Optical waveguide structure, optical waveguide module and head-mounted display device

Abstract

The invention discloses an optical waveguide structure, an optical waveguide module and head-mounted display equipment. The optical waveguide structure comprises a waveguide substrate, a coupling-in grating and a coupling-out grating. The coupling-in grating is used for coupling input light into the waveguide substrate and transmitting the input light. And the coupling-out grating is used for carrying out pupil expansion and coupling-out on the light transmitted in the waveguide substrate. The coupled-out grating is a two-dimensional grating, and the two-dimensional grating is provided with a two-dimensional structure element. And the characteristic axis direction of the two-dimensional structure element and the lattice period vector sum direction of the two-dimensional grating form a relative rotation angle so as to change the diffraction efficiency of the coupling-out grating in the preset direction. According to the optical waveguide structure, the optical waveguide module and the head-mounted display device, the characteristic axis direction of the two-dimensional structure element and the lattice period vector sum direction of the two-dimensional grating form the relative rotation angle to change the diffraction efficiency of the coupled-out grating in the preset direction, so that the form of the grating can be optimized, and the efficiency of the optical waveguide is improved.

Description

Technical Field

[0001] The present application relates to the field of optical waveguide technology, and in particular to an optical waveguide structure, an optical waveguide module, and a head-mounted display device. Background Art

[0002] Optical waveguides are a key component of augmented reality (AR) display devices. Their basic principle is that light emitted by an optical engine is coupled into the waveguide. As the light propagates through the waveguide, it undergoes total internal reflection, ensuring no energy loss until it is coupled out at the human eye. Improving the efficiency of the waveguide by optimizing the grating morphology is a key issue in waveguide design. Summary of the Invention

[0003] The embodiments of the present application provide an optical waveguide structure, an optical waveguide module, and a head-mounted display device to solve at least one of the above-mentioned technical problems.

[0004] The optical waveguide structure according to the embodiment of the present application includes:

[0005] waveguide substrate;

[0006] A coupling grating, used for coupling input light into the waveguide substrate and transmitting the light;

[0007] An outcoupling grating is used to expand the pupil of the light transmitted in the waveguide substrate and couple it out. The outcoupling grating is a two-dimensional grating having a two-dimensional structural element. The characteristic axis direction of the two-dimensional structural element forms a relative angle with the direction of the lattice period vector sum of the two-dimensional grating to change the diffraction efficiency of the outcoupling grating in a predetermined direction.

[0008] In some embodiments, the two-dimensional grating has a first lattice periodic direction and a second lattice periodic direction, and the number of the two-dimensional structural primitives is multiple, and the multiple two-dimensional structural primitives are arranged along the first lattice periodic direction and the second lattice periodic direction;

[0009] The direction of the sum of the lattice period vectors of the two-dimensional grating is the direction of the sum of the vector in the first lattice period direction and the vector in the second lattice period direction.

[0010] In some embodiments, the two-dimensional structural element has a first reciprocal lattice vector direction corresponding to the second lattice period direction and a second reciprocal lattice vector direction corresponding to the first lattice period direction, and the characteristic axis direction of the two-dimensional structural element and the direction of the sum of the lattice period vectors of the two-dimensional grating form the relative rotation angle to change the diffraction efficiency of the out-coupling grating in the first reciprocal lattice vector direction or the second reciprocal lattice vector direction.

[0011] In some embodiments, the first reciprocal lattice vector direction is perpendicular to the second lattice period direction, and the second reciprocal lattice vector direction is perpendicular to the first lattice period direction.

[0012] In some embodiments, the size of the relative rotation angle is determined based on the first lattice period length, the second lattice period length, and the angle between the first lattice period direction and the second lattice period direction.

[0013] In some embodiments, the two-dimensional structural element rotates along a first rotation direction so that the characteristic axis direction of the two-dimensional structural element and the direction of the sum of the lattice period vectors of the two-dimensional grating form a negative relative rotation angle, so as to increase the diffraction efficiency of the out-coupling grating in the direction of the first reciprocal lattice vector; wherein the first rotation direction is the direction of rotation from the first lattice period direction to the second lattice period direction.

[0014] In some embodiments, the outcoupling grating includes a first grating region corresponding to the direction of the first reciprocal lattice vector, within which the characteristic axis direction of the two-dimensional structural element and the direction of the sum of the lattice period vectors of the two-dimensional grating form the negative relative rotation angle.

[0015] In some embodiments, the two-dimensional structural element rotates along a second rotation direction so that the characteristic axis direction of the two-dimensional structural element and the direction of the lattice period vector sum of the two-dimensional grating form a positive relative rotation angle, so as to increase the diffraction efficiency of the out-coupling grating in the direction of the second reciprocal lattice vector; wherein the second rotation direction is the direction of rotation from the second lattice period direction to the first lattice period direction.

