Waveguide display system with wide field of view

Abstract

Implementations include optical systems that can be included in waveguide displays. An example optical system includes a first waveguide having a first transmissive diffractive in-coupler (DG1) and a first diffractive out-coupler (DG6), and a second waveguide having a second transmissive diffractive in-coupler (DG2), a reflective diffractive in-coupler (DG3), a second diffractive out-coupler (DG4), and a third diffractive out-coupler (DG5). The second transmissive diffractive in-coupler (DG2) is disposed between the first transmissive diffractive in-coupler (DG1) and the reflective diffractive in-coupler (DG3) in an input region.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to European Patent Application No. 20315042.0, filed on March 23, 2020, entitled “Waveguide Display System with Wide Field of View”, and European Patent Application No. 20315216.0, filed on April 23, 2020, entitled “Full-Color Waveguide Combiner”, both of which are incorporated herein by reference in their entirety. Background Technology

[0003] This disclosure relates to the fields of optics and photonics, and more specifically to optical devices comprising at least one diffraction grating. It can be applied in the field of conformal and wearable optics (e.g., AR / VR glasses (augmented reality / virtual reality)) and in a variety of other consumer electronics products including displays and / or lightweight imaging systems (including head-up displays (HUDs)), such as in the automotive industry.

[0004] This section is intended to introduce the reader to various aspects of the art that may relate to the various aspects of this disclosure described below and / or claimed. This discussion is intended to help provide the reader with background information to facilitate a better understanding of the various aspects of the systems and methods described herein. Therefore, it should be understood that these statements should be interpreted in this context, rather than as an admission of prior art.

[0005] AR / VR glasses are considered the next generation of human-computer interfaces. The development of AR / VR glasses (and more generally, protective electronic devices for glasses) is associated with many challenges, including reducing the size and weight of such devices and improving image quality (in terms of contrast, field of view, color depth, etc.) to achieve a truly immersive user experience.

[0006] The trade-off between image quality and physical size in optics has spurred research into ultracompact optical components that could serve as building blocks for more complex optical systems, such as AR / VR glasses. It is hoped that such optical components will be easy to manufacture and replicate.

[0007] In such AR / VR glasses, various types of refractive and diffractive lenses and beamforming components are used to guide light from a microdisplay or projector to the human eye, thereby allowing the formation of virtual images that are superimposed on the physical world seen with the naked eye (in the case of AR glasses) or captured by a camera (in the case of VR glasses).

[0008] Some types of AR / VR glasses utilize optical waveguides, where light propagates into the waveguide only within a limited internal angle range via TIR (Total Internal Reflection). The FoV (Field of View) of the waveguide depends on the waveguide material and other factors.

[0009] The FoV of a waveguide can be expressed as the value of the waveguide propagating through the TIR. The maximum span. In some cases, such as Figure 17 As shown, the maximum angular span that can be coupled into a waveguide can be expressed by two rays: one with an incident angle of incidence. Critical ray ( Figure 17 In ) and having an angle of incidence Grazing rays ( Figure 17 In The critical ray is just the right distance from the critical ray. Limited critical angle The light rays diffracted into the waveguide, where n² is the refractive index of the waveguide material and λ is the wavelength of the incident light. Above the critical angle. Total internal reflection (TIR) ​​occurs. A grazing ray is a ray with an input angle that can be... The grazing incident diffracted into the waveguide. The theoretical FoV of the waveguide presented above is for a single-mode system, where a single diffraction mode is used to carry the image: +1 or -1 diffraction mode.

[0010] In some systems based on optical waveguides, the field of view is limited by the angular bandwidth of the glass plate. If we diffract a mode into the glass plate, we obtain the FoV as a function of the refractive index of the glass material. The FoV of a waveguide with a refractive index of n² is given by the following equation:

[0011] Figure 18 A diagram showing a reasonable range for n2 is presented. For n2 = 1.5, the total field of view of a single-mode system is more precisely limited to Δθ1 = 28.96 degrees. It can be seen that 60 degrees FoV is a practical limitation for some types of waveguides, as it is generally not feasible to use materials with a refractive index higher than 2.0.

[0012] By utilizing a second propagation direction within the waveguide, the field of view of the optical waveguide can be further expanded, effectively doubling the field of view.

[0013] For example, WO2017180403 proposes a waveguide with an extended field of view, employing dual-mode image propagation. In this method, the +1 diffraction mode is used to carry the right-hand side image (negative incident angle at the in-coupler) in one direction, and the -1 mode is used to propagate the positive incident angle in the opposite direction within the waveguide. In WO2017180403, these two half-images are combined due to a pupil dilator and an out-coupler at the waveguide exit, allowing the user to see a single image. The goal of this system is to double the field of view, as each half-image can utilize the entire angular bandwidth of the waveguide in each propagation direction.

[0014] EP18215212.4 (“An optical device comprising at least one diffraction grating having a grating pitch above the wavelength”, O. Shramkova, V. Drazic) discloses an optical waveguide comprising a diffraction grating configured to diffract light of at least one given wavelength onto the optical waveguide. The diffraction grating has a grating spacing higher than the at least one given wavelength and is configured to diffract the incident light with a diffraction order |M|>1, where M is the diffraction order.

[0015] Using a diffraction order higher than 1 has the effect of multiplying the wavelength by the diffraction order used in the diffraction equation. Since the grating spacing is directly a function of the product Mλ, this means the grating spacing is multiplied by M. EP18215212.4 shows a much larger structure for the internal coupler and opens up new possibilities in fabrication techniques because nanoimprinting can be used. Grating densities with lower line-to-millimeter ratios can be used, and the fabrication process can be simplified by using ultrawavelength structures instead of subwavelength structures.

[0016] Also shown in EP18215212.4 is an optical waveguide with ±2 diffraction orders providing a FoV of approximately 60°, where the refractive index is 1.5. Therefore, it is possible to obtain a 60° field of view using a material with a refractive index of 1.5 instead of 2 in the single mode.

[0017] However, 60° FoV is still limited relative to the total human field of vision, in which stereoscopic vision is effective for human vision and is approximately 114°.

[0018] Two waveguide full RGB combiner architectures have been studied, in which the green FoV is shared between the first and second waveguides, as described in BCKress, “Optical waveguide combiners for AR headsets: features and limitations,” Proc. of SPIE, Vol. 11062, p. 110620J, 2019. Summary of the Invention

[0019] The terms "an embodiment," "implementation," or "exemplary embodiment" used in the specification describe embodiments that may include specific features, structures, or characteristics; however, not every embodiment necessarily includes specific features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same embodiment. Additionally, when a specific feature, structure, or characteristic is described in conjunction with an embodiment, such feature, structure, or characteristic may be used in conjunction with other embodiments, whether or not it is explicitly described.

[0020] In some embodiments, the optical system includes: a first waveguide having a first transmission diffraction inner coupler (DG1); a second waveguide having a second transmission diffraction inner coupler (DG2) and a reflection diffraction inner coupler (DG3); wherein the second transmission diffraction inner coupler (DG2) is arranged in the input region between the first transmission diffraction inner coupler (DG1) and the reflection diffraction inner coupler (DG3).

[0021] In some such implementations, the first waveguide further includes a first diffractive external coupler (DG6), and the second waveguide further includes a second diffractive external coupler (DG4) and a third diffractive external coupler (DG5).

[0022] In some implementations, the optical system is configured such that blue light: (i) preferentially couples into a first waveguide at a relatively high incident angle, and (ii) preferentially couples into a second waveguide at a relatively low incident angle.

[0023] In some implementations, the optical system is configured such that green light: (i) preferentially couples into a first waveguide at a relatively high incident angle, and (ii) preferentially couples into a second waveguide at a relatively low incident angle.

[0024] In some embodiments, the optical system is configured such that red light: (i) preferentially couples into the second waveguide via the second transmission diffraction inner coupler at a relatively high incident angle, and (ii) preferentially couples into the second waveguide via the reflection diffraction inner coupler at a relatively low incident angle.

[0025] In some implementations, the optical system is configured to substantially reproduce an image spanning a field of view of at least 100°.

[0026] In some implementations, the system is configured to reproduce panchromatic images.

[0027] In some implementations, the first diffraction inner coupler has a first grating spacing, the second diffraction inner coupler has a second grating spacing greater than the first grating spacing, and the reflection diffraction inner coupler has a third grating spacing greater than the second grating spacing.

[0028] In some of the optical systems described in the implementation schemes

[0029]

[0030] Where d1 is the grating spacing of the first transmission diffraction inner coupler (DG1), M1 is a non-zero integer (e.g., 1 or 2), n2 is the refractive index of the first waveguide, and λ is the wavelength between 450 nm and 700 nm. It is an angle between 55 degrees and 90 degrees, and It is essentially equal to the angle diffracted at the critical angle of the second waveguide, where the critical angle of the second waveguide is arcsin(1 / n3), and n3 is the refractive index of the first waveguide.

[0031] In some of the optical systems described in the implementation schemes

[0032]

[0033] Where d2 is the grating spacing of the second transmission diffraction inner coupler (DG2), M2 is a non-zero integer (e.g., 1 or 2), n3 is the refractive index of the second waveguide, and λ is the wavelength between 450 nm and 700 nm. It is an angle between 55 degrees and 90 degrees, and It is the angle within ±5 degrees of normal incidence.

[0034] In some of the optical systems described in the implementation schemes

[0035]

[0036] Where d3 is the grating spacing of the reflection diffraction inner coupler (DG3), N is a non-zero integer (e.g., 1 or 2), n3 is the refractive index of the second waveguide, and λ is the wavelength between 450 nm and 700 nm. It is an angle between 55 degrees and 90 degrees, and It is the angle within ±5 degrees of normal incidence.

[0037] In some embodiments, the optical system is a dual-mode system configured to: (i) couple at least some incident light having a first incident angle to travel in a first direction in at least one of a first waveguide and a second waveguide, and (ii) couple at least some incident light having a second incident angle substantially opposite to the first incident angle to travel in a second direction substantially opposite to the first direction in at least one of the first waveguide and a second waveguide.

[0038] In some embodiments of the optical system, the first grating spacing (d1) of the first transmission diffraction inner coupler is between 420 nm and 520 nm; the second grating spacing (d2) of the second transmission diffraction inner coupler is between 600 nm and 700 nm; and the third grating spacing (d3) of the reflection diffraction inner coupler is between 720 nm and 820 nm.

[0039] In some embodiments of the optical system, the first grating spacing (d1) of the first transmission diffraction inner coupler is between 460 nm and 480 nm; the second grating spacing (d2) of the second transmission diffraction inner coupler is between 640 nm and 660 nm; and the third grating spacing (d3) of the reflection diffraction inner coupler is between 760 nm and 780 nm.

[0040] In some embodiments of this optical system, the second grating spacing is between 30% and 50% larger than the first grating spacing; and the third grating spacing is between 10% and 30% larger than the second grating spacing.

[0041] In some embodiments, a method of operating an optical system includes: directing input light representing an image onto a first transmission diffraction inner coupler (DG1) of a first waveguide, the first waveguide having a first diffraction outer coupler (DG6); coupling a first portion of the input light into the first waveguide using the first transmission diffraction inner coupler (DG1); coupling a second portion of the input light into a second waveguide using a second transmission diffraction inner coupler (DG2) of a second waveguide; and coupling a third portion of the input light into the second waveguide using a reflection diffraction inner coupler (DG3) of the second waveguide.

[0042] In some such embodiments, the method further includes: coupling at least a portion of a first portion of light out of the first waveguide using a first diffraction external coupler (DG6) on the first waveguide; coupling at least a portion of a second portion of light out of the second waveguide using a second diffraction external coupler (DG4) on the second waveguide; and coupling at least a portion of a third portion of light out of the second waveguide using a third diffraction external coupler (DG5) on the second waveguide. Attached Figure Description

[0043] Figure 1AThis is a schematic diagram of the cross-section of a waveguide display.

[0044] Figure 1B This is a schematic diagram of a binocular waveguide display with a first layout featuring diffractive optical components.

[0045] Figure 1C This is a schematic diagram of a binocular waveguide display with a second layout featuring diffractive optical components.

[0046] Figure 1D This is a schematic exploded view of a dual-waveguide display based on some implementation schemes.

[0047] Figure 1E This is a cross-sectional schematic diagram of a dual-waveguide display according to some implementation schemes.

[0048] Figures 2A to 2C The field of view of an exemplary waveguide is shown.

[0049] Figure 3 This is a schematic side view of a portion of a dual-waveguide display according to some embodiments, showing the angles of the incident and diffracted light.

[0050] Figures 4A to 4B This is a schematic side view of the input pupil region of the second waveguide in a dual-waveguide display.

[0051] Figure 5 This is a schematic side view of a portion of a dual-waveguide display according to some implementation schemes.

[0052] Figures 6A to 6C It is based on some implementation schemes that show blue light ( Figure 6A ), green light ( Figure 6B ) and red light ( Figure 6C A schematic diagram of a waveguide coupled to a dual-waveguide display with a wide field of view.

[0053] Figure 7 It is a graph showing the angular range of incident light coupled to the first waveguide of a dual-waveguide display in some embodiments for blue, green, and red light.

[0054] Figure 8 It is a graph showing the angular range of incident light coupled to the first waveguide of a dual-waveguide display in some embodiments for blue, green, and red light.

[0055] Figures 9A to 9D This is a cross-sectional view illustrating an example of an element of a diffraction grating structure that can be used as an inner and / or outer coupler in some implementations.

[0056] Figure 10 The refractive index of TiO2 for different wavelengths is shown.

[0057] Figure 11 This is a cross-sectional view of the basic type of the metallized U-shaped element of the coupler within the reflective grating.

