Diffractive optical waveguide and AR display device having same

Abstract

The invention discloses a diffractive optical waveguide and AR display equipment comprising the same. The diffraction optical waveguide comprises a waveguide substrate and a coupling-in grating, a turning grating and a coupling-out grating which are arranged on the substrate, the coupling-in grating, the turning grating and the coupling-out grating are respectively provided with a first grating vector, a second grating vector and a third grating vector, and the vector sum of the first grating vector, the second grating vector and the third grating vector is zero; the diffraction optical waveguide transmits visible light with the minimum wavelength of lambda min from the external environment, the grating period corresponding to the second grating vector is P2, and P2 is smaller than or equal to 0.7 lambda min. According to the embodiment of the invention, the characteristic that the turning grating can adopt a relatively small grating period is utilized, and the grating period of the turning grating is adjusted, so that the transmission diffraction light diffracted by the turning grating is totally reflected in the waveguide substrate and cannot enter human eyes, and therefore, the rainbow fringes are effectively inhibited.

Description

Technical Field

[0001] The present invention relates to a display technology based on a diffraction optical waveguide; in particular, to a diffraction optical waveguide for AR display and an AR display device having the same. Background Art

[0002] As a very smart and portable display technology, AR augmented reality technology is slowly becoming popular among the public. Display technology based on diffraction optical waveguides is one of the mainstream solutions for realizing AR display. A diffraction optical device can be provided on a waveguide substrate as an optical coupling device. The diffraction optical device can adopt a waveguide grating. For example, the diffraction optical waveguide can include an in-coupling grating and an out-coupling grating. The in-coupling grating receives the input light carrying image information from the optical machine and couples it into the waveguide substrate; the out-coupling grating propagates and expands the light carrying the image information while coupling the light out of the waveguide substrate to form an out-coupling light field. The eye receives the light from the out-coupling light field, so that, for example, the image carried by the incident light can be observed. The waveguide grating can also include a turning grating, which expands the light from the in-coupling grating in one direction and deflects it to propagate toward the out-coupling grating.

[0003] Existing diffractive optical waveguides may produce rainbow effects under ambient light conditions. Figure 1 As shown in the figure, when the external ambient light AL, especially the light from the light source (such as a spotlight and the sun) from the top direction illuminates the waveguide grating g on the diffractive light waveguide W, the diffraction optical device diffracts the ambient light to form diffracted light of different wavelengths entering the human eye in different directions (the diffracted light entering the human eye E, represented by the solid line, the dashed line and the dotted line, respectively, has different wavelengths). This causes the human eye to observe some colorful dispersion patterns (such as rainbow patterns), which greatly affects the viewing experience of people.

[0004] Therefore, there is a need to provide a diffractive optical waveguide that can suppress the rainbow effect to improve the user experience. Summary of the invention

[0005] An object of the present invention is to provide a diffractive optical waveguide for AR display and an AR display device having the same, which at least partially overcome the problems in the prior art.

[0006] According to one aspect of the present invention, a diffraction optical waveguide for AR display is provided, the diffraction optical waveguide comprising a waveguide substrate and an in-coupling grating, a turning grating and an out-coupling grating arranged on the waveguide substrate, wherein the in-coupling grating couples input light carrying image information incident thereon into the waveguide substrate and propagates it through total reflection, the turning grating expands the light from the in-coupling grating in a first direction and deflects it to propagate toward the out-coupling grating, and the out-coupling grating expands the light propagated therein in a second direction different from the first direction and couples it out from the waveguide substrate, thereby realizing image display in a viewing window area.

[0007] wherein the coupling-in grating, the turning grating and the coupling-out grating respectively have a first grating vector G1, a second grating vector G2 and a third grating vector G3, and a vector sum of the first grating vector G1, the second grating vector G2 and the third grating vector G3 is zero; and

[0008] The minimum wavelength transmitted by the diffractive light waveguide from the external environment is λ min The visible light, and the grating period corresponding to the second grating vector G2 is P2, P2≤0.7λ min .

