Thin waveguide imager

Abstract

A device for providing a 1D line of an image is disclosed. The device is based on a thin slab waveguide coupled to a beam redirection device, such as a tiltable mirror MEMS scanner, a waveguide-based phased array, or a waveguide-based optical switch that switches image light between waveguides in a waveguide array coupled to collimating elements formed in a low-mode slab waveguide. The image can be formed by scanning a collimated beam propagating in the slab waveguide or by simultaneously forming a 1D singular distribution of brightness. The device can be used in a near-eye display to form a 2D image in the angular domain.

Description

Technical Field

[0001] The present disclosure relates to optical devices, and in particular to display systems and modules.

[0002] background

[0003] Head-mounted displays (HMDs), helmet-mounted displays, near-eye displays (NEDs), etc. are increasingly being used to display virtual reality (VR) content, augmented reality (AR) content, mixed reality (MR) content, etc. Such displays are used in a variety of fields including entertainment, education, training, and biomedical sciences, to name just a few. The VR / AR / MR content displayed can be three-dimensional (3D) to enhance the experience and match virtual objects with real objects observed by the user.

[0004] To provide better optical performance, display systems and modules may include a large number of components, such as lenses, waveguides, display panels, etc. Because the display of an HMD or NED is usually worn on the user's head, a large, bulky, unbalanced and / or heavy display device would be inconvenient and may be uncomfortable for the user to wear. Compact, lightweight and efficient head-mounted display devices and modules are desired.

[0005] Overview

[0006] According to a first aspect of the present disclosure, a device for providing image lines in an angular domain is provided. The device includes a low-mode waveguide. The low-mode waveguide includes: an in-coupler for coupling image light into the low-mode waveguide; a 1×N beamsplitter for splitting the image light coupled by the in-coupler into N linear waveguides; N phase shifters, each coupled to a specific one of the N linear waveguides for delaying the image light portion propagating in the N linear waveguides by a controllable amount; an array of N linear waveguide transmitters, each linear waveguide transmitter coupled to a specific one of the N phase shifters for emitting the image light portion delayed thereby; and a slab waveguide portion coupled to an array of N linear waveguide transmitters for propagating therein the delayed image light portion emitted by a corresponding transmitter in the array of N linear waveguide transmitters, wherein N is an integer.

[0007] In some embodiments, the slab waveguide portion comprises a single mode slab waveguide.

[0008] In some embodiments, the slab waveguide portion includes a few-mode slab waveguide supporting no more than 10 lateral modes of propagation.

[0009] The 1×N beamsplitter may preferably comprise a binary tree of tunable Mach-Zehnder interferometers for providing a controllable distribution of the optical power of the image light among the N linear waveguides.

[0010] The slab waveguide portion may preferably also include a field of view (FOV) expander in the slab waveguide portion, the FOV expander comprising a tunable cladding portion that is instantaneously coupled to the core of the slab waveguide portion and is shaped to deviate light propagating in the core of the slab waveguide portion by a controllable amount.

[0011] In some embodiments, the tunable cladding portion includes an array of triangular liquid crystal cladding portions extending laterally relative to an optical path of the image light in the core of the slab waveguide portion, wherein at least some of the triangular liquid crystal cladding portions have sides extending at an acute angle relative to the optical path.

[0012] In some embodiments, the slab waveguide portion also includes a hologram, which is configured to reflect the collimated beam portion of the image light in the hologram at multiple positions along the optical path of the collimated beam portion, so that the collimated beam portion reflected by the hologram is wider than the collimated beam portion impacting the hologram.

[0013] According to a second aspect of the present disclosure, there is provided a device for providing image lines in an angular domain, the device comprising a low-mode waveguide, the low-mode waveguide comprising: an inner coupler for coupling image light into the low-mode waveguide; a tunable 1×N splitter for distributing the optical power of the image light coupled by the inner coupler between linear waveguides in an array of N linear waveguides; and a slab waveguide portion comprising a collimating element for converting the lateral positioning of the linear waveguides in the array of N linear waveguides into a beam angle of the image light portion propagating in the linear waveguides in the array of N linear waveguides, wherein N is an integer.

[0014] In some embodiments, the slab waveguide portion comprises a single mode slab waveguide.

[0015] In some embodiments, the slab waveguide portion includes a few-mode slab waveguide supporting no more than 10 lateral propagation modes.

[0016] In some embodiments, the 1xN beamsplitter includes a binary tree of Mach-Zehnder switches for switching the image light between the N linear waveguides.

[0017] In some embodiments, the slab waveguide portion further includes a field of view (FOV) expander in the slab waveguide portion, the FOV expander comprising a tunable cladding portion instantaneously coupled to the core of the slab waveguide portion and shaped to deviate light propagating in the core of the slab waveguide portion by a controllable amount.

[0018] In some embodiments, the tunable cladding portion includes an array of triangular liquid crystal cladding portions extending laterally relative to an optical path of the image light in the core of the slab waveguide portion, wherein at least some of the triangular liquid crystal cladding portions have sides extending at an acute angle relative to the optical path.

[0019] The slab waveguide portion may preferably also include a hologram, which is configured to reflect the collimated beam portion of the image light in the hologram at multiple positions along the optical path of the collimated beam portion, so that the collimated beam portion reflected by the hologram is wider than the collimated beam portion impacting the hologram.

[0020] According to a third aspect of the present invention, there is provided a device for providing image lines in an angular domain, the device comprising: a microelectromechanical system (MEMS) beam scanner comprising a tiltable reflector for scanning image light in a first plane; a low-mode slab waveguide in the first plane for propagating the image light scanned by the MEMS beam scanner; and a coupler for receiving the image light scanned by the MEMS beam scanner and coupling the image light to the low-mode slab waveguide.

[0021] The low-mode slab waveguide may be a single-mode slab waveguide.

[0022] The low-mode slab waveguide may be a few-mode slab waveguide supporting no more than 10 lateral propagation modes.

[0023] In some embodiments, the low-mode slab waveguide also includes a field of view (FOV) expander in the slab waveguide portion, the FOV expander including a tunable cladding portion that is instantaneously coupled to the core of the low-mode slab waveguide and is shaped to deviate light propagating in the core of the slab waveguide portion by a controllable amount.

[0024] In some embodiments, the tunable cladding portion comprises an array of triangular liquid crystal cladding portions extending laterally relative to an optical path of the image light in the core of the low-mode slab waveguide, wherein at least some of the triangular liquid crystal cladding portions have sides extending at an acute angle relative to the optical path.

[0025] In some embodiments, the low-mode slab waveguide also includes a hologram, which is configured to reflect the collimated beam portion of the image light in the hologram at multiple positions along the optical path of the collimated beam portion, so that the collimated beam portion reflected by the hologram is wider than the collimated beam portion impacting the hologram. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Exemplary embodiments will now be described with reference to the accompanying drawings, in which:

[0028] Figure 1A is a 3D view of a device for redirecting light in two dimensions, the device comprising a low-mode waveguide;

[0029] Figure 1B yes Figure 1A A side cross-sectional view of a low mode waveguide;

[0030] Figure 1C It is shown by Figure 1A A schematic diagram of an image presented by a device in FIG.

[0031] Figure 2 yes Figure 1A and Figure 1B A system level block diagram of an embodiment of the device in;

[0032] Figure 3 yes Figure 2 A schematic front view of a near-eye display embodiment of the device in;

[0033] Figure 4A yes Figure 3 A schematic front view of an embodiment of a photonic integrated circuit (PIC) for a near-eye display in FIG.

[0034] Figure 4B and Figure 4C Wear Figure 4A Side and top views of a person using a near-eye display device;

[0035] Figure 5 is a schematic side view of a wavelength tunable light source including an intracavity spectrally selective element;

[0036] Fig. 6A is a schematic side view of a tunable spectral light source including an external dynamic spectral selection element;

[0037] Figure 6B is the output spectrum of the light source superimposed with the transmission spectrum of the spectrally selective element, used to show Fig. 6A Working principle of tunable spectrum light source in;

[0038] Figure 6C yes Fig. 6A The output spectrum of the light source in ;

[0039] Figure 7 is a side cross-sectional view of a free-space grating coupler for coupling light into a waveguide;

[0040] Figure 8 is a side cross-sectional view of an adiabatic waveguide coupler for coupling light into a waveguide;

[0041] Fig. 9 is a schematic diagram of a phased array 1D imager of the present disclosure;

[0042] Fig. 10A yes Fig. 9 Schematic top view of a PIC implementation of a phased array 1D imager in FIG.

[0043] Fig. 10B yes Fig. 10A Schematic top view of a PIC implementation of a Mach-Zehnder interferometer (MZI) array (MZIA) of a PIC 1D imager in FIG.

[0044] Fig. 10C yes Fig. 10B Schematic top view of a single MZI in;

[0045] Fig. 10D yes Fig. 10A Schematic top view of the phase shifter array (PSA) of the PIC 1D imager in FIG.

[0046] Fig.10E yes Fig. 10A Schematic top view of the implementation of the waveguide fan of the PIC 1D imager in FIG.

[0047] Fig.11 is a schematic top view of a hybrid 1D imager including a 1D lens etched in a waveguide;

[0048] Fig.12 is a schematic diagram of a free space optics (FSO) implementation of a 1D scanner including a micro-electromechanical system (MEMS) tiltable reflector;

[0049] Fig.13A is a top schematic view of a field of view (FOV) extender based on a liquid crystal (LC) cladding waveguide;

[0050] Fig. 13B yes Fig.13A Side cross-sectional view of the FOV extender in FIG.

