Glasses device for a wide field of view display

Abstract

The present invention discloses a glasses device, which includes: at least one light display engine (LDE), the light display engine being configured to generate at least one image on a display (disp1) of the light display engine; a waveguide (WG), the waveguide being configured to guide light from the light display engine towards the user's eyes to make the image (Im1) visible to the user, wherein the display (disp1) is displaced (d) on one side with respect to the optical axis of the light display engine, such that the image (Im1) is visible to the user on the corresponding side of the field of view (HFoV) of the glasses device.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to EP20152557, titled "Glasses Device for Wide - Field - of - View Displays", filed on January 17, 2020. Background of the Invention

[0003] The present disclosure relates to the fields of optics and photonics. The present disclosure can be applied in the field of conformable and wearable optical devices (i.e., AR / VR glasses (augmented reality / virtual reality)), and more specifically, can be applied in the field of augmented reality glasses with monocular or binocular systems for see - through.

[0004] This section is intended to introduce the reader to aspects of the art that may be related to various aspects of the invention described and / or claimed below. This discussion is considered to be helpful in providing background information to the reader to facilitate a better understanding of the various aspects of the invention. Accordingly, it should be understood that these statements should be read from this perspective and not as an admission of prior art.

[0005] AR / VR glasses are regarded as the next - generation human - machine interface. The development of AR / VR glasses (and more generally, glasses - mounted electronic devices or head - mounted devices (also referred to as HMDs)) is associated with many challenges, including reducing the size and weight of such devices and improving the image quality (in terms of contrast, field of view, color depth, etc.), which should be realistic enough to achieve a truly immersive user experience.

[0006] The trade - off between optical image quality and physical size has motivated research into ultra - compact optical components that can be used as building blocks for more complex optical systems such as AR / VR glasses.

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

[0008] However, the aspect ratio of the display does not necessarily match the field of view (FoV) provided by the optical system of the AR / VR glasses. Generally, a very wide FoV is desired, but since the FoV provided by the optical system is wider than the aspect ratio of the display, the display is set at the center of the field of view, and the HMD has a FoV smaller than the display area in the field of view. Thus, it is the aspect ratio of the display rather than the optics of the optical system that imposes a limitation on the display area, and the field of view provided by the optical system is not fully utilized. Summary of the Invention

[0009] Devices according to some embodiments include: at least one waveguide having a coupler, at least a first display configured to generate a first image, and a lens system having an optical axis, the lens system being configured to direct at least the first image onto the coupler, wherein the first display is offset toward a first side of the optical axis of the lens system.

[0010] In some embodiments, the device further includes a second display configured to generate a second image, wherein the second display is offset toward a second side of the optical axis. In some embodiments, the first display and the second display are arranged on opposite sides of the optical axis.

[0011] In some embodiments, the coupler is configured to couple the first image into the waveguide using a positive diffraction order and to couple the second image into the waveguide using a negative diffraction order. In some embodiments, the coupler may be configured to couple the first image and the second image into the waveguide using a diffraction order with an absolute value greater than one.

[0012] In some embodiments, the optical axis does not intersect any display of the device.

[0013] In some embodiments, the waveguide further includes a coupler and at least one pupil expander along at least a first optical path from the coupler to the coupler.

[0014] In some embodiments, the waveguide further includes a coupler and a first pupil expander and a second pupil expander along a first optical path from the coupler to the coupler, the first pupil expander and the second pupil expander being configured to direct the first image to the coupler.

[0015] In some embodiments, the waveguide further includes a coupler and a third pupil expander and a fourth pupil expander along a first optical path from the coupler to the coupler.

[0016] Methods according to some embodiments include generating at least a first image on a first display and using a lens system having an optical axis to direct at least the first image onto a coupler of a waveguide, wherein the first display is offset toward a first side of the optical axis of the lens system.

[0017] In some embodiments, the method further includes generating at least a second image on a second display and using the lens system to direct the second image onto the coupler of the waveguide, wherein the second display is offset toward a second side of the optical axis. In some embodiments, the first display and the second display are arranged on opposite sides of the optical axis.

[0018] Some embodiments also include using a coupler to couple a first image into the waveguide using a positive diffraction order and a second image into the waveguide using a negative diffraction order.

[0019] In some embodiments, the coupler is configured to couple the first image and the second image into the waveguide using a diffraction order with an absolute value greater than one.

[0020] According to one aspect of the present disclosure, a glasses device is disclosed, the glasses device comprising:

[0021] - at least one light display engine configured to generate at least one first image on a first display of the light display engine,

[0022] - a waveguide configured to direct light from the light display engine towards a user's eye to make the first image visible to the user,

[0023] wherein the first display is offset on one side relative to an optical axis of the light display engine such that the first image is visible to the user on a corresponding side of a field of view of the glasses device.

[0024] According to the present disclosure, the glasses device is configured to display an image at a periphery of a field of view of a user wearing the glasses device. Generally speaking, the display of the light display engine is centered on the optical axis of the light display engine. According to the present disclosure, the display of the light display engine is offset from the optical axis of the light display engine, that is, the optical axis of the projection lens of the light display engine is offset. In this way, the image is no longer displayed at the center of the field of view of the device, but the image is displayed on one side of the field of view of the device, so that on one side of the user's field of view, the central part of the field of view has no image. With this arrangement, the user can see the real world through the glasses device. Therefore, virtual information can be displayed to the user on at least one side of the user's field of view without disturbing the central part of the field of view. The virtual information is displayed on at least one side of the human field of view without superimposing virtual and real images at the FoV center. This aspect is applied to:

[0025] - glasses for a driver (airplane, car, bicycle,...) that provide the driver with information for supplementing directions, displacements, various vehicle information (such as speed, target distance, available fuel, and more).

[0026] Informative glasses that allow walking (e.g., in a city, a store, or a museum), running, or cycling without disturbing the central field of view.

[0027] - glasses for adding subtitles to a movie or a play in a theater.

[0028] According to an embodiment of the present disclosure, a first polar angle range of a light beam associated with the first image and incident on the waveguide is outside a cone of polar angles about normal incidence of the light on the waveguide, and the waveguide is configured to guide the first polar angle range. According to this embodiment, the waveguide is preferably configured to guide an off-axis angle of the light beam. When the first display is shifted relative to the optical axis, the light beam projected onto the user's image is off-axis. In other words, the light beam of interest is not in a cone about the optical axis of the projection lens, but in a cone with a polar angle off-axis relative to the optical axis of the projection lens. Thus, according to this embodiment, the waveguide is configured to guide such a range of off-axis polar angles.

[0029] According to another embodiment of the present disclosure, the refractive index of the waveguide is higher than 1.5. The FoV of the waveguide depends on the material of the waveguide, and more specifically on the refractive index of the waveguide. Thus, using a higher refractive index allows increasing the field of view of the waveguide, thereby allowing encapsulating at least one display on one side of the FoV of the optical system and making the central display area without virtual information wider.

[0030] According to another embodiment of the present disclosure, the waveguide includes a coupler configured to couple the first range of polar angles of the incident light, wherein the coupler includes a diffraction grating having a grating pitch determined for a grazing incidence angle corresponding to an extreme angular value of the first polar angle range of the incident light. According to this embodiment, the grating pitch of the coupler is determined for a specific range of polar angles to be coupled into the waveguide. Since no light rays hit the coupler in a cone of polar angles about normal incidence, the coupler diffraction grating can be designed for a higher grazing incidence angle, thereby providing more freedom in the pitch dimension of the coupler.

