Diffractive optical waveguide, display device

Abstract

The present invention discloses a diffractive optical waveguide and a display device. The diffractive optical waveguide includes: a waveguide substrate, an input grating, and a two-dimensional pupil-expanding grating; the two-dimensional pupil-expanding grating includes a plurality of optical unit structures arranged in an array, and each optical unit structure includes a plurality of segments, which are spliced in sequence along a first direction; along a second direction perpendicular to the first direction, the segments respectively contract in width at the top, upper-middle part, and bottom of the optical unit structure; the total length of the optical unit structure along the first direction is L, and the grating period of the input grating is d, and the relationship between L and d is: 0.88×d < L < 1.19×d. In the present invention, the optical unit structure is integrally arranged as a curved trapezoid, and the output coupling efficiency and the conduction efficiency can be adjusted by adjusting the structure of the curved trapezoid. This structure has high splitting efficiency and output coupling efficiency on both sides, especially an excellent structure at the conduction end of the two-dimensional grating region.

Description

Technical Field

[0001] The present invention generally relates to the field of diffraction-based display technologies, and more particularly to a diffractive optical waveguide and a display device. Background Art

[0002] Diffractive optical waveguides have advantages such as being thin, light, easy to replicate, and having a high processing yield. Compared with the low processing yield of array optical waveguides and the difficulty in mass production of holographic waveguides, the surface-relief diffractive optical waveguide is a relatively ideal solution for consumer electronics waveguide glasses. In diffractive optical waveguides, they can generally be divided into one-dimensional pupil-expanding diffractive optical waveguides and two-dimensional pupil-expanding diffractive optical waveguides. Among them, in some gratings in the output region of the two-dimensional pupil-expanding diffractive optical waveguide, there is a two-dimensional grating structure (i.e., grating periods exist in both directions). For the signal light orders transmitted inside the waveguide, when hitting the interface from inside the medium, four orders will be formed, including: the total reflection order, the output order, the left-side splitting order, and the right-side splitting order. As Figure 3 respectively corresponding to R(0, 0), R(1, 1), R(-1, 1), R(-2, 0) in ; this can play the role of two-dimensional pupil expansion. The black dots in the figure represent the light rays coupled out perpendicular to the screen. The two-dimensional pupil-expanding structure needs to penetrate the entire output region, which is a relatively large-span region. Therefore, these four parameters need to have a relatively high degree of freedom to achieve the purpose of high efficiency and good non-uniformity in the entire output region.

[0003] Therefore, it is necessary to provide a diffractive optical waveguide and a display device to at least partially solve the above problems. Summary of the Invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further detailed in the Detailed Description section. The Summary of the Invention section of the present invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.

[0005] To at least partially solve the above problems, a first aspect of the present invention provides a diffractive optical waveguide, comprising:

[0006] A waveguide substrate;

[0007] An input grating disposed on the waveguide substrate for coupling light into the waveguide substrate;

[0008] A two-dimensional pupil-expanding grating disposed on the waveguide substrate, the two-dimensional pupil-expanding grating comprising a plurality of optical unit structures arranged in an array for expanding the light propagating to the waveguide substrate and simultaneously coupling it out from the waveguide substrate;

[0009] The optical unit structure includes a plurality of sections, which are spliced in sequence along a first direction;

[0010] Along a second direction, the widths of the sections are respectively reduced at the top, upper middle, and bottom of the optical unit structure, and the first direction is perpendicular to the second direction;

[0011] The total length of the optical unit structure along the first direction is L, and the grating period of the coupling grating is d. The relationship between L and d is: 0.88*d < L < 1.19*d.

[0012] Optionally, the section is composed of a trapezoid, and the trapezoid is upright or inverted;

[0013] Alternatively, the section is composed of a rounded trapezoid, and the rounded trapezoid is upright or inverted;

[0014] Alternatively, the section is composed of an approximate trapezoid, and the approximate trapezoid is upright or inverted.

[0015] Optionally, the relationship between L and d is: 0.95*d < L < 1.15*d.

[0016] Optionally, the optical unit structure includes four such sections, which are respectively the first section, the second section, the third section, and the fourth section along the first direction;

[0017] The top width of the first section is W1, the bottom width of the first section and the top width of the second section are W2, the bottom width of the second section and the top width of the third section are W3, the bottom width of the third section and the top width of the fourth section are W4, and the bottom width of the fourth section is W5.

[0018] Optionally, the relationship between W2, W4, and L is: 1.25 ≤ (W2 + W4) / L ≤ 1.60.

[0019] Optionally, the relationship between W2, W4, and L is: 1.30 ≤ (W2 + W4) / L ≤ 1.45.

[0020] Optionally, the relationship between W2, W4, and L is:

[0021] 0.90 ≤ W2 / W4 ≤ 1.40, 0.65 ≤ W2 / L ≤ 0.85, 0.6 ≤ W4 / L ≤ 0.7.

[0022] Optionally, the relationship between W2 and W4 is: 0.95 ≤ W2 / W4 ≤ 1.20.

[0023] Optionally, the following relationship exists between W2 and L: 0.4*L < W2 < 1.0*L.

[0024] Optionally, the following relationship exists between W1 and W5: |W1 - W5| > 0.2*max(W1, W5).

[0025] Optionally, the following relationship exists among W1, W2, and W5:

[0026] W5 > 0.1*W1, or W5 > 0.2*W1, or W1 = W5 = 0;

[0027] 0.8*W2 > W5, or 0.3*W2 > W5.

[0028] Optionally, along the first direction, the length of the first section is L1, the length of the second section is L2, the length of the third section is L3, and the length of the fourth section is L4. The following relationship exists among L1, L2, L3, and L4: 0.43 ≤ (L1 + L2) / (L3 + L4) ≤ 2.30.

[0029] Optionally, the following relationship exists among L1, L2, L3, and L4: 0.50 ≤ (L1 + L2) / (L3 + L4) ≤ 1.50.

[0030] Optionally, the overall structure of the optical unit structure is a non-centrosymmetric structure, and W1 ≥ W5;

[0031] When (L1 + L2) / (L3 + L4) = 1, W2 ≠ W4;

[0032] When W2 = W4 and W1 = W5, L1 / (L1 + L2) ≠ L4 / (L3 + L4).