[0051] Fig.14is a schematic top view of a holographic-based beam expander according to the present disclosure;

[0052] Fig.15 is a schematic top view of a PIC implementation of a phased array 1D imager with a beam expander;

[0053] Fig.16 is a side cross-sectional view of an output waveguide for illustrating angular dispersion calculations;

[0054] Fig.17 is a side cross-sectional view of a dual-core waveguide for widening the angular dispersion range of an out-coupler;

[0055] Fig.18 is a top view of the few-mode waveguide (FMW) used to broaden the angular dispersion range of the outcoupler;

[0056] Fig.19 is a side cross-sectional view of a high-dispersion outcoupler based on a slow-light waveguide;

[0057] Fig. 20A is a side cross-sectional view of a high-dispersion outcoupler based on a waveguide grating and a corrugated reflector;

[0058] Fig. 20B is a side cross-sectional view of a high dispersion outcoupler based on a waveguide grating and a polarization selective corrugated reflector;

[0059] Fig.21A and Fig. 21B is a schematic side view of a low-mode slab waveguide with a refractive index gradient for variably focusing or defocusing image light coupled out of the waveguide;

[0060] Fig. 22 is a side cross-sectional view of an embodiment of a variable focus outcoupler based on a tilted liquid crystal (LC) cell;

[0061] Fig.23 is a side cross-sectional view of an embodiment of a zoom outer coupler based on a wedge-shaped Pockels cell;

[0062] Fig.24 is a side cross-sectional view of an embodiment of a variable focus outer coupler based on a Pockels cell with buried electrodes;

[0063] Fig.25 is a side cross-sectional view of an embodiment of a variable focus outer coupler based on a thermo-optic effect;

[0064] Fig.26 is a flow chart of a method for providing an image in an angle domain;

[0065] Fig. 27 yes Fig.26 A flowchart of a variation of the method utilizing 1D scanning / rendering at a set wavelength;

[0066] Fig.28 yes Fig.26 A flowchart of a method for simultaneously generating variants of image frames to be displayed;

[0067] Fig.29 is an illustration of an augmented reality (AR) display of the present disclosure having the form factor of a pair of glasses; and

[0068] Fig.30 is an isometric view of a virtual reality (VR) display according to an embodiment of the present disclosure.

[0069] Detailed Description

[0070] Although this teaching is described in conjunction with various embodiments and examples, it is not intended that this teaching be limited to such embodiments. On the contrary, this teaching includes various substitutions and equivalents, as understood by those skilled in the art. All statements describing the principles, aspects and embodiments of the present disclosure and its specific examples herein are intended to include their structural and functional equivalents. In addition, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, that is, any element developed to perform the same function, without considering structure.

[0071] As used herein, unless explicitly stated, the terms "first," "second," etc. are not intended to imply a sequential order, but rather are intended to distinguish one element from another. Similarly, unless explicitly stated, the sequential order of method steps does not imply a sequential order in which they are performed. Figure 1A , Figure 1B , Figure 2 , Figure 3 , Figure 4A , Figure 5 , Fig. 6A , Figure 7-Figure 9 , Figure 10A-10E , Fig.11 , Fig.12 , Fig.13A , Fig. 13B ,and Figure 14-Figure 25 In the drawings, like reference numerals denote like elements.

[0072] Near-eye displays (NEDs) can use pupil-replicating waveguides to expand the projected image over the display's eyebox, i.e., over the area where the user's eyes are likely to be located during normal operation, such as when the display is worn by a user. Pupil-replicating waveguides are typically parallel plates of transparent material that propagate image light in a zigzag pattern from the top and bottom surfaces of the waveguide by total internal reflection (TIR). Such waveguides can be prone to diffraction effects that cause color dispersion that varies depending on the field angle, and are generally not suitable for curved substrates and exhibit ghosting for real-world close-up objects.

[0073] According to the present disclosure, single-mode (SM) waveguides or few-mode (FM) waveguides (collectively referred to herein as "low-mode" waveguides) can be used to deliver light to a viewing window and form an image. One advantage of low-mode waveguides is that light interacts with a grating several orders of magnitude more than with a conventional multimode waveguide. Therefore, for each individual interaction, the diffraction efficiency of the grating can be small enough to reduce or eliminate see-through artifacts such as rainbows and improve the conspicuity of the display. In addition, single-mode waveguides can more precisely control the distribution of light on the viewing window, which results in better uniformity and efficiency.

[0074] One challenge with using a single mode waveguide is that it only has the ability to transmit 1D information, for example, horizontal resolution without vertical resolution, or vertical resolution without horizontal resolution. This limitation can be overcome by encoding other components of a 2D image in non-spatial properties of light such as wavelength, for example. The wavelength range used for each color channel can be small enough not to significantly reduce the color gamut.

[0075] According to the present disclosure, a device for providing image lines in an angular domain is provided. The device includes a low-mode waveguide, the low-mode waveguide including an inner coupler for coupling image light into the low-mode waveguide; a 1×N beamsplitter for splitting the image light coupled by the inner coupler into N linear waveguides; N phase shifters, each coupled to a specific one of the N linear waveguides, for delaying the image light portion propagating therein by a controllable amount; an array of N linear waveguide transmitters, each linear waveguide transmitter coupled to a specific one of the N phase shifters, for transmitting the image light portion delayed thereby; and a slab waveguide portion, the slab waveguide portion coupled to an array of N linear waveguide transmitters, for propagating therein the delayed image light portion emitted by a corresponding transmitter in the array of the N linear waveguide transmitters, where N is an integer. The slab waveguide portion may include, for example, a single-mode slab waveguide, or a few-mode slab waveguide supporting no more than 10 lateral propagation modes. The 1×N beamsplitter may include a binary tree of tunable Mach-Zehnder interferometers for providing controllable distribution of optical power of the image light among the N linear waveguides.

[0076] In some embodiments, the slab waveguide portion further includes a field of view (FOV) expander in the slab waveguide portion. The FOV expander may include a tunable cladding portion that is transiently coupled to the core of the slab waveguide portion and is shaped to deviate light propagating in the core of the slab waveguide portion by a controllable amount. The tunable cladding portion may include an array of triangular shaped liquid crystal cladding portions that extend laterally relative to an optical path of the image light in the core of the slab waveguide portion. At least some of the triangular shaped liquid crystal cladding portions may have sides that extend at an acute angle relative to the optical path.

[0077] In some embodiments, the slab waveguide portion also includes a hologram, which is configured to reflect the collimated beam portion of the image light in the hologram at multiple positions along the optical path of the collimated beam portion, so that the collimated beam portion reflected by the hologram is wider than the collimated beam portion impacting the hologram.

[0078] According to the present disclosure, a device for providing image lines in an angular domain is provided. The device may include a low-mode waveguide, the low-mode waveguide including an inner coupler for coupling image light into the low-mode waveguide; a tunable 1×N beam splitter for distributing the optical power of the image light coupled by the inner coupler between the linear waveguides in an array of N linear waveguides; and a slab waveguide portion, the slab waveguide portion including a collimating element for converting the lateral positioning of the linear waveguides in the array of N linear waveguides into a beam angle of the image light portion propagating in the linear waveguides in the array of N linear waveguides, where N is an integer.

[0079] The slab waveguide portion may include, for example, a single-mode slab waveguide or a few-mode slab waveguide supporting no more than 10 lateral propagation modes. The 1×N beamsplitter may include a binary tree of Mach-Zehnder switches for switching image light between N linear waveguides. In some embodiments, the slab waveguide portion also includes a field of view (FOV) expander in the slab waveguide portion. The FOV expander may include a tunable cladding portion that is instantaneously coupled to the core of the slab waveguide portion and is shaped to deviate light propagating in the core of the slab waveguide portion by a controllable amount. The tunable cladding portion may include an array of triangular liquid crystal cladding portions that extend laterally relative to the optical path of the image light in the core of the slab waveguide portion. At least some of the triangular liquid crystal cladding portions may have sides that extend at an acute angle relative to the optical path. The slab waveguide portion may also include a hologram configured to reflect the collimated beam portion of the image light in the hologram at multiple locations along the optical path of the collimated beam portion, so that the collimated beam portion reflected by the hologram is wider than the collimated beam portion impacting the hologram.

[0080] According to the present disclosure, a device for providing an image line in an angle domain is also provided. The device may include a microelectromechanical system (MEMS) beam scanner, the microelectromechanical system (MEMS) beam scanner including a tiltable reflector for scanning image light in a first plane; a low-mode slab waveguide in the first plane, the low-mode slab waveguide for propagating the image light scanned by the MEMS beam scanner; and a coupler for receiving the image light scanned by the MEMS beam scanner and coupling the image light to the low-mode slab waveguide. The low-mode slab waveguide may include, for example, a single-mode slab waveguide or a few-mode slab waveguide supporting no more than 10 lateral propagation modes. The low-mode slab waveguide may also include a field of view (FOV) expander in the slab waveguide portion. The FOV expander may include a tunable cladding portion that is instantaneously coupled to the core of the low-mode slab waveguide and is shaped to deviate the light propagating in the core of the slab waveguide portion by a controllable amount.

[0081] In some embodiments, the tunable cladding portion includes an array of triangular liquid crystal cladding portions extending laterally relative to an optical path of the image light in the core of the low-mode slab waveguide. At least some of the triangular liquid crystal cladding portions may have sides extending at an acute angle relative to the optical path. The low-mode slab waveguide may also include a hologram configured to reflect a collimated beam portion of the image light in the hologram at multiple locations along the optical path of the collimated beam portion such that the collimated beam portion reflected by the hologram is wider than the collimated beam portion impinging on the hologram.

[0082] Reference now Figure 1A, the device 100 provides an image in the angular domain. The image can be defined by a light field having a two-dimensional (2D) angular distribution of brightness I(α, β). The angles α, β are the ray angles of the image light that define the ray angles in 3D space, such as Figure 1A More generally, the device 100 can be used to redirect light in two dimensions or along two non-parallel planes or surfaces, such as for 2D beam rastering, remote sensing, depth sensing, LIDAR applications, etc. In this document, the term "redirection" includes rastering of a collimated beam, as well as providing an instantaneous distribution of light in one or two dimensions or planes.

