Diffractive optical element and diffractive optical waveguide

Abstract

The embodiment of the invention discloses a diffractive optical element and a diffractive optical waveguide. The diffractive optical element comprises a substrate and a diffractive optical structure arranged on the substrate, the diffractive optical structure comprises repetitive units arranged in an array, each repetitive unit comprises a plurality of microstructures, and the microstructures can be arranged on the substrate to form a space optical structure with i rows, j columns and k layers, when difference design is carried out on a plurality of microstructures in each dimension in a space optical structure and angle or morphology difference exists between projection morphologies of at least any two adjacent microstructures on a substrate, the polarization sensitivity can be effectively reduced, the diffraction efficiency on light is remarkably improved, the structure acts in a diffraction optical waveguide, and the polarization sensitivity can be effectively improved. The energy utilization efficiency of the diffraction optical waveguide can be remarkably improved, the in-eye brightness is improved, and the light leakage brightness is reduced.

Description

Technical Field

[0001] The present invention relates to the field of optical technologies, and in particular, to a diffractive optical element and a diffractive optical waveguide. Background Art

[0002] In recent years, with the rapid development of virtual reality and augmented reality technologies, near-eye display devices have received increasing attention. In near-eye display devices, the grating waveguide display technology uses a diffraction grating to achieve the incidence, turning, and emergence of light, and uses the total internal reflection principle to achieve light transmission, conducting the image of a microdisplay to the human eye, and then seeing a virtual image.

[0003] Common diffraction gratings form periodic microstructures such as grooves and columns on the surface of a substrate through an etching process. Due to the clear directionality of the spatial arrangement of such structures, their optical response exhibits significant polarization dependence, that is, anisotropy. Taking a one-dimensional grating as an example: it has periodic modulation only in a single direction and no structural change in the orthogonal direction. This asymmetry further amplifies the difference in diffraction efficiency for light of different polarization states. The optical response of common diffraction gratings exhibits significant anisotropy. When the polarization direction of incident light is parallel to the grating period direction, the modulation effect of the structure on light is the strongest, and the diffraction efficiency reaches the peak value; when the polarization direction of incident light is perpendicular to the grating period direction, the modulation effect of the structure on light is significantly weakened, and the diffraction efficiency drops to the valley value.

[0004] For unpolarized light composed of randomly distributed full polarization states, its overall diffraction efficiency can be approximated as the average of the efficiencies of each polarization state. Due to the large difference in efficiency between the orthogonal polarization directions, the total diffraction efficiency of unpolarized light is often lower than the peak efficiency when a single polarization is incident. Summary of the Invention

[0005] Embodiments of the present invention provide a diffractive optical element and a diffractive optical waveguide, which break the polarization sensitivity of traditional one-dimensional gratings and achieve high diffraction efficiency modulation under TE / TM polarization and unpolarized light.

[0006] In a first aspect, embodiments of the present invention provide a diffractive optical element, including: a substrate, and a diffractive optical structure disposed on the substrate;

[0007] The diffractive optical structure includes repetitively arranged units arranged in an array. Each repetitively arranged unit includes a plurality of microstructures. The microstructures are micro-nano columnar structures. The plurality of microstructures can form a three-dimensional optical structure of i rows, j columns, and k layers on the substrate. i, j, and k are all positive integers. The plane formed by the intersection of the row direction and the column direction in the three-dimensional optical structure is parallel to the bottom surface of the substrate, and the depth direction is perpendicular to the bottom surface of the substrate;

[0008] Among them, there is a first difference and / or a second difference between the projected morphologies of at least any two adjacent microstructures in the spatial optical structure on the substrate. The first difference is that two adjacent projected morphologies are the same pattern and there is a relative rotation angle between them; the second difference is that two adjacent projected morphologies are different patterns.

[0009] In a second aspect, an embodiment of the present invention further provides a diffractive optical waveguide, including at least two functional diffractive regions and the diffractive optical element according to any one of the first aspect, wherein the diffractive optical element can be disposed in any functional diffractive grating region of the diffractive optical waveguide.

[0010] An embodiment of the present invention discloses a diffractive optical element and a diffractive optical waveguide. The diffractive optical element includes a substrate and a diffractive optical structure disposed on the substrate. The diffractive optical structure includes a repeated unit arranged in an array, and each repeated unit includes a plurality of microstructures. The plurality of microstructures can be arranged on the substrate to form a spatial optical structure with i rows, j columns, and k layers. When differential design is performed on the plurality of microstructures in each dimension in the spatial optical structure, and there is an angular or morphological difference between at least any two adjacent microstructures in the projected morphology on the substrate, each microstructure can transmit the polarized light corresponding to the polarization direction in the unpolarized light, thereby effectively reducing the polarization sensitivity and significantly improving the diffraction efficiency of light. Furthermore, when this structure is applied to the diffractive optical waveguide, it will significantly improve the energy utilization efficiency of the diffractive optical waveguide, increase the brightness of the light entering the eye, and reduce light leakage.

[0011] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0013] Figure 1 is a schematic structural diagram of the diffractive optical element proposed by the embodiment of the present invention;

[0014] Figure 2 is a schematic structural diagram of the difference between adjacent projected morphologies proposed by the embodiment of the present invention;

[0015] Figure 3 is a spatial optical structure with a single row of repeated units in the diffractive optical element proposed by the embodiment of the present invention;

[0016] Figure 4 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in an embodiment of the present invention;

[0017] Figure 5 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0018] Figure 6 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in yet another embodiment of the present invention;

[0019] Figure 7 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in still another embodiment of the present invention;

[0020] Figure 8 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0021] Figure 9 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in yet another embodiment of the present invention;

[0022] Figure 10 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in still another embodiment of the present invention;

[0023] Figure 11 It is a sectional view of the structure that only performs the first differential design in the depth direction proposed in an embodiment of the present invention;

[0024] Figure 12 It is a top view of the structure that only performs the first differential design in the depth direction proposed in an embodiment of the present invention;

[0025] Figure 13 It is a sectional view of the structure that only performs the first differential design in the depth direction proposed in another embodiment of the present invention;

[0026] Figure 14 It is a top view of the structure that only performs the first differential design in the depth direction proposed in another embodiment of the present invention;

[0027] Figure 15 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in still another embodiment of the present invention;

[0028] Figure 16 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in still another embodiment of the present invention;

[0029] Figure 17 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in still another embodiment of the present invention;

[0030] Figure 18 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0031] Figure 19 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0032] Figure 20 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0033] Figure 21 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0034] Figure 22 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0035] Figure 23 is Figure 22 a sectional view in the depth direction;

[0036] Figure 24 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0037] Figure 25 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0038] Figure 26 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0039] Figure 27 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0040] Figure 28 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0041] Figure 29 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention;

[0042] Figure 30 It is a schematic diagram of the diffractive optical waveguide structure proposed in an embodiment of the present invention;

[0043] Figure 31 It is a schematic diagram of the polarization direction of a traditional one-dimensional straight grating;

[0044] Figure 32It is a schematic structural diagram of a diffractive optical element proposed in an embodiment of the present invention;

[0045] Figure 33 It is a schematic diagram showing the relationship between the diffraction efficiency and polarization angle of a traditional one-dimensional straight grating;

[0046] Figure 34 It is a schematic diagram showing the relationship between the diffraction efficiency and polarization angle of a diffractive optical element proposed in an embodiment of the present invention, which is only designed differently in the depth direction;

[0047] Figure 35 It is a schematic diagram showing the relationship between the diffraction efficiency and polarization angle of a diffractive optical element proposed in an embodiment of the present invention, which is designed differently in both the row direction and the depth direction;

[0048] Figure 36 It is a schematic diagram showing the relationship between the diffraction efficiency and polarization angle of a diffractive optical element proposed in an embodiment of the present invention, which is designed differently in the row direction, column direction, and depth direction. Detailed implementation manners

[0049] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0050] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0051] Figure 1 It is a schematic structural diagram of a diffractive optical element proposed in an embodiment of the present invention, refer to Figure 1 , including: a substrate 10, and a diffractive optical structure disposed on the substrate 10;

[0052] The diffractive optical structure includes repeating units arranged in an array. Each repeating unit includes a plurality of microstructures 20, and the microstructures 20 are micro-nano columnar structures. The plurality of microstructures 20 can be arranged on the substrate 10 to form a three-dimensional optical structure with i rows, j columns, and k layers, where i, j, and k are all positive integers. The plane formed by the intersection of the row direction and the column direction in the three-dimensional optical structure is parallel to the bottom surface of the substrate 10, and the depth direction is perpendicular to the bottom surface of the substrate 10.