[0058] Figure 12A The image shows TM-polarized green light with a wavelength of 530 nm using methods such as... Figure 9A The reflectivity and transmittance of different diffraction orders of the transmission diffraction inner coupler in the first waveguide of the twin diffraction grating are shown.

[0059] Figure 12B The TE-polarized green light with a wavelength of 530 nm was shown by using, for example Figure 9A The reflectivity and transmittance of different diffraction orders of the transmission diffraction inner coupler in the first waveguide of the twin diffraction grating are shown.

[0060] Figure 12C The image shows TM-polarized green light with a wavelength of 530 nm using methods such as... Figure 9B The reflectivity and transmittance of the transmission diffraction inner coupler of the second waveguide of the U-shaped diffraction grating are shown.

[0061] Figure 12D The TE-polarized green light with a wavelength of 530 nm was shown by using, for example Figure 9B The reflectivity and transmittance of the transmission diffraction inner coupler in the second waveguide of the U-shaped diffraction grating are shown.

[0062] Figure 12E The image shows TM-polarized green light with a wavelength of 530 nm using methods such as... Figure 9A The reflectivity and transmittance of the transmission diffraction inner coupler of the second waveguide of the twin diffraction grating are shown.

[0063] Figure 12F The TE-polarized green light with a wavelength of 530 nm was shown by using, for example Figure 9A The reflectivity and transmittance of the transmission diffraction inner coupler in the second waveguide of the twin diffraction grating are shown.

[0064] Figure 13A This demonstrates how TM polarized blue light with a wavelength of 460 nm is produced using methods such as... Figure 9A The reflectivity and transmittance of different diffraction orders of the transmission diffraction inner coupler in the first waveguide of the twin diffraction grating are shown.

[0065] Figure 13B This demonstrates how TE-polarized blue light with a wavelength of 460 nm is produced by using methods such as... Figure 9A The reflectivity and transmittance of different diffraction orders of the transmission diffraction inner coupler in the first waveguide of the twin diffraction grating are shown.

[0066] Figure 13C This demonstrates how TM polarized blue light with a wavelength of 460 nm is produced by using, in some implementations, such as... Figure 9B The reflectivity and transmittance of the transmission diffraction inner coupler of the second waveguide of the U-shaped diffraction grating are shown.

[0067] Figure 13D This demonstrates how TE-polarized blue light with a wavelength of 460 nm is produced by using methods such as... Figure 9B The reflectivity and transmittance of the transmission diffraction inner coupler in the second waveguide of the U-shaped diffraction grating are shown.

[0068] Figure 13E This demonstrates how TM polarized blue light with a wavelength of 460 nm is produced using methods such as... Figure 9A The reflectivity and transmittance of the transmission diffraction inner coupler of the second waveguide of the twin diffraction grating are shown.

[0069] Figure 13F This demonstrates how TE-polarized blue light with a wavelength of 460 nm is produced by using methods such as... Figure 9A The reflectivity and transmittance of the transmission diffraction inner coupler in the second waveguide of the twin diffraction grating are shown.

[0070] Figure 14A The TM polarized red light with a wavelength of 625 nm was shown by using, for example Figure 9A The reflectivity and transmittance of different diffraction orders of the transmission diffraction inner coupler in the first waveguide of the twin diffraction grating are shown.

[0071] Figure 14B The image shows TE-polarized red light with a wavelength of 625 nm using methods such as... Figure 9A The reflectivity and transmittance of different diffraction orders of the transmission diffraction inner coupler in the first waveguide of the twin diffraction grating are shown.

[0072] Figure 14C This demonstrates how TM-polarized red light with a wavelength of 625 nm is transmitted through some implementations using, for example... Figure 9B The reflectivity and transmittance of the transmission diffraction inner coupler of the second waveguide of the U-shaped diffraction grating are shown.

[0073] Figure 14D The image shows TE-polarized red light with a wavelength of 625 nm using methods such as... Figure 9B The reflectivity and transmittance of the transmission diffraction inner coupler in the second waveguide of the U-shaped diffraction grating are shown.

[0074] Figure 14E The TM polarized red light with a wavelength of 625 nm was shown by using, for example Figure 9AThe reflectivity and transmittance of the transmission diffraction inner coupler of the second waveguide of the twin diffraction grating are shown.

[0075] Figure 14F The image shows TE-polarized red light with a wavelength of 625 nm using methods such as... Figure 9A The reflectivity and transmittance of the transmission diffraction inner coupler in the second waveguide of the twin diffraction grating are shown.

[0076] Figure 14G The TM polarized red light with a wavelength of 625 nm was shown by using, for example Figure 9D The reflectivity and transmittance of the second waveguide of the twin diffraction grating shown are different diffraction orders of the internal coupler.

[0077] Figure 14H The image shows TE-polarized red light with a wavelength of 625 nm using methods such as... Figure 9D The reflectivity and transmittance of the different diffraction orders of the reflective diffraction inner coupler in the second waveguide of the twin diffraction grating are shown.

[0078] Figure 14I The TM polarized red light with a wavelength of 625 nm was shown by using, for example Figure 9C The reflectivity and transmittance of the different diffraction orders of the reflection diffraction inner coupler of the second waveguide of the U-shaped diffraction grating are shown.

[0079] Figure 14J The image shows TE-polarized red light with a wavelength of 625 nm using methods such as... Figure 9C The reflectivity and transmittance of different diffraction orders of the reflective diffraction inner coupler in the second waveguide of the U-shaped diffraction grating are shown.

[0080] Figure 15 This is a schematic diagram showing a portion of the field of view propagating through the second waveguide at a relatively low incident angle.

[0081] Figure 16 This is a schematic diagram showing a portion of the field of view propagating through the second waveguide at a relatively high incident angle.

[0082] Figure 17 This is a schematic diagram of a single-mode system, in which a single diffraction mode is used to carry the image using either a +1 or -1 diffraction mode.

[0083] Figure 18 This is an exemplary graph showing the waveguide's field of view as a function of the refractive index of its material.

[0084] Figure 19 It is a cross-sectional side view of a lens system that provides a true exit pupil.

[0085] Figure 20This is a cross-sectional side view of a lens system suitable for use in some implementation schemes.

[0086] Figure 21 It is a cross-sectional view of a symmetrical diffraction grating.

[0087] Figure 22 This is a cross-sectional view of another symmetrical diffraction grating.

[0088] Figure 23 It is a cross-sectional view of an inclined diffraction grating.

[0089] Figure 24 The application of symmetrical diffraction with asymmetric gratings using two different diffraction gratings is shown.

[0090] Figure 25 It schematically shows the target Figure 24 The typical diffraction efficiency of a grating is a function of the incident angle.

[0091] Figure 26A It is a cross-sectional view of the profile of a diffraction grating, as used in some implementations.

[0092] Figure 26B Is it used as Figure 26A A schematic diagram of the grating profile in the image coupling light across different incident angles.

[0093] Figure 27 This is a schematic side view of the waveguide used in some implementation schemes.

[0094] Figures 28A to 28B This is a schematic side view of a single-waveguide internally coupled system, showing an example of a transmission diffraction grating. Figure 28A ) and reflection diffraction grating ( Figure 28B The angle between the incident light and the diffracted light.

[0095] Figures 29A to 29C The angles at which blue (29A), green (29B), and red (29C) light are incident on and diffracted in a single waveguide system are schematically shown.

[0096] Figures 30A to 30C A cross-sectional view of the basic configuration of the transmission (30A) diffraction grating and the reflection (30B) diffraction grating is shown. Figure 30C It shows Figure 30B Metallization of the surface of the diffraction grating.

[0097] Figure 31 This is a graph showing the refractive index of TiO2 as a function of wavelength.

[0098] Figure 32 This is a diagram showing the simulated performance of the first transmission grating DG1 for blue light.

[0099] Figure 33 This is a diagram showing the simulated performance of the first transmission grating DG1 for green light.

[0100] Figure 34 This is a diagram showing the simulated performance of the first transmission grating DG1 for red light.

[0101] Figure 35 This is a graph showing the simulated performance of the second reflective grating DG2 for blue light.

[0102] Figure 36 This is a graph showing the simulated performance of the second reflective grating DG2 for green light.

[0103] Figure 37 This is a graph showing the simulated performance of the second reflective grating DG2 for red light.

[0104] Figure 38A The grating profile of the transmission grating used in some embodiments is shown.

[0105] Figure 38B The grating profile of the reflective grating used in some embodiments is shown.

[0106] Figure 38C It shows Figure 38B The metallized surface on the grating.

[0107] Figure 39 This is a diagram showing the simulated performance of the first transmission grating DG1 for blue light.

[0108] Figure 40 This is a diagram showing the simulated performance of the first transmission grating DG1 for green light.

[0109] Figure 41 This is a diagram showing the simulated performance of the first transmission grating DG1 for red light.

[0110] Figure 42 This is a graph showing the simulated performance of the second reflective grating DG2 for green light.

[0111] Figure 43 This is a graph showing the simulated performance of the second reflective grating DG2 for red light.

[0112] Figure 44 This is a schematic cross-sectional side view of half of a second waveguide having a reflective internally coupled diffraction grating DG2 and a transmission externally coupled diffraction grating DG4.

[0113] Figure 45 This is a schematic cross-sectional side view of half of the second waveguide of a system formed by a transmission internally coupled diffraction grating DG1 and two externally coupled diffraction gratings DG3 and DG4. Detailed Implementation

[0114] This document describes waveguide display systems and methods. Some embodiments provide full RGB displays with a wide field of view. Some embodiments use a stack of two waveguides to provide full-color display capability. Such optical devices can be used as waveguides for, for example, AR / VR glasses. In exemplary embodiments, the display does not require light with a specific polarization to operate. For example, it can operate using TE-polarized light, TM-polarized light, or light with both polarizations.

[0115] Figure 1A An exemplary waveguide display device is shown in the figure. Figure 1A This is a schematic cross-sectional side view of the waveguide display device in operation. The image is projected by image generator 102. Image generator 102 can project the image using one or more of a variety of technologies. For example, image generator 102 can be a laser beam scanning (LBS) projector, a liquid crystal display (LCD), a light-emitting diode (LED) display (including organic LED (OLED) or micro LED (μLED) displays), a digital light processor (DLP), a liquid crystal on silicon (LCoS) display, or other types of image generators or light engines.

[0116] Light representing image 112 generated by image generator 102 is coupled into waveguide 104 via diffraction inner coupler 106. Inner coupler 106 diffracts the light representing image 112 into one or more diffraction orders. For example, a ray 108 representing part of the bottom of the image is diffracted by inner coupler 106, and one of the diffraction orders 110 (e.g., second order) is at an angle capable of propagating through waveguide 104 via total internal reflection.

[0117] At least a portion of the light 110 coupled into waveguide 104 via diffractive inner coupler 106 is coupled out of the waveguide via diffractive outer coupler 114. At least some of the light coupled out of waveguide 104 replicates the angle of incidence of the light coupled into the waveguide. For example, in the illustration, the externally coupled rays 116a, 116b, and 116c replicate the angle of the internally coupled ray 108. Since the light leaving the outer coupler replicates the direction of the light entering the inner coupler, the waveguide essentially replicates the original image 112. The user's eye 118 can focus on the replicated image.

[0118] exist Figure 1AIn the example, the external coupler 114 allows a single input beam (such as beam 108) to generate multiple parallel output beams (such as beams 116a, 116b, and 116c) by reflecting only a portion of the externally coupled light each time. In this way, even if the eye is not perfectly aligned with the center of the external coupler, at least some light from each part of the image may reach the user's eye. For example, if the eye 118 moves downwards, beam 116c can enter the eye even if beams 116a and 116b do not, so the user can still perceive the bottom of image 112 despite the positional shift. Therefore, the external coupler 114 partially operates as an exit pupil dilator in the vertical direction. The waveguide may also include one or more additional exit pupil dilators (…). Figure 1A (Not shown in the image) to expand the exit pupil in the horizontal direction.

[0119] In some implementations, waveguide 104 is at least partially transparent to light originating from outside the waveguide display. For example, at least some light 120 from a real-world object (such as object 122) passes through the waveguide 104, allowing the user to see the real-world object while using the waveguide display. Since the light 120 from the real-world object also passes through diffraction grating 114, multiple diffraction orders will exist, and thus multiple images will exist. To minimize the visibility of multiple images, it is desirable that diffraction order zero (not deflected by 114) has high diffraction efficiency for light 120, while higher diffraction orders have lower energy. Therefore, in addition to extending and externally coupling virtual images, external coupler 114 is preferably configured to pass through the zero order of the actual image. In such implementations, the image displayed by the waveguide display may appear to be superimposed on the real world.

[0120] In some implementations, as described further in detail below, the waveguide display includes more than one waveguide layer. Each waveguide layer can be configured to preferentially deliver light with a specific wavelength range and / or angle of incidence from the image generator to the viewer.

[0121] like Figure 1B and Figure 1C As shown, waveguide displays with internal couplers, external couplers, and pupil expanders can have various different configurations. Figure 1B An exemplary layout of a binocular waveguide display is shown. Figure 1BIn the example, the display includes waveguides 152a and 152b for the left and right eyes, respectively. The waveguides include inner couplers 154a and 154b, pupil dilators 156a and 156b, and components 158a and 158b, which operate as outer couplers and horizontal pupil dilators. The pupil dilators 156a and 156b are arranged along an optical path between the inner and outer couplers. An image generator (not shown) can be provided to each eye and is arranged to project light representing the image on the corresponding inner coupler.

