Supporting large field of view waveguides for red, green, and blue on one board

Abstract

Embodiments of the present disclosure relate to supporting large field of view waveguides for red, green, and blue on a single panel. An optical device for combining RGB light signals in a single waveguide. The device includes a plurality of DOEs. A first DOE is configured to receive a light signal at an input propagation angle and diffract the light signal based on a spectrum such that light of one spectrum is primarily diffracted in a first direction and path and light of a second spectrum is primarily diffracted in a second, different direction and path. The first DOE is configured to diffract the light into a second DOE. The second DOE is configured to diffract the light into a third DOE. The third DOE is configured to diffract the light into an eyebox that maintains an output propagation angle substantially parallel to the input propagation angle. A sum of grating vectors for each path is substantially equal to zero.

Description

[0001] Divisional Application Instructions

[0002] This application is a divisional application of Chinese patent application No. 201880043089.6, filed on May 25, 2018, entitled "Supporting a large field-of-view waveguide for red, green and blue on a single board".

[0003] Background and related technologies

[0004] Recently, there has been a renewed interest in virtual reality (VR) and augmented reality (AR) devices, as well as other such near-eye devices. These devices typically include some type of video transmitter (such as a light engine) and optics coupled to the video transmitter, which is configured to project images to the user's eyes using the device. Specifically, the user will wear a headset or similar device that includes a video transmitter optically coupled to one or more waveguides, wherein the waveguides are configured to optically couple images to the user.

[0005] One problem that manufacturers of such devices need to address is related to the limited field of view (FoV). In the context presented here, FoV is the angle of view at eye level, assumed to be fixed. Horizontally, a person's FoV is approximately 135°. However, the available FoV for virtual reality and augmented reality devices is typically much lower. The lower the available FoV of a device, the less realistic the experience becomes.

[0006] Techniques have been developed to attempt to increase the FoV. One such technique uses diffraction gratings, which scatter light along wavelengths to increase the FoV. That is, the diffraction grating is dispersive, meaning it produces a diffraction order such that all non-zero order colors propagate in different directions. While this behavior is highly beneficial, for example, in spectral applications, it is undesirable in diffraction waveguide-based AR / VR devices, as carrying and expanding image content within the waveguide requires three (or in some cases two) separate waveguides unless the FoV is very small.

[0007] Having multiple waveguides greatly complicates the manufacturing process. Not only must several waveguides be fabricated, but manufacturing tolerances also become much tighter. Furthermore, multiple plates must be precisely placed within the grating stack, introducing additional manufacturing steps that require high precision and increase costs.

[0008] The subject matter claimed herein is not limited to addressing any of the aforementioned drawbacks or to embodiments that operate only in environments such as those described above. Rather, this background is provided merely to illustrate an exemplary technical field in which some of the embodiments described herein can be practiced. Summary of the Invention

[0009] One embodiment illustrated herein includes an optical device for combining RGB optical signals in a single waveguide. The device includes multiple DOEs. The device includes a first DOE configured to receive an optical signal at an input propagation angle and diffract the optical signal based on a spectrum, such that light of one spectrum is diffracted primarily in a first direction and light of a second spectrum is diffracted primarily in different second directions, such that different portions of the optical signal take different paths including at least two different paths. The device includes a second DOE. The first DOE is configured to diffract light into the second DOE. The device includes a third DOE. The second DOE is also configured to diffract light into the third DOE. The second and third DOEs are configured to cause substantially non-parallel spreading. The third DOE is configured to diffract light into the eye box, which maintains the output propagation angle within a predetermined threshold of the input propagation angle. The multiple DOEs are associated with grating vectors. The sum of the grating vectors for each of the at least two different paths is substantially equal to zero.

[0010] This "Summary" is provided to introduce some concepts in a simplified form, which will be further described in the "Detailed Description" below. This "Summary" is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0011] Other features and advantages will be set forth in the description which follows, and some features will become apparent from the description or may be learned by practice of the teachings herein. The features and advantages of the invention can be realized and obtained by the means and combinations particularly pointed out in the appended claims. The features of the invention will become more fully apparent from the following description and the appended claims, or may be learned by practice of the invention as described below. Attached Figure Description

[0012] To describe how the above and other advantages and features can be obtained, the subject matter briefly described above will be described in more detail with reference to specific embodiments illustrated in the accompanying drawings. It should be understood that these drawings depict only typical embodiments and should not be considered as limiting of the scope. The embodiments will be described and explained with additional features and details using the drawings, in which:

[0013] Figure 1 An example of a near-eye display device is shown;

[0014] Figure 2 Various display elements are shown;

[0015] Figure 3 The waveguide is shown;

[0016] Figure 4A The wave vector space representation is shown;

[0017] Figure 4B The wave vector space representation is shown;

[0018] Figure 4C The wave vector space representation is shown;

[0019] Figure 5 The output waveguide is shown;

[0020] Figure 6A A waveguide with an odd-order extension is shown;

[0021] Figure 6B A waveguide with an odd-order extension is shown;

[0022] Figure 7 A waveguide with an even-order extension is shown; and

[0023] Figure 8 A method for combining RGB optical signals in a single waveguide is shown. Detailed Implementation

[0024] Some embodiments shown herein may include, or can be used to implement, a diffractive waveguide-based AR / VR device that: 1) carries virtual content from a light engine to in front of the user's eyes, and 2) expands the pupil, thereby increasing the range of eye movement. In particular, some embodiments can support large FoVs (e.g., 45 × 30°) for multiple different wavelengths within a single waveguide plate. For example, embodiments may be configured to support red, green, and blue (RGB) wavelengths with large FoVs within a single waveguide. Therefore, embodiments can carry large FoV RGB content through a single waveguide. This can be accomplished in some embodiments described herein.