[0031] According to another embodiment of the present disclosure, an optical display engine has a second display, and the optical display engine is configured to generate a second image on the second display, wherein the second display and the first display are symmetrically shifted relative to the optical axis of the optical display engine such that the second image is visible to the user on the other side of the field of view of the glasses device. According to this embodiment, the optical display engine includes two displays, with one display disposed on each side but not adjacent. The two displays are symmetrically disposed on each side of the optical axis of the optical engine. In this way, virtual information can be displayed on both sides of the user's field of view, and there is no image in the central portion of the FoV.

[0032] According to another embodiment of the present disclosure, the eyewear device includes a second light display engine configured to generate at least one second image on the display of the other light display engine, wherein the second light display engine and the light display engine are disposed on one side each, such that the second image is visible to the user on the other side of the field of view of the eyewear device. According to this alternative, the other light display engine is used to display a second image within the user's field. The two light display engines are disposed on one side each, such that the light beams generated by the two light engines are guided by the waveguide. The two light display engines are configured such that their optical axes are parallel.

[0033] According to another embodiment of the present disclosure, the second polar angle range of the light beam associated with the second image and incident on the waveguide is outside the cone of the polar angle around the normal incidence of the light on the waveguide, and the waveguide is configured to guide the second polar angle range.

[0034] According to another embodiment of the present disclosure, the first polar angle range and the second polar angle range are symmetric with respect to the normal incidence of the light, and wherein the coupler is further configured to couple the second polar angle range of the incident light beam. According to this embodiment, the waveguide is configured to guide a specific angular range corresponding to a specific position of the display of the incident light. According to the present disclosure, the angular range of the light to be coupled corresponds to an off-axis angular range. Since no image is displayed in the central portion of the user's field of view, it is not necessary to couple a cone of the angular range spanning the incident axis of the light incident on the waveguide. Advantageously, the same coupler is configured to couple two off-axis angular ranges of the incident light.

[0035] According to another embodiment of the present disclosure, the coupler is configured to diffract the first image into a positive diffraction order and the second image into a negative diffraction order. According to this embodiment, the coupler operates in a dual mode, wherein positive and negative diffraction orders are used, such that the first image is sent on one side of the waveguide and the second image is sent on the other side of the waveguide.

[0036] According to another embodiment of the present disclosure, the coupler is configured to diffract the first image and the second image into diffraction orders having an absolute value greater than one. According to this embodiment, using a diffraction order of 2 or more allows for a larger pitch size to be used for the coupler, which is thus easier to manufacture.

[0037] According to another embodiment of the present disclosure, the waveguide includes at least one diffraction grating configured to deflect a first image by a deflection angle, wherein the grating pitch of the at least one diffraction grating is determined as a function of the deflection angle such that the maximum angular range of the first image is deflected. According to this embodiment, the waveguide includes a diffraction grating specifically configured to allow the maximum angular range of the light beam of the image coupled in the waveguide in the TIR (total internal reflection) mode to be deflected. In other words, this embodiment allows the image to be transmitted through the waveguide without being cropped by the angles diffracted from the TIR mode.

[0038] According to another embodiment of the present disclosure, the grating pitch Λ e is determined as follows:

[0039] ο If then where φ K is half of the deflection angle, where n2 is the refractive index of the waveguide material, is the maximum grazing incidence angle in the waveguide, M is the diffraction order, λ is the wavelength of the light coupled into the waveguide, and Δφ is the maximum angle of the deflected light obtained by obtained.

[0040] ο If then Λ e = M × λ × sin(φ K - Δφ / 2), and Δφ = sin -1 (sin(2 × φ K )) - N),

[0041] ο If then and where and Δ = (cosφ K ) 2 - 4 × α × (α + sinφ K ),

[0042] ο If then and

[0043] According to another embodiment of the present disclosure, the at least one diffraction grating is included in a first exit pupil expander, the first exit pupil expander being included in the waveguide and configured to expand the image in one direction and deflect the image towards a second exit pupil expander included in the waveguide.

[0044] According to another embodiment of the present disclosure, the second exit pupil expander is configured to expand the image in another direction and deflect the image towards the decoupler.

[0045] According to another embodiment of the present disclosure, according to any one of the above-cited embodiments, the glasses device includes a waveguide configured for each of red, green, and blue. According to this embodiment, when the system is an RGB system, the glasses device includes three waveguides for each eye.

[0046] According to a second aspect of the present disclosure, a waveguide is disclosed that includes a diffraction grating configured to deflect a light beam coupled into the waveguide by a certain deflection angle in total internal reflection (TIR) mode, wherein the grating pitch of the diffraction grating is determined as a function of the deflection angle such that the maximum angular range of the light beam remains in the waveguide in TIR mode after deflection. According to this aspect of the present disclosure, a diffraction grating is proposed that is specifically configured to allow the maximum angular range of the light beam of an image coupled in TIR mode to be deflected in the waveguide. In other words, this aspect of the disclosure allows an image to be transmitted through the waveguide without being cropped by angles diffracted out of the TIR mode.

[0047] According to an embodiment of this aspect, the grating pitch Λ e is determined as follows:

[0048] ο If then where φ K is half of the deflection angle, where n2 is the refractive index of the waveguide material, is the maximum grazing incidence angle in the waveguide, M is the diffraction order, λ is the wavelength of the light coupled into the waveguide, and Δφ is the maximum angle of the deflected light obtained by

[0049] ο If then Λ e = M×λ×sin(φ K -Δφ / 2), and Δφ = sin -1 (sin(2×φ K ) - N),

[0050] ο If then and where and Δ = (cosφ K ) 2 - 4×α×(α + sinφ K ), ​

[0051] ο If then and

[0052] According to another embodiment, the diffraction grating is an exit pupil expander, which is included in the waveguide and configured to expand a light beam in one direction and deflect the light beam towards another exit pupil expander included in the waveguide or the coupler of the waveguide.

[0053] According to an embodiment of the second aspect, an eyewear device is disclosed, which includes:

[0054] - A light engine configured to generate an image on a grid display of the light engine,

[0055] - A waveguide according to any one or any combination of the embodiments cited above, the waveguide being configured to guide light from the light engine towards the user's eyes to make the image visible to the user.

