Display optics using light guides

Abstract

This disclosure relates to a projection display having a light guide for a perspective display system, using holographic or diffractive optical elements as input coupling optics, and combined with a Fresnel mirror as an output coupling optics. Displays using this light guide can achieve wide-angle (e.g., field of view exceeding 90 degrees), high resolution, and large viewing windows, while remaining compact.

Description

[0001] Related applications

[0002] This application claims priority to U.S. Patent Application No. 16 / 934,536, filed July 21, 2020; U.S. Provisional Patent Application No. 63 / 019,388, filed May 3, 2020; and U.S. Provisional Patent Application No. 62 / 962,566, filed January 17, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to display optics using light guides (e.g., a perspective display that projects images through a thin light guide using holographic or diffractive optical elements). Background Technology

[0004] In recent years, with the widespread acceptance of smartphones, see-through displays (e.g., heads-up displays and wearable displays) have gained attention. See-through displays can free up the hands and display images at the same distance as the conventional field of vision. While see-through displays are practical, in the past, some (e.g., see-through displays using holograms) failed to satisfy viewers because they did not provide a sufficiently large viewing angle. Optical systems that are light-transmitting, small, bright, and have high resolution and / or see-through properties would be useful, but achieving a relatively large viewing angle remains a significant challenge for some systems. Summary of the Invention

[0005] In one aspect, this disclosure provides a display system for providing light to a viewer's eye, comprising: a display device; a group of one or more lenses configured to receive light from the display device; a light tube; an input coupling optical element configured to receive light from the group of one or more lenses and provide light into the light tube, the light tube having three or more sides and at least a portion of the surfaces of the sides of the light tube being reflected by a coating or total internal reflection; an output coupling light guide; and one or more mirrors configured to reflect light from an exit portion of the light tube into the output coupling light guide. The one or more mirrors include at least a first Fresnel reflector comprising a plurality of sawtooth grating elements configured to reflect light into the output coupling light guide, and the output coupling light guide includes a second Fresnel reflector comprising a plurality of sawtooth grating elements.

[0006] This aspect may include one or more of the following features.

[0007] The input coupling optical element includes a prism, and the group of one or more lenses is telecentric, wherein the main rays emitted from the pixels of the display device are substantially perpendicular to the surface of the display device, and the main rays intersect each other in or near the prism.

[0008] The input coupling optical element includes a prism having a reflective surface configured to receive light from the group of one or more lenses and reflect the light into the light tube, wherein the normal vector of the reflective surface is 15 to 45 degrees relative to the optical axis of the group of one or more lenses.

[0009] The input coupling optical element includes a prism having a reflective surface configured to receive light from the group of one or more lenses and reflect the light into the light tube, and the normal vector of the reflective surface is configured to rotate to form an angle between 30 degrees and 60 degrees relative to the long side of the light tube.

[0010] The input coupling optical element includes a prism with a refractive index greater than 1.4, and the optical tube has a refractive index greater than 1.4.

[0011] The size of the outlet portion varies at least in part based on the position of the outlet portion along the long side of the light tube.

[0012] The grating element of the first Fresnel reflector is bent on the surface of a sawtooth triangular prism, and the surface is inclined at 15 to 45 degrees relative to the top surface of the light tube. The normal vector of the first Fresnel reflector is set such that light rays parallel to the optical axis of the group of one or more lenses are substantially parallel to the normal vector of the top surface of the light tube.

[0013] The input coupling optical element includes a prism with a refractive index greater than 1.3, and the output coupling optical guide has a refractive index greater than 1.3. The refractive index of the prism is substantially equal to the refractive index of the optical guide.

[0014] The output coupling light guide has an inclined surface forming a prism into which light can enter, and the normal vector of the inclined surface is between 15 degrees and 45 degrees relative to the top surface of the light guide, so that light from one or more mirrors is reflected into the output coupling light guide.

[0015] The output coupling light guide has an inclined surface forming a prism into which light enters, and the normal vector of the inclined surface is between 15 degrees and 45 degrees relative to the top surface of the light tube, so that light from the one or more mirrors is reflected into the output coupling light guide.

[0016] The second Fresnel reflector includes a grating region comprising a plurality of sawtooth grating elements configured to reflect light from the one or more reflectors to the viewer's eye, and a flat region between the sawtooth grating elements, wherein no sawtooth grating elements are present; the output coupling light guide reflects light by total internal reflection and is substantially transparent, allowing external light to reach the viewer's eye, and the grating region includes a reflective coating.