[0016] In some embodiments, the outcoupling grating includes a second grating region corresponding to the direction of the second reciprocal lattice vector, and within the second grating region, the characteristic axis direction of the two-dimensional structural element and the direction of the lattice period vector sum of the two-dimensional grating form the positive relative rotation angle.

[0017] In some embodiments, along a direction away from the coupling-in grating, the relative rotation angle changes gradually or in steps within the spatial range of the coupling-out grating.

[0018] The optical waveguide module according to the embodiment of the present application includes:

[0019] The optical waveguide structure of any one of the above embodiments; and

[0020] An optical engine is used to transmit input light to the coupling-in grating.

[0021] The head-mounted display device according to the embodiment of the present application includes the optical waveguide module according to the above embodiment.

[0022] In the optical waveguide structure, optical waveguide module and head-mounted display device of the embodiments of the present application, the characteristic axis direction of the two-dimensional structural element forms a relative angle with the direction of the sum of the lattice period vectors of the two-dimensional grating to change the diffraction efficiency of the out-coupling grating in a predetermined direction. In this way, the morphology of the grating can be optimized, thereby improving the efficiency of the optical waveguide.

[0023] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without inventive work. Among them:

[0025] Figure 1 is a schematic diagram of an optical waveguide structure according to certain embodiments of the present application;

[0026] Figure 2 This is a schematic diagram of a structure in which a two-dimensional structural element and a two-dimensional grating form a relative rotation angle in certain embodiments of the present application;

[0027] Figure 3 This is a schematic diagram of a structure in which a two-dimensional structural element and a two-dimensional grating form a relative rotation angle in certain embodiments of the present application;

[0028] Figure 4 Schematic diagram of the calculation principle of the relative rotation angle in certain embodiments of the present application;

[0029] Figure 5 It is a schematic diagram of a structure in which there is no relative rotation angle between the two-dimensional structural element and the two-dimensional grating;

[0030] Figure 6 Schematic diagram of the diffraction efficiency of the outcoupling grating in the direction of the first reciprocal grating vector in certain embodiments of the present application;

[0031] Figure 7 Schematic diagram of the diffraction efficiency of the outcoupling grating in the direction of the second reciprocal grating vector in certain embodiments of the present application;

[0032] Figure 8 is a schematic diagram of an optical waveguide structure according to certain embodiments of the present application;

[0033] Figure 9 is a schematic diagram of an optical waveguide structure according to certain embodiments of the present application;

[0034] Figure 10 is a schematic diagram of an optical waveguide structure according to certain embodiments of the present application;

[0035] Figure 11 is a schematic diagram of an optical waveguide structure according to certain embodiments of the present application;

[0036] Figure 12 It is a schematic diagram of the spatial distribution of the outgoing light energy in the eye box area when there is no relative rotation angle between the two-dimensional structural element and the two-dimensional grating;

[0037] Figure 13 is a schematic diagram of the spatial distribution of the outgoing light energy in the eye box region when the two-dimensional structural element and the two-dimensional grating form a relative rotation angle in certain embodiments of the present application;

[0038] Figure 14 is a schematic structural diagram of an optical waveguide module according to certain embodiments of the present application;

[0039] Figure 15 It is a structural schematic diagram of a head-mounted display device according to certain embodiments of the present application.

[0040] Description of reference numerals:

[0041] Optical waveguide structure 100, waveguide substrate 10, coupling-in grating 20, coupling-out grating 30, two-dimensional grating 31, two-dimensional structural element 32, first grating region 33, second grating region 34, third grating region 35, optical engine 200, optical waveguide module 300, head-mounted display device 1000. DETAILED DESCRIPTION

[0042] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be understood as limiting the present application.

[0043] See also Figure 1 and Figure 2 , an embodiment of the present application provides an optical waveguide structure 100. The optical waveguide structure 100 includes a waveguide substrate 10, a coupling-in grating 20, and a coupling-out grating 30. The coupling-in grating 20 is used to couple the input light into the waveguide substrate 10 and transmit it. The coupling-out grating 30 is used to expand the pupil of the light transmitted in the waveguide substrate 10 and couple it out. The coupling-out grating 30 is a two-dimensional grating 31, and the two-dimensional grating 31 has a two-dimensional structural element 32. The characteristic axis direction of the two-dimensional structural element 32 forms a relative rotation angle with the direction of the lattice period vector sum of the two-dimensional grating 31 to change the diffraction efficiency of the coupling-out grating 30 in a predetermined direction.

[0044] In the optical waveguide structure 100 of the embodiment of the present application, the characteristic axis direction of the two-dimensional structural element 32 forms a relative angle with the direction of the lattice period vector sum of the two-dimensional grating 31 to change the diffraction efficiency of the outcoupling grating 30 in a predetermined direction. In this way, the morphology of the grating can be optimized, thereby improving the efficiency of the optical waveguide.