[0056] According to a third aspect of the present disclosure, an eyewear device is disclosed, which includes features of any one or any combination of the embodiments of the first aspect of the present disclosure and / or features of any one or any combination of the embodiments of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The present disclosure can be better understood with reference to the following description and drawings, which are given by way of example and do not limit the scope of protection, and in which:

[0058] Figure 1 An exemplary off-axis illumination system for a DLP (representing Digital Light Processing) microdisplay is shown,

[0059] Figure 2 Another exemplary off-axis illumination system for a DLP microdisplay is shown,

[0060] Figure 3 An exemplary LCOS (representing Liquid Crystal on Silicon) typical illumination system is shown,

[0061] Figure 4 The principle of time-sequential color illumination is shown,

[0062] Figure 5 An exemplary non-pupil-forming optical design is shown,

[0063] Figure 6 An exemplary pupil-forming optical design is shown,

[0064] Figure 7Shows an exemplary planar optical system,

[0065] Figure 8 Shows different display aspect ratios and FoV of the optical system,

[0066] Figure 9 Shows an example of two inscribed displays within the spatial acceptance region of an optical system according to an embodiment of the present disclosure,

[0067] Figure 10 Shows variations of the horizontal and vertical fields of view as a function of the refractive index n2 of the waveguide,

[0068] Figure 11A Shows an exemplary spatial position of the display,

[0069] Figure 11B Shows an angle according to an embodiment of the present disclosure which is converted by the lens of the optical system from Figure 11A the pixel position on the display into an angle,

[0070] Figure 11C Shows a diffraction region according to an embodiment of the present disclosure which remains in the TIR mode after diffraction by the corrugated grating,

[0071] Figure 11D Shows a diffraction angle according to an embodiment of the present disclosure which represents the maximum angular range achieved by an optical device having a corrugated grating,

[0072] Figure 12 Shows an exemplary light engine having two displays,

[0073] Figure 13 Shows the spherical angles calculated for a normalized lens which is a lens whose components are uniformly scaled to have a total focal length f = 1,

[0074] Figure 14 Shows the spot diagrams of the corners of the display in spherical angle coordinates simulated using optical design software in,

[0075] Figure 15 is a schematic cross-sectional view through a set of two displays, a projection lens system, and a waveguide having a coupler region,

[0076] Figure 16 Shows an exemplary schematic light path within the waveguide according to an embodiment of the present disclosure,

[0077] Figure 17 Shows the definitions of critical rays, grazing-incidence rays, and diffracted rays,

[0078] Figure 18 Shows the coordinate system for conical diffraction,

[0079] Figure 19 Shows the incident angle of diffraction into the waveguide,

[0080] Figure 20 Shows the diffraction angle in the TIR mode in the waveguide,

[0081] Figure 21 Shows the double-diffraction mode,

[0082] Figure 22 Shows the acceptance angle as a function of the grating orientation of the corrugated grating,

[0083] Figure 23 Shows the grating pitch as a function of the grating orientation,

[0084] Figure 24A Shows another exemplary spatial position of the display,

[0085] Figure 24B Shows the angle according to an embodiment of the present disclosure, This angle is converted from the pixel position on the display to an angle by the lens of the optical system,

[0086] Figure 24C Shows the diffraction region according to an embodiment of the present disclosure, This diffraction region remains in the TIR mode after diffraction by the corrugated grating,

[0087] Figure 24D Shows the diffraction angle according to an embodiment of the present disclosure, This diffraction angle represents the maximum angular range achieved by the optical device with the corrugated grating,

[0088] Figure 25 Shows an exemplary glasses device according to an embodiment of the present disclosure, which shows an exemplary spatial position of the display according to an embodiment of the present disclosure relative to the optical axis of the projection lens of the light engine,

[0089] Figure 26 Shows another exemplary glasses device according to an embodiment of the present disclosure, which shows an exemplary spatial position of a plurality of displays according to an embodiment of the present disclosure relative to the optical axis of the projection lens of the light engine. Detailed Description

[0090] Waveguide-based optical systems for augmented reality (AR) typically use diffraction gratings for internal coupling and pupil expansion. Due to the eye pupil expander (EPE), the vertical field of view (VFoV) (FoV) is more restricted than the horizontal field of view (HFoV). The typical aspect ratios of microdisplays used in AR applications are 4:3, 3:2, and 16:9. Some embodiments of the present disclosure provide an optical system with a wider field of view.

[0091] According to one aspect of the present disclosure, a glasses device is proposed that utilizes a wide HFoV by using one or two microdisplays for each eye to cover the virtual image on the left or right side of the FoV while leaving the central part of the FoV without enhanced display. Such displays can be used in applications where virtual information does not need to be displayed in the center of the field of view.

[0092] The field of view of the glasses device corresponds to the angular field of view, where when a user wearing the glasses device views through the glasses device, the glasses device renders an image for the user. The horizontal field of view corresponds to the part of the field of view along the horizontal axis, which is perpendicular to the line of sight of the user wearing the glasses device and has a direction parallel to the line joining the centers of the eyeballs.

[0093] Different techniques can be used to design head-mounted displays (HMDs) related to display types, lighting systems, imaging systems, etc. A brief review of possible techniques for head-mounted displays is given below.

[0094] Monitor type 。

[0095] The embodiments described herein can use any of the following types of displays: LCOS (liquid crystal on silicon), DLP (digital light projection), and OLED (organic light-emitting diode), etc.

[0096] Illumination system 。

[0097] The flat-panel microdisplay of the OLED type is light-emitting and does not require an illumination system. This simplifies the design and reduces the weight limitation. Unfortunately, this comes at the cost of brightness, as the brightness is limited by the brightness of the screen itself, which is lower than that of other systems with external light sources, and also because the large geometric extent of the display results in significant light loss through the imaging system.

[0098] LCOS - or DLP - based systems are typically illuminated by one or more LEDs, and in order to obtain the colors in the projected image, the light source provides RGB illumination in a time - sequential manner. The illumination system based on LED light sources is not an optimal solution due to the high geometric extent of the LEDs, and furthermore, the illumination system for LCOS microdisplays is more laborious due to the need for polarization management. One aspect of polarization management is that in order not to lose one polarization, the system can employ polarization beam splitters for recycling. The polarization recycling is at least twice the geometric extent, such that in order for a particular implementation to be light - efficient, the original geometric extent of the selected light source is at least half of the original geometric extent of the imaging optics.

[0099] The illumination system can also use beam forming to maintain efficiency. In many cases, the light source produces a disk - shaped illumination, while the display geometry is rectangular. In order to illuminate the entire display area, the illuminated footprint can be larger than the display, which results in light loss. Since uniform illumination is desired, the illuminated footprint can be chosen to be several times the area of the microdisplay region. Components can be used during illumination to convert the illumination beam into a uniform rectangular illumination section that is the same size as the microdisplay. Here, a light pipe or a fly - eye integrating lens can be used.

[0100] Another difference between LCOS - and DLP - based systems is that DLP - based systems require off - axis illumination.

[0101] Figure 1 An exemplary off - axis illumination system for a DLP microdisplay is shown. Figure 1 The display includes a high - intensity gas - discharge (HID) lamp, which has a parabolic reflector 101, a converging lens 102, a color - wheel motor 103 for driving a color wheel 104, an integrating fly - eye lens system 105 for converting the circular beam into a rectangular beam, a total internal reflection (TIR) prism 106, a digital micromirror device (DMD) 107, and a projection lens system 108.

[0102] Figure 2Shows another exemplary off-axis illumination system for a DLP microdisplay. In this example, the illumination includes three LED light sources 201 (for red light), 202 (for green light), and 203 (for blue light), which are triggered in a time-sequential mode and guided by dichroic filters 207, 208. The optical integrator 204 converts the circular beam into a rectangular beam. The relay system images the rectangular end of the conduit onto a digital light processor (DLP), generating an image to be displayed on a digital micromirror device (DMD) array 205. Each pixel of the DMD array can be in an on or off state by moving the corresponding micromirror. When the pixel is on, the micromirror reflects the light to the projection lens 206. When the pixel is off, the light is reflected elsewhere (e.g., into a heat sink). These pixels appear dark in the display area of the smart glasses because there is no transmitted light for these pixels.