[0009] Advantageously, the diffractive optical waveguide may further include an optical structure, wherein the optical blocking layer is disposed on a side of the diffractive optical waveguide opposite to the viewing window region and is configured to block wavelengths shorter than the minimum wavelength λ. min The light enters the diffractive optical waveguide.

[0010] Advantageously, the turning grating is a one-dimensional grating.

[0011] Advantageously, the turning grating is configured to satisfy: P2≤0.5λ min .

[0012] Advantageously, the turning grating is constructed to satisfy: P2≤280nm.

[0013] Advantageously, the turning grating is constructed to satisfy: P2≤200nm.

[0014] Advantageously, the refractive index of the waveguide substrate is n, n≥2.0, and the grating period corresponding to the third grating vector G3 is P3, P3≤0.7λ min .

[0015] Advantageously, the diffraction optical waveguide has an image horizontal direction and an image vertical direction which are orthogonal to each other and are parallel to the surface of the waveguide substrate, and when the diffraction optical waveguide is correctly positioned relative to a human eye for display, the image horizontal direction is parallel to a projection of an interpupillary line of a human eye on the diffraction optical waveguide; the image horizontal direction is determined so that the coupling-in grating is located in a positive direction of the image horizontal direction relative to the coupling-out grating; and the coupling-out grating is a one-dimensional grating, and the direction of the third grating vector G3 is deflected downward by an inclination angle relative to the positive direction of the image horizontal direction.

[0016] Advantageously, the outcoupling grating is configured to satisfy:

[0017] In some embodiments, the outline of the outcoupling grating is a rectangle, and two adjacent sides of the rectangle are parallel to the horizontal direction and the vertical direction of the image respectively.

[0018] According to another aspect of the present invention, there is also provided an AR display device, comprising a lens, wherein the lens comprises the diffractive optical waveguide as described above.

[0019] Advantageously, the AR display device is a near-eye display device and further comprises a frame for holding the lens close to the eye.

[0020] According to an embodiment of the present invention, by utilizing the characteristic of a turning grating that a relatively smaller grating period can be used, by adjusting the grating period of the turning grating, the transmitted diffraction light diffracted by the turning grating is totally reflected in the waveguide substrate and cannot enter the human eye, thereby effectively suppressing rainbow patterns. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0022] Figure 1 A schematic diagram of how ambient light forms rainbow patterns under the action of a waveguide grating of a diffractive light waveguide and affects a person's viewing experience;

[0023] Figure 2 is a schematic plan view of a diffractive optical waveguide for AR display according to the first embodiment of the present invention, showing an exemplary arrangement of an in-coupling grating, a turning grating and an out-coupling grating;

[0024] Figure 3 It is a schematic diagram of several orders of reflected light and diffracted light generated by the ambient light incident on the turning grating after being reflected and diffracted;

[0025] Figure 4is an exemplary wave vector space diagram of a diffractive optical waveguide according to the first embodiment of the present invention;

[0026] Figure 5 A variation of the diffractive optical waveguide for AR display according to the first embodiment of the present invention is schematically shown, wherein an optical blocking layer is provided on the side of the diffractive optical waveguide opposite to the window area;

[0027] Figure 6 A schematic diagram of an example of an AR display device according to Embodiment 1 of the present invention;

[0028] Figure 7 is a schematic plan view of a diffractive optical waveguide according to a second embodiment of the present invention;

[0029] Figure 8 A schematic diagram of an example of an AR display device according to the second embodiment of the present invention;

[0030] Fig. 9 is a schematic plan view of a diffractive optical waveguide for AR display according to Embodiment 3 of the present invention;

[0031] Fig.10 Shows Fig. 9 Different examples of periodic array structures of outcoupling gratings in diffractive optical waveguides are shown. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It will be appreciated that the specific embodiments described herein are only used to explain the relevant inventions, rather than to limit the invention. For ease of description, only the parts related to the invention are shown in the accompanying drawings. It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments may be combined with each other.

