Optical waveguide structure and near-eye display module

Abstract

The application discloses an optical waveguide structure and a near-eye display module, and relates to the technical field of optical waveguide structures. The optical waveguide structure comprises: a light splitting waveguide and an imaging waveguide which are arranged in parallel; the imaging waveguide comprises a first coupling-in area and a second coupling-in area which are respectively located at two ends of the imaging waveguide; the light splitting waveguide is used for splitting coupled-in light into two light beams, one of which is coupled in from the first coupling-in area of the imaging waveguide, and the other of which is coupled in from the second coupling-in area of the imaging waveguide to which the other light beam propagates through the light splitting waveguide, so that two light beams which propagate in opposite directions and have different propagation angles exist in the imaging waveguide, thereby relieving the technical problems of pupil discontinuity and poor field of view (FOV) brightness uniformity existing in the prior art waveguide design, balancing and keeping consistent the energy utilization rate of each FOV, and improving the market brightness uniformity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of projection display, and in particular to a light waveguide structure and a near-eye display module. BACKGROUND

[0002] In the waveguide design process, in order to ensure that the field of view is as large as possible, the propagation angle difference of the light transmitted in the waveguide is often large. The propagation angles of the light beams corresponding to each field of view in the waveguide are inconsistent, which affects the pupil expansion times of the light beams. The light beam with a large propagation angle has fewer pupil expansion times, and the light beam with a small propagation angle has more pupil expansion times, as shown in FIG. 1. The propagation angle of the solid line shown in the figure is larger than that of the dashed line, and the light beam represented by the solid line has fewer pupil expansion times, and the light beam represented by the dashed line has more pupil expansion times. Figure 1

[0003] In order to ensure the continuity of the exit pupil, the thickness of the waveguide is relatively thin. When the pupil expansion times are relatively large, the coupling-out efficiency of the light needs to be reduced each time, and the coupling-out efficiency of each coupling-out light beam needs to be arranged in the propagation process. If the coupling-out efficiency is too large, the energy utilization rate of the light beam with a large number of pupil expansion times will be low, and if the coupling-out efficiency is too small, the energy utilization rate of the light beam with a small number of pupil expansion times will be low. The above will result in poor uniformity of the brightness of the field of view, as shown in FIG. 2. The left and right two images are the brightness output diagrams of the field of view when the coupling-out efficiency is high and low, respectively. Figure 2 SUMMARY

[0004] The purpose of the present application is to provide a light waveguide structure and a near-eye display module, which can alleviate the technical problems of discontinuity of the exit pupil and poor uniformity of the brightness of the field of view in the existing waveguide design.

[0005] In order to achieve the above-mentioned purpose of the application, the first aspect of the embodiment of the present application provides a light waveguide structure, comprising:

[0006] The light splitting waveguide and the imaging waveguide are arranged in parallel.

[0007] The imaging waveguide comprises a first coupling-in region and a second coupling-in region located at two ends of the imaging waveguide, respectively.

[0008] The light splitting waveguide is used for splitting the coupling-in light into two beams, one of which is coupled into the first coupling-in region of the imaging waveguide, and the other of which is coupled into the second coupling-in region of the imaging waveguide through the light splitting waveguide, so that there are two light beams in the imaging waveguide, which propagate in opposite directions and have different propagation angles.

[0009] Optionally, the light splitting waveguide is a diffractive light waveguide.

[0010] ​​When the image source is coupled into the beam splitting waveguide vertically, the light emitted by the image source enters the coupling-in region of the beam splitting waveguide to generate 0th-order diffracted light, -1st-order diffracted light and +1st-order diffracted light; wherein the 0th-order diffracted light enters the first coupling-in region of the imaging waveguide along the original light direction, and the +1st-order diffracted light is transmitted in the beam splitting waveguide by total reflection, and after reaching the coupling-out region of the beam splitting waveguide, is coupled into the imaging waveguide through the second coupling-in region of the imaging waveguide.

[0011] Optionally, the beam splitting waveguide comprises a relief type diffractive optical waveguide or a holographic type diffractive optical waveguide.