[0122] Figure 1C Another exemplary layout of a binocular waveguide display is shown in the image. Figure 1C In the example, the display includes waveguides 160a and 160b for the left and right eyes, respectively. The waveguides include inner couplers 162a and 162b. Light from different parts of the image can be coupled by the inner couplers 162a and 162b to different directions within the waveguides. Inner-coupled light traveling to the left passes through pupil dilatators 164a and 164b, while inner-coupled light traveling to the right passes through pupil dilatators 166a and 166b. Having passed through the pupil dilatators, light is coupled out of the waveguides using components 168a and 168b, which operate as both outer couplers and vertical pupil dilatators to substantially replicate the image provided at the inner couplers 162a and 162b.

[0123] In different implementations, different features of the waveguide display can be disposed on different surfaces of the waveguide. For example (e.g.) Figure 1A In some configurations, both the inner and outer couplers can be positioned on the front surface of the waveguide (away from the user's eye). In other embodiments, the inner and / or outer couplers can be positioned on the rear surface of the waveguide (facing the user's eye). The inner and outer couplers can be positioned on opposite surfaces of the waveguide. In some embodiments, one or more of the inner coupler, outer coupler, and pupil dilator can be present on both surfaces of the waveguide. The image generator can be positioned facing either the front or rear surface of the waveguide. The inner coupler is not necessarily on the same side of the waveguide as the image generator. Any pupil dilator in the waveguide can be positioned on the front, rear, or both surfaces of the waveguide. In displays with more than one waveguide layer, different layers can have different configurations of inner couplers, outer couplers, and pupil dilators.

[0124] Figure 1D This is a schematic exploded view of a dual-waveguide display according to some embodiments, including an image generator 170, a first waveguide (WG1) 172 and a second waveguide (WG2) 174. Figure 1EThis is a schematic side view of a dual-waveguide display according to some embodiments, including an image generator 176, a first waveguide (WG1) 178, and a second waveguide (WG2) 180. The first waveguide includes a first transmission diffraction inner coupler (DG1) 180 and a first diffraction outer coupler (DG6) 182. The second waveguide has a second transmission diffraction inner coupler (DG2) 184, a reflection diffraction inner coupler (DG3) 186, a second diffraction outer coupler (DG4) 188, and a third diffraction outer coupler (DG5) 190. Different embodiments may use different arrangements of optical components (such as different arrangements of pupil dilatators) on the first and second waveguides.

[0125] Although Figures 1A to 1E The example demonstrates the use of waveguides in near-eye displays, but the same principle can be applied to other display technologies, such as head-up displays for automobiles or other applications.

[0126] The waveguide's field of view can be propagated into the waveguide via a reference through TIR. Described by the maximum span. For example... Figures 2A to 2C As shown, the maximum angular span that can be coupled into a two-mode waveguide can be represented by two rays: one with an incident angle θ. C Critical ray ( Figures 2A to 2C θ C ) and having an incident angle θ G Grazing rays ( Figures 2A to 2C θ G The critical ray is precisely expressed by the critical angle Φ, which is given by the following formula. C Light rays diffracted into the waveguide:

[0127]

[0128] Where n2 is the refractive index of the waveguide material at wavelength, and is the wavelength of the incident light. Above the critical angle Φ C Total internal reflection (TIR) ​​occurs, such as Figure 2A As shown. Grazing rays have an input angle θ G The light ray, which is incident at a grazing angle of approximately 90° on Φ G Diffraction into the waveguide, such as Figure 2C As shown. In some cases, grazing rays have an input angle θ of 0° or close to 0°. G However, for readability, in Figure 2C θ is shown at a larger angle. G In some implementations, the angular range of light coupled to the left can overlap with the angular range of light coupled to the right. The theoretical FoV of the waveguide presented above is for a single-mode system, where a single diffraction mode is used to carry the image: a +1 or -1 diffraction mode.

[0129] In optical waveguide-based systems, the field of view can be limited by the angular bandwidth of the glass plate. If a mode is diffracted into the glass plate, the FoV can be described as a function of the refractive index of the glass material. The FoV of a waveguide with a refractive index of n² is given by the following equation:

[0130]

[0131] For n2 = 1.5, the total field of view of a single-mode system is more precisely limited to Δθ1 = 28.96 degrees. It can be seen that, due to the general availability of materials with refractive indices higher than 2.0, a 60-degree FoV may be a practical limitation for single-mode flat waveguides.

[0132] By utilizing the second propagation direction inside the waveguide, the field of view of the optical waveguide can be further extended.

[0133] An exemplary dual-waveguide solution for full RGB systems

[0134] Figure 3 This is a schematic diagram of a stack of two waveguides, where each waveguide has a diffraction grating. Figure 3 The system uses higher-order modes and ultrawavelength gratings to provide a wide field of view. Angles whose names begin with the letter Θ are located in air. Angles whose names begin with Φ are located in the waveguide and are measured as the angle of the already diffracted light. The superscript C refers to the critical ray in air or in the waveguide, and the superscript G refers to the grazing ray. Some implementations operate to split the field of view and distribute it in two waveguides.

[0135] Exemplary implementations employ ultrawavelength gratings and second-order diffraction to couple high incident angles for ultra-high field of view into the first waveguide (WG1). In some examples, the high incident angle coupled into the first waveguide corresponds to an angle with an absolute value greater than Δθ1 / 2. In this case, the low incident angle is an angle with an absolute value less than Δθ1 / 2. Some such implementations provide a wider FoV than that obtained by the above formula for Δθ1.

[0136] according to Figure 3 , Angle range [Θ C WG1 ;Θ G WG1 ] and [-Θ C WG1 ;-Θ G WG1 The diffraction pattern inside the first waveguide WG1 exhibits an angular range of [Φ]. C WG1 ;Φ G WG1 ] and [-Φ C WG1 ;-Φ GWG1 ].

[0137] In [-Θ G WG1 ;Θ G WG1 The angle range between ] is transmitted through the first diffraction grating with high efficiency (which corresponds to the 0th transmission order T0).

[0138] Upon entering the first waveguide, the left-hand side of the image will propagate to the left and the right-hand side will propagate to the right.

[0139] The transmitted beam has [-Θ] C WG2 ;Θ C WG2 The angle range between [0, 1] and [0, 2] is such that the grazing ray is near the normal. T0 will diffract on the second grating on top of the second waveguide WG2, and the positive incident angle will propagate to the right in the waveguide, while the negative incident angle will propagate to the left in WG2. The second grating differs from the first grating because it has a different spacing size. However, in some embodiments, the geometry may have the same shape as the previous waveguide. The grating shape can be selected to emphasize the nanojet wave.

[0140] Different implementation schemes may employ different technologies to provide full-color display using only two waveguides.

[0141] In some implementations, the spacing between the first diffraction grating (DG1 with spacing d1) and the second diffraction grating (DG2 with spacing d2) is configured to cover an angular range covering the entire FoV (see [reference]). Figure 3 This provides high diffraction efficiency for green light at the ±2nd diffraction order. In such implementations, the first waveguide preferentially couples for high incident angles, and the second waveguide preferentially couples for low incident angles.

[0142] A similar angular distribution with a shift towards the lower angle would correspond to blue diffraction through both gratings. (See below) Figure 5 As shown, the first waveguide will preferentially couple high and low incident angles, and the second waveguide will couple low angles. For blue diffraction through DG2, there is some angular overlap between the ±2nd diffraction orders. As a result, the positive diffraction order will correspond to a positive incident angle and a range of negative incident angles, and the negative diffraction order will correspond to a negative incident angle and a range of positive incident angles. There exists a series of low angles that exhibit a response (angular overlap of characteristics) to these two diffraction orders. This may help to account for undesirable degradation that limits image quality.

[0143] In the red case, the angular distribution of the incident angle coupled by the first and second waveguides will shift towards a higher angle. For example... Figure 5As shown, the first diffraction grating DG1 will preferentially diffract very high incident angles, and the second waveguide will couple both high and low incident angles. The lower remaining incident angle will be transmitted through the highly efficient second diffraction grating. To couple this transmitted beam into the second waveguide (WG2), an exemplary embodiment uses a third reflection diffraction grating (DG3 with a spacing d3) to be placed at the bottom of the second waveguide WG2, and the positive incident angle will propagate to the left (see [reference]). Figure 4A The negative incident angle will propagate to the right in WG2. To improve and protect the performance of the reflection diffraction grating, the surface of DG3 can be covered with a thin metal layer.

[0144] In the second example, the system is configured to account for partial overlap of the characteristics reflected by the third diffraction grating at the wavelength corresponding to green. In this implementation, the first two diffraction gratings are configured to cover the full FoV for blue and cover both high and low incident angles (only a portion of the low incident angle) for green and red. The third diffraction grating will diffract the remaining angular range corresponding to the low incident angle for green and red.

[0145] Figure 4A This is a schematic diagram of the second waveguide WG2 system with two internal couplers of diffraction gratings. Figure 4B This is a schematic diagram of the span of the angle diffracted by DG3 to the left-hand side of the waveguide. Angles whose names begin with the letter Θ are located in air. Angles whose names begin with Φ are located in the waveguide and the angle of the diffracted light is measured. The superscript C' indicates the critical incident ray of DG3, and the superscript G' indicates the grazing ray of DG3.

[0146] In some implementations, the following four diffraction equations are used to select the spacing sizes d1 and d2 of the transmission diffraction gratings DG1 and DG2 of the two waveguides WG1 and WG2 to provide the desired effect. Figure 3 The total field of view coupled by the optical device shown:

[0147]

[0148]

[0149]

[0150]

[0151] In these equations, it is assumed that the refractive index of the environmental material (e.g., air) is equal to one (n1 = 1). Some values ​​are determined by the choice of material, for example, as well as Where n2 is the refractive index of the first waveguide material, n3 is the refractive index of the second waveguide material, and M1 and M2 correspond to the diffraction orders of the first diffraction grating DG1 and the second diffraction grating DG2, respectively. According to an embodiment of this disclosure, Φ... G WG1 and Φ G WG2 Choose approximately 75°.

[0152] Specific values ​​are given in this document as parameters used in some implementations, but other values ​​can be chosen for other implementations. Φ can be selected based on the distance the image must travel into the waveguide before being extracted, the number of TIR bounces, and the thickness of the waveguide. G WG1 and Φ G WG2 The selected value.

[0153] According to at least one embodiment disclosed herein, for example for λ = λ G =530nm, Θ G WG2 Choose -1°. Here, λ G This corresponds to the wavelength of green. Other values ​​are also possible depending on the following design conditions: whether it is desired to overlay the left and right images in the middle of the final image, or whether it is desired that the left and right images do not intersect / overlap.

[0154] Therefore, we can solve the set of equations previously given for the spacing size. From the last one:

[0155]

[0156] By substituting into the previous equation, we can obtain the critical incident angle of the second grating:

[0157]

[0158] Then, because so and Therefore, we can present the equation for the spacing size in this form:

[0159]

[0160] To calculate the spacing d3 of the reflection diffraction grating DG3 of the second waveguide WG2, we use two diffraction grating equations:

[0161]

[0162]

[0163] but, and Here, we correspond to the diffraction order of the third diffraction grating, DG3. We note that for a negative incident angle, we obtain the positive diffraction angle corresponding to the positive diffraction order, and correspondingly, for a positive incident angle, we obtain the negative diffraction angle for the negative mode (see...). Figure 4B For the positive incident angle and the corresponding negative diffraction angle for the negative diffraction order, the equation for the spacing of DG3 can be presented in the following form:

[0164]

[0165] These equations can be used to calculate the partial and final field of view for each waveguide. Table 1 shows some practical parameters and values ​​calculated based on the previously solved set of equations for three diffraction gratings configured for three different wavelengths and n2 = n3 = 1.7:

[0166] Table 1

[0167]

[0168] To avoid black bands in some colors, in some implementations, the FoV of a full RGB system can be equal to 2 × 66.32 = 132.64° (this value corresponds to 2 × Θ for red). C WG2 For the purposes of the following description, FoV is considered to be subject to the angular range [-Θ]. C* WG2 ;Θ C* WG2 The restriction of Θ, where Θ C* WG2 = 66.32°. This type of implementation uses only two waveguides to achieve a wide field of view, which is larger than enough to cover the total human field of view, where the stereo field of view is effective for human vision, and is 114 degrees. In some implementations, the refractive index of the two waveguides can be increased, and a full 180-degree field of view can be achieved for a full RGB system with two waveguides.

[0169] Figure 5 This is a schematic cross-sectional view of an exemplary display system using two waveguides. Figure 5 The diagram presents a schematic of a waveguide system corresponding to the values ​​proposed in Table 1.

[0170] Figures 6A to 6C These are schematic diagrams of a dual-waveguide system with a wide field of view. These diagrams show the coupling of light into the first waveguide (top) and the second waveguide (bottom) at different incident angles for three different colors, corresponding to blue, green, and red, respectively. Figure 6AThis illustrates the coupling of blue light through a dual-waveguide system. (Example:) Figure 6A As shown, blue light at a relatively high incident angle is preferentially coupled into the first waveguide 602 via a first transmission diffraction inner coupler, which can be located on the front surface of the first waveguide. Figure 6A Blue light at a relatively low incident angle passes through the first waveguide and is preferentially coupled into the second waveguide 604 via a second transmission diffraction inner coupler, which is located on the front surface of the second waveguide.

[0171] Figure 6B The coupling of green light through a dual waveguide system is shown. Figure 6B This illustrates that green light at a relatively high incident angle is preferentially coupled into the first waveguide 602 via a first transmission diffraction inner coupler. Green light at a relatively low incident angle passes through the first waveguide and is preferentially coupled into the second waveguide 604 via a second transmission diffraction inner coupler.

