximum diffraction angle depends on the size of the pixel and other factors such as the wavelength of the light.

[0046] In embodiments, the display device is a spatial light modulator, such as a liquid crystal on silicon ("LCOS") spatial light modulator (SLM). Light propagates from the LCOS toward a viewing entity / system, such as a camera or an eye, over a range of diffraction angles (e.g., from zero to a maximum diffraction angle). In some embodiments, magnification techniques can be used to expand the range of available diffraction angles beyond the conventional maximum diffraction angle of the LCOS.

[0047] In some embodiments, the hologram itself (light) is transmitted to the eye. For example, the hologram's spatially modulated light (not yet fully converted into a holographic reconstruction, i.e., an image), which may informally be referred to as "encoded" by the hologram, is transmitted directly to the viewer's eye. The viewer may perceive a real or virtual image. In these embodiments, no intermediate holographic reconstruction / image is formed between the display device and the viewer. In these embodiments, the lens of the eye is sometimes said to perform the hologram-to-image transformation or conversion. A projection system or light engine can be configured so that the viewer effectively views the display device directly.

[0048] Throughout the specification, references are made to a "light field," but this is a "complex light field." The term "light field" simply denotes a pattern of light that has finite size in at least two orthogonal spatial directions, e.g., x and y. The term "complex" is used herein simply to indicate that the light at each point in the light field is defined by an amplitude and a phase value and may therefore be represented by a complex number or pair of values. For purposes of hologram calculations, a complex light field is 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.

[0049] According to well-known optical principles, the range of angles of light propagating from a display device that can be observed by the eye or other viewing object / system varies depending on the distance between the display device and the viewing object. For example, at a viewing distance of one meter, only a small portion of the angles from an LCOS can pass through the eye's pupil and form an image on the retina at a particular eye position. The range of angles of light rays propagating from the display device that can pass through the eye's pupil and form an image on the retina determines the portion of the image that is "visible" to the viewer. In other words, not all parts of the image are visible from any one point on the viewing surface (e.g., any one eye position within a viewing window such as the eyebox).

[0050] In some embodiments, the image perceived by the viewer is a virtual image displayed upstream of the display device. That is, the viewer perceives the image as being farther away than the display device. Conceptually, the viewer can be thought of as viewing the virtual image through a very small "display device-sized window," such as 1 cm in diameter, at a relatively large distance, e.g., 1 m. The user also sees the display device-sized window through a very small eye pupil. Thus, the field of view is narrowed, and the specific angular range that can be seen is highly dependent on the eye position at any given time.

[0051] Pupil expanders address the problem of how to expand the angular range of light rays propagating from a display device and successfully pass through the eye's pupil to form an image. Display devices are generally (relatively) small and have (relatively) large projection distances. In some embodiments, the projection distance is at least one order of magnitude, e.g., at least two orders of magnitude, larger than the diameter or width of the display device's entrance pupil and / or aperture (i.e., the size of the pixel array).

[0052] The use of a pupil expander expands the viewing zone (i.e., the user's eyebox) laterally, allowing for eye movement while still allowing the user to see the image. As a skilled artisan will appreciate, in an imaging system, the viewing area (the user's eyebox) is the area in which the observer's eyes can perceive an image. The present disclosure is directed to non-infinite virtual image distances, i.e., near-field virtual images.

[0053] Traditionally, a two-dimensional pupil expander consists of one or more one-dimensional optical waveguides, each formed using a pair of opposing reflective surfaces, with output light from the surfaces forming a viewing window or eyebox. Light received from a display device (e.g., spatially modulated light from an LCOS) is replicated by the or each waveguide so that the field of view (or viewing area) is expanded in at least one dimension. In particular, the waveguides generate additional light rays or "replicas" by amplitude division of the incident wavefront, thereby expanding the viewing window.

[0054] The display device may have an active or display area that is less than 10 cm, e.g., less than 5 cm or less than 2 cm. The propagation distance between the display device and the display system may be greater than 1 m, e.g., greater than 1.5 m or greater than 2 m. The light propagation distance within the waveguide may be up to 2 m, e.g., up to 1.5 m or up to 1 m. The method can receive an image and determine a corresponding hologram of sufficient quality in less than 20 ms, e.g., less than 15 ms or less than 10 ms.

[0055] In some embodiments, described solely as examples of diffractive or holographic light fields according to the present disclosure, a hologram is configured to route light into multiple channels, each corresponding to a different portion (i.e., subarea) of an image. The channels formed by the diffractive structures are referred to herein simply as "hologram channels" to reflect that they are channels of light holographically encoded with image information. The light in each channel is said to reside in the hologram domain, rather than the image or spatial domain. In some embodiments, the hologram is a Fourier or Fourier transform hologram, and thus the hologram domain is the Fourier or frequency domain. The hologram may similarly be a Fresnel or Fresnel transform hologram. The hologram may also be a point cloud hologram. Holograms are described herein as routing light into multiple hologram channels, each corresponding to a different image subregion, to reflect that the image that can be reconstructed from the hologram has a finite size and can be arbitrarily divided into multiple image subregions. Importantly, the hologram in this example is characterized by how it distributes image content when illuminated. Specifically, the hologram divides the image content by angle. That is, each 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, the operation of this hologram is unconventional. When illuminated, the spatially modulated light formed by this special type of hologram is split into multiple hologram channels, each defined by a range (in two dimensions) of ray angles. From the foregoing, it will be understood that each hologram channel (i.e., sub-range of ray angles) that may be considered in the spatially modulated light is associated with a respective portion or sub-region of the image. That is, all information necessary to reconstruct that portion or sub-region of the image is contained within the sub-range of angles of the spatially modulated light formed from the hologram of the image.When the spatially modulated light is viewed as a whole, there is not necessarily evidence of multiple individual light channels.