[0025] Some embodiments include various diffractive optical elements (DOEs) in the waveguide to achieve the functionality described herein. In one example embodiment, an ingress coupling grating (referred to herein as DOE1) diffracts light into two or more directions such that the wavelength of one spectrum (e.g., red light) is diffracted primarily in directions different from the wavelength of another spectrum (e.g., blue light). In the example shown, green light is separated between these directions. This can be achieved, for example, by using a single-sided cross grating (a double-period grating) or by using linear gratings on both surfaces of the waveguide. Although the example shown herein refers to the two (or more) paths through the waveguide as the red path and the blue path, it should be understood that other chromatic paths can be implemented. Furthermore, it should be understood that, in practice, a portion of the red light (or other color) naturally passes through the blue path (or other color), and vice versa.

[0026] As will be explained in further detail below, different extended gratings (shown as DOE2 in this document) exist for the blue and red paths. Both have at least one unique DOE2 wing, but may have more. The number of DOE2 wings may also be unequal for the two paths.

[0027] For red and blue, the out-coupling grating (shown as DOE3 in this paper) has two different periods and orientations (and even more periods and orientations if multiple colors are processed separately). Again, this can be accomplished by a cross grating on one side of the grating or by “cross” linear gratings on each of the different surfaces of the waveguide.

[0028] Note that in the component where light reaches DOE3 through multiple possible paths, each path follows a zero-sum rule, such that the sum of the vectors for each path is approximately zero, as explained in more detail below.

[0029] Therefore, typically, embodiments can split the FoV of different colors into two (or more) paths, carry a portion of the FoV to DOE3, expand the pupil by pupil replication, and recombine the different contributions of each color at DOE3.

[0030] Now, other details will be shown.

[0031] Figure 1 An example of a near-eye display device in which embodiments can be practiced is shown. The near-eye display device 100 can be a virtual reality (VR) and / or augmented reality (AR) device capable of providing a VR or AR experience to a user. In a VR experience, essentially the entire visual experience is provided by the VR device's light engine. In an AR experience, the light engine is used to transmit images onto a transparent protective visor. In this way, the visual experience includes elements provided by the VR device's light engine, as well as objects that the user can visually see through the transparent visor. In the example shown herein, the near-eye display device 100 is designed for AR visualization, but a VR device could implement this using the principles illustrated.

[0032] In the illustrated embodiment, the near-eye display device 100 includes a frame 101, a transparent protective sunshade 102 mounted to the frame 101, and left and right side arms 104 mounted to the frame 101. The sunshade 102 is formed... Figure 2 Protective housings for the various display components shown.

[0033] Display component 200 that can generate images for AR / VR visualization (see...) Figure 2The display assembly 200 is also mounted to the rack 101 and enclosed within the protective sun visor 102. The sun visor assembly 102 and / or the rack 101 may also house electronics for controlling the functions of the display assembly 200 and other functions of the near-eye display device 100. The near-eye display device 100 also includes an adjustable headband 105 attached to the rack 101, through which the near-eye display device 100 can be worn on the user's head.

[0034] Figure 2 A side view is shown of a display component that may be included in a sun visor 102 of a near-eye display device 100 in some embodiments of the invention. During operation of the near-eye display device 100, the display component is positioned relative to the user's left eye 206. L Or right eye 206 R And is positioned. The display components are not mounted to the inner surface of rack 101. Rack 101 is in Figure 2 The image is shown in cross-section.

[0035] In AR applications, the display assembly is designed to overlay a 3D image onto a user's view of the real environment visible through a transparent protective sunshade 102, for example, by projecting light into the user's eyes. Therefore, the display assembly includes a display module 204 housing a light engine comprising components such as: one or more light sources (e.g., one or more light-emitting diodes (LEDs)); one or more microdisplay imagers, such as liquid crystal on silicon (LCOS), liquid crystal displays (LCDs), digital micromirror devices (DMDs); and one or more lenses, beam splitters, and / or waveguides. The microdisplay imagers (not shown) within the display module 204 can be connected via flexible circuit connectors 205 to a printed circuit board 208 on which image generation / control electronics are mounted.

[0036] The display assembly also includes a transparent waveguide carrier 201 on which the display module 204 is mounted, and one or more output waveguides 202 on the user side of the waveguide carrier 201 for each of the user's left and right eyes. Note that, ideally, embodiments can use a single waveguide to achieve the functionality described herein. The waveguide carrier 201 has a central nose bridge portion 210, from which left and right waveguide mounting surfaces of the waveguide carrier 201 extend. Waveguides 202 are implemented on each of the left and right waveguide mounting surfaces of the waveguide carrier 201 to project light emitted from the display module and representing an image to the user's left eye 206, respectively. L and right eye 206 R The display component 200 can be mounted to the rack 101 via a central tab 207 on top of the waveguide carrier 201 located above the central nose bridge portion 210.

