Grating Wave Export Pupil Expander and Augmented Reality Display Module

Abstract

The present invention provides a grating wave output pupil expander and an augmented reality display module, which relates to the technical field of augmented reality display modules. The grating wave output pupil expander includes a waveguide flat plate, the waveguide flat plate includes opposite first and second plate surfaces, an input grating and an output grating are arranged on the first plate surface, and the input grating and the output grating are arranged at intervals; a light reflection structure is further arranged on the waveguide flat plate, the light reflection structure has a reflection layer, the reflection layer is respectively connected to the first plate surface and the second plate surface, and the reflection layer is used for reflecting the diffracted light traveling in the direction of the input grating toward the direction of the output grating. When light propagates in the grating wave output pupil expander, a diffraction phenomenon will occur. Part of the diffracted light will move in the direction of the input grating and gradually move away from the output grating. The light reflection structure can reflect this part of the diffracted light toward the direction of the output grating, so as to be reused again, avoid waste of light energy, and ultimately the light energy received by the human eye retina is more and the brightness is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of augmented reality display modules, and more particularly to a grating waveguide exit pupil expander and an augmented reality display module. Background Art

[0002] Using the grating waveguide solution for exit pupil expansion, the virtual image generated by the projection module is guided to the human eye and imaged on the retina, so that the user can observe the virtual image. At the same time, the high transmittance of the grating waveguide ensures that ambient light can enter the human eye with low loss, ensuring that the user can observe both the virtual image and the real scene simultaneously, thus achieving the application purpose of augmented reality.

[0003] For the existing exit pupil expander using the grating waveguide solution, when light enters the waveguide and propagates in the waveguide, due to the existence of multiple diffraction orders, part of the energy is wasted and cannot be effectively utilized, resulting in a relatively low light intensity finally entering the retina. Summary of the Invention

[0004] The purpose of the present invention is to provide a grating waveguide exit pupil expander and an augmented reality display module to alleviate the technical problem of energy waste existing in the existing exit pupil expander.

[0005] In a first aspect, a grating waveguide exit pupil expander provided by an embodiment of the present invention includes a waveguide flat plate, the waveguide flat plate includes opposite first and second plate surfaces, an input grating and an output grating are provided on the first plate surface, and the input grating and the output grating are arranged at intervals;

[0006] A light reflection structure is further provided on the waveguide flat plate, the light reflection structure has a reflection layer, the reflection layer is respectively connected to the first plate surface and the second plate surface, and the reflection layer is used to reflect the diffracted light directed towards the input grating towards the output grating direction, wherein the input grating direction is the direction in which the output grating faces the input grating, and the output grating direction is opposite to the input grating direction.

[0007] Further, the light reflection structure is provided on the side surface of the waveguide flat plate, and the reflection layer is attached to the side surface; along the direction from the input grating towards the output grating, the input grating is located between the output grating and the light reflection structure.

[0008] Further, both the input grating and the output grating are one-dimensional gratings;

[0009] The length direction of the reflection layer, the grating direction of the input grating, and the grating direction of the output grating are parallel.

[0010] Further, the input grating is a one-dimensional grating, and the output grating is a two-dimensional grating.

[0011] Further, the light reflection structure is embedded in the waveguide flat plate. Along the direction from the input grating towards the output grating, the light reflection structure is located between the input grating and the output grating.

[0012] A notch is provided on the light reflection structure, and the notch is used to avoid the light propagating from the end side where the input grating is located towards the end side where the output grating is located.

[0013] Further, the number of the light reflection structures is two, namely a first light reflection structure and a second light reflection structure.

[0014] The first light reflection structure is arranged on the side surface of the waveguide flat plate, and the reflection layer of the first light reflection structure is attached to the side surface. Along the direction from the input grating towards the output grating, the input grating is located between the output grating and the first light reflection structure.

[0015] The second light reflection structure is embedded in the waveguide flat plate. Along the direction from the input grating towards the output grating, the second light reflection structure is located between the input grating and the output grating.

[0016] A notch is provided on the second light reflection structure, and the notch is used to avoid the light propagating from the end side where the input grating is located towards the end side where the output grating is located.