[0012] Optionally, the coupling-in region / coupling-out region of the beam splitting waveguide comprises a straight grating, an inclined grating, a blazed grating or a metasurface structure.

[0013] Optionally, the beam splitting waveguide and the imaging waveguide are projected along the normal direction of the beam splitting waveguide or the imaging waveguide, and on the projection plane, the first coupling-in region of the imaging waveguide can contain the coupling-in region of the beam splitting waveguide; and the second coupling-in region of the imaging waveguide can contain the coupling-out region of the beam splitting waveguide.

[0014] Optionally, on the projection plane, the coupling-in region of the beam splitting waveguide coincides with the first coupling-in region of the imaging waveguide, and the coupling-out region of the beam splitting waveguide coincides with the second coupling-in region of the imaging waveguide.

[0015] Optionally, the coupling-out region of the beam splitting waveguide is in the shape of a rectangle or an ellipse; and the second coupling-in region of the imaging waveguide is in the shape of a rectangle or an ellipse.

[0016] Optionally, the beam splitting waveguide is a geometric array type waveguide; the beam splitting waveguide comprises one coupling-in region and two coupling-out regions.

[0017] The light emitted by the image source enters the beam splitting waveguide through the coupling-in region of the beam splitting waveguide; when the light emitted by the image source enters the first coupling-out region of the beam splitting waveguide, the light emitted by the image source is divided into two beams, one of which is coupled out from the first coupling-out region of the beam splitting waveguide and coupled into the imaging waveguide through the first coupling-in region of the imaging waveguide, and the other of which is coupled out from the second coupling-out region of the beam splitting waveguide after propagating in the beam splitting waveguide and enters the imaging waveguide through the second coupling-in region of the imaging waveguide.

[0018] Optionally, the beam splitting waveguide and the imaging waveguide are projected along the normal direction of the beam splitting waveguide or the imaging waveguide, and on the projection plane, the first coupling-in region of the imaging waveguide can contain the first coupling-out region of the beam splitting waveguide; and the second coupling-in region of the imaging waveguide can contain the second coupling-out region of the beam splitting waveguide.

[0019] The second aspect of the embodiment of the present application provides a near-eye display module, comprising an image source and the optical waveguide structure of the first aspect, wherein the image source is configured to output imaging light and project the imaging light to the optical waveguide structure, and the imaging light is output after being transmitted through the optical waveguide structure.

[0020] The one or more technical solutions in the embodiment of the present application have at least the following technical effects or advantages:

[0021] In the scheme of the embodiment of the present application, the beam splitting waveguide and the imaging waveguide are arranged in parallel, the beam splitting waveguide is configured to split the in-coupled light into two beams, one of which is coupled into the first in-coupling region of the imaging waveguide, and the other is coupled into the second in-coupling region of the imaging waveguide through the beam splitting waveguide, so that there are two beams of light propagating in opposite directions and having different propagation angles in the imaging waveguide. Since there are more than two kinds of diffracted light in the waveguide, one kind of diffracted light has a large propagation angle and a small pupil expansion times, and the other kind of diffracted light has a small propagation angle and a large pupil expansion times, and the two beams of light propagate into the out-coupling region of the imaging waveguide from two opposite directions, so that the energy utilization rate of each field of view can be balanced and kept consistent, thereby alleviating the technical problems of pupil discontinuity and poor field of view brightness uniformity existing in the existing waveguide design. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor:

[0023] Figure 1 A schematic diagram of light beams with different propagation angles;

[0024] Figure 2 A field of view brightness output diagram for different out-coupling efficiencies;

[0025] Figure 3 A schematic diagram of the optical waveguide structure provided by the embodiment of the present application;

[0026] Figure 4 A propagation wave vector diagram provided by the embodiment of the present application;

[0027] Figure 5 A schematic diagram of the propagation angle and the azimuth angle provided by the embodiment of the present application;

[0028] Figure 6 A schematic diagram of the beam splitting waveguide provided by the embodiment of the present application as a diffractive waveguide;

[0029] Figure 7 A schematic diagram of the shape of the out-coupling region of the light-splitting waveguide provided in the embodiments of the present application is shown in the following figure;