[0037] Near-eye display devices can provide light representing an image to a user's light receiver (e.g., the eye). The user can be, for example, a person, an animal, or a machine.

[0038] Figure 3 An example of an output waveguide that can be mounted on waveguide carrier 201 to transmit light to one of a user's eyes is shown. Similar waveguides can be designed for one or more eyes, for example, as... Figure 3 The image shows a (horizontal) mirror image of the waveguide. Waveguide 310 is transparent (although diffracted), and from... Figure 2 As can be seen, waveguide 310 is typically positioned directly in front of the user's eyes during operation of near-eye display devices, for example, as... Figure 2 One of the waveguides 202 in the device. Therefore, during operation of the near-eye display device 100, waveguide 310 is shown from the user's perspective.

[0039] Waveguide 310 includes a single input port 311, which is a DOE (also known as an in-coupling element) denoted as DOE1. Input port 311 may be formed by, for example, a surface diffraction grating, a volume diffraction grating, or a reflective component.

[0040] In the example shown in this paper, input port 311 is configured to diffract the input light into two or more spectra (other spectra have some leakage), and to diffract these two or more spectra in different directions. This allows the different spectra to... Figure 3 Different paths are used on the transmission channel 312 shown.

[0041] This is Figure 4A A detailed example is shown below. Figure 4A The wave vector space representation is shown. Figure 4A The transverse wave vector space representation of the light wave diffracted by DOE1 at input port 311 in waveguide 310 is shown. The inner solid circle 401 represents the boundary of the total internal refraction (TIR) ​​condition. The outer solid circle 402 represents the boundary of the evanescent wave.

[0042] Therefore, any light wave in the annular portion between concentric circles 401 and 402 propagates in waveguide 310 via total internal reflection (TIR). Any light wave in the inner circle 401 is a wave that propagates in the waveguide and is then emitted into the air. In other words, these light waves propagate in the waveguide and then exit from it. Any light wave outside the outer circle 402 is an evanescent wave that is not coupled into the waveguide.

[0043] Figure 4A Two grating vectors of the FOV of DOE1 diffraction for DOE1 and waveguide 310 are shown. Specifically, Figure 4AThe diagram shows the DOE1 blue path, order -1; the DOE1 red path, order -1; the DOE1 red path, order +1; and the DOE1 blue path, order +1.

[0044] In some embodiments, the DOE1 may include a linear grating having a first grating orientation and period on its front side and a second grating orientation and period on its back side. The first grating may diffract light of one spectrum, and the second grating may diffract light of a second spectrum. Alternatively, the DOE1 may include a cross grating on one side of the waveguide. The grating vectors of the cross grating may have different orientations and lengths and may not be orthogonal to each other.

[0045] Refer again Figure 3 Waveguide 310 includes transmission channel 312. The transmission channel includes a DOE, referred to herein as DOE2. Note that DOE2 has several different wings, including DOE2 upper left, DOE2 upper right, DOE2 lower left, and DOE2 lower right. As previously mentioned, DOE2 includes several extended gratings. The functionality of DOE2 will be discussed below. Figures 5 to 7 Please provide a detailed explanation.

[0046] However, now referencing Figure 4B , Figure 4B The DOE2 grating vector and the FOV diffracted by DOE2 are shown.

[0047] Note that the various wings of the DOE2 can be implemented on a grating, wherein the first wing is on the front side of the grating and the second wing is on the back side of the grating. In some embodiments, these first and second wings can overlap. In some embodiments, the DOE2 can be a linear grating having the first and second wings on the front side of the waveguide. In some embodiments, the DOE2 can be a linear grating having the first and second wings on the back side of the waveguide.

[0048] Refer again Figure 3 Waveguide 310 also includes a single output port 313, which is a DOE (also known as an output coupling element) denoted as DOE3.

[0049] Now for reference Figure 4C The diagram shows the DOE3 grating vector and the FOV diffracted by DOE3.

[0050] During operation, display module 204 (see...) Figure 2 The light representing the image for the eye is output from its output port to the input port 311 of the waveguide 310.

[0051] The transmission channel 312 transmits light from the input port 311 to the output port 313 and can be, for example, a surface diffraction grating, a polarization grating, a volume diffraction grating, or a reflective component. The transmission channel 312 can be designed to achieve this by using total internal reflection (TIR). The light representing the image is then projected from the output port 313 to the user's eye.

[0052] Therefore, typically, embodiments may split the FoV of different colors into two (or more) paths, carry a portion of the FoV to DOE3 when expanding the pupil via pupil replication, and recombine the different contributions of each color at DOE3. In certain portions of the paths, the two or more paths may be identical.

[0053] The grating vectors of DOE1, DOE2, and DOE3 satisfy D1+D2+D2=0.

[0054] Specifically, for the "red" and "blue" paths, the two grating vectors of DOE1 (for +1 order) are represented by D1r and D1b, as shown in the figure above.

[0055] For the top right, bottom right, top left, and bottom left, the DOE2 grating vectors are represented by D2tr, D2br, D2tl, and D2bl, respectively.

[0056] The grating vectors of DOE3 are represented by D3b and D3r.