[0017] Further, the light reflection structure attached to the side surface of the waveguide flat plate is a reflective film. The grating waveguide exit pupil expander includes a protection strip for protecting the reflective film. The protection strip is connected to the back surface of the reflective film so that the reflective film is clamped between the side surface of the waveguide sheet and the protection strip.

[0018] Further, the input grating is a surface relief grating, a volume holographic grating, a rectangular grating, a triangular grating or a trapezoidal grating.

[0019] The output grating is a surface relief grating or a volume holographic grating.

[0020] In a second aspect, an augmented reality display module provided by an embodiment of the present invention includes an image source, a projection system and the above-mentioned grating waveguide exit pupil expander.

[0021] The projection system is used to convert the light emitted by the image source into parallel light beams and send the parallel light beams to the input grating.

[0022] Further, the image source is a reflective projection display, a digital light processor, a liquid crystal flat panel display or a micro light emitting diode.

[0023] An embodiment of the present invention provides a grating waveguide pupil expander, the grating waveguide pupil expander includes a waveguide plate, the waveguide plate includes a first plate surface and a second plate surface opposite to each other, a coupling-in grating and a coupling-out grating are arranged on the first plate surface, and the coupling-in grating and the coupling-out grating are arranged at intervals, and the incident light enters the waveguide plate from the coupling-in grating, and is emitted from the coupling-out grating to enter the human eye after multiple total reflections in the waveguide plate. A light reflection structure is also arranged on the waveguide plate, and the light reflection structure has a reflection layer, and the reflection layer is connected to the first plate surface and the second plate surface respectively, and the reflection layer is used to reflect the diffracted light emitted in the direction of the coupling-in grating in the direction of the coupling-out grating. When the light propagates in the grating waveguide pupil expander, diffraction phenomenon will occur, and part of the diffracted light will move in the direction of the coupling-in grating, gradually away from the coupling-out grating, and the light reflection structure can reflect this part of the diffracted light in the direction of the coupling-out grating, so as to reuse it, thereby avoiding the waste of light energy, and finally the retina of the human eye receives more light energy and higher brightness.

[0024] An embodiment of the present invention provides an augmented reality display module, the augmented reality display module includes an image source, a projection system and the above-mentioned grating waveguide pupil expander; the projection system is used to convert the light emitted by the image source into a parallel light beam, and send the parallel light beam to the coupling grating. Because the augmented reality display module provided by the embodiment of the present invention refers to the above-mentioned grating waveguide pupil expander, the augmented reality display module provided by the embodiment of the present invention also has the advantages of the grating waveguide pupil expander. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A front view of the grating waveguide out-pupil expander provided in Example 1 of the present invention;

[0027] Figure 2 A bottom view of the grating waveguide out-pupil expander provided in Example 1 of the present invention;

[0028] Figure 3 A schematic diagram of a grating waveguide pupil expander provided in Example 1 of the present invention;

[0029] Figure 4 A front view of a grating waveguide output pupil expander provided in Example 1 of the present invention, in which the coupling-in grating is a triangular grating;

[0030] Figure 5 The front view of the input grating of the grating wave output pupil expander provided in Embodiment 1 of the present invention is a rectangular grating;

[0031] Figure 6 The front view of the input grating of the grating wave output pupil expander provided in Embodiment 1 of the present invention is a trapezoidal grating;

[0032] Figure 7 The side view of the grating wave output pupil expander provided in Embodiment 2 of the present invention;

[0033] Figure 8 The bottom view of the grating wave output pupil expander provided in Embodiment 2 of the present invention;

[0034] Figure 9 The schematic diagram of the grating wave output pupil expander provided in Embodiment 2 of the present invention;

[0035] Figure 10 The schematic diagram of the included angle between two dimensions of the output grating of the grating wave output pupil expander provided in Embodiment 2 of the present invention is 60°;

[0036] Figure 11 The bottom view of the grating wave output pupil expander provided in Embodiment 3 of the present invention.