[0083] The device 100 includes a light source 102, a 1D redirector 104 coupled to the light source 102, and a low-mode waveguide 106 coupled to the 1D redirector 104 through a coupler 103. The low-mode waveguide 106 includes a slab waveguide portion 107. As used herein, the term "slab waveguide" means a waveguide that restricts light propagation in only one dimension (i.e., the vertical direction or Z direction perpendicular to the plane of the waveguide) while allowing light to propagate freely within the plane of the waveguide (e.g., in the Z direction). Figure 1A The light source 102 provides light 108 having a tunable spectrum, which varies according to the desired brightness distribution I(α, β). For example, the tunable optical spectrum can have multiple spectral components; in some embodiments, one spectral component can be provided at a tunable wavelength.

[0084] The 1D redirector 104 receives light 108 from the light source 102 and redirects the light 108 in the XY plane (i.e., the plane of the low-mode waveguide 106) according to a desired brightness distribution I(α, β), for example, angularly dispersing the light 108. In display applications, the 1D redirector 104 is used as a 1D imager that provides a 2D image line. The slab waveguide portion 107 is a single-mode waveguide or a few-mode waveguide that is configured to propagate the light 108 in the XY plane, but to restrict and guide the light to propagate along the Z axis. The slab waveguide portion 107 includes an external coupler 110 that couples the image light 108 outward at an angle to the plane of the low-mode waveguide 106 (XY plane), the angle depending on the wavelength of the spectral components of the light 108. In some embodiments, a single tunable spectral component can be coupled outwardly by an outcoupler 110 in a plane arranged at an angle to the plane of the low-mode waveguide 106 (i.e., the XY plane) at an angle that depends on its wavelength; and in some embodiments, multiple spectral components are coupled outwardly simultaneously or instantaneously at an angular distribution corresponding to the wavelength distribution of the spectral components. The distribution of the out-coupling angles is defined by the tunable optical spectrum of the light 108. The angular distribution of the brightness in the X-direction and the Y-direction can be controlled to provide an image with a desired brightness distribution I(α, β) in the angular domain for direct observation by a viewer.

[0085] Figure 1B An embodiment of a low-mode waveguide 106 is shown in a side cross-sectional view. The low-mode waveguide 106 includes a substrate 112 supporting a thin waveguide layer 114 in which light 108 propagates. Depending on the refractive index contrast and thickness of the waveguide layer 114, only one mode or multiple modes (e.g., up to 10 modes) can propagate in the thin waveguide layer 114. Therefore, the term "low-mode" waveguide is defined herein to refer to a waveguide that supports up to 10 different lateral propagation modes. The light 108 propagates in the plane of the waveguide 106 (i.e., the XY plane), but is constrained or guided in the Z direction.

[0086] The wavelength selective outcoupler 110 couples the image light 108 out at different angles depending on the wavelength. For example, a first spectral 121 component at wavelength λ1 is coupled out at a right angle to the low mode waveguide 106, and a second spectral component 122 at wavelength λ2 is coupled out at an acute angle to the low mode waveguide 106. The spectral composition of the light 108 provided by the light source 102 and the angular dispersion of the wavelength selective outcoupler 110 are selected so as to provide a desired angular distribution of brightness I(α, β(λ)). By way of non-limiting example, reference is made to Figure 1C , the entire image 116 can be formed in the angle domain. The image 116 is represented by the brightness angular distribution I(α, β(λ)).

[0087] refer to Figure 2 , device 200 is Figure 1A and Figure 1B An example implementation of the device 100 in FIG. Figure 2 The display device 200 in the embodiment includes: a spectrally tunable single-mode light source 202, an inner coupler 203, a 1D imager 204, the following optional modules: a 1D FOV expander 224, a 1D lateral beam expander 226 and an angular dispersion enhancer 228; and an outer coupler 210, which are optically coupled in series. Other elements may also include a zoom adjuster 230, a stray light filter 232 and a distributed temperature sensor 234. The optional elements are shown as dashed rounded rectangles. All or some of the elements may be part of the low-mode waveguide 206, for example, may be formed in the low-mode waveguide 206 or on the low-mode waveguide 206. It should be noted that the low-mode waveguide 206 may include a portion having a linear waveguide (i.e., a straight or curved ridge waveguide that guides light in two dimensions) and a slab waveguide portion that guides light in only one dimension, i.e., in Figure 2 The 3D prism guides light in the Z direction while allowing light to propagate freely in the XY plane. Figure 2 The coupling order of the elements shown in FIG. 1 may be varied.

[0088] In operation, the spectrally tunable single-mode light source 202 provides image light 208 having a tunable spectrum, which varies according to the desired angular distribution of brightness I(α, β(λ)), as described above. The coupler 203 couples the image light 208 into the 1D imager 204. The 1D imager 204 receives the image light 208 from the light source 202 and redirects or angularly disperses the image light 208, scans a collimated beam of the image light 208, etc. The 1D FOV expander 224 can be configured to switch the image light 208 between multiple adjacent FOV portions to enhance or widen the spread of the light. The 1D lateral beam expander 226 increases the width of the collimated portion of the image light in the XY plane, that is, widens the beam of the image light 208 in the plane of the low-mode waveguide 206, thereby increasing the lateral size of the viewing window of the display device 200. In this document, the term "viewing window" refers to a geometric area in which a user of the display device 200 can observe an image of acceptable quality. Angular dispersion enhancer 228 increases the spectral dispersion of image light 208 to achieve a desired second brightness ID angular distribution I(β) when coupled outwardly by wavelength selective outcoupler 210. Zoom adjuster 230 can adjust the convergence or divergence of the outcoupled image light to change the perceived depth of focus. Stray light filter 232 can remove or reduce the portion of image light that is not coupled outwardly to the user's eyes but is coupled outwardly to the outside world. Distributed temperature sensor 234 can obtain the temperature distribution on low mode waveguide 206 to provide correction and operate thermally driven optical elements and components. More details will be given below.

[0089] refer to Figure 3 , the display device 300 is the device 100 in FIG. 1 or Figure 2 Implementation method of device 200 in. Figure 3 The display device 300 in FIG. 3 is a near-eye display device having the form factor of a pair of glasses 311 , wherein the low-mode waveguide 306 occupies the lens area of ​​the glasses. Figure 3 The display device 300 in FIG. 1 includes: a light source 302, a coupler 303, a 1D imager 304, a 1D FOV expander 324, a 1D lateral beam expander 326, an angular dispersion enhancer 328, an outer coupler 310, and a zoom adjuster 330 optically coupled in series. All elements can be implemented in a low-mode waveguide 306. As shown in the figure, the light source 302 can be set separately.

[0090] refer to Figure 4A , the display device 400 is the device 100 in FIG. 1 , Figure 2 Device 200 or Figure 3 Implementation method of the display device 300 in FIG. Figure 4AThe display device 400 in is a near-eye display device having the form factor of a pair of glasses 411, wherein active components / features are implemented in a PIC portion 436 of a waveguide 406. The PIC portion 436 can be driven by an integrated circuit (IC) driver unit 407. The display device 400 includes a light source 402 having a tunable emission spectrum, which is coupled to the PIC portion 436 via an optical fiber 403. The PIC portion 436 can include, for example, a 1D imager and / or a 1D FOV expander. The light beams 408A, 408B, and 408C (collectively referred to as 408) formed in the PIC portion 436 are expanded by waveguide intra-optical elements 426A, 426B, and 426C, respectively, which have optical power (i.e., focusing / defocusing power) for collimating / redirecting the light beams 408A, 408B, and 408C to a high dispersion output grating 410. The function of the high dispersion output grating 410 is to provide image light 408 to be coupled out at different vertical angles to provide a vertical FOV, such as Figure 4B shown. Figure 4C The horizontal FOV shown in FIG. 4 is provided by the portion of the PIC that diffuses the image light 408 within the plane of the waveguide 406 .

[0091] Now we will consider Figure 1. Figure 2 , Figure 3 and Figure 4A Multiple implementations of the different modules depicted in .

[0092] First reference Figure 5 , the tunable laser source 502 can be used as a wavelength tunable light source for the display device of the present disclosure. The tunable laser source 502 includes an optical cavity formed by a pair of reflectors 501, a gain medium 504, and a wavelength selective intracavity element 506, the wavelength selective intracavity element 506 having a transmission peak tunable within the gain spectrum band of the gain medium 504. The transmission peak of the wavelength selective element 506 can be scanned in coordination with the 1D angle of the scanned collimated light beam 508 to provide the 2D FOV required by the display device, such as the horizontal FOV provided by the beam scanning and the vertical FOV provided by the output wavelength scanning of the tunable laser source 502.

[0093] Go to Fig. 6A , a tunable spectrum light source 602 can be used as a wavelength tunable light source for a display device of the present disclosure. The tunable spectrum light source 602 includes a broadband source 604 of light 608 coupled to a dynamic spectrum filter 606 having a selectable arbitrary spectral shape. The emission spectrum 630 of the broadband source 604 is Figure 6B , where it overlaps with an example broadband spectral shape 632 of the dynamic spectral filter 606 or an example narrowband (single wavelength) spectral shape 633 of the dynamic spectral filter 606 .

[0094] Dynamic spectral filter 606 can be configured to independently adjust the transmission of single or multiple adjacent narrow spectral bands or channels. For example, dynamic spectral filter 606 can adjust the shape of broadband spectral shape 632 according to the desired angular distribution of brightness at the output of the display device. In some embodiments, narrowband spectral shape 633 can be scanned at a wavelength that causes the output beam to be scanned angularly according to the dispersion function of the outer coupler of the display device.