[0053] Among them, at least any two adjacent microstructures 20 in the three-dimensional optical structure have a first difference and / or a second difference in the projected morphology on the substrate 10. The first difference is that the two adjacent projected morphologies are the same pattern and there is a relative rotation angle between them, and the second difference is that the two adjacent projected morphologies are different patterns.

[0054] It should be noted that the diffractive optical structure is a periodic diffractive optical structure, and the periodicity of the diffractive optical structure is formed by the array arrangement of the repeating units. Specifically, after the repeating units are arranged in an array, a diffractive optical structure with a preset period value and a period direction can be formed, and this periodic diffractive optical structure can achieve a diffractive function.

[0055] Specifically, being able to achieve a diffractive function means that when this periodic diffractive optical structure is applied to a diffractive optical waveguide, if it is set in the coupling region of the waveguide, it can achieve diffracting a light beam into the substrate and performing total internal reflection transmission in the substrate; if it is set in the output region of the waveguide, it can achieve diffracting the light out of the waveguide. Accordingly, the period of this periodic diffractive optical structure can be determined according to the grating equation. The direction of this period can be any direction of this diffractive optical structure. For example, in a specific example, the direction of this period can be the row direction, the column direction, or the depth direction, etc. In addition, the direction of this period can also be any spatial direction of this diffractive optical structure, and this spatial direction can ultimately be vectorially decomposed into the row, column, or depth direction, or obtained by the vector sum of the row, column, or depth direction, specifically determined by the light propagation direction required during design.

[0056] The repeating unit is a three-dimensional optical structure with i rows, j columns, and k layers, and can be a one-row, one-column, one-stack, multiple-rows-and-multiple-columns, multiple-rows-and-multiple-stacks, multiple-columns-and-multiple-stacks, or multiple-rows-and-multiple-columns-and-multiple-stacks three-dimensional optical structure. The diffractive optical structure is formed by arraying based on this three-dimensional optical structure in the row direction, and / or the column direction, and / or the depth direction.

[0057] In order to improve the diffraction efficiency when unpolarized light passes through a diffractive optical element, in the embodiments of the present invention, in the repeating unit, a first difference and / or a second difference may be provided between any two adjacent microstructures. That is to say, the projected morphologies of at least any two adjacent microstructures on the substrate 10 are set differently, or the projected morphologies are the same but have a certain relative rotation angle. In this way, when unpolarized light passes through the diffractive optical element, due to the different polarization characteristics of the polarization components of the unpolarized light between adjacent microstructures, the polarization components of the unpolarized light that could not originally pass through the diffractive optical element can pass through the diffractive optical element. Thus, not only can the diffraction efficiency of the diffractive optical element be improved, but also the occurrence of light leakage can be avoided. That is to say, the diffractive optical structure formed by arranging the repeating units in an array can not only achieve the diffraction function of light, but also the differential design inside the repeating unit can improve the transmittance of unpolarized light.

[0058] The following explains the difference between adjacent microstructures. Before explaining the difference, the diffractive optical structure is first introduced, as Figure 1 shown, the substrate 10 can be a silicon wafer substrate, a glass substrate, a crystal substrate (such as silicon carbide) or a resin substrate, and the microstructures 20 can be formed on the substrate 10 by means of nanoimprinting, etching, etc. The microstructures 20 can be micro-nano columnar structures. The aforementioned row direction can be defined as Figure 1 the x direction in Figure 1 the y direction in Figure 1 the z direction in. Among them, the row direction can also be defined as the y direction, the column direction can be defined as the x direction, and the depth direction can be defined as the z direction. In this embodiment, the former definition is used for illustration.

[0059] Figure 2 is a schematic structural diagram of the difference between adjacent projected morphologies proposed in the embodiments of the present invention. Among them, the following understanding should be had for the first difference between adjacent microstructures: Refer to Figure 2 , Figure 2 only shows the states of adjacent microstructures for the purpose of explaining the difference, and it does not represent any diffractive optical structure in the embodiments of the present invention. Among them, Figure 2 the first microstructure 201 and the second microstructure 202 are arranged in the row direction in, and there is a first difference between the two. That is to say, their projected morphologies on the substrate 10 are the same, but there is a relative rotation angle between the two (such as Figure 2The quadrilateral projection morphologies in [reference] are the same in size and have a relative rotation angle between them); compared with the case where there is no difference between the first microstructure 201 and the second microstructure 202 and only a certain polarization component can pass through in unpolarized light, the first microstructure 201 and the second microstructure 202 with the first difference in this embodiment enable light of different polarization components in unpolarized light to pass through the diffractive optical element, so as to improve the diffraction efficiency.

[0060] Similarly, the following understanding should be had for the second difference: As Figure 2 the third microstructure 203 and the fourth microstructure 204 in [reference], there is a second difference in the arrangement in the row direction, that is, their projection morphologies on the substrate 10 are different, that is, although both are quadrilateral morphologies, their sizes are different. Or as Figure 2 the fifth microstructure 205 and the sixth microstructure 206 in [reference], there is a second difference in the arrangement in the row direction, that is, their projection morphologies on the substrate 10 are different, that is, one is a quadrilateral morphology and the other is a rectangular morphology. Compared with the case where there is no difference between adjacent microstructures and only a certain polarization component can pass through in unpolarized light, the microstructures with the second difference in this embodiment enable light of different polarization components in unpolarized light to pass through the diffractive optical element, so as to improve the diffraction efficiency.

[0061] The following understanding should be had for the coexistence of the first difference and the second difference: Continuing to refer to Figure 2 the seventh microstructure 207 and the eighth microstructure 208 in [reference], on the basis of having the second difference between the two, the eighth microstructure 208 has a certain deflection angle compared with the seventh microstructure 207. Thus, both of them simultaneously satisfy the first difference and the second difference. Similarly, for the ninth microstructure 209 and the tenth microstructure 210, on the basis of having the second difference between the two, there is a certain deflection angle between the ninth microstructure 209 and the tenth microstructure 210.

[0062] Therefore, by making at least any adjacent microstructures among the multiple microstructures 20 in the spatial optical structure have the first difference and / or the second difference, the diffraction efficiency of the diffractive optical element can be improved.

[0063] In some embodiments, the multiple microstructures 20 in the spatial optical structure can be regularly arranged.

[0064] Optionally, in at least one direction of the spatial optical structure, there is the first difference and / or the second difference between the projection morphologies of any two adjacent microstructures on the substrate.