[0056] Nevertheless, the hologram is identifiable. For example, if only a continuous portion or subregion of the spatially modulated light formed by the hologram is reconstructed, only a subregion of the image should be visible. If a different continuous portion or subregion of the spatially modulated light is reconstructed, a different subregion of the image should be visible. A further distinguishing feature of this type of hologram is that the cross-sectional shape of the hologram channel substantially corresponds to (i.e., is substantially the same as) the shape of the entrance pupil, although the sizes may differ, at least in the correct plane from which the hologram was calculated. Each light / hologram channel propagates from the hologram at a different angle or range of angles. These are exemplary methods for characterizing or identifying this type of hologram, but other methods may also be used. In summary, the holograms disclosed herein are characterized and identifiable by how the image content is distributed within the light encoded by the hologram. Again, for the avoidance of doubt, references herein to holograms configured to direct light or angularly split an image into multiple holographic channels are made by way of example only, and the present disclosure is equally applicable to any type of holographic light field, as well as any type of diffracted light field or pupil dilation of a diffracted light field.

[0057] The system can be provided in a compact and streamlined physical form, making it suitable for a variety of practical applications where space is limited and real estate is at a premium, such as implementation in head-up displays (HUDs) in vehicles and automobiles.

[0058] According to the present disclosure, pupil dilation is provided for diffracted light or diffracted light comprising diverging ray bundles. The diffracted light field is defined by a "light cone." Thus, the size of the diffracted light field (defined on a two-dimensional plane) increases with the propagation distance from the corresponding diffractive structure (i.e., display device). The pupil dilator can be said to replicate a hologram or form at least one replica of a hologram, imparting that the light delivered to the viewer is spatially modulated according to the hologram.

[0059] In some embodiments, two one-dimensional waveguide pupil expanders are provided, each positioned to effectively expand the size of the system's exit pupil by forming multiple replicas or copies of the spatial light modulator's exit pupil (or the light at the exit pupil). An exit pupil can be understood to be the physical area from which light is output by the system. Each waveguide pupil expander can also be said to be positioned to expand the size of the system's exit pupil. Each waveguide pupil expander can also be said to be positioned to expand / increase the size of the eyebox where an observer's eye can be positioned to see / receive the light output by the system.

[0060] Light channeling in the holographic regime. Holograms formed according to some embodiments angularly split the image content to provide multiple hologram channels that can have cross-sectional shapes defined by the aperture of the optical system. The hologram is calculated to provide this channeling of the diffracted light field. In some embodiments, this is achieved during hologram calculation by taking into account the aperture (virtual or real) of the optical system, as described above.

[0061] 2 and 3 show examples of this type of hologram that can be used in conjunction with the pupil dilation devices disclosed herein, but this example does not limit the invention.

[0062] FIG. 2 illustrates a projection image 252 containing eight image regions / components V1 through V8. While FIG. 2 shows eight image components as an example, image 252 can be divided into any number of components. FIG. 2 also illustrates an encoded light pattern 254 (i.e., a hologram) that can reconstruct image 252, such as when transformed by lenses in an appropriate display system. Encoded light pattern 254 is composed of first through eighth sub-holograms or components H1 through H8, corresponding to the first through eighth image components / regions V1 through V8. FIG. 2 further illustrates how a hologram decomposes image content by angle. Thus, a hologram is characterized by the light channeling it performs. This is illustrated in FIG. 3. Specifically, the hologram in this example directs light into multiple discrete regions. In the illustrated example, the discrete regions are disks, but other shapes are also contemplated. The optimal disk size and shape may be related to the size and shape of the optical aperture, such as the entrance pupil of the observation system, after propagation through the waveguide.

[0063] FIG. 4 shows a system 400 including a display device for displaying the holograms calculated as shown in FIGS.

[0064] System 400 includes a display device, which in this arrangement includes an LCOS 402. LCOS 402 is positioned to display a modulation pattern (or "diffraction pattern") that includes a hologram and project the holographically encoded light toward eye 405, which includes a pupil that serves as aperture 404, a lens 409, and a retina (not shown) that serves as a viewing surface. There is a light source (not shown) positioned to illuminate LCOS 402. Lens 409 of eye 405 performs the conversion from the hologram to an image. The light source may be of any suitable type, for example, a laser light source.

[0065] The vision system 400 further comprises a waveguide 408 disposed between the LCOS 402 and the eye 405. The presence of the waveguide 408 ensures that all angular content from the LCOS 402 is received by the eye, even at the relatively long projection distances shown, because the waveguide 408 acts as a pupil expander. This method is well known and will only be briefly described here.

[0066] Briefly, the waveguide 408 shown in FIG. 4 comprises a substantially elongated structure. In this example, the waveguide 408 comprises an optical slab of refractive material, although other types of waveguides are well known and may be used. The waveguide 408 is positioned, for example, at an oblique angle, to intersect with the light cone (i.e., the diffracted light field) projected from the LCOS 402. In this example, the size, location, and position of the waveguide 408 are configured so that light from each of eight ray bundles within the light cone enters the waveguide 408 through a first planar surface of the waveguide 408 (closest to the LCOS 402) and is guided at least partially along the length of the waveguide 408 before exiting through a second planar surface (closest to the eye) substantially opposite the first surface. As will be appreciated, the second planar surface may be partially reflective and partially transmissive. In other words, as each ray of light travels within the waveguide 408 from a first plane and strikes a second plane, some of the light is transmitted out of the waveguide 408, and some is reflected off the second plane back to the first plane. The first plane is reflective, so all of the light that strikes the first plane from within the waveguide 408 is reflected off the second plane. Thus, some of the light is refracted between the two planes of the waveguide 408 before being transmitted, while other light is reflected and undergoes one or more reflections (or "bounces") between the planes of the waveguide 408 before being transmitted.

