JP2015118273A - Ned polarization system for wavelength pass-through - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization system and method for providing uniform color distribution of light emitted from a light source to an eye box in a near eye display (NED).SOLUTION: A polarization system and method uses an optical element including two or more waveguides 140, 140optimized to different colors of the visible light spectrum. The optical element further includes one or more polarization state generators 160, 162 for controlling the polarization of light incident on the waveguides 140, 140to facilitate coupling of light into a matched waveguide 140, 140, and to impede coupling of light into unmatched waveguides 140, 140.

Description

  One embodiment of the present invention relates to a NED polarization system for wavelength passing, for example.

  [0001] A see-through near-to-eye display (NED) unit can be used to display a virtual image that is compounded with a real object in a physical environment. Such NED units include an illumination engine for producing images and optical elements that are partially transmissive and partially reflective. The optical element is transmissive to allow light from the outside to reach the viewer's eyes, and partially reflective to allow light from the illumination engine to reach the viewer's eyes It is a type. The optical element can include a diffractive optical element (DOE) or hologram in a planar waveguide, and can diffract the image from the microdisplay into the user's eyes.

  [0002] In practice, a NED unit may include a stack of multiple waveguides with each waveguide assigned to a wavelength component. In particular, by controlling the orientation of the DOE in the waveguide, the waveguide can be matched or optimized to couple with a particular wavelength component with maximum efficiency. Optimizing different DOEs to different colors in the visible light spectrum allows the NED unit to provide a full color experience.

  [0003] Within a stack of multiple waveguides, wavelength components matched to the distal waveguide in the stack (ie, the waveguide furthest from the illumination engine) pass through the closer waveguide in the stack To do. In many cases, wavelength components directed to the distal waveguide will couple into the closer waveguide instead of passing straight through. This results in a loss of brightness, color non-uniformity reaching the viewer from the NED unit, and a reduction in the quality of the reproduced virtual image.

US Patent Application Publication No. 2012/0105473 US Pat. No. 4,711,512

  One embodiment of the present invention relates to a NED polarization system for wavelength passing, for example.

  [0004] Embodiments of the present technology relate to systems and methods for selectively changing the polarization state of different wavelength bands as the different wavelength bands pass through a waveguide in a NED unit. The DOE on or in the waveguide is sensitive to polarization. By changing the polarization of a wavelength band to a state where the DOE on the waveguide is less sensitive, the wavelength band can pass through the DOE with little or no attenuation. The polarization in the wavelength band is controlled so that light enters the target waveguide through the DOE before entering the waveguide.

  [0005] In one example, the technology relates to a method for presenting an image, the method comprising: (a) projecting light from a light source into an optical element, wherein the light is at least a first wavelength band. And the second wavelength band, the optical element includes at least a first waveguide and a second waveguide, and the first waveguide and the second waveguide each have at least one optical grating to project And (b) a first wavelength band incident on the first waveguide such that the first wavelength band is coupled within the first waveguide to a greater degree than the first wavelength band. Controlling the polarization of the first wavelength band incident on the first waveguide to be different from the other polarizations, and (c) to the extent that the second wavelength band is larger than the second wavelength band. Second coupling to couple in the second waveguide And the second other than the wavelength band polarized light incident on the waveguide and controlling the polarization of a second wavelength band that is incident on the second waveguide differently.

  [0006] In another example, the present technology relates to a method for presenting an image, the method comprising: (a) projecting light from a light source into an optical element, wherein two lights and n The optical element includes between 2 and m waveguides, the i th wavelength band is matched to the j th waveguide, where i = 1 to n, projecting, where j = 1 to m, and (b) passing one or more of the 2 to n wavelength bands through a plurality of polarization state generators. Each polarization state generator is associated with one of the 2 to m waveguides, and the plurality of polarization state generators couple the remaining wavelength bands that pass through the jth waveguide. To the state that facilitates coupling of the i-th wavelength band in the j-th waveguide. Controlling the polarization of one or more wavelength band passing through, and a step of passing.

  [0007] In a further example, the technology relates to an optical element for transmitting light from a light source to an eyebox, the optical element being a first waveguide, wherein the first waveguide is from the light source. A first waveguide comprising at least a first optical grating for receiving light and coupling a first portion of light into the first waveguide; and a second waveguide, A second waveguide, wherein the second waveguide includes at least a second optical grating for receiving light from the light source and for coupling a second portion of light into the second waveguide And a first polarization state generator between the light source and the first waveguide, wherein the first polarization state generator couples the first polarization state into the first waveguide. A first polarization state generator for changing the polarization of the portion, and a second between the first and second diffraction gratings A polarization state generator, wherein the second polarization state generator changes the polarization of the second portion of the light for coupling into the second waveguide; Prepare.