[0103] In comparison, the illumination system for a liquid crystal on silicon (LCOS) display is more complex due to the polarization management system. Figure 3 Shows an exemplary LCOS typical illumination system. There is a beam-forming integrator compound eye system. The exemplary light engine has three LCOS displays. It is different from the Figure 4 time-sequential illumination system shown. The image to be displayed by such a light engine is generated on an LCOS panel (blue, green, and red direct-drive image light amplifier (D-ILA)). Figure 4 The example of Figure 3 has an LCOS panel for each RGB color. The display of Figure 3 includes a lamp 301, which can be an arc lamp. The light from the arc lamp is integrated using an integrating lens system including an integrating lens 302 and polarized by a polarizer 303. The dichroic filter 304 separates the light into a blue beam, a red beam, and a green beam. The blue beam travels to a pre-polarizer 305, and the red and green beams travel to a pre-polarizer 306. The blue light travels to a blue-tuned polarizer 307 and is modulated by a corresponding D-ILA (direct-drive image light amplifier) device 308. The green light travels to a green-tuned polarizer 309 and is modulated by a corresponding D-ILA device 310. The red light travels to a red-tuned polarizer 311 and is modulated by a corresponding D-ILA device 312. The modulated light is recombined at an X-combiner 313 and provided to a projection lens system 314. In the

[0104] Figure 4The principle of sequential color illumination is shown. A sequential color illumination system is a device that switches colors in the order of red to green to blue and back to red, with some white sometimes to achieve a certain light efficiency. The switching is accomplished by triggering a set of three or more LEDs, or by selecting a color path from a white light source with a dynamic or solid-state color switcher.

[0105] Image forming system 。

[0106] The current basic form of the optical design for an HMD is an eyepiece, an objective lens, and projection optics. Exemplary eyepiece and objective lens systems are described below.

[0107] The eyepiece is designed as a non-pupil-forming design. Figure 5 An example of such a design is shown in. It does not require an intermediate image plane conjugate to the microdisplay 501. The pupil of the eye is the pupil of the HMD. Compared with the pupil-forming design, this system is smaller and simpler, but this system has a shorter projection distance between the image source and the virtual image, thus placing the entire assembly in front of the head, close to the eyes.

[0108] The second optical method is the pupil-forming design, which is more complex. Figure 6 An example of this design is shown in. This design is more like a compound microscope, in which the first set of lenses forms an intermediate image 601 of the display 602. This intermediate image is transferred by the second set of lenses, where a pupil is formed. The potential advantage is that the pupil-forming design provides more path length from the image plane to the eye. This gives the designer more freedom to insert mirrors (e.g., 603, 604) as needed to fold the optical axis and thus move the optical components away from the face to a more favorable weight and center of gravity position. Some disadvantages are that the additional lenses increase the weight and cost of the HMD, and there is no image outside the exit pupil.

[0109] In each case, it is desirable for the optical design to transfer the image with a sufficiently small amount of residual aberration, manual focusing (if needed), and proper alignment with a binocular system. In addition, the optical design preferably provides a sufficiently large exit pupil (eye box) such that when the HMD is shifted onto the head and at least 25 mm of the good eye distance, the user does not lose the image, thus allowing the user to wear glasses.

[0110] Exemplary optical systems according to embodiments of the present disclosure are disclosed below.

[0111] The principles disclosed herein are generally applied to an optical system that is a hybrid type between a non-pupil and a pupil-forming optical design, which is based on planar optical components placed on a spectacle plate (also called a waveguide).

[0112] This optical system basically has the architecture of a non-pupil system, but the pupil is transmitted through a waveguide by total internal reflection (TIR) and is also expanded by various optical components, rather than placing the eye at the exit pupil of the optical system. Total internal reflection refers to the complete reflection of light within the waveguide from the surrounding surface back into the waveguide. The TIR mode occurs when the incident angle is greater than the critical angle.

[0113] Figure 7 An exemplary system is shown in Figure 7 The glasses device shown in

[0114] Figure 7 Figure 7

[0115]

[0116] In a typical AR system based on planar optical components, the longitudinal field of view is reduced due to the corrugated grating EPE. In a system using a dual diffraction mode, the spatial extent of the display that matches the field of view angular range is very wide. For example, for a system with a waveguide refractive index n2 = 1.5, the horizontal field of view HFoV is 48.5, and the vertical field of view VFoV = 23.7, which corresponds to an angular aspect ratio of 2:1.

[0117] Typically, the display has a spatial aspect ratio of 16:9, 3:2, or 4:3. Figure 8 Compare the aspect ratios under discussion on the same scale as the FoV range. In Figure 8 , the top rectangle corresponds to the maximum display size transmitted through the system of the coupler and the corrugator for a waveguide plate with n2 = 1.5. The three lower rectangles correspond to displays with spatial aspect ratios of 16:9, 3:2, and 4:3 respectively.

[0118] The display that best matches the system FoV shown at the top layer is the display with an aspect ratio of 16:9. 16:9 is the aspect ratio that least disrupts the horizontal field of view. According to one of the principles disclosed herein, an optical system is provided in which the spatial field can horizontally encapsulate one or more displays while maintaining the center of the FoV without any displayed information. Such a system can operate to display virtual information only peripherally and not at the center of the observer's FoV.

[0119] Figure 9 An example of such a display area is shown in

[0120] As Figure 8 shown, it may not be feasible to insert two displays with an aspect ratio of 4:3 on each side of the FoV. Figure 8 The FoV 801 of

[0121] is not wide enough to encapsulate two displays side by side with a large gap therebetween. This requires an extremely wide horizontal FoV. Figure 8 Even if only one display is shifted to one side of the FoV so that the central part of the FoV has no image, the same situation occurs. For example, if it is desired to display virtual information only on one side of the FoV, then Figure 8 the FoV 801 of

[0122] The FoV varies with the refractive index of the waveguide. It can be seen that very different behaviors are obtained for the variations of the horizontal and vertical FoV. For this purpose, the variations of the HFoV and VFoV for a system with a double diffraction pattern are compared.

[0123] The HFoV equation is:

[0124]

[0125] And the VFoV equation is:

[0126]

[0127] where φ K is the orientation of the EPE grating. It is typically equal to 45°. The variable n2 is the refractive index of the waveguide. The angles are design parameters for the grating, and the values of the angles can be set to:

[0128] Exemplary values are

[0129] Using these equations, Figure 10 is a graph of the field of view as a function of n2 (in degrees). The graph clearly shows that the horizontal FoV 1001 grows faster with the increase of n2 compared to the vertical FoV 1002.

[0130] According to an embodiment of the present disclosure, a waveguide is provided that has a refractive index, thereby allowing a display to be encapsulated on the left or right side of the FoV or two displays to be encapsulated: one display on the left side of the field of view and the other on the right side of the field of view, and still leaving an unobstructed field of view in the central part of the visual system in both cases.

[0131] An exemplary optical system according to the present disclosure can be an eyewear device, such as Figure 7 the eyewear device shown in. Exemplary parameters are as follows: the refractive index of the waveguide is n2 = 1.9, the grating is designed for λ = 625 nm, M = ±2, Λ i = 697.3 nm, Λ e = 652.4 nm, where M is the diffraction order, and Λ i and Λ e are the grating pitches of the coupler and the outcoupler, respectively.