[0033] Optionally, along the second direction, a sampling section is randomly intercepted from the section. The top width of the sampling section is M1, the bottom width is M2, and the length is H. The following relationship exists among M1, M2, and H:

[0034] 0 ≤ arctan(((M1 - M2) / 2) / H) ≤ β, where β < 75°.

[0035] Optionally, the following relationship exists for β: β < 45°, or β < 30°.

[0036] Optionally, the corners of the optical unit structure are provided with rounded corners.

[0037] Optionally, along the second direction, draw a straight line A1 through the uppermost tangent point of the optical unit structure, draw a straight line A2 through the widest point in the upper part of the optical unit structure, draw a straight line A3 through the narrowest point in the middle of the optical unit structure, draw a straight line A4 through the widest point in the middle of the optical unit structure, and draw a straight line A5 through the lowermost tangent point of the optical unit structure;

[0038] The straight line connecting the uppermost tangent point of the optical unit structure and the intersection point of A2 and the boundary of the optical unit structure is B1, and the included angle between B1 and A1 is α1, where α1 ≤ 180°;

[0039] The straight line connecting the intersection point of A2 and the boundary of the optical unit structure and the intersection point of A3 and the boundary of the optical unit structure is B2, and the included angle between B2 and A2 is α2, where 30° ≤ α2 ≤ 90°;

[0040] The straight line connecting the intersection point of A3 and the boundary of the optical unit structure and the intersection point of A4 and the boundary of the optical unit structure is B3, and the included angle between B3 and A3 is α3, where 90° ≤ α3 ≤ 150°;

[0041] The straight line connecting the intersection point of A4 and the boundary of the optical unit structure and the lowermost tangent point of the optical unit structure is B4, and the included angle between B4 and A4 is α4, where 20° ≤ α4 ≤ 75°.

[0042] Optionally, along the second direction, with the midpoint of the narrowest point in the middle of the optical unit structure as the center, the connecting lines between the center of the first optical unit structure and the centers of the second and third optical unit structures adjacent to it diagonally backward form lattice direction lines, and the sum of the included angles between the two lattice direction lines and the midline of the first optical unit structure is θ, where 45° ≤ θ ≤ 75°.

[0043] Optionally, θ has the following relationship: 50° ≤ θ ≤ 70°, or 55° ≤ θ ≤ 65°.

[0044] Optionally, W2, L, and θ have the following relationship: W2 < 2 / 3 * (d * tan(θ)), L < 1 / 2 * (d * tan(θ)).

[0045] Optionally, the optical unit structure is a convex or concave hole structure formed on the waveguide substrate.

[0046] The second aspect of the present invention provides a display device, including the diffractive optical waveguide according to any one of the above technical solutions.

[0047] Optionally, the display device is a near-eye display device, including a lens, and the lens includes the diffractive optical waveguide.

[0048] A diffractive optical waveguide and a display device according to the present invention integrally form the optical unit structure in the two-dimensional grating into a curvilinear trapezoid, and the coupling-out efficiency and the conduction efficiency can be adjusted by adjusting the structure of the curvilinear trapezoid. This structure has a high light splitting efficiency and coupling-out efficiency on both sides, especially an excellent structure at the conduction end of the two-dimensional grating region. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The following drawings of the embodiments of the present invention are hereby incorporated as part of the present invention for understanding the present invention. The embodiments of the present invention shown in the drawings and their descriptions are used to explain the principles of the present invention. In the drawings,

[0050] Figure 1 is a schematic structural diagram of an optical unit structure of the prior art;

[0051] Figure 2 is a schematic structural diagram of a coupling-out grating of the prior art;

[0052] Figure 3 is a schematic diagram of the propagation order of the coupling-out grating of the prior art;

[0053] Figure 4 is a schematic diagram of the dimensions of an optical unit structure according to a preferred embodiment of the present invention;

[0054] Figure 5 is a schematic structural diagram of a coupling-out grating according to a preferred embodiment of the present invention;

[0055] Figure 6a is a schematic structural diagram of a diffractive optical waveguide according to a preferred embodiment of the present invention;

[0056] Figure 6b is a schematic structural diagram of a display device according to a preferred embodiment of the present invention;

[0057] Figure 7 is a schematic structural diagram of an optical unit structure according to a preferred embodiment of the present invention;

[0058] Figure 8 is a schematic structural diagram of an optical unit structure according to a preferred embodiment of the present invention;

[0059] Figure 9 is Figure 8 a schematic diagram of the dimensions of the sampling area in;

[0060] Figure 10 is a schematic structural diagram of an optical unit structure according to a preferred embodiment of the present invention;

[0061] Figure 11 is a schematic diagram of the dimensions of an optical unit structure according to a preferred embodiment of the present invention;

[0062] Figure 12 Schematic diagram of an output grating provided with optical unit structures of different shapes;

[0063] Figure 13a 、 Figure 13b Schematic diagram of an optical unit structure with a curved trapezoid of different shapes;

[0064] Figure 14 Simulation data graph of the influence of the parameter L / d on the two - side splitting * two - side coupling;

[0065] Figure 15a - Figure 15e Simulation data graph of the influence of different values of L / d on the two - side splitting * two - side coupling when the parameters are W1 - W5;

[0066] Figure 16a 、 Figure 16b Schematic diagram of an optical unit structure with a curved trapezoid of different shapes;

[0067] Figure 17a Simulation data graph of the influence of different values of (W2 + W4) / L on the two - side splitting * two - side coupling when the parameter L / d = 0.875;

[0068] Figure 17b Simulation data graph of the influence of different values of (W2 + W4) / L on the two - side splitting * two - side coupling when the parameter L / d = 1.000;

[0069] Figure 17c Simulation data graph of the influence of different values of (W2 + W4) / L on the two - side splitting * two - side coupling when the parameter L / d = 1.125;

[0070] Figure 18a 、 Figure 18b Schematic diagram of an optical unit structure with a curved trapezoid of different shapes;

[0071] Figure 19a - Figure 19c Simulation data graph of the influence of different values of W2 / W4 on the two - side splitting * two - side coupling when the parameters are different L / d;

[0072] Figure 20a 、 Figure 20b Schematic diagram of an optical unit structure with a curved trapezoid of different shapes;

[0073] Figure 21a - Figure 21i Simulation data graph of the influence of different values of (L1 + L2) / (L3 + L4) on the two - side splitting * two - side coupling when the parameters are different L1, L3.