  [0008] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0009] FIG. 2 is a diagram of components of an example embodiment of a system for presenting a virtual environment to one or more users. [0010] FIG. 2 is a perspective view of one embodiment of a head mounted NED unit. [0011] FIG. 2 is a side view of a portion of one embodiment of a head mounted NED unit. [0012] FIG. 2 is an end view of an optical element from a NED unit including a waveguide having a diffraction grating. [0013] FIG. 3 is an enlarged partial view of the structure of a surface relief diffraction grating. [0014] FIG. 6 is a side view of a portion of one embodiment of a head mounted NED unit including an optical element having a plurality of waveguides. [0015] FIG. 5 is a diagram of an incident surface of light incident on a diffraction grating. [0016] FIG. 6 is an end view of a first embodiment of imaging optics from a NED unit that includes a plurality of waveguides and a polarization state generator for changing the polarization of the wavelength band as the wavelength band enters the waveguide. . [0017] FIG. 6 is an end view of a second embodiment of imaging optics from a NED unit that includes a plurality of waveguides and a polarization state generator for changing the polarization of the wavelength band as the wavelength band enters the waveguide. . [0018] FIG. 9 is a flowchart of the operation of the imaging optics of the first embodiment shown in FIG. [0019] FIG. 10 is a flowchart of the operation of the imaging optics of the second embodiment shown in FIG. [0020] FIG. 9 is an end view of a third embodiment of imaging optics from a NED unit including a plurality of waveguides and a polarization state generator for changing the polarization of the wavelength band as the wavelength band enters the waveguide. . [0021] In an end view of a fourth embodiment of imaging optics from a NED unit comprising a plurality of waveguides and a polarization state generator for changing the polarization of the wavelength band as the wavelength band enters and exits the waveguide. is there. [0022] FIG. 6 is an end view illustrating a wavelength band traveling through a pair of waveguides that do not control polarization. [0023] FIG. 7 is an end view illustrating a wavelength band traveling through a pair of waveguides with controlled polarization in accordance with an embodiment of the present technology. [0024] FIG. 16 is a graph showing the coupling efficiency in the wavelength band of FIGS. 14 and 15.

  [0025] Overall, embodiments of the present technology related to imaging optics for selectively changing the polarization state of different wavelength bands when the wavelength bands pass through a waveguide in a NED unit are shown in FIGS. 16 will be described herein with reference to FIG. The DOE on the waveguide is sensitive to the polarization of light. Thus, by selectively controlling the polarization of the wavelength band entering the DOE on the waveguide, the wavelength band matched to the waveguide can be coupled through the DOE with high efficiency. Unmatched wavelength bands can pass through the DOE and waveguide with little or no effect. While examples using DOE are described herein, it is understood that the waveguide can include a DOE, a hologram, a surface relief grating, or another type of periodic structure in an optical element. These structures are sometimes referred to herein as “optical gratings”.

  [0026] In the embodiments described below, the NED unit may be a head mounted display unit used in a mixed reality system. However, it is understood that the embodiments of the NED unit and the imaging optics contained therein can be used in a variety of other optical applications, such as in optical couplers and other light modulation devices. The figures are provided to understand the present technology and may not be drawn to scale.

  FIG. 1 illustrates an example of a NED unit 2 as a head mounted display used in the mixed reality system 10. The NED unit may be worn as eyeglasses including a lens, which is somewhat transmissive so that the user can see a real object 27 in the user's field of view (FOV) through the display element. . The NED unit 2 also provides the ability to project the virtual image 21 into the user's FOV so that the virtual image can still appear alongside the real object. Although not critical to the technology, the mixed reality system can automatically track where the user is looking, so that the system inserts a virtual image where in the user's FOV It is possible to decide what to do. Once the system knows where to project the virtual image, the image is projected using the display element.

  [0028] FIG. 1 shows a number of users 18a, 18b and 18c, each wearing a head-mounted NED unit 2. The head-mounted NED unit 2, which is in the form of glasses in one embodiment, is mounted on the user's head so that the user can see through the display, so that the space in front of the user is It is possible to see the actual direct sight. Further details of the head mounted NED unit 2 are given below.

  [0029] The NED unit 2 can provide signals to and receive signals from the processing unit 4 and the hub computing device 12. NED unit 2, processing unit 4 and hub computing device 12 determine each user 18's FOV what virtual image should be presented in that FOV and how this should be presented. Can work together. The hub computing device 12 further includes a capture device 20 for capturing image data from a portion of the scene in the FOV of the capture device. The hub computing device 12 can be further connected to an audiovisual device 16 and a speaker 25, which can provide game or application video and sound. Details regarding the processing unit 4, the hub computing device 12, the capture device 20, the audiovisual device 16, and the speaker 25 are described in, for example, “Low-Latency Fusion of Virtual and Real Content” published on May 3, 2012 (virtual content and real content). US Patent Application Publication No. 2012/0105473, entitled “Low Latency Synthesis”), which is hereby incorporated by reference herein in its entirety.

  [0030] FIGS. 2 and 3 show a perspective view and a side view of the head-mounted NED unit 2. FIG. FIG. 3 shows the right side of the head mounted NED unit 2 that includes a portion of the device having the temple 102 and the nose bridge 104. A part of the frame of the head-mounted NED unit 2 will surround the display (including one or more lenses). The display includes a light guide optical element 115, a see-through lens 116 and a see-through lens 118. In one embodiment, the light guide optical element 115 is aligned after the see-through lens 116 and the see-through lens 118 is aligned after the light guide optical element 115. See-through lenses 116 and 118 are standard lenses used in eyeglasses and can be made to any prescription (including no prescription). The light guide optical element 115 transmits artificial light to the eye. Further details of the light guide optical element 115 are given below.

