Diffractive waveguide device, near-eye display device, and method of manufacture

Abstract

The application provides a diffraction waveguide device, which comprises a waveguide substrate and a grating structure, the grating structure is arranged on the surface of the waveguide substrate, the grating structure comprises a plurality of grating units, the plurality of grating units have a first period in a first direction and a second period in a second direction different from the first direction, the two-dimensional pupil expanding angle of the grating structure is 180° by adjusting the first period and the second period. The effective coupling-out grating area of the grating structure of the application is approximately rectangular, therefore, the grating structure does not need part of the grating units to only perform pupil expanding, the area of the grating units of the grating structure used for effective coupling-out is increased, the effective display area of the grating structure is increased, and the grating utilization rate is improved. The application also provides a near-eye display device provided with the diffraction waveguide device and a manufacturing method of the diffraction waveguide device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diffractive optical devices, in particular to a diffractive light waveguide device, a near-eye display device provided with the diffractive light waveguide device, and a manufacturing method of the diffractive light waveguide device. BACKGROUND

[0002] With the development of technology, Augmented Reality (AR) display devices, such as AR glasses, need to see both the external real world and virtual images. A near-eye display device usually includes a diffractive waveguide system. Existing diffractive waveguide systems based on gratings are divided into two categories. The first category is a diffractive waveguide system with three or more one-dimensional grating regions. The second category is a two-dimensional diffractive waveguide system with two grating regions. The first category of diffractive waveguide system includes a waveguide substrate, a coupling-in grating, a turning grating, and a coupling-out grating. The light of a display image generated by an image source enters the waveguide substrate through the coupling-in grating, is expanded by the turning grating, and then is coupled out by the coupling-out grating to be emitted to the human eye. The two-dimensional diffractive waveguide system includes a waveguide substrate, a coupling-in grating, and a two-dimensional coupling-out grating. The light of a display image generated by an image source enters the waveguide substrate through the coupling-in grating, and then is coupled out by the coupling-out grating to be emitted to the human eye.

[0003] However, the first category of diffractive waveguide system described above has a turning grating that occupies the area of the waveguide substrate, resulting in a small setting area of the coupling-out grating, low utilization rate of the waveguide substrate, and limited eye box. Figure 1 As shown in FIG. 1, the existing two-dimensional grating in the second category of diffractive waveguide system mainly uses a periodic structure of a hexagonal lattice. The expansion angle of the periodic structure is 120°. Therefore, a part of the grating region needs to be expanded, i.e., the grating region on the left side of the dashed box a0 in FIG. 1 is not used for coupling-out, resulting in a reduced effective coupling-out grating area. Figure 1 SUMMARY

[0004] The first aspect of the present application provides a diffractive waveguide device, which includes:

[0005] a waveguide substrate; and

[0006] a grating structure disposed on the surface of the waveguide substrate, the grating structure including a plurality of grating units having a first period in a first direction and a second period in a second direction different from the first direction, the first period and the second period being adjusted to make the two-dimensional expansion angle of the grating structure 180°.

[0007] ​The effective coupling-out grating area of the grating structure of the application is approximately rectangular, thus, the grating structure does not need part of the grating units to only perform pupil expansion, the area of the grating units of the grating structure used for effective coupling-out is increased, the effective display area of the grating structure is increased, and the grating utilization rate is improved.

[0008] The second aspect of the application further provides a near-eye display device, which comprises the diffractive waveguide device of the first aspect.

[0009] The near-eye display device of the application sets the two-dimensional pupil expansion angle of the grating structure to 180° through the diffractive waveguide device, so that the effective coupling-out grating area of the diffractive waveguide device is approximately rectangular, the grating structure does not need part of the grating units to only perform pupil expansion, the area of the grating units of the grating structure used for effective coupling-out is increased, the effective display area of the grating structure is increased, and the grating utilization rate is improved.

[0010] The third aspect of the application provides a manufacturing method of a diffractive waveguide device, comprising:

[0011] providing a waveguide substrate; and

[0012] forming a grating structure on a surface of the waveguide substrate, wherein the grating structure comprises a plurality of grating units, the plurality of grating units have a first period in a first direction and a second period in a second direction different from the first direction, and the values of the first period and the second period are adjusted so that the two-dimensional pupil expansion angle of the grating structure is 180°. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a schematic diagram of light pupil expansion of a two-dimensional coupling-out grating of the prior art;

[0014] Figure 2 is a schematic diagram of the use state of the diffractive waveguide device provided by the first embodiment of the application;

[0015] Figure 3 is Figure 2 a schematic diagram of the structure of the partial grating structure and the waveguide substrate of the diffractive waveguide device in

[0016] Figure 4 is Figure 3 a schematic diagram of light pupil expansion of the grating structure in

[0017] Figure 5 is Figure 3 a front view schematic diagram of the grating structure in

[0018] Figure 6 is a schematic diagram of light propagation of a diffraction grating;

[0019] Figure 7 and Figure 8 is a schematic diagram of rainbow fringes corresponding to different incident angles of sunlight for a diffraction grating;

[0020] Figure 9 is a K-space analysis diffraction schematic diagram of the grating structure provided by one embodiment;

[0021] Figure 10 is a K-space analysis diffraction schematic diagram of the grating structure provided by the preferred mode of the present application;

[0022] Figure 11 is a schematic diagram of the grating structure in Figure 3 ;

[0023] Figure 12 is a schematic diagram of the grating structure provided by the second embodiment of the present application;

[0024] Figure 13 is a K-space analysis diffraction schematic diagram of the grating structure in Figure 12 ;

[0025] Figure 14 is a schematic diagram of the grating structure provided by the third embodiment of the present application;

[0026] Figure 15 is a K-space analysis diffraction schematic diagram of the grating structure in Figure 14 ;

[0027] Figure 16 is a schematic diagram of the grating structure in Figure 14 ;

[0028] Figures 17-23 is a schematic diagram of the grating structure provided by the fourth embodiment to the tenth embodiment of the present application;

[0029] Figure 24 is a schematic diagram of the grating structure provided by the eleventh embodiment of the present application;

[0030] Figure 25 is a schematic diagram of the grating structure provided by the twelfth embodiment of the present application;

[0031] Figure 26 is a schematic diagram of the grating structure provided by the thirteenth embodiment of the present application;

[0032] Figure 27 is a schematic diagram of the grating structure provided by the fourteenth embodiment of the present application;

[0033] Figure 28 is a schematic diagram of the in-coupling grating and the out-coupling grating of the diffraction waveguide device provided by the fifteenth embodiment of the present application;

[0034] Figure 29is Figure 1 a ray propagation schematic of a two-dimensional out-coupling grating in

[0035] Figure 30 is Figure 28 a ray propagation schematic of an out-coupling grating in

[0036] Figure 31 is Figure 29 a rainbow fringe simulation schematic of (1, 1) order diffraction of a two-dimensional out-coupling grating in