[0033] First, refer to Figures 2 to 5 A diffractive optical waveguide according to a first embodiment of the present invention is introduced.

[0034] Figure 2 FIG. 1 is a schematic plan view of a diffractive optical waveguide for AR display according to Embodiment 1 of the present invention, showing an exemplary arrangement of the waveguide grating therein. Specifically, Figure 2 As shown, the diffraction optical waveguide 100 comprises a waveguide substrate 100a and an in-coupling grating 101, a turning grating 102 and an out-coupling grating 103 arranged on the waveguide substrate 100a. The in-coupling grating 101 converts the input light L carrying image information incident thereon into in The deflection grating 102 couples the light from the coupling grating 101 into the waveguide substrate 100a and transmits it through total reflection. Figure 2The light is expanded (dilated pupil) in the x direction (shown in the figure) and deflected to propagate toward the outcoupling grating 103. The outcoupling grating 103 deflects the light propagated therein in a second direction (eg, Figure 2 The light is expanded in the y direction (as shown) (pupil expansion) and coupled out from the waveguide substrate 100a, thereby realizing image display in the viewing window area.

[0035] The coupling-in grating 101 has a first grating vector G1, the turning grating 102 has a second grating vector G2, and the coupling-out grating 103 has a third grating vector G3. in The vector sum of the first grating vector G1, the second grating vector G2 and the third grating vector G3 is zero, such as Figure 2 The direction of the "grating vector" is the direction along which the grating structure changes / arranges periodically (e.g., perpendicular to the direction of the grating lines / grooves), and the size of the "grating vector" is 2π / t, where t is the period / pitch of the grating structure in the direction of the "grating vector".

[0036] Since the areas of the turning grating 102 and the outcoupling grating 103 are usually significantly larger than those of the coupling-in grating 101, and in some diffraction waveguide applications, ambient light is blocked and cannot enter the coupling-in grating 101, the rainbow pattern is mainly generated by the turning grating 102 and the outcoupling grating 103.

[0037] According to the first embodiment of the present invention, the characteristic of the turning grating that a relatively smaller grating period can be used is utilized, and by adjusting the grating period of the turning grating, the transmitted diffracted light diffracted by the turning grating is totally reflected in the waveguide substrate and cannot enter the human eye, thereby effectively suppressing rainbow stripes. Specifically, in the diffraction light waveguide 100 according to the first embodiment of the present invention, the grating period corresponding to the second grating vector G2 of the turning grating 102 is P2, and P2≤0.7λ min , where λ min is the minimum wavelength of visible light from the external environment transmitted by the diffractive optical waveguide 100. Preferably, the grating period P2 of the second grating vector G2 is ≤ 0.5λ min .

[0038] The following reference Figure 3 The principle of suppressing rainbow fringes by the turning grating 102 in the diffraction optical waveguide 100 is introduced. Figure 3 The schematic diagram shows several orders of diffraction light generated after the incident light (ambient light AL) is incident on the turning grating 102, including, for example, the 0th order reflected diffraction light R0, the -1st order reflected diffraction light R -1 , 0th order transmission diffraction light T0 and -1st order transmission diffraction light T -1 , where -1 order transmitted diffraction light T-1 It is the main diffraction light that will produce rainbow patterns when the ambient light AL passes through the diffraction light waveguide. Here, the positive direction of the diffraction order of the diffraction light is defined as the direction pointed by the projection of the incident light on the plane where the grating is located.

[0039] According to the diffraction equation, we can get the -1 order transmitted diffraction light T -1 The diffraction angle of

[0040]

[0041] where θ inc is the incident angle of the ambient light, λ is the wavelength of the ambient light, n sub is the refractive index of the waveguide substrate in the diffractive light waveguide.