[0037] Icon: 110 - waveguide flat plate; 120 - input grating; 130 - output grating; 200 - light reflection structure; 300 - protection strip; 410 - first light reflection structure; 420 - second light reflection structure. Detailed implementation manners

[0038] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Embodiment 1

[0040] As Figures 1-3As shown, an exit pupil expander for grating waves provided by an embodiment of the present invention, the exit pupil expander for grating waves includes a waveguide flat plate 110, the waveguide flat plate 110 includes a first plate surface and a second plate surface opposite to each other, an input grating 120 and an output grating 130 are arranged on the first plate surface, and the input grating 120 and the output grating 130 are arranged at intervals. Incident light enters the waveguide flat plate 110 from the input grating 120 and can be totally reflected multiple times in the waveguide flat plate 110 and then exit from the output grating 130 and enter the human eye. A light reflection structure 200 is further arranged on the waveguide flat plate 110, the light reflection structure 200 has a reflection layer, the reflection layer is respectively connected to the first plate surface and the second plate surface, and the reflection layer is used to reflect the diffracted light in the direction of the input grating 120 towards the direction of the output grating 130. When light propagates in the exit pupil expander after passing through the input grating, a diffraction phenomenon will occur. Part of the diffracted light will move towards the direction of the input grating 120 and gradually move away from the output grating 130, while the light reflection structure 200 can reflect this part of the diffracted light towards the direction of the output grating 130, so as to be reused again, avoiding the waste of light energy, and finally the human eye retina receives more light energy and higher brightness.

[0041] Wherein, the direction of the input grating 120 is the direction of the output grating 130 towards the input grating 120, that is Figure 1 the direction from left to right in Figure 1 ; the direction of the output grating 130 is opposite to the direction of the input grating 120, that is

[0042] In this embodiment, the light reflection structure 200 is arranged on the side surface of the waveguide flat plate 110, and the reflection layer is attached to the side surface; along the direction from the input grating 120 towards the output grating 130, the input grating 120 is located between the output grating 130 and the light reflection structure 200.

[0043] Specifically, in this embodiment, the waveguide flat plate 110 can be a rectangular plate-like structure, and the light reflection structure 200 is attached to the side surface of the waveguide flat plate 110 near one end of the input grating 120. The incident light vertically irradiated on the input grating 120 by the projection system will diffract at the connection between the input grating 120 and the waveguide flat plate 110. As Figure 3 shown, the incident light will generate three diffraction orders, namely the T-1 order, the T0 order, and the T+1 order. Among them, the diffracted light of the T-1 order is guided to the output grating 130 and is coupled out by the output grating 130. The diffracted light of the T+1 order will propagate to the side surface of the waveguide flat plate 110, and under the reflection of the light reflection structure 200, its propagation direction is changed and it propagates towards one end of the output grating 130, avoiding the diffracted light generated by the waveguide flat plate 110 from exiting from the side surface of the waveguide flat plate 110, resulting in energy waste, and improving the overall light energy utilization rate of the input grating 120.

[0044] In this embodiment, both the input grating 120 and the output grating 130 can be one-dimensional gratings; and the length direction of the reflection layer, the grating direction of the input grating 120, and the grating direction of the output grating 130 are parallel, and the reflection layer of the optical reflection structure 200 covers the entire side surface of the waveguide plate 110.

[0045] In this embodiment, the output grating 130 can also be a two-dimensional grating.

[0046] The optical reflection structure 200 attached to the side surface of the waveguide plate 110 is a reflective film, and the reflective film can be a metal reflective film or an all-dielectric reflective film. The grating waveguide exit pupil expander includes a protective strip 300 for protecting the reflective film. The material of the protective strip 300 can be the same as that of the waveguide plate 110. The protective strip 300 is connected to the back surface of the reflective film so that the reflective film is clamped between the side surface of the waveguide sheet and the protective strip 300, and the reflective film clamped in the middle can be well protected, reducing the probability of damage.

[0047] As Figures 4-6 shown, the input grating 120 can be a surface relief grating, a volume holographic grating, a rectangular grating, a triangular grating, or a trapezoidal grating; the output grating 130 can be a surface relief grating or a volume holographic grating.