[0067] FIG. 4 shows a total of nine "reflection" points B0 through B8 along the length of waveguide 408. As shown in FIG. 2, light associated with all points (V1-V8) of the image is transmitted from the waveguide at each "reflection" from the second plane of waveguide 408; however, only light from one angular portion of the image (e.g., any light from V1 through V8) has a trajectory that allows it to reach eye 405 from each "reflection" point B0 through B8. Furthermore, light from different angular portions of the image V1 through V8 reaches eye 405 from each "reflection" point. Thus, in the example of FIG. 4, each angular channel of encoded light reaches the eye only once from waveguide 408.

[0068] Although this specification has generally discussed virtual images, in which the eye must transform received modulated light to form a perceived image, the methods and arrangements described herein can also be applied to real images.

[0069] 2D pupil dilation While the arrangement shown in Figure 4 includes a single waveguide that provides pupil dilation in one dimension, pupil dilation can be provided in multiple dimensions, such as two. Additionally, while the example of Figure 4 uses a calculated hologram to create channels of light that correspond to different portions of the image, this disclosure and the systems described below are not limited to such types of holograms.

[0070] FIG. 5A shows a perspective view of a system 500 that includes two replicators 504, 506 arranged to expand a light beam 502 in two dimensions.

[0071] In system 500 of FIG. 5A, first replicator 504 comprises a first pair of surfaces stacked parallel to one another and arranged to provide replication (or pupil dilation) similar to waveguide 408 of FIG. 4. The first pair of surfaces have similar (possibly identical) sizes and shapes and are substantially elongated in one direction. A collimated light beam 502 is directed to the input of first replicator 504. As is well known to the skilled reader, due to the process of internal reflection between the two surfaces and partial transmission of light from each of multiple output points on one of the surfaces (the top surface as shown in FIG. 5A), the light of light beam 502 is replicated in a first direction along the length of first replicator 504. Thus, a first plurality of replica light beams 508 are emitted from first replicator 504 toward second replicator 506.

[0072] The second replicator 506 comprises a second pair of surfaces stacked parallel to one another and positioned to receive each of the collimated rays of the first plurality of light beams 508 and provide replication, i.e., pupil dilation, by expanding each of those rays in a second direction substantially perpendicular to the first direction. The first pair of surfaces are similar (possibly identical) in size and shape to one another and are substantially rectangular. The second replicator is implemented in a rectangular shape so that it has a length along the first direction to receive the first plurality of light beams 508 and a length along a second, orthogonal direction to provide replication in the second direction. Through a process of internal reflection between the two surfaces and partial transmission of light from each of a plurality of output points on one of the surfaces (the top surface as shown in FIG. 5A ), the light of each ray in the first plurality of light beams 508 is replicated in the second direction. Thus, a second plurality of light beams 510 is emitted from the second replica device 506, the second plurality of light beams 510 comprising replicas of the input light beam 502 along each of the first and second directions. Thus, the second plurality of light beams 510 can be considered to comprise a two-dimensional grid or array of replica light beams.

[0073] 5A , the combination of the first and second replicators 504, 505 may be said to provide a two-dimensional replicator (or a “two-dimensional pupil dilator”). Thus, a replica light beam 510 may be emitted along a light path to an extended eyebox of a display system, such as a head-up display.

[0074] In the system of Figure 5A, the first replicator 504 is a waveguide including a pair of elongated, linear reflective surfaces stacked parallel to one another, and similarly, the second replicator 504 is a waveguide including a pair of rectangular reflective surfaces stacked parallel to one another. In other systems, the first replicator is a solid, elongated, linear waveguide and the second replicator is a solid, planar, rectangular waveguide, each including a solid, optically transparent material such as glass. In this case, the pair of parallel reflective surfaces is formed by a pair of opposing major sidewalls, each optionally including a reflective and a reflective-transmissive surface coating, familiar to the skilled reader.

[0075] FIG. 5B shows a perspective view of a system 500 including two replicators 520, 540 arranged to replicate a light beam 522 in two dimensions, the first replicator being a solid, elongated waveguide 520 and the second replicator being a solid, planar waveguide 540.

[0076] In the system of FIG. 5B, the first replicator / waveguide 520 is positioned so 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 positioned to couple light from the output port of the first replicator 520 to the input port of the second replicator 540. In the illustrated arrangement, the optical coupler is a flat / folding mirror 530 positioned to fold and rotate the optical path of the light to achieve the required optical coupling from the first replicator to the second replicator. As shown in FIG. 5B, the mirror 530 is positioned to receive light from the output port / reflective-transmissive surface 524a of the first replicator / waveguide 520, which contains a one-dimensional array of replicas extending in the first dimension. Mirror 530 is tilted at an angle that provides waveguiding and replication along its length in the second dimension to redirect the received light onto a path to an input port on the (fully) reflective surface of second replicator 540. Mirror 530 is one example of an optical element capable of redirecting light in the illustrated manner, and it will be appreciated that one or more other elements may be used instead to perform this task.

[0077] In the illustrated arrangement, the (partially) reflective-transmissive surface 524a of the first replicator 520 is adjacent to the input port of the first replicator / waveguide 520 and receives the input beam 522 at an angle for guiding and replicating along its length in the first dimension. The input port of the first replicator / waveguide 520 is therefore located at the input end of the same surface as the reflective-transmissive surface 524a. The skilled reader will appreciate that the input port of the first replicator / waveguide 520 may be located in other suitable locations.