[0037] Figure 32 is Figure 30 a rainbow fringe simulation schematic of (1, 0) order diffraction of an out-coupling grating in

[0038] Figure 33 is Figure 29 a rainbow fringe simulation schematic of (1, 0) order diffraction and (0, 1) order diffraction of a two-dimensional out-coupling grating in

[0039] Figure 34 is Figure 30 a rainbow fringe simulation schematic of (1, -1) order diffraction and (1, 1) order diffraction of an out-coupling grating in

[0040] Figure 35 is a schematic diagram of an in-coupling grating and an out-coupling grating of a diffractive waveguide device provided by a sixteenth embodiment of the present application;

[0041] Figure 36 is a structural schematic diagram of a diffractive waveguide device provided by a seventeenth embodiment of the present application;

[0042] Figure 37 is a structural schematic diagram of a diffractive waveguide device provided by an eighteenth embodiment of the present application;

[0043] Figure 38 is a structural schematic diagram of a diffractive waveguide device provided by a nineteenth embodiment of the present application;

[0044] Figure 39 is a structural schematic diagram of a diffractive waveguide device provided by a twentieth embodiment of the present application;

[0045] Figure 40 is a structural schematic diagram of a diffractive waveguide device provided by a twenty-first embodiment of the present application;

[0046] Figure 41 is a structural schematic diagram of a diffractive waveguide device provided by a twenty-second embodiment of the present application;

[0047] Figure 42 is a schematic diagram of a near-eye display device provided by an embodiment of the present application;

[0048] Figure 43is a schematic diagram of a near-eye display device provided by another embodiment of the present application;

[0049] Figure 44 is a schematic diagram of a near-eye display device provided by another embodiment of the present application;

[0050] Figure 45 is a schematic diagram of a near-eye display device provided by another embodiment of the present application;

[0051] Figure 46 is a schematic diagram of a near-eye display device provided by another embodiment of the present application;

[0052] Figure 47 is a flow chart of a manufacturing method of a diffractive waveguide device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be apparently and completely described in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those of ordinary skill in the art without any creative work fall within the scope of protection of the present application.

[0054] It should be noted that, in the present document, the term “embodiment” or “implementation” means that the specific features, structures or characteristics described in combination with the embodiment or implementation can be included in at least one embodiment of the present application. The appearance of this phrase at various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment to other embodiments. Those of ordinary skill in the art explicitly and implicitly understand that the embodiments described in the present document can be combined with other embodiments.

[0055] The terms “first”, “second” appearing in the present application are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with “first”, “second” can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of “multiple” is two or more, unless otherwise specifically limited.

[0056] Please refer to Figures 2 to 5 , Figure 2 is a schematic diagram of a diffractive waveguide device 20 provided by a first embodiment of the present application in a use state; Figure 3 is Figure 2 is a schematic diagram of a part of grating structure 22 and waveguide substrate 21 of the diffractive waveguide device 20 in Figure 4 is Figure 3A schematic diagram of the light pupil expanding of the grating structure 22 in FIG. 1; Figure 5 is Figure 3 A front view schematic diagram of the grating structure 22 in FIG. 1. The present application provides a diffractive waveguide device 20 which can be used in AR glasses and can also be applied to devices with windshields such as cars. The diffractive waveguide device 20 will be described in detail below. The diffractive waveguide device 20 includes a waveguide substrate 21 and a grating structure 22 disposed on the surface of the waveguide substrate 21, the grating structure 22 includes a plurality of grating units 221, the plurality of grating units 221 have a first period in a first direction and a second period in a second direction different from the first direction, by adjusting the first period and the second period, the two-dimensional pupil expanding angle of the grating structure 22 is 180°. In the present application, the first period includes the first direction and a first mode length extending along the first direction, and the second period includes the second direction and a second mode length extending along the second direction; by adjusting the direction of the first direction and the size of the first mode length of the grating structure 22, and the direction of the second direction and the size of the second mode length, the two-dimensional pupil expanding angle of the grating structure 22 is 180°.

[0057] The plurality of grating units 221 can be arranged to form an out-coupling grating 222 and / or an in-coupling grating 225, the in-coupling grating 225 is used to couple light into the waveguide substrate 21, and the out-coupling grating 222 is used to receive light after total reflection in the waveguide substrate 21, and to couple out the light after two-dimensional pupil expanding from the waveguide substrate 21.

[0058] In Figure 4 The light is represented by dashed lines in FIG. 1. When the diffractive waveguide device 20 is used, the waveguide substrate 21 can be considered to be in the XY plane, and each grating unit 221 extends along the Z axis.

[0059] When the diffractive waveguide device 20 is used, the light of the display image generated by the image source 30 enters the waveguide substrate 21 through the in-coupling grating 225, is totally reflected in the waveguide substrate 21, and then is incident on the out-coupling grating 222, and then is emitted to the human eye 50 after being coupled out by the out-coupling grating 222. Because the two-dimensional pupil expanding angle of the grating structure 22 is 180°, compared with the two-dimensional grating in the prior art, the effective out-coupling grating area of the grating structure 22 is approximately rectangular, therefore, the grating structure 22 does not need part of the grating units 221 to only perform pupil expanding, that is, the plurality of grating units 221 do not have invalid out-coupling gratings, so that the area of the grating units 221 used for effective coupling out of the grating structure 22 is increased, the effective display area of the grating structure 22 is increased, and the grating utilization rate is improved.

[0060] The image source 30 is a device that generates the original image, and the image source 30 may include, but is not limited to, a Micro-LED display screen, a projection optical engine, etc.

[0061] The waveguide substrate 21, also known as an optical waveguide substrate, dielectric optical waveguide substrate, or waveguide substrate sheet, is the medium in which light is guided to propagate. Optical waveguide substrates generally fall into two main categories: integrated optical waveguide substrates, including planar (thin-film) dielectric optical waveguide substrates and strip-shaped dielectric optical waveguide substrates, which are typically part of optoelectronic integrated devices (or systems), hence the name integrated optical waveguide substrates; and cylindrical optical waveguide substrates, commonly referred to as optical fibers. Typically, the waveguide substrate 21 is a guiding structure for transmitting light (optical frequency electromagnetic waves) made of an optically transparent medium (such as quartz glass). When light propagates within the waveguide substrate 21, total internal reflection occurs within the optical waveguide substrate 21, confining the light propagation within the waveguide substrate 21.

[0062] Total internal reflection refers to the transmission of light without loss or leakage. It requires "total internal reflection" so that the light travels back and forth in the waveguide substrate through a wave shape and does not transmit. Total internal reflection requires two conditions: (1) the transmission medium, i.e. the waveguide substrate, must have a higher refractive index than the surrounding medium; (2) the angle of incidence of the light into the waveguide substrate must be greater than the critical angle.