  [0031] Inside the vine 102 or inside the vine 102 is an image source, which (in embodiments) lightguides the image from the microdisplay 120 and the microdisplay 120 for projecting a virtual image. It includes an illumination engine such as a lens 122 for directing to the optical element 115. In one embodiment, lens 122 is a collimating lens. The micro display 120 projects an image through the lens 122.

  [0032] There are various image generation techniques that can be used to implement the microdisplay 120. For example, the microdisplay 120 can be implemented when using transmissive projection technology, where the light source is modulated by an optically active material backlit with white light. These technologies are usually implemented using LCD-type displays with a powerful backlight and high light energy density. The microdisplay 120 can also be implemented using reflective technology, for which external light is reflected and modulated by the optically active material. Illumination is front illuminated by either a white light source or an RGB light source, depending on the technology. Digital Light Processing (DLP), Liquid Crystal on Silicon (LCOS) and Qualcomm, Inc. Mirasol® display technology from is an example of a reflective technology that is efficient because most of the energy is reflected far away from the modulated structure and can be used in current systems is there. In addition, the microdisplay 120 can be implemented using emissive technology where light is generated by the display. For example, Microvision, Inc. The PicoP (TM) display engine from the laser signal using micromirror steering either emits light directly onto the very small screen functioning as a transmissive element or into the eye (eg laser) Release.

  [0033] A light guide optical element (also referred to only as an optical element) 115 can transmit light from the microdisplay 120 to the eyebox 130. The eye box 130 is a two-dimensional area that is located in front of the user's eye 132 wearing the head-mounted NED unit 2 and through which light passes through the optical element 115. The optical element 115 also allows light from the front of the head mounted NED unit 2 to be transmitted through the light guiding optical element 115 to the eye box 130 as depicted by the arrow 142. This allows the user to see the actual direct view of the space in front of the head mounted NED unit 2 in addition to receiving a virtual image from the microdisplay 120.

  FIG. 3 shows half of the head mounted NED unit 2. The entire head-mounted display device can include another optical element 115, another microdisplay 120, and another lens 122. When the head-mounted NED unit 2 has two optical elements 115, each eye has its own micro display capable of displaying the same image in both eyes or a different image in the two eyes. 120 can be included. In another embodiment, there may be one optical element 115 that reflects light from one microdisplay 120 to both eyes.

  [0035] Further details of the light guide optics 115 will now be described with reference to FIGS. In general, optical element 115 includes two or more waveguides stacked on top of each other to form an optical column. One such waveguide 140 is shown in FIG. Although waveguide 140 may be formed from a thin flat glass sheet, in further embodiments it may be formed from plastic or other materials. The waveguide 140 can include two or more diffraction gratings, including an entrance diffraction grating 144 that couples the light beam into the waveguide 140 and an exit diffraction grating 148 that diffracts the light beam out of the waveguide 140. Including. The gratings 144 and 148 are shown as transmissive gratings attached to the lower surface 150a of the substrate 150 or within the lower surface. A reflective grating attached to the opposite surface of the substrate 150 may be used in further embodiments.

[0036] FIG. 4 shows total internal reflection of a wavelength band, λ ₁ , coupled into and out of waveguide 140. As used herein, a wavelength band may be composed of, for example, one or more wavelengths from the visible light spectrum. The illustration of FIG. 4 is a simplified diagram of a single wavelength band in a system where there are no second and higher diffraction orders. Although not shown in FIG. 4, the optical element 115 may further include a polarization state generator sandwiched in front of and between the waveguides as described below.

[0037] The wavelength band λ ₁ from the microdisplay 120 is collimated through the lens 122 and coupled into the substrate 150 by the entrance grating 144 at an incident angle θ ₁ . Inlet grating 144, changing the direction of the wavelength band to the diffraction angle theta _2. The refractive index n ₂ , the incident angle θ ₁ , and the diffraction angle θ ₂ are determined so that the wavelength band λ ₁ causes total internal reflection in the substrate 150. Wavelength band λ ₁ reflects off the surface of substrate 150 until it hits exit diffraction grating 148, where wavelength band λ ₁ diffracts out of substrate 150 toward eye box 130. Further details of waveguides, such as waveguide 140, are disclosed, for example, in US Pat. No. 4,711,512 entitled “Compact Head-Up Display” issued December 8, 1987. This patent is hereby incorporated by reference in its entirety.

  [0038] FIG. 5 is an enlarged partial view showing an example of a surface relief grating 154 that forms part of a transmissive diffraction grating such as diffraction grating 144 and / or 148 (FIG. 5 is into substrate 150). A diffraction grating 144 that diffracts light is shown). The grating 154 can have an inclined profile with a period, p, but the grating may have other profiles such as squares and saw teeth in further embodiments. As noted, the gratings 144, 148 may be reflective in further embodiments.