[0074] Description of reference numerals:

[0075] 100: Optical unit structure

[0076] 101: First trapezoid

[0077] 102: Second trapezoid

[0078] 103: Third trapezoid

[0079] 104: Fourth trapezoid

[0080] 105: Fifth trapezoid

[0081] 106: Sixth trapezoid

[0082] 107: Seventh trapezoid

[0083] 108: Eighth trapezoid

[0084] 109: Ninth trapezoid

[0085] 110: Tenth trapezoid

[0086] 111: Eleventh trapezoid

[0087] 112: Twelfth trapezoid

[0088] 113: First section

[0089] 114: Second section

[0090] 115: Third section

[0091] 116: Fourth section

[0092] 117: Sampling section

[0093] 200: Two-dimensional pupil expansion grating

[0094] 300: Lens

[0095] 400: Opto-mechanics

[0096] 500: Optical unit structure

[0097] 600: Coupling-in grating

[0098] 700: Waveguide substrate Detailed implementation manners

[0099] In the following description, numerous specific details are given to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other instances, some well-known technical features are not described to avoid obscuring the present invention.

[0100] To fully understand the present invention, a detailed description will be presented in the following. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the concept of these exemplary embodiments to those of ordinary skill in the art. Obviously, the implementation of the embodiments of the present invention is not limited to the specific details familiar to those skilled in the art. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other embodiments.

[0101] The ordinal numbers such as "first" and "second" cited in the present invention are merely identifiers and do not have any other meanings, such as a specific order, etc. Moreover, for example, the term "first component" does not imply the existence of a "second component" by itself, and the term "second component" does not imply the existence of a "first component" by itself.

[0102] It should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer" and similar expressions used in the present invention are for illustrative purposes only and not for limitation.

[0103] In some embodiments, an optical unit structure 500 in a trapezoidal structure is disclosed, as Figure 1 、 Figure 2 shown, but it has two defects: 1) The trapezoidal structure naturally has an acute angle structure, and it is difficult to process and restore. Since the waveguide structure is a period of sub-wavelength structure, usually only a few hundred nanometers, the processing reducibility is not good enough, which will cause the deterioration of the beam splitting performance and the robustness is not good enough; 2) After the upper and lower bases and the height of the traditional trapezoid are fixed (the duty cycle is determined after the three parameters are determined, which is the main variable affecting four orders), the waist structure is already fixed, and its degree of freedom for controlling the coupling efficiency on both sides is insufficient. This will result in that although the beam splitting efficiency a is relatively high, the coupling efficiency b on both sides after beam splitting is relatively low, causing the overall coupling c = a * b efficiency of this structure to have no obvious advantage. In the present application, the curved trapezoid can maintain a relatively high beam splitting efficiency a', and at the same time can adjust the coupling efficiency b' on both sides. As a result, the overall coupling c' = a' * b' is relatively high.

[0104] The present invention discloses a diffractive optical waveguide and a display device.

[0105] Now, exemplary embodiments according to the present invention will be described in more detail with reference to the accompanying drawings.

[0106] As Figure 4 、 Figure 5 、 Figure 6a shown, in a preferred embodiment, a diffractive optical waveguide includes: a waveguide substrate 700, an input grating 600, and a two-dimensional pupil expansion grating 200;

[0107] The waveguide substrate 700 can be made of glass, optical plastic, or other optically transmissive materials;

[0108] The coupling grating 600 is disposed on the waveguide substrate 700 for coupling light into the waveguide substrate 700; the coupling grating 600 can adopt a one-dimensional grating;

[0109] The two-dimensional pupil-expanding grating 200 serves as an output grating. The two-dimensional pupil-expanding grating 200 is disposed on the waveguide substrate 700 and includes a plurality of optical unit structures 100 arranged in an array for expanding the light propagating to the waveguide substrate 700 and simultaneously coupling out the light from the waveguide substrate 700;

[0110] The optical unit structure 100 includes:

[0111] A plurality of sections spliced in sequence along a first direction, where the first direction is the X-axis direction in the figure;

[0112] Along a second direction, the widths of the sections are respectively reduced at the top, upper middle, and bottom of the optical unit structure 100. The second direction is the Y-axis direction in the figure, and the first direction is perpendicular to the second direction;

[0113] The total length of the optical unit structure 100 along the first direction is L, and the grating period of the coupling grating is d. The relationship between L and d is: 0.88*d < L < 1.19*d.

[0114] In the diffractive optical waveguide of this embodiment, the overall optical unit structure is set as a curved trapezoid, and the output efficiency and conduction efficiency can be adjusted by adjusting the structure of the curved trapezoid. This structure has high light splitting efficiency and output efficiency on both sides, especially at the conduction end in the two-dimensional grating region, which is an excellent structure. Compared with the traditional trapezoidal structure, the curved trapezoid structure can adjust the morphology of the optical unit structure with a large degree of freedom within a certain duty cycle range, forming a large product of light splitting efficiency and output efficiency on both sides. The simulation experiment results can be referred to. At the same time, the processability is significantly stronger than that of the ordinary trapezoid in the prior art.

[0115] In one embodiment, as Figure 4 shown, the optical unit structure 100 includes four sections, which are the first section 113, the second section 114, the third section 115, and the fourth section 116 along the first direction respectively;

[0116] The top width of the first section 113 is W1, the bottom width of the first section 113 and the top width of the second section 114 are W2, the bottom width of the second section 114 and the top width of the third section 115 are W3, the bottom width of the third section 115 and the top width of the fourth section 116 are W4, and the bottom width of the fourth section 116 is W5.

[0117] As Figure 4 shown, the total length L of the optical unit structure 100 = L1 + L2 + L3 + L4.

[0118] After splicing the four sections, the maximum width is W2 and the length is L = L1 + L2 + L3 + L4, where the relationship between L and the coupling-in grating period d is L < 1.2 * d, preferably L < d; the relationship between W2 and L is W2 < 0.7 * L.

[0119] Simulation experiment 1:

[0120] In all simulation experiments of this embodiment, gratings with a refractive index of 1.9 and green light with a wavelength of 532 nm are used.