[0017] The second Fresnel reflector includes a grating region comprising a plurality of sawtooth grating elements configured to reflect light from the one or more reflectors to the viewer's eye, and a flat region between the sawtooth grating elements, wherein double reflection of the flat region and the sawtooth grating elements is blocked by a light-absorbing region.

[0018] At least one of the light tube and / or the output coupling light guide includes one or more layers configured to at least partially reflect light to reduce unlit areas.

[0019] The surface of the output coupling light guide includes a curved envelope of multiple flat surfaces, such that the internal reflected beam has the same angle as the flat surface.

[0020] The angles of the multiple sawtooth grating elements of the second Fresnel reflector of the output coupled light guide change with position, so that the image is focused at a finite distance.

[0021] The display system also includes a plurality of groups of the display system, which overlap to allow images to be viewed at multiple distances.

[0022] The display system also includes integrating multiple waveguides into a single waveguide using one or more dichroic filters and at least one dichroic cross prism.

[0023] At least one of the light guide and / or the light tube is covered with a holographic optical element, a diffractive optical element, or a multilayer thin film, thereby reducing the total internal reflection angle and thus expanding the field of view of the display system.

[0024] At least one of the light guide and / or the optical tube includes a lower refractive index material adjacent to the input coupling optical element and a higher refractive index material in or near the output coupling light guide.

[0025] The light guide is laminated with a higher refractive index material, which has a higher refractive index than the light guide, and the second Fresnel reflector is formed on the higher refractive index material.

[0026] The input coupling optical element includes a first optical element comprising at least one of a holographic optical element (HOE) and / or a diffractive optical element (DOE), arranged such that the angle of attack of the diffracted beam is smaller than the angle of attack of the incident beam; and a second optical element comprising at least one of a holographic optical element and / or a diffractive optical element, placed in the light guide to receive light from the light guide, and the second optical element is arranged such that the angle of attack of the outgoing beam is larger than the angle of attack of the incident beam; for beams from the same pixel, the angle between the outgoing light and the normal direction of the second optical element is substantially equal to the angle between the incident light and the normal direction of the first optical element.

[0027] In another aspect, this disclosure provides a display system comprising: a display device; a group of one or more lenses configured to receive light from the display device; an input coupling optical element configured to receive light from the group of one or more lenses; an output coupling light guide; and one or more mirrors configured to reflect light into the output coupling light guide. A diffractive optical element (DOE) in at least one of the input coupling optical element or the output coupling light guide is configured to use 7th-order diffraction for light including a blue spectral component, 6th-order diffraction for light including a green spectral component, and 5th-order diffraction for light including a red spectral component.

[0028] This aspect may include one or more of the following features.

[0029] The display system also includes a light tube configured to optically couple a first diffractive optical element in an input coupling optical element to a second diffractive optical element in an output coupling light guide.

[0030] The display system also includes: an optical element with electronically controllable focal length.

[0031] The electronically controllable focal length optical element is configured to display multiple images at multiple corresponding distances in sequence with the display device.

[0032] This aspect may have one or more of the following advantages.

[0033] Some embodiments of the display system described herein can be used as a periscope, having a thin light guide (e.g., a waveguide or light pipe) combined with a prism or Fresnel mirror having a reflective surface. This display system can be adapted for automotive head-up displays and can be configured as a wearable display (e.g., as compact as eyeglasses), or configured to achieve a wide field of view (FOV), high resolution, and a large eyebox.

[0034] Some implementations can use light guides (e.g., waveguides or optical tubes) to expand the field of view (FOV) of a display, thereby delivering light from the display to the viewer. In some examples, if the waveguide's optics system uses only specular reflection, the angle at which incident light enters the waveguide remains constant. This means that in such examples, the FOV is the same as the angle of attack of the incident light, and the FOV can be increased by using a larger angle at which the incident light converges into the waveguide, for example, by using more lenses or a more complex optical system. Typically, holographic optical elements (HOEs) or diffractive optical elements (DOEs) increase the angle of attack of diffracted light when used as input coupling optics, while HOEs or DOEs decrease the angle of attack of diffracted light when used as output coupling optics. Some implementations of the systems and apparatus described herein use HOEs or DOEs as input coupling optics to increase the angle of attack of diffracted light and use specular reflection for output coupling to maintain the angle of attack (e.g., neither increasing nor decreasing). Because it combines diffractive optics and geometric optics, where the diffractive optics are used to couple and extend the incident beam, while the geometric optics do not change the beam's angle of attack, the final combined optics configuration extends the angle of attack (dθ). i to dθ out ), and expand the field of view. For example, in Figure 4 In the example shown, dθ out Greater than dθ i If the reflector ( Figure 4 If 403 is a regular reflecting mirror, then dθ i =dθ out Furthermore, the facing angle will not increase, but if the reflector 403 is a HOE or DOE, the facing angle will increase.