[0172] Figure 6C The coupling of red light through a dual waveguide system is shown. Figure 6C This shows that almost no red light couples into the first waveguide. Instead, red light passes through the first waveguide and preferentially couples into the second waveguide. At relatively high incident angles, the front surface of the second waveguide ( Figure 6C The second transmission diffraction inner coupler on the top surface of the second waveguide preferentially couples red light into the second waveguide. At relatively low incident angles, the rear surface of the second waveguide (… Figure 6C The reflection diffraction inner coupler on the bottom surface of the waveguide preferentially couples red light into the second waveguide.

[0173] Figures 6A to 6C and Figure 7 The diagram presents a schematic explanation of the role of each waveguide relative to the wavelength and angular range of an RGB image with a field of view of 132.64 degrees. Figures 6A to 6C The working principle of the system for the three colors is illustrated schematically. The possible angle values ​​are presented in Table 1. Figure 7 This is a diagram illustrating the coupling and transmission of different colors of light by an implementation with two waveguides, starting with WG1 with a diffraction grating DG1, which couples blue and green. An RGB image is provided as input, and these three colors can be superimposed, but for clarity, they are shown separately to emphasize the behavioral differences of each color. A schematic diagram explains the angular space for each color (starting with blue).

[0174] Figure 7Information regarding the angular space for incident light coupled to and transmitted through the waveguide is shown. In this figure, the minimum angular value for the range of angles coupled to the waveguide is determined under the assumption that the grazing angle inside the waveguide is equal to 90°. For the second waveguide, Figure 8 This shows portions of the light coupled by the ±2nd diffraction order of the DG2 waveguide, and portions of the directly transmitted light corresponding to the zeroth diffraction order of the DG2 (see [link]). Figure 8 The left side of the waveguide can be coupled using only the third reflection diffraction grating DG3 (see the left side of the waveguide). Figure 8 (The right side of the text).

[0175] from Figure 7 and Figure 8 It is evident that by multiplexing different combinations of color and angle spaces, the two waveguides can couple a wide field of view of 132.64 degrees. The size of the reflection diffraction grating DG2 can be chosen to be small enough (given the thickness of the second diffraction grating) that the ±2 diffraction orders of DG2 do not project onto DG3. As mentioned above, the FoV of the entire system can be limited by the FoV obtained for the red diffracted by DG2.

[0176] Figure 7 This is a schematic diagram illustrating the effect of the first waveguide (WG1) relative to the wavelength and angular range of an RGB image with a field of view of 132.64 degrees. The first waveguide has an in-line coupler (DG1 with a spacing d1) within a transmission diffraction grating.

[0177] Figure 8 This is a schematic diagram illustrating the effect of the second waveguide relative to the wavelength and angular range of an RGB image with a field of view of 132.64 degrees. The second waveguide has two diffraction grating couplers (a transmission grating DG2 with a spacing of d2 and a reflection grating DG3 with a spacing of d3).

[0178] Implementation scheme of non-polarized light diffraction grating

[0179] In this section, we present two types of transmission diffraction gratings with high refractive indices (with twins). Figure 9A ) and U-shaped ( Figure 9B A numerical simulation set of elements, the transmission diffraction grating is configured to simultaneously generate dense ±2nd diffraction orders for two polarizations (TE and TM).

[0180] Figure 9A It is a cross-sectional view of the basic type of a diffraction grating with twin elements. Figure 9B This is a cross-sectional view of the basic type of a diffraction grating with a transmission grating having U-shaped elements. Figure 9C This is a cross-sectional view of the basic type of a diffraction grating with a U-shaped element. Figure 9D It is a cross-sectional view of the basic type of a diffraction grating with twin elements.

[0181] The presented data were obtained using COMSOL Multiphysics software. The simulation implementation used TiO2 as the material for the grating elements and glass with a refractive index n2 = n3 = 1.7 as the substrate material. The presented numerical simulations take into account the dispersion of the TiO2 material, as described in JRDevore, “Refractive indices of rutile and sphalerite,” J. Opt. Soc. Am. 41, 416-419 (1951). Based on the results of ordinary spectral measurements presented in this document, the following refractive index values ​​were used for the three different colors (see...). Figure 10 ):

[0182] Blue (λ=460nm) - nH=2.7878;

[0183] Green (λ=530nm) - nH=2.6702;

[0184] Red (λ=625nm)-nH=2.5884.

[0185] Figure 10 This is a graph showing the refractive index of TiO2 for a series of wavelengths.

[0186] Figure 12 to Figure 22 The results of numerical simulations for two types of diffraction gratings (twin and U-shaped morphologies) with high refractive indices, configured for use with two polarizations, are presented. In the simulation implementation, n1 is the refractive index of the host medium, and n1 = 1. We have considered a combination of two waveguides for a full RGB system with FoV = 132.64°.

[0187] The first transmission grating DG1, configured for green to couple the ±2nd order at high incident angles, for the first waveguide (WG1), has a spacing of d1 = 471.27 nm and twin elements with W1 = 130 nm; W2 = 110 nm; H2 = 240 nm. Combining the responses for the two polarizations, we can obtain fairly good diffraction homogeneity for the ±2nd order transmitted waves at incident angles of -66.34° to +66.34° at wavelengths corresponding to green and blue (see Table 1 and...). Figure 7 ).

[0188] The second transmission grating DG2, configured for green to couple the ±2nd order for the second waveguide (WG2) at low incident angles, has a spacing size d2 = 652.46 nm, and the parameters of the twin elements are: W1 = 180 nm; W2 = 140 nm; H2 = 240 nm. Using an additional block with a height H1 = 20 nm, we obtain a U-shaped element. The combination of responses to the two polarizations will provide high diffraction uniformity of the overall response for the three colors across different angular ranges (see Table 1 and...). Figure 8 Examples presented for two different components demonstrate the impact of component morphology on system performance.

[0189] A third reflection grating DG3 for the second waveguide (WG2) is configured for the red wavelength to convert a portion of the red light transmitted by the second diffraction grating (0th transmission order T0) into ±2nd diffraction orders coupled by WG2. The morphologies of the elements described herein (e.g., U-shaped and twin morphologies) can also be used for high-performance ultrawavelength in-coupled high-refractive-index dispersion material reflection gratings, which can also simultaneously produce dense ±2nd diffraction orders for both polarizations (TE and TM). To prevent transmission through the waveguide and increase the intensity of the diffracted light, in some embodiments, the surface of the diffraction grating is metallized (see [link to relevant documentation]). Figure 11 In one embodiment, the third diffraction grating has a spacing of d3 = 769.41 nm, and the twin elements have W1 = 180 nm; W2 = 200 nm; H2 = 400 nm. For the U-shaped system in this example, the height of the central block is equal to H1 = 20 nm.

[0190] Figure 11 This is a cross-sectional view of the basic type of the metallized U-shaped element of the coupler within the reflective grating. The metallized surface is depicted by dark lines.

[0191] Figures 12A to 12F The diffraction performance of the dual-waveguide system for green light was depicted. The simulation implementation used a twin diffraction grating DG1 for the first waveguide WG1. For the second waveguide WG2, both U-shaped and twin diffraction gratings DG2 were simulated.

[0192] Specifically, Figure 12A The reflectivity and transmittance of TM-polarized green light with a wavelength of 530 nm as it passes through a transmission diffraction coupler in the first waveguide at different diffraction orders are shown. Figure 12B The reflectivity and transmittance of TE-polarized green light with a wavelength of 530 nm as it passes through the transmission diffraction coupler in the first waveguide at different diffraction orders are shown. Figures 12A to 12B The transmission diffraction inner coupler of the simulated implementation has, for example, Figure 9A The twin-shaped diffraction grating shown.

[0193] Figure 12C The reflectivity and transmittance of TM-polarized green light with a wavelength of 530 nm through a transmission diffraction coupler of a second waveguide in some embodiments are shown. Figure 12D The reflectivity and transmittance of TE-polarized green light with a wavelength of 530 nm as it passes through the transmission diffraction inner coupler in the second waveguide are shown. Figures 12C to 12D The transmission diffraction inner coupler of the simulated implementation has, for example, Figure 9B The U-shaped diffraction grating shown.

[0194] Figure 12E The reflectivity and transmittance of TM-polarized green light with a wavelength of 530 nm through a transmission diffraction coupler of a second waveguide in some embodiments are shown. Figure 12F The reflectivity and transmittance of TE-polarized green light with a wavelength of 530 nm as it passes through the transmission diffraction inner coupler in the second waveguide are shown. Figures 12E to 12F The transmission diffraction inner coupler of the simulated implementation has, for example, Figure 9A The twin-shaped diffraction grating shown.

[0195] Figures 13A to 13F The diffraction performance of the dual-waveguide system for blue light is depicted. In the presented system, a twin diffraction grating DG1 was used for the first waveguide WG1; and a U-shaped / twin diffraction grating DG2 (for comparison) was used for the second waveguide WG2.

[0196] Specifically, Figure 13A The reflectivity and transmittance of TM-polarized blue light with a wavelength of 460 nm as it passes through a transmission diffraction coupler in the first waveguide at different diffraction orders are shown. Figure 13B The reflectivity and transmittance of TE-polarized blue light with a wavelength of 460 nm as it passes through the transmission diffraction coupler in the first waveguide at different diffraction orders are shown. Figures 13A to 13B The transmission diffraction inner coupler of the simulated implementation has, for example, Figure 9A The twin-shaped diffraction grating shown.

[0197] Figure 13C The reflectivity and transmittance of TM-polarized blue light with a wavelength of 460 nm through a transmission diffraction coupler of a second waveguide in some embodiments are shown. Figure 13D The reflectivity and transmittance of TE-polarized blue light with a wavelength of 460 nm as it passes through the transmission diffraction coupler in the second waveguide at different diffraction orders are shown. Figures 13C to 13D The simulated transmission diffraction inner coupler has the following characteristics: Figure 9B The U-shaped diffraction grating shown.

[0198] Figure 13EThe reflectivity and transmittance of TM-polarized blue light with a wavelength of 460 nm through a transmission diffraction coupler of a second waveguide in some embodiments are shown. Figure 13F The reflectivity and transmittance of TE-polarized blue light with a wavelength of 460 nm as it passes through the transmission diffraction coupler in the second waveguide at different diffraction orders are shown. Figure 13E The simulated transmission diffraction inner coupler in -F has the following characteristics: Figure 9A The twin-shaped diffraction grating shown.

[0199] Figures 14A to 14J The diffraction performance of the dual-waveguide system for red light is depicted. In the presented system, a twin diffraction grating DG1 is used for the first waveguide WG1; and a U-shaped / twin (for comparison) transmission diffraction grating DG2 and a U-shaped / twin (for comparison) reflection diffraction grating DG3 are used for the second waveguide WG2.

[0200] Specifically, Figure 14A The reflectivity and transmittance of TM-polarized red light with a wavelength of 625 nm as it passes through the transmission diffraction coupler in the first waveguide at different diffraction orders are shown. Figure 14B The reflectivity and transmittance of TE-polarized red light with a wavelength of 625 nm as it passes through the transmission diffraction coupler in the first waveguide at different diffraction orders are shown. Figures 14A to 14B The transmission diffraction inner coupler of the simulated implementation has, for example, Figure 9A The twin-shaped diffraction grating shown.

[0201] Figure 14C The reflectivity and transmittance of TM-polarized red light with a wavelength of 625 nm through the transmission diffraction inner coupler of the second waveguide are shown in some embodiments. Figure 14D The reflectivity and transmittance of TE-polarized red light with a wavelength of 625 nm as it passes through the transmission diffraction coupler in the second waveguide at different diffraction orders are shown. Figures 14C to 14D The transmission diffraction inner coupler of the simulated implementation has, for example, Figure 9B The U-shaped diffraction grating shown.

[0202] Figure 14E The reflectivity and transmittance of TM-polarized red light with a wavelength of 625 nm through the transmission diffraction inner coupler of the second waveguide are shown in some embodiments. Figure 14F The reflectivity and transmittance of TE-polarized red light with a wavelength of 625 nm as it passes through the transmission diffraction coupler in the second waveguide at different diffraction orders are shown. Figures 14E to 14F The transmission diffraction inner coupler of the simulated implementation has, for example, Figure 9A The twin-shaped diffraction grating shown.

[0203] Figure 14GThe reflectivity and transmittance of TM-polarized red light with a wavelength of 625 nm through the reflection diffraction inner coupler of the second waveguide in some embodiments are shown. Figure 14H The reflectivity and transmittance of TE-polarized red light with a wavelength of 625 nm as it passes through the reflection diffraction coupler in the second waveguide are shown. Figures 14G to 14H The reflection diffraction inner coupler of the simulated implementation has, for example, Figure 9D The twin-shaped diffraction grating shown.

[0204] Figure 14I The reflectivity and transmittance of TM-polarized red light with a wavelength of 625 nm through a reflection diffraction coupler of a second waveguide in some embodiments are shown. Figure 14J The reflectivity and transmittance of TE-polarized red light with a wavelength of 625 nm as it passes through the reflection diffraction coupler in the second waveguide are shown. Figures 14I to 14J The reflection diffraction inner coupler of the simulated implementation has, for example, Figure 9C The U-shaped diffraction grating shown.

[0205] External coupler system for second waveguide

[0206] The following discusses an exemplary embodiment of an external coupler configured to externally couple a red image from a second waveguide. The exemplary embodiment is configured to externally couple the incident image with an appropriate angular span.

