Diffractive optical structure, light guide device and head-mounted display equipment

Abstract

The embodiment of the invention provides a diffractive optical structure, a light guide device and head-mounted display equipment. Wherein the diffractive optical structure comprises repetitive units periodically presented in the P1 direction and the P2 direction, the periodic units in the P1 direction are of a strip-shaped structure, and the periodic units in the P2 direction are of an addition or subtraction periodic biaxial structure on the strip-shaped structure; wherein the biaxial directions of the biaxial structure respectively correspond to the P1 direction and the P2 direction, and the biaxial lengths of the biaxial structure are different. The diffractive optical structure provided by the embodiment of the invention is such as a grating structure, has many adjustable parameters, and can perform more flexible regulation and control on coupling-out efficiency and pupil expansion efficiency after being applied to a coupling-out area of a light guide device, thereby realizing uniform propagation of imaging light.

Description

Technical Field

[0001] Embodiments of the present application relate to the field of optical imaging technology. More specifically, embodiments of the present application relate to a diffractive optical structure, a light guiding device, and a head-mounted display device. Background Art

[0002] Augmented reality technology (AR) is a technology that combines virtual information with the real world. The optical waveguide solution is considered to be the best optical display solution in current augmented reality glasses. The optical waveguide solution is further divided into a geometric waveguide solution, a relief grating waveguide solution, and a volume holographic waveguide solution. Considering the process difficulty and optical effect comprehensively, the relief grating waveguide solution is the most studied technical solution among the three.

[0003] Currently, the relief grating waveguide solution mainly includes two paths: one-dimensional grating and two-dimensional grating. Using a two-dimensional grating in the coupling-out region can not only expand light but also achieve the coupling-out function. At different positions in the coupling-out region, the two-dimensional grating is required to have different pupil expansion efficiencies and coupling-out efficiencies. However, common two-dimensional gratings are square or circular, both of which are symmetric structures and have few adjustable parameters, making it difficult to control the coupling-out efficiency and pupil expansion efficiency, and it is not conducive to achieving uniform propagation of the image by adjusting the coupling-out energy. Summary of the Invention

[0004] The purpose of the present application is to provide a new technical solution for a diffractive optical structure, a light guiding device, and a head-mounted display device.

[0005] In a first aspect, the present application provides a diffractive optical structure. The diffractive optical structure includes repeating units that are periodically presented in the P1 direction and the P2 direction, and the periodic unit in the P1 direction is a strip structure, and the periodic unit in the P2 direction is a biaxial structure that is periodically added or subtracted on the strip structure;

[0006] Wherein, the biaxial directions of the biaxial structure respectively correspond to the P1 direction and the P2 direction, and the biaxial lengths of the biaxial structure are different.

[0007] Optionally, the biaxial structure includes a semi-elliptical structure or an elliptical structure.

[0008] Optionally, the center of the biaxial structure is located on one side edge of the strip structure.

[0009] Optionally, when the periodic unit in the P2 direction is an elliptical structure that is periodically added on the strip structure, the strip structure and the elliptical structure have a partially overlapping region, and the overlapping region is semi-elliptical.

[0010] Optionally, the periodic unit in the P2 direction is an elliptical structure that is periodically added or subtracted on the bar-shaped structure, and the center of any one of the elliptical structures is located on the same side edge of the bar-shaped structure; or,

[0011] the periodic unit in the P2 direction is a semi-elliptical structure that is periodically added or subtracted on the bar-shaped structure, and the center of any one of the semi-elliptical structures is located on the same side edge of the bar-shaped structure.

[0012] Optionally, the period of the diffractive optical structure in the P1 direction is P1', and the period in the P2 direction is P2';

[0013] the major axis length of the biaxial structure is 2a, and the minor axis length of the biaxial structure is 2b;

[0014] the width of the bar-shaped structure is c;

[0015] the minimum distance between the centers of the biaxial structures on adjacent bar-shaped structures in the P2 direction is d;

[0016] When subtracting the biaxial structure periodically on the bar-shaped structure, the following conditions are satisfied: c > b, P2' > 2a;

[0017] When adding the biaxial structure periodically on the bar-shaped structure, the following conditions are satisfied: (P1' - c) > b, P2' > 2a.