[0078] 5B allows first replicator 520 and mirror 530 to be provided as part of a relatively thin first layer in a plane in the first and third dimensions (illustrated as the x-z plane). Notably, the size or "height" of the first planar layer in which first replicator 520 is disposed is reduced in the second dimension (illustrated as the y-dimension). Mirror 530 is configured to direct light away from the first layer / plane in which first replicator 520 is disposed (i.e., the "first planar layer") and toward a second layer / plane above and substantially parallel to the first layer / plane in which second replicator 540 is disposed (i.e., the "second planar layer"). Thus, the overall size or "height" of the system, including first and second replicators 520, 540 and mirrors 530 arranged in stacked first and second planar layers in the first and third dimensions (illustrated as the xz planes), is compact in the second dimension (illustrated as the y dimension). The skilled reader will appreciate that many variations of the arrangement of Figure 5B are possible and contemplated for implementing the present disclosure.

[0079] Glare reduction by suppressing reflections In operation, the transmission / exit surface (i.e., the expanded exit pupil) of the second replicator 506 of the two-dimensional pupil expander of FIG. 5 forms an exterior surface or “output port” through which image light is transmitted through air to the viewing eyebox region. Therefore, the transmission surface may be exposed to sunlight from the environment in which the head-up display is used. In particular, the received sunlight may cause glare to the viewer due to sunlight reflections associated with the pupil expander 506 and / or a turning film, if used in conjunction with the pupil expander 506. For example, glare may occur when sunlight is directly reflected from the exterior transmission surface or other surfaces of the pupil expander 506 at an angle that directs the sunlight along the optical path directly toward the viewing region / eyebox. This is referred to herein as “direct glare.” In another example, if the angle at which sunlight is coupled into the pupil expander 506 causes sunlight rays to follow the same optical path as the image rays within the pupil expander, or are reflected off the surface of the pupil expander and reach the viewing zone / eyebox indirectly (e.g., through an optical combiner such as an automobile windshield), glare can occur, described herein as "bell glare."

[0080] FIG. 6A illustrates the optical path of sunlight S incident on the transmission / exit surface 642 of a (bulk optic) waveguide pupil expander 640 of a head-up display (HUD) for automotive applications. In particular, sunlight S, at a relatively high elevation angle relative to the horizon, enters the exterior transmission / exit surface 642 of the pupil expander 640 through the vehicle's windshield 630. In this example, the transmission / exit surface 642 is positioned in a substantially horizontal plane within an opening in the vehicle's dashboard (not shown). Some sunlight D may be reflected directly from the pupil expander 640 (e.g., by one or more reflective layers thereof) toward the viewing area / eyebox, causing "direct glare." Other light rays V may be reflected indirectly from the pupil expander 640 (e.g., by one or more reflective layers thereof) and reflected back through the windshield 630 toward the viewing area / eyebox, causing "bell glare." Thus, light rays V may follow the same optical path as the image light output from the pupil expander 640. In either case, the glare resulting from reflected sunlight can be harmful to the viewer / driver. Figure 6B illustrates a viewing area / eyebox perspective, showing the areas of the windshield and dashboard where the viewer / driver may be subject to solar glare. Direct glare area D is seen at the exit / transmission surface of the vehicle dashboard (not shown), and viewing glare area V is seen at the vehicle windshield. Those skilled in the art will understand that the presence of glare from different locations within the illustrated areas D and V at a particular time may depend on the solar elevation angle and the display system configuration (both interior and in-situ). Light Control Layer

[0081] Therefore, the inventors propose using an optical component including a light control layer on the transmission surface of the second replicator / pupil expander, or more generally on the output port of the HUD, to reduce the risk of glare to the observer. One example of a light control layer for controlling the direction of received sunlight includes a plurality of parallel louvers formed of a light-absorbing, light-attenuating, or similar material. The inventors recognized that a one-dimensional louver array, typically in the form of a vertically elongated rectangular louver slat, can be used to control the direction or suppress reflection of sunlight that may be incident on the transmission surface / output port of the HUD due to its upward / horizontal orientation within the vehicle dashboard adjacent to the vehicle windshield. The louver orientation (e.g., sidewall angle), pitch, and shape (e.g., length, width, thickness) can be selected to transmit image light from the HUD over the desired angular range required to reach the viewing area / eyebox.

[0082] 7 illustrates a light control layer in the form of a louver structure 706 for reducing glare from reflected sunlight. The louver structure 706 includes a plurality of parallel louver / louver slats 710 arranged in a one-dimensional array in a second dimension (illustrated as the y-dimension). Thus, the length (longitudinal direction) of the louver / louver slats 710 is parallel to the first dimension (illustrated as the x-dimension) of the waveguide pupil dilator 740 and orthogonal to the second dimension. The louver slats 710 include a light-absorbing or light-attenuating (e.g., light-diffusing) material to block light rays incident thereon.

[0083] In the illustrated arrangement, the louver structure 706 is disposed on a substantially planar transmissive surface 742 that forms the output port of a second replicator / waveguide pupil expander 740, which is arranged to internally reflect and replicate image light I and provide pupil expansion in a second dimension (illustrated as the y-dimension). As shown in FIG. 7 , in use, the transmissive surface 742 of the waveguide pupil expander 740 is substantially horizontal and faces directly toward the vehicle windshield 730, which forms the optical combiner of the HUD display system. In the illustrated arrangement, the louver / louver slats 710 have a vertically oriented, linear shape with parallel rectangular sidewalls. The louver / louver slats 710 of the louver structure 706 are arranged at an acute angle θ (i.e., non-orthogonal) relative to the surface normal of the transmissive surface. The angled orientation of the louver slats 710 allows the rays of the replica of image light I formed and output at the transmissive surface 742 by the waveguide pupil dilator 740 to pass between the louver slats 710 without deviating from their required optical path through the windshield 730 to the viewing area / eyebox, as indicated by the arrows of the rays of image light I. Thus, the angle θ is the direction of the replica of image light I, and hence the direction of pupil dilation by the waveguide pupil dilator 740 (illustrated from left to right in the y dimension). In other words, the louver slats are tilted in the same direction as the propagation axis of the replica of image light I, relative to the surface normal of the transmissive surface 742.