[0035] Other features and advantages of the invention will be more readily understood from the following description, the accompanying drawings, and the claims. Attached Figure Description

[0036] This disclosure can be better understood by reading in conjunction with the accompanying drawings, and the following detailed description will provide further insight. It should be emphasized that, by convention, the features in the drawings are not drawn to scale. Instead, for clarity, the dimensions of the features have been arbitrarily enlarged or reduced.

[0037] Figure 1 This is an illustration of an example optical system that enables a perspective display to form a virtual image using prisms and Fresnel mirrors.

[0038] Figure 2A This is an illustration of an example projection lens assembly, which is included as part of an input coupling optics device.

[0039] Figure 2BAn example is shown where a light guide receives light from a prism, which is part of an input coupling optics device.

[0040] Figure 2C An example is shown where a light guide receives light from a hologram that is part of an input-coupled optics device.

[0041] Figure 2D An example is shown where a light guide receives light through a projection lens group and an input coupling optics.

[0042] Figure 3 An example of a display system is shown.

[0043] Figure 4 This demonstrates how to increase the incident angle of the incident beam using HOE or DOE.

[0044] Figure 5 This illustrates why the angle of the diffracted beam is limited by the refractive index of the HOE substrate.

[0045] Figure 6 An example of a light guide with a coating is shown, which reflects light beams with an incident angle smaller than the TIR angle.

[0046] Figure 7 Another example of an optical guide is shown.

[0047] Figure 8A , Figure 8B and Figure 8C An example of a structure that avoids unnecessary double reflections is shown.

[0048] Figure 9 This illustrates why the maximum angle of the light beam is limited by the refractive index of the HOE substrate.

[0049] Figure 10 An embodiment of a distortion-free optical tube and optical guide system is shown.

[0050] Figure 11 Another embodiment of a distortion-free optical tube and optical guide system is shown.

[0051] Figure 12 It is a perspective view showing the correct path inside the optical tube and waveguide.

[0052] Figure 13A An example of an image formed at infinity is shown.

[0053] Figure 13B An example is shown of an image formed at an arbitrary distance that can be electronically controlled.

[0054] Figure 14 An example of the structure of an electronically controllable variable focal length lens is shown.

[0055] Figure 15A and Figure 15B An example of a very wide field of view (FOV) with 90 degrees (horizontal) × 90 degrees (vertical) is shown, simulated by an optical design tool.

[0056] Figure 16 This is a structural diagram of a DOE, which can diffract three primary colors in the same direction through a single-layer DOE.

[0057] Figure 17 yes Figure 16 The graph shown illustrates the relationship between the diffraction efficiency of the DOE and the wavelength of the incident light. Detailed Implementation

[0058] Some implementations of the display system are characterized by a perspective display having a relatively large field of view (FOV) in the horizontal direction (e.g., more than 90 degrees or + / - 45 degrees) and an eye-box greater than 15 mm. Figure 1 An embodiment of the display system is illustrated. The display system includes a display device 108, which includes a pixel array and a projection lens group 101. Light from the display device 108 is projected onto a HOE 102, which serves as an input coupling optics device, and enters a light tube 103. The light propagates in the light tube 103, and only light rays with the same direction as the original light rays from the HOE 102 are selected and guided to a folding mirror 105. These light rays are reflected by the folding mirror 105 at approximately 90 degrees to an output coupling light guide 107. In some embodiments, the light guide 107 is a sheet or plate waveguide that guides light between surfaces at an interface with air or certain lower refractive index materials via total internal reflection (TIR), and in some embodiments, the light guide 107 is a sheet or plate that guides light reflected between reflective surfaces of a sheet or plate. In this example, light is reflected to the viewer's eye by a sawtooth Fresnel mirror formed on the surface of the light guide 107. Details of each component example will be described in more detail below.