[0095] exist Figure 6C The resulting output spectra are shown in . For example, the broadband spectral shape 632 results in a broadband emission spectrum 634 , while the narrowband spectral shape 633 correspondingly results in a narrowband emission spectrum 635 , the emission wavelength of which can be tuned by the dynamic spectral filter 606 .

[0096] refer to Figure 7 The free-space grating coupler 703 can be used to couple light from a tunable spectral light source 702 (e.g. Figure 5 Tunable laser source 502 or Fig. 6A The free-space grating coupler 703 includes a plurality of grating lines 705 in a core 707 that receive image light 708 and couple the image light 708 into a waveguide 706. The grating lines 705 extend parallel to each other and may be straight or curved, for example, having a direction perpendicular to the image light. Figure 7 The concentric arc shape provides focusing of the image light 708 so that its mode size matches the size of the optical mode 709 that can propagate in the core 707 of the waveguide 706.

[0097] Go to Figure 8 , the waveguide coupler 803 can be used to couple light from a spectrally tunable, waveguide-based or fiber-coupled light source into a waveguide or PIC of a display of the present disclosure. The waveguide coupler 803 includes a tapered portion 836 in which the tapered core 813 of the source fiber 802 is disposed adjacent to and parallel to the tapered waveguide core 805 of a waveguide 806 having a waveguide core 807. The tapered portion 836 can be long enough to ensure that light can adiabatically transition from the source fiber 802 into the waveguide core 807 of the waveguide 806.

[0098] refer to Fig. 9 , the phased array 1D imager 904 is the 1D redirector / imager 104 in FIG. 1 , Figure 2 1D imager 204, or Figure 3 An embodiment of the 1D imager 304 in. Fig. 9The phased array 1D imager 904 in the embodiment includes a 1×N power splitter 920, N phase shifters 922 coupled to the power splitter 920, and an array of N linear waveguide transmitters 924 coupled to the phase shifters 922. In this specification, the term "linear waveguide" refers to a waveguide that restricts light propagation in two dimensions, such as a light wire. A linear waveguide can be straight, curved, etc.; in other words, the term "linear" does not mean a straight waveguide section. An example of a linear waveguide is a ridge waveguide. All elements of the phased array 1D imager 904 can be implemented in a low mode waveguide 906 including a slab waveguide section 907. The number N can vary, for example, between 4 and 16,000.

[0099] In operation, the internal coupler (e.g., free-space grating coupler 703) is Fig. 9 A wavelength tunable laser source not shown in the figure receives the image light 908 and couples the image light 908 into a power splitter 920. The power splitter 920 distributes the image light 908 among the N linear waveguides 921 of the low mode waveguide 906, each of which transmits a portion of the image light 908. Based on a control signal provided by a controller 926, each image light portion is phase shifted or delayed by a corresponding phase shifter 922. The image light portion is transmitted to the desired beam angle corresponding to the desired beam angle by an array of N linear waveguide transmitters 924. The phase profile of 922 forms an output beam 919 having a phase front 921 to emit the image light portion. The output beam 919 propagates in the slab waveguide portion 907. In some embodiments, the phase profile in 922 can be controlled to suppress all diffraction orders except one diffraction order so that all energy is concentrated into a single controllable beam.

[0100] Go to Fig. 10A , PIC phased array 1D imager 1004 is Fig. 9 10. The PIC phased array 1D imager 1004 in FIG. 10 includes a Mach-Zehnder interferometer array (MZIA) 1020 operating as a beam splitter 920, a PIC phase shifter array (PSA) 1022 coupled to the MZIA 1020, and a waveguide concentrator 1024 coupled to the PIC phase shifter array 1022. The end of the output linear waveguide 1030 of the waveguide concentrator 1024 serves as an antenna 924 ( Fig. 9 ) operation, launching on the plane of the slab waveguide section ( Fig. 10A The light propagates freely in the XY plane in the slab waveguide and at the same time in the direction perpendicular to the slab waveguide ( Fig. 10A The constraints are maintained in the Z direction.

[0101] The MZIA 1020 may include a binary tree of passive Y-splitters and / or active Mach-Zehnder interferometers (MZIs) 1021, such as Fig. 10B Each MZI may include Fig. 10C The evanescent coupler 1026 shown has one input 1023 and two outputs 1033, 1034, or two inputs (one of which is idle) and two outputs, i.e., two waveguide sections coupled by the evanescent coupler at two locations. The function of the MZIA 1020 is to split the image light into N parts. In an embodiment using a passive Y-splitter, the PSA 1022 can be used to scan the collimated beam. In an implementation in which an active MZI is used, the two branches of the MZI ( Fig. 10C ) in at least one branch to control the optical power distribution at the output end to unequal optical power, for example to provide apodization of the scanned collimated light beam, or even to create a fully desired 1D angular distribution.

[0102] refer to Fig. 10D , the phase shifter array 1022 may include a plurality of phase shifters 1027 that provide a controllable amount of phase shift or delay for light propagating therein. The phase shifters 1027 may be, for example, thermo-optic phase shifters based on thermo-optic effect, electro-optic phase shifters based on Pockels effect and / or Kerr effect, and / or electro-absorption phase shifters based on electro-absorption effect in semiconductors, and thus may include heaters and / or electrodes on the waveguide as needed.

[0103] Go to Fig.10E , the waveguide concentrator 1024 includes a waveguide array that fans in or out to achieve the desired output pitch. Generally, the output pitch needs to be small enough to achieve a large FOV. The FOV is approximately equal to the ratio of the emission wavelength of the output linear waveguide 1030 to the pitch.

[0104] refer to Fig.11 , the hybrid 1D imager 1104 is the 1D redirector 104 in FIG. 1 , Figure 2 1D imager 204 or Figure 3 An example implementation of the 1D imager 304 in FIG. Fig.11The hybrid 1D imager 1104 in FIG. 1 includes an MZIA 1120, a waveguide concentrator 1124 coupled to the MZIA 1120, and a FOV collimator 1136 coupled to the waveguide concentrator 1124, which are implemented in the low-mode waveguide 1106. The MZIA 1120 acts as a 1×N splitter or switch, where N is the number of output MZIA waveguides 1129. The MZIA 1120 may include, for example, a binary tree of Mach-Zehnder switches for switching image light 1108 between the N linear output waveguides. The waveguide concentrator 1124 has its output linear waveguides 1130 closer together than the output MZIA waveguides 1129. The ends of the output linear waveguides 1130 of the waveguide concentrator 1124 are disposed at the focal plane of the FOV collimator 1136 located in the slab waveguide portion 1107 of the few-mode waveguide 1106. The FOV collimator 1136 is a collimating element disposed at a focal length from the end of the output linear waveguide 1130 of the waveguide concentrator 1124. The function of the FOV collimator 1136 is to convert the positioning or Y offset of the end of the output linear waveguide 1130 of the waveguide concentrator 1124 into a beam angle of a corresponding output light beam 1119 propagating in the slab waveguide portion 1107. In other words, the FOV collimator 1136 operates as an offset-to-angle optical element that converts the offset or Y positioning of a selected one of the output waveguides 1130 conveying a portion of the image light 1108 into an angle of the output light beam 1119 originating from the image light portion propagating in the selected output waveguide.

[0105] The FOV collimator 1136 may be a single element such as a lens or a mirror, or may include multiple lenses 1138, 1140, such as Fig.11 As shown. Lenses 1138, 1140 may be formed in the low mode waveguide 1106 by etching and, for example, may have an s-folded configuration such as a pancake lens configuration. The output beam 1119 may be shaped, focused, collimated, etc. in the plane of the waveguide (XY plane) while remaining guided by the slab waveguide portion 1107, i.e., remaining constrained in the Z direction. The lens surface may include a plurality of tapers 1141 with sub-wavelength periodicity to facilitate an adiabatic transition between the etched and non-etched portions of the waveguide and thereby prevent out-of-plane light scattering.

[0106] refer to Fig.12, a free space optical (FSO) 1D scanner 1204 includes a microelectromechanical system (MEMS) beam scanner 1244 having a tiltable reflector 1245 and a cylindrical lens 1246. In operation, a multi-wavelength light source such as a wavelength-swept laser source 1202 emits a light beam 1208 with a tunable (e.g., linear scan) wavelength. The light beam 1208 is focused onto the MEMS tiltable reflector 1245 by the cylindrical lens 1203. The cylindrical lens 1246 serves as a coupler that receives the image light 1208 scanned by the MEMS beam scanner 1244 and couples the image light 1208 to the low-mode slab waveguide 1207. The cylindrical lens 1203 can be, for example, refractive or diffractive. For example, other types of couplers such as mirrors can be used. The MEMS tiltable reflector 1245 reflects the light beam 1208 at a variable angle, as indicated by the double-headed arrow. The cylindrical lens 1246 has focusing capability in the XZ plane while propagating the light beam 1208 substantially unfocused in the XY plane. The cylindrical lens 1246 focuses the light beam 1208 onto the edge of the low-mode slab waveguide 1207 or onto a grating coupler formed in the low-mode slab waveguide 1207. The light beam 1208 is coupled into the low-mode slab waveguide 1207 and propagates freely in the low-mode slab waveguide 1207 in the XY plane, being confined in the Z direction perpendicular to the plane of the low-mode slab waveguide 1207. The cylindrical lens 1246 needs to be precisely parallel to the low-mode slab waveguide 1207 for effective coupling.