[0207] To externally couple the red image coupled to waveguide WG2 via diffraction gratings DG2 and DG3, some embodiments use two diffraction gratings DG4 (reflection grating) and DG5 (transmission grating) from both sides of the plate. An exemplary embodiment is a dual-mode device that uses the +2 diffraction mode of DG2 to carry the right-hand side image (positive high incident angle at the inner coupler) in the right-hand direction, and uses the -2 mode to propagate the negative high incident angle in the opposite direction of the waveguide. The positive low incident angle will be directly transmitted by diffraction grating DG2 and converted to the -2 order of reflection DG3 propagating in the left-hand direction, while the negative low incident angle will be transformed into the +2 mode and propagated in the right-hand side direction of the waveguide. In the exemplary embodiment, the outer coupler is configured to maintain the same angular span. For illustration, consider a portion of the image propagating to the left side of the waveguide, as per [reference to...]. Figure 15 and Figure 16 As shown.

[0208] Figure 15 This is a schematic diagram showing some optical components of a second waveguide having a reflective internally coupled diffraction grating DG3 and a transmission externally coupled diffraction grating DG5.

[0209] Figure 16This is a schematic diagram of some optical components in the second waveguide of a system formed by a transmission internally coupled diffraction grating DG2 and two externally coupled diffraction gratings DG4 and DG5.

[0210] To externally couple a portion of the image directly transmitted (the zero-order beam T0 transmitted without diffraction) by the second diffraction grating DG2 and converted to the +2 diffraction order by the third reflection diffraction grating, an exemplary embodiment uses a fifth diffraction grating with a spacing of d5. The waveguide thickness, as well as the size and position of the diffraction grating DG4, can be selected to avoid interaction between this portion of the image and DG4. Figure 15 , Angle range [-Θ G” WG2 ;-Θ L WG2 ], where Θ L WG2 It is the maximum incident angle directly transmitted through DG2, transmitted inside waveguide WG2 and diffracted by DG3 within the waveguide into an angle range [Φ]. G WG2 ;Φ L WG2 Entering the waveguide, the right-hand side of the image with a low incident angle will propagate towards the left. Finally, after multiple internal reflections, it will reach DG5. To obtain externally coupled light with the same angular space, the spacing d5 of the transmission diffraction grating DG5 of waveguide WG2 can be selected using a system of diffraction grating equations:

[0211]

[0212]

[0213] As mentioned earlier, assume n1 = 1, and... The angle is chosen to be approximately 75°. M′ corresponds to the diffraction order of diffraction grating DG5.

[0214] but, Considering the sign of the corresponding angle, the presented expression compared with Equation 6 shows that in order to obtain the same angular span of the externally coupled light, d5 can be chosen such that d5 = d3 and N = -M'.

[0215] To externally couple a portion of the image coupled by WG2 through the second diffraction grating DG2 (specifically the +2nd diffraction order) and thus avoid diffraction through DG3, a fourth diffraction grating with a spacing of d4 can be used. According to Figure 16 , Angle range [Θ C WG2 ;Θ G WG2(High incident angle) diffracts within waveguide WG2 into an angle range propagating to the left [Φ] c WG2 ;Φ G WG2 Finally, after multiple internal reflections, it will reach the reflection diffraction grating DG4, which has a spacing size selectable according to the diffraction equation system:

[0216]

[0217]

[0218] in and This is determined by the grazing angle and critical angle of the diffraction from the reflection diffraction grating DG4. In this example, it is assumed that the incident angle is positive, the angle corresponding to the diffraction order is positive, and the diffraction order is negative. N′ corresponds to the diffraction order of the diffraction grating DG4.

[0219] Therefore, the spacing of DG4 can be calculated as follows:

[0220]

[0221] Assuming that the diffracted light should then be directly transmitted by DG5 (making the angular range...) (corresponding to the 0th diffraction order) into a host medium with a refractive index n1 = 1 and an angular range [Θ] C WG2 ;Θ G WG2 We obtained and Then, the spacing of DG4 can be calculated using the following formula:

[0222]

[0223] Considering the signs of the corresponding angles, the presented expression compared with Equation 4 shows that in order to obtain the same angular span of the externally coupled light, in some implementations, for N' = -M2, d4 = d2.

[0224] Considering the diffraction angle inside the waveguide, it can be concluded that the green and blue virtual images will be coupled only to the outside of the diffraction grating DG5, without substantially interacting with DG3 and DG4.

[0225] While some embodiments described herein employ a second diffraction order for each of the inner and outer couplers, other embodiments may use a first diffraction order. In such embodiments, the coupler using the first diffraction order may have a grating pitch that is half the grating pitch of the corresponding coupler using the second diffraction order.

[0226] One advantage of some implementations is the reduction in the number of waveguides used to provide a high FoV using unpolarized light. An exemplary implementation combines beams diffracted by reflection and transmission diffraction gratings placed from opposite sides of a glass plate. We also calculated parameters for the angular range of the externally coupled light maintained by the external coupler. It should also be noted that our nanojet wave-based technique can be used in twin and U-shaped reflection diffraction gratings to achieve ±2nd order diffraction. It should be noted that a full 180-degree field of view can be achieved for a full RGB system with two waveguides if the refractive indices of the two waveguides are slightly adjusted.

[0227] In some implementations, the following formula is used to calculate the FoV range:

[0228]

[0229]

[0230] In some implementations, for n3 = 1.5, λ R =625nm and λ G =530nm, the system operates to couple light with an incident angle greater than 38° and less than 100° to at least one of the first waveguide and the second waveguide.

[0231] In some implementations, for n3 = 2.0, λ R =625nm and λ G =530nm, the system operates to couple light with an incident angle greater than 100° and up to 180° to at least one of the first and second waveguides.

[0232] In some implementations, for the change of n3 from 1.5 to 2.0, λ R =625nm and λ G =530nm, the system operates to couple light with an incident angle greater than 38° and up to 180° into at least one of the first and second waveguides.

[0233] In some implementations, the following formula is used to determine the acceptable range of spacing d2:

[0234]

[0235]

[0236]

[0237] In some implementations, with n2 and n3 between 1.5 and 2.0 and with M1 = 1 or 2, the first grating spacing (d1) of the first transmission diffraction inner coupler is between 170 nm and 760 nm.

[0238] In some implementations, for n3 between 1.5 and 2.0 and for M1 = 1 or 2, the second grating spacing (d2) of the second transmission diffraction inner coupler is between 260 nm and 890 nm.

[0239] In some implementations, for n3 between 1.5 and 2.0 and for M1 = 1 or 2, the third grating spacing (d3) of the reflection diffraction inner coupler is between 300 nm and 1050 nm.

[0240] Exemplary single waveguide structure .

[0241] Some exemplary embodiments provide a full RGB single waveguide system with high FoV. Some such embodiments are based on a combination of two inner-coupled diffraction gratings and two outer-coupled diffraction gratings placed from both sides of the waveguide. Some such embodiments allow the use of only one waveguide. Due to the use of dual-mode image propagation, some embodiments exhibit a very high field of view.

[0242] An exemplary implementation uses a high FoV optical full RGB system with only one waveguide, which can be used to couple light into and / or out of the optical device. Such an optical device can be used as a waveguide, for example, in AR / VR glasses. Reducing the number of waveguides while maintaining the high FoV allowed by the guiding rate helps to miniaturize (reduce weight or size) and simplify the system.

[0243] For a waveguide based on a diffraction grating with an optical system that generates a composite image to be superimposed in the field of view, it is desirable for the lens system to have a real, rather than virtual, exit pupil. In other words, its exit pupil is located outside the lens and is also the aperture stop of the lens.

[0244] Figure 19 The lens system provides a suitable exit pupil. The system has a disc-shaped aperture stop, the diameter of which depends on the diameter of the lens, which primarily limits the system size. Since there is no lens behind the aperture stop, it is the image of the aperture stop itself, and therefore the exit pupil. It is located where an internal coupler can be placed, or in its vicinity.

[0245] If any of the objects or images is at infinity, the lens system can be called afocal. Figure 19The lens system is focal-free on the image side because the light rays leaving the lens are parallel for every field, and the image exists at infinity.

[0246] The position of a point on an object can be called a field. Figure 19 The diagram shows light rays exiting five different fields. In some cases, a pixel can be considered a field. Compared to other quantities in the system, the size of a pixel can be assumed to be negligible.

[0247] like Figure 19 As seen, light from each field pours through the entire exit pupil. Therefore, if we reduce the aperture of the exit pupil, we also simultaneously and uniformly block the amount of light from each pixel across all fields, meaning the light intensity decreases. This is the function of the aperture stop, and it confirms that the exit pupil and the aperture stop are identical in this lens, and that the exit pupil is real, not virtual.

[0248] The pupil can be tessellated in space. This means that light rays striking the pupil from the positive side (y>0) will undergo one diffraction process, while light rays striking the pupil from the negative side (y<0) will undergo another diffraction process. The origin of the y-axis is the optical axis. Light rays striking the pupil with a certain angular sign will undergo a specific process, while those striking with the opposite sign will undergo another diffraction process. Alternatively, tessellation of the pupil angle can result in light rays with a range of [θ1, θ2] being diffracted in one direction of the waveguide, while light rays with a range of [-θ1, -θ2] are diffracted in the opposite direction.

[0249] Another characteristic of a focalless lens is that it maps all pixels from the display to a spherical coordinate system, where each pixel is referenced by its corresponding position in Cartesian coordinates via its (x, y) coordinates on the display. Relative to Figure 19 The image plane can be considered as being in the xy-plane, where the y-axis extends vertically across the page and the x-axis is perpendicular to the page. After a focal-free lens system, rays emanating from a single field cannot be referenced by x or y because they diffuse, but they each have a unique direction distinct from one another between pixels. The lens transforms pixel (x, y) coordinates into spherical (θ, φ) pairs. This means that for each ray direction in the exit pupil (or inner coupler), we process another pixel.

[0250] exist Figure 20 In the example, rays from a field y>0 and rays from a field y<0 have angles with opposite signs at the exit pupil in polar coordinates. If we use a spherical coordinate system with the z-axis pointing along the optical axis, the polar angles are always between 0 and pi (positive), and only the azimuth direction sign will distinguish whether a ray strikes the exit pupil 'from above' or 'from below'. At each location along the exit pupil, we have positive and negative ray directions in polar coordinates.

[0251] When using symmetric diffraction modes, the diffraction grating will diffract the incoming light in either an additive or subtractive order. In some cases, if the light has a particular sign orientation, it will diffract in one mode, and if that sign changes, it will diffract into the opposite mode. In fact, mathematically, diffraction always occurs in all modes. Therefore, what we mean here is that if, for an incoming light in a particular direction, we diffract into a particular mode, then the energy in that mode is stronger than in the mode with the opposite sign. The symmetry here means that if the additive direction diffracts efficiently into mode M, then the subtractive direction will diffract efficiently into the -M direction (where M is a relative natural number).

[0252] Symmetric diffraction gratings typically allow for the pre-existing characteristics of symmetrical diffraction modes. This characteristic can be achieved by using a basic structure (fundamental spacing) with left-right geometric symmetry. Blazed tilt gratings are not symmetrical diffraction gratings. Gratings based on square-shaped stepped (gate-shaped) structures can be symmetrical diffraction gratings. Figure 21 and Figure 22 An example of a symmetrical diffraction grating is provided.

[0253] Exemplary implementations use symmetric diffraction gratings that enable very efficient symmetric diffraction modes. For incident angles with opposite signs, some implementations provide highly efficient +M or -M diffraction modes.

[0254] Figure 23 The diagram shows a tilted grating that, when illuminated from above, will be effective for light tilted to the left (a negative angle in our case) and will have the optimal diffraction pattern towards the right side. When illuminated from the right side (a positive angle), the diffraction pattern towards the left will be very weak.

[0255] Figure 24 The application of symmetrical diffraction with asymmetric gratings using two different diffraction gratings is shown. Figure 24 The internally coupled grating in the [structure] has an asymmetric groove profile. The grating is divided into two parts, each primarily coupled in one direction. Figure 24 In this system, for a limited angular range, light rays from the left-hand side will diffract with high efficiency to the left, and light rays from the right-hand side will diffract with high efficiency to the right. In addition to this process, a small fraction of the energy will also be diffracted in the opposite direction for the opposite diffraction pattern.

[0256] In such Figure 24In the diffraction grating, only light rays with a negative propagation direction striking the right-hand side grating will diffract efficiently into the right-hand side diffraction mode. Light rays with a negative incident angle striking the right-hand side diffraction grating will not diffract into the right-hand side diffraction mode (but they will actually have low intensity). Only light rays with a positive propagation direction striking the left-hand side grating will diffract efficiently into the left-hand side diffraction mode. Light rays with a negative incident angle striking the left-hand side diffraction grating will only diffract into the left-hand side diffraction mode with low intensity. Thus, at each position of the exit pupil, there is an equal distribution of positive and negative angle propagation, and approximately half of the light will be lost. Figure 25 The typical diffraction efficiency for two gratings as a function of the incident angle is shown.

[0257] In contrast, some implementations use features such as Figure 26A The diffraction grating with the outline shown provides more uniform light coupling across different incident angles, such as... Figure 26B It is shown schematically in the diagram.

[0258] Some exemplary embodiments provide single-waveguide panchromatic solutions with high FOV for internally coupling light into optical devices. Some embodiments offer high efficiency and high diffraction uniformity for internally coupled light. Figure 27 This is a schematic side view of the waveguide used in some implementation schemes.

[0259] Figures 28A to 28B This is a schematic side view of a single-waveguide internally coupled system, showing an example of a transmission diffraction grating. Figure 28A ) and reflection diffraction grating ( Figure 28B The angle between the incident and diffracted light. Angles named starting with Θ are in air (or other ambient medium). Angles named starting with Φ are in the waveguide and measure the angle of the already diffracted light. C is the critical ray in air or the waveguide, and G is the grazing ray. Negative incident angles and their corresponding diffracted angles inside the waveguide are marked with solid arrows, and positive incident angles and their corresponding diffracted angles inside the waveguide are marked with dashed arrows.