[0045] Please combine Figure 14 In the embodiment of the present application, the transmission process of light can be as follows: the optical machine 200 emits input light toward the coupling grating 20, for example, the optical machine 200 transmits input light along Figure 1 The input light is emitted toward the coupling-in grating 20 in a direction perpendicular to the paper surface; the input light is coupled into the waveguide substrate 10 through the coupling-in grating 20 and transmitted, wherein the transmission of the light in the waveguide substrate 10 includes total internal reflection; the light transmitted in the waveguide substrate 10 is pupil-expanded and coupled out through the coupling-out grating 30, for example, the light transmitted in the waveguide substrate 10 is pupil-expanded in one dimension and / or in two dimensions through the coupling-out grating 30, and is coupled out along the coupling-out grating 30. Figure 1 The light is coupled out in a direction perpendicular to the paper surface and is received by the human eye.

[0046] See also Figure 1 and Figure 2 In the specific example of the present application, the coupling grating 20 is represented by IG and the coupling grating 30 is represented by OG. The coupling grating IG is used to provide the coupling wave vector The outcoupling grating OG is used to provide the first wave vector and the second wave vector The input light emitted by the optical engine 200 is coupled into the wave vector provided by the grating IG. The light transmitted in the waveguide substrate 10 is coupled into the waveguide substrate 10 and transmitted. The light transmitted in the waveguide substrate 10 is coupled into the waveguide substrate 10 and transmitted. One-dimensional pupil expansion occurs; after one-dimensional pupil expansion, the light passes through the wave vector provided by the outcoupling grating OG Alternatively, the light transmitted in the waveguide substrate 10 is coupled out through the wave vector provided by the outcoupling grating OG. One-dimensional pupil expansion occurs; after one-dimensional pupil expansion, the light passes through the wave vector provided by the outcoupling grating OG Two-dimensional pupil expansion occurs and coupling out occurs. It should be pointed out that when the wave vector space formed by the input light interacting with the coupling-in grating IG and the coupling-out grating OG is closed, the following conditional formula is satisfied: Thus, coupling out from the waveguide substrate 10 can be achieved.

[0047] Research has found that in actual structures, if the efficiency of the outcoupling grating is low, the light will not be fully coupled out and will be wasted. How to improve the efficiency of the optical waveguide by designing and optimizing the grating shape is an important issue in optical waveguide design. The embodiment of the present application changes the rotation angle of the two-dimensional structural element 32 so that the characteristic axis direction of the two-dimensional structural element 32 forms a relative angle with the direction of the lattice period vector sum of the two-dimensional grating 31, thereby changing the diffraction efficiency of the outcoupling grating 30 in a predetermined direction to optimize the grating shape and improve the efficiency of the optical waveguide. Among them, the two-dimensional grating 31 (i.e., the two-dimensional grating) refers to a grating with a periodic structure in two directions.

[0048] See also Figure 2 and Figure 3 In some embodiments, the two-dimensional grating 31 has a first lattice periodicity direction and a second lattice periodicity direction. There are multiple two-dimensional structural elements 32, and the multiple two-dimensional structural elements 32 are arranged along the first lattice periodicity direction and the second lattice periodicity direction. The direction of the sum of the lattice periodicity vectors of the two-dimensional grating 31 is the direction of the sum of the vectors in the first lattice periodicity direction and the second lattice periodicity direction.

[0049] Specifically, Figure 2 and Figure 3 for Figure 14 Schematic diagram of the planar structure of the outcoupling grating 30 viewed from bottom to top (or from top to bottom). The two-dimensional structural element 32 is the smallest repeating unit in the two-dimensional grating 31 (the two-dimensional structural element 32 can also be called a cell). The number of the two-dimensional structural elements 32 can be multiple, and the multiple two-dimensional structural elements 32 are distributed in an array as a whole, for example, in a rectangular array or a ring array. The projection shape of the two-dimensional structural element 32 on the two-dimensional grating 31 is a two-dimensional figure, such as a rectangle, an ellipse, a parallelogram or other arbitrary shapes. The embodiment of the present application uses a rectangle as an example.

[0050] like Figure 2 and Figure 3 As shown, the first lattice periodic direction is represented by a1, and the second lattice periodic direction is represented by a2. A plurality of two-dimensional structural elements 32 are arranged along the first lattice periodic direction a1 and the second lattice periodic direction a2. In other words, the two-dimensional structural elements 32 repeat periodically along the first lattice periodic direction a1 and repeat periodically along the second lattice periodic direction a2. The first lattice periodic direction a1 and the second lattice periodic direction a2 form an angle, which can be between 0 and 180 degrees.