[0018] Optionally, P1' satisfies: 100 nm ≤ P1' ≤ 1000 nm; and / or, P2' satisfies: 100 nm ≤ P2' ≤ 1000 nm.

[0019] Optionally, in the thickness direction of the diffractive optical structure, the height of the biaxial structure is h1, and the height of the bar-shaped structure is h2; where, 10 nm ≤ h1 ≤ 1000 nm, 10 nm ≤ h2 ≤ 1000 nm.

[0020] Optionally, the bar-shaped structure is a stepped structure, which includes a first step and a second step, and the total height of the first step and the second step is h2; in the P1 direction, the width of the first step is b, and the width of the second step is c - b; where, c is the width of the bar-shaped structure in the P1 direction.

[0021] Optionally, the diffractive optical structure includes a first diffraction order K1 and a second diffraction order K2, where, K1 = 2π / Λ1, K2 = 2π / Λ2, Λ1 = P1', Λ2 = cos(tan-1(d / P1')) * P2'.

[0022] Optionally, when the first diffraction order K1 corresponds to the coupling-out order and the second diffraction order K2 corresponds to the pupil-expanding order, the coupling-out efficiency and / or the pupil-expanding efficiency of the diffractive optical structure are changed according to the parameter design of c and P1', 2a and P2', b and c, b and (P1'-c), h1 or h2.

[0023] In a second aspect, an embodiment of the present application provides a light guiding device. The light guiding device includes: a substrate and a light coupling-in area and a light coupling-out area disposed on the substrate; wherein, the light coupling-in area is a one-dimensional grating; the light coupling-out area is the diffractive optical structure as described in the first aspect.

[0024] Optionally, the light coupling-out area is composed of a plurality of different diffractive optical structures, and the plurality of diffractive optical structures are arranged and combined according to a target arrangement manner so that the light energy coupled out from each part of the light coupling-out area is uniform.

[0025] Optionally, the surface of the diffractive optical structure in the light coupling-out area is covered with a metal oxide film layer, and the thickness of the metal oxide film layer is 1 nm to 50 nm.

[0026] The present application provides a head-mounted display device. The head-mounted display device includes:

[0027] a housing; and

[0028] the light guiding device as described in the second aspect.

[0029] The beneficial effects of the present application are as follows:

[0030] According to the diffractive optical structure provided by the embodiment of the present application, for example, a two-dimensional grating applicable to an AR optical system, by designing the periodic repetition units in the P1 direction and the P2 direction, and the periodic unit in the P1 direction is a strip structure, and the periodic unit in the P2 direction is a biaxial structure with periodic addition or subtraction on the strip structure, such a diffractive optical structure has many adjustable parameters. After being applied to the light coupling-out area of the light guiding device, it can more flexibly control the coupling-out efficiency and / or the pupil-expanding efficiency, so as to realize the uniform propagation of imaging light.

[0031] Through the following detailed description of the exemplary embodiments of the present specification with reference to the accompanying drawings, other features and advantages of the present specification will become clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings incorporated in the specification and constituting a part of the specification illustrate the embodiments of the present specification, and together with the description are used to explain the principles of the present specification.

[0033] Figure 1 One of the top views of the diffractive optical structure provided by the embodiment of the present application;

[0034] Figure 2 The second top view of the diffractive optical structure provided by the embodiment of the present application;

[0035] Figure 3 The first cross-sectional view of the diffractive optical structure provided by the first embodiment of the present application;

[0036] Figure 4 The second cross-sectional view of the diffractive optical structure provided by the first embodiment of the present application;

[0037] Figure 5 The first cross-sectional view of the diffractive optical structure provided by the second embodiment of the present application;

[0038] Figure 6 The second cross-sectional view of the diffractive optical structure provided by the second embodiment of the present application;

[0039] Figure 7 The first cross-sectional view of the diffractive optical structure provided by the third embodiment of the present application;

[0040] Figure 8 The second cross-sectional view of the diffractive optical structure provided by the third embodiment of the present application;

[0041] Figure 9 The first cross-sectional view of the diffractive optical structure provided by the fourth embodiment of the present application;

[0042] Figure 10 The second cross-sectional view of the diffractive optical structure provided by the fourth embodiment of the present application;

[0043] Figure 11 The first cross-sectional view of the diffractive optical structure provided by the fifth embodiment of the present application;

[0044] Figure 12 The second cross-sectional view of the diffractive optical structure provided by the fifth embodiment of the present application;

[0045] Figure 13 The K diagram of the diffraction order of the optical diffraction structure provided by the embodiment of the present application;

[0046] Figure 14 The structural schematic diagram of the light guide device provided by an embodiment of the present application.