[0057] Then, the path equation is:

[0058] D1r+D2bl+D3r=0

[0059] -D1r+D2tr+D3r=0

[0060] D1b + D2br + D3b = 0

[0061] -D1b+D2tl+D3b=0

[0062] Figures 4A-4C An example of a k-vector diagram enabling this type of solution is given. Note that in Figure 3 In the image, a portion of the red and blue FoV appears to be leaking, but this is not necessarily the case in all embodiments.

[0063] Waveguide 310 may include multiple diffractive optical elements (DOEs) to control the direction of light propagating in a near-eye display device by multiple optical diffraction events. DOEs may be, for example, surface diffraction gratings or volumetric diffraction gratings. Various components of waveguide 310 may be designed to include one or more DOEs.

[0064] For example, waveguide 310 may include three DOEs. The input port 311 of waveguide 310 is DOE1, which is used to couple light into waveguide 310 and control the direction of the optical path after the light reaches the input port 311.

[0065] The transmission channel 312 of waveguide 310 is DOE2, which is used to control the direction of the optical path in the transmission channel 312 and ensures the propagation of light inside the transmission channel 312 by total internal reflection (TIR). In addition, DOE2 is configured to homogenize the optical signal in the horizontal direction.

[0066] Output port 313 is DOE3, which controls the direction of the optical path after the light leaves output port 313. DOE3 is configured to diffract the light into the eye-tracking range, which maintains the output propagation angle within a predetermined threshold of the input propagation angle.

[0067] The propagation directions of the extended light waves are substantially parallel to each other (within a certain predetermined threshold). The extended light waves are spaced out or distributed along a specific direction.

[0068] In other words, the extended light wave translates along a specific direction (or coordinate axis) within the output waveguide before leaving it. Each extended light wave has a relatively narrow propagation angle, or FoV range. Each extended light wave has a "propagation vector," which represents the average propagation direction of the light wave and the central axis of the extended light wave's energy. Translation of the light wave means moving the corresponding propagation vector along a specific direction (or coordinate axis) that is not parallel to the propagation vector itself.

[0069] Therefore, for any given wavelength of light, the light wave leaving the output waveguide has the same direction as the light wave entering the output waveguide (i.e., substantially parallel to it within a certain threshold), so that the light wave follows the desired path to the user's optical receiver. This condition is called achromatic imaging.

[0070] The following details the expansion of light, specifically for a single light path. However, it should be understood that the concepts shown can be applied to the different paths described above, making the expansion and summation rules applicable to every different path of light.

[0071] A waveguide containing three dots of light (DOE) can spread light waves into two dimensions. This spreading process is also known as exit pupil spreading. Figure 5 An example of an output waveguide for extending the exit pupil of a near-eye display device is shown. Waveguide 510 includes three DOEs 515, 520, and 525 to extend the exit pupil. DOEs 515, 520, and 525 are continuous in a common optical path. DOEs 515, 520, and 525 can, for example, be arranged on a planar substrate.

[0072] Imager 505 (e.g., LCOS device) outputs light wave 550 incident along the Z-direction on first DOE 515. DOE 515 directs light wave 552 to second DOE 520. For example... Figure 5 As shown, DOE 520 extends light wave 554 in the first dimension (X dimension). (As...) Figure 5 As shown, during the expansion, each propagation vector of the expanded light wave 554 moves along the X-coordinate axis, such that the expanded light waves are spaced apart or distributed in the X dimension.

[0073] DOE 520 further redirects the extended light wave 554 to a third DOE 525. The third DOE 525 further extends the light wave 554 in the second dimension (Y dimension) and redirects the extended light wave 556 outward in the Z direction.

[0074] Therefore, waveguide 510 receives the input light wave 550 incident in the Z direction, expands the light wave in both the X and Y directions, and redirects the expanded light wave in the same Z direction. In other words, waveguide 510 expands the light distribution in two dimensions while maintaining the direction of the light wave. Therefore, waveguide 510 can be referred to as a beam expander or an exit pupil expander.

[0075] Waveguides, as beam spreading devices, can spread light waves in, for example, odd-order or even-order spreading processes. Figure 6A The output waveguide for odd-order extension is shown. Waveguide 600 includes DOE 615, DOE 620, and DOE 625.

[0076] Each of the DOEs—DOE 615, DOE 620, and DOE 625—features a diffraction grating. A diffraction grating is an optical component with a periodic structure that splits and diffracts an incident light beam into several beams propagating in different directions. The periodic structure may include linear grooves arranged in a periodic pattern. The distance between nearby grooves is called the grating period, d.

[0077] A diffraction grating has the property of a grating vector D (also called a diffraction pattern vector). The grating vector D represents the direction and spacing of the grating pattern (also called a periodic diffraction pattern). The length of the grating vector is D = 2π / d. The direction of the grating vector D is perpendicular ("normal to" or "orthogonal to") to the central axis of the periodic linear groove, where the central axis is perpendicular to the cross-section of the periodic linear groove.

[0078] Light is incident on waveguide 600 along the Z direction, which is perpendicular to the X and Y directions. A first DOE 615 couples light from an imager (not shown) into waveguide 600. A second DOE 620 extends the light in the X direction. A third DOE 625 further extends the light along the Y direction and couples the extended light out of waveguide 600 along the same Z direction.