[0107] Go to Fig.13A and Fig. 13B , Liquid Crystal (LC) 1D FOV Expander 1324 is Figure 2 1D FOV extender 224 and Figure 3 An embodiment of the 1D FOV expander 324 in. Fig.13A and Fig. 13B The LC 1D FOV expander 1324 in FIG. 1 includes a slab waveguide 1306 having a core 1307 for guiding image light 1308 in the core 1307 while allowing the image light 1308 to propagate freely in the XY plane as shown. The top cladding 1337 includes tunable cladding portions 1339, 1340 that are transiently coupled to the core 1307 of the slab waveguide 1306 and are shaped to deviate light propagating in the core 1307 of the slab waveguide 1306 by a controllable amount. Fig.13A In the illustrated embodiment, the tunable cladding portions 1339, 1340 have a sawtooth shape in the XY plane, for example a triangular array, such as Fig.13A The array extends transversely relative to the optical path of the image light in the core 1307 of the slab waveguide 1306. At least some of the triangular tunable cladding portions have a shape relative to that shown in FIG. Fig.13A A bottom layer 1338 ( Fig. 13B ) to avoid direct contact between the tunable cladding portions 1339, 1340 and the waveguide core 1307. The bottom layer 1338 may be thin enough to ensure evanescent coupling of light propagating in the core 1307 with the tunable cladding portions 1339, 1340.

[0108] The tunable cladding portions 1339, 1340 of the top cladding 1337 include a liquid crystal (LC) LC material that changes its refractive index for a specific polarized light when an electric field is applied to the tunable cladding portions 1339, 1340. When the refractive index of the LC tunable cladding portions 1339, 1340 of the top cladding 1337 changes, the effective refractive index of the slab waveguide 1306 also changes, so that the image light 1308 deviates from the original propagation direction due to Fresnel refraction on the inclined surfaces of the LC tunable cladding portions 1339, 1340. The magnitude of the deviation depends on the angle and vertical pitch (vertical pitch in the Y direction) of the inclined surfaces of the LC tunable cladding portions 1339 and 1340. The energy distribution in directions 1349 and 1350 depends on the switching state of the LC tunable cladding portions 1339 and 1340, which can be operated in a binary mode (on / off). When the LC tunable cladding portions 1339 and 1340 are not continuously tunable, each array of LC tunable cladding portions 1339 and 1340 may shift the 1DFOV by a discrete amount. Thus, the cascaded m LC elements will produce 2 m By energizing different triangular LC tunable cladding portions 1339, 1340, the image light 1308 can be deflected at different angles. For example, energizing the larger triangular shape 1339 deflects the image light 1308 to propagate at an angle, as shown at 1349, and energizing the shallower triangular shape 1340 deflects the image light 1308 to propagate at a steeper angle, as shown at 1350. More arrays of LC portions with different deviation angles can achieve more precise angular control. When different triangular shapes of the LC tunable cladding portions 1339, 1340 are energized in coordination with operating a 1D imager or scanner, the image light is switched between multiple adjacent FOV portions, enabling effective controllable light diffusion and the associated horizontal FOV can be extended or enhanced.

[0109] refer to Fig.14, a holographic beam expander 1426 includes a hologram 1456 in a low-mode slab waveguide 1406 that enables image light to propagate in two dimensions (i.e., in the XY plane) in the plane of the slab waveguide 1406. The hologram 1456 is configured to receive image light 1408, which includes at least one collimated beam portion, such as a first (1451; dotted line) collimated beam portion and a second (1452; dashed line) collimated beam portion that propagate at an angle to each other, and reflect each collimated beam portion at a plurality of locations along the optical path of the collimated beam portion in the hologram 1456. For example, the first collimated beam portion 1451 is reflected at a first angle at multiple locations 1451A, 1451B, 1451C to produce a first output beam (1461; dotted line); and the second collimated beam portion 1452 is reflected at a second angle at multiple locations 1452A, 1452B, 1452C to produce a second output beam (1462; dashed line). Any other light beam is reflected at a beam angle between the first angle and the second angle, propagating in multiple directions between the directions of the first output beam 1461 and the second output beam 1462. To this end, the hologram 1456 may include multiple stripes that are configured to ensure reflection in a desired direction based on the angle of the impinging beam. Fig.14 It can be seen that such a reflection geometry results in the expansion of light beams 1451 , 1452 .

[0110] Go to Fig.15 , the wide beam PIC phased array 1D imager 1504 is similar to Fig. 10A PIC phased array 1D imager 1004 in the MZIA 1520 and PSA 1522 ( Fig.15 ) include more linear waveguides. The output waveguide array coupler or beam expander 1524 is similar to the concentrator 1024, but includes more output linear waveguides 1530, such as 10,000; 20,000; 30,000 or more waveguides spanning a lateral distance of more than 5 mm; 10 mm; or 15 mm, as appropriate. The output beam can be as wide as the width of the linear waveguide 1530 array, and therefore, any subsequent beam expansion and collimation may not be required in order to expand the output beam over the viewing window of the near-eye display, thereby simplifying the overall design.

[0111] Reference now Fig.16 , the slab waveguide 1606 supports a diffraction grating 1661 for diffracting a portion of the image light 1608 propagating in the XY plane of the slab waveguide 1606. The K vector of the diffraction grating 1661 is aligned with the x component of the K vector of the image light 1608. The diffraction angle θ of the image light 1608 follows the equation:

[0112]

[0113] where n is the refractive index, T is the grating period, and λ is the wavelength of the light in the propagation medium. Therefore,

[0114]

[0115] Among them, n gr is the group velocity refractive index. In a regular waveguide with small dispersion, n gr =n; therefore,

[0116]

[0117] From equation (3), we can see that at normal incidence and T = λ / n

[0118]

[0119] For n=2, the wavelength range is from 510 nm to 530 nm. According to the present disclosure, the angular range can be increased to some extent by increasing the diffraction angle θ. For example, by reducing the grating pitch to 180 nm, a range of diffraction angles dθ to 14.4 degrees can be achieved.

[0120] The angular dispersion range can be increased, for example, by using multilayer output waveguides. Fig.17 , the dual-core slab waveguide 1706 extends in the XY plane. The dual-core slab waveguide 1706 includes a first core 1707 and a second core 1757 extending parallel to each other in the XY plane of the substrate 1736 surrounded by a first cladding 1705 and a second cladding 1755, respectively. The first core 1707 and the first cladding 1705 are configured for single-mode propagation of a first beam of image light (solid arrow; 1708). Similarly, the second core 1757 and the second cladding 1755 are configured for single-mode propagation of a second beam of image light (dashed arrow; 1758).

[0121] The first core 1707 and the second core 1757 have a first diffraction grating 1710 and a second diffraction grating 1760 formed in or on the first core 1707 and the second core 1757, respectively. The first diffraction grating 1710 is configured to couple outwardly a spectral component of the redirected image light at a first angle depending on the first wavelength. The first angle is within a first angular range corresponding to the tuning range of the wavelength tunable light source used. Similarly, the second diffraction grating 1760 is configured to couple outwardly a spectral component of the redirected image light at a second angle different from the first angle. The second angle is within a second angular range corresponding to the tuning range of the wavelength tunable light source.

[0122] For the same wavelength of image light represented by the first beam 1708 and the second beam 1758, different angles and angular ranges of diffraction from different cores 1707, 1757 of the dual-core waveguide 1706 can be achieved by changing the thickness or refractive index of the cores 1707 and 1757, the refractive index of the claddings 1705 and 1755, or the pitch of the diffraction gratings 1710 and 1760. To simplify manufacturing, a single grating can be etched into the first core 1707 layer, and the second core 1757 layer or any subsequent layers can simply reproduce the grating by directional material deposition. In the latter case, the FOV can be adjusted by changing the thickness of the layer and thus changing the effective refractive index.

[0123] By tilting the angular range relative to the stratification to a smaller extent, different diffraction angles can be used to extend the corresponding "vertical" 1D FOV. In this article, the term "vertical" means to distinguish from the 1D FOV by redirecting the image light in the plane of the low-mode waveguide (i.e., the XY plane referred to as the "horizontal"). It should be noted that in this context, the terms "horizontal" and "vertical" are meant only as differentiators to distinguish the in-plane 1D FOV from the wavelength dispersion 1D FOV, and do not mean the actual orientation of the device when in use. Switching between the first core 1707 and the second core 1757 can be achieved, for example, using a Mach-Zehnder interferometer and a directional coupler. More details on possible switching configurations will be provided further below.

[0124] Go to Fig.18 , the angular dispersion module 1828 provides enhanced wavelength dispersion of the image light to obtain the desired vertical 1DFOV. The angular dispersion module 1828 includes a series coupled: an MZIA 1820, which is coupled to a vertical mode converter 1821, such as an asymmetric directional coupler; a multimode interference (MMI) coupler 1851 that receives light from the vertical mode converter 1821; and a few-mode slab waveguide section 1856 that receives light from the MMI coupler 1851. The number of transverse propagation modes of the image light that can propagate in the core of the few-mode slab waveguide section 1856 can be, for example, 2, 3, 4, 5, or 6, or more generally not more than 10 modes. A diffraction grating 1807 disposed in or on the core of the few-mode slab waveguide section 1856 operates as an outcoupler that outcouples the image light at an angle that depends on the wavelength. The diffraction grating 1807 is configured to outcouple each spectral component of the redirected image light at an angle that depends on the wavelength of the spectral component. The outcoupling angle is within the outcoupling angle range corresponding to the tuning range of the wavelength tunable light source used. The outcoupling angle range is different for different lateral propagation modes of the few-mode slab waveguide portion 1856 because each propagation mode has a different effective refractive index.

[0125] Initially, only the fundamental mode of the image light is coupled into the MZIA 1820 via the inner coupler 1803. The MZIA 1820 acts as a 1×N optical switch, switching the image light between its output waveguides. At the end of each of the MZIA 1820 output waveguides, the image light is converted into a different vertical mode by a vertical mode converter 1821. Using an MMI coupler 1851, the image light from all waveguides is combined into the few-mode slab waveguide section 1856. In this way, the in-plane image encoder layout (i.e., the one described above with reference to FIG. 1 ) is Figure 9-Figure 15 The disclosed horizontal 1D imager circuit) can be shared between different propagation modes of the image light in FMW 1856.