[0042] At the same time, according to this embodiment, the grating period P2 of the turning grating 102 is set so that the diffraction angle θ T-1 Greater than or equal to the critical angle of total reflection, that is:

[0043]

[0044] Combining the above relations (1) and (2), we can get:

[0045]

[0046] Thus we can get:

[0047] P2≤0.5λ(4).

[0048] It can be seen from the above relationship that when the grating period P2 of the turning grating 102 satisfies the relationship (4), that is, when the grating period P2 is less than half of the wavelength λ of the ambient light, the -1 order transmission diffraction light T generated by the diffraction of the ambient light by the turning grating 102 is -1 The diffraction angle θ T-1 is greater than the critical angle of total reflection, so the diffracted light will be totally reflected in the waveguide substrate 100 a and propagate along the waveguide substrate 100 a , and cannot pass through the diffraction light waveguide 100 to illuminate the human eye.

[0049] Accordingly, if the grating period P2 of the turning grating 102 is designed to be smaller than the minimum wavelength λ of the visible light from the external environment transmitted by the diffractive optical waveguide 100, min Half (i.e. P2≤0.5λ min ), the turning grating 102 suppresses the -1st order transmission diffraction light T of all visible light that can be transmitted through the diffraction light waveguide 100. -1 , thereby ideally suppressing rainbow lines.

[0050] According to this embodiment, the turning grating 102 may have a properly larger grating period P2, that is, P2≤0.7λ min , to provide greater flexibility in the design of the turning grating. The turning grating 102 designed in this way can completely suppress the -1st order transmission diffraction light T of the light with a longer wavelength in the visible light range that can be transmitted through the diffraction light waveguide 100. -1 , while suppressing the -1st order transmission diffraction light T of the shorter wavelength light in part of the incident angle range -1 , thereby helping to significantly improve the user experience of diffractive light waveguides.

[0051] When the grating period P2 is set to P2≤0.7λ min On this basis, for example, by combining the trimming of the grating area of ​​the turning grating 102 to avoid ambient light from entering a specific part of the turning grating 102, the -1st order transmission diffraction of the rainbow pattern can be suppressed when the grating period P2 exceeds half of the minimum incident wavelength.

[0052] In addition, by adjusting other grating parameters of the turning grating, such as grating height, duty cycle, etc., by setting the grating period P2 to P2≤0.7λ min , the -1 order transmitted diffraction light T at each wavelength can be -1 , the diffraction efficiency is reduced to a level invisible to the human eye, for example, less than 0.5%.

[0053] Considering the range of visible light (about 400-700 nm), in the diffraction optical waveguide 100 according to the first embodiment of the present invention, the grating period P2 of the turning grating 102 can be set to P2≤280 nm, and in some cases can be set to P2≤200 nm.

[0054] According to the present embodiment, the turning grating 102 is preferably a one-dimensional grating. However, this is not restrictive, and the turning grating 102 may also be a two-dimensional grating having a significantly smaller grating vector (not shown) in a direction perpendicular to the grating vector G2 and a very small diffraction period in the grating vector direction that does not produce any diffraction modulation.

[0055] It should be understood that according to the first embodiment of the present invention, not only is it proposed that the period of the waveguide grating is set to be less than or equal to 0.7λ min To effectively help suppress the rainbow effect or less than or equal to 0.5λ minTo ideally suppress the rainbow effect, the period setting condition is selected to be applied to the turning grating. This is because the inventors have found that the grating vectors G1 and G3 of the coupling-in grating 101 and the coupling-out grating 103 are limited by the annular space determined by the refractive index of the waveguide substrate; when the vector sum of the grating vectors G1, G2 and G3 of each grating of the diffraction light waveguide 100 is zero, the turning grating 102 can have a significantly larger grating vector G2 (corresponding to a significantly smaller grating period P2).

[0056] For ease of understanding, Figure 4 An exemplary wave vector space diagram of the diffractive optical waveguide according to the first embodiment of the present invention is shown, wherein each grating vector G1, G2 and G3 is exemplarily shown.