[0030] Figure 8 A schematic diagram of the light-splitting waveguide provided in the embodiments of the present application is a geometric array type waveguide;

[0031] Figure 9 A schematic diagram of the shape of the out-coupling region of the light-splitting waveguide provided in the embodiments of the present application is shown in the following figure; DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0033] The embodiments of the present application propose a two-piece waveguide structure, as shown in the following figure, Figure 3 One piece of waveguide is used as a light-splitting structure, i.e., a light-splitting waveguide 30, and the other piece is used as an imaging waveguide 31. The imaging waveguide 31 includes a first in-coupling region 311 and a second in-coupling region 312 located at two ends of the imaging waveguide 31, respectively. The light-splitting waveguide 30 can split the in-coupled light into two beams, one of which is in-coupled from the first in-coupling region 311, and the other of which is in-coupled from the second in-coupling region 312 located at another position of the imaging waveguide 31. Thus, there are two beams of light propagating in opposite directions and having different propagation angles in the imaging waveguide 31. During the transmission of the two beams of light in the imaging waveguide 31, the two beams of light propagate into an out-coupling region 313 of the imaging waveguide 31 from two opposite directions. In this way, the energy utilization of each field of view can be balanced and kept consistent, thereby improving the brightness uniformity.

[0034] In the embodiments of the present application, if there are two or more kinds of diffracted light of each field of view beam propagating in the waveguide, and one kind of diffracted light has a large propagation angle and a small number of pupil expansion times, and the other kind of diffracted light has a small propagation angle and a large number of pupil expansion times. As shown in the propagation wave vector diagram in the following figure, Figure 4 the energy utilization of each field of view can be balanced and kept consistent. As can be seen from the propagation wave vector diagram, the azimuth angles of the two orders of diffracted light differ by 180 degrees, as shown in the following figure, Figure 5 and a schematic diagram of the azimuth angle is shown in the following figure. Figure 5 Therefore, the two kinds of diffracted light need to propagate into the out-coupling region from two opposite directions to achieve the effect of brightness uniformity.

[0035] In a possible implementation, when the image source is coupled in vertically, the azimuth angle of the incident light of the image source is greater than 90 degrees, and the geometric array waveguide is difficult to ensure that all the light of the field of view can be transmitted into the next coupling-in area along the light splitting waveguide. Therefore, when the image source is coupled in vertically, the diffractive optical waveguide can be used as the light splitting waveguide. The diffractive waveguide can be a relief type or a holographic type. The relief grating can be a straight grating, an inclined grating or a blazed grating. Generally, the inclined grating and the blazed grating can ensure as little energy loss as possible.

[0036] As shown in Figure 6 , Figure 6 The two beams of light split by the light splitting waveguide 30 are distinguished by the dashed line and the solid line in the figure. Taking the fiber scanning display device as an example, the light emitted by the fiber scanning display device enters the coupling-in area of the light splitting waveguide 30 as parallel light after the imaging system, and the light will generate 0th-order, -1st-order and +1st-order diffracted light in the coupling-in area 301 of the light splitting waveguide 30. Among them, the 0th-order light enters the coupling-in area 311 of the imaging waveguide 31 in the original light direction, the -1st-order diffracted light is transmitted out of the light splitting waveguide 30 and is absorbed and consumed, and the +1st-order diffracted light is transmitted in the light splitting waveguide 30 by total reflection and finally reaches the coupling-out area 302 of the light splitting waveguide 30. In order to ensure that the imaging waveguide 31 has good brightness uniformity after expansion, the coupling-in area 301 of the light splitting waveguide 30 adopts an inclined grating, a blazed grating or a super surface structure, so that the energy ratio of the 0th-order diffracted light and the +1st-order diffracted light in the diffracted light is slightly lower than 1:1, and the -1st-order diffracted light is as low as possible. The specific value of the energy ratio of the 0th-order diffracted light and the +1st-order diffracted light can be optimized and matched according to the diffraction efficiency of each area. During the light transmission process, because the light of each field of view has different azimuth angles and incident angles when coupled in, the azimuth angles of the light propagating in the light splitting waveguide 30 are different, and the coupling-out area 302 of the light splitting waveguide 30 can adopt a rectangular or elliptical shape, which can contain the shape of all the coupling-out light, as shown in Figure 7 .