[0059] On one hand, the display system acts as an exit pupil expander. For example, the viewer should be able to see the image even if they move their eyes. Some systems have only a relatively small exit pupil (e.g., an exit pupil of 0.5 mm diameter, such as at the level of a mobile phone camera lens). However, the human eye can move within a range of + / - half an inch or 1 inch. The exit pupil expander function of the display system described herein is capable of expanding the exit pupil from approximately 0.5 mm in diameter to approximately 1 inch (25.4 mm) in diameter.

[0060] An input-coupled HOE or DOE redirects the light beam from the external projection lens system into the light tube. Some beams exit the light tube through one or more slits or other openings to a Fresnel reflector. The beam is reflected outwards by an output-coupled element (e.g., a Fresnel reflector consisting of individual reflective grating elements, also referred to herein as a "Fresnel mirror") to enter the light guide. The beam arrives at a second input-coupled HOE or DOE connected to the light guide and is reflected inwards. After propagating inside the light guide, the beam is reflected by the output-coupled Fresnel mirror to the viewer's eye. For example, the light guide can be implemented as a light guide plate (a flat rectangular plate with a surface area of ​​approximately 50 mm × 50 mm).

[0061] Examples of features that enable a display system to utilize an exit pupil expander include the following. The incident beam angle can be compressed (e.g., from 60 degrees to 20 degrees). The compressed beam propagates within the light tube, redirects, and distributes from multiple openings along the light tube to a wide area of ​​the light guide plate, thus allowing for a larger field of view (FOV). For example, a Fresnel folding mirror's grating element redirects light to the light guide plate, which expands the exit pupil in a first dimension (e.g., the x-axis). An output-coupled DOE (e.g., another Fresnel mirror) connected to the light guide plate also expands the beam angle exiting to the viewer. An output-coupled Fresnel reflector expands the exit pupil in a second dimension (e.g., the y-axis perpendicular to the x-axis).

[0062] Other additional features may be included in some implementations of the display system. For example, a single DOE can diffract three primary color beams into the same direction. This reduces the number of layers required for light guides or other output coupling optics (e.g., from three layers to a single layer). Moreover, images can be dynamically formed at each of a plurality of selected distances.

[0063] exist Figure 2A , Figure 2B , Figure 2C and Figure 2D The diagram illustrates implementations of different types of input coupling optics. For example... Figure 2A As shown, the display device 203 provides light to the projection lens group 205, and the distance between the center of the display device 203 and a given pixel (labeled "X" 201) and the projection angle θ of the light from that given pixel are... 202Proportional. For example, the projection lens is arranged to ensure that the angle of the output light is proportional to the distance of the pixel from the center of the pixel array (or θ is proportional to X). The display device 203 emits a light beam 204 from each of its pixels into the projection lens group 205. The lens group 205 is designed as a telecentric optics, meaning that the principal rays of the light beam 204 from each pixel of the display device 203 entering the projection lens group 205 are substantially parallel to the optical axis of the projection lens group. The lens group 205 can be configured such that the image is focused at infinity or substantially far away, such that all the light rays projected from a single pixel are substantially parallel to each other, as... Figure 2A The light rays 207A, 207B, and 207C are shown in the diagram. This feature is also known as an F-Theta lens. This optics ensures that all light rays from a single pixel are parallel. This is the principle behind focusing an image after the light rays are mixed in the light tube in some implementations, because this optics ensures that all light rays with the same direction originate from a single pixel.

[0064] Figure 2B An example of a light guide 214 (e.g., a light tube or waveguide) is shown, in which a prism 213, as part of an input coupling optics, receives light from a display device 211 via a lens group 212. Figure 2C An example of a light guide 225 (e.g., a light tube or waveguide) is shown, in which a hologram 221, as part of an input coupling optics 222, receives light from a display device 220 via a lens group 223. Figure 2D An example of a light guide 233 (e.g., a light pipe or waveguide) is shown, wherein a projection lens group 231 provides light to an input coupling optics 232 (e.g., a HOE or DOE or a prism), and the figure also shows a beam 234 propagating inside the light guide 233.