[0057] exist Figure 4 In the wave vector space shown, B1 represents the first wave vector boundary formed by satisfying the total internal reflection condition in the diffraction optical waveguide, and the first wave vector boundary B1 can be normalized to a circle with a radius of 1; B2 represents the second wave vector boundary corresponding to the maximum wave vector that can be transmitted in the diffraction optical waveguide, and the second wave vector boundary B2 is determined by the refractive index of the waveguide substrate. Light can be transmitted in the diffraction optical waveguide only when the light beam wave vector is in the annular space between the first wave vector boundary B1 and the second wave vector boundary B2. If the light beam wave vector is within the first wave vector boundary B1, the light will leak out of the waveguide substrate; if the light beam wave vector is outside the second wave vector boundary B2, the diffraction order does not exist, and the corresponding light carrying image information cannot be transmitted.

[0058] Figure 4 shows the input light L in Angular spectrum F. In order to realize image display, when the light is coupled into the waveguide substrate by the diffraction effect of the first grating vector G1 of the coupling-in grating 101, after the pupil is expanded by the diffraction effect of the second grating vector G2 of the turning grating 102, and when the light is coupled out by the diffraction effect of the third grating vector G3 of the coupling-out grating 103, the angular spectrum F (corresponding to the field angle) of the light must be maintained.

[0059] from Figure 4 It can be seen that the size of the first grating vector G1 and the third grating vector G3 (corresponding to the length of the grating vector) is very strictly limited by the two annular wave vector boundaries B1 and B2 of the wave vector space determined by the refractive index of the waveguide substrate and the size of the angular spectrum F; in contrast, the size of the second grating vector G2 can vary in a larger range as the directions of the grating vectors G1 and G3 change, and the maximum can almost reach the sum of the sizes of the grating vectors G1 and G3. Therefore, according to the first embodiment of the present invention, the grating period P2 corresponding to the second grating vector G2 of the turning grating 102 is set to be less than or equal to 0.7λ min , even less than or equal to 0.5λmin , to suppress the rainbow effect, can provide great flexibility for the waveguide material selection and grating parameter setting of the diffraction optical waveguide, reduce the design difficulty, and help reduce costs.

[0060] However, in some other examples according to this embodiment, in addition to setting the grating period of the turning grating as described above, a waveguide substrate with a high refractive index may be used, and the grating period of the coupling-in grating and / or the coupling-out grating may be set to be less than or equal to 0.7λ. min For example, the refractive index of the waveguide substrate n≥2.0, and the grating period P3 corresponding to the third grating vector G3 of the outcoupling grating is set to P3≤0.7λ min In this way, the rainbow pattern caused by the diffraction of ambient light by the outcoupling grating can also be well suppressed.

[0061] Figure 5 A variation of the diffractive optical waveguide according to the first embodiment of the present invention is schematically shown. Figure 5 The diffractive optical waveguide 100' shown in the modification has Figure 2 The diffractive light waveguide 100 shown in FIG. 1 is substantially the same in structure, except that the diffractive light waveguide 100′ further includes an optical blocking layer 104, which is disposed on a side of the diffractive light waveguide 100′ opposite to the window region EB and is configured to block wavelengths less than the minimum wavelength λ min The light enters the diffractive optical waveguide 100 ′, particularly, enters the region corresponding to the turning grating 102 .

[0062] The grating period of the coupling-in grating and / or the coupling-out grating is also set to be less than or equal to 0.7λ min or smaller, the optical blocking layer 104 may also block wavelengths smaller than the minimum wavelength λ min The light enters the area corresponding to the incoupling grating and / or the outcoupling grating.

[0063] According to this variation, by using an optical blocking layer to block light of a smaller wavelength from entering the diffractive optical waveguide 100 ′, it is possible to avoid limiting or compromising the design, manufacture and / or performance of the diffractive optical waveguide due to a too small grating period.