[0065] When there is a difference in one direction, there are the following multiple situations:

[0066] There are differences in the row direction: The repeating unit can be a row of spatial optical structures, and the diffractive optical structure is formed by an array of a row of spatial optical structures. Exemplarily, in the case where the repeating unit includes a plurality of microstructures and the plurality of microstructures form a spatial optical structure, if i = 1, k = 1, and j>1, that is, a row of spatial optical structures is formed, and there is a first difference, or a second difference, or both a first difference and a second difference between the projected morphologies of any two adjacent microstructures in the row direction of this row of spatial optical structures on the substrate 10. This row of spatial optical structures can be repeatedly arrayed in the row direction as the smallest repeating unit, and / or in the column direction, and / or in the depth direction to form a periodic diffractive optical structure.

[0067] Exemplarily, Figure 3 is a spatial optical structure with a row as the repeating unit in the diffractive optical element proposed in an embodiment of the present invention. Figure 3 In it, the repeating unit presents with a first difference in the row direction. Figure 4 is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in an embodiment of the present invention. Figure 4 In the diffractive optical structure, it is arrayed with this repeating unit in the row direction, Figure 4 and only two repetitions in the row direction are shown in it. Figure 5 is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Figure 5 In the diffractive optical structure, it is arrayed with this repeating unit in the column direction, Figure 5 and only two repetitions in the column direction are shown in it. Figure 6 is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in yet another embodiment of the present invention. Figure 6 In the diffractive optical structure, it is arrayed with this repeating unit in both the row direction and the column direction, Figure 6 and two arrays in the row direction and multiple arrays in the column direction are shown in it. As Figure 6 shown, the spatial optical structure with a row as the repeating unit can form a periodic diffractive optical structure with periods Dx and Dy through arraying, and in the x direction, differential design is performed within the period Dx, and through this differential design, more polarization components in the unpolarized light can pass through, thereby improving the utilization efficiency of the unpolarized light and further increasing the diffraction efficiency of the diffractive optical structure. In addition, in the y direction, no differential design is made within the period Dy. Optionally, if the effect of pupil expansion needs to be achieved, the size of the period Dy can be determined according to the grating equation so as to enable the light to be expanded and transmitted in the y direction. That is to say, the size of the period Dy can be determined according to actual needs.

[0068] Figure 7 is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in yet another embodiment of the present invention. Among them,Figure 7 Shown is a schematic diagram of a diffractive optical structure after being arrayed with a spatial optical structure as one row and having a second difference in the row direction and the column direction. Among them, it is arrayed twice in the row direction and multiple times in the column direction. Figure 8 It is a schematic diagram of a diffractive optical structure in a diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 8 Shown is a schematic diagram of a diffractive optical structure after being arrayed with a spatial optical structure as one row and having a second difference in the row direction and the column direction. Among them, it is arrayed twice in the row direction and multiple times in the column direction. Figure 9 It is a schematic diagram of a diffractive optical structure in a diffractive optical element proposed in yet another embodiment of the present invention. Among them, Figure 9 Shown is a schematic diagram of a diffractive optical structure after being arrayed with a spatial optical structure as one row and having a first difference and a second difference in the row direction and the column direction. Among them, it is arrayed twice in the row direction and three times in the column direction.

[0069] Similarly, there is a difference in the column direction: the repeating unit can be a column of spatial optical structures, and the diffractive optical structure is formed by arraying a column of spatial optical structures. Exemplarily, in the case where the repeating unit includes a plurality of microstructures and the plurality of microstructures form a spatial optical structure, if i>1, k = 1, j = 1, that is, a column of spatial optical structures is formed, and there is a first difference, or a second difference, or both a first difference and a second difference between the projected morphologies of two adjacent microstructures in the column direction of the column of spatial optical structures on the substrate 10. This column of spatial optical structures can be repeatedly arrayed in the row direction, and / or in the column direction, and / or in the depth direction to form a diffractive optical structure as the smallest repeating unit.

[0070] Exemplarily, Figure 10 It is a schematic diagram of a diffractive optical structure in a diffractive optical element proposed in yet another embodiment of the present invention. Among them, Figure 10 Shown is a schematic diagram of a diffractive optical structure after being arrayed with a spatial optical structure as one column and having a first difference in the row direction and the column direction. Among them, it is arrayed multiple times in the row direction and twice in the column direction. As Figure 10As shown, a spatial optical structure with a single-column repeating unit can form a periodic diffractive optical structure with periods Dx and Dy after passing through an array. In the y-direction, differential design is performed within the period Dy. Through this differential design, more polarization components in unpolarized light can pass through, thereby improving the utilization efficiency of unpolarized light and further increasing the diffraction efficiency of the diffractive optical structure. In addition, in the x-direction, no differential design is performed within the period Dx. Optionally, if a pupil expansion effect needs to be achieved, the size of the period Dx can be determined according to the grating equation so that light can be expanded and transmitted in the x-direction. That is, the size of the period Dx can be determined according to actual needs. It should be noted that by interchanging the row and column coordinates of the single-row spatial optical structure in the foregoing embodiment, various examples of a single-column spatial optical structure can be obtained, which will not be elaborated here.

[0071] Similarly, there are differences in the longitudinal direction: the repeating unit can be a longitudinal spatial optical structure, and the diffractive optical structure is formed by an array of longitudinal spatial optical structures. Exemplarily, in the repeating unit including multiple microstructures, and when multiple microstructures form a spatial optical structure, if i = 1, k > 1, j = 1, a longitudinal spatial optical structure is formed. The projection morphologies of two adjacent microstructures of this longitudinal spatial optical structure in the depth direction on the substrate 10 have a first difference, or a second difference, or both a first difference and a second difference. This longitudinal spatial optical structure can be repeatedly arrayed in the row direction, and / or in the column direction, and / or in the depth direction as the smallest repeating unit to form a diffractive optical structure.

[0072] Exemplarily, Figure 11 is a cross-sectional view of a structure with only the first differential design in the depth direction proposed in an embodiment of the present invention, Figure 12 is a top view of a structure with only the first differential design in the depth direction proposed in an embodiment of the present invention. Refer to Figure 11 , in the row direction and in the column direction, each row and each column have only 1 microstructure. In the depth direction, each column has 6 microstructures. Among them, a first difference is set between adjacent layers. Refer to Figure 12 , the relative rotation angle between adjacent layers takes the center of each microstructure as the rotation origin. Figure 13 is a cross-sectional view of a structure with only the first differential design in the depth direction proposed in another embodiment of the present invention, Figure 14 is a top view of a structure with only the first differential design in the depth direction proposed in another embodiment of the present invention. Similar to Figure 14 and Figure 12 , adjacent layers have a first difference, and the relative rotation angle between adjacent layers takes the edge of each microstructure as the rotation origin.

[0073] Among them, only the second difference can be set in the depth direction, or the first difference and the second difference can be set simultaneously. The method can refer to the setting in the row direction and will not be elaborated here.

[0074] Figure 15 FIG. 4 is a schematic diagram of a diffractive optical structure in a diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 15 FIG. 5 shows a schematic diagram of the diffractive optical structure after being arrayed in the row direction and the column direction with a spatial optical structure as one column and having a first difference. Specifically, after an array of a column of spatial optical structures with a differential design in the depth direction, a periodic diffractive structure with periods Dx and Dy can be formed. By setting symmetric spatial optical structures (i.e., single-column spatial optical structures) within the periods in the x direction and the y direction, the utilization efficiency of unpolarized light composed of randomly distributed full polarization states is improved, thereby achieving high diffractive efficiency modulation and breaking the polarization sensitivity of traditional one-dimensional gratings (no structural change in the orthogonal direction). In addition, to achieve the diffractive function, the period Dy and the period Dx can be determined according to the grating equation. Whether the periods Dy and Dx are simultaneously designed to have a diffractive function can be determined according to the design requirements and will not be limited here.