[0079] like Figure 6A As shown, the second DOE 620 receives light waves from the first DOE 615 located at the left edge of the DOE 620 (as seen in the diagram). The light waves are reflected once or multiple times by the grating pattern in the DOE 620 before exiting the DOE 620 at its bottom edge. Because odd-order extensions cause the second DOE 620 to receive light waves at its side edges, waveguides with odd-order extensions typically occupy less space than waveguides with even-order extensions (discussed later).

[0080] During the odd-order extension process, the second DOE 620 reflects (i.e., changes direction) the light an odd number of times before redirecting it to the third DOE 625. During these multiple reflections between the 0 and +1 diffraction orders, a significant portion of the light energy is converted to the +1 order, which is then redirected to the third DOE 625.

[0081] Figure 6B The wave vector of light propagating in the waveguide and the grating vector of the DOE of the waveguide are shown. The incident light has a pair of transverse wave vector components k. x0 and k y0 The magnitude of the wave vector is the wave number k = 2π / λ, where λ is the wavelength of light. The wave number of incident light in air is denoted as k0. The wave number of light propagating in a waveguide is denoted as k = k0 * n, where n is the refractive index of the waveguide material.

[0082] The raster vectors of DOE1, DOE2 and DOE3 ( Figure 6B 616, 620, and 625 in the above are represented as D j =(D xj D yj The wave vector is (D). x1 D y1 The DOE 615 will transmit the incident light (k) x0 k y0 Redirecting to the second DOE 620. Therefore, (k x1 k y1 )=(k x0 +D x1 k y0 +D y1 ).

[0083] The wave vector is (D)x2 D y2 DOE 620 receiving light (k) x1 k y1 ), and will light (k x1 k y1 Redirected to the third DOE 625. Therefore, (k x2 k y2 )=(k x1 +D x2 k y1 +D y2 )=(k x0 +D x1 +D x2 k y0 +D y1 +D y2 ).

[0084] The wave vector is (D) x3 D y3 DOE 625 receiving light (k) x2 k y2 And will light (k x2 k y2 It couples out along the Z direction. Therefore, (k x3 k y3 )=(k x2 +D x3 k y2 +D y3 )=(k x0 +D x1 +D x2 +D x3 k y0 +D y1 +D y2 +D x3 ).

[0085] Waveguide 600 satisfies the achromatic imaging condition, meaning that when light waves of different wavelengths are spread by waveguide 600 and leave waveguide 600, the exit direction of the light waves is the same as the incident direction of the light waves entering waveguide 600. In other words, the incident light wavenumber (k) x0 k y0 ) and output coupling wavenumber (k x3 k y3 Matching: (k) x0 k y0 )=(k x3 k y3 Therefore, the grating vector of waveguide 600 satisfies D. x1 +D x2 +D x3 =D y1 +Dy2 +D x3 ) = 0. Or, in vector form, the vector sum of the grating vectors is equal to zero: D1 + D2 + D2 = 0 (also known as the "summation rule").

[0086] Note that the grating vectors D1, D2, and D2 depend on the grating period, but not on the wavelength of the light wave. Therefore, once the grating vectors satisfy the summation rule, the achromatic imaging condition is satisfied for any wavelength of light (hence the name "achromatic imaging").

[0087] To meet the achromatic imaging requirements, it is not necessary to restrict the diffraction gratings of the first DOE 615 and DOE 625 to have the same grating period. The summation rule relaxes the design constraints on these diffraction gratings. This relaxed design constraint allows waveguide 600 to have a larger FoV.

[0088] Furthermore, waveguide 600 retains the light diffracted by DOE 615 and DOE 620 within waveguide 600. Therefore, the light propagating inside waveguide 600 does not disappear and satisfies the total internal reflection (TIR) ​​condition. In other words, the light diffracted by DOE 615 satisfies the TIR condition inside the waveguide: k x1 2 +k y1 2 >k0 2 The light diffracted by DOE 615 is not hidden: k x1 2 +k y1 2 <k 2 The light diffracted by DOE620 also satisfies the TIR condition inside the waveguide: k x2 2 +k y2 2 >k0 2 The light diffracted by DOE 620 is not hidden: k x2 2 +k y2 2 <k 2 .

[0089] although Figure 6A and 6B A waveguide with three DOEs is shown, but a waveguide according to the disclosed technique can have any number of DOEs. For example, if the waveguide includes N DOEs, the achromatic imaging condition is D. x1 +D x2 +D x3 +…+D xN =D y1 +D y2 +Dx3 +…+D yN = 0. Or, in vector form: D1 + D2 + D2 + ... + D N =0. DOE also satisfies these conditions for TIR and is non-hidden.

[0090] In some embodiments, the achromatic imaging condition can be expressed as a weighted vector sum of grating vectors: mD1 + nD2 + lD3 = 0, where the values ​​m, n, and l in the addends are integer weight values ​​that represent the diffraction order in which the periodic diffraction pattern is designed to concentrate light energy. In some embodiments, the integer weight values ​​can be 0, negative, or positive.

[0091] In addition, waveguides, as beam spreading devices, can also spread light waves during even-order spreading processes. Figure 7 The output waveguide for even-order extension is shown. Waveguide 700 includes DOE 715, DOE 720, and DOE 725.