[0063] like Figure 2 and Figure 3 As shown, the waveguide substrate 21 includes a first surface 211 and a second surface 213 disposed opposite to each other. The first surface 211 refers to the surface facing away from the user's eye 50 when the diffraction waveguide device 20 is used; the second surface 213 refers to the surface close to the user's eye 50 when the diffraction waveguide device 20 is used. In this embodiment, the grating unit 221 is a protruding structure protruding from the surface of the waveguide substrate 21, that is, the grating unit 221 protrudes from the first surface 211 of the waveguide substrate 21. Specifically, the grating unit 221 has a cylindrical structure, the axial direction of the grating unit 221 is perpendicular to the xy plane, that is, the grating unit 221 extends along the Z-axis, and the transverse surface of the grating unit 221 parallel to the xy plane is circular. The first surface 211 is a plane parallel to the xy plane. These grating units 221 are arranged in a rectangle on the first surface 211 at intervals of the first modulus length along the first direction (i.e., along the x-axis) and the second modulus length along the second direction (i.e., along the y-axis). The height of the grating units 221 is the same, that is, the length of each grating unit 221 extending along the Z-axis is the same. Therefore, the end faces of each grating unit 221 that are away from the first surface 211 are coplanar.

[0064] The in-coupling grating 225 is carried on the waveguide substrate 21, specifically including the following cases: the in-coupling grating 225 is arranged on the first surface 211 of the waveguide substrate 21, or the in-coupling grating 225 is arranged on the second surface 213 of the waveguide substrate 21. In the embodiment, the in-coupling grating 225 is arranged on the first surface 211 of the waveguide substrate 21. The process of coupling light into the waveguide substrate 21 by the in-coupling grating 225 is also called light in-coupling. The out-coupling grating 222 and the in-coupling grating 225 are both diffraction gratings. A diffraction grating refers to an optical element with a periodic structure. The period can be a high peak and a low valley of a material surface relief, or a "light and dark interference fringe" formed by holographic technology in the material. In the present application, the diffraction grating is a convex structure protruding from the surface of the waveguide substrate 21. Ultimately, the diffraction grating causes a periodic change in the refractive index in the material. The period is generally on the order of microns or nanometers, which is on the same order of magnitude as the wavelength of visible light (~450nm-700nm), so that the light can be effectively manipulated.

[0065] Please refer to Figure 6 , Figure 6 is a schematic diagram of light propagation of a diffraction grating. The "light splitting" of a diffraction grating is realized in two dimensions. Assuming that the incident light is single-wavelength green light, it will be split into several diffraction orders by the diffraction grating, and each diffraction order will continue to propagate in a different direction, including reflected diffraction light and transmitted diffraction light. The reflected diffraction includes diffraction orders such as 0th order, ±1st order, ±2nd order, etc. The transmitted diffraction includes diffraction orders such as 0th order, ±1st order, ±2nd order, etc. The diffraction angle corresponding to each diffraction order is determined by the incident angle of the light and the period of the grating. Therefore, by designing other parameters of the grating such as material refractive index, grating shape, thickness, duty cycle, etc., the diffraction efficiency of a certain diffraction order (i.e. a certain direction) can be optimized to the highest, so that most of the light will propagate mainly in this direction after diffraction.

[0066] Pupil expansion refers to the process that when light propagates in the waveguide substrate 21 and passes through the grating structure 22, part of the light will be coupled out of the waveguide substrate 21 by diffraction, and the remaining light will be diffracted again by the grating structure 22 to continue total reflection transmission in the waveguide substrate 21. This cycle continues, and finally light is coupled out of the entire grating structure 22, so that the human eye 50 can see a complete and continuous image at any position.

[0067] The so-called augmented reality (AR) refers to that light rays of an image to be displayed generated by the image source 30 in the near-eye display device are coupled into the waveguide substrate through the in-coupling grating and then coupled out through the out-coupling grating to be emitted to the human eye. External environment light rays (such as sunlight outdoors or light generated by indoor lighting lamps) can also be transmitted through the in-coupling grating to the human eye, so that the user can view the image in the image source and the image in the external environment, thereby realizing the augmented reality function of virtual and real combination.

[0068] Specifically, as shown in Figure 2 The image source 30 is a Lambertian light source, and the light emitted by the image source 30 is incident on an ideal lens (not shown in the figure). The ideal lens collimates the incident light and then emits the collimated light to the in-coupling grating 225. When the light is diffracted by the in-coupling grating 225, the light propagates in the waveguide substrate 21 in the form of total reflection to the out-coupling grating 222. When the total reflection light is diffracted by the out-coupling grating 222, the light is coupled out to the air, and then is incident on the human eye 50 of the user, so that the human eye 50 can see the virtual image. The region of the in-coupling grating 225 can also transmit the ambient light, thereby realizing the effect of augmented reality. The angles of the light rays incident on the in-coupling grating 225 are different, which represents the field of view of the diffractive waveguide device. The larger the field of view of the diffractive waveguide device is designed, the larger the angle of the light incident on the in-coupling grating 225 is. For the in-coupling grating 225, the larger the field of view of the diffractive waveguide device is, the larger the incident angle of the out-coupling grating 222 is, and the larger the angle of the out-coupled light is. Therefore, in the actual design of the diffractive waveguide device 20, the period and topography of the out-coupling grating 222 are generally controlled to be consistent with those of the in-coupling grating 225, and only the height (i.e., the length of the grating unit along the Z axis) of the grating unit 221 is different. It can be considered that the in-coupling grating 225 and the out-coupling grating 222 are a pair of conjugate systems, and only the diffraction efficiency is different.

[0069] Generally, the diffractive waveguide device includes an in-coupling grating and an out-coupling grating to realize two-dimensional pupil expansion. The image source enters the waveguide substrate through the in-coupling grating, and then exits to the human eye through the out-coupling grating. The external environment light can also be transmitted to the human eye through the in-coupling grating, thereby realizing the augmented reality function of virtual and real combination. Since the in-coupling grating and the out-coupling grating both have strong dispersion function, when the relatively strong external environment light (such as sunlight or lighting light source) is incident, the incident light of the external environment light is dispersed into rainbow stripes by the diffraction grating, and is mainly generated by-1 order reflection type diffraction and-1 order transmission type diffraction. Figure 7 and Figure 8As shown, the -1 order reflection diffracted light cannot enter the human eye, thus has no impact on the user experience, while the -1 order transmission diffracted light can enter the human eye, making the user see rainbow stripes, which may affect the user experience or even harm the human eye. It should be noted that whether the rainbow stripes formed by the -1 order transmission diffraction can enter the eyes of the user wearing the diffraction waveguide device 20 is related to the incident angle of the external environment light. For example, when the external environment light is incident at an angle of 50° to the out-coupling grating, the rainbow stripes formed by the -1 order transmission diffraction have a large exit angle a°, and the diffracted light is more likely to deviate from the observation position of the user's eyes. Even if it enters the user's eyes, due to the large diffraction angle a°, the rainbow stripes will appear in the peripheral area of the field of view. When the external environment light is incident at an angle of 80° to the in-coupling grating, the rainbow stripes formed by the -1 order transmission diffraction have a small exit angle a°, and the diffracted light is more likely to enter the human eye and is closer to the center of the field of view, which has a greater impact on the user.