[0075] When there are differences in two directions, the following situations exist:

[0076] Among them, the repeating unit can be a row-column spatial optical structure, and the diffractive optical structure is formed by an array of row-column spatial optical structures. Exemplarily, in the repeating unit including multiple microstructures and the multiple microstructures forming a spatial optical structure, if i>1, k = 1, j>1, that is, a multi-row and multi-column spatial optical structure is formed. There is a first difference between the projected morphologies of two adjacent microstructures in the row direction on the substrate 10, and there is a first difference between the projected morphologies of two adjacent microstructures in the column direction on the substrate 10. Or, there is a second difference in both the row and column directions. Or, both the row and column directions simultaneously have a first difference and a second difference. Or, there is a first difference in the row direction and a second difference in the column direction. Or, there is a second difference in the row direction and a first difference in the column direction. Or, there are a first difference and a second difference in the row direction and a first difference in the column direction. Or, there are a first difference and a second difference in the column direction and a first difference in the row direction. Or, there are a first difference and a second difference in the row direction and a second difference in the column direction. Or, there are a first difference and a second difference in the column direction and a second difference in the row direction. This row-column spatial optical structure can be repeatedly arrayed in the row direction, and / or in the column direction, and / or in the depth direction to form a diffractive optical structure as the smallest repeating unit.

[0077] Figure 16It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 16 The shown diffractive optical structure takes the spatial optical structure as a row-column optical structure and has a first difference in both the row and column directions, and is a schematic diagram after being arrayed in the row direction and the column direction. As Figure 16 shown, the spatial optical structure with the repeating unit as rows and columns can form a periodic diffractive optical structure with periods Dx and Dy after being arrayed, and differential designs are made within both the periods Dx and Dy. Through this differential design, the periodic diffractive optical structure not only has a diffractive function, but also allows more polarization components in unpolarized light to pass through, thereby improving the utilization efficiency of unpolarized light and further increasing the diffraction efficiency of the diffractive optical structure. In addition, the spatial optical structure with the repeating unit as rows and columns may also form a periodic structure with a period direction at a certain angle to the x direction (which can be called an oblique period) after being arrayed. That is to say, the period direction of the periodic diffractive optical structure is at a certain angle to the x direction, and the period size can be determined by the grating equation. Through this design, the light is transmitted in a preset direction after diffraction. In addition, the oblique period can also be orthogonally decomposed into periods in the x and y directions, and differential designs are made for the micro-nano structures within the periods in the x and y directions. Figure 17 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 17 The shown diffractive optical structure takes the spatial optical structure as a row-column optical structure and has a second difference in both the row and column directions, and is a schematic diagram after being arrayed in the row direction and the column direction. Figure 18 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 18 The shown diffractive optical structure takes the spatial optical structure as a row-column optical structure and has a first difference and a second difference in both the row and column directions, and is a schematic diagram after being arrayed in the row direction. Figure 19 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 19 The shown diffractive optical structure takes the spatial optical structure as a row-column optical structure and has a second difference in the row direction and a difference in the column direction, and is a schematic diagram after being arrayed in the row direction. Figure 20 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 20 The shown diffractive optical structure takes the spatial optical structure as a row-column optical structure and has a first difference and a second difference in the row direction and a difference in the column direction, and is a schematic diagram after being arrayed in the row direction. Figure 21 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 21Shown is a schematic diagram of a diffractive optical structure where the spatial optical structure is a row-column optical structure with a first difference and a second difference in the row direction, a second difference in the column direction, and after arraying in the row direction.

[0078] It should be noted that by interchanging the row-column coordinates of the row-column spatial optical structure in the foregoing embodiment, various examples of other row-column spatial optical structures can be obtained, which will not be elaborated here.

[0079] Similarly, the repeating unit can be a row-depth spatial optical structure, and the diffractive optical structure is formed by arraying the row-depth spatial optical structures. Exemplarily, in the repeating unit including multiple microstructures and the multiple microstructures forming a spatial optical structure, if i = 1, k > 1, j > 1, that is, a multi-column multi-longitudinal spatial optical structure is formed. There is a first difference between the projected morphologies of two adjacent microstructures in the row direction on the substrate 10, and there is a first difference between the projected morphologies of two adjacent microstructures in the depth direction on the substrate 10. Or there is a second difference in both the row-depth direction. Or there are both a first difference and a second difference in the row-depth direction. Or, there is a first difference in the row direction and a second difference in the depth direction. Or, there is a second difference in the row direction and a first difference in the depth direction. This row-depth spatial optical structure as the smallest repeating unit can be repeatedly arrayed in the row direction, and / or in the column direction, and / or in the depth direction to form a diffractive optical structure.

[0080] Exemplarily, Figure 22 is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Figure 23 is Figure 22 a cross-sectional view in the depth direction. Wherein, Figure 22 and Figure 23 shown is a schematic diagram of the diffractive optical structure where the spatial optical structure is a row-depth optical structure with a first difference in the row direction and a first difference in the depth direction, and after arraying in the row-column-depth direction. As Figure 23 shown, by respectively arranging micro-nano structures including multiple differential designs within the period Dx in the row direction and the period Dz in the depth direction, the utilization efficiency of the diffractive optical structure for non-polarized light is improved, and the energy is more concentrated in the preset direction, greatly enhancing the diffraction efficiency. In addition, after the row-depth spatial optical structure with this differential design is arrayed, an equivalent tilted grating with differential design within the period range can also be formed (such as Figure 23 the area between the black lines in).

[0081] It should be noted that for examples with other differences in the row direction and the depth direction, reference can be made to the description at the row-column structure, which will not be elaborated here.

[0082] Similarly, the repeating unit may be a column-depth spatial optical structure, and the diffractive optical structure is formed by an array of column-depth spatial optical structures. Exemplarily, in the case where the repeating unit includes a plurality of microstructures and the plurality of microstructures form a spatial optical structure, if i>1, k>1, and j = 1, a multi-row and multi-column spatial optical structure is formed. There is a first difference between the projected morphologies of two adjacent microstructures in the column direction on the substrate 10, and there is a first difference between the projected morphologies of two adjacent microstructures in the depth direction on the substrate 10. Or there is a second difference in the column-depth direction. Or there are both a first difference and a second difference in the column-depth direction. Or, there is a first difference in the column direction and a second difference in the depth direction. Or, there is a second difference in the column direction and a first difference in the depth direction. This column-depth spatial optical structure can be repeatedly arrayed in the row direction, and / or in the column direction, and / or in the depth direction as the smallest repeating unit to form a diffractive optical structure.

[0083] It should be noted that the examples in the column direction and the depth direction can refer to the examples in the row direction and the depth direction, and will not be elaborated here.

[0084] Among them, the repeating unit may be a row-column-depth spatial optical structure, and the diffractive optical structure is formed by an array of row-column-depth spatial optical structures. Exemplarily, in the case where the repeating unit includes a plurality of microstructures and the plurality of microstructures form a spatial optical structure, if i>1, k>1, and j>1, a multi-row, multi-column, and multi-depth spatial optical structure is formed. In the row direction, there is a first difference, a second difference, or one of the first difference and the second difference. In the column direction, there is a first difference, a second difference, or one of the first difference and the second difference. In the depth direction, there is a first difference, a second difference, or one of the first difference and the second difference. This row-column-depth spatial optical structure can be repeatedly arrayed in the row direction, and / or in the column direction, and / or in the depth direction as the smallest repeating unit to form a diffractive optical structure.