[0092] Light is incident on waveguide 700 along the Z direction, which is perpendicular to the X and Y directions. A first DOE 715 couples the light into waveguide 700 and redirects the light wave to a second DOE 720 at the top edge of DOE 720. The second DOE 720 extends the light in the X direction. A third DOE 725 further extends the light in the Y direction and couples the extended light out of waveguide 700 along the same Z direction.

[0093] like Figure 7 As shown, the second DOE 720 receives light waves from the first DOE 715 at the top edge of the DOE 520. Note that, as... Figure 6A In the odd-order extension shown, the second DOE 520 receives light waves at its left edge. The choice between odd-order or even-order extensions depends on various waveguide design factors. Generally, waveguides with odd-order extensions tend to be smaller. On the other hand, even-order extensions allow light waves to be delivered at the top edge of the second DOE, which can be advantageous when the waveguide width is limited.

[0094] Before the light wave leaves the DOE 720 at its bottom edge, it is reflected multiple times by the grating pattern within the DOE 720. During even-order extension, the second DOE 720 reflects the light an even number of times (including zero times) before redirecting it to the third DOE 725. Similar to odd-order extension, during the multiple reflections between orders 0 and +1, more light energy is converted to the +1 order, which is then redirected to the third DOE 725.

[0095] like Figure 7As shown, the second DOE 720 extends the light wave along the X-direction. However, the second DOE 720 maintains the same direction of its output light as its input light. In other words, in even-order expansion, the wave vectors of the light waves before and after the second DOE 720 are the same. Therefore, the grating vector of the diffraction grating of the second DOE 720 does not restrict the diffraction vectors of the other DOEs in the waveguide 700.

[0096] In even-order extensions, the first DOE 715 may have, for example, linear diffraction gratings (also known as "double-sided linear gratings") on both sides of the DOE 715. The grating vector of the first diffraction grating on the first side (e.g., the top side) of the DOE 715 is D. 1a =(D x1a D y1a The grating vector of the second diffraction grating on the second side (e.g., the bottom side) of the DOE715 is D. 1b =(D x1b D y1b The grating vector of the third DOE 725 diffraction grating is D3 = (D x3 D y3 )

[0097] Waveguide 700 satisfies the achromatic imaging condition, which means that the incident light (k x0 k y0 ) and emitted light (k x3 k y3 ) matches. If mD 1a +nD 1b = ±D3, where m and n are integer orders, then the achromatic imaging condition is satisfied.

[0098] In some embodiments, the achromatic imaging condition can be expressed as a weighted vector sum of grating vectors: mD 1a +nD 1b +lD3 = 0, where the values ​​m, n, and l in the addends are integer weight values ​​that represent the diffraction order in which the periodic diffraction pattern is designed to concentrate light energy (also known as the "weighted summation rule"). In some embodiments, the integer weight values ​​can be 0, -1, or +1. Higher diffraction orders corresponding to integers with absolute values ​​greater than 1 are typically suppressed by the grating pattern.

[0099] In some embodiments, m = 1 and n = 0, or m = 0 and n = 1. Therefore, the first DOE 715 has a diffraction grating with wave vectors D1 = ±D3. In other words, the achromatic imaging condition is satisfied if the first DOE 715 and the third DOE 725 have the same length (or the same grating period) for the grating vectors.

[0100] Since the grating periods of the first DOE 715 and the third DOE 725 do not need to be equal, the design constraints on the grating vectors can be relaxed. In some embodiments, m = 1 and n = 1, which means that the first diffraction grating of the first DOE 715 reflects the light wave to the +1 diffraction order, and then the second diffraction grating of the first DOE 715 reflects the light wave to the +1 diffraction order again. Diffraction orders above the +1 diffraction order are generally less efficient and produce ghosting effects. Therefore, when m = 1 and n = 1, the vector sum of the grating vectors of the first DOE 715 diffraction grating is equal to, or exactly the opposite of, the grating vector of the third DOE 725: D 1a +D 1b = ±D3. Specifically, in the case of -D3, the first and second diffraction gratings of the first DOE 715 and the diffraction grating of the third DOE 725 satisfy the summation rule: D 1a +D 1b +D3=0.

[0101] In addition to the double-sided linear grating, the first DOE 715 may also have, for example, crossed diffraction gratings (also called "double-sided crossed gratings") on both sides of the DOE 715. Therefore, the first DOE 715 effectively comprises four diffraction gratings with four grating vectors. On the first side (e.g., the top side) of the first DOE 715, there are gratings that intersect each other and have a grating vector of D. 1a =(D x1a D y1a ) and D 1b =(D x1b D y1b Two diffraction gratings exist on the first side. In other words, the grating pattern is periodic in two directions on the first side. On the second side (e.g., the bottom side) of the first DOE 715, there are gratings that intersect each other and the grating vector is D. 1c =(D x1c D y1c ) and D 1d =(D x1d D y1d Two diffraction gratings.

[0102] Waveguide 700 satisfies the achromatic imaging condition, meaning the incident light and the outgoing light are matched. If mD 1a +nD 1b +oD 1a +pD 1b = ±D3, where m, n, o and p are integer orders, then the achromatic imaging condition is satisfied.