[0084] Additionally, optional transparent structures 760 having a similar vertically linear shape as the louver slats 710 are positioned at an angle between adjacent slats 710 (e.g., having a width (or cross-section) extending between near (e.g., substantially) the bottom of one louver slat and near (e.g., substantially) the top of an adjacent louver slat) to provide mechanical robustness to the louver structures 706 and a protective cover for the transmissive surface 742. Thus, the tilt angle of the transparent structures is different from (e.g., greater than) the tilt angle θ of the louver slats. The transparent structures 760 are configured (e.g., shaped) to prevent rays I of image light output by the waveguide pupil dilator 740 from straying from their required optical paths (e.g., by refraction at their surfaces).

[0085] In the illustrated arrangement, the light control layer formed by the louver structure 706 can reduce sunlight glare to observers in the observation area / eyebox. In particular, FIG. 7 shows sunlight S1 from the sun at a first elevation angle (relative to the horizon) passing through the windshield 730 and incident on the louver structure 706. Some of the sunlight S1 (not shown) may directly impinge on the louver slats 710, where it may be absorbed or attenuated and not reach the transmissive surface 742. Additionally, some of the sunlight S1 (shown) may impinge on the transparent structure 760 between the louver slats 710, as shown. Depending on the configuration and orientation of the transparent structure 760, these sunlight S1 may be specularly reflected by one or more surfaces of the transparent structure 760 in a direction that passes through the windshield 730, resulting in sunlight S1 being reflected back to the transparent structure 760, as indicated by the arrows. 1R The reflected sunlight S2 is directed into a path away from the viewing area / eyebox. Figure 7 also shows sunlight S2 emanating from the sun at a second elevation angle higher / greater than the first elevation angle, which also passes through windshield 730 and is incident on louver structure 706. Due to the configuration and orientation of transparent structure 760, sunlight S2 is specularly reflected by one or more surfaces of transparent structure 760 in a direction towards one of the louvers 710 and is absorbed or attenuated. This causes reflected sunlight S2, which may be directed towards the viewing area / eyebox, as shown by the arrows. 2R The intensity of the signal is blocked / reduced.

[0086] Reflection of sunlight within optical components beneath a light control layer The presence of a light control layer including a louver structure disposed on a first major sunlight-receiving surface of an optical component, such as the transmissive surface of the waveguide pupil expander described above, can suppress or reduce many of the sunlight reflections that could be directed along the optical path toward the display area of ​​the display system and cause glare. However, the inventors have discovered that there are still some sources of sunlight reflections that can occur as a result of internal reflections within the optical component below the louver structure, which can be directed along the optical path through the louver structure toward the display area and cause glare. Figure 10 shows examples of sunlight reflections from these sources.

[0087] 10, a first potential source of solar reflection is a first type of sunlight S1 that is incident relatively close to the first end 1044 of the waveguide pupil dilator 1040, with the direction of pupil dilation being from the first end 1044 to the second end 1045. 1は , is received (through the windshield 1030) in a direction such that the light rays are incident on the outer minor surface (i.e., the outer edge surface) of the first end 1044 of the waveguide pupil expander 1040. In the illustrated arrangement, the waveguide pupil expander 1040 includes a light rotating layer 1046 including an array of rotating prisms (referred to herein as a "light rotating prism layer") disposed on its outer primary transmitting surface 1042. The louver structure, as described herein, consists of a one-dimensional array of air-spaced louvers / louver slats and is disposed above (on the inclined surfaces of) the prisms of the light rotating prism layer 1046. The illustrated first sunlight S1 is incident on the outer minor surface / edge surface of the first end 1044 of the light rotating prism layer 1048. As shown in FIG. 10, the first sunlight S1 is reflected from the inclined surfaces 1043 of the prisms of the light rotating prism layer 1048, and the reflected first sunlight S 1R is directed towards the display area on an optical path between a pair of louvers of louver structure 1006, as indicated by the arrow.

[0088] A second potential source of solar reflections are second and third solar rays S2 and S3, respectively, which are received in a direction such that their rays enter the louver structure 1006 (through the windshield 1030) and are transmitted to the light rotating prism layer 1048 of the waveguide pupil expander 1040. In particular, the rays of the second solar ray S2 shown are incident on the louver structure 1006 at approximately the same angle as the orientation angle θ of the louvers / louver slats. Thus, the second solar ray S2 passes between a pair of louvers (optionally through a transparent structure (not shown) between the louvers / louver slats) and enters the light rotating prism layer 1048. The second solar ray S2 shown undergoes multiple internal reflections within the light rotating prism layer 1048. In particular, the second sunlight S2 is first reflected from the internal minor / edge surface of the first end 1044 of the light rotating prism layer 1048 and then reflected from the transmitting surface 1042 of the waveguide pupil expander 1040 at the interface with the light rotating prism layer 1046. This results in the illustrated reflected second sunlight S2. 2R is directed toward the display area on an optical path between a pair of louvers of louver structure 1006, as indicated by the arrow. The third sunlight S3 shown is also incident on louver structure 1006 at approximately the same angle as the louver orientation angle θ. Thus, the third sunlight S3 passes between the pair of louvers (and optionally through a transparent structure (not shown) between the louvers / louver slats) and enters light rotating layer 1046. The third sunlight S3 shown undergoes multiple internal reflections within light rotating prism layer 1048 that are different from the internal reflections of the second sunlight S2. In particular, the third sunlight S3 is first reflected from an internal minor / edge surface at the first end 1044 of the light rotating prism layer 1048, then reflected from the interface of the transmitting surface 1042 of the waveguide pupil dilator 1040 with the light rotating prism layer 1046, then reflected back to the light rotating prism layer 1048 from the prism's angled surface 1043, and fourthly reflected from the interface of the transmitting surface 1042 of the waveguide pupil dilator 1040 with the light rotating prism layer 1046. This results in the illustrated reflected third sunlight S 2RThe second and third sunlight S2, S3 are also directed toward the viewing area on the optical path between a pair of louvers / louver slats of the louver structure 1006, as indicated by the arrows. In both cases, the angle of incidence of the second and third sunlight S2, S3 on the internal minor / edge surface at the first end 1044 of the light-rotating prism layer 1048 exceeds the critical angle, potentially causing total internal reflection. Therefore, the intensity of the reflection exhibited by the second and third sunlight S2, S3 may be high, potentially causing glare in the viewing area.