[0047] Explanation of reference numerals:

[0048] 1. Strip structure; 11. First step; 12. Second step; 2. Semi-elliptical structure; 3. Elliptical structure; 100. Substrate; 200. Coupling-in region; 300. Coupling-out region. Detailed implementation manners

[0049] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present application.

[0050] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way a limitation on the present application or its application or use.

[0051] Technologies and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies and devices should be regarded as part of the specification.

[0052] In all examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values.

[0053] It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, further discussion thereof is not required in subsequent drawings.

[0054] The diffractive optical structure, light guiding device, and head-mounted display device provided by the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0055] According to one aspect of the embodiments of the present application, a diffractive optical structure is provided, and the diffractive optical structure is applicable to an AR diffractive optical scheme.

[0056] The diffractive optical structure provided by the embodiments of the present application, see Figure 1 and Figure 2 , the diffractive optical structure includes repeating units periodically presented in the P1 direction and the P2 direction, and the periodic unit in the P1 direction is a bar structure 1, and the periodic unit in the P2 direction is a biaxial structure that adds or subtracts periodically on the bar structure 1; wherein, the biaxial directions of the biaxial structure respectively correspond to the P1 direction and the P2 direction, and the biaxial lengths of the biaxial structure are different.

[0057] The diffractive optical structure provided by the embodiments of the present application can be a grating structure applied to an AR optical system, such as a two-dimensional grating. By designing the diffractive optical structure to have repeating units periodically presented in the P1 direction and the P2 direction, with the periodic unit in the P1 direction being a bar structure 1 and the periodic unit in the P2 direction being a biaxial structure that adds or subtracts periodically on the bar structure 1. Here, the biaxial structure means that the figure has two axes with different length dimensions, such as a long axis and a short axis, and both the long axis and the short axis pass through the center point of the figure.

[0058] For example, see Figure 1 andFigure 2 , Figure 1 and Figure 2 The white parts in Figure 2 show the periodic bar structure 1 and the periodic semi-elliptical structure 2 of the diffractive optical structure. The formed diffractive optical structure has many adjustable parameters. Among them, the semi-elliptical structure 2 is one of the biaxial structures.

[0059] When the diffractive optical structure is applied to a light guiding device, such as its light extraction part, it can more flexibly control the light extraction efficiency and / or the pupil expansion efficiency, so as to realize the uniform propagation of imaging light (image), that is, the light energy extracted from each part of the light extraction area can be made uniform, which can improve the user's visual experience.

[0060] See Figure 1 and Figure 2 , where the P1 direction is the normal direction of the periodic bar structure 1 (i.e., bar stripes), and the P2 direction is perpendicular to the P1 direction. The two axes of the biaxial structure, i.e., the long axis and the short axis directions, can respectively correspond to the P1 direction and the P2 direction.

[0061] For example, the long axis corresponds to the P1 direction and the short axis corresponds to the P2 direction.

[0062] For another example, the short axis corresponds to the P1 direction and the long axis corresponds to the P2 direction.

[0063] The diffractive optical structure provided by the embodiments of the present application can be a diffractive grating, such as a two-dimensional grating, and can be applied to the light coupling part and / or the light extraction part of a diffractive optical waveguide element. When the diffractive optical structure provided by the embodiments of the present application is used in the light extraction part, it can not only expand the light but also realize the light extraction function. More importantly, at different positions within the light extraction part, different pupil expansion efficiencies and light extraction efficiencies can be made at different positions by adjusting parameters as needed, and there are many adjustable parameters among them.

[0064] For example, in the central area of the light extraction part, it is required to have both a high light extraction efficiency and a high pupil expansion efficiency, while in the edge area of the light extraction part, it is required to have a high light extraction efficiency and a low pupil expansion efficiency. The diffractive optical structure provided by the embodiments of the present application has many parameters included in its own structure, resulting in more adjustable parameters, and can flexibly meet the above requirements.