[0132] The total normalized display size transmitted through the system is 2.65 × 0.78, which is actually a wide aspect ratio of 10:3. The normalized display size means the size that the display will have when using a projection lens with a focal length equal to 1 mm.

[0133] Two 4:3 displays with a normalized size of 1.04×0.78 can be encapsulated in this area, and the size of the central area where nothing is displayed in the field of view is 0.57×0.78.

[0134] To design an optical system that provides the above functions, the horizontal field of view (HFoV) and the vertical field of view (VFoV) can be determined based on the refractive index of the waveguide. A waveguide with a specific refractive index (e.g., higher than 1.5) is selected, and the HFoV and VFoV given by this waveguide are determined.

[0135] Some embodiments may use one display. Other embodiments may use two displays. The selection of the display can be performed according to the aspect ratio to be rendered. In some embodiments, two displays with an aspect ratio of 4:3 are used, but in other embodiments, other aspect ratios are used. The displays can be arranged to provide an effective use of the horizontal field of view. For example, the displays can be placed at a spatial position relative to the optical axis of the projection lens such that the light beam incident on the coupler exits the optical system at the periphery of the HFoV.

[0136] In some embodiments, as Figure 25 shown, the display disp1 is displaced by a distance d on one side of the optical axis of the projection lens of the optical display engine LDE, and d is the distance between the optical axis of the projection lens and the center of the display disp1. The optical axis of the projection lens is along the z-axis of the orthogonal coordinate system. The display disp1 is displaced by a distance d in the xz plane, which generally corresponds to the horizontal plane of the glasses device.

[0137] The light beam of the image generated on the display disp1 of the optical engine LDE is coupled into the waveguide WG and guided by the waveguide WG towards the user's eyes so that the image Im1 is visible to the user on one side of the horizontal field of view HFoV of the system, as schematically shown in Figure 25 shown.

[0138] In Figure 26 the embodiment, two displays disp1 and disp2 of the optical display engine LDE are shown. Each of the displays is symmetrically displaced by the same distance d' on one side of the optical axis of the projection lens, and d' corresponds to the distance between the optical axis and the center of the display. In a similar manner to Figure 25 above, the optical axis of the projection lens is along the z-axis of the orthogonal coordinate system. The displays disp1 and disp2 are displaced by a distance d' in the xz plane, which generally corresponds to the horizontal plane of the glasses device.

[0139] In some embodiments, the distance d' can be selected as follows: where w tot is the width of the total normalized display size transmitted through the system, and wdisp is the width of the display encapsulated on one side of the system. For example, using the values given above, d' = tan(2.65 / 2 - 1.04 / 2). The light of the images generated on each of the displays disp1 and disp1 in the light engine LDE is coupled into the waveguide WG and guided by the waveguide WG towards the user's eyes so that the images Im1 and Im2 are visible to the user on each side of the horizontal field of view HFoV of the system, which is schematically shown in Figure 26 schematically shown.

[0140] Figure 11A An exemplary spatial positioning of two displays of the light engine is shown. Here, the displays 1101, 1102 are shown such that the optical axis of the projection lens is perpendicular to the image plane of the display.

[0141] It can be seen that the two displays are placed in a non - intersecting manner, leaving a central space between the displays. Each display is shifted a distance d' from the optical axis of the projection lens in the horizontal direction and is centered on the optical axis of the projection lens in the vertical direction.

[0142] Figure 11B shows the angle which is converted from the pixel position on the display to an angle by the lens of the optical system. Figure 11B represents the input angle coupled into the waveguide before the coupler. It can be seen that there is a missing region between the edges 1110 and 1112, within which no information is added to the waveguide. Only the angles between the closed regions exist in the coupler and diffract in the TIR mode and are thus transmitted to the eye.

[0143] Figure 11C shows the diffraction region which remains in the TIR mode after diffraction by the first EPE corrugated grating of the optical system. Figure 11D shows the diffraction angle of the first EPE output which represents the maximum angular range achieved in the optical device with the above - mentioned parameters.

[0144] In some embodiments, in the case where the width of the central portion is relatively narrow, the left - hand display can have its right - hand side cropped by displaying only a black band, while the right - hand display can have a left - hand border provided by a black display strip in order to provide a larger area for the central portion of the FoV where nothing is shown. This can be done, for example, by cropping the right - hand or left - hand side of the image generated on the display of the light engine and setting these portions of the image to black pixels.

[0145] The field of view of the example provided above is: horizontal = 105.9, vertical = 42.6, diagonal = 108.2.

[0146] According to an embodiment of the present disclosure, since there is no light hitting the coupler, the coupler is conical for the polar angle around the normal incidence (missing for each incident polar angle between the edges 1110 and 1112 as can be seen in Figure 11B ), the coupler can be configured to obtain a higher angle in the case of grazing incidence in the waveguide than . For this purpose, in the following equations, for example

[0147]

[0148] In other embodiments, for other values can be used. This angle can be lower than the angle in the graph of Figure 11B , in which the edges 1110, 1112 cross the horizontal axis.

[0149] Figure 12 is a schematic perspective view of a display system and a projection lens system according to some embodiments. Although the displays 1201 and 1202 are spaced apart from each other on opposite sides of the optical axis 1205, both displays supply light to the same projection lens system 1203. In this example, the displays do not intersect the optical axis 1205. The inner coupling grating is intended to be placed at the exit pupil position (shown as being approximately at 1204). At the exit pupil position, the optical design software can calculate the spot diagram in spherical coordinates and compare its overall form with the spot diagram calculated for a lens with a normalized focal length. Since it is very difficult to design a lens that accommodates a horizontal FoV higher than 100 degrees, the sizes and aspect ratios are different, but at least allow for a visual comparison, and this is the case for comparison with Figure 13 and Figure 14 , where Figure 13 shows the spherical angle calculated for the normalized lens while Figure 14 shows the spherical angle simulated using the optical design software

[0150] Figure 15 is a schematic cross-sectional view through a set of two displays 1501, 1502, a projection lens system 1503, and a waveguide 1504 having a coupler region 1505. Figure 15 shows the paths of exemplary light rays from the displays 1501 and 1502. According to an embodiment, the light from the upper (as shown on the page) display 1501 travels in an upward direction once coupled into the waveguide, and the light from the lower display 1502 travels in a downward direction once coupled into the waveguide. Figure 15The cross-section can represent a horizontal layering through the display system, where, for example, display 1501 is located on the left side and display 1502 is located on the right side.

[0151] In the case where virtual information is displayed on both sides of the HVoF, an implementation with a complete AR headset for augmented reality equipped for both eyes can have such one lens and two displays for each eye, which amounts to two projection lenses, four displays, and two waveguides for the headset.

[0152] In the case where virtual information is only displayed on one side of the HFoV, a complete AR headset for augmented reality equipped for both eyes can have such one lens and one display for each eye, which amounts to two projection lenses, two displays, and two waveguides for the headset.

[0153] Figure 16 A pair of symmetric waveguides with their planar optical components are schematically shown. In an implementation using two waveguides, the two waveguides can be identical to each other, or the two waveguides can be, for example, mirror images of each other.