[0048] Embodiment 2

[0049] As Figures 7-9 shown, the difference from Embodiment 1 is that in this embodiment, the input grating 120 is a one-dimensional grating and the output grating 130 is a two-dimensional grating. The optical reflection structure 200 is embedded in the waveguide plate 110, and along the direction from the input grating 120 towards the output grating 130, the optical reflection structure 200 is located between the input grating 120 and the output grating 130; a notch is provided on the optical reflection structure 200, and the notch is used to avoid the light propagating from the end side where the input grating 120 is located towards the end side where the output grating 130 is located.

[0050] In this embodiment, the incident light vertically irradiated on the input grating 120 by the projection system will be reflected multiple times in the waveguide plate 110 and propagate towards the output grating 130. When the light contacts the output grating 130, since the output grating 130 is a two-dimensional grating, diffracted light of multiple diffraction orders will be generated. Part of the diffracted light propagates towards the input grating 120. By providing the optical reflection structure 200 between the input grating 120 and the output grating 130, this part of the diffracted light can be reflected back towards the output grating 130 and finally enter the output grating 130, thereby improving the optical efficiency of the system. Avoiding the waste of energy by some diffraction orders and improving the overall optical efficiency of the exit pupil expander.

[0051] The manufacturing process of the waveguide flat plate 110 of the embedded optical reflection structure 200 is as follows:

[0052] Take two glass plates. Along the width direction of the glass plates, coat two reflection films on the side surface of one of the glass plates, and the two reflection films are arranged at intervals, and the gap between the two forms the notch;

[0053] Dock the side surface of the glass plate coated with the reflection film with the side surface of the other glass plate, glue them together, and obtain the waveguide flat plate 110 embedded with the optical reflection structure 200 after cutting and polishing.

[0054] Among them, the width of the notch is related to parameters such as the width of the coupling grating 120 and the field of view angle of the expander, and the calculation formula is:

[0055] D = D0 + 2 * L * tanθ

[0056] Among them, D0 is the width of the coupling grating 120, L is the distance between the farthest grating unit of the coupling grating 120 from the optical reflection structure 200 and the optical reflection structure 200, and θ is the maximum deflection angle of the diffracted light of the coupling grating 120.

[0057] As Figure 10 shown, the included angle between the two dimensions of the output grating 130 can be 45°, 60°, or 90°, etc.

[0058] Embodiment 3

[0059] As Figure 11 shown, the difference from Embodiment 1 and Embodiment 2 is that in this embodiment, the output grating 130 is a two-dimensional grating and takes into account the advantages of Embodiment 1 and Embodiment 2.

[0060] Specifically, in this embodiment, the number of the optical reflection structures 200 is two, namely the first optical reflection structure 410 and the second optical reflection structure 420; the first optical reflection structure 410 is arranged on the side surface of the waveguide flat plate 110, and the reflection layer of the first optical reflection structure 410 is attached to the side surface; along the direction of the coupling grating 120 towards the output grating 130, the coupling grating 120 is located between the output grating 130 and the first optical reflection structure 410; the second optical reflection structure 420 is embedded in the waveguide flat plate 110, and along the direction of the coupling grating 120 towards the output grating 130, the second optical reflection structure 420 is located between the coupling grating 120 and the output grating 130; a notch is arranged on the second optical reflection structure 420, and the notch is used to avoid the light propagating from the end side where the coupling grating 120 is located towards the end side where the output grating 130 is located.

[0061] The waveguide plate 110 may be a rectangular plate-shaped structure, and the first light reflecting structure 410 is attached to the side surface of the waveguide plate 110 near one end of the coupling-in grating 120. The incident light vertically irradiated by the projection system to the coupling-in grating 120 will be diffracted at the connection between the coupling-in grating 120 and the waveguide plate 110, and some orders of diffracted light will propagate to the side surface of the waveguide plate 110, and change the propagation direction under the reflection effect of the first light reflecting structure 410, and propagate to one end of the coupling-out grating 130, thereby preventing the diffracted light generated by the waveguide plate 110 from being transmitted from the side surface of the waveguide plate 110, causing energy waste. When light contacts the out-coupling grating 130, since the out-coupling grating 130 is a two-dimensional grating, diffraction light of multiple diffraction orders will be generated, and part of the diffraction light will propagate toward the coupling-in grating 120. A second light reflecting structure 420 is provided between the coupling-in grating 120 and the out-coupling grating 130, which can reflect part of the diffraction light back to propagate toward the coupling-out grating 130 and finally enter the out-coupling grating 130, thereby improving the light efficiency of the system.