[0065] Figure 3 Another implementation is shown where multiple waveguides are integrated into a single waveguide using dichroic filters and cross prisms. HOEs allow for multiple recordings and the superposition of multiple wavelength holograms into a single layer. However, certain types of hologram materials have limitations on the maximum number of recordings, and surface-undulating DOEs do not allow for multi-wavelength diffraction. These can use multilayer waveguides, typically one color per layer. For color displays, three-layer waveguides can be used. This implementation achieves a single-layer waveguide for multicolor displays by integrating the three color layers of the waveguide into a single layer with dichroic filters and dichroic cross prisms, such as... Figure 3As shown. Optical element 303 is a waveguide for blue light and has a HOE or DOE layer at 307. The beam diffracted by the HOE or DOE contains three colors, but only the blue light is filtered by the dichroic filter 308. Optical elements 302 and 301 are waveguides for green and red light, respectively. All three colored beams after the filters are introduced into a cross prism 311 and integrated into an intermediate layer 310. Integrating three layers into a single layer is not limited to waveguides but is also applicable to optical tubes.

[0066] Figure 4 Another embodiment is shown. The incident ray is shown, for example, between ray 405 and ray 406, and its angle of repose is shown as dθ. i (401). θ i (409) is the intermediate ray between them. The incident ray will converge onto HOE or DOE 403 and be diffracted by HOE / DOE 403 to the output angle between ray 402 and ray 407. θ out It is the angle between intermediate ray 408 and ray 402 and ray 407. Because dθ out =cos(θ) i )*dθ i / cos(θ out ), θ i Approximately zero, θ out Approximately 120 degrees, dθ out =-2*dθ i This means that the angular divergence of the diffracted beam between its component rays is twice that of the incident beam. Therefore, a HOE or DOE can be used to widen the ray angle of the incident beam. If a HOE or DOE is used as an output coupling optics, where θ i Approximately 60 degrees, θ out If it is approximately 180 degrees, then the relationship is reversed and dθ out = -0.5dθ i This means the angle will be reduced by half. Therefore, if the system uses a HOE or DOE for input coupling and employs ordinary optical reflectors (such as mirrors, prisms, or Fresnel reflectors), the system can obtain an expanded exit angle from a smaller incident angle. This will increase the FOV.

[0067] Figure 5Another embodiment is illustrated. A light tube 501 receives light from an input coupling optics element 503 (e.g., HOE or DOE). A first propagation direction 504 represents the angular propagation direction of the beam through the input coupling optics element 503. The diffracted beam has a parallelogram distortion along the propagation direction 504. After the beam exits the light tube 501 through an opening along the light tube 501, the beam enters a light guide plate 502. The opening along the light tube 501 can be a location lacking reflective material or a location where some rays propagating along the light tube 501 have an incident angle smaller than the total internal reflection angle. At an output coupling optics element 505 (e.g., a folding mirror, including a Fresnel mirror with a Fresnel reflector), a second propagation direction 506 can be configured perpendicular to the propagation direction 504 to reduce image distortion.

[0068] Figure 6 An implementation of the optical guide is shown. In some cases, the optical guide can be implemented as a waveguide with a high-refractive-index core surrounded by a cladding of lower refractive index (e.g., air in some cases). However, the FOV of the waveguide is limited by the minimum angle of total internal reflection (TIR) ​​of the material used for the waveguide core. To increase the FOV, for the optical guide 601 configured as a light tube, coatings (605 and 608) on either surface of the transparent material plate reflect the beam whose constituent rays are incident at an angle smaller than the TIR angle associated with the material plate. The input coupling optics 602 are either HOE or DOE. Without the coating, beam 606 will be transmitted as beam 607, but with the coating 608, beam 606 can be reflected as beam 604.

[0069] Figure 7 Another embodiment of the light guide is shown. This light guide comprises two regions (region 701 and region 707) composed of two different materials with different refractive indices. This embodiment enables the HOE 702 to diffract the incident beam 700 to a beam 705 incident at an angle below the TIR angle associated with material 703, and to produce a material region 707 with a higher refractive index and a smaller TIR angle, thereby expanding the FOV. The maximum angle of the diffracted beam by the HOE 702 is limited by the refractive index of the HOE substrate, and it requires the waveguide where the HOE is placed to use a material with a low or similar refractive index. The waveguide can be connected to the higher refractive index material toward the output coupling region, and this technique can be used to increase the FOV. If the higher refractive index material 707 is not present, the diffracted beam 705 is transmitted (as beam 704) and can be reflected by reflected beams 706 and 708 as shown.