[0085] Figure 24 It is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 24 What is shown is a schematic diagram after the diffractive optical structure is a row-column-depth optical structure in the spatial optical structure and has a first difference in the row-column-depth direction and is arrayed in the row-column-depth direction. As Figure 24As shown, a plurality of micro-nano structures are provided within a period Dx in the x direction, a period Dy in the y direction, and a period Dz in the z direction, and there is a first differential design between the plurality of micro-nano structures in each direction. Through this design, the utilization efficiency of unpolarized light is effectively improved, and the diffraction efficiency is increased. Moreover, when this diffractive optical structure is applied to the coupling-out region of a diffractive optical waveguide, it can achieve the export of more energy in a single direction, and thus more energy is exported to the human eye, effectively reducing light leakage.

[0086] It should be noted that the differences in the three directions of row, column, and depth can be set independently. The part in the aforementioned dashed block diagram can be understood as a repeating unit. Among them, repeating in the row direction can form a row period in the row direction. Repeating in the column direction can form a column period in the column direction, and repeating in the depth direction can form a depth period in the depth direction. When repeating in two or more directions of row, column, and depth, a spatial period may be formed in space due to the repetition in multiple directions (that is, the periods in other directions, which can be decomposed into the row direction and the column direction through vector decomposition).

[0087] In some embodiments, the plurality of micro-structures 20 in the spatial optical structure can be arranged irregularly.

[0088] Optionally, in the same direction of the spatial optical structure, the types of differences between adjacent rows, or adjacent columns, or adjacent columns are different.

[0089] That is to say, when i>1 and j>1, the types of differences between the rows in the spatial optical structure are different. Or, when i>1 and j>1, the types of differences between the columns in the spatial optical structure are different. Or, when k>1 and i>1, or when k>1 and j>1, the types of differences between the columns in the spatial optical structure are different.

[0090] Among them, there are three types of difference types in the embodiments of the present invention. The first is the first difference, the second is the second difference, and the third is the first difference and the second difference. Taking the different types of differences between the rows as an example for description, the differences between the columns and the differences between the columns are referred to the description of the differences between the rows.

[0091] It can be understood that when the types of differences between the rows in the spatial optical structure are different, the spatial optical structure has two or three rows. When there are two rows, there is a first difference between adjacent projection morphologies in the first row, and a second difference between adjacent projection morphologies in the second row. When there are three rows, there is a first difference between adjacent projection morphologies in the first row, a second difference between adjacent projection morphologies in the second row, and a first difference and a second difference between adjacent projection morphologies in the third row. The differences in this embodiment are more complex, which is more conducive to improving the diffraction efficiency.

[0092] The diffractive optical structure can be arrayed in the row direction, and / or column direction, and / or depth direction of the spatial optical structure.

[0093] Exemplarily, Figure 25 is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 25 shown is the schematic diagram after the diffractive optical structure is arrayed in the row and column directions with the spatial optical structure as the row-column optical structure, where in the row direction, one row has a first difference, one row has a second difference, and the diffractive optical structure is arrayed in the row and column directions. Figure 26 is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 26 shown is the schematic diagram after the diffractive optical structure is arrayed in the row and column directions with the spatial optical structure as the row-column optical structure, where in the row direction, one row has a second difference, one row has both a first difference and a second difference, and the diffractive optical structure is arrayed in the row and column directions. Figure 27 is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 27 shown is the schematic diagram after the diffractive optical structure is arrayed in the row and column directions with the spatial optical structure as the row-column optical structure, where in the row direction, one row has a first difference, one row has a second difference, one row has both a first difference and a second difference, and the diffractive optical structure is arrayed in the row and column directions.

[0094] Optionally, the types of differences in a single row or single column, or single vertical column of the spatial optical structure can be different.

[0095] It can be understood that there are three types of difference types in the embodiments of the present invention. The first is the first difference, the second is the second difference, and the third is the first difference and the second difference. The following will be described with the differences in a single row as an example, and the description of a single row can be referred to for a single column or single vertical column.

[0096] Among them, when the types of differences in a single row are different, there can be two or three types of differences in a single row. When there are two types of differences, there are at least 3 microstructures in each row. Among the 3 microstructures in a single row, the projection morphologies between the first two microstructures are the first difference, the projection morphologies between the last two microstructures are the second difference, or the projection morphologies between the first two microstructures are the first difference and the second difference, and the projection morphologies between the last two microstructures are the first difference. Or, the projection morphologies between the first two microstructures are the first difference, the projection morphologies between the last two microstructures are the first difference and the second difference, or the positions corresponding to different difference types can be interchanged.

[0097] When there are three types of differences, there are at least 5 microstructures in each row. Among them, there is a first difference between the projected morphologies of the first two microstructures, a second difference between the projected morphologies of the last two microstructures, a first difference and a second difference between the projected morphologies of the middle two microstructures, or the positions corresponding to different difference types can be interchanged.

[0098] Among them, when the differences between the projected morphologies of the microstructures in the same row are the same, the preparation difficulty will be reduced. However, when the differences between the projected morphologies of the microstructures in the same row are complex, it has certain advantages for improving the diffraction efficiency of the diffractive optical element.

[0099] Exemplarily, Figure 28 is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 28 shows a schematic diagram of the diffractive optical structure after the diffractive optical structure is a row-column optical structure with a spatial optical structure and in the row direction, there is a first difference between some microstructures in a row and a second difference between some microstructures, and after being arrayed in the row-column direction. Diagrams of other different difference types can be analogized and will not be elaborated here.

[0100] Among them, when the difference types within a single row in the spatial structure are different, the difference types between rows being different can also be interpreted as the different arrangement orders of the difference types within each single row between adjacent rows. Exemplarily, Figure 29 is a schematic diagram of the diffractive optical structure in the diffractive optical element proposed in another embodiment of the present invention. Among them, Figure 29 shows a schematic diagram of the diffractive optical structure after the diffractive optical structure is a row-column optical structure with a spatial optical structure and in the row direction, there is a first difference between some microstructures in a row and a second difference between some microstructures, and the difference types between adjacent rows are different, and after being arrayed in the row-column direction.

[0101] Optionally, in the diffractive optical structure, if in the column direction, there are columns with exactly the same projected morphology, then there is also a first difference between the projected morphologies of each column, or if in the row direction, there are rows with exactly the same projected morphology, then there is also a first difference between the projected morphologies of each row, or if in the depth direction, there are longitudinal sections with exactly the same projected morphology, then there is also a first difference between the projected morphologies of each longitudinal section.

[0102] Taking the column direction as an example, the other directions can refer to the description of this direction. Among them, taking Figure 26 and Figure 28 as examples, Figure 26 the projected morphologies in the first column in Figure 28The projected morphologies of each column are exactly the same. Furthermore, a first difference can be set in the column direction. By further increasing the difference in the diffractive optical structure, the diffraction efficiency of unpolarized light can be improved.

[0103] Optionally, when the projected morphologies in any one of the row direction, column direction, and depth direction have a first difference, the multiple relative rotation angles change in sequence along a preset curve in the corresponding direction.