[0089] FIG. 10 also illustrates how the louver structure 1006 suppresses reflections from the fourth sunlight S4. 。 In this example, fourth sunlight S4 enters louver structure 1006 at a location away from first end 1044 of waveguide pupil expander 1040 and is transmitted through transmissive surface 1042 to light rotating prism layer 1048 of waveguide pupil expander 1040. In particular, the light of fourth sunlight S4 is shown entering louver structure 1006 at an angle substantially the same as the orientation angle θ of the louvers / louver slats. Thus, fourth sunlight S4 passes between a pair of louvers / louver slats (optionally through a transparent structure (not shown) between the louvers) and enters light rotating prism layer 1048. Because the fourth sunlight S4 enters the louver structure 1006 farther from the first end 1044 than the second sunlight S2 and S3, it only undergoes a single reflection from the transmitting surface 1042 of the waveguide pupil expander 1040 at the interface with the light-rotating prism layer 1046 before exiting the optical component between the pair of louvers / louver slats. However, as a result of the louver arrangement, the fourth sunlight S4 is directed toward the angled sidewall of one of the pair of louvers / louver slats, where it is absorbed or attenuated. Furthermore, the reflection from one sidewall of the pair of louvers / louver slats is reflected back to the other sidewall of the pair of louvers / louver slats, thereby further absorbing or attenuating the light. As a result, the reflection of the fourth sunlight S4 is suppressed, and it is not directed toward the viewing area in a way that would cause glare.

[0090] As one skilled in the art will appreciate, the above first, second, third, and fourth sunlight examples depend on the elevation angle of the sun relative to the horizon (or, conversely, its azimuth angle relative to vertical) and other factors related to the optical components present therein (e.g., the shape of the windshield 1030 and the position and orientation angle of its transmissive surface 1042). Thus, the presence of these sunlight rays depends on the time of day, the orientation of the optical components relative to the sun, etc.

[0091] FIG. 8 is a polar plot of different sun elevation angles at the center of the display area of ​​an automotive head-up display with a comparative example waveguide pupil expander, illustrating simulated solar glare. By convention, the origin (center) of the polar plot corresponds to the sun at a zenith angle of 0° (i.e., a 90° elevation angle relative to the horizon), i.e., perpendicular / directly above the HUD, and the concentric circles represent decreasing elevation angles at each position relative to the HUD (shown in 10° intervals from a 10° zenith angle to a 90° zenith angle on the outer circle). As will be appreciated by those skilled in the art, glare occurring at the center of the display area (i.e., the eyebox) is generally representative of the entire eyebox. In the comparative example, simulations were performed based on an example waveguide pupil expander with a light-redirecting prism layer and a louver structure, as shown in FIG. 10.

[0092] FIG. 8 shows elliptical regions surrounding the polar position of the sun that are known to cause intense solar glare (e.g., above a threshold intensity) in the center of the field of view. The first, second, and third elliptical regions are shown as described above with reference to FIG. 、 First, second, and third solar rays S1, S 2、 and the reflection S of S3 1R , S 2R , and S 3R In the simulation, the corresponding elliptical area S 1R , S 2R , and S 3RIt has been shown that the intensity of solar glare due to these types of reflections within can be problematic for viewers such as vehicle drivers and other similar applications where the direction and elevation angle of received sunlight changes dynamically over time.

[0093] Technology to reduce sunlight reflection under the light control layer The inventors herein propose solutions to address the problem of glare from reflected sunlight due to internal reflection within optical components below the louver structure, as described above. Those skilled in the art will appreciate that these solutions are equally applicable to optical components in display systems that do not include louver structures.

[0094] FIG. 11A illustrates a first embodiment. According to the first embodiment, the minor surfaces of the optical component are arranged to absorb, attenuate, and / or diffusely scatter / reflect light. In the illustrated embodiment, the optical component is a light-turning prism layer 1148. FIG. 11A also illustrates that the light-turning prism layer 1148 is disposed on the waveguide pupil dilator 1140, and the louver structure 1106 is disposed on the light-turning prism layer 1148, as described above with reference to FIG. 10. The minor surfaces of the optical component are parallel to the longitudinal dimension of the louver slats. In particular, the minor surface that absorbs / attenuates / diffusely reflects light is the edge surface of the first end 1144 of the light-turning prism layer 1148 (the direction of pupil dilation is from the first end 1144 to the second end 1145). For example, the minor surfaces of the prisms at the first end 1144 of the light turning prism layer 1148 may be coated with a light-absorbing, diffusely reflecting / scattering, and / or attenuating coating. In one example, the coating may be black paint applied to the outer minor / edge surfaces. In another example, the minor surfaces of the prisms at the first end 1144 of the light turning prism layer 1148 may be treated (e.g., etched) or provided with a coating or film that diffusely reflects / scatters light incident thereon. In examples where the minor surfaces diffusely reflect or scatter incident light, the reflected light is also attenuated. The inventors suggest a hemispherical diffuse reflectance of less than 10%, optionally less than 4%. This may be achieved by a combination of a light-absorbing coating, such as black paint, and a surface treatment (e.g., etching) that provides surface roughness to diffusely reflect incident light. Those skilled in the art will recognize that various alternatives for coating or treating the minor / edge surfaces are possible, including arrangements that include other types of materials, elements, or components that absorb, attenuate, and / or diffusely reflect / scatter light incident thereon.