[0103] Therefore, the weighted vector summation rule can be used to design the DOE (Design of Output) waveguide. The diffraction grating of the DOE follows the summation rule or the weighted summation rule, and thus satisfies the achromatic imaging order. The summation rule or the weighted summation rule allows for a loose degree of freedom to design the configuration of output waveguides with various characteristics of the DOE.

[0104] The following discussion now involves the many methods and method actions that can be performed. Although method actions may be discussed in a specific order or shown in a specific order in a flowchart, a specific order is not required unless specifically stated or because an action depends on another action being performed before it is performed.

[0105] Now for reference Figure 8 Method 800 is illustrated. Method 800 includes actions for combining RGB optical signals in a single waveguide. The waveguide includes multiple optical distributions (DOEs). The method includes guiding the optical signal at an input propagation angle at a first DOE (action 802).

[0106] Method 800 further includes diffracting the optical signal at the first DOE based on the spectrum, such that the light of one spectrum is diffracted mainly in a first direction and the light of a second spectrum is diffracted mainly in different second directions, so that different parts of the different optical signals take different paths including at least two different paths (action 804).

[0107] Method 800 also includes diffracting the different portions at the first DOE into the second DOE (action 806).

[0108] Method 800 also includes diffracting the different portions into a third DOE at the second DOE (808).

[0109] Method 800 further includes extending the optical signal in a substantially non-parallel manner at the second and third DOEs; the extension at DOE2 and DOE3 is substantially non-parallel. For example, an embodiment may extend the pupil substantially vertically at DOE2 during the out-coupling process and then extend the pupil horizontally at DOE3 (action 810).

[0110] Method 800 also includes diffracting different portions at the third DOE into an eye-tracking range that maintains the output propagation angle within a predetermined threshold of the input propagation angle. That is, an attempt is made to keep the output propagation angle substantially parallel to the input propagation angle to prevent distortion and / or other side effects (Action 812).

[0111] Multiple DOEs are associated with raster vectors. The action of method 800 is performed such that the sum of the raster vectors for each of at least two different paths is substantially equal to zero (action 814).

[0112] Note that "nearly equal to zero" depends on the device's display resolution. Specifically, as long as a certain predefined resolution is maintained, the sum is essentially equal to zero. In some embodiments, this may mean that the output resolution of the outgoing optical signal must be the same as the input resolution of the incoming optical signal.

[0113] Method 800 can be practiced, wherein the optical signal is diffracted based on the spectrum such that the light of one spectrum is diffracted mainly in a first direction and the light of a second spectrum is diffracted mainly in different second directions such that different parts of the optical signal take different paths including at least two different paths, which is performed by a first DOE having a linear grating associated with a first grating vector on the front side of the grating and a second grating vector on the back side of the waveguide.

[0114] Method 800 can be practiced, in which the diffraction of different portions into an eye-tracking range that keeps the output propagation angle within a predetermined threshold of the input propagation angle is performed by a third DOE, which is a linear grating having a first grating vector on the front side of the waveguide and a second grating vector on the back side of the waveguide.

[0115] Method 800 can be practiced, in which the optical signal is extended in a substantially non-parallel manner and the different portions are diffracted into a third DOE by a second DOE, the second DOE comprising a linear grating having a first wing on the front side of the waveguide and a second wing on the back side of the waveguide, wherein the first wing and the second wing overlap.

[0116] Method 800 can be practiced, in which the optical signal is extended in a substantially non-parallel manner and the different portions are diffracted into a third DOE, which is performed by a second DOE comprising a linear grating having a first wing and a second wing on the front side of the waveguide.

[0117] Method 800 can be practiced, in which the optical signal is extended in a substantially non-parallel manner and the different portions are diffracted into a third DOE, which is performed by a second DOE comprising a linear grating having a first wing and a second wing on the back side of the waveguide.

[0118] Method 800 can be practiced, wherein the optical signal is diffracted based on the spectrum such that the light of one spectrum is diffracted mainly in a first direction and the light of a second spectrum is diffracted mainly in a different second direction, such that different parts of the optical signal take different paths including at least two different paths, which is performed by a first DOE having a cross grating associated with two dissimilar grating vectors.

[0119] Method 800 can be practiced, in which the optical signal is extended in a substantially non-parallel manner and the different portions are diffracted into a third DOE, which is performed by a second DOE having a cross grating associated with two dissimilar grating vectors.

[0120] Method 800 can be practiced, in which the diffraction of different portions into an eye-tracking range that keeps the output propagation angle within a predetermined threshold of the input propagation angle is performed by a third DOE having a cross grating associated with two dissimilar grating vectors.

[0121] The invention may be practiced in other specific forms without departing from the spirit or characteristics thereof. The described embodiments should be considered illustrative rather than restrictive in all respects. Therefore, the scope of the invention is indicated by the appended claims rather than the foregoing description. All modifications falling within the equivalent meaning and scope of the claims should be included within their scope.

Claims

1. An optical device, comprising: A single waveguide plate, the single waveguide plate comprising: The first DOE includes an in-line coupling element having at least two periods and orientations; A second DOE, optically coupled to the first DOE, the second DOE comprising a plurality of extended gratings, wherein at least one extended grating comprises a plurality of different wings, such that the second DOE comprises four different extended wings; and A third DOE, optically coupled to the second DOE, directs the output from the four different extended wings into the third DOE, the third DOE comprising an output coupling grating having at least two periods and orientations. The first DOE is configured to receive an optical signal at an input propagation angle and diffract the optical signal to at least two different paths based on the spectrum. The first DOE, the second DOE, and the third DOE are associated with grating vectors, and for each of the at least two different paths, the sum of the grating vectors of the corresponding wings of the first DOE, the second DOE, and the third DOE is substantially equal to zero.