[0260] Exemplary implementations operate by diffracting the incident light using two diffraction gratings and internally coupling them into a waveguide. The correct combination of diffraction gratings described in this disclosure provides high FoV for all three colors. Figures 28A to 28B The functions of the transmission (28A) diffraction grating and the reflection (28B) diffraction grating are shown. Angular range [Θ] C ;Θ G ] and [-Θ G ;-Θ C The waveguide diffracts into an angular range [Φ]. C ;Φ G ] and [-Φ G ;-Φ CAs light passes through a transmission diffraction grating into the waveguide, the left-hand side of the image propagates to the left, while the right-hand side propagates to the right. Finally, the left-hand side of the image, corresponding to a negative incident angle, will primarily shift to the negative transmission diffraction order (first or second order, depending on the system morphology) within the waveguide. The right-hand side of the image, corresponding to a positive incident angle, will shift to the positive transmission diffraction order. In the case of light diffraction from a reflection diffraction grating at the bottom of the waveguide, the positive incident angle will propagate to the left of the waveguide, corresponding to the negative reflection diffraction order, while the negative incident angle will propagate to the right of the waveguide, corresponding to the positive reflection diffraction order. The reflection grating differs from the transmission grating in that it has different spacing sizes calculated for the appropriate wavelength, but the geometry emphasizing the edge waves can have the same shape.

[0261] In order to reduce the number of waveguides to one waveguide, some implementations use diffraction gratings with the following characteristics.

[0262] In some implementations, for a transmission diffraction grating (DG1 with a spacing d1), the spacing size is calculated for the blue wavelength and the full FoV angular range covering the grating (2Δθ1 for a two-mode system), assuming the incoming grazing ray is near the normal. The diffraction grating can be selected to achieve high diffraction efficiency at the corresponding order (±2nd or ±1st order, depending on the morphology) at the blue wavelength within the mentioned angular range. Figure 29A As shown, corresponding to blue, the angle range is [Θ]. C 1; Θ G 1] and [-Θ G 1; -Θ C 1] Diffraction within the waveguide forms an angle range [Φ] G 1; Φ C 1] and [-Φ C 1; -Φ G 1]. DG1 can be configured such that Θ C 1 ≈ Δθ1. (Note that Θ) C 1, Θ G 1、 Φ G 1 and Φ C 1. Different values ​​can be assigned to each color.

[0263] At the wavelength corresponding to green, there is a shift in the angular distribution towards higher incident angles. For example... Figure 29B As shown, at the green wavelength, the angle range [Θ] C 1; Θ G 1] and [-Θ G 1; -Θ C 1] Diffraction within the waveguide forms an angle range [Φ] G 1; Φ C 1] and [-ΦC 1; -Φ G 1]. In [-Θ G 1; Θ G The angular range between 1] is transmitted with very high efficiency through the transmission diffraction grating DG1 (which corresponds to the 0th transmission order T0). This portion of the incident image will be diffracted by the reflection grating from the bottom of the waveguide. If for values ​​above |±Θ G If the angular range of 1| is high and the transmittance T0 is also high, then it will also be diffracted by the reflected DG2 (the corresponding diffraction angle range depends on the parameters of the reflected DG2, and cannot be greater than [-Θ]. C 2; Θ C 2]), and thereafter it can be combined with a portion of the image diffracted by DG1.

[0264] A similar function will be observed at the wavelength corresponding to red. Increasing the wavelength yields an additional shift in the angular distribution towards higher incident angles. For example... Figure 29C As shown, at the red wavelength, the angular range [Θ] C 1; Θ G 1] and [-Θ G 1; -Θ C 1] Diffraction within the waveguide forms an angle range [Φ] G 1; Φ C 1] and [-Φ C 1; -Φ G 1]. As in the case of green, in [-Θ G 1; Θ G The angular range between [1] is transmitted with very high efficiency through the transmission diffraction grating DG1 (which corresponds to the 0th transmission order T0). This portion of the incident image will also be diffracted by the reflection grating DG2. If for values ​​above |±Θ... G If the angular range of 1| is high and the transmittance T0 is also high, then it can also be diffracted by reflection DG2 (the diffraction angle range depends on the parameters of DG2 and cannot be greater than [-Θ]). C 2; Θ C 2]), and thereafter it can be combined with a portion of the image diffracted by DG1.

[0265] In some implementations, the reflection diffraction grating (DG2 with a spacing d2) has a spacing size calculated for the red wavelength and the full FoV angular range covering the reflection diffraction grating (2Δθ1 for a two-mode system), also assuming that the grazing ray is near the normal. The diffraction grating can be selected to provide high diffraction efficiency at the corresponding order (±2nd or ±1st order, depending on the morphology) at the red wavelength within the mentioned angular range. Figure 29C Corresponding to red, the angle range is [Θ]. C 2; Θ G2] and [-Θ G 2; -Θ C 2] Diffraction within the waveguide forms an angle range [Φ] G 2; Φ C 2] and [-Φ C 2; -Φ G 2]. DG2 can be configured such that Θ C 2≈Δθ1.

[0266] At the wavelength corresponding to green, there is a shift in the angular distribution towards lower incident angles, resulting in angular overlap between the corresponding positive and negative diffraction orders. This means that the positive diffraction order will correspond to negative incident angles and a range of positive incident angles. The negative diffraction order will correspond to positive incident angles and a range of negative incident angles. Finally, we obtain the low-angle range in which we have a response (angular overlap of characteristics) to these two diffraction orders. This fact can be considered to prevent undesirable degradation of image quality.

[0267] In some implementations, the spacing d1 and d2 of the transmission and reflection diffraction gratings DG1 and DG2 of the two waveguides WG1 and WG2 can be calculated using the following diffraction equations, as well as the equations derived from the diffraction equations. Figure 27 The total field of view coupled by the optical internal coupling device shown.

[0268]

[0269]

[0270]

[0271]

[0272] We assume n1 = 1. Some values ​​are known. Where n2 is the refractive index of the waveguide material, and M1 and M2 correspond to the diffraction orders of the first diffraction grating DG1 and the second diffraction grating DG2, respectively. According to an embodiment of this disclosure, and Choose approximately 75°.

[0273] It's important to note that these values ​​are design parameters, and other values ​​can be selected. The optimal values ​​can be chosen based on the distance the image must travel into the waveguide before being extracted, the number of TIR bounces, and the waveguide thickness. and The selected value.

[0274] Considering the corresponding signs of the angle and diffraction order, we can present the equation for the spacing magnitude of DG1 in this form:

[0275]

[0276] Furthermore, we can obtain the critical incident angle of the first grating:

[0277]

[0278] The spacing d2 of the reflection diffraction grating DG2 can be represented in the following form:

[0279]

[0280] The critical incident angle of the second grating has the following form:

[0281]

[0282] These equations can be used to calculate the field of view of the system. The next table (Table 2) shows some practical parameters and the equation set solved previously for two diffraction gratings at three different wavelengths, as well as the value of n2 calculated for a high refractive index wafer. Considering the dispersion of the waveguide material (e.g., sapphire (Al2O3)), we have these refractive index values ​​for the three different colors:

[0283] At λ = 460 nm (blue), n² = 1.7783;

[0284] At λ = 530 nm (green), n² = 1.7719;

[0285] At λ = 625 nm (red), n² = 1.7666.

[0286] In Table 2, the input parameters of the proposed system are shown in parentheses. All computational parameters are not shown in parentheses. For optimization to the first diffraction order of internal coupling (M... 1,2 To calculate the spacing of the diffraction grating at three different wavelengths, we use equations (2) and (4). (For M) 1,2 =2, which will double the grating spacing: d1 = 535.598nm, d2 = 749.67nm)

[0287]

[0288] Table 2

[0289] Below, we assume that the blue FoV is subject to an angle range of [-Θ]. C 1; Θ C The restriction of 1], where Θ C 1 = 45.87°. To avoid black bands in some colors, we propose that the FoV of a full RGB system should be equal to 2 × 45.87 = 91.74° (this value corresponds to 2 × for blue). Such systems achieve a high field of view using only one waveguide. However, if the refractive index of the waveguide is increased, an even higher field of view can be achieved for a full RGB system with a single waveguide.

[0290] Figures 29A to 29C The operation of the exemplary system using three colors is schematically depicted. Examples of possible angle values ​​are presented in Table 2. As input, we have an RGB image and the three colors are superimposed, but for illustration, we show them as non-intersecting to emphasize the behavioral differences of each color. The schematic diagram explains the angle space for each color (from...). Figure 29A (Starting with blue in the diagram). For green (29B) and red (29C), we show a portion of the light coupled through this waveguide using the ±1st diffraction order of DG1 and DG2.

[0291] In this example, most of the blue zero-order particles have angles below the TIR limit. When struck by DG2, these angles will have several diffraction components. Figure 35 As shown, they will be diffracted into modes 0, +1, and -1. Light diffracted into mode 0 will be reflected back, its angle mirrored around the normal, and it will strike the input interface again. If it strikes a place where DG1 is not present, it will leave the waveguide, which is expected. If it strikes DG1, it will leave through diffraction. It retains two diffracted blue light modes through DG2, which can diffract at approximately 20 degrees with a maximum efficiency of approximately 30%. At 20 degrees inside the waveguide, due to Snell's law, this corresponds to a 37.5-degree incident angle of DG1 at that incident point, where the light has an initial power of less than 10% in mode T0 ( Figure 32 This means that due to the undesirable reflections made by DG2, up to 3.0% of the blue will remain.

[0292] Regarding the lateral size of DG2 relative to DG1, the first should be large enough to collect all the useful diffracted rays for the green and red channels. Its size can be a function of the waveguide thickness.

[0293] The FoV of the entire system is limited by the FoV obtained for the blue diffracted by DG1. The total FoV of such a system is approximately 2Δθ1, where Δθ1 is the maximum theoretically possible FoV of the waveguide material.

[0294] It has been optimized to produce high-refractive-index transmission with dense ±1st diffraction order for TE polarization. Figure 30A ) and reflection ( Figure 30B Numerical simulation was performed using a diffraction grating.

[0295] The presented data was obtained using COMSOL Multiphysics software. The simulation uses TiO2 as the material element for the grating and sapphire (Al2O3) as the substrate. The presented numerical simulation considers the dispersion of the TiO2 material. Based on the results of ordinary spectral measurements presented in this document, we have these refractive index values ​​for the three different colors (see [link to document]). Figure 31 ):

[0296] At λ = 460 nm (blue), n3 = 2.7878;

[0297] At λ = 530 nm (green), n3 = 2.6702;

[0298] At λ = 620 nm (red), n3 = 2.5915.

[0299] Figures 32 to 37 The paper presents a set of numerical simulations for two high-refractive-index diffraction gratings configured for TE polarization. We have assumed that n1 is the refractive index of the host medium and n1 = 1 (air). We have considered the combination of two diffraction gratings for a full RGB system with FoV = 91.74°.

[0300] Figures 32 to 34 The figure shows the simulated performance of the first transmission grating DG1 configured for coupling the ±1st order in blue (λ = 460 nm), where the spacing is d1 = 267.799 nm and the elements have w1 = 80 nm and h1 = 110 nm. Figure 32 The performance compared to blue light (λ = 460 nm) is shown. Figure 33 The performance with green light (λ = 530 nm) is shown in the figure. Figure 34 The performance with red light (λ = 620 nm) is shown in the figure.

[0301] Figures 35 to 37 The diagram shows the simulated performance of a second reflective grating DG2 configured for red (λ = 620 nm), where the spacing is d2 = 374.835 nm and the elements have parameters w2 = 140 nm and h2 = 380 nm. This grating converts a portion of the red light transmitted by the first diffraction grating (0th transmission order T0) into ±1st diffraction orders coupled by the waveguide. To prevent transmission through the waveguide and increase the intensity of the diffracted light, the surface of the diffraction grating can be metallized (see [reference]). Figure 30C ). Figures 35 to 37 The range of angles presented corresponds to incident light from a medium with a refractive index n2. Using Snell's law, we can calculate the range corresponding to medium n1. Figure 35 The performance compared to blue light (λ = 460 nm) is shown. Figure 36The performance with green light (λ = 530 nm) is shown in the figure. Figure 37 The performance with red light (λ = 620 nm) is shown in the figure.

[0302] Also for transmission with high refractive index configured to produce dense ±2nd diffraction orders for TE polarization ( Figures 39 to 41 ) and reflection ( Figures 42 to 43 Numerical simulations were performed. Figure 38A The grating profile of a simulated transmission grating is shown. Figure 38B The grating profile of a simulated reflection grating is shown. Figure 38C It shows Figure 38B The metallized surface on the grating.

[0303] The presented data were obtained using the same materials (TiO2 as the material of the grating elements and sapphire (Al2O3) as the material of the substrate) and COMSOL Multiphysics software.

[0304] Figures 39 to 43 This paper presents a set of numerical simulations for optimizing two diffraction gratings with high refractive indices for TE polarization. We have assumed that n1 is the refractive index of the host medium and n1 = 1 (air). We have considered the combination of two diffraction gratings for a full RGB system with FoV = 91.74°.