[0126] Different vertical modes have different effective refractive indices and, therefore, will be diffracted at different angles at the diffraction grating 1807 for the same wavelength. The overall vertical 1D FOV can be extended using diffraction range extension using separate modes in a time sequential manner, i.e., switching to a particular core providing a corresponding portion of the vertical 1D FOV, then switching to another core providing a different portion of the vertical 1D FOV, and so on, until all vertical 1D FOVs are covered. The MMI coupler 1851 can be optimized for the desired coupling of the vertical modes using physical design software by defining an optimization function (also called a merit function) to have an operand representing the optical insertion loss of the MMI coupler for each vertical mode with predefined vertical coordinates, and having the physical design software run the optimization.

[0127] Fig.18 A coupling configuration, i.e., MZIA 1820 coupled to vertical mode converter 1821 coupled to MMI 1851, can be used to couple image light received by inner coupler 1803 into a different vertical mode of any waveguide assembly that supports several vertical modes. For example, such a configuration can be used to couple image light into Fig.17 In the core of the dual-core slab waveguide 1706. In the case of the dual-core slab waveguide 1706, only one Mach-Zehnder interferometer can be used to replace the MZIA 1820 to operate as a 1×2 optical switch. The multi-core slab waveguide may include multiple cores, and Fig.18 The coupling configuration can be used to couple image light into any core of a multi-core slab waveguide.

[0128] refer to Fig.19, the angular dispersion enhancer 1928 is based on a slow light slab waveguide 1906 that extends in the XY plane and supports a cladding 1905 with a diffraction grating structure 1910 for coupling image light out of the slow light waveguide 1906. The slow light waveguide 1906 may include a uniform 2D photonic crystal, a multilayer structure, or a combination of both, for increasing the group velocity refractive index by a factor of 20, for example, or at least by a factor of 10. Then, from equations (2)-(4), it can be seen that the FOV can be increased by a factor of ten, for example, from 4.4 degrees to 44 degrees, when the slowing factor is 20. In some embodiments, the slow light waveguide 1906 may include an array of linear photonic crystal waveguides.

[0129] refer to Fig. 20A , the angular dispersion enhancer 2028A includes a low mode waveguide 2006 having a slab waveguide portion 2056 disposed in the XY plane and a corrugated reflector 2070A supported by the slab waveguide portion 2056. Image light 2008 conveying image information encoded in its spectrum propagates in the slab waveguide portion 2056. A diffraction grating 2010, such as a Bragg grating, in the slab waveguide portion 2056 couples out different spectral components of the image light 2008 at different angles exceeding 90 degrees relative to the propagation direction of the image light 2008 in the slab waveguide portion 2056. For example, a first spectral component 2081 is coupled out at a first angle θ1, and a second spectral component 2081 is coupled out at a second, larger angle θ2. The corrugated reflector 2070A reflects the first spectral component 2081 and the second spectral component 2082 of the image light 2008 diffracted by the diffraction grating 2010 through the slab waveguide portion 2056 and outside the low mode waveguide 2056.

[0130] The angular dispersion of the outcoupled image light 2008 is greatest when the image light 2008 is coupled out almost directly backwards (i.e., the angle θ is close to 180 degrees). For example, assuming a regular waveguide grating with a refractive index of 2, changing the wavelength from 510nm to 530nm results in a 4.4° shift when the average diffraction angle θ is 0, and a 14° shift if the average diffraction angle θ is approximately 65°. In this configuration, the diffraction grating 2010 couples the image light 2008 out backwards to maximize the angular dispersion and thus increase the FOV of the display. The corrugated reflector 2070A may include a plurality of prisms 2072 having a reflective coating 2074 supported by the slab waveguide portion 2056 that redirect the image light 2008 in a direction perpendicular to the slab waveguide portion 2056 to ensure that the central field angle is perpendicular to the slab waveguide portion 2056, i.e., parallel to the Z axis. As non-limiting examples, the reflective layer 2074 can be made of any one or a combination of the following: (1) a low refractive index material for total internal reflection (TIR), (2) a thin metal layer forming a semi-reflective mirror, or (3) a narrow spectrum multilayer mirror coating or a reflective polarizer such as a wire grid polarizer or a dual brightness enhancement film (DBEF).

[0131] Go to Fig. 20B , the angular dispersion enhancer 2028B is Fig. 20A A polarization selective embodiment of the angular dispersion enhancer 2028A in FIG. Fig. 20B In the angular dispersion enhancer 2028B in the embodiment, the corrugated reflector includes a polarization selective reflector 2070B, which is configured to reflect light with a first polarization and transmit light with a second polarization orthogonal to the first polarization. The angular dispersion enhancer 2028B also includes a quarter wave plate (QWP) 2076 supported by the slab waveguide portion 2056 on the opposite side of the slab waveguide portion 2056 and the polarization selective reflector 2070B. The QWP 2076 is configured to receive image light components 2081, 2082 reflected by the polarization selective reflector 2070B. The image light components 2081, 2082 are in a first polarization state.

[0132] A diffractive structure 2078 (e.g., a reflective surface relief diffraction grating) is supported by the QWP 2076 and is configured to reflect image light components 2081, 2082 propagating through the QWP 2076 back to propagate through the QWP 2076 a second time, thereby converting the polarization of the image light components 2081, 2082 from a first polarization to a second polarization. The components 2081, 2082 then propagate through the slab waveguide portion 2056 and through the polarization selective reflector 2070B, which transmits the components 2081, 2082 through because they are in the second polarization state. The purpose of the diffractive structure 2078 is to further increase the angular dispersion of the image light 2008.

[0133] refer to Fig.21A and Fig. 21B , showing the principle of zoom adjustment (ie, adjusting convergence / divergence) of outcoupled image light. Fig.21A The low-mode slab waveguide portion 2156A in FIG. 21 includes a grating outcoupler with a uniform refractive index. The image light component 2108 is outcoupled vertically, ie, perpendicular to the plane of the slab waveguide portion 2156A, as a parallel beam focused at infinity. Fig. 21B The slab waveguide portion 2156B in the embodiment includes a grating outcoupler with a controllable non-uniform refractive index so that the image light component 2108 is coupled out vertically, i.e., perpendicular to the plane of the slab waveguide portion 2156B, to converge as shown in the figure as a focused beam with a focal length equal to the inverse of the optical power (focusing power) of the grating outcoupler. Assuming that the desired size of the window 2112 is 16 mm, a refractive delta of 0.008 is required to focus the image light component 2108 from the slab waveguide portion 2156B to a focal spot 2185 two meters outside the window 2112. In order to achieve this focusing function, the effective refractive index n of the grating outcoupler is 0.008 when passing through the window 2112. eff A linear change from 0.004 to -0.004 is required. This principle can be used in any dispersion enhancer considered in this paper. For a dispersion enhancer with a resonant structure, any change in the physical refractive index of the material in the stack will produce n eff The greater change in refractive index along the outer coupler promotes focusing or defocusing. Figure 22 to Figure 25 Consider the example of a zoom adjuster based on this principle.

[0134] First reference Fig. 22, the zoom adjuster 2230 includes a low-mode slab waveguide portion 2256 for propagating light (e.g., image light 2208). The slab waveguide portion 2256 includes an outcoupler 2210, such as a Bragg grating, which is configured to outcouple the image light 2208 at a certain angle to the XY plane of the slab waveguide portion 2256. A liquid crystal (LC) cell 2288 is transiently coupled to the slab waveguide portion 2256. The thickness of the upper cladding 2287 of the slab waveguide portion 2256 is selected so that the tail of the guided mode 2290 of the image light 2208 traveling in the core of the mode slab waveguide portion 2256 overlaps with the LC cell 2288, reaches the LC layer 2289 of the LC cell 2288 through the upper cladding 2287 supporting the LC cell 2288. The LC layer 2289 is disposed between a pair of electrodes 2283. The guided mode 2290 overlaps with the LC layer 2289 of the LC cell 2288 .

[0135] The LC cell 2288 defines the effective refractive index of the guided mode 2290 of the image light 2208 propagating in the slab waveguide portion 2256. The effective refractive index n eff In the direction in which the image light 2208 propagates in the low-mode slab waveguide 2256 (i.e. Fig. 22 The effective refractive index n eff The direction of the outcoupled image light 2208 portion changes along the X-axis, which causes the outcoupled image light 2208 to be focused or defocused, as described above with reference to Fig.21A and Fig. 21B The upper cladding layer 2287 ( Fig. 22 ) can be selected such that a change in the refractive index of the LC layer 2289 will result in an effective refractive index n for the propagating waveguide mode 2290. eff This will cause the outcoupled image light 2208 to be focused or defocused. The absolute value of the change, and therefore the focal length, can be controlled by the voltage applied to the LC cell 2288. The thickness profile of the upper cladding layer 2287 can be linear, i.e. the LC cell 2288 can form an acute angle with the slab waveguide portion 2256, thereby changing the effective refractive index n for the waveguide mode 2290 eff .

[0136] The refractive index of LC layer 2289 is changed by applying a voltage to LC cell 2288. As described above, this causes the propagation direction of out-coupled image light 2208 to change along the propagation direction of image light 2208 in slab waveguide portion 2256 (i.e., the X direction), causing out-coupled image light 2208 to diverge or converge in the XZ plane. By varying the applied voltage, the divergence / convergence (collectively referred to as "divergence") of out-coupled image light 2208 can be controlled. In some embodiments, LC cell 2288 can be parallel to slab waveguide portion 2256 and can be pixelated to impart a refractive index variation profile along the propagation direction of image light 2208 (i.e., along the X direction).