[0039] The waveguide may be optimized or matched to a specific wavelength band. This relationship can be determined according to the lattice equation:
mλ = p (n ₁ sin θ ₁ + n ₂ sin θ ₂ ) (1)
here,
m = diffraction order,
λ = wavelength band suitable for waveguide / diffraction grating,
p = lattice period,
n ₁ = refractive index of the incident medium,
n ₂ = refractive index of waveguide 140,
θ ₁ = incident angle,
θ ₂ = Diffraction angle.

[0040] By changing parameters such as the grating period p and the refractive index n _{2 of the} substrate 150, a particular waveguide 140, including the diffraction gratings 144, 148, can be matched to a particular wavelength band. . That is, a specific wavelength band can be coupled into a matched waveguide 140 with higher coupling efficiency than other wavelength bands. Moreover, exact coupled wave theory (RCWT) can be used to optimize the profile parameters of the grating 154 (FIG. 5), angular bandwidth, diffraction efficiency and polarization (described below). The waveguide performance such as can be improved.

FIG. 4 illustrates one waveguide 140 for a particular wavelength band through diffraction gratings 144, 148. In embodiments of the present technology, the optical element 115 may include two or more waveguides 140 as described with respect to FIG. 4 layered together in an optical column. Each such waveguide 140 within the optical element 115 can be matched to a different wavelength band. In the example shown in FIG. 6, there is a mutual four such superimposed on the layer to a waveguide 140 _{1-140 4.} Although providing more than four layers may not be practical, it can be imagined that an optical element can contain more than four layers. Each can be optimized for different wavelength (s) of light, for example, violet light at a wavelength of about 400 nm, indigo light at about 445 nm, blue light at about 475 nm, about It includes green light at 510 nm, yellow light at about 570 nm, orange light at about 590 nm, and / or red light at about 650 nm.

[0042] waveguide ₁₄₀ 1-140 ₄ can be provided in any order, one or more of the waveguide ₁₄₀ 1-140 ₄ aligned with wavelengths other than those mentioned above May be. In the example, one waveguide 140 can be matched to a wavelength band covering different colored wavelengths of the visible light spectrum.

[0043] In a layered waveguide stack, the emitted wavelength band matched to the distal waveguide in the stack passes through all of the nearby waveguides in the stack. For example, in the embodiment of FIG. 6, the wavelength band lambda ₁ from the micro display 120 matched to the most distal of the waveguide 140 ₁ passes closer waveguide ₁₄₀ 2-140 _4. As described in the Background section, one problem associated with conventional stacks of layered waveguides is that the wavelength band intended to couple into the distal waveguide is closer. It is also partly coupled into the waveguide, thereby degrading the color of the image reaching the eyebox 130.

[0044] It is a characteristic of the diffraction grating in the waveguide 140 that it is sensitive to polarization in the wavelength band that the diffraction grating passes through. Thus, the wavelength band of the first polarization can be coupled with the one or more waveguide layers through which it passes, but the same wavelength band with a second polarization different from the first polarization is It can pass through one or more waveguide layers without ringing. According to aspects of the present technique, the polarization of the light wavelength band is controlled to pass through other mismatched waveguides while coupling into the matched waveguide. Thus, in the example of FIG. 6 wavelength band lambda ₁ is aligned to the coupling to the waveguide 140 in _1, the polarization waveguide 140 ₂ - prior to coupling the waveguide 140 within ₁ 140 ₄ is controlled.

[0045] Referring now to FIG. 7, the polarization of light incident on the diffraction grating 144, 148 may be defined by the orientation of the electric and magnetic fields related to the incident plane P _i. The plane P _i can be defined by the propagation vector from the illumination source, PV, and the grid normal vector, GN. Vector PV is a projection of the k-vector of light on waveguides 144 and 148. The lattice vector GV is a vector in the plane of the lattices 144 and 148 that defines the direction of the lattice lines. As used herein, the term “state E” refers to a state of polarization where the electric field component in the wavelength band along the lattice vector, GV, is zero. As used herein, the term “state M” refers to a state of polarization where the magnetic field component along the lattice vector, GV, is zero.

  [0046] In the example described below, the polarization of the wavelength band incident on the gratings in the various waveguides 140 is controlled to change between state E and state M. In an embodiment, the polarized wavelength band of state M incident on the diffraction grating passes through the diffraction grating, but the polarized wavelength band of state E incident on the diffraction grating is in the waveguide including the diffraction grating. Coupling to

  [0047] The following example describes the current technology with respect to controlling the state E and state M of polarized light, but in the first polarization state, the wavelength band passes through a waveguide. However, it will be appreciated that in the second polarization state, other polarization states may be used such that the wavelength band couples to the waveguide. Examples of additional first and second polarization states are left polarization and right polarization of wavelengths that pass through the waveguide 140. In addition, although the following describes polarized light, which is one of two states, it is envisioned that polarized light can occupy more than two states. In such an embodiment, at least one state couples in the waveguide, while at least one other state passes without coupling.