[0305] Figures 39 to 41 The figure shows the simulated performance of the first transmission grating DG1 configured for blue light coupling at ±2nd order, with a spacing of d1 = 535.598 nm and elements having w1 = 80 nm; h1 = 110 nm; w'1 = 187.799 nm; h'1 = 10 nm. Using more complex U-shaped elements can provide better diffraction uniformity for blue light. Figure 39 The simulated performance of DG1 with blue light (λ = 460 nm) is shown. Figure 40 The simulated performance of DG1 with green light (λ = 530 nm) is shown. Figure 41 The simulated performance of DG1 with red light (λ = 620 nm) is shown.

[0306] Figure 42 and Figure 43 The diagram shows the simulated performance of a second reflective grating DG2 configured for red light, with a spacing of d2 = 749.67 nm and element parameters of: w2 = 140 nm; h2 = 380 nm; w'2 = 234.835 nm; h'2 = 10 nm. This grating converts a portion of the red light transmitted through the first diffraction grating (0th transmission order T0) into ±2nd diffraction orders coupled by the waveguide. To prevent transmission through the waveguide and increase the intensity of the diffracted light, some embodiments metallize the surface of the diffraction grating (see [reference]). Figure 38C ). Figures 42 to 43 The range of angles presented corresponds to incident from a medium with a refractive index n2. Using Snell's law, we can calculate the range corresponding to the medium n1. Figure 42 The simulated performance of the second reflective grating DG2 for green light is shown. Figure 43 The simulated performance of the second reflective grating DG2 for red light is shown.

[0307] The following discussion describes an exemplary embodiment of an external coupler configured to externally couple half of an RGB image diffracted toward the left from within a waveguide. The exemplary embodiment is configured to externally couple the incident image with an appropriate angular span.

[0308] To enable external coupling of the image coupled to the waveguide via diffraction gratings DG1 and DG2, some embodiments use two diffraction gratings DG3 (reflection grating) and DG4 (transmission grating) from both sides of the plate. Exemplary embodiments use the positive diffraction mode of DG1 to carry the right-hand side image (positive high incident angle on the inner coupler) in the right-hand direction, and use the negative mode to propagate the negative high incident angle in the opposite direction of the waveguide. For high incident angles at blue wavelengths and at green and red wavelengths, the negative incident angle is converted by diffraction grating DG1 to a negative order propagating in the left-hand direction; for high incident angles at blue wavelengths and at green and red wavelengths, the positive incident angle is converted by diffraction grating DG1 to a positive order propagating in the right-hand side direction of the waveguide. In exemplary embodiments, the outer coupler is configured to maintain the same angular span. For green and red, a positive low incidence angle will be directly transmitted by the diffraction grating DG1 and converted into a negative order of the reflected DG3 propagating in the left-hand direction, while a negative low incidence angle will be transformed into a positive mode and propagate in the right-hand direction of the waveguide. In an exemplary embodiment, the external coupler is configured to maintain the same angular span. For illustration, consider a portion of the image propagating to the left side of the waveguide, as shown regarding... Figure 44 and Figure 45 As shown.

[0309] To externally couple a portion of an image that is directly transmitted (a zero-order beam T0 transmitted without diffraction) at a low incident angle at red and green wavelengths by the first diffraction grating DG1 and converted to a positive diffraction order by the second reflection diffraction grating, an exemplary embodiment uses a diffraction grating with a spacing of d4. The waveguide thickness, as well as the size and position of the diffraction grating DG3, can be selected to avoid interaction between this portion of the image and DG3. Figure 44 , Angle range [Θ G 2; Θ C 2], where Θ C 2 is the critical incident angle for direct transmission through DG1, which is transmitted inside the waveguide and diffracted by DG2 within the waveguide into an angle range of [-Φ].G 2; -Φ C 2]. Therefore, the right-hand side of the image with a low incident angle will propagate towards the left. Finally, after multiple internal reflections, it will reach DG4. To obtain externally coupled light with the same angular space, the spacing size 4 of the waveguide's transmission diffraction grating DG4 can be selected using such a system of diffraction grating equations:

[0310]

[0311]

[0312] As mentioned earlier, assume n1 = 1, and... The angle is chosen to be approximately 75°. M4 corresponds to the diffraction order of diffraction grating DG4.

[0313] but, Considering the sign of the corresponding angle (for the reflection grating DG2: angle of incidence) The positive value indicates that the coupling diffraction order M2 is negative. Negative; for transmission grating DG4: angle of incidence The external coupling diffraction order M4 is positive. (For positive), the expression presented, compared with Equation 14, shows that in order to obtain the same angular span of the externally coupled light, d4 can be chosen such that d4 / M4 = -d2 / M2.

[0314] To externally couple a portion of the image (the portion of the image at high incident angles at blue wavelengths and green and red wavelengths) that is coupled by the waveguide through the first diffraction grating DG1 (specifically, the negative diffraction order) and thus avoid diffraction through DG2, a third diffraction grating with a spacing of d3 can be used. Figure 45 , Angle range [Θ C 1; Θ G 1] (High incident angle) diffracts inside the waveguide into an angle range propagating to the left [Φ c 1; Φ G 1). Finally, after multiple internal reflections, it will reach the reflection diffraction grating DG3, which has a spacing size selectable according to the diffraction equation system:

[0315]

[0316]

[0317] Here, and M3 is the grazing angle and critical angle of the reflection diffraction grating DG3, and M3 corresponds to the diffraction order of the diffraction grating DG3.

[0318] Therefore, the spacing of DG3 can be calculated as follows:

[0319]

[0320] Assuming that after this, the diffracted light should be directly transmitted by DG4 (making the angular range...) (corresponding to the 0th diffraction order) into a host medium with a refractive index n1 = 1 and an angular range [Θ] C 1; Θ G 1], we obtained and Then, the spacing of DG3 can be calculated using the following formula:

[0321]

[0322] Considering the sign of the corresponding angle (for transmission grating DG1: angle of incidence) The value is negative, and the coupling diffraction order M1 is negative. Negative; for grating DG3 (considering the e / m wave incident side): incident angle The external coupling diffraction order M3 is positive, while the negative value indicates a negative value. For positive, (For negative values), the expression presented and the comparison with equation (12) show that in order to obtain the same angular span of the externally coupled light, in some implementations, d3 can be selected such that d3 / M3 = -d1 / M1.

[0323] Due to the symmetrical response of the diffraction grating, we use the same reflective DG3 and transmittive DG4 gratings to externally couple half of the RGB image diffracted to the right.

[0324] In some implementations, the following formula is used to determine the acceptable range of spacing d1:

[0325]

[0326]

[0327] Here, λ 蓝 It is the wavelength of blue, λ 红 It's the wavelength of red.

[0328] In some implementations, n2 and n3 are between 1.5 and 2.0 and for M1 = 1 (λ 蓝 =460nm), the first grating spacing (d1) of the first transmission diffraction inner coupler is between 230nm and 390nm.

[0329] In some implementations, n2 and n3 are between 1.5 and 2.0 and for M1 = 2(λ蓝 =460nm), the first grating spacing (d1) of the first transmission diffraction inner coupler is between 460nm and 780nm.

[0330] In some implementations, this applies when n² is between 1.5 and 2.0 and when M² = 1 (λ... 红 =620nm), and the second grating spacing (d2) of the second reflection diffraction inner coupler is between 310nm and 520nm.

[0331] In some implementations, this applies when n² is between 1.5 and 2.0 and when M² = 2(λ). 红 =620nm), the second grating spacing (d2) of the second reflection diffraction inner coupler is between 620nm and 1040nm.

[0332] Some implementations use only a single waveguide to provide a high field of view for RGB images. Some such implementations operate to combine beams diffracted by reflection and transmission diffraction gratings placed from opposite sides of a glass plate. In some implementations, the refractive index of the waveguide is selected to increase the field of view.

[0333] Some implementations use a waveguide to provide a high field-of-view RGB display. The waveguide's internal coupler may include a single transmission diffraction grating and a single reflection diffraction grating. The transmission grating DG1 may be configured for blue light. The transmission grating DG1 may have a spacing within the range described by the formula given above. The reflection grating DG2 may be configured for red light. The reflection grating DG2 may have a spacing within the range described by the formula given above.

[0334] The waveguide may have an external coupler system, wherein the external coupler transmission grating has the same spacing and diffraction order as the internal reflective coupler. The external coupler reflection grating may have the same spacing and diffraction order as the internal transmitive coupler grating.

[0335] In some implementations, the diffraction grating has cells that allow edge wave behavior to form the far field.

[0336] In some implementations, a metal layer is provided to cover the reflective grating.

[0337] In some implementations, all diffraction gratings use |M| greater than or equal to 1 for the inner coupler to achieve high diffraction efficiency.

[0338] Some implementations use two diffraction modes at each location of the internally coupled diffraction grating to achieve pupil angle tiling.

[0339] Some implementations use pupil angle tiling to multiplex different angle spaces and wavelengths among multiple diffraction gratings.

[0340] In some implementations, the internal coupler diffraction grating is compatible with a variety of different optical engine sources (such as DLP or LCOS) to achieve low light loss.

[0341] In this disclosure, modifiers such as “first,” “second,” and “third” are sometimes used to distinguish different features. These modifiers do not imply any particular order of operation or arrangement of components. Furthermore, the terms “first,” “second,” “third,” etc., may have different meanings in different embodiments. For example, in one embodiment, a component that is a “first” component may be a “second” component in a different embodiment.

[0342] Additional Implementation Plan

[0343] An optical system according to some embodiments includes a first waveguide having a first transmission diffraction inner coupler (DG1) and a second waveguide having a second transmission diffraction inner coupler (DG2) and a reflection diffraction inner coupler (DG3), wherein the second transmission diffraction inner coupler (DG2) is arranged in the input region between the first transmission diffraction inner coupler (DG1) and the reflection diffraction inner coupler (DG3).

[0344] In some implementations, the first waveguide further includes a first diffractive external coupler (DG6); and the second waveguide further includes a second diffractive external coupler (DG4) and a third diffractive external coupler (DG5).

[0345] In some implementations, the optical system also includes an image generator that operates to provide an image at an input region, wherein the optical system is configured to substantially replicate the image at an output pupil region that includes a first diffraction external coupler (DG6), a second diffraction external coupler (DG4), and a third diffraction external coupler (DG5).

[0346] In some embodiments, the system is configured to substantially replicate images spanning a field of view of at least 100°. In some embodiments, the system is configured to substantially replicate images spanning a field of view of at least 120°. In some embodiments, the system is configured to substantially replicate images spanning a field of view of at least 140°. In some embodiments, the system is configured to substantially replicate images spanning a field of view of at least 160°.

[0347] In some implementations, the image generator operates to produce light with the maximum wavelength, and the system's field of view is equal to the maximum field of view for the maximum wavelength.

[0348] In some implementations, the system is configured to reproduce panchromatic images.

[0349] In some implementations, the first diffraction inner coupler has a first grating spacing, the second diffraction inner coupler has a second grating spacing greater than the first grating spacing, and the reflection diffraction inner coupler has a third grating spacing greater than the second grating spacing.

[0350] Some implementations of this optical system are characterized by the following equations:

[0351]

[0352] Where d1 is the grating spacing of the first transmission diffraction inner coupler (DG1), M1 is a non-zero integer, n2 is the refractive index of the first waveguide, and λ is the wavelength between 450 nm and 700 nm. It is an angle between 55 degrees and 90 degrees, and It is essentially equal to the angle diffracted at the critical angle of the second waveguide, where the critical angle of the second waveguide is arcsin(1 / n3).

[0353] Some implementations of this optical system are characterized by the following equations:

[0354]

[0355] Where d2 is the grating spacing of the second transmission diffraction inner coupler (DG2), M2 is a non-zero integer, n3 is the refractive index of the second waveguide, and λ is the wavelength between 450 nm and 700 nm. It is an angle between 55 degrees and 90 degrees, and It is the angle within ±5 degrees of normal incidence.

[0356] In some embodiments, the optical system operates to couple light with an incident angle greater than 50° to at least one of the first and second waveguides. In some embodiments, the optical system operates to couple light with an incident angle greater than 60° to at least one of the first and second waveguides. In some embodiments, the optical system operates to couple light with an incident angle greater than 70° to at least one of the first and second waveguides. In some embodiments, the optical system operates to couple light with an incident angle greater than 80° to at least one of the first and second waveguides.

[0357] In some embodiments, the optical system is configured to: (i) couple at least some incident light having a first incident angle to travel in a first direction in at least one of a first waveguide and a second waveguide, and (ii) couple at least some incident light having a second incident angle substantially opposite to the first incident angle to travel in a second direction substantially opposite to the first direction in at least one of a first waveguide and a second waveguide.

[0358] In some embodiments, the optical system is configured such that light incident on a first transmission diffraction inner coupler for at least a first wavelength is preferentially coupled into a first waveguide at a relatively high incident angle and (ii) preferentially coupled into a second waveguide at a relatively low incident angle.

[0359] In some embodiments, the optical system is configured such that light incident on the second transmission diffraction inner coupler for at least a second wavelength is: (i) preferentially coupled to the second waveguide via the second transmission diffraction inner coupler at a relatively high incident angle, and (ii) preferentially coupled to the second waveguide via the reflection diffraction inner coupler at a relatively low incident angle.

[0360] In some implementations, the first wavelength is shorter than the second wavelength.

[0361] In some implementations, the incident light is blue light with a first wavelength of about 460 nm.

[0362] In some implementations, the incident light is green light with a first wavelength of about 530 nm.

[0363] In some implementations, the incident light is red light with a second wavelength of approximately 625 nm.

[0364] In some embodiments, the optical system is configured such that for at least one light incident angle at the input region: (i) light with a relatively short wavelength is preferentially coupled into a first waveguide, and (ii) light with a relatively long wavelength is preferentially coupled into a second waveguide.