[0065] By using the diffractive optical structure provided by the embodiments of the present application, the light energy extracted from each area of the light extraction part can be made more uniform, and a better image transmission effect can be obtained.

[0066] However, most of the common two-dimensional gratings at present are square or circular, both of which are symmetric structures, with very few adjustable parameters, making it difficult to flexibly control the light extraction efficiency and the pupil expansion efficiency, and it is not conducive to realizing the uniform propagation of the image by adjusting the extracted energy.

[0067] In some examples of the present application, referring to Figures 3 to 8 , the biaxial structure includes a semi-elliptical structure 2 or an elliptical structure 3.

[0068] In an embodiment of the present application, the biaxial structure has a major axis and a minor axis. Among them, the major axis is the line segment connecting the two points farthest apart on the biaxial structure, and the minor axis is the line segment connecting the two points closest together on the biaxial structure.

[0069] For example, the elliptical structure 3 is a biaxial structure with different major and minor axis dimensions.

[0070] Also for example, the semi-elliptical structure 2 is half of the elliptical structure 3. The semi-elliptical structure 2 can be half along the major axis direction or half along the minor axis direction. The semi-elliptical structure is also a biaxial structure with different major and minor axis dimensions.

[0071] In some examples of the present application, referring to Figure 1 and Figure 2 , the center of the biaxial structure is located on one side edge of the bar-shaped structure 1.

[0072] For example, the center of the elliptical structure 3 or the semi-elliptical structure 2 is located on one side edge of the bar-shaped structure 1.

[0073] According to the above examples, referring to Figures 3 to 6 , when subtracting or adding periodic semi-elliptical structures 2 on the bar-shaped structure 1, the center of the semi-elliptical structure 2 should fall on one side edge of the bar-shaped structure 1, that is, the major axis or minor axis of the semi-elliptical structure 2 is in contact with one side edge of the bar-shaped structure 1. Such a structure is easy to control during processing, does not increase the processing difficulty of the diffractive optical structure, and at the same time can obtain more adjustable parameters.

[0074] In one example, referring to Figure 1 and Figure 3 , what they show is subtracting the semi-elliptical structure 2 on the bar-shaped structure 1, and the height h1 of the semi-elliptical structure 2 is less than the height h2 of the bar-shaped structure 1. At this time, the semi-elliptical structure 2 is embedded in the bar-shaped structure 1.

[0075] In one example, referring to Figure 4 , different from Figure 3 , the height h1 of the semi-elliptical structure 2 is greater than the height h2 of the bar-shaped structure 1. At this time, a part of the semi-elliptical structure 2 is embedded in the bar-shaped structure 1, and another part extends outside the bar-shaped structure 1.

[0076] In one example, referring to Figure 2 and5 Both show adding the semi - elliptical structure 2 to the bar - shaped structure 1, and the height h1 of the semi - elliptical structure 2 is less than the height h2 of the bar - shaped structure 1. At this time, the semi - elliptical structure 2 is located on the outer side of the bar - shaped structure 1 and is lower than the bar - shaped structure 1 in height.

[0077] In one example, see Figure 6 , and Figure 5 is different in that the height h1 of the semi - elliptical structure 2 is greater than the height h2 of the bar - shaped structure 1. At this time, the entire semi - elliptical structure 2 is located on the outer side of the bar - shaped structure 1 and exceeds the bar - shaped structure 1 in height.

[0078] When the biaxial structure is the elliptical structure 3, the center of the elliptical structure 3 should also be designed to be located on one side edge of the bar - shaped structure 1.

[0079] In some examples of the present application, when the periodic unit in the P2 direction is adding the periodic elliptical structure 3 to the bar - shaped structure 1, the bar - shaped structure 1 and the elliptical structure 3 have a partial overlapping area, and the overlapping area is semi - elliptical.

[0080] According to the above example, see Figure 7 and Figure 8 , when adding the periodic elliptical structure 3 to the bar - shaped structure 1, it can be controlled so that a part of the elliptical structure 3, such as a semi - elliptical structure, is embedded in the bar - shaped structure 1. At this time, there is also a semi - elliptical structure, that is, the semi - elliptical structure 2, exposed on one side of the bar - shaped structure 1. Such a structure is easy to control during processing, does not increase the processing difficulty of the diffractive optical structure, and at the same time, more adjustable parameters can be obtained.