[0037] Similarly, as shown in Figure 7As shown, to ensure that the coupled light rays can smoothly enter the second coupling region 312 of the imaging waveguide 31, the shape of the second coupling region 312 of the imaging waveguide 31 is consistent with or includes the shape of the coupling region 302 of the beam splitter waveguide 30. That is, when the beam splitter waveguide 30 and the imaging waveguide 31 are projected along the normal direction (i.e., the Z-axis direction) of the beam splitter waveguide 30 or the imaging waveguide 31, on the projection plane, the first coupling region 311 of the imaging waveguide 31 coincides with the coupling region 301 of the beam splitter waveguide 30, or the first coupling region 311 of the imaging waveguide 31 can include the coupling region 301 of the beam splitter waveguide 30; the second coupling region 312 of the imaging waveguide 31 coincides with the coupling region 302 of the beam splitter waveguide 30, or the second coupling region 312 of the imaging waveguide 31 can include the coupling region 302 of the beam splitter waveguide 30. Here, the projection plane is the plane containing the x and y spatial dimensions, such as... Figure 5 As shown.

[0038] like Figure 6 As shown, after light propagates in the beam splitter 30, it enters the coupling region 302, generating -2nd, -1st, and 0th order transmitted diffracted light. The 0th order light exits the beam splitter 30 and is consumed. The -1st order diffracted light enters the second coupling region 312 of the imaging waveguide 31. The -2nd order diffracted light returns in the imaging waveguide 31 at the original propagation angle. Similarly, to ensure high energy utilization, the coupling region 302 of the beam splitter 30 adopts structures such as slanted gratings, blazed gratings, or metasurfaces to make the energy of the -1st order diffracted light as high as possible and the energy of the -2nd order diffracted light as low as possible.

[0039] In another possible implementation, the image source is tilted and coupled in, and the azimuth angles of the rays from the image source coupled into the beam-splitting waveguide are all less than 90 degrees. In this case, the beam-splitting waveguide can be a geometric array type waveguide. For example... Figure 8 As shown, the optical splitting waveguide 80 using a geometric array waveguide includes one coupling region and two coupling out regions.

[0040] Taking a fiber optic scanning display device as the image source as an example, after passing through the imaging system, the fiber optic scanning display device emits parallel light into the coupling region of the beam splitter 80, and then propagates through the coupling region into the beam splitter 80. When the light enters the first coupling region 801 of the beam splitter 80, the beam is split into two beams. One beam directly enters the first coupling region 811 of the imaging waveguide 81, while the other beam continues to propagate within the beam splitter 80. After propagation within the beam splitter 80, the light enters the second coupling region 802 of the beam splitter 80, and then is completely reflected into the second coupling region 812 of the imaging waveguide 81. To ensure good brightness uniformity after pupil dilation in the imaging waveguide 81, the beam splitting energy ratio is generally equal to 1:1. Similarly, during light transmission, because the light rays from each field of view have different azimuth angles and incident angles when coupled into the imaging waveguide 81, the azimuth angles of each light ray propagating in the imaging waveguide 81 are different. Therefore, as...Figure 9 As shown, the second coupling-in region 812 of the imaging waveguide 81 can be in the shape of a rectangle or an ellipse, or any other shape capable of containing all the out-coupled propagating light.

[0041] As can be seen from the above embodiments, after the image light is split by the splitting waveguide, the light corresponding to each field of view has two directions and different propagation angles in the imaging waveguide, thereby effectively alleviating the problems of pupil discontinuity and poor field of view brightness uniformity in the prior art waveguide design.

[0042] Based on the same inventive concept, the embodiments of the present application also provide a near-eye display module, which comprises an image source and a light waveguide structure, the image source is used to output imaging light and project to the light waveguide structure, and the imaging light is output after being transmitted through the light waveguide structure. The near-eye display module can be applied to AR glasses, and the image source can be a fiber scanning display device, a MEMS galvanometer, a Micro LED, etc., and the present application does not make any limitation on this.