[0104] That is, in the spatial optical structure, when the projected morphologies of adjacent microstructures in any one of the row direction, column direction, and depth direction have a first difference, the relative rotation angle between adjacent microstructures should satisfy the regulation of the preset curve, which is beneficial to the design of the spatial optical structure. The preset curves according to which the multiple relative rotation angles in any direction change can be the same or different. Exemplarily, the change curves in the row direction, column direction, and depth direction are all the same, or, the change curves in any two directions are the same and different in the other direction, or, the three directions are all different.

[0105] Optionally, when the projected morphologies in at least two of the row direction, column direction, and depth direction have a first difference, the preset curves corresponding to the sequential changes of the multiple relative rotation angles in different directions are different.

[0106] That is, in the spatial optical structure, when the projected morphologies in two of the row direction and column direction, row direction and depth direction, or column direction and depth direction have a first difference, or when the projected morphologies in all three of the row direction, column direction, and depth direction have a first difference, the relative rotation angle between adjacent microstructures in a certain direction should satisfy the first preset curve, while the relative rotation angle between adjacent microstructures in another direction can satisfy the second preset curve, and the first preset curve is different from the second preset curve.

[0107] Among them, when the preset curves in each direction are the same, it is beneficial to simplify the design steps. When the preset curves in each direction are different, it is beneficial to increase the transmittance of different direction polarization components in each direction.

[0108] Optionally, the preset curve is one of a constant function, a linear function, a trigonometric function, or an exponential function. That is to say, when the microstructures in any one of the directions satisfy the first difference, the angle difference between adjacent microstructures follows a specific function feature.

[0109] In an embodiment, if the preset curve is a constant function, the angle difference between adjacent microstructures is constant. When in any one of the three directions of row, column, and depth, as shown in Figure 3 When the spatial optical structure includes m microstructures in the row direction, the relationship between the angle difference θ between adjacent microstructures and the number m of microstructures is:

[0110]

[0111] This formula clarifies the relationship between the rotation angle and the number of microstructures under the design of a constant function. When the number of microstructures m increases, the rotation angle of each adjacent microstructure decreases to ensure that the total rotation of all microstructures within the entire period is a complete circle. Since the angular difference θ is determined by the number of microstructures m within the period, there are independent rotation angles between the microstructures in the row direction, column direction, and depth direction. The subscripts x, y, z in the formula represent different directions.

[0112] In another embodiment, if the preset curve is a linear function, the angular differences between adjacent microstructures show a linearly increasing relationship. When in any one of the three directions of row, column, and depth, referring to Figure 3 As shown, when the spatial optical structure contains m microstructures in the row direction, that is, within the period, the relationship between the angular difference θ between adjacent microstructures and the number of microstructures m is:

[0113]

[0114] This formula clarifies the relationship between the rotation angle and the number of microstructures under the design of a linear function. For example, when m = 5, the angular differences between adjacent microstructures are 24°, 48°, 72°, 96°, and 120° in sequence. Among them, △θ is the difference between adjacent angular differences, and the subscripts x, y, z in the formula represent different directions. is the difference between the nth microstructure and the (n - 1)th microstructure in the row direction. is the difference between the nth microstructure and the (n - 1)th microstructure in the column direction. is the difference between the nth microstructure and the (n - 1)th microstructure in the depth direction.

[0115] In yet another embodiment, if the preset curve is the sine function in trigonometric functions, the angular differences between adjacent microstructures show an increasing relationship. When in any one of the three directions of row, column, and depth, referring to Figure 3 As shown, when the spatial optical structure contains m microstructures in the row direction, the relationship between the angular difference θ between adjacent microstructures and the number of microstructures m is:

[0116]

[0117] Among them, α is a constant. The subscripts x, y, z in the formula represent different directions. is the difference between the nth microstructure and the (n - 1)th microstructure in the row direction. is the difference between the nth microstructure and the (n - 1)th microstructure in the column direction. is the difference between the nth microstructure and the (n - 1)th microstructure in the depth direction.

[0118] In another embodiment, if the preset curve is an exponential function, the angular differences between adjacent microstructures show an increasing relationship. When in any one of the three directions of row, column, and depth, referring to Figure 3 as shown, when the spatial optical structure includes m microstructures in the row direction, the relationship between the angular difference θ between adjacent microstructures and the number m of microstructures is:

[0119]

[0120] where α is a constant. The subscripts x, y, z in the formula represent different directions. is the difference between the nth microstructure and the (n - 1)th microstructure in the row direction. is the difference between the nth microstructure and the (n - 1)th microstructure in the column direction. is the difference between the nth microstructure and the (n - 1)th microstructure in the depth direction.

[0121] It can be understood that the diffraction period of the diffractive optical structure is generally the same as the repetition period of the spatial optical structure. In the above embodiments of the preset curve, the diffraction period of the diffractive optical structure is generally determined to meet the diffraction of light. However, the number of microstructures within this diffraction period and the size of the microstructures themselves are not fixed. If the size of the microstructures themselves is large, then the number may be set less; if the size of the microstructures themselves is small, then the number may be set more. And, in order to satisfy to a certain extent that the polarization components of unpolarized light in all directions can pass through this optical element, within the diffraction period of the diffractive optical structure, as many deflection directions of the microstructures as possible will be set.

[0122] It should also be noted that the preset curve can also be other functions. By setting each preset curve, the design freedom can be increased.

[0123] In some preferred embodiments, a first difference is set in the row direction, column direction, and depth direction. And the projected morphologies of the microstructures used in each direction on the substrate are the same, and the preset curves used for the change of the first difference of the microstructures in each direction are also the same.

[0124] Exemplarily, such as Figure 24As shown, the spatial optical structure includes an i-row, j-column, and k-layer spatial optical structure. Starting from the microstructure at the point (1, 1, 1), in the row direction, the projected morphologies of the microstructures change with counterclockwise rotation. In the column direction, the projected morphologies of the microstructures change with counterclockwise rotation. In the depth direction, the projected morphologies of the microstructures change with counterclockwise rotation. The angular difference changes between the projected morphologies of the microstructures in each direction are all the same. In this way, periodic arrangements can also be presented in some spatial directions of the spatial optical structure. For example, taking Figure 24 as an example, corresponding repeating periods appear in the inclined direction in Figure 24 . The size of the repeating period can also be set as the diffraction period of the diffractive optical structure under certain conditions to satisfy the diffraction of the optical structure in the inclined direction. Thus, different optical products can be adapted.

[0125] In other embodiments, when arranged differently from the above preferred examples, periodic arrangements may also appear in some inclined directions in space. Furthermore, when actually designing a diffractive optical element, corresponding period sizes can be set to perform diffraction in the row, column, and depth directions, or corresponding period sizes can be set to perform diffraction in the spatial inclined direction to meet the diffraction requirements in different diffraction directions.

[0126] Optionally, the projected morphology of the micro-nano columnar structure on the substrate is a regular pattern or an irregular free pattern. Among them, when the arrangements of the projected morphologies have a first difference, the regular pattern is not a circle.

[0127] Its projected morphology includes, but is not limited to, micro-nano structure morphologies such as rectangles, rhombuses, ellipses, etc. As Figure 2 shown, the projected morphologies of the first microstructure 201 and the second microstructure 202 on the substrate 10 have a first difference, and their projected morphologies on the substrate 10 are rhombuses. If the projected morphology on the substrate 10 is a circle, the significance of whether there is a first difference between adjacent microstructures is lost. The projected morphologies of the third microstructure 203 and the fourth microstructure 204 on the substrate 10 have a second difference. The projected morphology of the third microstructure 203 on the substrate 10 is a rhombus, and the projected morphology of the fourth microstructure 204 on the substrate 10 is a rhombus. At this time, since the projected morphologies of adjacent microstructures on the substrate 10 are different, with the same shape but different sizes. If the projected morphology of the third microstructure 203 on the substrate 10 is a rhombus and the projected morphology of the fourth microstructure 204 on the substrate 10 is a circle, there is also a second difference between the two. Furthermore, the circle does not affect the judgment of whether there is a second difference.