[0081] In one example, see Figure 7 , Figure 7 shows adding the elliptical structure 3 to the bar - shaped structure 1, and the height h1 of the elliptical structure 3 is less than the height h2 of the bar - shaped structure 1. At this time, a part (semi - ellipse) of the elliptical structure 3 is embedded in the bar - shaped structure 1, and the other part is exposed outside the bar - shaped structure 1, and the elliptical structure 3 is lower than the bar - shaped structure 1.

[0082] In one example, see Figure 8 , and Figure 7 is different in that the height h1 of the elliptical structure 3 is greater than the height h2 of the bar - shaped structure 1. At this time, a part (semi - ellipse) of the elliptical structure 3 is embedded in the bar - shaped structure 1, and the other part is exposed outside the bar - shaped structure 1, and the elliptical structure 3 is higher than the bar - shaped structure 1 in height.

[0083] It should be noted that the elliptical structure 3 with subtractive periodicity and the elliptical structure 3 with additive periodicity on the strip structure 1 are almost the same in appearance, and will not be described repeatedly here.

[0084] In some examples of the present application, the periodic unit in the P2 direction is an elliptical structure 3 with additive or subtractive periodicity on the strip structure 1, and the center of any of the elliptical structures 3 is located on the same side edge of the strip structure 1. Alternatively, the periodic unit in the P2 direction is a semi-elliptical structure 2 with additive or subtractive periodicity on the strip structure 1, and the center of any of the semi-elliptical structures 2 is located on the same side edge of the strip structure 1.

[0085] According to the above examples, a periodic semi-elliptical structure is formed on one side of the strip structure 1. See Figure 1 and Figure 2 , which can reduce the processing difficulty and is also conducive to subsequent parameter regulation.

[0086] In some examples of the present application, see Figure 1 and Figure 2 , the period of the diffractive optical structure in the P1 direction is P1', and the period in the P2 direction is P2'; the major axis length of the biaxial structure is 2a, and the minor axis length of the biaxial structure is 2b; the width of the strip structure 1 is c; the minimum distance between the centers of the biaxial structures on adjacent strip structures 1 in the P2 direction is d; see Figure 1 , when the biaxial structure with subtractive periodicity is formed on the strip structure 1, it satisfies: c > b, P2' > 2a; see Figure 2 , when the biaxial structure with additive periodicity is formed on the strip structure 1, it satisfies: (P1' - c) > b, P2' > 2a.

[0087] According to the above examples, the diffractive optical structure has good diffraction efficiency and can improve the optical performance of the light guiding device applying the diffractive optical structure.

[0088] Among them, P1' satisfies: 100 nm ≤ P1' ≤ 1000 nm; and / or, P2' satisfies: 100 nm ≤ P2' ≤ 1000 nm. It can meet the optical requirements of most light guiding devices.

[0089] In some examples of the present application, see Figures 3 to 8 , in the thickness direction of the diffractive optical structure, the height of the biaxial structure is h1, and the height of the strip structure 1 is h2; where, 10 nm ≤ h1 ≤ 1000 nm, 10 nm ≤ h2 ≤ 1000 nm.

[0090] See Figure 3 and Figure 4, corresponding to the scheme of subtracting the bar structure 1 from the periodic semi-elliptical structure 2. See Figure 5 and Figure 6 , corresponding to the scheme of adding the bar structure 1 to the periodic semi-elliptical structure 2. See Figure 7 and Figure 8 , corresponding to the scheme of adding the bar structure 1 to the periodic elliptical structure 3. See Figures 3 to 8 , the height of the semi-elliptical structure 2 or the elliptical structure 3 is h1, and the height of the bar structure 1 is h2. Optionally, h1 can be greater than, equal to, or less than h2. In addition, the ranges of the heights h1 and h2 are both 10 nm to 1000 nm, meeting the requirements of most light guiding devices.

[0091] For example, when applying the diffractive optical structure to the light extraction area of the light guiding device, h1 and h2 in the diffractive optical structure can be designed to be unequal at this time, so as to reduce the light leakage efficiency in the light extraction area, thereby improving the light extraction efficiency and helping to protect the privacy of users.