[0070] As shown in Figure 4 , the diffraction waveguide device 20 of the present application uses the grating structure 22 to expand the pupil in two dimensions, and the two-dimensional expansion angle is 180°, which is different from the two-dimensional grating in the diffraction waveguide system in Figure 1 , which has an expansion angle of 120°, so that the effective coupling-out area of the grating structure 22 is increased, the effective display area of the grating structure 22 is increased, and the grating utilization rate is improved. In the present embodiment, the included angle θ of the grating structure 22 is 90°, i.e. the grating structure 22 has a first base vector a x and a second base vector a y , the included angle θ of the first base vector a x and the second base vector a y is 90°, and the first base vector a x and the second base vector a y are respectively the first direction and the second direction of the plurality of grating units 221. In Figure 4 , the first direction is parallel to the x-axis direction, and the second direction is parallel to the y-axis direction. The grating structure 22 uses a square or rectangular lattice with a base vector included angle θ of 90° to achieve pupil expansion. In general, in the square or rectangular lattice diffraction process, 1 order diffraction and -1 order diffraction play a major role, resulting in a decrease in the efficiency of the vertical pupil expansion direction, and a decrease in the effective coupling-out area of the grating. Therefore, in the present application, the 1 order diffraction and -1 order diffraction can be shielded by designing the parameters of the square or rectangular lattice, so as to improve the efficiency of the vertical pupil expansion and increase the effective area of the grating structure.

[0071] As shown in Figure 5As shown, the technical principle is analyzed below by taking the grating cells 221 of the grating structure 22 arranged in a long square lattice as an example. The grating cells 221 arranged in a square lattice is only a special case of the long square lattice with equal periods (i.e. equal first mode length) in the first direction and equal periods (i.e. equal second mode length) in the second direction. Specifically, the grating cells 221 arranged in a long square lattice have a first primitive vector a x and a second primitive vector a y , where a x ⊥a y . When the periods are equal (i.e. the first mode length is equal to the second mode length), i.e. a x =a y , the grating cells 221 are arranged in a square lattice. The reciprocal lattice vector k x of the long square lattice in which the grating cells 221 are arranged is k x =2πe x / |a y |, k y =2πe y / |a x |, and the diffraction orders are linear superpositions based on these two vectors; where a y is the period (i.e. the first mode length) of the grating structure 22 in the x direction, a x is the period (i.e. the second mode length) of the grating structure 22 in the y direction, k y is the x-direction grating vector in the reciprocal space, and k x is the y-direction grating vector.

[0072] In the diffraction waveguide device 20, the generally used diffraction orders are combinations of -1 order diffraction, 0 order diffraction, +1 order diffraction in the x direction and -1 order diffraction, 0 order diffraction, +1 order diffraction in the y direction, where the (0, 0) order is the 0 order diffraction. As shown, Figure 9 Figure 9 is a K-space analysis diffraction diagram of the grating structure provided by one embodiment, where the horizontal axis is λk y / 2π and the vertical axis is λk x is the x-direction grating vector in the reciprocal space, and k y is the y-direction grating vector.Let λ be the grating vector in the y-direction of the reciprocal space. Multiplying the k vector by λ / 2π is for unit normalization. The figure shows nine fields of view from D0 to D8, where D0 is the (0,0) order diffraction (i.e., 0th order diffraction), D1 is the (-1,0) order diffraction (i.e., the central field of view), D2 is the (-1,1) order diffraction, D3 is the (-1,-1) order diffraction, D4 is the (0,1) order diffraction, D5 is the (0,-1) order diffraction, D6 is the (1,1) order diffraction, D7 is the (1,0) order diffraction, and D8 is the (1,-1) order diffraction. If the field of view is within the inner circle R1, the waveguide can be coupled out; if the field of view is within the ring formed by the inner circle R1 and the outer circle R2, it means that the light will propagate within the waveguide substrate 21; if the field of view is outside the outer circle R2, it means that these lights do not actually exist. The field of view outside the outer circle R2 is shown here only to illustrate the diffraction order.

[0073] The central field of view D1 (i.e., (-1, 0) order diffraction) is coupled into the waveguide substrate 21 via a coupling grating, which is the filled rectangle in the figure (i.e., D0). The field of view coupled into the waveguide is then diffracted through the output grating 222 onto the various order diffraction fields D1-D8. Without considering the presence of light, we analyze... Figure 9 The diagram shows nine rectangular regions (i.e., nine fields of view). The filled rectangular region represents the (0, 0) order diffraction (i.e., field of view D0), and the region at the origin (i.e., field of view D1) represents the coupled waveguide. In the other diffraction fields of view (i.e., fields of view D2-D8), we can see that the three rightmost fields of view (i.e., fields of view D6-D8) cannot exist at all, so they do not need to be described. The remaining four fields of view (i.e., fields of view D2-D5) have diffraction orders of (0, ±1) order and (-1, ±1) order, respectively. In the diagram, part of the (0, ±1) order diffraction fields of view (i.e., fields of view D4 and D5) can propagate within the waveguide substrate 21, while the other part cannot exist. However, if the fields of view of the two diffraction orders (0, ±1) in the figure (i.e., fields of view D4 and D5) are coupled out again through grating diffraction, it will result in extremely uneven brightness of the fields of view. At the same time, the presence of the two diffraction orders (0, ±1) will greatly reduce the diffraction efficiency of the (-1, ±1) order diffraction, resulting in a reduction in the effective grating area.

[0074] Based on the above analysis, diffraction of the (0, ±1) diffraction order is avoided by designing the period size of the grating structure 22 and the aspect ratio of the rectangular lattice. Specifically, by designing the size of the first period (i.e., the first mode length) in the first direction and the second period (i.e., the second mode length) in the second direction of the plurality of grating units 221 of the grating structure 22, and by adjusting the aspect ratio of the rectangular lattice formed by the plurality of grating units 221 of the grating structure 22, the diffraction field of view of the (0, ±1) diffraction order is compressed to the outer circle R2 (e.g., ...).Figure 10 In the present application, the first mode length of the first period is 260-500 nm, the second mode length of the second period is 260-500 nm, and the aspect ratio of the rectangular lattice is between 0.5 and 2.