[0154] At waveguide 1600, the exit pupil of the projection lens can be matched with the coupler 1601. One of the images diffracts towards the eye pupil expander 1602 as a positive diffraction order (e.g., +2 order), and the other image diffracts towards the eye pupil expander 1603 as a negative diffraction order (e.g., -2 order).

[0155] According to some implementations, second-order diffraction is used, which allows the use of a relatively large pitch size. However, other implementations are possible, and any positive or negative order can be used.

[0156] According to an implementation of the present disclosure, the imaging light beam emitted from the first display light engine is coupled into the waveguide at the coupler and diffracts as a positive second order. The imaging light beam reflects towards the first EPE 1602 inside the waveguide, where the imaging light beam is expanded in one direction and deflected towards the second EPE 1604. The second EPE expands the imaging light beam in a second direction and deflects it towards the coupler 1605. The coupler diffracts the image out of the waveguide and provides the user with enhanced information displayed on the imaging device on one side of their field of view.

[0157] According to an implementation of the present disclosure, when there is a second light display engine in the system, the image from the second display diffracts into a negative second order. However, other implementations are possible, and any negative order can be used.

[0158] The imaging beam from the second display is reflected inside the waveguide towards the third EPE 1603, where the imaging beam is expanded in one direction and deflected towards the fourth EPE 1606. The fourth EPE expands the imaging beam in a second direction and deflects it towards the coupler 1605. The coupler diffracts the image out of the waveguide for the display and provides the user with enhanced information displayed on the imaging device on the other side of their field of view. It should be noted that the first EPE 1602 and the third EPE 1603 have the same pitch dimension. Similarly, the second EPE 1604 and the fourth EPE 1606 have the same pitch dimension.

[0159] So far, the principle has been disclosed as a monochromatic system, where there is only one waveguide per eye.

[0160] According to another embodiment, if a full-color system is desired, more than one waveguide can be used per eye. For example, each color can be dedicated to one waveguide. This results in three waveguides per eye for an RGB system. In this case, the diffraction gratings are designed for each RGB color for the respective waveguide integrated therein.

[0161] The present disclosure also relates to a diffraction grating configured to deflect a beam coupled into a waveguide by a certain deflection angle in a total internal reflection mode, where the grating pitch of the diffraction grating is determined as a function of the deflection angle such that the maximum angular range of the beam remains in the waveguide in the TIR mode after deflection.

[0162] According to the principles disclosed herein, a waveguide including such a diffraction grating is disclosed.

[0163] In a typical imaging system, the optics use refractive and reflective optical components (lenses and mirrors) to transfer an image between conjugate planes. In these systems, the beam size and aperture are defined in the image and pupil planes, and the propagation in the space between these planes is uniform. Waveguide-based optical systems for augmented reality (AR) typically use diffraction gratings as optical components for a series of functions. The main function of these diffraction gratings is to fold or deflect the beam in an efficient and compact manner. As described above, such diffraction gratings are used to expand the pupil.

[0164] Another function is to deflect the image inside the waveguide to change its propagation direction. Among these functions, planar waveguide optics can fold or split the beam, like a mirror, while simultaneously increasing the optical path by performing various reflections (TIR mode) in a high refractive index material. This gives the system compactness.

[0165] A diffraction grating is used to couple an image into a waveguide, where the image further propagates in the TIR mode. The difficulty lies in deflecting the image and still remaining in the TIR mode while matching the optimal shape and range of the incident light beam. For this purpose, it is desirable that the TIR diffraction grating be configured to transmit the maximum possible FoV in another direction.

[0166] According to the principles disclosed herein, a waveguide is designed that deflects an imaging light beam in the TIR mode, thereby avoiding intensity loss and pupil masking for a rectangular-segment light beam defined by horizontal and vertical FoVs (HFoV and VFoV).

[0167] According to the principles disclosed herein, a diffraction grating is designed to deflect an image having HFoV and VFoV. The grating parameters to be determined are the orientation and the grating pitch. The limitation is to deflect an image that is already in the TIR mode, which means that each ray of the image inside the waveguide has its principal polar angle value within a range defined by the critical angle and the grazing angle values. Each ray also has a range of azimuth angle values. Therefore, the diffraction grating is in a conical mount. After deflection by the grating, the polar angle should still be contained between the critical angle and the grazing angle, thus remaining in the TIR mode. The propagation direction of the light beam after this diffraction is oriented towards another direction. The desired characteristics of the diffraction grating are discussed below, which satisfy the above functions in terms of orientation and grating pitch dimensions and maximize the operation for the highest possible field of view.

[0168] According to the present disclosure, an analytical solution is given such that the diffraction grating is designed for a large field of view. A set of equations is provided below to set the diffraction grating, which also gives more insights into the limitations, constraints, and possibilities of the system. The performance in terms of the angular transfer function is thereby fully defined, and this allows avoiding losses of image content and energy during the diffraction process. The precision obtained in the system design also avoids over-specification of the device and then provides the best compactness for a given transmission range.

[0169] Some explanations and mathematical basics are provided in the following description to help understand the principles disclosed herein.

[0170] Conical diffraction of the coupler 。

[0171] Generally speaking, a diffraction grating is analyzed and configured for in-plane diffraction, which means that both the incident ray and the diffracted ray are in the same plane perpendicular to the diffraction grating. However, the rays generated by the light engine used to illuminate the coupler have not only polar deflection but also azimuthal deflection. In the following explanations, the rays will be described in spherical coordinates by their polar angle and azimuth angle, and their directions are normalized.

[0172] The ray before the waveguide and incident on the coupler has coordinates (θ i ,φi ), θ i is the polar angle, and φ i is the azimuthal angle. Generally, the light is in air and diffracted by the coupler grating of the waveguide into the waveguide as (θ d , φ d ). Inside the waveguide, this light needs to be in the TIR mode, which means:

[0173] where n2 is the refractive index of the waveguide, is the grazing limit of the waveguide, and the critical angle. Figure 17 shows the critical ray, the grazing incident ray, and the diffracted ray.

[0174] Figure 18 shows the coordinate system for conical diffraction. In this figure, the projections of the incident wave vector and the diffracted wave vector on the X - Y plane are represented as and There is also a grating vector, which is perpendicular to the grating lines and multiplied by the diffraction order M.

[0175] The normalized and right - hand coordinate system (x, y, z) has a basis the incident wave vector is shown with its spherical angles (θ_i, φ_i). The incident wave vector has a polar angle θ i and an azimuthal angle φ i . Its projection onto the X - Y plane is the vector and mathematically is: The diffracted ray is a combination of diffraction and refraction. The refractive index of the waveguide is n2.

[0176] The wave vector is incident on the grating at the polar angle θ i and the azimuthal angle φ i .

[0177]

[0178] The diffracted wave has a wave vector This wave vector has a polar angle θ d and an azimuthal angle φ d ,

[0179]

[0180] In addition, the grating vector is

[0181]

[0182] where Λ is the grating pitch.

[0183] The conical diffraction equation formula can be applied to the projected wave vector:

[0184]

[0185] And for the out-of-plane component of the diffracted wave vector, the equation is:

[0186]

[0187] where M is the diffraction order, and k xd and k yd are calculated from the previous system of equations to which the conical diffraction equation formula is applied to the projected wave vector. Finally, a set of conical diffraction equations, as follows

[0188]

[0189] where n1 = 1 is the refractive index of the main medium (e.g., air).