[0092] It should be noted that light leakage refers to the light that is coupled out to the human eye on the side opposite to the AR glasses, and these lights will be observed by the people in front of the AR glasses wearer, thus causing privacy leakage.

[0093] In some examples of the present application, see Figures 9 to 12 , the bar structure 1 is a stepped structure, which includes a first step 11 and a second step 12, and the total height of the first step 11 and the second step 12 is h2; in the P1 direction, the width of the first step 11 is b, and the width of the second step 12 is c - b; where c is the width of the bar structure 1 in the P1 direction.

[0094] See Figures 9 to 12 , in which the bar structure 1 becomes two steps with a certain height.

[0095] Figure 9 It shows that the semi-elliptical structure 2 is subtracted from the first step 11 of the bar structure 1. The height h1 of the semi-elliptical structure 2 is the same as the height of the first step 11, and the height of the bar structure 1 is h2, and h2 is greater than h1. It can also be understood that the height of the semi-elliptical structure 2 is less than the height of the bar structure 1.

[0096] Figure 10 It shows that the semi-elliptical structure 2 is subtracted from the bar structure 1, and the difference from Figure 9 is that the height h1 of the semi-elliptical structure 2 is greater than the height h2 of the bar structure 1.

[0097] Figure 11Shown is that the elliptical structure 3 is added to the first step 11 of the bar structure 1. The height h1 of the elliptical structure 3 is the same as the height of the first step 11, while the height of the bar structure 1 is h2, and h2 is greater than h1. It can also be understood that the height of the elliptical structure 3 is less than the height of the bar structure 1.

[0098] Figure 12 Shown is that the elliptical structure 3 is added to the bar structure 1, which Figure 11 is different from that

[0099] in that the height h1 of the elliptical structure 3 is greater than the height h2 of the bar structure 1.

[0100] Optionally, h1 can be greater than, equal to, or less than h2.

[0101] Optionally, the ranges of both h1 and h2 are from 10 nm to 1000 nm.

[0102] In some examples of the present application, referring to Figure 13 , the diffractive optical structure includes a first diffraction order K1 and a second diffraction order K2, where K1 = 2π / Λ1, K2 = 2π / Λ2, Λ1 = P1', and Λ2 = cos(tan-1(d / P1')) * P2'.

[0103] Figure 13 This is the K diagram of the diffraction orders of the diffractive optical structure provided by the embodiment of the present application. The diffractive optical element is a two-dimensional grating. In this two-dimensional grating, due to the existence of multiple periodic structures, there will be diffraction orders in multiple directions, and these diffraction orders can all be represented by two basic diffraction vectors.

[0104] As shown in Fig. 13, the two basic diffraction orders in the diffractive optical structure are K1 and K2, where K1 = 2π / Λ1, K2 = 2π / Λ2, Λ1 = P1', and Λ2 = cos(tan-1(d / P1')) * P2'.

[0105] K3 = K1 + K2. In the diffraction waveguide architecture of the two-dimensional grating, K3 is the same as the vector of the coupling grating in the coupling region 200. K1 and K2 can correspond to the coupling-out order and the pupil-expanding order in the two-dimensional grating diffraction waveguide, and the coupling-out efficiency and pupil-expanding efficiency of the two-dimensional grating can be adjusted by various means.

[0106] In some examples of the present application, when the first diffraction order K1 corresponds to the outcoupling order and the second diffraction order K2 corresponds to the pupil expansion order, the outcoupling efficiency and / or pupil expansion efficiency of the diffractive optical structure can be changed according to the parameter design of c and P1', 2a and P2', b and c, b and (P1'-c), h1 or h2.

[0107] According to the above examples, the outcoupling efficiency and pupil expansion efficiency of the diffractive optical structure can be adjusted by various means, including: adjusting the ratio c / P1, adjusting the ratio 2a / P2, adjusting the ratio b / c, or b / (P1-c), and adjusting the size of h1 and h2.

[0108] Through the above method, when the diffractive optical structure is used in the outcoupling area, the outcoupling energy between the various areas in the outcoupling area can be made more uniform, thereby obtaining a better image transmission effect.