[0070] exist Figure 8A , Figure 8B and Figure 8CThe diagram illustrates an implementation of output coupling from the optical guide. In these implementations, undesirable double reflections (or "ghosting") of the waveguide with Fresnel mirrors can be avoided. The waveguide material 808 has a higher refractive index than the material on either side. The waveguide is designed for single reflection in the flat region 801 or the Fresnel mirror region 802 (as shown by incident rays 803A, 803B and reflected rays 804A, 804B), while double reflections are undesirable (as shown by incident rays 805 to reflected rays 806). Another limiting factor for FOV is this undesirable reflection produced by the individual sawtooth mirrors of the waveguide's Fresnel reflector, such as... Figure 8A As shown, as the angle of the propagating beam increases (the angle with the normal vector of the waveguide surface becomes larger), the beam may strike 806 twice before being coupled out of the waveguide, which may be undesirable. Figure 8B An example is to laminate a higher refractive index material 808 onto a waveguide and place a Fresnel mirror on the higher refractive index material 808. Figure 8C Another embodiment is shown to avoid double reflection from the external sawtooth protrusions of the Fresnel mirror grating element 815.

[0071] Figure 9 This illustrates how the maximum angle of beam 905 is limited by the refractive index of the substrate of the HOE (909 and 910). If the refractive index of the HOE substrate is less than that of the waveguide (908), the diffracted beam (904) from the HOE cannot exceed 90 degrees, and θ max Limited by the TIR angle between the waveguide material (908) and the HOE substrate (909).

[0072] like Figure 4 As shown, the orientation angle of the diffracted beam (dθ between 402 and 407) out Due to diffraction, the angles are substantially larger than the incident beam angles (dθ1, 401), and the beams (402 and 407) must be within total internal reflection. This limits the angles of the incident beams (405 and 406). Figure 10 Another implementation is shown that avoids this potential limitation. Figure 10In the structure shown, the incident beam's angle of attack (1007) is reduced by a high-refractive-index prism (1008) and further reduced by diffraction by a DOE (1003). In this example, the original incident beam angle is 60 degrees (1007), reduced to 40 degrees due to the high refractive index, and further reduced to 20 degrees after diffraction by the DOE. In this example, the beam angle can be reduced to 1 / 3. After the beam propagates through the optical tube at a reduced angle, this example shows the angle being expanded by a second DOE, then propagating inside the waveguide, and then expanded back to the original angle of the human eye. Using this technique (compression => propagation in the optical tube and waveguide => decompression => eye), even a 90-degree FOV can be achieved. This technique helps to achieve distortion-free images because as long as the two DOEs are parallel, they compensate for the distortion they cause to each other.

[0073] Figure 11 Another implementation is shown. Although rotational deformation may occur by tilting the DOE, the FOV can still be expanded (with...). Figure 10 (Compared to the example in the image). Rotation distortion can be compensated for by rotating the display system.

[0074] Figure 12 Another implementation of the display system is shown, in which a semi-reflective mirror is inserted into the optical tube to increase the number of beams maintaining the same propagation angle. This reduces the distance between two beams in the waveguide.

[0075] Figure 13A The image shows the trajectory of a beam diffracted from an input coupled DOE 1305, where the image location is at infinity because the beams from individual pixels are parallel. Figure 13B In the embodiment shown, the position of the image can be electronically controlled using a variable focal length diffractive lens, wherein the liquid crystal material is electrostatically driven by a driver 1320 to change its refractive index.

[0076] Figure 14 An example of a variable focal length lens is shown. The refractive index of the liquid crystal can be changed by applying an electrostatic voltage of up to 0.2. However, this is insufficient to control the image distance of the refractive lens. Figure 14The diffractive lens shown can significantly alter its focal length because diffraction bends light much more than a refracting lens. A single DOE lens can sequentially display multiple images at multiple distances under the influence of a liquid crystal driving voltage. Each image can be synchronized with the focal length adjusted by the DOE lens. For example, person A is displayed at time 1, 3m distance; person B at time 2, 10m distance; house A at time 3, 100m distance; and the background scene at time 4, infinity. If the switching speed of these images is fast enough, the viewer will not notice these changes and will recognize the generated composite scene as a virtual and / or augmented reality 3D scene (e.g., not like stereoscopic scenes but so-called "light fields") while the convergence and adaptation overlap.

[0077] Figure 15A and Figure 15B An example of an ultra-wide FOV augmented reality (AR) display with 90° (horizontal) × 90° (vertical) is shown, successfully designed and simulated using optical design tools.