[0075] As Figure 10 shown, Figure 10 is a K-space analysis diffraction schematic diagram of the grating structure 22 provided by the preferred mode of the present application. By designing the direction and size of the period of the grating structure 22, the central field of view D1 is located within the inner circle R1, the (0, 0) order diffraction field of view D0, the (-1, +1) order diffraction field of view D2 and the (-1, -1) order diffraction field of view D3 are located in the annulus formed by the inner circle R1 and the outer circle R2, and the (0, +1) order diffraction field of view D4 and the (0, -1) order diffraction field of view D5 are located outside the outer circle R2, so as to avoid (0, ±1) order diffraction. At this time, the grating structure 22 can not only ensure the effective grating area, but also ensure the pupil expansion efficiency. From Figure 10 It can be seen from the above that there are three paths for the field of view of the coupling-in waveguide to couple out of the waveguide: the first path is to couple out of the waveguide through (-1, 0) order diffraction, and the second path and the third path are to expand the pupil orthogonally to the left and right sides respectively through (-1, ±1) order diffraction and then couple out of the waveguide through (0, ±1) order diffraction. Since the (0, ±1) order diffraction of the grating structure 22 is suppressed, the light rays have only (-1, ±1) order diffraction in addition to (0, 0) order diffraction, and therefore, for the light rays of the central field of view D1, the projections of the two diffractions in the horizontal plane (i.e. the XY plane) are perpendicular to the propagating light rays of the coupling-in, so that ±90° orthogonal pupil expansion is achieved, forming a 180° pupil expansion area.

[0076] As Figure 11 shown, Figure 11 is Figure 3 a schematic diagram of the light pupil expansion of the grating structure in the above. When the light rays are incident on the grating structure 22, the grating unit 221 achieves ±90° orthogonal pupil expansion, forming a 180° pupil expansion area, so that the coupling-out grating area a1 of the grating structure 22 is rectangular. Therefore, the effective coupling-out grating area of the grating structure 22 is increased, the effective display area of the grating structure 22 is increased, and the grating utilization rate is improved.

[0077] In other embodiments, the first direction of the first period of the grating structure and the second direction of the second period are at an angle of 90°, and the first mode length of the first period and the first mode length of the second period are not equal, so that the aspect ratio of the grating structure is between 0.5 and 2, i.e., the grating structure is a long rectangular lattice. Specifically, the mode length of the first period is greater than or equal to N times the mode length of the second period, and the N ranges from 0.5 to 2. The grating structure is the same as the grating structure 22 in the first embodiment, i.e., the out-coupling grating region of the grating structure is rectangular, so that the grating structure can form a 180° pupil expansion region, increase the effective out-coupling grating region, increase the effective display area of the grating structure, and improve the grating utilization rate.

[0078] Please refer to Figure 12 and Figure 13 , Figure 12 is a schematic diagram of the grating structure 22a provided in the second embodiment of the present application; Figure 13 is Figure 12 a K-space analysis diffraction schematic diagram of the grating structure 22a in Figure 12 . The grating structure 22a provided in the second embodiment of the present application is similar to the grating structure 22 in the first embodiment, and the difference is that the period of the first base vector P x and the second base vector P y of the grating structure 22a in the second embodiment are equal, i.e., the grating unit 221 of the grating structure 22a is a square lattice. Specifically, the first base vector P x direction of the grating structure 22a and the second base vector P y direction are perpendicular to each other, and the period (i.e., the first mode length) of the first base vector P x is equal to the period (i.e., the second mode length) of the second base vector P y , i.e., P x = P y . The corresponding reciprocal lattice vectors are:

[0079]

[0080]

[0081] The relationship between the reciprocal lattice vectors is k x0 ⊥ k y0 , |k x0 | = |k y0 |. Wherein, P x is the period (i.e., the mode length) of the two-dimensional grating in the x direction, P y is the period (i.e., the mode length) of the two-dimensional grating in the y direction, k x0 is the x direction grating vector in the reciprocal space, and k y0In the reverse space, the y-direction grating vector is. The (0, ±1) order diffraction of the square lattice is suppressed, except for the (0, 0) 0th order diffraction (i.e. the field of view D0), the light rays only have (-1, ±1) order diffraction (i.e. the field of view D2, D3). For the light rays of the central field of view D1, the projections of the two diffractions on the horizontal plane are both perpendicular to the coupled-in propagation light rays, therefore, the grating structure 22a can achieve a ±90° orthogonal pupil expansion to form a 180° pupil expansion area, so that the effective coupling-out grating area of the grating structure 22a is increased, the effective display area of the grating structure 22a is increased, and the grating utilization rate is improved; at the same time, unnecessary coupling-out can be reduced, and the overall efficiency of the diffraction waveguide device can be improved.

[0082] Please refer to Figures 14 to 16 , Figure 14 , which is a schematic diagram of the grating structure 22b provided by the third embodiment of the present application. Figure 15 is a K-space analysis diffraction schematic diagram of the grating structure 22b in Figure 14 . Figure 16 is a light ray pupil expansion schematic diagram of the grating structure 22b in Figure 14 . The grating structure 22b provided by the third embodiment of the present application is similar to the grating structure 22 of the first embodiment, and the difference is that the angle θ between the first base vector P x and the second base vector P y ranges from 80° to 100°, the period (i.e. the module length) of the first base vector P x is different from the period (i.e. the module length) of the second base vector P y , and the aspect ratio is between 0.5 and 2; that is, the angle θ between the first direction and the second direction of the grating structure 22b ranges from 80° to 100°, and the period (i.e. the module length) of the first base vector P x is equal to N times the period (i.e. the module length) of the second base vector P y , and the range of N is: 0.5≤N≤2. In this embodiment, the angle θ is 80°, and N is equal to 1. The grating units 221 of the grating structure 22b are arranged in a rhombic lattice, which is obtained by deforming the rectangular lattice formed by the grating structure 22 in the first embodiment, therefore, the effect of two-dimensional pupil expansion of the grating structure 22b is similar to that of the grating structure 22 of the first embodiment, and the same pupil expansion target can also be approximately achieved.

[0083] As Figure 15 and Figure 16As shown, although the two-direction pupil expansion angles of the grating structure 22b vary according to the size of the included angle θ between the first direction and the second direction, the pupil expansion included angle of the central field of view D1 remains 180°, so that the coupling-out grating area of the grating structure 22b is a parallelogram (i.e. a rhombic lattice), that is, the coupling-out grating area of the grating structure 22b is similar to a rectangle, and therefore, the pupil expansion effect of the grating structure 22b is similar to that of the grating structure 22 in the first embodiment. Compared with the two-dimensional grating in the prior art, the effective coupling-out grating area of the grating structure 22b is increased, the effective display area of the grating structure 22b is increased, the grating utilization rate is improved, and the overall efficiency of the diffractive waveguide device is improved.