[0128] Optionally, the dimensions (length and width) of each microstructure range from 10 nm to 800 nm, and the height ranges from 50 nm to 2 μm. To facilitate determining the number of micro-nano structures included in one period of the diffractive optical structure, in this embodiment, the modulation dimensions of each microstructure are set. Specifically, each microstructure has length, width, and height in space, and there are corresponding gaps between adjacent microstructures in the row and column directions. There may be other dielectric layers, air, or direct overlap between adjacent microstructures in the depth direction, which is designed according to actual requirements. Among them, in the row direction, the modulation dimension of the current microstructure in terms of length is the sum of the projected dimension of the current microstructure itself in the row direction and the gap before the next microstructure. In the column direction, the modulation dimension of the current microstructure in terms of width is the sum of the projected dimension of the current microstructure itself in the column direction and the gap before the next microstructure. In the depth direction, the modulation dimension of the current microstructure in terms of height is the distance from the side of the projected dimension of the current microstructure in the depth direction away from the next microstructure to the side of the next microstructure close to the current microstructure.

[0129] Optionally, the period of the diffractive optical structure ranges from 100 nm to 30 μm, and the number of microstructures included in each period is 2 - 60. It should be noted that independent period settings can be made in the row direction, column direction, and depth direction respectively, that is, there can be independent periods, microstructure modulation dimensions, and the number of microstructures in the row direction, column direction, and depth direction.

[0130] Among them, the relationship between the period D of the diffractive optical structure in each direction, the modulation dimension d of the microstructure, and the number m of microstructures can be:

[0131]

[0132] This formula clarifies the relationship between the period of the diffractive optical structure, the microstructure size, and the number. The period length of the diffractive optical structure is equal to the modulation dimension of each microstructure in that period multiplied by the number of microstructures.

[0133] The embodiment of the present invention also provides a diffractive optical waveguide, including at least two functional diffractive regions and the diffractive optical element in any one of the above embodiments, where the diffractive optical element can be disposed in any functional diffractive region of the diffractive optical waveguide.

[0134] Figure 30Schematic diagram of a diffractive optical waveguide structure proposed in an embodiment of the present invention, including a substrate 10, the substrate 10 can be a glass substrate, a resin substrate or a crystal substrate (such as silicon carbide, etc.), and at least two functional diffractive regions on the substrate 10, that is, at least including an input grating region 30 (with a period of DT1) and an output grating region 40 (with a period of DT2), and there may also be a turning region according to the situation, where at least one region is a diffractive optical element in any one of the above embodiments, and the diffractive optical element has a microstructure 20.

[0135] Among them, due to different requirements such as the diffraction direction of each functional diffractive region, a diffractive optical element that can match and adapt to the diffraction direction can be selected.

[0136] Optionally, when a diffractive optical element in any one of the above embodiments is provided in at least one functional diffractive region of the diffractive optical waveguide, the period of the diffractive optical element set in one of the row direction and the column direction is less than λ / 2n, or the periods of the diffractive optical element set in both the row direction and the column direction are greater than λ / n, where n is the refractive index of the waveguide substrate and λ is the specified ray wavelength.

[0137] It should be noted that setting the period less than λ / 2n in one of the row direction and the column direction of the diffractive optical element means that the period in one of the directions cannot achieve the diffraction function, that is, only the period in one direction can achieve the diffraction function, which can be equivalent to a one-dimensional grating. However, due to the differential design within the period range of the diffractive optical element, compared with the traditional one-dimensional grating, more unpolarized light can pass through, so it can have a higher diffraction efficiency. Setting the periods in both the row direction and the column direction of the diffractive optical element to be greater than λ / n means that the periods in both directions can achieve the diffraction function, which can be equivalent to a two-dimensional grating. Similarly, due to the differential design within the period range, it has a higher diffraction efficiency compared with the traditional two-dimensional grating.

[0138] Exemplarily, Figure 31 is a schematic diagram of the polarization direction of a traditional one-dimensional straight grating. Since any non-linearly polarized light can be decomposed into the sum of a pair of orthogonally polarized light rays, when the traditional grating faces this pair of orthogonally polarized light rays, due to the large difference in the morphology of the traditional grating in the orthogonal direction, the traditional grating shows anisotropy, resulting in a large difference in the efficiency of light rays with different polarization directions. Figure 32 is a schematic diagram of the structure of a diffractive optical element proposed in an embodiment of the present invention, as Figure 32As shown, in the row direction, there is a first difference between adjacent microstructures. And when the period in the row direction (or column direction) is less than λ / 2n (that is, the period set in the row direction does not meet the requirements of light diffraction), this diffractive optical element can not only meet the requirements of diffraction in the column direction (row direction), but also meet the requirements of transmitting light with different polarization directions, and the diffraction efficiency is higher. When the periods in both the row direction and the column direction are greater than λ / n, this diffractive optical element can not only meet the requirements of diffraction in the row direction and the column direction, but also meet the requirements of transmitting light with different polarization directions, and the diffraction efficiency is higher.

[0139] Reference Figure 6 、 Figure 10 and Figure 15 , when the microstructures coupled into the grating region 30 are the above-mentioned diffractive optical elements and are designed with differences only in a single direction, that is, only in the row direction, column direction or depth direction, the utilization efficiency of unpolarized light in the grating region coupled in can be improved, and more energy can be transmitted into the waveguide; when the microstructures in the grating region 40 coupled out are the above-mentioned diffractive optical elements and are designed with differences only in a single direction, that is, only in the row direction, column direction or depth direction, the utilization efficiency of unpolarized light in the grating region coupled out can also be improved, and more energy can be exported to the human eye.

[0140] Figure 33 is a schematic diagram of the relationship between the diffraction efficiency and the polarization angle of a traditional one-dimensional straight grating. Among them, the substrate and the structure refractive index of the traditional one-dimensional straight grating are 2.0, the period is 300 nm, the duty cycle is 70%, and the height is 450 nm. Diffraction is performed using 532 nm light with different polarization angles, and the relationship curve as shown in Figure 33 is obtained.

[0141] Figure 34 is a schematic diagram of the relationship between the diffraction efficiency and the polarization angle of a diffractive optical element designed with differences only in the depth direction proposed in an embodiment of the present invention. Among them, as shown in Figure 15 , for the diffractive optical element designed with differences only in the depth direction, the substrate and the structure refractive index are 2.0, the microstructure size is 210 nm * 50 nm, no difference design is made in the row direction of the period, the period size Dx in the row direction is 300 nm; no difference design is made in the column direction, the period size Dy in the column direction is 60 nm; difference design is made in the z direction, the period size Dz in the depth direction is 450 nm, the microstructure height size dz is 50 nm, and the number mz is 9. Diffraction is performed using 532 nm light with different polarization angles, and the relationship curve as shown in Figure 34 is obtained.

[0142] Therefore, the diffractive optical element provided in this embodiment, which only makes differential designs in the depth direction, can effectively reduce the diffraction efficiency gap of light rays with different polarization angles. Compared with the traditional one-dimensional straight grating with the same period, the efficiency gap is reduced from 4.1% (from 4.3% to 0.2%) to 1.5% (from 5.8% to 4.3%), and at the same time, the diffraction efficiency is significantly improved.