[0121] For Figure 2 and Figure 5 the output coupling gratings shown, simulation experiments are carried out. The experimental results are shown in Table 1. Compared with the existing trapezoidal optical unit structure, the optical unit structure with a curved trapezoidal (gourd-like) structure in this application can have a higher intermediate output coupling efficiency and split light on both sides * output coupling on both sides, almost reaching twice the order of magnitude of the existing trapezoid. There can be a good output coupling efficiency at the rear end of the entire diffractive optical waveguide, that is, the conduction end of the two-dimensional grating region.

[0122] Table 1. Comparison table of four optical parameters of the existing trapezoidal structure and the curved trapezoidal structure of this application

[0123]

[0124] For Figure 1 , Figure 2 the traditional trapezoidal optical unit structure shown, the output coupling efficiency on the left and right sides after splitting light is lower than that of the curved trapezoidal structure. From this point of view, the curved trapezoid has a large modulation freedom for the overall duty cycle, because the duty cycle is a definite parameter after the three parameters (upper base, lower base, and height) of the traditional trapezoid are determined, while the curved trapezoid can break through this duty cycle control and obtain the left and right light splitting efficiencies and the left and right output coupling efficiencies after splitting light outside the traditional trapezoid, as well as the product of the two.

[0125] Simulation experiment 2:

[0126] Table 2. Comparison table of four optical parameters of the existing optical unit structure and the optical unit structure of this application

[0127]

[0128] The optical unit structures for comparison refer to Figure 12 shown, and are respectively: circular, elliptical, trapezoidal, double diamond, single diamond, curved trapezoid.

[0129] As Figure 6bAs shown, the light in the waveguide travels along the arrow. When it reaches the dashed box, a greater intermediate coupling efficiency and greater splitting on both sides are required *to achieve high efficiency in the end field of view through splitting on both sides. At this position, the intermediate total reflectance is already a less important parameter. Excessive intermediate total reflectance within the dashed box range will cause energy waste. The total reflectance on both sides only plays a role within a very small range after splitting, and it can be regarded as a negative index. In summary, the optical unit structure in the shape of a curvilinear trapezoid has very good optical effects within the dashed box range, surpassing the previous conventional shapes.

[0130] Figure 5 The optical unit structure 100 in [reference] is formed by applying a certain Gaussian blur to the edges of a curvilinear trapezoid. Smoothing the edges of a two-dimensional structure is beneficial for micro-nano optical processing as the curve becomes smoother. By adjusting the σ parameter of the Gaussian blur, different degrees of smoothing can be achieved for the edges of the two-dimensional structure, with edge morphologies varying from 0nm σ to 200nm σ and the ultimately achieved optical effects.

[0131]

[0132] The formula for Gaussian blur is as shown above. In the formula, σ is the standard deviation of the normal distribution, and σ is less than 200nm, preferably less than 100nm.

[0133] In one embodiment, as Figure 7 shown, each section of the optical unit structure 100 is composed of a trapezoid, which can be upright or inverted. An upright trapezoid has the smaller base facing upwards, and an inverted trapezoid has the smaller base facing downwards. Figure 7 In [reference], the optical unit structure 100 includes twelve trapezoids:

[0134] The first trapezoid 101 is upright, the second trapezoid 102 is inverted, the third trapezoid 103 is inverted, the fourth trapezoid 104 is inverted, the fifth trapezoid 105 is upright, the sixth trapezoid 106 is upright, the seventh trapezoid 107 is inverted, the eighth trapezoid 108 is inverted, the ninth trapezoid 109 is inverted, the tenth trapezoid 110 is inverted, the eleventh trapezoid 111 is inverted, and the twelfth trapezoid 112 is inverted.

[0135] It should be added that: The sixth trapezoid 106 appears to be a rectangle but is still a trapezoid. Due to the limitation of the drawing size, it looks relatively close to a rectangle.

[0136] From a practical application perspective, multiple trapezoids can be spliced to form various curvilinear trapezoid structures, offering a high degree of design freedom.

[0137] In one embodiment, as Figure 5As shown, certain sections of the optical unit structure 100 are formed by rounded trapezoids, which can be upright or inverted. The rounded trapezoid can have rounded corners at the top two corners, for example, the top two corners of the first trapezoid 101 are designed to be rounded, or it can have rounded corners at the bottom two corners, for example, the bottom two corners of the twelfth trapezoid 112 are designed to be rounded, or it can have rounded corners at all four corners, for example, all four corners of the first trapezoid 101 are designed to be rounded.

[0138] In one embodiment, as Figure 5 shown, certain sections of the optical unit structure 100 are formed by approximate trapezoids, which can be upright or inverted. The approximate trapezoid can have arc-shaped waists, for example, the waists of the fourth trapezoid 104 and the fifth trapezoid 105 are designed to be arc-shaped.

[0139] In one embodiment, L and d have the following relationship: 0.95*d < L < 1.15*d. The corresponding technical effects can be referred to the results of simulation experiments 3 and 4.

[0140] In one embodiment, W2 is the maximum width of the section near the top of the optical unit structure 100, W4 is the maximum width of the section near the middle of the optical unit structure 100, and W2, W4, and L have the following relationship: 1.25 ≤ (W2 + W4) / L ≤ 1.60. The corresponding technical effects can be referred to the results of simulation experiments 5, 6, 7, and 8.

[0141] In one embodiment, W2, W4, and L have the following relationship: 1.30 ≤ (W2 + W4) / L ≤ 1.45. The corresponding technical effects can be referred to the results of simulation experiments 5, 6, 7, and 8.

[0142] In one embodiment, W2, W4, and L have the following relationship:

[0143] 0.90 ≤ W2 / W4 ≤ 1.40, 0.65 ≤ W2 / L ≤ 0.85, 0.6 ≤ W4 / L ≤ 0.7. The corresponding technical effects can be referred to the results of simulation experiment 9.

[0144] In one embodiment, W2 and W4 have the following relationship: 0.95 ≤ W2 / W4 ≤ 1.20. The corresponding technical effects can be referred to the results of simulation experiment 9.

[0145] In one embodiment, W2 and L have the following relationship: 0.4*L < W2 < 1.0*L.