[0078] exist Figure 16 The diagram illustrates a DOE implementation. Unbound by theory, the relationship between the angle of incident light and the angle of outgoing light can be given by the following formula:

[0079] sin(θ out )–sin(θ in ) = m / λ * constant (a function of the groove spacing, such as a sawtooth-shaped reflector)

[0080] Where, θ out = The angle between the emitted light and the normal direction of the DOE surface.

[0081] θ in = The angle between the incident light and the normal direction of the DOE surface.

[0082] m = diffraction order

[0083] λ = wavelength of light. If first-order diffraction is used for a DOE, the exit angle will vary depending on the wavelength of the incident light. This is why a single DOE cannot be used for different colors in some cases, while multiple DOEs or multi-layer DOEs can be used to provide color displays. This disclosure describes a method of using a single-layer DOE for three primary colors. If different diffraction orders are used for different colors, i.e., m / λ = the same for all three primary colors, for example, m = 7 for λ = 0.45 μm (blue), m = 6 for λ = 0.525 μm (green), and m = 5 for λ = 0.63 μm (red), then m / λ = 15.555 for all three colors. This means that all three colors will diffract in the same direction. The next problem is whether cross-contamination occurs, meaning that diffraction of different orders may enter the field of view and cause cross-contamination, or so-called ghosting. Figure 17 The diffraction efficiency diagram shows the likelihood of no cross-contamination or very little contamination. This indicates that a single-layer DOE can be fabricated for color displays.

[0084] Although this disclosure has been described in conjunction with certain embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments, but rather is intended to cover various modifications and equivalents included within the scope of the claims appended to this disclosure, which should be interpreted in the broadest possible sense to cover all such modifications and equivalents permitted by law.

Claims

1. A display system for providing light to an eye of a viewer, the display system comprising: a display device comprising an array of pixels; a set of one or more lenses configured to receive light from respective pixels in the array of pixels and to project the light such that respective angles between at least two projected beams of light are proportional to respective distances of different pixels receiving the projected light from a center of the array of pixels; a light pipe; an input-coupling optical element configured to receive light from the set of one or more lenses and to redirect the projected light into the light pipe, the light pipe having three or more sides and at least a portion of surfaces of the three or more sides of the light pipe being reflective by a coating or total internal reflection; an output-coupling light guide; and one or more mirrors configured to reflect light from an exit portion of the light pipe into the output-coupling light guide; wherein the one or more mirrors comprise at least a first Fresnel reflector comprising a plurality of sawtooth-shaped grating elements configured to reflect light into the output-coupling light guide, and the output-coupling light guide comprises a second Fresnel reflector comprising a plurality of sawtooth-shaped grating elements.

2. The display system of claim 1, wherein: the input-coupling optical element comprises a prism and the set of one or more lenses is telecentric, wherein chief rays emitted from pixels of the display device are perpendicular to a surface of the display device and the chief rays cross each other within or near the prism.

3. The display system of claim 1, wherein: the input-coupling optical element comprises a prism having a reflective surface configured to receive light from the set of one or more lenses and to reflect the light into the light pipe, and a normal vector of the reflective surface is 15 to 45 degrees with respect to an optical axis of the set of one or more lenses.

4. The display system of claim 1, wherein: the input-coupling optical element comprises a prism having a reflective surface configured to receive light from the set of one or more lenses and to reflect the light into the light pipe, and a normal vector of the reflective surface is configured to rotate to form an angle of between 30 and 60 degrees with respect to a long side of the light pipe.

5. The display system of claim 1, wherein: the input-coupling optical element comprises a prism having a refractive index greater than 1.4, and the light pipe has a refractive index greater than 1.

4.

6. The display system of claim 1, wherein: a size of the exit portion varies based at least in part on a position of the exit portion along a long side of the light pipe.

7. The display system of claim 1, wherein: ​ The plurality of sawtooth grating elements of the first Fresnel reflector are curved on the surface of sawtooth triangular prisms, and the surface is tilted 15 degrees to 45 degrees relative to the top surface of the light pipe, the normal vector of the first Fresnel reflector is set such that light rays parallel to the optical axis of the group of one or more lenses are parallel to the normal vector of the top surface of the light pipe.

8. The display system of claim 1, wherein: The input-coupling optical element comprises a prism having a refractive index greater than 1.3, the output-coupling light guide has a refractive index greater than 1.3, and the refractive index of the prism is equal to the refractive index of the light guide.