[0051] The characteristic axis direction of the two-dimensional structure element 32 represents the main component direction of the two-dimensional structure element 32, such as Figure 2 、 Figure 3 and Figure 5When the projection of the two-dimensional structural element 32 on the two-dimensional grating 31 is a rectangle, the characteristic axis direction of the two-dimensional structural element 32 is the direction of the long side of the rectangle, or the direction of the length extension of the two-dimensional structural element 32. The direction of the lattice period vector and the direction of the first lattice period vector of the two-dimensional grating 31 refers to the vector of the first lattice period direction. The vector in the direction of the second lattice period The direction of the sum, such as Figure 4 The vector in the direction of the first lattice period is shown in the B direction. It has a first lattice period direction a1, and its size is the first lattice period length (ie, the distance between two adjacent two-dimensional structural units 32 arranged along the first lattice period direction a1). The vector of the second lattice period direction It has a second lattice period direction a2, and its size is the second lattice period length (i.e., the distance between two adjacent two-dimensional structural units 32 arranged along the second lattice period direction a2). The direction of the lattice period vector sum of the two-dimensional grating 31 is The relative rotation angle formed by the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector and of the two-dimensional grating 31 is the angle between the A direction and the B direction.

[0052] Please continue reading Figure 2 and Figure 3 In some embodiments, the two-dimensional structural element 32 has a first reciprocal lattice vector direction corresponding to the second lattice period direction and a second reciprocal lattice vector direction corresponding to the first lattice period direction. The characteristic axis direction of the two-dimensional structural element 32 forms a relative rotation angle with the direction of the lattice period vector sum of the two-dimensional grating 31 to change the diffraction efficiency of the outcoupling grating 30 in the first reciprocal lattice vector direction or the second reciprocal lattice vector direction.

[0053] like Figure 2 and Figure 3 As shown, the first reciprocal lattice vector direction is represented by k1, and the second reciprocal lattice vector direction is represented by k2. In the specific example of the present application, the outcoupling grating 30 is used to provide the first wave vector and the second wave vector first wave vector The direction of the first reciprocal lattice vector k1, the second wave vector The direction of is the second reciprocal lattice vector direction k2. The first lattice period direction a1 and the second lattice period direction a2 of the two-dimensional grating 31 determine the first reciprocal lattice vector direction k1 and the second reciprocal lattice vector direction k2 of the two-dimensional structural element 32. Among them, the first reciprocal lattice vector direction k1 is perpendicular to the second lattice period direction a2, and the second reciprocal lattice vector direction k2 is perpendicular to the first lattice period direction a1. In the embodiment of the present application, the characteristic axis direction of the two-dimensional structural element 32 forms a relative angle with the direction of the lattice period vector sum of the two-dimensional grating 31 to change the diffraction efficiency of the outcoupling grating 30 in the first reciprocal lattice vector direction k1 or the second reciprocal lattice vector direction k2.

[0054] Please combine Figure 4 In some embodiments, the size of the relative rotation angle is determined based on the first lattice period length, the second lattice period length, and the angle between the first lattice period direction and the second lattice period direction.

[0055] Specifically, the first lattice period length can be represented by the distance d1 between two adjacent two-dimensional structural elements 32 arranged along the first lattice period direction a1, and the second lattice period length can be represented by the distance d2 between two adjacent two-dimensional structural elements 32 arranged along the second lattice period direction a2. In other words, the magnitude of the relative rotation angle is determined by d1, d2, and the angle between a1 and a2. Based on d1, d2, and the angle between a1 and a2, combined with the parallelogram rule, the optimal magnitude of the relative rotation angle α1 or α2 can be determined. When it is necessary to change the diffraction efficiency of the outcoupling grating 30 in the first reciprocal lattice vector direction k1, for example, to maximize the diffraction efficiency of the outcoupling grating 30 in the first reciprocal lattice vector direction k1, the magnitude of the relative rotation angle can be set to α1. When it is necessary to change the diffraction efficiency of the outcoupling grating 30 in the second reciprocal lattice vector direction k2, for example, to maximize the diffraction efficiency of the outcoupling grating 30 in the second reciprocal lattice vector direction k2, the magnitude of the relative rotation angle can be set to α2. In one example, when d1 = d2, the relative rotation angle is half the angle between a1 and a2. For example, when the angle between a1 and a2 is 60 degrees, the relative rotation angle α1 or α2 is 30 degrees. For another example, when the angle between a1 and a2 is 90 degrees, the relative rotation angle α1 or α2 is 45 degrees.

[0056] Of course, in other embodiments, the size of the relative angle may not be determined based on the above method, but may be determined based on a comprehensive consideration of the direction in which the diffraction efficiency needs to be increased, the degree to which the diffraction efficiency needs to be increased, and other aspects. The above method is only used as an example.