[0137] Reference now Fig.23 , zoom adjuster 2330 includes a low-mode slab waveguide portion 2356 for propagating light (e.g., image light 2308). Slab waveguide portion 2356 includes a core layer 2307 and an outer coupler 2310, which is configured to couple image light 2308 outward at a certain angle to the plane of the slab waveguide portion. Core layer 2307 is made of a material having a refractive index that depends on the applied electric field. For example, core layer 2307 can be made of LiNbO3, AlN, SiC, or other materials with a high electro-optic coefficient.

[0138] Electrodes 2383 are disposed above and below the core layer 2307 for applying an electric field 2386 to the core layer 2307. The electrodes 2383 may be disposed at an acute angle to each other, forming a wedge shape. When a voltage is applied to the electrodes 2383, the electric field 2386 varies spatially along the direction of propagation of the image light 2308 in the core 2307 of the slab waveguide portion 2356 (i.e., along the X direction). This causes the direction of the image light 2308 coupled outward from the slab waveguide portion 2356 to vary along the direction of propagation of the light in the low-mode slab waveguide, effectively causing the outward coupled image light 2308 to diverge or converge in the XZ plane. By varying the applied voltage, the degree of convergence / divergence of the outward coupled image light 2308 may be varied in a controllable manner.

[0139] Spatial modulation of the refractive index can be achieved by passing a DC or AC electric field through the material of the slab waveguide portion 2356 and the propagating optical mode 2390. Depending on the crystal axis and the component design in which refractive modulation is desired, the electrodes can be placed above / below the upper / lower cladding, respectively, or in just one of these layers. In the case where the electrodes clamp the core of the waveguide, the electric field 2386 will extend vertically, as Fig.23As shown. The relative size of the electric field 2386 along the propagation of the image light 2308 (which is the image light that needs to be controlled in order to achieve focusing) can be distributed by changing the distance between the electrodes 2383. A larger distance will produce a weaker electric field 2386. By doing so, a predetermined wedge-shaped profile electric field 2386 that is proportional to the local refractive index change can be embedded. When the applied voltage V=0, the image light 2308 is collimated, that is, the image is at infinity. As the applied voltage V increases, the focal plane of the system gets closer and closer.

[0140] A similar principle applies to Fig.24 A zoom adjuster 2430 is shown in which an electric field 2486 is parallel to the core 2407 of the few-mode slab waveguide 2456. This orientation of the electric field 2486 is defined by a floating electrode 2482 extending along the propagation direction of the image light 2408 in the low-mode slab waveguide 2456, and the floating electrode 2482 is located between a pair of end electrodes 2485 to which a voltage V can be applied. The floating electrode 2482 is arranged to provide an amplitude distribution of the electric field 2486 that matches the refractive index distribution required to focus the outcoupled image light 2408. In some embodiments, a set of independently controlled electrodes can be provided to better control the amplitude distribution of the electric field 2486.

[0141] Reference now Fig.25 , the zoom adjuster 2530 includes a low-mode slab waveguide portion 2506 supporting a grating structure 2510, the grating structure 2510 including an array of grating fringes 2511 having a first refractive index and surrounded by a substrate 2512 having a second refractive index between each grating fringes 2511. The grating structure 2510 couples image light 2508 outwardly from the low-mode slab waveguide portion 2506. At least one of the first refractive index or the second refractive index may be tuned to provide a gradient of at least one of the first refractive index or the second refractive index for focusing or defocusing the image light 2508 coupled outwardly from the slab waveguide portion through an outcoupler. To this end, an array of heating elements 2570 may be coupled to the waveguide 2506 for providing non-uniform, spatially selective heating to the grating structure 2510. The spatially selective heating produces a refractive index gradient that can modify the local diffraction angle of the image light 2508, thereby enabling focusing or defocusing of the image light 2508 coupled out of the waveguide 2506. As a non-limiting example, to achieve a focal length of 1 m at a window length of 16 mm, an effective refractive index of a maximum Δn = 0.008 is required. If a slow light waveguide is used instead of the waveguide 2506, this number will be proportionally smaller. In some embodiments, the substrate 2512 can include a liquid crystal (LC) layer to provide the required refractive index gradient by tuning the LC layer with an applied electric field. Since the layer whose refractive index is modified is very thin, it will only affect the display optical path and not the see-through optical path.

[0142] refer to Fig.26 , and further reference Figure 1A , a method 2600 for providing an image in an angle domain ( Fig.26 ) includes using an inner coupler (eg, inner coupler 103) to couple image light (eg, image light) including a spectral component at a first wavelength Figure 1A The light 108 in the image is coupled 2602 to a 1D redirector / imager. The image light may be redirected using any horizontal FOV 1D redirector / imager disclosed herein, such as a 1D redirector / imager including FIG. 10A to FIG. 10E Any PIC embodiment of Fig. 9 Phased array 1D imager 904, Fig.11 A hybrid 1D imager 1104, or Fig.12 FSO1D scanner 1204. The 1D imager is in a first plane, e.g. Figure 1A 2604, the image light is redirected in the XY plane of the 1D imager, which is the plane of the low-mode slab waveguide portion 107. The image light 108 redirected by the 1D imager propagates 2606 in the low-mode slab waveguide portion 107. The spectral component at the first wavelength is coupled out 2608 from the low-mode slab waveguide by an outcoupler 110 (e.g., any grating outcoupler considered herein) at an angle that depends on the first wavelength. The low-mode slab waveguide portion may include a single-mode slab waveguide or a few-mode (no more than 10 modes) slab waveguide.

[0143] Go to Fig. 27 , method 2700 is Fig.26 An embodiment of method 2600 in. Fig. 27 Method 2700 in uses a monochromatic tunable source of image light, such as Figure 5 2704. The method 2700 includes setting 2702 an emission wavelength of a monochromatic tunable source and redirecting 2704 image light coupled into a 1D imager in an XY plane. In other words, when the 1D imager redirects the image light in a first plane, the wavelength of the tunable light source is not offset, so that the image light redirected in the first plane is coupled out at the same angle. Then, the next wavelength is set 2706 and the process is repeated, with the output power of the light source having its own value corresponding to the desired brightness of the pixels of the displayed image. The redirection in the XY plane includes angularly scanning 2708 a collimated light beam in the XY plane, or simultaneously forming an angular distribution 2710 of the brightness.

[0144] Reference now Fig.28 , method 2800 is Fig.26 An embodiment of method 2600 in. Fig.28 The method 2800 uses a spectrally tunable light source, such as Fig. 6A A tunable spectral light source 602 in. Fig.28 The method 2800 in the embodiment includes using a tunable spectral light source to provide 2802 image light having multiple spectral components corresponding to a vertical FOV of an image to be displayed. The image light having multiple spectral components is redirected 2804 in the XY plane by providing an angular distribution of brightness in the XY plane, which can be accomplished by scanning 2808 or forming an instantaneous angular distribution 2810. The angularly dispersed multi-wavelength image light is coupled out 2806 from a low-mode slab waveguide at an angular distribution corresponding to the spectral composition of the image light.

[0145] Go to Fig.29 , an augmented reality (AR) near-eye display 2900 includes a frame 2901 having the form factor of a pair of glasses. The frame 2901 supports a light engine 2908 for each eye, the light engine 2908 including a tunable spectrum light source as described herein, and a low-mode, i.e., single-mode or few-mode waveguide 2910 as disclosed herein, optically coupled to the light engine 2908. The AR near-eye display 2900 may also include an eye tracking camera 2904, a plurality of illuminators 2906, and an eye tracking camera controller 2907. The illuminator 2906 may be supported by the waveguide 2910 for illuminating a viewport 2912. The light engine 2908 provides a light beam having a spectrum representing a vertical 1D FOV to be projected into the user's eyes. The waveguide 2910 receives the light beam and expands the light beam on the viewport 2912. The horizontal 1D FOV may be provided by a 1D imager disclosed herein, such as a Figure 4A PIC-based imager 436, Fig. 9 Phased array 1D imager 904, Fig.11 A hybrid 1D imager 1104, or Fig.12 MEMS-based scanner 1204 in.

[0146] The purpose of the eye tracking camera 2904 is to determine the position and / or orientation of the user's eyes. Once the position and orientation of the user's eyes are known, the gaze convergence distance and direction can be determined. The displayed imagery can be dynamically adjusted to take into account the user's gaze to better realistically immerse the user in the displayed augmented reality scene, and / or provide specific functions for interacting with augmented reality. In operation, the illuminator 2906 illuminates the eye at the corresponding window 2912 so that the eye tracking camera can obtain an image of the eye, and provides a reference reflection, i.e., a bright spot. The bright spot can be used as a reference point in the captured eye image to facilitate the determination of the eye gaze direction by determining the position of the eye pupil image relative to the bright spot image. In order to avoid distracting the user's attention with the illumination light, the illumination light can be made invisible to the user. For example, infrared light can be used to illuminate the window 2912.

[0147] The function of the eye tracking camera controller 2907 is to process the images obtained by the eye tracking camera 2904 to determine the eye gaze direction of the user's eyes in real time. In some embodiments, the image processing and eye location / orientation determination functions may be performed by a central controller (not shown) of the AR near-eye display 2900. The central controller may also provide control signals to the light engine 2908 based on the determined eye location, eye orientation, gaze direction, eye vergence, etc.

[0148] refer to Fig.30 , HMD 3000 is an example of an AR / VR wearable display system that surrounds the user's face for greater immersion into an AR / VR environment. The function of HMD 3000 is to enhance the view of the physical, real-world environment with computer-generated imagery, and / or to generate completely virtual 3D imagery. HMD 3000 may include a front body 3002 and a strap 3004. The front body 3002 is configured to be placed in front of the user's eyes in a secure and comfortable manner, and the strap 3004 may be stretched to secure the front body 3002 on the user's head. A display system 3080 may be arranged in the front body 3002 for presenting AR / VR images to the user. The side 3006 of the front body 3002 may be opaque or transparent.