[0095] By providing light-absorbing, attenuating, or diffusely reflecting / scattering minor / edge surfaces at the first ends 1144 of the prisms of the light-turning prism layer 1148, light rays corresponding to the second and third sunlight S2 and S3 are suppressed. In particular, as shown in FIG. 11A , the light rays of the first and second sunlight S2 and S3 incident on the louver structure 1106 between the louver pairs directly or indirectly strike the internal minor / edge surfaces of the first ends 1144, resulting in absorption, attenuation, and / or diffuse reflection, as indicated by the arrows. Thus, when the light rays of the second and third sunlight S2 and S3 strike the minor / edge surfaces of the first ends 1144, the intensity of the totally reflected light decreases when the angle of the prisms of the light-turning prism layer 1148 exceeds the critical angle. When light is diffusely reflected / scattered, the proportion of light from the second and third solar rays S2 and S3 that traverses the optical path to the observation area is reduced, thereby reducing the risk of glare to the observer.

[0096] FIG. 11B illustrates a second embodiment substantially similar to the first embodiment. However, in the second embodiment, the light-absorbing / attenuating / diffuse-reflective minor surface extends above the prisms of the light-turning prism layer 1148 at the first end 1144 (e.g., to the region between the prisms and the louver structure). If the angled surfaces of adjacent prisms in the light-turning prism layer 1148 are separated by air, this can be achieved by providing a separate opaque boundary adjacent to the (external) minor / edge surface at the first end 1144 of the optical component. Such an opaque boundary can be included instead of, or in addition to, a surface coating (or equivalent) as in the first embodiment of FIG. 11A, as described further below. For example, the boundary may include a sheet material having light-absorbing, diffusely reflective / scattering, and / or attenuating properties, or a sheet material including a coating or film having light-absorbing, diffusely reflective / scattering, and / or attenuating properties.

[0097] Light rays corresponding to the first sunlight S1 are suppressed by extending the light-absorbing, attenuating, or diffusely reflecting / scattering secondary / edge surfaces to the top regions of the prisms of the light-turning prism layer 1148. In particular, as shown in FIG. 11B, the rays of the first sunlight S1 that are directly incident on the outer secondary / edge surfaces of the light-turning prism layer 1148 at the inclined surfaces 1143 (top) of the prisms are absorbed, attenuated, or scattered as indicated by the arrows.

[0098] In the embodiment of Figures 11A and 11B, the optical component is a light turning prism layer 1048, as disclosed herein. As will be appreciated by those skilled in the art, in other embodiments, the optical component can include a waveguide pupil expander 1140 (e.g., without a light turning layer thereon). In this case, a minor / edge surface at the first end of the waveguide pupil expander 1140 is positioned to absorb, attenuate, or diffusely reflect / scatter light. In yet other embodiments, the optical component can include a combination of a waveguide pupil expander 1140 with a light turning layer 1148 thereon. In this case, a minor / edge surface at the first end of both the waveguide pupil expander 1150 and the light turning prism layer 1148 is positioned to absorb, attenuate, or diffusely reflect / scatter light. Such embodiments may be suitable for applications where features of the optical component, such as the louver structure 1106, allow sunlight to be incident directly or indirectly on a minor / edge surface at the first end 1144 of the waveguide pupil expander 1140.

[0099] Those skilled in the art will appreciate that in some other arrangements, two or more small surfaces forming each edge surface of an optical component are arranged to absorb, attenuate, or diffusely reflect / scatter light. For example, the edge surfaces of the first and second ends 1144, 1145 (parallel to the longitudinal dimension of the louvers, shown as the x-dimension in FIG. 7) and / or one or both of the edge surfaces of the first and second sides 1146, 1147 (parallel to the dimension of the array of louvers, shown as the y-dimension in FIG. 7) of the waveguide pupil expander of FIGs. 11A and 11B may be arranged to absorb, attenuate, or diffusely reflect / scatter light as described herein.

[0100] In addition to or as an alternative to the reflection suppression means of the first or second embodiment, an opaque boundary can be provided around all minor / edge surfaces of the optical component. In particular, an opaque box can be provided surrounding the sides 1046, 1147 and ends 1144, 1145 of the waveguide pupil expander 1040, the light-turning prism layer 1048, and the louver structure 1106 thereon. This opaque boundary can further prevent sunlight from entering the minor / edge surface of the optical component and further suppress internal reflection of sunlight incident on the minor / edge surface. The opaque boundary can include a sheet material with light-absorbing, diffusely reflective / scattering, and / or attenuating properties, or a sheet material including a coating or film with light-absorbing, diffusely reflective / scattering, and / or attenuating properties. For example, the opaque boundary can be treated (e.g., etched or roughened) to diffusely reflect / scatter and / or attenuate light incident thereon.

[0101] FIG. 9 is a polar diagram equivalent to FIG. 8 showing a simulation of sunlight glare at the center of the viewing area of ​​an automotive head-up display including a waveguide pupil expander according to the second embodiment of FIG. 11B for different solar elevation angles.