[0084] Please refer to Figures 17 to 23 , Figures 17-23is a schematic view of the grating structure provided by the fourth embodiment to the tenth embodiment of the present application. The grating structure provided by the fourth embodiment to the tenth embodiment of the present application is similar to the grating structure 22 of the first embodiment, and the difference is that the shape of the grating unit 221c of the grating structure provided by the fourth embodiment to the tenth embodiment is different from the grating unit 221 of the first embodiment. Specifically, the grating unit 221c of the grating structure 22c of the fourth embodiment is an elliptical cylindrical structure, the axis of the grating unit 221c is perpendicular to the xy plane, and the grating unit 221c is an ellipse on the lateral surface parallel to the xy plane; the grating unit 221d of the grating structure 22d of the fifth embodiment is a square cylindrical structure, the square cylindrical structure is perpendicular to the xy plane, and the grating unit 221d is a square on the lateral surface parallel to the xy plane; the grating unit 221e of the grating structure 22e of the sixth embodiment is a rectangular cylindrical structure, the rectangular cylindrical structure is perpendicular to the xy plane, and the grating unit 221e is a rectangle on the lateral surface parallel to the xy plane; the grating unit 221f of the grating structure 22f of the seventh embodiment is a prismatic structure, the prismatic structure is perpendicular to the xy plane, and the grating unit 221f is a prismatic shape on the lateral surface parallel to the xy plane; the grating unit 221g of the grating structure 22g of the eighth embodiment is a triangular cylindrical structure, the triangular cylindrical structure is perpendicular to the xy plane, and the grating unit 221g is a triangle on the lateral surface parallel to the xy plane; the grating unit 221h of the grating structure 22h of the ninth embodiment is a two-trapezoidal cylindrical combined structure, the grating unit 221h is perpendicular to the xy plane, and the grating unit 221h is two connected trapezoids on the lateral surface parallel to the xy plane; and the grating unit 221i of the grating structure 22i of the tenth embodiment is a two-triangular cylindrical combined structure, the grating unit 221i is perpendicular to the xy plane, and the grating unit 221i is two spaced triangles on the lateral surface parallel to the xy plane. The grating structures provided by the fourth embodiment to the tenth embodiment of the present application can all achieve orthogonal pupil expansion of ±90° to form a 180° pupil expansion area, so as to increase the effective coupling-out grating area of the grating structure, increase the effective display area of the grating structure, improve the grating utilization rate, and also reduce unnecessary coupling-out, thereby improving the overall efficiency of the diffractive waveguide device.

[0085] In other embodiments, the grating unit can also be one or a combination of a conical structure, a pyramidal structure, a frustum-like structure, and a circular truncated cone structure.

[0086] In other embodiments, the grating unit can also be an irregular shape or a combination of irregular shapes; therefore, the shape of the grating unit can be designed according to the required diffraction energy distribution.

[0087] Please refer to Figure 24 ,Figure 24 FIG. 11 is a schematic view of a grating structure 22j according to an eleventh embodiment of the present disclosure. The grating structure 22j according to the eleventh embodiment of the present disclosure is similar to the grating structure 22 according to the first embodiment, except that the grating units 221j are arranged in a rectangular region, and the duty cycle of each grating unit 221j is adjusted on the two sides of a center line o of the rectangular region parallel to the first direction (along the x-axis direction) as the symmetry axis, so as to modulate the diffraction efficiency of the grating units 221j. In this embodiment, the duty cycle of the grating units 221j is modulated in the second direction (along the y-axis direction). Specifically, the radial dimension of the grating units 221j gradually increases from the center line o along the second direction, i.e., the radial dimension of the grating units 221j on the horizontal cross section parallel to the xy plane gradually increases from the center line o along the second direction. For example, if the grating units 221j are in a cylindrical structure, the diameter of the grating units 221j gradually increases from the center line o to the side away from the center line o. If the grating units 221j are in a square column structure or a rectangular column structure, the size of the grating units 221j on the horizontal cross section parallel to the xy plane gradually increases from the center line o to the side away from the center line o. In the grating structure 22j according to this embodiment, the duty cycle is modulated on the two sides of the center line o parallel to the first direction as the symmetry axis, so that the diffraction efficiency of the edge of the grating structure 22j is improved, thereby ensuring the uniformity of the up and down emission intensities.

[0088] In other embodiments, the grating units 221j are arranged in a rectangular region, and the radial dimension of the grating units 221j can also gradually decrease from the center line o along the second direction (along the y-axis direction) as the symmetry axis, i.e., the radial dimension of the grating units 221j on the horizontal cross section parallel to the xy plane gradually decreases from the center line o along the second direction. For example, if the grating units are in a cylindrical structure, the diameter of the grating units gradually decreases from the center line o to the side away from the center line o. If the grating units are in a square column structure or a rectangular column structure, the size of the grating units on the horizontal cross section parallel to the xy plane gradually decreases from the center line o to the side away from the center line o.

[0089] In other embodiments, the grating units are arranged in a rectangular region, and the duty cycles of the grating units are adjusted on both sides of a center line of the rectangular region parallel to the second direction (along the y-axis direction) as the symmetry axis, that is, the duty cycles of the grating units are modulated in the first direction (along the x-axis direction) to improve the diffraction efficiency of the grating units and ensure the uniformity of the up and down emission intensities. Specifically, the radial dimensions of the grating units gradually increase from the center line in the first direction, that is, the radial dimensions of the grating units on the horizontal wearing surface parallel to the xy plane gradually increase from the center line in the first direction. For example, if the grating units are cylindrical structures, the diameters of the grating units gradually increase from the center line to the side away from the center line; if the grating units are square column structures or rectangular column structures, the sizes of the grating units on the horizontal wearing surface parallel to the xy plane gradually increase from the center line to the side away from the center line.

[0090] In other embodiments, the grating units are arranged in a rectangular region, and the duty cycles of the grating units are adjusted on both sides of a center line of the rectangular region parallel to the second direction (along the y-axis direction) as the symmetry axis to improve the diffraction efficiency of the grating units and ensure the uniformity of the up and down emission intensities; the radial dimensions of the grating units gradually decrease from the center line in the first direction (along the x-axis direction), that is, the radial dimensions of the grating units on the horizontal wearing surface parallel to the xy plane gradually decrease from the center line in the first direction. For example, if the grating units are cylindrical structures, the diameters of the grating units gradually decrease from the center line to the side away from the center line; if the grating units are square column structures or rectangular column structures, the sizes of the grating units on the horizontal wearing surface parallel to the xy plane gradually decrease from the center line to the side away from the center line.