[0146] In one embodiment, W1 and W5 have the following relationship: |W1 - W5| > 0.2*max(W1, W5).

[0147] In one embodiment, W1, W2, and W5 have the following relationships:

[0148] W5 > 0.1 * W1, or, W5 > 0.2 * W1, or, W1 = W5 = 0;

[0149] 0.8 * W2 > W5, or, 0.3 * W2 > W5.

[0150] In one embodiment, along the first direction, the length of the first section 113 is L1, the length of the second section 114 is L2, the length of the third section 115 is L3, and the length of the fourth section 116 is L4. L1, L2, L3, and L4 have the following relationship: 0.43 ≤ (L1 + L2) / (L3 + L4) ≤ 2.30. The corresponding technical effects can be referred to the results of simulation experiment 10.

[0151] In one embodiment, L1, L2, L3, and L4 have the following relationship: 0.50 ≤ (L1 + L2) / (L3 + L4) ≤ 1.50. The corresponding technical effects can be referred to the results of simulation experiment 10.

[0152] In one embodiment, the overall structure of the optical unit structure 100 is a non-centrosymmetric structure, and W1 ≥ W5;

[0153] When (L1 + L2) / (L3 + L4) = 1, W2 ≠ W4;

[0154] When W2 = W4 and W1 = W5, L1 / (L1 + L2) ≠ L4 / (L3 + L4).

[0155] In one embodiment, as Figure 8 , Figure 9 shown, along the second direction, a sampling section 117 is randomly intercepted from the section. The top width of the sampling section 117 is M1, the bottom width is M2, and the length is H. M1, M2, and H have the following relationship:

[0156] 0 ≤ arctan(((M1 - M2) / 2) / H) ≤ β, where β < 75°.

[0157] In one embodiment, β has the following relationship: β < 45°, or, β < 30°.

[0158] In one embodiment, the corners of the optical unit structure 100 are set as rounded corners.

[0159] In one embodiment, as Figure 10 , Figure 11As shown in the figure, along the second direction, draw a straight line A1 through the uppermost tangent point of the optical unit structure 100, draw a straight line A2 through the widest part at the upper part of the optical unit structure 100, draw a straight line A3 through the narrowest part in the middle of the optical unit structure 100, draw a straight line A4 through the widest part in the middle of the optical unit structure 100, and draw a straight line A5 through the lowermost tangent point of the optical unit structure 100;

[0160] The straight line connecting the uppermost tangent point of the optical unit structure 100 and the intersection point of A2 and the boundary of the optical unit structure 100 is B1, and the included angle between B1 and A1 is α1, where α1 ≤ 180°;

[0161] The straight line connecting the intersection point of A2 and the boundary of the optical unit structure 100 and the intersection point of A3 and the boundary of the optical unit structure 100 is B2, and the included angle between B2 and A2 is α2, where 30° ≤ α2 ≤ 90°;

[0162] The straight line connecting the intersection point of A3 and the boundary of the optical unit structure 100 and the intersection point of A4 and the boundary of the optical unit structure 100 is B3, and the included angle between B3 and A3 is α3, where 90° ≤ α3 ≤ 150°;

[0163] The straight line connecting the intersection point of A4 and the boundary of the optical unit structure 100 and the lowermost tangent point of the optical unit structure 100 is B4, and the included angle between B4 and A4 is α4, where 20° ≤ α4 ≤ 75°.

[0164] In one embodiment, as Figure 5 shown in the figure, along the second direction, with the midpoint of the narrowest part in the middle of the optical unit structure 100 as the center, the connecting lines between the center of the first optical unit structure 100 and the centers of the second and third adjacent optical unit structures 100 in the obliquely rear direction form lattice direction lines, and the sum of the included angles between the two lattice direction lines and the midline of the first optical unit structure 100 is θ, where 45° ≤ θ ≤ 75°.

[0165] In one embodiment, θ has the following relationship: 50° ≤ θ ≤ 70°, or 55° ≤ θ ≤ 65°.

[0166] In one embodiment, W2, L, and θ have the following relationship: W2 < 2 / 3 * (d * tan(θ)), L < 1 / 2 * (d * tan(θ)).

[0167] In one embodiment, the two-dimensional pupil-expanding grating includes a plurality of optical unit structures 100 arranged in an array along a plane, which is used to expand the light propagating approximately parallel to the plane to the waveguide substrate 700 in the plane and simultaneously couple out the light from the waveguide substrate 700.

[0168] In one embodiment, the optical unit structure 100 is a convex or concave hole-like structure formed on the waveguide substrate 700, having a cross-section parallel to the plane, and the structural features of the cross-section refer to the structural features of the aforementioned optical unit structure 100.

[0169] An embodiment of the present invention also provides a display device, including the diffractive optical waveguide described in any one of the above embodiments.

[0170] In one embodiment, as Figure 6b shown, the display device is a near-eye display device, including a lens 300, and the lens 300 includes a diffractive optical waveguide.

[0171] The display device further includes an optical engine 400, and the optical engine 400 emits laser light to the coupling grating.

[0172] Simulation experiment 3: Influence of the topography parameter L

[0173] As Figure 13a 、 13b shown, simulation tests are carried out on the optical unit structures of seven different L-shaped trapezoids.

[0174] Table 3. Comparison table of four optical parameters of different L-shaped trapezoids of the optical unit structure of the present application

[0175]

[0176] In this group of simulations, through the relationship between L and the coupling grating d, the most suitable total length of L is given. That is, when L is approximately equal to d, the effect is the best. If L < 0.9*d or L > 1.1*d, the effect will deteriorate significantly, and this deterioration cannot be compensated by changing the width of W.

[0177] After simulation tests, topography 1 is the best test result, and its L length is close to 1 times the period d of the coupling grating. It can be seen from the data that the L of topography 1, 2, and 4 is in the range of 0.9 times to 1.1 times the period d of the coupling grating, and the ratio is located between 0.85 and 1.25, preferably between 0.95 and 1.1.

[0178] Simulation experiment 4: Influence of different L / d on two-side splitting * two-side coupling out

[0179] The simulation results are shown in reference to Figure 14 、Table 4.