[0048] Example embodiments are described herein with reference to FIGS. 8-9, which illustrate an optical element 115 comprised of two waveguides 140. FIG. FIG. 12, described below, illustrates an example embodiment in which the optical element 115 can be comprised of n waveguides, where n can be a different number of waveguides. . A first embodiment will now be described with reference to the flowcharts of FIGS. Figure 8 shows a pair of waveguides 140 ₁ and 140 _2. Separate wavelength bands of light λ ₁ and λ ₂ are emitted from microdisplay 120 and collimated through lens 122 in step 300. Waveguide, light from the microdisplay 120 is disposed so as to proceed to the first and to the waveguide 140 in ₂ then waveguide 140 in _1.

[0049] Waveguides 140 ₁ and 140 ₂ can be matched to _two different wavelength bands λ ₁ and λ ₂ emitted from microdisplay 120, respectively. As an example, waveguide 140 ₁ can be adjusted to the red light, the waveguide 140 ₂ can be adjusted to the blue and green light. It is understood that the waveguides 140 ₁ and 140 ₂ may be matched to other wavelength bands of one or more wavelengths of visible light in further embodiments.

[0050] The light emitted from the microdisplay 120 can be polarized into unpolarized light or state E in this embodiment. Prior to entering the first waveguide 140 ₂ , both wavelength bands λ ₁ and λ ₂ pass through a polarization state generator (PSG) 160. PSG 160 (also multiple PSGs described below) shifts the phase of a particular wavelength band between two perpendicular polarization states while leaving other wavelengths of light unaffected. It may be a known polarization state generator such as a wave plate or a polarization retarder, for example.

[0051] PSG160 may be formed as a thin plate before the birefringent material capable of being affixed to optical element 115 of the diffraction grating 144 of the substrate 150 of the waveguide 140 in _2. If the diffraction grating is a transmission type, PSG160 before the diffraction grating 144 of the waveguide 140 _2, it is possible to be incorporated into the waveguide 140 _{and second} substrate 150. The PSG 160 (also a plurality of PSGs described below) can have the same footprint as the waveguide 140, but in embodiments can be small or large. If small, the PSG 160 can overlie at least the entrance grating 144. The PSG 160 may be formed from, for example, a polymer film retarder, a birefringent crystal retarder, a liquid crystal retarder, or a combination thereof. The PSG 160 may be formed from another material in further embodiments. PSG 160 (similarly, multiple PSGs described below) can be obtained from, for example, Meadowlark Optics, Inc. , Frederick, CO, USA.

[0052] The PSG 160 may be configured to change the polarization of the wavelength band λ ₁ from state E to state M at step 304. The PSG 160 can leave the intensity and direction of the wavelength band λ ₁ unaffected. PSG160 is still wavelength band lambda ₂ of the polarization may be left without the strength and direction influenced, to allow the wavelength band lambda ₂ straight pass without or altered without substantial change.

[0053] As noted above, in embodiments, individual wavelengths from the microdisplay 120 may not be polarized. In such an embodiment, PSG 160 can modulate wavelength band λ ₁ to state M as described above, and a second PSG (not shown) modulates wavelength band λ ₂ to state E. can do.

[0054] As described above, polarized light in state E can be coupled into waveguide 140, where polarized light in state M does not couple (or is less). To some extent). Thus, after a state change via PSG160, the wavelength band lambda ₂ polarized state E is coupled with the waveguide 140 within ₂ at step 308, the wavelength band lambda ₂ taken here, eye box It is transmitted to 130 outside the waveguide 140 _2.

[0055] When polarized to state M, the wavelength band λ ₁ passes substantially or completely through the waveguide 140 ₁ without coupling or attenuation. To enable wavelength band lambda ₁ of the coupling in the waveguide 140 within ₁ wavelength band lambda _1, before entering into after exiting the waveguide 140 ₁ and waveguide 140 _2, the second The PSG 162 passes through.

[0056] The PSG 162 may be formed of the same material as the PSG 160, but is configured to modulate the polarization of the wavelength band λ ₁ from state M to state E in step 310. PSG162 is the optical element 115, is capable of being formed sandwiched between the waveguide 140 ₁ and 140 _2. Alternatively, PSG162 may be formed before or waveguide 140 diffraction grating 144 in the _first substrate 150 after the diffraction grating 144 in the substrate 150 of the waveguide 140 _2.

[0057] After phase change through PSG 162, wavelength band λ ₁ can be coupled into waveguide 140 ₁ at step 314, where wavelength band λ ₁ is captured as described above. which is transmitted to the eye box 130 outside the waveguide 140 _1. In this way, different wavelengths of light can be transmitted from the microdisplay 120 using the waveguide 140, while maintaining the color quality of the wavelengths transmitted through the optical element 115. Can do.

[0058] Further embodiments will now be described with reference to the flowcharts of FIGS. Individual wavelengths of light are emitted from the microdisplay 120 and collimated through the lens 122 in step 320. Collimated light is then first enters into waveguide 140 _2. Waveguides 140 ₂ and 140 ₁ can be optimized for _two different wavelength bands, λ ₁ and λ ₂ , corresponding to the individual wavelengths emitted from microdisplay 120 as described above. It is. All wavelengths of light emitted from the microdisplay 120 can be unpolarized or polarized to state M in this embodiment. Prior to entering the first waveguide 140 ₂ , both wavelength bands λ ₁ and λ ₂ pass through the PSG 166.