[0064] The optical barrier layer 104 may be an optical film layer, a super surface structure or a photonic crystal. As an example only, Figure 5It is shown that the turning grating 102 is arranged on the surface of the side opposite to the window area EB of the waveguide substrate 100a, and the optical barrier layer 104 is arranged to cover the turning grating 102. In this case, the optical barrier layer 104 can be composed of an optical film layer, for example. The optical barrier layer 104 can also cover other waveguide gratings, which will not be described in detail here. In other cases, for example, the turning grating 102 can be arranged on the surface of the same side of the waveguide substrate 100a as the field of view area EB, and the optical barrier layer 104 can be arranged to directly cover the other surface of the waveguide substrate 100a. In this case, the optical barrier layer 104 can be an optical film layer, a metasurface structure or a photonic crystal.

[0065] Reference above Figures 2 to 5 The diffraction optical waveguide according to the first embodiment of the present invention is introduced. According to the first embodiment of the present invention, an AR display device is also provided. Figure 6 As shown, the AR display device according to the first embodiment of the present invention comprises a lens 11, and the lens 11 comprises a diffractive optical waveguide 100 according to the first embodiment of the present invention. Preferably, the AR display device 10 is implemented as a near-eye display device and further comprises a frame 12 for holding the lens 11 close to the eye.

[0066] Next, refer to Figure 7 and Figure 8 A diffractive optical waveguide and an AR display device according to a second embodiment of the present invention are introduced. Figure 7 FIG. 2 shows a diffraction optical waveguide 200 according to a second embodiment of the present invention. Figure 8 A schematic diagram showing an example of an AR display device 20 according to the second embodiment of the present invention.

[0067] like Figure 7 As shown, the diffraction optical waveguide 200 includes a waveguide substrate 200a and an in-coupling grating 201, a turning grating 202 and an out-coupling grating 203 arranged on the waveguide substrate 200a. The in-coupling grating 201 diffracts the input light L carrying image information incident thereon. in The light from the coupling-in grating 201 is coupled into the waveguide substrate 200a and propagated by total reflection. The turning grating 202 expands the light from the coupling-in grating 201 in a first direction (pupil dilation) and deflects it to propagate toward the coupling-out grating 203. The coupling-out grating 203 expands the light propagated therein in a second direction different from the first direction (pupil dilation) and couples it out of the waveguide substrate 200a, thereby realizing image display in the viewing window area.

[0068] The coupling-in grating 201 , the deflection grating 202 , and the coupling-out grating 203 respectively have a first grating vector G1 , a second grating vector G2 , and a third grating vector G3 , and the vector sum of the first grating vector G1 , the second grating vector G2 , and the third grating vector G3 is zero.

[0069] According to the second embodiment of the present invention, rainbow stripes are suppressed by controlling the grating vector direction of the outcoupling grating. Figure 7 and Figure 8 The diffraction optical waveguide 200 has an image horizontal direction u and an image vertical direction v which are orthogonal to each other and are parallel to the surface of the waveguide substrate 200a. When the diffraction optical waveguide 200 is correctly positioned relative to the human eye for display, the image horizontal direction u is parallel to the projection of the interpupillary line IPL of the human eye on the diffraction optical waveguide 200; the image horizontal direction u is determined so that the coupling-in grating 201 is located in the positive direction of the image horizontal direction u relative to the coupling-out grating 203; and the coupling-out grating 203 adopts a one-dimensional grating, and the direction of the third grating vector G3 of the coupling-out grating 203 is deflected downward by an inclination angle relative to the positive direction of the image horizontal direction u. In some preferred examples, the inclination angle satisfy

[0070] The ambient light that produces rainbow patterns mainly comes from the strong light source in the overhead space, so it is necessary to prevent the light from these light sources from diffracting into the human eye. However, at the same time, the side light source will also produce rainbow patterns under the diffraction effect of the waveguide grating. In the diffraction light waveguide 200 according to the second embodiment of the present invention, the third grating vector G3 of the outcoupling grating 203 is set so that its direction is deflected downward by an inclination angle relative to the positive direction of the horizontal direction u of the image. The rainbow pattern caused by the light from the side light source being diffracted at the tail end of the outcoupling grating 203 can be avoided, and a proper balance can be achieved between avoiding the rainbow pattern caused by the light source in the overhead direction and avoiding the rainbow pattern caused by the side light source, thereby obtaining a good comprehensive rainbow pattern suppression effect.