[0180] Table 4. Parameter scan of different L / d and different W1 to W5 of the optical unit structure of the present application

[0181] Parameter Optimal Parameter / nm Parameter Variation Range / nm W1 200 20-300 W2 310 240-380 W3 220 100-240 W4 260 240-380 W5 70 20-140

[0182] As Figure 14As shown, through simulation tests, it has better effects when the coupled grating period d is 0.9 times to 1.1 times, and the L / d ratio is positioned from 0.85 to 1.25, preferably from 0.95 to 1.1.

[0183] It can be further referred to Figure 15a - Figure 15e as shown in Tables 5 - 9.

[0184] Figure 15a It is the influence of W1 on the light splitting on both sides * the light coupling out on both sides at different L / d. Five values of L / d are selected in the figure, presenting five different curves respectively. It can be seen from the figure that when different values of L / d are adopted, there are obvious size differences in the light splitting on both sides * the light coupling out on both sides. When L / d is 1.1250, the light splitting on both sides * the light coupling out on both sides is basically the largest. Moreover, as W1 increases, some of the light splitting on both sides * the light coupling out on both sides show an increasing trend, while some show a decreasing trend. Figure 15a The parameters adopted are shown in Table 5.

[0185] Table 5. Variation range of width W1, variation range of L / d

[0186]

[0187]

[0188] Figure 15b It is the influence of W2 on the light splitting on both sides * the light coupling out on both sides at different L / d. Five values of L / d are selected in the figure, presenting five different curves respectively. It can be seen from the figure that when different values of L / d are adopted, there are obvious size differences in the light splitting on both sides * the light coupling out on both sides. When L / d is 1.1250, the light splitting on both sides * the light coupling out on both sides is basically the largest. Moreover, as W2 increases, some of the light splitting on both sides * the light coupling out on both sides show an increasing trend, while some show a decreasing trend. Figure 15b The parameters adopted are shown in Table 6.

[0189] Table 6. Variation range of width W2, variation range of L / d

[0190] Parameter Parameter Range W1 200 nm W2 240 nm - 380 nm W3 220 nm W4 260 nm W5 70 nm L / d 0.5625-1.3125

[0191] Figure 15c It is the influence of W3 on the light splitting on both sides * the light coupling out on both sides at different L / d. Five values of L / d are selected in the figure, presenting five different curves respectively. It can be seen from the figure that when different values of L / d are adopted, there are obvious size differences in the light splitting on both sides * the light coupling out on both sides. When L / d is 1.1250, the light splitting on both sides * the light coupling out on both sides is basically the largest. Moreover, as W3 increases, the light splitting on both sides * the light coupling out on both sides basically shows an increasing trend. Figure 15c The parameters adopted are shown in Table 7.

[0192] Table 7. Variation range of width W3, variation range of L / d

[0193]

[0194]

[0195] Figure 15d The influence of W4 on the light splitting on both sides * the light coupling out on both sides under different L / d. Five values of L / d are selected in the figure, presenting five different curves respectively. It can be seen from the figure that when different values of L / d are adopted, there are obvious differences in the light splitting on both sides * the light coupling out on both sides. When L / d is 1.1250, the light splitting on both sides * the light coupling out on both sides are basically the largest. Moreover, as W4 increases, the light splitting on both sides * the light coupling out on both sides basically show a decreasing trend. Figure 15d The parameters adopted are shown in Table 8.

[0196] Table 8. The variation ranges of width W4 and L / d

[0197] Parameter Parameter Range W1 200 nm W2 310 nm W3 220 nm W4 240 nm - 380 nm W5 70 nm L / d 0.5625-1.3125

[0198] Figure 15e The influence of W5 on the light splitting on both sides * the light coupling out on both sides under different L / d. Five values of L / d are selected in the figure, presenting five different curves respectively. It can be seen from the figure that when different values of L / d are adopted, there are obvious differences in the light splitting on both sides * the light coupling out on both sides. When L / d is 1.1250, the light splitting on both sides * the light coupling out on both sides are basically the largest. Moreover, as W5 increases, some of the light splitting on both sides * the light coupling out on both sides show an increasing trend, while some show a decreasing trend. Figure 15e The parameters adopted are shown in Table 9.

[0199] Table 9. The variation ranges of width W5 and L / d

[0200]

[0201]

[0202] Simulation experiment 5: The influence of the morphological parameter (W2 + W4) / L

[0203] Simulation results for reference Figure 16a 、 16b 、as shown in Table 10.

[0204] Explore the change of light efficiency caused by the change of the relative relationship between the two main width parameters W2 and W4 of the curved trapezoid two-dimensional structure and L. When the sum value of W2 and W4 is within a certain range, the overall light efficiency is the best, and this range is when (W2 + W4) / L is between 1.25 and 1.6.

[0205] Table 10. Scanning of the influence of different (W2 + W4) parameters for the optical unit structure L = d of this application

[0206]

[0207]

[0208] After simulation tests, it can be seen from the simulation results that when L is fixed at the best value, i.e., L = d, when (W2 + W4) / L varies between 1.25 and 1.6, the light splitting on both sides * the coupling out on both sides shows a trend of first increasing and then decreasing, and the optimal value is between 1.3 and 1.45.

[0209] Simulation Experiment 6: Influence of Different L / d and Morphology Parameter (W2 + W4) / L

[0210] Reference for Simulation Results Figure 17a as shown in Table 11.

[0211] Table 11. Optical Unit Structure of This Application: Influence of Different Values of (W2 + W4) / L on Light Splitting on Both Sides * Coupling Out on Both Sides when L / d = 0.875

[0212] Parameter Parameter Range W1 200 nm W2 240 nm - 380 nm W3 220 nm W4 240 nm - 380 nm W5 70 nm L / D 0.875

[0213] Simulation Experiment 7: Influence of Different L / d and Morphology Parameter (W2 + W4) / L

[0214] Reference for Simulation Results Figure 17b as shown in Table 12.

[0215] Table 12. Optical Unit Structure of This Application: Influence of Different Values of (W2 + W4) / L on Light Splitting on Both Sides * Coupling Out on Both Sides when L / d = 1.000

[0216]

[0217]

[0218] Simulation Experiment 8: Influence of Different L / d and Morphology Parameter (W2 + W4) / L

[0219] Reference for Simulation Results Figure 17c as shown in Table 13.