[0062] In summary, in the existing technical solutions, due to the existence of multiple diffraction orders, some energy will be wasted and cannot be effectively utilized. The present invention uses the diffraction orders that cannot be used in the existing solutions by setting a light reflection structure 200 on the side and / or inside the flat waveguide, thereby improving the overall light efficiency of the exit pupil expander. This helps to improve the light energy utilization rate of the augmented reality display device and improve the system display brightness.

[0063] An embodiment of the present invention provides an augmented reality display module, which includes an image source, a projection system, and the above-mentioned grating waveguide pupil expander; the projection system is used to convert the light emitted by the image source into a parallel light beam, and send the parallel light beam to the coupling grating 120. Because the augmented reality display module provided by the embodiment of the present invention refers to the above-mentioned grating waveguide pupil expander, the augmented reality display module provided by the embodiment of the present invention also has the advantages of the grating waveguide pupil expander.

[0064] The image source may be a reflective projection display, a digital light processor, a liquid crystal flat panel display or a micro light emitting diode.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A grating wave-derived pupil expander, characterized in that, The grating wave exit pupil expander includes a waveguide flat plate (110), the waveguide flat plate (110) includes opposite first and second plate surfaces, an input grating (120) and an output grating (130) are arranged on the first plate surface, and the input grating (120) and the output grating (130) are arranged at intervals; An optical reflection structure (200) is further arranged on the waveguide flat plate (110), the optical reflection structure (200) has a reflection layer, the reflection layer is respectively connected to the first plate surface and the second plate surface, and the reflection layer is used for reflecting the diffracted light in the direction of the input grating (120) towards the direction of the output grating (130), wherein, the direction of the input grating (120) is the direction in which the output grating (130) faces the input grating (120), and the direction of the output grating (130) is opposite to the direction of the input grating (120); The number of the optical reflection structures (200) is two, namely a first optical reflection structure (410) and a second optical reflection structure (420); The first optical reflection structure (410) is arranged on the side surface of the waveguide flat plate (110), and the reflection layer of the first optical reflection structure (410) is attached to the side surface; along the direction from the input grating (120) towards the output grating (130), the input grating (120) is located between the output grating (130) and the first optical reflection structure (410); The input grating (120) is a one-dimensional grating, and the output grating (130) is a two-dimensional grating; The second optical reflection structure (420) is embedded in the waveguide flat plate (110), and along the direction from the input grating (120) towards the output grating (130), the second optical reflection structure (420) is located between the input grating (120) and the output grating (130); A notch is arranged on the second optical reflection structure (420), and the notch is used for avoiding the light propagating from the end side where the input grating (120) is located towards the end side where the output grating (130) is located; The input grating (120) is a surface relief grating, a rectangular grating, a triangular grating or a trapezoidal grating; The output grating (130) is a surface relief grating or a volume holographic grating.

2. The grating wave-derived pupil expander according to claim 1, wherein The optical reflection structure (200) attached to the side surface of the waveguide flat plate (110) is a reflection film, and the grating wave exit pupil expander includes a protection strip (300) for protecting the reflection film, and the protection strip (300) is connected to the back surface of the reflection film so that the reflection film is clamped between the side surface of the waveguide plate and the protection strip (300).

3. An augmented reality display module, characterized in that, The augmented reality display module includes an image source, a projection system and the grating wave exit pupil expander according to any one of claims 1-2; The projection system is used for converting the light emitted by the image source into a parallel light beam and sending the parallel light beam to the input grating (120).

4. The augmented reality display module according to claim 3, characterized in that, The image source is a reflective projection display, a digital light processor, a liquid crystal flat panel display or a micro light emitting diode.

Images