[0091] Please refer to Figure 25 , Figure 25FIG. 12 is a schematic view of a grating structure 22k according to a twelfth embodiment of the present application. The grating structure 22k according to the twelfth embodiment of the present application is similar to the grating structure 22j according to the eleventh embodiment of the present application, except that the radial dimension of the grating units 221k gradually increases along the first direction (along the x-axis direction) and gradually increases from the center line o along the second direction (along the y-axis direction), i.e., the radial dimension of the grating units 221k gradually increases along the first direction and the radial dimension of the grating units 221k gradually increases from the center line o along the second direction, so that the radial dimension of the grating units 221k on the horizontal cross-sectional surface parallel to the xy plane gradually increases along the first direction and gradually increases from the center line o to the side away from the center line o. The grating structure 22k in this embodiment is modulated in the first direction and the second direction at the same time to improve the uniformity in the two directions, so that the diffraction efficiency of the edge of the grating structure 22k is improved to ensure the uniformity of the up and down emission intensities.

[0092] In other embodiments, the grating units are arranged in a rectangular region, and the duty cycle of each grating unit is adjusted on the two sides of the center line of the rectangular region parallel to the first direction (along the x-axis direction) as the symmetry axis to improve the diffraction efficiency of the grating units to ensure the uniformity of the up and down emission intensities. Specifically, the radial dimension of the grating units gradually decreases along the first direction and gradually decreases from the center line along the second direction (along the y-axis direction), i.e., the radial dimension of the grating units gradually decreases along the first direction and the radial dimension of the grating units gradually decreases from the center line along the second direction, so that the radial dimension of the grating units on the horizontal cross-sectional surface parallel to the xy plane gradually decreases along the first direction and gradually decreases from the center line to the side away from the center line. The grating structure in this embodiment is modulated in the first direction and the second direction at the same time to improve the uniformity in the two directions, so that the diffraction efficiency of the grating structure is improved to ensure the uniformity of the up and down emission intensities.

[0093] Please refer to Figure 26 , Figure 26is a schematic diagram of the grating structure 22n provided by the thirteenth embodiment of the present application; the grating structure 22n provided by the thirteenth embodiment of the present application is similar to the grating structure 22 of the first embodiment in structure, except that the height dimension of the grating unit 221n of the grating structure 22n can be modulated. Specifically, a plurality of grating units are arranged into a rectangular region, and the height dimension of each grating unit 221n is adjusted on the two sides opposite to each other with the center line o of the rectangular region parallel to the first direction (along the x-axis direction) as the axis of symmetry, i.e., the extension length of each grating unit 221n along the Z direction is adjusted. In this embodiment, the height dimension of a plurality of grating units 221n gradually decreases from the center line o along the second direction (along the y-axis direction) towards the two opposite sides. The grating unit 221n in this embodiment adjusts the depth along the second direction towards the two opposite sides with the center line of the grating structure as the axis of symmetry, which can also modulate the diffraction efficiency of the grating structure 22n and improve the uniformity.

[0094] In another embodiment, a plurality of grating units are arranged into a rectangular region, and the height dimension of a plurality of grating units gradually increases from the center line o along the second direction (along the y-axis direction) towards the two opposite sides with the center line of the rectangular region parallel to the first direction (along the x-axis direction) as the axis of symmetry, which can also modulate the diffraction efficiency of the grating structure and improve the uniformity.

[0095] Please refer to Figure 27 , Figure 27FIG. 14 is a schematic view of the grating structure 22m according to the fourteenth embodiment of the present application. The grating structure 22m according to the fourteenth embodiment of the present application is similar to the grating structure 22 according to the first embodiment, except that the surface of the waveguide substrate 21a is a stepped surface, i.e., the first surface 211a of the waveguide substrate 21a is a stepped surface, which includes a first stepped surface 2112 located in the middle and two second stepped surfaces 2114 located on opposite sides of the first stepped surface 2112, and the first stepped surface 2112 is parallel to the second stepped surfaces 2114. A plurality of grating units are arranged on the first stepped surface 2112 and the two second stepped surfaces 2114, and the end surfaces of the grating units away from the surface are coplanar. Specifically, the first stepped surface 2112 protrudes out of the second stepped surfaces 2114 along the Z-axis direction, and a plurality of first grating units 2212 are arranged on the first stepped surface 2112, a plurality of second grating units 2214 are arranged on each second stepped surface 2114, the height of the first grating units 2212 is less than the height of the second grating units 2214, i.e., the length of the first grating units 2212 extending along the Z-axis is less than the length of the second grating units 2214 extending along the Z-axis. Preferably, the end surfaces of the grating units away from the first surface 211a are coplanar, i.e., the end surfaces of the first grating units 2212 away from the first stepped surface 2112 are coplanar with the end surfaces of the second grating units 2214 away from the second stepped surfaces 2114. The grating structure 22m according to the present embodiment modulates in the first direction and the second direction at the same time, so as to improve the uniformity in the two directions, increase the diffraction efficiency of the grating structure, and ensure the uniformity of the up and down emission intensities.

[0096] Further, the stepped surface further includes two third stepped surfaces 2116 parallel to the first stepped surface 2112, and the two third stepped surfaces 2116 are located on the sides of the two second stepped surfaces 2114 away from the first stepped surface 2112, and each second stepped surface 2114 protrudes out of the third stepped surface 2116 along the Z-axis direction. A plurality of third grating units 2216 are arranged on each third stepped surface 2116, and the height of the third grating units 2216 is greater than the height of the second grating units 2214, i.e., the length of the third grating units 2216 extending along the Z-axis is greater than the length of the second grating units 2214 extending along the Z-axis. Preferably, the end surfaces of the first grating units 2212 away from the first stepped surface 2112, the end surfaces of the second grating units 2214 away from the second stepped surfaces 2114, and the end surfaces of the third grating units 2216 away from the third stepped surfaces 2116 are coplanar.

[0097] Please refer to Figure 28 , Figure 28FIG. 15 is a schematic view of the in-coupling grating 225 and the out-coupling grating 222 of the diffractive waveguide device provided by the fifteenth embodiment of the present application; the diffractive waveguide device provided by the fifteenth embodiment of the present application is similar in structure to the diffractive waveguide device of the first embodiment, except that the grating structure in the fifteenth embodiment also includes the out-coupling grating 222 and the in-coupling grating 225 disposed on the waveguide substrate, the in-coupling grating 225 is located directly above the out-coupling grating 222 (i.e., top projection mode), that is, the projection of the in-coupling grating 225 along the first direction is located within the area of the out-coupling grating 222; in the present embodiment, the first direction refers to the y-axis direction. Specifically, the structure and positional relationship of the in-coupling grating 225 and the out-coupling grating 222 on the diffractive waveguide device in the fifteenth embodiment are that the in-coupling grating 225 and the out-coupling grating 222 in the first embodiment are all rotated clockwise by 90°, so that the in-coupling grating is directly above the out-coupling grating 222. In the present embodiment, the included angle θ of the base vector of the out-coupling grating 222 is 90° or 80°≤θ≤100°; the period (i.e., the mode length) of the first base vector is equal to the period (i.e., the mode length) of the second base vector or the period (i.e., the mode length) of the first base vector is equal to N times the period (i.e., the mode length) of the second base vector, wherein the range of N is: 0.5≤N≤2.