[0057] The study also found that in the actual structure, if the efficiency of the outcoupling grating is high, more energy will be in the front end (such as Figure 1The left area of ​​the out-coupling grating in the middle) is prematurely coupled out after interacting with the out-coupling grating. At the same time, this part of the prematurely coupled light cannot enter the eye box area (EyeBox) due to the angle, resulting in energy waste. Especially for blue light, since the propagation angle of blue light in the waveguide is small and the step size is small, premature coupling is more likely to occur. Therefore, in the embodiment of the present application, the characteristic axis direction of the two-dimensional structural element 32 forms a negative relative rotation angle (such as Figure 2 As shown), to increase the diffraction efficiency of the outcoupling grating 30 in the first reciprocal lattice vector direction; or, the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector and the two-dimensional grating 31 form a positive relative rotation angle (as shown Figure 3 As shown), the diffraction efficiency of the out-coupling grating 30 in the second reciprocal lattice vector direction is increased, so that the light is more likely to be directed away from the in-coupling grating 20 (as shown). Figure 1 The light is transmitted to the right area of ​​the out-coupled grating 30), thereby improving the uniformity of the display (the specific principle will be explained later).

[0058] See also Figure 2 、 Figure 5 and Figure 6 In some embodiments, the two-dimensional structural element 32 is rotated along a first rotation direction such that the characteristic axis direction of the two-dimensional structural element 32 forms a negative relative rotation angle with the direction of the sum of the lattice period vectors of the two-dimensional grating 31, thereby increasing the diffraction efficiency of the outcoupling grating 30 in the direction of the first reciprocal lattice vector. The first rotation direction is the direction from the first lattice period direction to the second lattice period direction.

[0059] Specifically, see Figure 5 When the rotation angle of the two-dimensional structural element 32 is unchanged, there is no relative rotation angle between the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector sum of the two-dimensional grating 31 (i.e., direction A is consistent with direction B), and the diffraction efficiency of the outcoupling grating 30 in the first reciprocal lattice vector direction k1 and the second reciprocal lattice vector direction k2 is equal. The two-dimensional structural element 32 rotates along the first rotation direction (the direction from the first lattice period direction a1 to the second lattice period direction a2), which is Figure 5 The counterclockwise rotation makes the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector sum of the two-dimensional grating 31 form a negative relative rotation angle (such as Figure 2 As shown in FIG, the diffraction efficiency of the outcoupling grating 30 in the first reciprocal lattice vector direction k1 is increased. Figure 4In one example, when the angle between a1 and a2 is 60 degrees, the two-dimensional structural element 32 rotates 30 degrees counterclockwise (i.e., α1 = -30 degrees), so that the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector sum of the two-dimensional grating 31 form a relative rotation angle of -30 degrees, so that the diffraction efficiency of the outcoupling grating 30 in the first reciprocal lattice vector direction k1 is relatively strong (e.g., Figure 6 shown).

[0060] It should be noted that during the counterclockwise rotation of the two-dimensional structural element 32, the first lattice period direction a1 and the second lattice period direction a2 remain unchanged, and the first lattice period direction a1 and the second lattice period direction a2 determine the first reciprocal lattice vector direction k1 and the second reciprocal lattice vector direction k2. Therefore, the first reciprocal lattice vector direction k1 and the second reciprocal lattice vector direction k2 also remain unchanged. In this way, the spatial closure of the wave vector formed by the input light after interacting with the coupling grating 20 and the coupling grating 30 will not be affected. The rotation of the two-dimensional structural element 32 is only the rotation of the two-dimensional structural element 32 itself, for example Figure 2 The rectangle in the figure is rotated to change the characteristic axis direction of the two-dimensional structural element 32, thereby increasing the diffraction efficiency of the outcoupling grating 30 in the first reciprocal lattice vector direction k1.

[0061] See also Figure 2 、 Figure 8 and Figure 9 In some embodiments, the outcoupling grating 30 includes a first grating region 33 corresponding to the first reciprocal lattice vector direction. In the first grating region 33, the characteristic axis direction of the two-dimensional structural element 32 forms a negative relative rotation angle with the direction of the lattice period vector sum of the two-dimensional grating 31.

[0062] Specifically, when the light transmitted in the waveguide substrate 10 reaches the outcoupling grating 30, part of the light obtains the wave vector provided by the outcoupling grating 30. Propagating downward, if we continue to obtain the wave vector provided by the outcoupling grating 30 If the wave vector space is closed, it will be coupled out from the waveguide substrate 10, and there is a problem of premature coupling. The first grating region 33 (eg Figure 8 The characteristic axis direction of the two-dimensional structural element 32 forms a negative relative rotation angle with the direction of the lattice period vector sum of the two-dimensional grating 31 to increase the diffraction efficiency of the out-coupling grating 30 in the first reciprocal lattice vector direction k1, and then this part of the light continues to obtain the wave vector provided by the out-coupling grating 30. is more efficient due to the wave vector The direction is bidirectional, the wave vector With wave vector is symmetrical, so this part of the light continues to obtain the wave vector provided by the outcoupling grating 30 The efficiency will be higher, and the With the previously obtained The offsetting effect causes the light to not be coupled out immediately but to continue to propagate forward, thereby allowing the light to propagate more in a direction away from the coupling-in grating 20, thereby improving the uniformity of the display.