[0071] exist Figure 7 and Figure 8 In the example shown, the outline of the outcoupling grating 203 may be a rectangle, and two adjacent sides of the rectangle are respectively parallel to the image horizontal direction u and the image vertical direction v. It should be understood that this is merely exemplary and the present invention is not limited in this respect.

[0072] The turning grating 202 of the diffraction optical waveguide 200 may have the same structure as the turning grating 102 in the diffraction optical waveguide 100 according to the first embodiment, that is, the grating period P2 corresponding to the second grating vector G2 of the turning grating 202 is less than or equal to 0.7λ. min , or less than or equal to 0.5λ min ,λ min is the minimum wavelength of visible light from the external environment transmitted by the diffractive optical waveguide 200. It should be understood that the diffractive optical waveguide 200 according to the second embodiment of the present invention is not limited in this aspect.

[0073] Similarly, the coupling-in grating 201 and / or the coupling-out grating 203 may also have a value less than or equal to 0.7λ. min or less than or equal to 0.5λ min The grating period is set to suppress the rainbow effect in the corresponding grating area. The diffractive optical waveguide 200 according to the second embodiment of the present invention is not limited in this aspect.

[0074] like Figure 8 As shown, the AR display device 20 according to the second embodiment of the present invention comprises a lens 21, and the lens 21 comprises a diffractive optical waveguide 200 according to the second embodiment of the present invention. Preferably, the AR display device 20 is implemented as a near-eye display device and further comprises a frame 22 for holding the lens 21 close to the eye.

[0075] Fig. 9 FIG. 3 shows a diffraction optical waveguide 300 according to the third embodiment of the present invention. Fig. 9 As shown, the diffraction optical waveguide 300 includes a waveguide substrate 300a and an in-coupling grating 301 and an out-coupling grating 303 disposed on the waveguide substrate 300a. The in-coupling grating 301 converts the input light L carrying image information incident thereon into in The light is coupled into the waveguide substrate 300a and propagated by total reflection. The outcoupling grating 303 expands the light propagated therein in a two-dimensional plane (pupil expansion) and couples it out from the waveguide substrate 300a, thereby realizing image display in the viewing window area.

[0076] The coupling-in grating 301 may be a one-dimensional grating, a two-dimensional grating or a combination of the two.

[0077] The outcoupling grating 303 may be a two-dimensional grating, or a combination of a two-dimensional grating and a one-dimensional grating. Fig.10 Different examples of the periodic array structure of the two-dimensional grating in the outcoupling grating 303 are shown.

[0078] Fig.10 In the example shown in FIG. (a), the outcoupling grating 303 includes an array structure 303A, Fig.10 In the example shown in Figure (b), the outcoupling grating 303 includes an array structure 303B. The array structures 303A and 303B respectively include a plurality of rows extending in the horizontal direction formed by arranging a plurality of optical unit structures u1 and u2, the optical unit structures u1 and u2 in each row are periodically arranged in the horizontal direction, and the plurality of rows have a predetermined interval in the vertical direction perpendicular to the horizontal direction. The optical unit structures u1 in two adjacent rows in the plurality of rows are aligned with each other in the horizontal direction, and the optical unit structures u2 in two adjacent rows in the plurality of rows are staggered with each other in the horizontal direction.

[0079] The horizontal period of the array structures 303A and 303B of the outcoupling grating 303 in the horizontal direction is Px, and the vertical period in the vertical direction is Py. According to the third embodiment of the present invention, the vertical period Py≤0.7λ min Preferably, Py≤0.5λ min .