[0190] The goal is to calculate the spherical coordinates (φ i as θ i varies from 0 degrees to 90 degrees and φ d varies from 0 degrees to 360 degrees. For coupler analysis, the diffraction grating is along the x-axis, which means φ d = 0. The direction of the diffracted wave vector can be calculated by solving the conical equation for (θ K , φ d , φ d ):

[0191]

[0192]

[0193] Analyze this set of equations in a polar plot, where the radial coordinate is the polar angle and the azimuthal angle is φ, as Figure 19 shown. Angle values are plotted for a system where M = 1, λ = 625 nm, n2 = 1.5 and Λ = 500 nm. The polar coordinates show the incident angles (θ i , φ i ). In Figure 19 , curve 1901 represents the grazing limit, which indicates the angle of incident light diffracted into the waveguide at the grazing angle (75°, in this case). Curve 1902 represents the TIR limit, which indicates the angle of incident light diffracted into the waveguide at the critical angle. Incident light with angles between curve 1901 and 1902 will propagate in the waveguide by total internal reflection.

[0194] Figure 20Shows the diffraction angle in the waveguide. The polar coordinates show the diffraction angle (θ d , φ d ). The curve 2201 represents the grazing angle (here 75°), and the curve 2202 represents the critical angle. The curved dashed line 2203 encloses the angles of the diffracted light in the waveguide. The light ray has an angle within the arc region enclosed by the curves 2201, 2202, and 2203, and this light ray can propagate within the waveguide.

[0195] It can be seen that the diffracted wave vector has a preferred direction. The preferred direction is the x - direction and is in the direction of the grating vector, and as expected, this direction is perpendicular to the grating lines. The polar plot also shows the TIR limit. The diffracted light rays of the isoparametric curves above this TIR limit are in the TIR mode inside the waveguide, while the light rays beyond this value only pass through the waveguide. There is also a grazing limit isoparametric curve at 75 degrees, which becomes the grazing limit because the grazing diffracted light rays above 75 degrees are considered difficult to extract. Such a graph more comprehensively shows the behavior of the coupler for the incident light rays and the situation of the diffracted light rays.

[0196] Dual diffraction mode .

[0197] The inner - coupling grating can also be designed to couple half of the image field into the waveguide propagating in one direction and the other half into the waveguide propagating in a second direction.

[0198] According to another embodiment of the present disclosure, as discussed above, the inner - coupling grating can be configured to couple two images into the waveguide, where one image propagates in one direction in the waveguide and the other image propagates in a second direction in the waveguide. Figure 21 Shows such a double - diffraction mode, where the negative diffraction order is coupled towards the left and the positive diffraction order is coupled towards the right.

[0199] The advantage of such a system is that the two image halves are recombined before reaching the eye pupil and then presented as approximately twice the field of view. In the case where two images are coupled into the waveguide, this dual - mode can also be used to display each of the two images on one side of the field of view.

[0200] The equation that can be used to select the inner - coupling grating pitch size is:

[0201]

[0202] The additional angle that appears here is which is the maximum grazing incidence angle inside the waveguide. Generally, this value is set to The second angle is and this value controls the amount of overlap between the two diffraction modes.

[0203] Orientation and pitch dimensions of the corrugated grating according to the embodiment 。

[0204] For calculating the EPE pitch dimension according to some embodiments, it is assumed that the imaging beam is coupled into the waveguide. A single-mode or dual-mode diffraction grating can be used. In any of the following cases, one direction inside the waveguide is considered to be, for example, on the beam, and the propagation direction of the beam is φ d = 0. Similar reasons can be used for other beams, and the direction of the beam is φ d = π.

[0205] For the propagation direction at φ d = 0, the azimuth angle extends from φ d = -30 to approximately φ d = 30°, while the polar angle extends from the TIR angle to θ d = 75°.

[0206] It is also assumed that the inner coupling grating and the deflection grating are located on the same side of the waveguide, and both are provided with a Cartesian coordinate system with the same orientation. Figure 18 The coordinate system at the TIR inner coupling diffraction grating is shown. The first difference of the deflection grating relative to the inner coupling grating is that the incident wave vector on the deflection grating is and the diffracted wave vector is called

[0207] The second difference is that both its incident wave vector and diffracted wave vector are inside the waveguide, while in the case of the coupler, the incident wave vector is in air. Assume that the unknown grating pitch (to be determined) is Λ e .

[0208] By applying the grating equation, then:

[0209] where

[0210] According to these equations, the value of the polar diffraction angle is calculated by:

[0211] (sinθ e ) 2 = (α × cosφ K - sinθ d × cosφ d ) 2 + (α × sinφ K - sinθ d × sinφ d ) 2 ,

[0212] and since the condition for the coupler diffracted ray is Thus, the range of values of the light diffracted by the deflection grating can be set similarly. The light should all remain in the TIR mode, regardless of its incident direction (θ d , φ d ):

[0213]

[0214] Using two conditions, a set of two three - part equations is provided below, from which the lower e boundary and upper boundary

[0215]

[0216]

[0217] for the pitch Λ

[0218]

[0219]

[0220] can be obtained:

[0221]

[0222]

[0223] where the pitch is within the interval .

[0224] In the above two equations, providing the pitch size, there is a dependence on the azimuth angle φ d . This azimuth angle can vary. The range of values that can be explored is the domain where the upper pitch size is always greater than the lower pitch size. If the azimuth angle is derived from this domain, then there is no pitch size that can satisfy the last equation, because this would result in which is impossible.

[0225] Since decreases as the azimuth angle increases and increases as the azimuth angle value decreases, and since it is desired to handle positive and negative azimuth angles symmetrically, there are a maximum β = max φ and a minimum γ = min φ d for d . Then, the deflection grating can be configured to have the following characteristics:

[0226] · Its maximum acceptance angle is β, which means the device accepts φ for the gratingK The maximum possible image field of view with a specific orientation.

[0227] · No other design can have a larger field of view.

[0228] · The corresponding pitch size to achieve this is unique.

[0229] To find the field of view and pitch size, the following relationship will be solved:

[0230]

[0231] In fact, the maximum and minimum values should be sought as a function of θ d However, similar results for the maximum and minimum values are obtained when seeking the maximum and minimum values as a function of x = sinθ d This transformation is invertible and greatly simplifies the derivative and its solution.

[0232] Depending on the value of φ K - β, the function reaches its minimum value at one of the following three points:

[0233]

[0234]

[0235]

[0236] In a similar manner, it reaches its maximum value at one of the following points:

[0237]

[0238]

[0239]

[0240] where N is the ratio between the sine of the TIR and the grazing angle:

[0241]

[0242] To solve the relationship (1), four different cases will be distinguished between a set of 3 previous equations for the maximum and minimum dimensions of the corrugated grating pitch and according to the value of the orientation φ K of the corrugated grating. According to the embodiments of the present disclosure, these four cases allow the parameters of the TIR diffraction grating to be fully defined to deflect the imaging beam inside the waveguide.

[0243]

[0244]

[0245] and the image is deflected by an angle 2φ K .