[0063] It should be pointed out that Figure 9 The thick arrows represent the transmission of light in the waveguide substrate 10 , and the thin arrows represent the coupling of light out of the waveguide substrate 10 (the coupling direction is, for example, perpendicular to the paper and outward).

[0064] See also Figure 3 、 Figure 5 and Figure 7 In some embodiments, the two-dimensional structural element 32 is rotated along a second rotation direction so that the characteristic axis direction of the two-dimensional structural element 32 forms a positive relative rotation angle with the direction of the lattice period vector sum of the two-dimensional grating 31, thereby increasing the diffraction efficiency of the outcoupling grating 30 in the direction of the second reciprocal lattice vector. The second rotation direction is the direction of rotation from the second lattice period direction to the first lattice period direction.

[0065] Specifically, see Figure 5 When the rotation angle of the two-dimensional structural element 32 is unchanged, there is no relative rotation angle between the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector sum of the two-dimensional grating 31 (i.e., direction A is consistent with direction B), and the diffraction efficiency of the outcoupling grating 30 in the first reciprocal lattice vector direction k1 and the second reciprocal lattice vector direction k2 is equal. The two-dimensional structural element 32 rotates along the second rotation direction (the direction from the second lattice period direction a2 to the first lattice period direction a1), which is Figure 5 The clockwise rotation of the 2D structural unit 32 forms a positive relative rotation angle with the direction of the lattice period vector sum of the 2D grating 31 (e.g. Figure 3 As shown in FIG, the diffraction efficiency of the outcoupling grating 30 in the second inverse lattice vector direction k2 is increased. Figure 4 In one example, when the angle between a1 and a2 is 60 degrees, the two-dimensional structural element 32 rotates 30 degrees clockwise (i.e., α2 = 30 degrees), so that the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector sum of the two-dimensional grating 31 form a relative rotation angle of 30 degrees, so that the diffraction efficiency of the outcoupling grating 30 in the second reciprocal lattice vector direction k2 is relatively strong (e.g., Figure 7 shown).

[0066] It should be noted that during the clockwise rotation of the two-dimensional structural element 32, the first lattice period direction a1 and the second lattice period direction a2 remain unchanged, and the first lattice period direction a1 and the second lattice period direction a2 determine the first reciprocal lattice vector direction k1 and the second reciprocal lattice vector direction k2. Therefore, the first reciprocal lattice vector direction k1 and the second reciprocal lattice vector direction k2 also remain unchanged. In this way, the spatial closure of the wave vector formed by the input light after interacting with the coupling-in grating 20 and the coupling-out grating 30 will not be affected. The rotation of the two-dimensional structural element 32 is only the rotation of the two-dimensional structural element 32 itself, for example Figure 3 The rectangle in the figure is rotated to change the characteristic axis direction of the two-dimensional structural element 32, thereby increasing the diffraction efficiency of the outcoupling grating 30 in the second reciprocal lattice vector direction k2.

[0067] See also Figure 3 、 Figure 8 and Figure 10 In some embodiments, the outcoupling grating 30 includes a second grating region 34 corresponding to the second reciprocal lattice vector. In the second grating region 34, the characteristic axis direction of the two-dimensional structural element 32 forms a positive relative rotation angle with the direction of the lattice period vector and the direction of the two-dimensional grating 31.

[0068] Specifically, when the light transmitted in the waveguide substrate 10 reaches the outcoupling grating 30, part of the light obtains the wave vector provided by the outcoupling grating 30. Propagate upwards, if we continue to obtain the wave vector provided by the outcoupling grating 30 If the wave vector space is closed, it will be coupled out from the waveguide substrate 10, and there is a problem of premature coupling. The second grating region 34 (eg Figure 8 By making the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector sum of the two-dimensional grating 31 form a positive relative rotation angle, the diffraction efficiency of the out-coupling grating 30 in the second reciprocal lattice vector direction k2 is increased, and then this part of the light continues to obtain the wave vector provided by the out-coupling grating 30. is more efficient due to the wave vector The direction is bidirectional, the wave vector With wave vector is symmetrical, so this part of the light continues to obtain the wave vector provided by the outcoupling grating 30 The efficiency will be higher, and the With the previously obtained The offsetting effect causes the light to not be coupled out immediately but to continue to propagate forward, thereby allowing the light to propagate more in a direction away from the coupling-in grating 20, thereby improving the uniformity of the display.

[0069] It should be pointed out that Figure 10The thick arrows represent the transmission of light in the waveguide substrate 10 , and the thin arrows represent the coupling of light out of the waveguide substrate 10 (the coupling direction is, for example, perpendicular to the paper and outward).

[0070] See also Figure 8 In some embodiments, the outcoupling grating 30 includes a third grating region 35 corresponding to the first reciprocal lattice vector direction and / or the second reciprocal lattice vector direction. Within the third grating region 35, the characteristic axis direction of the two-dimensional structural element 32 forms a negative relative rotation angle and / or a positive relative rotation angle with the direction of the lattice period vector sum of the two-dimensional grating 31.