[0080] In some examples, the vertical period Py of the array structure of the outcoupling grating 303 is ≤280 nm, and in some cases can be set to Py ≤200 nm.

[0081] Similar to the effect of setting the grating period in the diffractive optical waveguide 100 according to the first embodiment of the present invention, by setting the vertical period Py to be less than or equal to the minimum wavelength λ of the visible light transmitted by the diffractive optical waveguide 300, min 0.5 times of min , the -1st order transmission diffraction light T of the visible light that can be transmitted through the diffraction light waveguide 300 can be well suppressed. -1 , thereby suppressing rainbow lines.

[0082] The vertical period Py of the outcoupling grating 303 is set to be less than or equal to the minimum wavelength λ of the visible light transmitted by the diffraction optical waveguide 300. min 0.7 times of min , which can provide greater flexibility in the design of turn gratings while helping to suppress rainbow patterns to improve the user experience of diffractive light waveguides.

[0083] Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A diffractive optical waveguide for AR display, comprising: A waveguide substrate and an in-coupling grating, a turning grating and an out-coupling grating arranged on the waveguide substrate, wherein the in-coupling grating couples input light carrying image information incident thereon into the waveguide substrate and causes it to propagate through total reflection, the turning grating expands the light from the in-coupling grating in a first direction and deflects it to propagate toward the out-coupling grating, and the out-coupling grating expands the light propagated therein in a second direction different from the first direction and couples it out from the waveguide substrate, thereby realizing image display in a viewing window area, wherein the coupling-in grating, the turning grating and the coupling-out grating respectively have a first grating vector G1, a second grating vector G2 and a third grating vector G3, and a vector sum of the first grating vector G1, the second grating vector G2 and the third grating vector G3 is zero; and The minimum wavelength transmitted by the diffractive light waveguide from the external environment is λ min The visible light, and the grating period corresponding to the second grating vector G2 is P2, P2≤0.7λ min .

2. The diffractive optical waveguide according to claim 1, further comprising an optical blocking layer, wherein the optical structure is disposed on a side of the diffractive optical waveguide opposite to the window region and is configured to block wavelengths shorter than the minimum wavelength λ. min The light enters the diffractive optical waveguide.

3. The diffractive optical waveguide according to claim 1, wherein: The turning grating is a one-dimensional grating.

4. The diffractive optical waveguide according to claim 1, wherein: P2≤0.5λ min 。 5. The diffractive optical waveguide according to claim 1, wherein: P2≤280nm.

6. The diffractive optical waveguide according to claim 1, wherein: P2≤200nm.

7. The diffractive optical waveguide according to any one of claims 1 to 6, wherein: The refractive index of the waveguide substrate is n, n≥2.0, and the grating period corresponding to the third grating vector G3 is P3, P3≤0.7λ min .

8. The diffractive optical waveguide according to any one of claims 1 to 7, wherein: The diffractive optical waveguide has an image horizontal direction and an image vertical direction that are orthogonal to each other and are parallel to the surface of the waveguide substrate, and when the diffractive optical waveguide is correctly positioned relative to the human eye for display, the image horizontal direction is parallel to the projection of the interpupillary line of the human eye on the diffractive optical waveguide; The image horizontal direction is determined so that the coupling-in grating is located in the positive direction of the image horizontal direction relative to the coupling-out grating; and The outcoupling grating is a one-dimensional grating, and the direction of the third grating vector G3 is deflected downward by an angle relative to the positive direction of the horizontal direction of the image.

9. The diffractive optical waveguide according to claim 8, wherein:

10. The diffractive optical waveguide according to claim 8, wherein: The outline of the outcoupling grating is a rectangle, and two adjacent sides of the rectangle are parallel to the horizontal direction and the vertical direction of the image respectively.

11. An AR display device, comprising a lens, wherein the lens comprises the diffractive optical waveguide according to any one of claims 1 to 10.

12. The AR display device according to claim 11, wherein: The AR display device is a near-eye display device and also includes a frame for holding the lens close to the eye.

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