[0246] Figure 22 The curve of the angular acceptance is shown in Figure 23 and the optimal spacing dimension is shown in . Each section of the two curves corresponds to the section indicated in the previous table. Figure 22 shows for n = 1.5, λ = 625 nm, M = 2, and for the case of K (in degrees) the vertical field of view Δφ (in degrees) as a function of the grating orientation φ Figure 22 . In , section 1 is represented by the dashed line marker 2201, section 2 is represented by the dashed line marker 2202, section 3 is represented by the dashed line marker 2203, and section 4 is represented by the dashed line marker 2204. Figure 23 shows for the same case as Figure 22 the grating pitch Λ K (in nm) as a function of the grating orientation φ e (in degrees). In Figure 23 , section 1 is represented by the dashed line marker 2301, section 2 is represented by the dashed line marker 2302, section 3 is represented by the dashed line marker 2303, and section 4 is represented by the dashed line marker 2304.

[0247] Four different cases are considered according to the spacing depending on the grating orientation. The acceptance angle of the highest angle is at φ K = 45°. Once the acceptance angle moves away from this value, the angular bandwidth decreases.

[0248] According to an embodiment of the present disclosure, a waveguide is proposed that has a coupler and a grating for deflecting an image by 90° in the field of view in the waveguide, where the grating is configured according to the principle disclosed above.

[0249] According to an embodiment of the present disclosure, a system is proposed that includes a display having a rectangular shape and whose image is added to the waveguide of the system through the coupler of the waveguide. The proposed system allows the transmission of the image generated by the display through the system without being cropped by the angles diffracted from the TIR scheme.

[0250] Before being added to the waveguide, each spherical wave emitted by each pixel at the position (x, y) on the display matrix is transformed by a lens with a normalized focal length of 1 mm into a plane wave direction (θ i , φ i ). It is assumed that the system has a coupler in the double diffraction mode, so that inFigures 24A to 24D represents only half of the display field.

[0251] Such visualization helps to show the maximum horizontal display length that can be used, such as Figure 24A the line 2240 thereon, and the maximum vertical display length such as the line 2241. At Figure 24B on, the horizontal field of view is the maximum θ of the line 2242 (≈25 degrees) i, while the vertical field of view is the maximum θ of the line 2243 (≈±12 degrees) i, A system with a coupler and a corrugated grating has a horizontal FoV of 48.5° and a vertical FoV of 23.7°.

[0252] The aspect ratio of the vertical FoV is problematic, and it is generally desirable for the display to have an aspect ratio of 16:9. This means that only a smaller portion of the horizontal field of view can be used for the ends, and in order to obtain a better vertical FoV, waveguides with a higher refractive index can be used.

[0253] According to an embodiment of the present disclosure, a corrugated diffraction grating configured according to the principles disclosed above can be integrated in Figure 16 the optical system shown. For example, the first and second EPEs of the waveguide can be configured using the four case equations defined in the table according to the principles disclosed above, depending on the deflection angle of the optical system for deflecting the beam.

[0254] Although the content currently considered to be the preferred embodiments of the present invention has been illustrated and described, those skilled in the art will understand that various other modifications can be made, and equivalents can be substituted without departing from the true scope of the present invention. Additionally, many modifications can be made to adapt to the specific circumstances of the teachings of the present invention without departing from the central inventive concept described herein. Furthermore, the embodiments of the present invention may not include all of the features described above. Therefore, the present invention is intended to be limited not to the specific embodiments disclosed, but to include all embodiments falling within the scope of the appended claims.

[0255] When interpreting the description and its related claims, words of the present invention such as "comprising", "including", "combining", "containing", "is" and "having" should be interpreted in a non-exclusive manner, that is, interpreted as allowing the existence of other items or components that are not explicitly defined. References to the singular should also be interpreted as references to the plural, and vice versa.

[0256] Those skilled in the art will readily understand that various parameters disclosed in the description can be modified, and various embodiments disclosed and / or claimed can be combined without departing from the scope of the present invention.

Claims

1. A device, the device comprising: at least one waveguide having an optical coupler; a first display and a second display, the at least first display being configured to generate a first image and the second display being configured to generate a second image; and a lens system configured to direct the first image and the second image onto the optical coupler, wherein the lens system has an optical axis and the first display and the second display are arranged on opposite sides of the optical axis; wherein the optical coupler is configured to couple the first image into the waveguide and the second image into the waveguide using different diffraction orders.

2. The device according to claim 1, wherein the first display and the second display are separated by a central space without a display.

3. The device according to claim 1, wherein the optical coupler is configured to couple the first image into the waveguide using a positive diffraction order and to couple the second image into the waveguide using a negative diffraction order.

4. The device according to claim 1, wherein the optical coupler is configured to couple at least one of the first image and the second image into the waveguide using a diffraction order with an absolute value greater than one.

5. The device according to claim 1, wherein the lens system has an optical axis and the optical axis does not intersect any display of the device.

6. The device according to claim 1, wherein the waveguide further comprises an optical coupler and at least one pupil expander along at least a first optical path from the optical coupler to the optical coupler.

7. The device according to claim 1, wherein the waveguide further comprises an optical coupler and a first pupil expander and a second pupil expander, the first pupil expander and the second pupil expander being along a first optical path from the optical coupler to the optical coupler, the first pupil expander and the second pupil expander being configured to direct the first image to the optical coupler.

8. The device according to claim 7, wherein the waveguide further comprises a third pupil expander and a fourth pupil expander, the third pupil expander and the fourth pupil expander being along a second optical path from the optical coupler to the optical coupler, the third pupil expander and the fourth pupil expander being configured to direct the second image to the optical coupler.

9. The device according to claim 7, wherein the grating pitch Λ of at least one pupil expander in the pupil expander e is determined as follows: o If then φ therein K is half of the deflection angle, where n2 is the refractive index of the waveguide material, is the maximum grazing incidence angle in the waveguide, M is the diffraction order, λ is the wavelength of the light coupled into the waveguide, and Δφ is the maximum angle of the deflected light obtained by ​ o If then Λ e = M × λ × sin(φ K - Δφ / 2), and Δφ = sin -1 (sin(2 × φ K ) - N), o If then and where and Δ = (cosφ K ) 2 - 4×α×(α + sinφ K ), o If then and 10. A method, the method comprising: generating a first image on a first display and a second image on a second display; and using a lens system to direct the first image and the second image onto an optical coupler of a waveguide, wherein the lens system has an optical axis and the first display and the second display are arranged on opposite sides of the optical axis; wherein the optical coupler is configured to couple the first image into the waveguide and the second image into the waveguide using different diffraction orders.

11. The method according to claim 10, further comprising using the coupler to couple the first image into the waveguide using a positive diffraction order and to couple the second image into the waveguide using a negative diffraction order.

12. The method according to claim 10, wherein the coupler is configured to couple at least one of the first image and the second image into the waveguide using a diffraction order with an absolute value higher than one.

13. The method according to claim 10, wherein the lens system has an optical axis, and the optical axis does not intersect any display of the device.

14. The method according to claim 10, wherein the waveguide further comprises an outcoupler, at least a first pupil expander, and at least a second pupil expander, the at least first pupil expander being configured to direct the first image to the outcoupler, and the at least second pupil expander being configured to direct the second image to the outcoupler.

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