[0071] Specifically, the embodiment of the present application requires both wave vector To allow light to propagate upwards, a wave vector is also required The third grating region 35 (e.g., the middle region of the outcoupling grating 30), which allows light to propagate downward, can cause the characteristic axis direction of the two-dimensional structural element 32 to form a positive or negative relative rotation angle with the direction of the lattice period vector sum of the two-dimensional grating 31. Alternatively, the characteristic axis directions of some two-dimensional structural elements 32 form a positive relative rotation angle with the direction of the lattice period vector sum of the two-dimensional grating 31, while the characteristic axis directions of some two-dimensional structural elements 32 form a negative relative rotation angle with the direction of the lattice period vector sum of the two-dimensional grating 31. In this way, light can be directed more away from the incoupling grating 20, thereby improving display uniformity. In one example, when the angle between a1 and a2 is 60 degrees, the relative rotation angle formed by the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector sum of the two-dimensional grating 31 can be between -30 degrees and 30 degrees.

[0072] In various embodiments of the present application, for different grating regions of the outcoupling grating 30, the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector sum of the two-dimensional grating 31 can be made to form different relative rotation angles as needed to optimize the light propagation path and the efficiency of the optical waveguide. The relative rotation angle can be between -90 degrees and 90 degrees.

[0073] See also Figure 8 and Figure 11 In some embodiments, the relative rotation angle changes gradually or in steps within the spatial range of the outcoupling grating 30 in a direction away from the incoupling grating 20 .

[0074] Specifically, if Figure 11As shown, one approach is to gradually adjust the diffraction efficiency of the outcoupling grating 30 in a predetermined direction by gradually rotating the characteristic axis of the two-dimensional structural element 32 and the direction of the sum of the lattice period vectors of the two-dimensional grating 31 to a relative angle. For example, when the desired relative rotation angle is 60 degrees, the characteristic axis of the two-dimensional structural element 32 and the direction of the sum of the lattice period vectors of the two-dimensional grating 31 are adjusted from no relative rotation angle to relative rotation angles of 20 degrees, 40 degrees, and 60 degrees, in sequence. In this case, the relative rotation angle gradually changes within the spatial range of the outcoupling grating 30, specifically gradually decreasing, in a direction away from the incoupling grating 20.

[0075] Another way is, Figure 8 As shown, in the region where the diffraction efficiency of the outcoupling grating 30 in a predetermined direction needs to be adjusted, the characteristic axis direction of the two-dimensional structural element 32 and the direction of the sum of the lattice period vectors of the two-dimensional grating 31 can be directly caused to form a relative rotation angle. For example, when the desired relative rotation angle is set to 60 degrees, the characteristic axis direction of the two-dimensional structural element 32 and the direction of the sum of the lattice period vectors of the two-dimensional grating 31 change from no relative rotation angle to a relative rotation angle of 60 degrees. At this time, in the direction away from the incoupling grating 20, the relative rotation angle changes in a step-like manner within the spatial range of the outcoupling grating 30, specifically, directly decreases.

[0076] Table 1 below shows simulation results for waveguide efficiency of an optical waveguide structure 100 according to an embodiment of the present application. Table 1 shows that for different colors of light, the direction of the characteristic axis of the two-dimensional structural element 32 forms a relative angle with the direction of the lattice period vector sum of the two-dimensional grating 31, significantly improving the waveguide efficiency.

[0077] Table 1

[0078]

[0079]

[0080] See also Figure 12 and Figure 13 , Figure 12 Schematic diagram of the spatial distribution of the outgoing light energy in the eye box area when there is no relative rotation angle between the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector and the two-dimensional grating 31. Figure 13 This is a schematic diagram of the spatial distribution of the emitted light energy in the eye box area after the rotation angle of the two-dimensional structural element 32 is changed so that the characteristic axis direction of the two-dimensional structural element 32 and the direction of the lattice period vector sum of the two-dimensional grating 31 form a relative rotation angle. Figure 12 and Figure 13It can be seen that by adjusting the rotation angle of the two-dimensional structural unit 32, the intensity of light propagating in different directions can be adjusted, thereby improving the energy emitted away from the coupling grating 20 and enhancing uniformity. In addition, the optical waveguide structure 100 of the embodiment of the present application does not increase the difficulty of the process.

[0081] See also Figure 14 The embodiment of the present application further provides an optical waveguide module 300 . The optical waveguide module 300 includes the optical waveguide structure 100 of any of the above embodiments and an optical engine 200 . The optical engine 200 is used to transmit input light to the coupling grating 20 .

[0082] In the optical waveguide module 300 of the embodiment of the present application, the characteristic axis direction of the two-dimensional structural element 32 forms a relative angle with the direction of the lattice period vector sum of the two-dimensional grating 31 to adjust the diffraction efficiency of the outcoupling grating 30 in a predetermined direction. In this way, the morphology of the grating can be optimized, thereby improving the efficiency of the optical waveguide.