[0365] In some embodiments, the optical system is configured such that at least a portion of the first wavelength light and at least a portion of the second wavelength light incident on the input region are coupled into a first waveguide.

[0366] In some embodiments, the optical system is configured such that at least a portion of the first wavelength light and at least a portion of the second wavelength light incident on the input region are coupled into a second waveguide.

[0367] In some implementations, the first grating spacing (d1) of the first transmission diffraction inner coupler is between 420 nm and 520 nm.

[0368] In some implementations, the second grating spacing (d2) of the second transmission diffraction inner coupler is between 600 nm and 700 nm.

[0369] In some implementations, the third grating spacing (d3) of the reflective diffraction inner coupler is between 720 nm and 820 nm.

[0370] In some implementations, the first grating spacing (d1) of the first transmission diffraction inner coupler is between 460 nm and 480 nm.

[0371] In some implementations, the second grating spacing (d2) of the second transmission diffraction inner coupler is between 640 nm and 660 nm.

[0372] In some implementations, the third grating spacing (d3) of the reflective diffraction inner coupler is between 760 nm and 780 nm.

[0373] In some implementations, the second grating spacing is between 30% and 50% larger than the first grating spacing.

[0374] In some implementations, the third grating spacing is between 10% and 30% larger than the second grating spacing.

[0375] In some implementations, the third grating spacing is between 50% and 70% larger than the second grating spacing.

[0376] In some implementations, the first transmission diffraction inner coupler operates to couple light of the second diffraction order into the first waveguide.

[0377] In some implementations, the second transmission diffraction inner coupler and the reflection diffraction inner coupler operate to couple the light of the second diffraction order into the second waveguide.

[0378] In some embodiments, the first waveguide includes at least one pupil expander along an optical path between the first transmission diffraction inner coupler and the first diffraction outer coupler.

[0379] In some embodiments, the second waveguide includes at least one pupil expander along an optical path between (i) the second transmission diffraction inner coupler and the reflection diffraction inner coupler and (ii) the second diffraction outer coupler and the third diffraction outer coupler.

[0380] In some implementations, the second waveguide includes at least two pupil dilators along optical paths between (i) the second transmission diffraction inner coupler and the reflection diffraction inner coupler and (ii) the second diffraction outer coupler and the third diffraction outer coupler.

[0381] In some implementations, the first diffraction external coupler (DG6) is a reflection diffraction external coupler.

[0382] In some implementations, the first diffraction external coupler (DG6) is a transmission diffraction external coupler.

[0383] In some implementations, the second diffraction external coupler (DG4) is a reflection diffraction external coupler.

[0384] In some implementations, the second diffraction external coupler (DG4) is a transmission diffraction external coupler.

[0385] In some implementations, the third diffraction external coupler (DG5) is a transmission diffraction external coupler.

[0386] In some implementations, the third diffraction external coupler (DG5) is a reflection diffraction external coupler.

[0387] In some implementations, the first diffraction outer coupler has a grating spacing (d6) that is substantially equal to the grating spacing (d1) of the first transmission diffraction inner coupler.

[0388] In some implementations, the second diffraction outer coupler has a grating spacing (d4) that is substantially equal to the grating spacing (d2) of the second transmission diffraction inner coupler.

[0389] In some implementations, the third diffraction outer coupler has a grating spacing (d5) that is substantially equal to the grating spacing (d3) of the reflection diffraction inner coupler.

[0390] In some implementations, the first and second waveguides are substantially planar and substantially parallel to each other.

[0391] In some implementations, the first and second waveguides are arranged as a waveguide stack comprising only two waveguides.

[0392] In some implementations, the optical system is configured such that blue light: (i) preferentially couples into a first waveguide at a relatively high incident angle, and (ii) preferentially couples into a second waveguide at a relatively low incident angle.

[0393] In some implementations, the optical system is configured such that green light: (i) preferentially couples into a first waveguide at a relatively high incident angle, and (ii) preferentially couples into a second waveguide at a relatively low incident angle.

[0394] In some embodiments, the optical system is configured such that red light: (i) preferentially couples into the second waveguide via the second transmission diffraction inner coupler at a relatively high incident angle, and (ii) preferentially couples into the second waveguide via the reflection diffraction inner coupler at a relatively low incident angle.

[0395] A method of operating an optical system according to some embodiments includes: directing input light representing an image onto a first transmission diffraction inner coupler (DG1) of a first waveguide, the first waveguide having a first diffraction outer coupler (DG6); coupling a first portion of the input light into the first waveguide using the first transmission diffraction inner coupler (DG1); coupling a second portion of the input light into a second waveguide using a second transmission diffraction inner coupler (DG2) of a second waveguide; and coupling a third portion of the input light into the second waveguide using a reflection diffraction inner coupler (DG3) of the second waveguide.

[0396] In some embodiments, the method further includes: using a first diffraction external coupler (DG6) on a first waveguide to couple at least a portion of a first portion of the light out of the first waveguide; using a second diffraction external coupler (DG4) on a second waveguide to couple at least a portion of a second portion of the light out of the second waveguide; and using a third diffraction external coupler (DG5) on the second waveguide to couple at least a portion of a third portion of the light out of the second waveguide.

[0397] In some implementations, when the input light includes blue light, the blue light: (i) preferentially couples into the first waveguide at a relatively high incident angle, and (ii) preferentially couples into the second waveguide at a relatively low incident angle.

[0398] In some implementations, when the input light includes green light, the green light: (i) preferentially couples into the first waveguide at a relatively high incident angle, and (ii) preferentially couples into the second waveguide at a relatively low incident angle.

[0399] In some implementations, the input light includes red light, and the red light: (i) preferentially couples into the second waveguide via the second transmission diffraction inner coupler at a relatively high incident angle, and (ii) preferentially couples into the second waveguide via the reflection diffraction inner coupler at a relatively low incident angle.

[0400] An optical system according to some embodiments includes a waveguide having a transmission diffraction inner coupler (DG1) on a first surface and a reflection diffraction inner coupler (DG2) on a second surface substantially opposite to the first surface, wherein the transmission diffraction inner coupler (DG1) has a grating period selected to couple blue light into the waveguide, and wherein the reflection diffraction inner coupler (DG2) has a grating period selected to couple red light into the waveguide.

[0401] In some implementations, the waveguide further includes at least one external reflective diffraction coupler and at least one external transmittive diffraction coupler.

[0402] In some embodiments, the optical system further includes an image generator that operates to provide an image at an input region including an inner transmission diffraction coupler and an inner reflection diffraction coupler, wherein the optical system is configured to substantially replicate the image at at least one output pupil region including an outer reflection diffraction coupler and an outer transmission diffraction coupler.

[0403] Although the features and elements have been described above in specific combinations, those skilled in the art will understand that each feature or element may be used alone or in any combination with other features and elements.

Claims

1. An optical system, comprising: The first waveguide has a first transmission diffraction inner coupler (DG1) and a first diffraction outer coupler (DG6). as well as The second waveguide has a second transmission diffraction inner coupler (DG2), a reflection diffraction inner coupler (DG3), a second diffraction outer coupler (DG4), and a third diffraction outer coupler (DG5). The second transmission diffraction inner coupler (DG2) is arranged in the input region between the first transmission diffraction inner coupler (DG1) and the reflection diffraction inner coupler (DG3); And among them: (a) Blue light incident at an angle greater than the first critical angle and less than the grazing angle is coupled into the first waveguide through the first transmission diffraction inner coupler (DG1), while blue light at an angle less than the first critical angle is transmitted and coupled into the second waveguide through the second transmission diffraction inner coupler (DG2). (b) Green light incident at an angle greater than the second critical angle and less than the grazing angle is coupled into the first waveguide through the first transmission diffraction inner coupler (DG1), while green light at an angle less than the second critical angle is transmitted and coupled into the second waveguide through the second transmission diffraction inner coupler (DG2). (c) The red light transmitted through the first waveguide is coupled into the second waveguide through the second transmission diffraction inner coupler (DG2) at an angle greater than the third critical angle and less than the grazing angle, and is coupled into the second waveguide through the reflection diffraction inner coupler (DG3) at an angle less than the third critical angle; (d) The external coupling is configured such that blue and green light are coupled out through the first diffraction external coupler (DG6) and the third diffraction external coupler (DG5), while red light with an angle smaller than the third critical angle is coupled out through the third diffraction external coupler (DG5), and red light with an angle greater than the third critical angle is coupled out through the second diffraction external coupler (DG4).

2. The optical system of claim 1, further comprising an image generator that operates to provide an image at the input region, wherein the optical system is configured to reproduce the image at an output region, the output region comprising the first diffraction external coupler (DG6), the second diffraction external coupler (DG4), and the third diffraction external coupler (DG5).

3. The optical system of claim 1 or 2, wherein the optical system is configured to reproduce an image spanning a field of view of at least 100°.

4. The optical system of claim 1 or 2, wherein the optical system is configured to reproduce a panchromatic image.

5. The optical system according to claim 1 or 2, wherein the first transmission diffraction inner coupler has a first grating spacing, the second transmission diffraction inner coupler has a second grating spacing greater than the first grating spacing, and the reflection diffraction inner coupler has a third grating spacing greater than the second grating spacing.

6. The optical system according to claim 1 or 2, wherein in It is the grating spacing of the first transmission diffraction inner coupler (DG1). It is a non-zero integer. It is the refractive index of the first waveguide. It is a wavelength between 450nm and 700nm. It is an angle between 55 degrees and 90 degrees, and Equal to the angle diffracted at the critical angle of the second waveguide, wherein the critical angle of the second waveguide is arcsin(1 / ),in It is the refractive index of the second waveguide.

7. The optical system according to claim 1 or 2, wherein in It is the grating spacing of the second transmission diffraction inner coupler. It is a non-zero integer. It is an angle between 55 degrees and 90 degrees, and It is the angle within ±5 degrees of the normal incidence. It is the refractive index of the second waveguide, and It is a wavelength between 450nm and 700nm.

8. The optical system of claim 1 or 2, wherein the optical system is configured to: (i) couple at least some incident light having a first incident angle to travel in a first direction in at least one of the first waveguide and the second waveguide, and (ii) couple at least some incident light having a second incident angle opposite to the first incident angle to travel in a second direction opposite to the first direction in at least one of the first waveguide and the second waveguide.

9. The optical system according to claim 1 or 2, wherein: The first grating spacing (d1) of the first transmission diffraction inner coupler is between 420 nm and 520 nm; The second grating spacing (d2) of the second transmission diffraction inner coupler is between 600 nm and 700 nm; and The third grating spacing (d3) of the internal coupler for reflection diffraction is between 720 nm and 820 nm.

10. The optical system according to claim 1 or 2, wherein: The first grating spacing (d1) of the first transmission diffraction inner coupler is between 460 nm and 480 nm; The second grating spacing (d2) of the second transmission diffraction inner coupler is between 640 nm and 660 nm; and The third grating spacing (d3) of the internal coupler for reflection diffraction is between 760 nm and 780 nm.

11. The optical system according to claim 1 or 2, wherein: The second grating spacing (d2) of the second transmission diffraction inner coupler is between 30% and 50% larger than the first grating spacing (d1) of the first transmission diffraction inner coupler; and The third grating spacing (d3) of the internal coupler of the reflection diffraction is between 10% and 30% larger than the second grating spacing.

12. A method of operating an optical system, said optical system comprising: The first waveguide has a first transmission diffraction inner coupler (DG1) and a first diffraction outer coupler (DG6). as well as The second waveguide has a second transmission diffraction inner coupler (DG2), a reflection diffraction inner coupler (DG3), a second diffraction outer coupler (DG4), and a third diffraction outer coupler (DG5). The second transmission diffraction inner coupler (DG2) is arranged in the input region between the first transmission diffraction inner coupler (DG1) and the reflection diffraction inner coupler (DG3); And among them: (a) Blue light incident at an angle greater than the first critical angle and less than the grazing angle is coupled into the first waveguide through the first transmission diffraction inner coupler (DG1), while blue light at an angle less than the first critical angle is transmitted and coupled into the second waveguide through the second transmission diffraction inner coupler (DG2). (b) Green light incident at an angle greater than the second critical angle and less than the grazing angle is coupled into the first waveguide through the first transmission diffraction inner coupler (DG1), while green light at an angle less than the second critical angle is transmitted and coupled into the second waveguide through the second transmission diffraction inner coupler (DG2). (c) The red light transmitted through the first waveguide is coupled into the second waveguide through the second transmission diffraction inner coupler (DG2) at an angle greater than the third critical angle and less than the grazing angle, and is coupled into the second waveguide through the reflection diffraction inner coupler (DG3) at an angle less than the third critical angle; (d) The external coupling is configured such that blue and green light are coupled out through the first diffraction external coupler (DG6) and the third diffraction external coupler (DG5), while red light with an angle smaller than the third critical angle is coupled out through the third diffraction external coupler (DG5), and red light with an angle greater than the third critical angle is coupled out through the second diffraction external coupler (DG4).

13. The method of claim 12, wherein in It is the grating spacing of the first transmission diffraction inner coupler. It is a non-zero integer. It is the refractive index of the first waveguide. It is a wavelength between 450nm and 700nm. It is an angle between 55 degrees and 90 degrees, and Equal to the angle diffracted at the critical angle of the second waveguide, wherein the critical angle of the second waveguide is arcsin(1 / ),in It is the refractive index of the second waveguide.

14. The method according to claim 12 or 13, wherein in It is the grating spacing of the second transmission diffraction inner coupler (DG2). It is a non-zero integer. It is an angle between 55 degrees and 90 degrees, and It is the angle within ±5 degrees of the normal incidence. It is the refractive index of the second waveguide, and It is a wavelength between 450nm and 700nm.

Images