[0109] According to another aspect of the present application, the present application embodiment also provides a light guide device, see Figure 14 , the light guide device includes a substrate 100 and an in-coupling region 200 and an out-coupling region 300 disposed on the substrate; wherein the in-coupling region 200 is a one-dimensional grating; and the out-coupling region 300 is a diffractive optical structure as described above.

[0110] According to the light-guiding device provided in the above embodiment, the diffractive optical structure can be used in the outcoupling area 300, so that the outcoupling efficiency and pupil expansion efficiency can be more flexibly adjusted, thereby achieving uniform propagation of imaging light.

[0111] Wherein, the grating types in the coupling region 200 include rectangular grating, blazed grating, tilted grating, step grating, etc.

[0112] In some examples of the present application, the outcoupling region 300 is composed of a plurality of different diffractive optical structures, and the plurality of diffractive optical structures are arranged and combined in a target arrangement manner so that the light energy coupled out of each location of the outcoupling region 300 is uniform.

[0113] For an example, see Figure 14 , the out-coupling region 300 is an optical diffraction structure of the embodiment of the present application, with the center line of the coupling-in region 200 and the out-coupling region 300 as the first direction, and the second direction perpendicular to the first direction, and the out-coupling region 300 and the coupling-in region 200 are symmetrical in the second direction. In addition, in this example, the out-coupling region 300 can be divided into partitions in the first direction, and it can be seen that Figure 14 The outcoupling region 300 shown in is divided into a plurality of sub-regions ( Figure 14Six sub-areas are shown in the figure); the closer to the edge of the outcoupling area 300, the smaller the ratio of b / c (or b / (P1-c)) to 2a / P2, and conversely, the closer to the center of the outcoupling area 300, the larger the ratio of b / c (or b / (P1-c)) to 2a / P2. In this way, the edge outcoupling efficiency and the center pupil expansion efficiency are enhanced respectively, and the outcoupling energy is uniformly coupled everywhere in the outcoupling area 300.

[0114] In the above example, in the diffractive optical structure in the outcoupling region 300, h1 and h2 are designed to be unequal. This can reduce the light leakage efficiency of the outcoupling region 300, thereby improving the outcoupling efficiency and helping to protect the privacy of the user.

[0115] Optionally, grating partitioning can be performed in the second direction of the outcoupling region 300.

[0116] It should be noted that the partitions of the outcoupling area 300 include but are not limited to Figure 14 The method shown in can be flexibly adjusted as needed.

[0117] In some examples of the present application, the surface of the diffractive optical structure in the outcoupling region 300 is covered with a metal oxide film layer, and the thickness of the metal oxide film layer is 1nm to 50nm.

[0118] By covering the surface of the diffractive optical structure in the outcoupling region 300 with a metal oxide film layer, the diffraction efficiency can be improved.

[0119] Wherein, the metal oxide film layer can be plated on the surface of the diffractive optical structure.

[0120] Wherein, the metal oxide film layer includes but is not limited to titanium oxide (TiO2), aluminum oxide (Al2O3), silicon oxide (SiO2), etc.

[0121] The thickness of the metal oxide film layer will affect the diffraction efficiency and the thickness of the entire light guide device. Therefore, it needs to be reasonably controlled. The thickness of the metal oxide film layer is, for example, 1nm to 50nm.

[0122] According to another aspect of the present application, an embodiment of the present application further provides a head-mounted display device. The head-mounted display device includes a housing and the light guide device as described above.

[0123] The light guide device is, for example, a diffractive light waveguide element, which is disposed in the housing.

[0124] The head mounted display device includes AR smart glasses or AR smart helmets, etc., which are not limited in the embodiments of the present application.

[0125] For the specific implementation of the head-mounted display device according to the embodiments of the present application, reference may be made to the above embodiments of the diffractive optical structure and the light guide device. Therefore, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated herein one by one.

[0126] In the above embodiments, the differences between the embodiments are mainly described. As long as the different optimization features between the embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity of the text, it will not be elaborated herein.

[0127] Although some specific embodiments of the present application have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A diffractive optical structure, characterized in that: The invention comprises a repeating unit which is periodically presented in the P1 direction and the P2 direction, wherein the periodic unit in the P1 direction is a strip structure (1), and the periodic unit in the P2 direction is a biaxial structure which is periodically added or subtracted on the strip structure (1); The biaxial directions of the biaxial structure correspond to the P1 direction and the P2 direction respectively, and the biaxial lengths of the biaxial structure are different.