[0083] See also Figure 15 The present application also provides a head-mounted display device 1000. The head-mounted display device 1000 includes the optical waveguide module 300 of the above embodiment. The head-mounted display device 1000 is, for example, an AR display device.

[0084] In the head-mounted display device 1000 of the embodiment of the present application, the characteristic axis direction of the two-dimensional structural element 32 forms a relative angle with the direction of the sum of the lattice period vectors of the two-dimensional grating 31 to change the diffraction efficiency of the outcoupling grating 30 in a predetermined direction. In this way, the morphology of the grating can be optimized, thereby improving the efficiency of the optical waveguide.

[0085] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0086] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or the interaction between two components. A person of ordinary skill in the art will be able to understand the specific meanings of the above terms in this application based on the specific circumstances.

[0087] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0088] The disclosure above provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described above. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art will appreciate the application of other processes and / or the use of other materials.

[0089] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "example," "specific example," and "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0090] Although the embodiments of the present application have been shown and described above, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and purpose of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. An optical waveguide structure, characterized in that: include: waveguide substrate; A coupling grating, used for coupling input light into the waveguide substrate and transmitting the light; An outcoupling grating is used to expand the pupil of the light transmitted in the waveguide substrate and couple it out. The outcoupling grating is a two-dimensional grating having a two-dimensional structural element. The characteristic axis direction of the two-dimensional structural element forms a relative angle with the direction of the lattice period vector sum of the two-dimensional grating to change the diffraction efficiency of the outcoupling grating in a predetermined direction.

2. The optical waveguide structure according to claim 1, wherein: The two-dimensional grating has a first lattice periodic direction and a second lattice periodic direction, and the number of the two-dimensional structural primitives is multiple, and the multiple two-dimensional structural primitives are arranged along the first lattice periodic direction and the second lattice periodic direction; The direction of the sum of the lattice period vectors of the two-dimensional grating is the direction of the sum of the vector in the first lattice period direction and the vector in the second lattice period direction.

3. The optical waveguide structure according to claim 2, wherein: The two-dimensional structural element has a first reciprocal lattice vector direction corresponding to the second lattice period direction and a second reciprocal lattice vector direction corresponding to the first lattice period direction. The characteristic axis direction of the two-dimensional structural element and the direction of the sum of the lattice period vectors of the two-dimensional grating form the relative rotation angle to change the diffraction efficiency of the out-coupling grating in the first reciprocal lattice vector direction or the second reciprocal lattice vector direction.

4. The optical waveguide structure according to claim 3, wherein: The first reciprocal lattice vector direction is perpendicular to the second lattice period direction, and the second reciprocal lattice vector direction is perpendicular to the first lattice period direction.

5. The optical waveguide structure according to claim 3, wherein: The size of the relative rotation angle is determined based on the first lattice period length, the second lattice period length, and the angle between the first lattice period direction and the second lattice period direction.

6. The optical waveguide structure according to claim 3, wherein: The two-dimensional structural element rotates along a first rotation direction so that the characteristic axis direction of the two-dimensional structural element and the direction of the sum of the lattice period vectors of the two-dimensional grating form a negative relative rotation angle, so as to increase the diffraction efficiency of the out-coupling grating in the direction of the first reciprocal lattice vector; wherein the first rotation direction is the direction of rotation from the first lattice period direction to the second lattice period direction.

7. The optical waveguide structure according to claim 6, wherein: The outcoupling grating includes a first grating region corresponding to the first reciprocal lattice vector direction. In the first grating region, the characteristic axis direction of the two-dimensional structural element and the direction of the lattice period vector sum of the two-dimensional grating form the negative relative rotation angle.

8. The optical waveguide structure according to claim 3, wherein: The two-dimensional structural element rotates along a second rotation direction so that the characteristic axis direction of the two-dimensional structural element and the direction of the lattice period vector sum of the two-dimensional grating form a positive relative rotation angle, so as to increase the diffraction efficiency of the out-coupling grating in the direction of the second reciprocal lattice vector; wherein the second rotation direction is the direction of rotation from the second lattice period direction to the first lattice period direction.

9. The optical waveguide structure according to claim 8, wherein: The outcoupling grating includes a second grating region corresponding to the second reciprocal lattice vector direction. In the second grating region, the characteristic axis direction of the two-dimensional structural element and the direction of the lattice period vector sum of the two-dimensional grating form the positive relative rotation angle.

10. The optical waveguide structure according to claim 3, wherein Along the direction away from the coupling-in grating, the relative rotation angle changes gradually or in steps within the spatial range of the coupling-out grating.

11. An optical waveguide module, characterized in that: include: The optical waveguide structure according to any one of claims 1 to 10; and An optical engine is used to transmit input light to the coupling-in grating.

12. A head-mounted display device, characterized in that: The optical waveguide module according to claim 11 is included.

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