[0149] In some embodiments, the front body 3002 includes a positioner 3008, an inertial measurement unit (IMU) 3010 for tracking the acceleration of the HMD 3000, and a position sensor 3012 for tracking the position of the HMD 3000. The IMU 3010 is an electronic device that generates data indicating the position of the HMD 3000 based on measurement signals received from one or more position sensors 3012, and the position sensor 3012 generates one or more measurement signals in response to the movement of the HMD 3000. Examples of the position sensor 3012 include: one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor that detects movement, a type of sensor used for error correction of the IMU 3010, or some combination thereof. The position sensor 3012 can be located outside the IMU 3010, inside the IMU 3010, or some combination of these two locations.

[0150] The localizer 3008 is tracked by an external imaging device of the virtual reality system so that the virtual reality system can track the position and orientation of the entire HMD 3000. The information generated by the IMU 3010 and the position sensor 3012 can be compared with the position and orientation obtained by tracking the localizer 3008 to improve the tracking accuracy of the position and orientation of the HMD 3000. As the user moves and turns in 3D space, accurate position and orientation are important for presenting an appropriate virtual scene to the user.

[0151] The HMD 3000 may also include a depth camera assembly (DCA) 3011 that captures data describing depth information of a local area surrounding part or all of the HMD 3000. To this end, the DCA 3011 may include a laser radar (LIDAR) or similar device. The depth information may be compared with information from the IMU 3010 to more accurately determine the position and orientation of the HMD 3000 in 3D space.

[0152] The HMD 3000 may also include an eye tracking system 3014 for determining the orientation and position of the user's eyes in real time. The position and orientation of the eyes obtained also allow the HMD 3000 to determine the gaze direction of the user and adjust the image generated by the display system 3080 accordingly. In one embodiment, the convergence, i.e., the convergence angle of the gaze of the user's eyes, is determined. Depending on the viewing angle and the eye position, the determined gaze direction and convergence angle may also be used for real-time compensation of visual artifacts. In addition, the determined convergence angle and gaze angle may be used to interact with the user, highlight objects, bring objects to the foreground, create additional objects or pointers, etc. An audio system may also be provided, which includes, for example, a set of small speakers built into the front body 3002.

[0153] Embodiments of the present disclosure may include an artificial reality system or be implemented in combination with an artificial reality system. The artificial reality system adjusts the sensory information about the outside world obtained by the senses (such as visual information, audio, tactile (somatic) information, acceleration, balance, etc.) in some way before presenting the sensory information to the user. As a non-limiting example, artificial reality may include virtual reality (VR), augmented reality (AR), mixed reality (MR), mixed reality, or some combination and / or derivative thereof. Artificial reality content may include fully generated content or generated content combined with captured (e.g., real-world) content. Artificial reality content may include video, audio, body or tactile feedback, or some combination thereof. Any of these contents may be presented in a single channel or multiple channels, such as in a stereoscopic video that produces a three-dimensional effect to the viewer. In addition, in some embodiments, artificial reality may also be associated with an application, product, accessory, service, or some combination thereof, which is used, for example, to create content in artificial reality and / or otherwise used in artificial reality (e.g., performing activities in artificial reality). Artificial reality systems that provide artificial reality content can be implemented on a variety of platforms, including wearable displays such as HMDs connected to a host computer system, standalone HMDs, near-eye displays with eyeglass form factors, mobile devices or computing systems, or any other hardware platform capable of providing artificial reality content to one or more viewers.

[0154] The present disclosure is not limited in scope by the specific embodiments described herein. In fact, in addition to those embodiments and modifications described herein, various other embodiments and modifications will be apparent to those of ordinary skill in the art according to the foregoing description and accompanying drawings. Therefore, such other embodiments and modifications are defined as falling within the scope of the present disclosure. In addition, although the present disclosure is described herein in a specific environment for a specific purpose in the context of a specific implementation, a person of ordinary skill in the art will recognize that its usefulness is not limited thereto, and the present disclosure can be beneficially implemented in any number of environments for any number of purposes. Therefore, the claims set forth should be interpreted in light of the full breadth and spirit of the present disclosure as described herein.

Claims

1. A device for providing image lines in an angular domain, the device comprising a low-mode waveguide, the low-mode waveguide comprising: an inner coupler for coupling image light into the low-mode waveguide; a 1×N beam splitter, the 1×N beam splitter being used to split the image light coupled by the inner coupler into N linear waveguides; N phase shifters, each phase shifter coupled to a specific one of the N linear waveguides for partially delaying image light propagating therein by a controllable amount; an array of N linear waveguide transmitters, each linear waveguide transmitter coupled to a specific one of said N phase shifters for transmitting said image light portion delayed thereby; as well as a slab waveguide portion coupled to the array of N linear waveguide transmitters for propagating in the slab waveguide portion delayed image light portions emitted by corresponding transmitters in the array of N linear waveguide transmitters, wherein N is an integer; wherein the slab waveguide portion further comprises a field of view expander in the slab waveguide portion, the field of view expander comprising a tunable cladding portion, the tunable cladding portion being transiently coupled to a core of the slab waveguide portion and being shaped to deviate light propagating in the core of the slab waveguide portion by a controllable amount; and, The tunable cladding portion comprises an array of triangular liquid crystal cladding portions extending transversely relative to an optical path of the image light in the core of the slab waveguide portion, wherein at least some of the triangular liquid crystal cladding portions have sides extending at an acute angle relative to the optical path.

2. The device according to claim 1, wherein: The slab waveguide portion includes a single-mode slab waveguide.

3. The device according to claim 1, wherein: The slab waveguide portion includes a few-mode slab waveguide supporting no more than 10 lateral propagation modes.

4. The device according to any one of claims 1 to 3, wherein: The 1×N beamsplitter includes a binary tree of tunable Mach-Zehnder interferometers for providing a controllable distribution of optical power of the image light among the N linear waveguides.

5. The device according to any one of claims 1 to 3, wherein: The planar waveguide portion also includes a hologram, which is configured to reflect the collimated beam portion of the image light in the hologram at multiple positions along the optical path of the collimated beam portion, so that the collimated beam portion reflected by the hologram is wider than the collimated beam portion that hits the hologram.

6. An apparatus for providing image lines in an angular domain, the apparatus comprising a low mode waveguide, the low mode waveguide comprising: an inner coupler for coupling image light into the low-mode waveguide; a tunable 1×N beam splitter for distributing the optical power of the image light coupled by the inner coupler among linear waveguides in an array of N linear waveguides; as well as a slab waveguide portion including a collimating element for converting lateral positioning of a linear waveguide in the array of N linear waveguides into a beam angle of an image light portion propagating in a linear waveguide in the array of N linear waveguides, wherein N is an integer; wherein the slab waveguide portion further comprises a field of view expander in the slab waveguide portion, the field of view expander comprising a tunable cladding portion, the tunable cladding portion being transiently coupled to a core of the slab waveguide portion and being shaped to deviate light propagating in the core of the slab waveguide portion by a controllable amount; and The tunable cladding portion comprises an array of triangular liquid crystal cladding portions extending transversely relative to an optical path of the image light in the core of the slab waveguide portion, wherein at least some of the triangular liquid crystal cladding portions have sides extending at an acute angle relative to the optical path.

7. The device according to claim 6, wherein: The slab waveguide portion includes a single-mode slab waveguide; or, wherein the slab waveguide portion includes a few-mode slab waveguide supporting no more than 10 lateral propagation modes.

8. The apparatus of claim 6 or claim 7, wherein: The 1×N beamsplitter includes a binary tree of Mach-Zehnder switches for switching the image light between the N linear waveguides.

9. The apparatus according to any one of claims 6 to 7, wherein: The planar waveguide portion also includes a hologram, which is configured to reflect the collimated beam portion of the image light in the hologram at multiple positions along the optical path of the collimated beam portion, so that the collimated beam portion reflected by the hologram is wider than the collimated beam portion that hits the hologram.

10. A device for providing image lines in an angular domain, the device comprising: A micro-electromechanical system MEMS beam scanner comprising: a tiltable reflector for scanning image light in a first plane; a low-mode slab waveguide, the low-mode slab waveguide being in the first plane, the low-mode slab waveguide being used to propagate image light scanned by the MEMS beam scanner; and A coupler, the coupler being used to receive the image light scanned by the MEMS beam scanner and couple the image light to the low-mode slab waveguide; wherein the low-mode slab waveguide further comprises a field of view expander in the slab waveguide portion, the field of view expander comprising a tunable cladding portion, the tunable cladding portion being transiently coupled to a core of the low-mode slab waveguide and being shaped to deviate light propagating in the core of the slab waveguide portion by a controllable amount; and The tunable cladding portion comprises an array of triangular liquid crystal cladding portions extending transversely relative to an optical path of the image light in the core of the low-mode slab waveguide, wherein at least some of the triangular liquid crystal cladding portions have sides extending at an acute angle relative to the optical path.

11. The device according to claim 10, wherein: The low-mode slab waveguide is a single-mode slab waveguide; or, wherein the low-mode slab waveguide is a few-mode slab waveguide supporting no more than 10 lateral propagation modes.

12. The apparatus according to any one of claims 10 to 11, wherein: The low-mode slab waveguide also includes a hologram, which is configured to reflect the collimated beam portion of the image light in the hologram at multiple positions along the optical path of the collimated beam portion, so that the collimated beam portion reflected by the hologram is wider than the collimated beam portion that hits the hologram.

Images