[0059] PSG 166 may be formed of the same material and size as PSG 160, but is configured to change the polarization of wavelength band λ ₂ from state M to state E at step 324. The PSG 166 can leave the intensity and direction of the wavelength band λ ₂ unaffected. PSG166 also wavelength band lambda ₁ of the polarization may be left without the strength and direction affected, makes it possible to straight pass unchanged wavelength band lambda _1.

[0060] If the light from the microdisplay 120 is not polarized, the PSG 166 can modulate the wavelength band λ ₂ to state E as described above, and a second PSG (not shown). Can modulate the wavelength band λ ₁ to state M.

[0061] PSG166 after state changes through the wavelength band lambda ₂ polarized state E is coupled in the waveguide 140 _2, here taken as the wavelength band lambda ₂ has been described above, It is transmitted to the rear to the eye box 130 outside the waveguide 140 _2.

[0062] When polarized to state M, wavelength band λ ₁ passes substantially or completely through waveguide 140 ₁ without coupling or attenuation. To enable wavelength band lambda ₁ of the coupling in the waveguide 140 within ₁ wavelength band lambda _1, before entering into after exiting the waveguide 140 ₁ and waveguide 140 _2, the second Pass through PSG168. PSG 168 may be the same as PSG 162 in FIG. 8, and wavelength band λ ₁ may still be modulated from state M to state E at step 334. The wavelength band λ ₁ can then be coupled into the waveguide 140 ₁ at step 338 where the wavelength band λ ₁ is captured as described above and into the eye box 130 the waveguide 140. ₁ is transmitted backward to the outside.

  [0063] Using a PSG system sandwiched in front of and between waveguides, multiple wavelength bands can be polarized as described above, resulting in mismatched leads. It passes through the waveguide and couples all or nearly all the intensity in the matched waveguide. The PSG system can cause the polarization in the wavelength band approaching the mismatched waveguide to already be in state M, thus passing through the mismatched waveguide without affecting the wavelength band. . Alternatively, the polarization in the wavelength band approaching the mismatched waveguide may be in the state E state, so that the wavelength band passes through the PSG for modulation to state M, where the wavelength band is then Can pass through unmatched waveguides without being affected. That wavelength band can then remain in state M until it reaches the matched waveguide, at which point the wavelength band is PSG to cause state E to modulate the wavelength band. So that the wavelength band can be coupled into the matching waveguide.

  [0064] An example including n wavelength bands and waveguides is shown and described herein in connection with FIG. Although the example of FIG. 13 shows wavelength bands and waveguides where n is 4 or greater, further examples can also include three wavelength bands and waveguides.

[0065] The individual wavelength bands λ ₁ , λ ₂ , λ ₃ ,. . . And λ _n are emitted from the microdisplay 120 and collimated through the lens 122. In one example, all wavelengths of light from microdisplay 120 can be polarized to state M. In this case, this embodiment includes a PSG 170 ₁ as described above configured to modulate the polarization of λ ₁ to state E while leaving the remaining wavelength band polarized to state M. be able to. In further embodiments, the wavelength band emitted from the microdisplay 120 may have another polarization or may not be polarized. In these further embodiments, one or more PSGs may be installed in front of (or integrated into) the waveguide 140 ₁ so that it passes through the one or more PSGs. Then, after entering the entrance diffraction grating 144 of the waveguide 140 ₁ , the wavelength band λ ₁ is polarized to the state E, and the wavelength bands λ ₂ to λ _n are polarized to the state M.

[0066] The polarized wavelength band λ ₁ in state E can then be coupled into the waveguide 140 ₁ , where the wavelength band λ ₁ is captured as described above and the eyebox to 130 out of the waveguide 140 ₁ is transmitted to the rear. When polarized to state M, the remaining wavelength bands λ ₂ to λ _n pass through the waveguide 140 ₁ substantially or completely without coupling or attenuation.

[0067] Next, the remaining wavelength bands λ ₂ to λ _n pass through the second PSG 170 ₂ , which modulates the wavelength band λ ₂ to state E, while the remaining wavelength bands λ ₃ to λ Leave _n substantially or completely unaffected.

[0068] wavelength band lambda ₂ polarized state E is then to the waveguide 140 in ₂ and can be coupled, the wavelength band lambda ₂ is taken as described above herein, eye box 130 is transmitted to the rear out of the waveguide 140 ₂ to. When polarized state M, the lambda _n from the remaining wavelength band lambda _3, substantially or completely through the waveguide 140 ₂ without coupling or damping.

[0069] This process is repeated for each of the remaining waveguides. Each wavelength band can be polarized to pass through a mismatched waveguide until it reaches the matched waveguide, at which point the wavelength band is matched to the matched waveguide It can be polarized to couple into. The last wavelength band λ _n passes through all of the waveguides 140 ₁ to 140 _n−1 until reaching the waveguide 140 _n . Prior to passing through waveguide 140 _n , wavelength band λ _n passes through PSG 170 _n and is polarized to a state where it can then be coupled into waveguide 140 _n .

  [0070] Other configurations of PSG can be provided so that a wavelength band suitable for one waveguide is polarized to couple with that waveguide while all other wavelengths are It will be appreciated that the band is polarized to pass through its waveguide. In this way, different wavelengths of light can be transmitted through the optical element 115 using the waveguide and the PSG described above, while all transmitted through the optical element 115. Maintain the color quality of the wavelength.