[0220] Table 13. Optical Unit Structure of This Application: Influence of Different Values of (W2 + W4) / L on Light Splitting on Both Sides * Coupling Out on Both Sides when L / d = 1.125

[0221] Parameter Parameter Range W1 200 nm W2 240 nm - 380 nm W3 220 nm W4 240 nm - 380 nm W5 70 nm L / D 1.125

[0222] Simulation Experiment 9: Influence of Morphology Parameter W2 / W4

[0223] Reference for Simulation Results Figure 18a and Figure 18b and Figure 19a andFigure 19b , Figure 19c as shown in Table 14.

[0224] Investigate the influence of the relative relationship between the two main width parameters W2 and W4 of the curvilinear trapezoid two-dimensional structure on the light efficiency. When the range is above 0.95, the light efficiency is better, preferably 1.0 to 1.1.

[0225] Table 14. Optical unit structure of this application: Influence of the morphological parameter W2 / W4

[0226]

[0227]

[0228] It can be seen from the above table that W2 / W4 is in a suitable range. When this value is from 0.95 to 1.30, preferably 1.0 to 1.1.

[0229] Such as Figure 19a , Figure 19b , Figure 19c As shown, taking the condition with the best effect of L / d being 1.000, in the numerical range above 0.005 shown by the contour lines, the change range of W2 is about 260nm to 340nm, the change range of W4 is 240nm to 280nm, the change range of W2 / W4 is 0.93 to 1.41, and the optimal range is determined to be between 0.90 - 1.40 for W2 / W4, preferably 0.95 - 1.20, where the range of W2 / L is 0.65 - 0.85 and the range of W4 / L is 0.6 to 0.7.

[0230] Simulation experiment 10: Influence of the morphological parameter L

[0231] Simulation results for reference Figure 20a , 20b , Figure 21a - Figure 21i as shown in Table 15.

[0232] Investigate the influence of the change of the ratio of (L1 + L2) / (L3 + L4) of the curvilinear trapezoid two-dimensional structure on the overall light efficiency. When the value of (L1 + L2) / (L3 + L4) is between 0.43 and 2.3, the light efficiency is better.

[0233] Table 15. Optical unit structure of this application: Influence of the morphological parameter (L1 + L2) / (L3 + L4)

[0234]

[0235] It can be seen from the above table that (L1 + L2) / (L3 + L4) is in a suitable range, and the ratio is 0.43 - 2.33, preferably 0.50 to 1.50.

[0236] As shown Figure 21a - Figure 21i in the figure, the traversal two-dimensional diagram of different (L1+L2) / (L3+L4) is given. If the condition of splitting light on both sides * coupling out on both sides being above 0.0051 is used as the demarcation condition, then from the scanning results, it can be seen that only when (L1+L2) / (L3+L4) is between 0.43 and 2.33 can it be achieved. At 0.67 and 1.00, the extreme values of splitting light on both sides * coupling out on both sides are high, and there are relatively many states that can reach the extreme value conditions. Therefore, the value of (L1+L2) / (L3+L4) is selected to be between 0.43 and 2.33, preferably between 0.50 and 1.50.

[0237] For a diffractive optical waveguide and a display device according to the present invention, the optical unit structure in the two-dimensional grating is set as a curvilinear trapezoid. The coupling-out efficiency and the conduction efficiency can be adjusted by adjusting the structure of the curvilinear trapezoid. This structure has a very high splitting-light efficiency on both sides and a coupling-out efficiency on both sides. Especially at the conduction end in the two-dimensional grating region, it is an excellent structure. Compared with the traditional trapezoidal structure, the curvilinear trapezoid structure can adjust the morphology of the optical unit structure with a large degree of freedom within a certain duty cycle range, forming a large product of the splitting-light efficiency and the coupling-out efficiency on both sides. At the same time, the processability is also significantly stronger than that of the ordinary trapezoid in the prior art.

[0238] In all the above preferred embodiments, the processes and steps described are only examples. Unless adverse effects occur, various processing operations can be performed in an order different from the order of the above processes. The order of the steps of the above processes can also be increased, combined, or deleted according to actual needs.

[0239] When understanding the scope of the present invention, as used herein, the term "comprising" and its derivatives are intended to be open-ended terms that specify the presence of the recited features, elements, components, groups, wholes, and / or steps, but do not exclude the presence of other unrecited features, elements, components, groups, wholes, and / or steps. This concept also applies to words with similar meanings, such as the terms "including", "having", and their derivatives.

[0240] As used herein, the term "attached" or "attachment" includes: a configuration in which an element is directly fixed to another element by directly fixing the element to the other element; a configuration in which an element is indirectly fixed to another element by fixing the element to an intermediate member, and the intermediate member is in turn fixed to the other element; and a configuration in which one element is integral with another element, that is, one element is substantially a part of the other element. This definition also applies to words with similar meanings, such as "connected", "coupled", "coupled", "mounted", "adhered", "fixed", and their derivatives. Finally, degree terms such as "substantially", "about", and "approximate" used herein indicate the amount of deviation that modifies the term such that the final result will not change significantly.

[0241] Unless otherwise defined, the technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the technical field of the present invention. The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention. The features described in one embodiment herein can be applied to another embodiment alone or in combination with other features, unless the feature is not applicable or otherwise stated in that other embodiment.

[0242] The present invention has been described by the above embodiments, but it should be understood that the above embodiments are for illustrative and exemplary purposes only and are not intended to limit the present invention to the scope of the described embodiments. In addition, those skilled in the art can understand that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of protection required by the present invention.

Claims

1. A diffractive optical waveguide, characterized in that, it comprises: a waveguide substrate; an input grating, which is arranged on the waveguide substrate and is used for coupling light into the waveguide substrate; and a two-dimensional pupil-expanding grating, which is arranged on the waveguide substrate, and the two-dimensional pupil-expanding grating comprises a plurality of optical unit structures arranged in an array and is used for expanding the light propagating to the waveguide substrate and simultaneously coupling out the light from the waveguide substrate; wherein, the optical unit structure comprises four sections, and the four sections are spliced in sequence along a first direction, and the four sections are respectively a first section, a second section, a third section and a fourth section along the first direction, the section is composed of a trapezoid, and the trapezoid is upright or inverted; alternatively, the section is composed of a rounded trapezoid, and the rounded trapezoid is upright or inverted; the sections respectively contract in width at the top, upper middle and bottom of the optical unit structure, the width is along a second direction, and the first direction is perpendicular to the second direction; the total length of the optical unit structure along the first direction is L, the grating period of the input grating is d, and the relationship between L and d is: 0.88*d < L < 1.19*d; the bottom width of the first section and the top width of the second section are W2, the bottom width of the third section and the top width of the fourth section are W4, the maximum width of the first section and the second section of the optical unit structure is W2, the maximum width of the third section and the fourth section of the optical unit structure is W4, and the relationship between W2 and W4 is: 1 < W2 / W4 ≤ 1.