[0143] Reference Figure 16 and Figure 22 , when the microstructure coupled into the grating region 30 is the above diffractive optical element and differential designs are made simultaneously in the depth direction and the row direction, or in the depth direction and the column direction, or in the row direction and the column direction, the utilization efficiency of unpolarized light by the grating region coupled in can be further improved, and the energy can be more concentrated in the positive direction of the grating region coupled in, greatly improving the utilization efficiency; when the microstructure of the grating region 40 coupled out is the above diffractive optical element and differential designs are made simultaneously in the depth direction and the row direction, or in the depth direction and the column direction, or in the row direction and the column direction, the utilization efficiency of unpolarized light by the grating region coupled out can also be further improved, and more energy can be exported in a single direction, enabling more energy to be exported to the human eye and effectively reducing light leakage.

[0144] Figure 35 is a schematic diagram showing the relationship between the diffraction efficiency and the polarization angle of the diffractive optical element that makes differential designs in both the row direction and the depth direction proposed in the embodiment of the present invention. Among them, reference Figure 22 shows that the substrate and the structural refractive index of the diffractive optical element are 2.0, the microstructure size is 210nm * 50nm, differential design is made in the x direction, the period size Dx in the row direction is 300nm, the microstructure size dx is 60nm, and mx is 5; no differential design is made in the y direction, the period size Dy in the column direction is 60nm, differential design is made in the z direction, the period size Dz in the depth direction is 450nm, the microstructure size dz is 50nm, and mz is 9; diffraction is performed using 532nm light with different polarization angles, and the relationship curve as shown in Figure 35 is obtained.

[0145] Therefore, the diffractive optical element provided in this embodiment, which makes differential designs in both the row direction and the depth direction, can effectively reduce the diffraction efficiency gap of light rays with different polarization angles, and the +1 - order diffraction efficiency is greater than the - 1 - order diffraction.

[0146] Reference Figure 24 , when the microstructure of the grating region 40 coupled out is the above diffractive optical element and differential designs are made simultaneously in the three directions of the row direction, the column direction, and the depth direction, the utilization efficiency of unpolarized light by the grating region coupled out can be improved, and more energy can be exported in a single direction, enabling more energy to be exported to the human eye and effectively reducing light leakage.

[0147] Exemplarily, Figure 36 is a schematic diagram of the relationship between the diffraction efficiency and the polarization angle of a diffractive optical element with differential design in the row direction, column direction, and depth direction proposed in an embodiment of the present invention. The substrate and the structural refractive index of the diffractive optical element are 2.0, the microstructure size is 50nm * 30nm, differential design is performed in the x direction, the period Dx is 300nm, the microstructure dx is 60nm, and mx is 5; differential design is performed in the y direction, the period Dy is 350nm, the microstructure dy is 50nm, and my is 7; differential design is performed in the z direction, the period Dz is 450nm, the microstructure dz is 50nm, and mz is 9. Diffraction is performed using 532nm light with different polarization angles, and the relationship curve as shown in Figure 36 is obtained.

[0148] In the above embodiment, the differential design in each direction can be preferably the first differential design.

[0149] Therefore, a diffractive optical element with differential design in the row direction, column direction, and depth direction provided in this embodiment can more finely control the energy direction, effectively reduce the diffraction efficiency gap of light with different polarization angles, and the (1,1)-order diffraction efficiency is greater than the (-1,-1)-order diffraction.

[0150] In summary, compared with the traditional grating, the diffractive optical element provided by the present invention has lower polarization selectivity, higher diffraction efficiency for unpolarized light or polarized light. When it is applied to a diffractive waveguide, it will significantly improve the energy utilization efficiency of the diffractive optical waveguide, enhance the eye brightness, and reduce light leakage.

[0151] The above specific implementation manners do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A diffractive optical element, characterized in that, Comprising: a substrate, and a diffractive optical structure disposed on the substrate; The diffractive optical structure includes repeating units arranged in an array, each repeating unit includes a plurality of microstructures, the microstructures are micro-nano columnar structures, and the plurality of microstructures can be arranged on the substrate to form a three-dimensional optical structure with i rows, j columns and k layers, where i, j, and k are all positive integers. The plane formed by the intersection of the row direction and the column direction in the three-dimensional optical structure is parallel to the bottom surface of the substrate, and the depth direction is perpendicular to the bottom surface of the substrate; Wherein, in the three-dimensional optical structure, at least any two adjacent microstructures have a first difference and / or a second difference in the projected morphology on the substrate. The first difference is that the adjacent two projected morphologies are the same graph and there is a relative rotation angle between them; the second difference is that the adjacent two projected morphologies are different graphs.

2. The diffractive optical element according to claim 1, wherein In at least one direction of the three-dimensional optical structure, any two adjacent microstructures have a first difference and / or a second difference in the projected morphology on the substrate.

3. The diffractive optical element according to claim 1, characterized in that, In the same direction in the three-dimensional optical structure, the difference types between adjacent rows, or adjacent columns, or adjacent layers are different.

4. The diffractive optical element according to claim 1 or 3, characterized in that, In a single row, or a single column, or a single layer in the three-dimensional optical structure, the difference types are different.

5. The diffractive optical element according to claim 4, characterized in that, In the diffractive optical structure, if there are columns with exactly the same projected morphology in the column direction, then there is also the first difference between the projected morphologies of each column. Or, if there are rows with exactly the same projected morphology in the row direction, then there is also the first difference between the projected morphologies of each row. Or, if there are layers with exactly the same projected morphology in the depth direction, then there is also the first difference between the projected morphologies of each layer.

6. The diffractive optical element according to claim 1, characterized in that When there is a first difference in the projected morphologies in any one of the row direction, the column direction and the depth direction, the plurality of relative rotation angles change in sequence along a preset curve in the corresponding direction.

7. The diffractive optical element according to claim 6, characterized in that, When there is a first difference in the projected morphologies in at least two of the row direction, the column direction and the depth direction, the preset curves corresponding to the sequential changes of the plurality of relative rotation angles in different directions are different.

8. The diffractive optical element according to claim 6 or 7, characterized in that, The preset curve is one of a constant function, a linear function, a trigonometric function or an exponential function.

9. The diffractive optical element according to claim 1, characterized in that, The projected morphology of the micro-nano columnar structure on the substrate is a regular graph or an irregular free graph. Among them, when there is a first difference in the arrangement of the projected morphologies, the regular graph is not a circle.

10. The diffractive optical element according to claim 1, characterized in that, The size range of each microstructure is 10 nm - 800 nm, and the height range is 50 nm - 2 μm.

11. The diffractive optical element according to claim 1, wherein The period range of the diffractive optical structure is 100 nm - 30 μm, and the number of microstructures included in each period is 2 - 60.

12. A diffractive optical waveguide, characterized in that, Including at least two functional diffraction regions and a diffractive optical element according to any one of claims 1 - 11, wherein the diffractive optical element can be disposed in any functional diffraction region of the diffractive optical waveguide.

13. The diffractive optical waveguide according to claim 12, characterized in that, At least one functional diffraction region of the diffractive optical waveguide is provided with a diffractive optical element as described in any one of claims 1-11, and the period of the diffractive optical element set in one of the row direction and the column direction is less than λ / 2n; alternatively, the periods of the diffractive optical element set in both the row direction and the column direction are greater than λ / n, where n is the refractive index of the waveguide substrate and λ is the specified ray wavelength.

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