2. The optical device of claim 1, wherein at least one of the first DOE and the third DOE comprises a linear grating associated with a first grating vector on the front side of the waveguide plate and a second grating vector on the back side of the waveguide plate.

3. The optical device of claim 1, wherein the second DOE comprises a linear grating having a first wing on the front side of the waveguide plate and a second wing on the back side of the waveguide plate, wherein the first wing and the second wing overlap.

4. The optical device according to claim 1, wherein the plurality of wings are linear gratings.

5. The optical device according to claim 1, wherein the first and second wings of the second DOE belong to a linear grating on the back side of the waveguide plate.

6. The optical device of claim 1, wherein the second DOE comprises a cross grating associated with two dissimilar grating vectors.

7. The optical device of claim 1, wherein the third DOE comprises a cross grating associated with two dissimilar grating vectors.

8. A method for displaying a large field of view in a near-eye display device, the method comprising: The light from the optical engine is directed to a first DOE on a single waveguide plate. The first DOE includes an ingress coupling element having an orientation that causes at least two different spectra of the light wavelength to be diffracted in different directions by at least two periods. The light is directed from the first DOE to a second DOE of the single waveguide plate optically coupled to the first DOE. The second DOE includes a plurality of extended gratings, wherein at least one of the extended gratings includes a plurality of different wings, such that the second DOE includes four different extended wings, thereby causing an expansion of the exit pupil by pupil replication for at least one spectrum of light wavelength. as well as The light is directed from the four different extension wings of the second DOE to a third DOE of the single waveguide plate, the third DOE being optically coupled to the second DOE, the third DOE including an output coupling grating having at least two periods and orientations that cause the different spectral recombination of the light wavelengths. Specifically, the first DOE receives the optical signal at an input propagation angle and diffracts the optical signal onto at least two different paths based on the spectrum. The first DOE, the second DOE, and the third DOE are associated with grating vectors, and for each of the at least two different paths, the sum of the grating vectors of the corresponding wings of the first DOE, the second DOE, and the third DOE is substantially equal to zero.

9. The method of claim 8, wherein the first DOE comprises a linear grating associated with a first grating vector on the front side of the waveguide plate and a second grating vector on the back side of the waveguide plate, such that the first grating vector on the front side of the waveguide plate and the second grating vector on the back side of the waveguide plate are used to perform diffraction of at least two different spectra of light wavelengths in different directions.

10. The method of claim 8, wherein the third DOE comprises a linear grating associated with a first grating vector on the front side of the waveguide plate and a second grating vector on the back side of the waveguide plate, such that the first grating vector on the front side of the waveguide plate and the second grating vector on the back side of the waveguide plate are used to perform the recombination of the different spectra of optical wavelengths.

11. The method of claim 8, wherein the second DOE comprises an extended grating having a first wing on the front side of the waveguide plate and a second wing on the back side of the waveguide plate, such that the first wing on the front side of the waveguide plate and the second wing on the back side of the waveguide plate are used to perform pupil replication.

12. The method of claim 8, wherein the plurality of wings of the second DOE are linear gratings, such that pupil replication is performed using the linear gratings.

13. The method of claim 8, wherein the first and second wings of the second DOE belong to a linear grating on the back side of the waveguide plate, such that the linear grating on the back side of the waveguide plate is used to perform pupil replication.

14. The method of claim 8, wherein the third DOE comprises a cross grating associated with two dissimilar grating vectors, such that the cross grating associated with the two dissimilar grating vectors is used to perform the recombination of the different spectra of light wavelengths.

15. A near-eye optical device, comprising: Light engine; A single waveguide plate, optically coupled to the optical engine, the single waveguide plate comprising: The first DOE includes an in-line coupling element having at least two periods and orientations; A second DOE, optically coupled to the first DOE, the second DOE comprising a plurality of extended gratings, wherein at least one extended grating comprises a plurality of different wings, such that the second DOE comprises four different extended wings; and A third DOE, optically coupled to the second DOE, directs the output from the four different extended wings into the third DOE, the third DOE comprising an output coupling grating having at least two periods and orientations. The first DOE is configured to receive an optical signal at an input propagation angle and diffract the optical signal to at least two different paths based on the spectrum. The first DOE, the second DOE, and the third DOE are associated with grating vectors, and for each of the at least two different paths, the sum of the grating vectors of the corresponding wings of the first DOE, the second DOE, and the third DOE is substantially equal to zero.

16. The near-eye optical device of claim 15, wherein the first DOE comprises a single-sided cross grating.

17. The near-eye optical device of claim 15, wherein the first DOE includes a reflective component.

18. The near-eye optical device of claim 15, wherein the plurality of wings are linear gratings.

19. The near-eye optical device of claim 15, wherein the first and second wings of the second DOE belong to a linear grating on the back side of the waveguide plate.

20. The near-eye optical device of claim 15, wherein the third DOE comprises a cross grating associated with two dissimilar grating vectors.

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