40.

2. The diffractive optical waveguide according to claim 1, characterized in that, the relationship between L and d is: 0.95*d < L < 1.15*d.

3. The diffractive optical waveguide according to claim 1, characterized in that, the top width of the first section is W1, the bottom width of the second section and the top width of the third section are W3, and the bottom width of the fourth section is W5.

4. The diffractive optical waveguide according to claim 1, characterized in that, the relationship between W2, W4 and L is: 1.25 ≤ (W2 + W4) / L ≤ 1.

60.

5. The diffractive optical waveguide according to claim 1, characterized in that, the relationship between W2, W4 and L is: 1.30 ≤ (W2 + W4) / L ≤ 1.

45.

6. The diffractive optical waveguide according to claim 1, characterized in that, the relationship between W2, W4 and L is: 0.65 ≤ W2 / L ≤ 0.85, 0.6 ≤ W4 / L ≤ 0.

7.

7. The diffractive optical waveguide according to claim 1, characterized in that, the relationship between W2 and W4 is: 1 < W2 / W4 ≤ 1.

20.

8. The diffractive optical waveguide according to claim 1, characterized in that, the relationship between W2 and L is: 0.4*L < W2 < 1.0*L.

9. The diffractive optical waveguide according to claim 3, It is characterized in that the following relationship exists between the said W1 and the said W5: |W1 - W5| > 0.2 * max(W1, W5).

10. The diffractive optical waveguide according to claim 3, It is characterized in that the following relationship exists between the said W1, the said W2 and the said W5: W5 > 0.1 * W1, or, W5 > 0.2 * W1; 0.8 * W2 > W5, or, 0.3 * W2 > W5.

11. The diffractive optical waveguide according to claim 3, It is characterized in that along the said first direction, the length of the said first section is L1, the length of the said second section is L2, the length of the said third section is L3, the length of the said fourth section is L4, and the following relationship exists between the L1, the L2, the L3 and the L4: 0.43 ≤ (L1 + L2) / (L3 + L4) ≤ 2.

30.

12. The diffractive optical waveguide according to claim 11, It is characterized in that the following relationship exists between the L1, the L2, the L3 and the L4: 0.50 ≤ (L1 + L2) / (L3 + L4) ≤ 1.

50.

13. The diffractive optical waveguide according to claim 11, It is characterized in that the overall structure of the said optical unit structure is a non - centrosymmetric structure, and W1 ≥ W5; (L1 + L2) / (L3 + L4) = 1.

14. The diffractive optical waveguide according to claim 1, It is characterized in that randomly intercept a sampling section from the said section, the top width of the said sampling section is M1, the bottom width is M2, and the length is H, and the following relationship exists between the M1, the M2 and the H: 0 ≤ arctan(((M1 - M2) / 2) / H) ≤ β, where β < 75°.

15. The diffractive optical waveguide according to claim 14, It is characterized in that the following relationship exists for the said β: β < 45°, or, β < 30°.

16. The diffractive optical waveguide according to claim 1, It is characterized in that the corners of the said optical unit structure are set as rounded corners.

17. The diffractive optical waveguide according to any one of claims 1 - 16, It is characterized in that along the said second direction, draw a straight line A1 through the uppermost tangent point of the said optical unit structure, draw a straight line A2 through the widest point in the upper part of the said optical unit structure, draw a straight line A3 through the narrowest point in the middle of the said optical unit structure, draw a straight line A4 through the widest point in the middle of the said optical unit structure, and draw a straight line A5 through the lowermost tangent point of the said optical unit structure; The straight line connecting the uppermost tangent point of the said optical unit structure and the intersection point of A2 and the boundary of the said optical unit structure is B1, and the included angle between B1 and A1 is α1, α1 ≤ 180°; The straight line connecting the intersection point of A2 and the boundary of the said optical unit structure and the intersection point of A3 and the boundary of the said optical unit structure is B2, and the included angle between B2 and A2 is α2, 30° ≤ α2 ≤ 90°; The straight line connecting the intersection point of A3 and the boundary of the said optical unit structure and the intersection point of A4 and the boundary of the said optical unit structure is B3, and the included angle between B3 and A3 is α3, 90° ≤ α3 ≤ 150°; The straight line connecting the boundary intersection point of A4 and the optical unit structure and the tangent point at the lowermost end of the optical unit structure is B4, and the included angle between B4 and A4 is α4, where 20° ≤ α4 ≤ 75°.

18. The diffractive optical waveguide according to claim 1, wherein, Along the second direction, with the midpoint of the narrowest part in the middle of the optical unit structure as the center, the connecting lines between the center of the first optical unit structure and the centers of the second and third optical unit structures adjacent diagonally behind form lattice direction lines, and the sum of the included angles between the two lattice direction lines and the midline of the first optical unit structure is θ, where 45° ≤ θ ≤ 75°.

19. The diffractive optical waveguide according to claim 18, wherein, θ has the following relationship: 50° ≤ θ ≤ 70°, or 55° ≤ θ ≤ 65°.

20. The diffractive optical waveguide according to claim 19, wherein, W2, L, and θ have the following relationship: W2 < 2 / 3 * (d * tan(θ)), L < 1 / 2 * (d * tan(θ)).

21. The diffractive optical waveguide according to claim 1, wherein, The optical unit structure is a convex or concave hole structure formed on the waveguide substrate.

22. A display device, wherein, It includes the diffractive optical waveguide according to any one of claims 1 - 21.

23. The display device according to claim 22, wherein, The display device is a near-eye display device, including a lens, and the lens includes the diffractive optical waveguide.

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