2. The diffractive optical structure according to claim 1, characterized in that: The biaxial structure comprises a semi-elliptical structure (2) or an elliptical structure (3).

3. The diffractive optical structure according to claim 1 or 2, characterized in that: The center of the biaxial structure is located on one side edge of the strip structure (1).

4. The diffractive optical structure according to claim 3, characterized in that: When the periodic unit in the P2 direction is a periodic elliptical structure (3) added to the strip structure (1), the strip structure (1) and the elliptical structure (3) have a partial overlapping area, and the overlapping area is semi-elliptical.

5. The diffractive optical structure according to claim 3, characterized in that: The periodic unit in the P2 direction is an elliptical structure (3) that is periodically added or subtracted from the strip structure (1), and the center of any of the elliptical structures (3) is located on the same side edge of the strip structure (1); or, The periodic unit in the P2 direction is a semi-elliptical structure (2) that is periodically added or subtracted from the strip structure (1), and the center of any of the semi-elliptical structures (2) is located on the same side edge of the strip structure (1).

6. The diffractive optical structure according to claim 3, characterized in that: The period of the diffractive optical structure in the P1 direction is P1', and the period of the diffractive optical structure in the P2 direction is P2'; The long axis length of the biaxial structure is 2a, and the short axis length of the biaxial structure is 2b; The width of the strip structure (1) is c; The minimum distance between the centers of the biaxial structures on any two adjacent strip structures (1) in the P2 direction is d; When a periodic biaxial structure is subtracted from the strip structure (1), the following conditions are satisfied: c>b, P2'>2a; When a periodic biaxial structure is added to the strip structure (1), the following conditions are satisfied: (P1'-c)>b, P2'>2a.

7. The diffractive optical structure according to claim 6, characterized in that: The P1' satisfies: 100nm≤P1'≤1000nm; and / or the P2' satisfies: 100nm≤P2'≤1000nm.

8. The diffractive optical structure according to claim 6, characterized in that: In the thickness direction of the diffractive optical structure, the height of the biaxial structure is h1, and the height of the strip structure (1) is h2; wherein 10nm≤h1≤1000nm, 10nm≤h2≤1000nm.

9. The diffractive optical structure according to claim 8, characterized in that: The strip structure (1) is a step structure, comprising a first step (11) and a second step (12), and the total height of the first step (11) and the second step (12) is h2; in the P1 direction, the width of the first step (11) is b, and the width of the second step (12) is cb; wherein c is the width of the strip structure (1) in the P1 direction.

10. The diffractive optical structure according to claim 6, characterized in that: The diffraction optical structure includes a first diffraction order K1 and a second diffraction order K2, wherein K1=2π / Λ1, K2=2π / Λ2, Λ1=P1', Λ2=cos(tan-1(d / P1'))*P2'.

11. The diffractive optical structure according to claim 10, characterized in that: When the first diffraction order K1 corresponds to the out-coupling order and the second diffraction order K2 corresponds to the pupil expansion order, the out-coupling efficiency and / or pupil expansion efficiency of the diffraction optical structure is changed according to the parameter design of c and P1', 2a and P2', b and c, b and (P1'-c), h1 or h2.

12. A light guide device, characterized in that: It comprises a substrate (100) and a coupling-in region (200) and a coupling-out region (300) arranged on the substrate; Wherein, the coupling-in region (200) is a one-dimensional grating; The outcoupling region (300) is a diffractive optical structure as claimed in any one of claims 1 to 11.

13. The light guide device according to claim 12, characterized in that: The outcoupling region (300) is composed of a plurality of different diffractive optical structures, and the plurality of diffractive optical structures are arranged and combined in a target arrangement manner so that the light energy coupled out at each location of the outcoupling region (300) is uniform.

14. The light guide device according to claim 13, characterized in that: The surface of the diffractive optical structure in the out-coupling region (300) is covered with a metal oxide film layer, and the thickness of the metal oxide film layer is 1 nm to 50 nm.

15. A head mounted display device, characterized in that: include: a housing; and A light guiding device as claimed in any one of claims 12 to 14.

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