  [0071] After coupling out in the distal waveguide, the wavelength band passes through each of the closer waveguides on the way to the eyebox 130. As described above in connection with FIG. 4, each waveguide 140 includes an exit grating (148) that couples light already in the waveguide out of the waveguide. The exit grating 148 may allow the incident wavelength band returning from the more distal waveguide to pass almost or completely straight without coupling. However, it may happen that light rays from a more distal waveguide at least partially couple into the closer waveguide on its way to the eyebox 130.

[0072] Thus, in a further embodiment, in addition to providing a PSG over the entrance grating 144 to control the coupling of light from the microdisplay 120 in each waveguide, the PSG is also , May be provided over the exit diffraction grating 148. The exit grating PSG prevents light from the distal waveguide from coupling into the closer waveguide as it travels to the eyebox 130. One such example is shown in FIG. In this example, the wavelength bands λ ₁ to λ _n are coupled to their matched waveguides while passing through unmatched waveguides as described above. Upon exiting the wavelength-matched waveguide, its polarization can be switched again, eg, from state E to state M by one of PSG 180 ₁ to 180 _n , so that the wavelength band is It then passes through the closer waveguide without coupling. In this example, the last PSG before the eye box, PSG 180 ₁ , transmits the wavelength bands λ ₁ to λ _n in various ways as desired for presentation to the user's eye 132 via the eye box 130. It can be polarized.

  [0073] In some of the embodiments described above, the polarized wavelength of state E has been described to couple in their matched waveguides, while polarized in state M Wavelengths pass through unmatched waveguides without being weakened. However, instead of full coupling / full pass, the polarized wavelengths of both states E and M will partially couple into the waveguide when these wavelengths enter the waveguide. There is. However, through the use of PSG as explained above, the coupling wavelength coupling efficiency of state E can be increased compared to the coupling wavelength coupling polarization of state M. is there.

[0074] An example of this is described in FIGS. 14 and 15, respectively, shows an end view of the wavelength bands λ incident on a pair of waveguides 140 ₁ and 140 _2. The wavelength band lambda, but is aligned to the waveguide 140 _2, through first waveguide 140 _1. In FIG. 15, the polarization in the wavelength band is controlled using PSG 160, and FIG. 14 and FIG. 15 are the same except that PSG is not used in FIG.

In [0075] Figure 14, incoming wavelength band is incident on the diffraction grating 144 in the waveguide 140 ₁ does not match with the incident angle theta _1. The uncontrolled wavelength band can have the polarization of state E so that the portion λ _1c is coupled into the waveguide 140 ₁ . The second part λ _1m is diffracted by second order diffraction (there can be further grating order diffraction, not shown). The remaining portion λ _1t is transmitted through the waveguide 140 ₁ and enters the matched waveguide 140 ₂ . Since a relatively large component of the wavelength band lambda-coupled with the waveguide 140 within _1, a small portion lambda _2c is left to coupling to waveguide 140 _2.

[0076] Conversely, in FIG. 15, the same wavelength band lambda, having (e.g., PSG by not shown) polarization which is set to a state M before entering the waveguide 140 _1. As shown, a relatively small portion λ _1c of the wavelength band couples into the waveguide 140 ₁ . Therefore, the portion λ _1t transmitted through the waveguide 140 ₁ is large. Between the waveguides 140 ₁ and 140 ₂ , the polarization in the wavelength band is changed from the state M to the state E by the PSG 160. Polarized wavelength lambda of the state E is, as a result, have a relatively large portion lambda _2c coupling with suits waveguide 140 within _2.

[0077] FIG. 16 is a graph of coupling efficiency versus incident incoupling angle. Coupling efficiency is defined here as the ratio (expressed as a number between 0 and 1) of the intensity of the wavelength coupled in the waveguide that matches the intensity of the wavelength band emitted from the light source. . This example uses the red light (650 nm) as the wavelength band shown in FIGS. 14 and 15 that matches the waveguide 140 _2. The graph also shows the second wavelength band of green light (540 nm). The green wavelength band is not shown in FIGS. 14 and 15 but is matched to and coupled in the _first waveguide 1401. Lattice interval for the diffraction grating 144 of the _first waveguide 140 for ₁ is 450 nm, the grating spacing of the diffraction grating 144 of the _second waveguide 140 for ₂ is 550 nm.

  [0078] As seen in the graph of FIG. 16, the green wavelength band curve 184 couples into the matched waveguide without requiring the green wavelength to travel through any other waveguide. Thanks to the fact that it does, it shows the highest coupling efficiency over 90%. As described above, the red wavelength band curve 186 of FIG. 15 coupled to a waveguide using polarization controlled in accordance with the present technology shows a coupling efficiency of about 88%. The red wavelength band curve 188 of FIG. 14 without controlled polarization shows a lower coupling efficiency, less than 70%. Thus, as described above, the PSG of the present technology can prevent light from coupling into mismatched waveguides and facilitate light coupling into matched waveguides.