9. The display system of claim 1, wherein: The output-coupling light guide has a tilted surface forming a prism into which light rays can enter, and the normal vector of the tilted surface is between 15 degrees and 45 degrees relative to the top surface of the light guide pipe such that light rays from the one or more mirrors are reflected into the output-coupling light guide.

10. The display system of claim 1, wherein: The output-coupling light guide has a tilted surface forming a prism into which light rays enter, and the normal vector of the tilted surface is between 15 degrees and 45 degrees relative to the top surface of the light pipe such that light rays from the one or more mirrors are reflected into the output-coupling light guide.

11. The display system of claim 1, wherein: The second Fresnel reflector comprises a grating area comprising a plurality of sawtooth grating elements configured to reflect light rays from the one or more mirrors to the viewer’s eye, and a flat area between the plurality of sawtooth grating elements in which there are no sawtooth grating elements; The output-coupling light guide reflects light rays by total internal reflection and is transparent such that external light can reach the viewer’s eye, and the grating area comprises a reflective coating.

12. The display system of claim 1, wherein: The second Fresnel reflector comprises a grating area comprising a plurality of sawtooth grating elements configured to reflect light rays from the one or more mirrors to the viewer’s eye, and a flat area between the plurality of sawtooth grating elements, double reflections of which and the sawtooth grating elements are prevented by a light-absorbing area.

13. The display system of claim 1, wherein: At least one of the light pipe and / or the output-coupling light guide comprises one or more layers configured to at least partially reflect light to reduce unlit areas.

14. The display system of claim 1, wherein: A surface of the output-coupling light guide comprises a curved envelope of a plurality of flat surfaces such that internally reflected light beams have the same angle as the flat surfaces.

15. The display system of claim 1, wherein: The angle of the plurality of sawtooth grating elements of the second Fresnel reflector of the output-coupling light guide varies with position such that the image is focused at a finite distance.

16. The display system of claim 1, further comprising: a plurality of groups of the display system overlapping so that images at a plurality of distances can be viewed.

17. The display system of claim 1, further comprising: integrating a plurality of waveguides into a single waveguide using one or more dichroic filters and at least one dichroic cross prism.

18. The display system of claim 1, wherein: at least one of the light guide and / or the light pipe is coated with a holographic optical element, a diffractive optical element, or a multilayer film to reduce the angle of total internal reflection, which in turn expands the field of view of the display system.

19. The display system of claim 1, wherein: at least one of the light guide and / or the light pipe includes a lower index material adjacent to the input-coupling optical element and a higher index material within or adjacent to the output-coupling light guide.

20. The display system of claim 1, wherein: the light guide is laminated with a higher index material having a higher index of refraction than the light guide, and the second Fresnel reflector is formed on the higher index material.

21. The display system of claim 1, wherein: the input-coupling optical element includes a first optical element comprising at least one of a holographic optical element and / or a diffractive optical element arranged so that the angle of incidence of a diffracted beam is less than the angle of incidence of an incident beam; and a second optical element comprising at least one of a holographic optical element and / or a diffractive optical element placed in the light guide to receive light from the light pipe, and arranged so that the angle of incidence of an emergent beam is greater than the angle of incidence of an incident beam; for a beam of light from the same pixel, the angle of the emergent light with respect to the normal direction of the second optical element is equal to the angle of the incident light with respect to the normal direction of the first optical element.

22. A display system, comprising: a display device comprising an array of pixels; one or more lenses configured to receive light rays from respective pixels in the array of pixels and to project the light rays so that respective angles between at least two projected light rays are proportional to respective distances of different pixels that receive the projected light rays from a center of the array of pixels; an input-coupling optical element configured to receive the light rays from the one or more lenses and to redirect the projected light rays; an output-coupling light guide; and one or more mirrors configured to reflect the light rays into the output-coupling light guide; wherein diffractive optical elements in at least one of the input-coupling optical element or the output-coupling light guide are configured to use a 7th order of diffraction for light comprising a blue spectral component, a 6th order of diffraction for light comprising a green spectral component, and a 5th order of diffraction for light comprising a red spectral component.

23. The display system of claim 22, further comprising: ​ an optical pipe configured to couple light between a first diffractive optical element in the input-coupling optical element and a second diffractive optical element in the output-coupling light guide.

24. The display system of claim 22, further comprising: an electronically controllable focal length optical element.

25. The display system of claim 24, wherein: the electronically controllable focal length optical element is configured to display a plurality of images at a plurality of respective distances that are sequentially synchronized with the display device.

Images