[0102] Figure 9 shows the solar reflection S at the center of the viewing area depending on the polar position of the sun. R The figure shows a roughly circular region in the center where solar glare was found to occur. In particular, solar reflections are diffuse and result in low-intensity reflections (e.g., below a threshold intensity) at all polar locations within the roughly circular region shown. Thus, the first, second, and third types of reflections described above are diffuse and indistinguishable from one another in the viewing area. Therefore, simulations surprisingly found that the countermeasures and techniques described herein result in a significant reduction in solar glare in the viewing area.

[0103] Combiner shape correction An advantage of projecting a hologram into the eyebox is that optical compensation can be encoded into the hologram (see, for example, EP 2936252, incorporated herein). 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 vehicle windshield. Details of this approach are described in EP 2936252, and the detailed features of those systems and methods are not repeated here as they are not essential to the novel teachings of the present disclosure and are merely exemplary of configurations that would benefit from the teachings of the present disclosure.

[0104] Control device The present disclosure is also compatible with optical configurations including a control device (e.g., an optical shutter device) for controlling the delivery of light from a light-channeling hologram to a viewer. The holographic projector may further include a control device arranged to control the delivery of the angular channels to an eyebox location. UK Patent Application No. 2108456.1, filed June 14, 2021, and incorporated herein by reference, discloses at least one waveguide pupil expander and control device. From at least this prior disclosure, the reader will understand that the optical configuration of the control device is essentially based on the user's eyebox location and is compatible with any hologram computation method that achieves light channeling as described herein. The control device can be described as an optical shutter or iris device. The optical shutter device includes a 1D array of apertures or windows, each of which can be independently switched between a light-transmitting state and a light-non-transmitting state to control the delivery of the hologram light channel and its replica to the eyebox. Each aperture or window may include multiple liquid crystal cells or pixels.

[0105] Additional Features The methods and processes described herein can be embodied in a computer-readable medium. The term "computer-readable medium" includes a medium configured to store data temporarily or permanently, such as random access memory (RAM), read-only memory (ROM), buffer memory, flash memory, cache memory, etc. The term "computer-readable medium" is also intended to include any medium, or combination of media, capable of storing instructions for execution by a machine. The instructions, when executed by one or more processors, cause the machine to perform, in whole or in part, one or more of the methods described herein.

[0106] The term "computer-readable medium" also includes cloud-based storage systems. The term "computer-readable medium" includes, but is not limited to, one or more tangible, non-transitory data repositories (e.g., data volumes), such as solid-state memory chips, optical disks, magnetic disks, or any suitable combination thereof. In some embodiments, executable instructions may be carried by a carrier medium. Examples of such carrier media include transitory media, such as a propagated signal carrying the instructions.

[0107] 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. This disclosure covers all modifications and variations that come within the scope of the appended claims and their equivalents.

Claims

1. an optical component having first and second major surfaces and one or more minor surfaces, each minor surface forming an edge surface of the optical component, and one or more of the first and second major surfaces being reflective; a light control layer disposed on the first major surface of the optical component, the light control layer comprising a louver structure including an array of louvers arranged to suppress reflection of sunlight received on an optical path to the first major surface; at least one edge surface of the optical component is arranged to reduce specular reflection of light incident thereon; Display system.

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

3. the at least one edge surface of the optical component is light-attenuating materials, elements, or components; and / or Comprising materials, elements, or components that diffusely reflect or scatter light; 3. The display system of claim 2.

4. 4. A display system according to claim 2 or 3, wherein the at least one edge surface of the optical component is coated with a light-attenuating coating, such as an opaque coating.

5. 5. The display system of claim 2, 3, or 4, wherein the at least one edge surface of the optical component is treated, such as by etching, to attenuate or diffusely reflect light incident thereon.

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

7. 7. A display system according to any one of the preceding claims, wherein the at least one edge surface of the optical component is arranged to absorb light incident thereon.

8. 8. The display system of claim 7, wherein the at least one edge surface of the optical component comprises a light-absorbing material, and optionally the at least one edge surface is coated with a light-absorbing coating, such as a black coating.

9. 9. The display system of claim 1, wherein the first main surface of the optical component comprises an exit surface for outputting image light of the display system to a viewing zone.

10. 10. The display system of claim 9, wherein the optical component comprises a light turning element for controlling the direction of the output image light from the exit surface.

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

12. 12. The display system of claim 11, wherein the first major surface of the light turning element interfaces with the exit surface of the optical component.

13. 13. The display system of claim 10, 11, or 12, wherein the light turning element is a light turning film, such as a film comprising an array of prisms with angled faces facing the exit face of the optical component.

14. 14. A display system according to any one of claims 10 to 13, wherein the at least one edge surface of the light turning element is arranged to absorb light incident thereon or to attenuate or diffusely reflect / scatter light incident thereon.

15. A display system according to any preceding claim, comprising an opaque boundary or box surrounding the one or more minor surfaces of the optical component.

16. 16. A display system according to any preceding claim, wherein the optical component comprises a waveguide pupil expander, the first and second major surfaces being opposed / parallel reflective surfaces arranged to provide internal reflection and guiding of image light therebetween, and optionally the first major surface comprising a partially reflective-partially transmissive surface forming an exit surface of the waveguide pupil expander.

17. 17. The display system of claim 16, wherein the at least one edge surface arranged to suppress specular reflection of light incident on the edge surface comprises an edge surface at a first end of the waveguide pupil expander or an edge surface of a light turning element on the exit surface of the waveguide pupil expander adjacent the first end of the waveguide pupil expander, and wherein pupil expansion occurs from the first end to the second end of the waveguide pupil expander.

18. 18. A waveguide pupil expander for the display system of claim 16 or 17.

Images