  [0079] Although the subject matter has been described in language specific to structural features and / or methodological acts, the subject matter defined in the claims below is specifically described by the specific features or acts described above. It is understood that it is not necessarily limited to. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. The scope of the present invention is defined by the appended claims.

2 Head-mounted NED unit 4 Processing unit 10 Mixed reality system 12 Hub computing device 16 Audiovisual device 18 User 20 Capture device 21 Virtual image 25 Speaker 27 Real object 102 Vine 104 Nose bridge 115 Optical element 116 See-through lens 118 See-through lens 120 Micro display 122 Lens 130 Eye box 132 Eye 140 Waveguide 142 Arrow 144 Entrance diffraction grating 148 Exit diffraction grating 154 Surface relief grating 160 PSG
162 PSG
166 PSG
168 PSG
170 PSG
180 PSG
184 Curve of green wavelength band 186 Curve of red wavelength band of FIG. 15 188 Curve of red wavelength band of FIG. 14 n ₁ Refractive index of incident medium n ₂ Refractive index of waveguide p Lattice period λ ₁ wavelength band λ ₂ wavelength band θ ₁ the incident angle theta ₂ diffraction angle GN grating vertical vector GV grating vector P _i incident surface PV propagation vector

Claims (10)

A method for presenting an image,
(A) projecting light from a light source into an optical element, the light comprising at least a first wavelength band and a second wavelength band, wherein the optical element Including at least a first waveguide and a second waveguide, wherein the first waveguide and the second waveguide each have at least one optical grating; ,
(B) Incident on the first waveguide such that the first wavelength band is coupled within the first waveguide to a greater extent than other than the first wavelength band. Controlling polarization of the first wavelength band incident on the first waveguide different from polarization other than the first wavelength band;
(C) the second wavelength incident on the second waveguide so that the second wavelength band is coupled in the second waveguide to a degree greater than that other than the second wavelength band. Controlling the polarization of the second wavelength band incident on the second waveguide to be different from the polarization other than the wavelength band.   The step of controlling the polarization of the first wavelength band to be different from the polarization of the first wavelength band is different from the first wavelength band incident on the first waveguide. The method of claim 1, comprising changing the polarization of the first wavelength band incident on the first waveguide while maintaining polarization.   The step of controlling the polarization of the first wavelength band to be different from the polarization other than the first wavelength band on the first waveguide from a first state to a second state; Changing the polarization other than the incident first wavelength band, wherein the first wavelength band is greater than the first state to a greater extent in the second state. The method of claim 1, comprising coupling and modifying in the waveguide.   The step of controlling the polarization of the first wavelength band to be different from the polarization other than the first wavelength band on the first waveguide from a first state to a second state; The method of claim 1, comprising changing the polarization other than the incident first wavelength band.   The step of controlling the polarization of the second wavelength band to be different from the polarization other than the second wavelength band, wherein the step of controlling the polarization of the second wave from the second state to the first state; The method according to claim 4, comprising changing the second wavelength band incident on the road. A method for presenting an image, comprising:
(A) projecting light from a light source into an optical element, wherein the light includes a wavelength band between 2 and n, and the optical element has a waveguide between 2 and m. Projecting, wherein the i th wavelength band is matched to the j th waveguide, where i = 1 to n and j = 1 to m;
(B) passing one or more of the two to n wavelength bands through a plurality of polarization state generators, wherein each polarization state generator is A plurality of polarization state generators associated with a waveguide of the 2 to m waveguides, wherein the plurality of polarization state generators are coupled to the i th wavelength band in the j th waveguide. Controls the polarization of the one or more wavelength bands passing to facilitate the ring while preventing coupling of the remaining wavelength band through the jth waveguide ( impeding) and passing.   After passing through a first polarization state generator installed between the light source and the first waveguide, the first wavelength band is a polarization state 1 (polarization state 1). An electric vector is perpendicular to a grating vector and the wavelength bands 2 to n are polarization states 2, where an electrical vector is perpendicular to the electrical vector in the first band; The method of claim 6.   The nth wavelength band is set in a state in which the polarization of the nth wavelength band is prevented from being coupled in the m-1 waveguides and passes through the m-1 waveguides. The nth wavelength band is passed through, and the polarization of the nth wavelength band is set to allow the coupling of the nth wavelength band in the mth waveguide. The method of claim 6, wherein An optical element for transmitting light from a light source to an eye box,
A first waveguide, wherein the first waveguide receives at least light from the light source and couples a first portion of the light into the first waveguide. A first waveguide comprising:
A second waveguide, wherein the second waveguide receives at least a second light to receive light from the light source and to couple a second portion of the light into the second waveguide. A second waveguide comprising:
A first polarization state generator between the light source and the first waveguide, wherein the first polarization state generator couples the light into the first waveguide for coupling. A first polarization state generator that changes the polarization of the one part;
A second polarization state generator between a first diffraction grating and a second diffraction grating, wherein the second polarization state generator emits light for coupling into the second waveguide. And a second polarization state generator for changing the polarization of the second portion of the optical element.   The first waveguide and the second waveguide and the polarization state generator are planar members formed in a near-eye display for generating a mixed reality environment; The optical element according to claim 9.

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