[0043] All features disclosed in this specification, and / or all steps of any methods or processes disclosed, can be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0044] Any feature disclosed in this specification, unless stated otherwise, can be replaced by any equivalent or similar feature. That is, unless stated otherwise, each feature is one example only of a generic series of equivalent or similar features.

[0045] The present application is not limited to the foregoing specific embodiments. The application extends to any novel one, or any novel combination, of the features disclosed in this specification, and to any novel method or process disclosed, or any novel step of any novel method or process disclosed.

Claims

1. An optical waveguide structure, characterized by, include: Parallel-arranged beam-splitting waveguides and imaging waveguides; The imaging waveguide includes a first coupling region and a second coupling region located at both ends of the imaging waveguide, respectively. The beam splitter is used to split the coupled light into two beams. One beam is coupled into the imaging waveguide from the first coupling region, and the other beam is coupled into the imaging waveguide from the second coupling region through the beam splitter, so that there are two beams of light propagating in opposite directions with different propagation angles in the imaging waveguide.

2. The optical waveguide structure of claim 1, wherein, The beam splitter is a diffractive waveguide; When the image source is vertically coupled into the beam splitter, the light emitted from the image source enters the coupling region of the beam splitter and generates 0th-order diffraction light, -1st-order diffraction light, and +1st-order diffraction light. The 0th-order diffraction light enters the first coupling region of the imaging waveguide along the original ray direction, and the +1st-order diffraction light is transmitted in the beam splitter through total internal reflection. After reaching the coupling region of the beam splitter, it is coupled into the imaging waveguide through the second coupling region.

3. An optical waveguide structure as claimed in claim 2, c h a r a c t e r i s e d in that The beam splitter includes an embossed diffractive waveguide or a holographic diffractive waveguide.

4. An optical waveguide structure as claimed in claim 2 or 3, characterized in that The coupling region / coupling region of the beam splitter includes a straight-tooth grating, a tilted grating, a blazed grating, or a metasurface structure.

5. The optical waveguide structure of claim 2, wherein, Projecting the beam splitter and imaging waveguide along the normal direction of the beam splitter or imaging waveguide, on the projection plane, the first coupling region of the imaging waveguide can include the coupling region of the beam splitter; the second coupling region of the imaging waveguide can include the coupling region of the beam splitter.

6. An optical waveguide structure as claimed in claim 5, wherein, On the projection surface, the coupling region of the beam splitter waveguide coincides with the first coupling region of the imaging waveguide, and the coupling out region of the beam splitter waveguide coincides with the second coupling region of the imaging waveguide.

7. An optical waveguide structure as claimed in claim 6, c h a r a c t e r i s e d in that The shape of the coupling region of the beam splitter waveguide is rectangular or elliptical; the shape of the second coupling region of the imaging waveguide is rectangular or elliptical.

8. The optical waveguide structure of claim 1, wherein, The optical splitter is a geometric array waveguide; the optical splitter includes an input region and two output regions. The light emitted from the image source enters the beam splitter waveguide through the coupling region and propagates in the beam splitter waveguide. When the light emitted from the image source enters the first coupling region of the beam splitter waveguide, the light emitted from the image source is split into two beams. One beam is coupled out from the first coupling region of the beam splitter waveguide and coupled into the imaging waveguide through the first coupling region of the imaging waveguide. The other beam propagates through the beam splitter waveguide to the second coupling region of the beam splitter waveguide, and after coupling out, it enters the imaging waveguide through the second coupling region of the imaging waveguide.

9. An optical waveguide structure as claimed in claim 8, wherein, Projecting the beam splitter and imaging waveguide along the normal direction of the beam splitter or imaging waveguide, on the projection plane, the first coupling region of the imaging waveguide can include the first coupling region of the beam splitter; the second coupling region of the imaging waveguide can include the second coupling region of the beam splitter.

10. A near-eye display module, comprising: The invention includes an image source and an optical waveguide structure as described in any one of claims 1-9, wherein the image source is used to output imaging light rays and project them onto the optical waveguide structure, and the imaging light rays are transmitted through the optical waveguide structure and then output.

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