[0098] Please refer to Figure 29 and Figure 30 , Figure 29 is Figure 1 the ray propagation schematic view of the top projection mode of the two-dimensional out-coupling grating in Figure 30 is the ray propagation schematic view of the top projection mode of the out-coupling grating 222 in Figure 28 For the top projection mode of the hexagonal lattice in the prior art, there are three diffractive orders that can affect the human eye vision, as shown in Figure 29 , which are (1, 1) order diffraction, (1, 0) order diffraction and (0, 1) order diffraction. For the top projection mode of the rectangular lattice in Figure 28 , there can be five diffractive orders that can affect the human eye vision, as shown in Figure 30 , which are (1, 0) order diffraction, (1, -1) order diffraction, (1, 1) order diffraction, (0, 1) order diffraction and (0, 1) order diffraction. Figure 29 and Figure 30 The solid lines in and

[0099] represent the wave vectors that can form diffraction fringes in the field of view, and the dashed lines represent the wave vectors that cannot form rainbow fringes in the field of view. Figure 31 and Figure 32 , Figure 31 is Figure 29 the rainbow fringe simulation schematic view of the (1, 1) order diffraction of the two-dimensional out-coupling grating in

[0100] Figure 32 isFigure 30 A schematic diagram simulating the rainbow pattern of the (1,0)th order diffraction of the coupling grating; from Figure 31 and Figure 32 It is known that, in order to match the wave vector of the coupled grating, the rainbow pattern simulation diagram of the (1,1)th order diffraction of the top projection mode of the coupled grating (i.e., the hexagonal lattice) in the prior art is consistent in direction and the same in size as the rainbow pattern simulation diagram of the (1,0)th order diffraction of the top projection mode of the coupled grating (i.e., the rectangular lattice) in this application, meaning that the rainbow patterns formed by the two are completely identical. Therefore, the coupled grating of this application cannot reduce the rainbow pattern effect in the top part of the area.

[0101] Please refer to the following: Figure 33 and Figure 34 , Figure 33 yes Figure 29 A schematic diagram simulating the rainbow pattern of (1,0) order diffraction and (0,1) order diffraction of a two-dimensional coupling grating; Figure 34 yes Figure 30 A schematic diagram simulating the rainbow pattern of (1, -1)-order and (1, 1)-order diffraction of the coupling grating. From Figure 29 and Figure 33 It can be seen that the top projection modes of the existing coupling grating (i.e., hexagonal lattice) also include (1, 0) order diffraction and (0, 1) order diffraction; from Figure 30 and Figure 34 It can be seen that the top projection modes of the coupling grating (i.e., rectangular lattice) in this application have two orders of diffraction: (1, -1) order and (1, 1) order, which are approximately the same in angle. Specifically, in the top projection mode of the coupling grating in this application, the direction of the wave vector of the square, rectangular, or rhomboid lattice is determined by the period and angle in the 45° left and right directions. However, generally around 45°, the magnitude of the diffraction wave vector is the superposition of the kx and ky directions. Because the angle between kx and ky is around 90°, the diffraction wave vector is longer than that of the diffraction wave vector of the coupling grating (i.e., hexagonal lattice) in the prior art, causing the final diffraction fringes to be far from the field of view (e.g., ...). Figure 34 (As shown). Based on this mechanism, the top projection mode of the coupled grating in this application can effectively reduce the rainbow effect caused by the upper right or upper left light source.

[0102] Unlike the top projection mode of the coupling grating (i.e., hexagonal grid) in the prior art, the top projection mode of the coupling grating (i.e., rectangular grid) in this application will have additional (0, 1) order diffraction and (0, -1) order diffraction. These two orders of diffraction will form diffraction fringes for the light source to the left or right front horizontally.

[0103] In summary, compared with the top projection mode of the coupling-out grating (i.e. hexagonal lattice) in the prior art, the top projection mode of the coupling-out grating (i.e. rectangular lattice) of the present application has no improvement on the rainbow stripe formed by the light source in the part of the area directly above, has obvious improvement effect on the rainbow stripe of the light source in the upper left and upper right, but may bring rainbow stripe of the light source in the front left or front right, but the daily light source often appears in the directly above or left and right upper area, so compared with the coupling-out grating (i.e. hexagonal lattice) in the prior art, the rainbow stripe of the top projection mode of the coupling-out grating (i.e. rectangular lattice) of the present application has greater improvement.

[0104] Please refer to Figure 35 , Figure 35 is a schematic diagram of the coupling-in grating and the coupling-out grating of the diffractive waveguide device provided by the sixteenth embodiment of the present application; the diffractive waveguide device provided by the sixteenth embodiment of the present application is similar in structure to the diffractive waveguide device of the fifteenth embodiment, the difference is that the coupling-in grating 225 is located on one side of the coupling-out grating 222 (i.e. side projection mode), that is, the projection of the coupling-in grating 225 along the second direction is located in the area of the coupling-out grating 222; the second direction in the present embodiment refers to the direction along the x-axis. Specifically, the structure and positional relationship of the coupling-in grating 225 and the coupling-out grating 222 on the diffractive waveguide device in the sixteenth embodiment is that the coupling-in grating 225 and the coupling-out grating in the fifteenth embodiment are all rotated counterclockwise by 90°, so that the coupling-in grating is on the side of the coupling-out grating. The included angle θ of the base vector of the coupling-out grating 222 in the present embodiment is 90° or 80°≤θ≤100°; the period (i.e. mode length) of the first base vector is equal to the period (i.e. mode length) of the second base vector or the period (i.e. mode length) of the first base vector is equal to N times the period (i.e. mode length) of the second base vector, the range of N is: 0.5≤N≤2.

[0105] The effect of the coupling-in grating 225 in the present embodiment on the rainbow stripe located on the side of the coupling-out grating 222 is the same as the effect of the coupling-in grating 225 in the fifteenth embodiment on the rainbow stripe located directly above the coupling-out grating 222. The analysis of the rainbow stripe of the coupling-out grating (i.e. rectangular lattice) of the present application is related to the period ratio, if the vertical direction (y-axis direction) period is smaller than the horizontal direction (x-axis direction) period, the rainbow stripe in the vertical direction will move away from the field of view, otherwise, the rainbow stripe will move to the center of the field of view. For the rhombic lattice, the effect is similar, in addition, the rainbow stripe will slightly deviate to the left or right, but no matter which lattice, the rainbow stripe brought by the light source in the upper left and upper right is relieved, the principle is described in the fifteenth embodiment.

[0106] Please refer to Figure 36 , Figure 36Figure 17 is a structural schematic diagram of a diffractive waveguide device provided by the seventeenth embodiment of the present application; the diffractive waveguide device provided by the seventeenth embodiment of the present application is similar in structure to the diffractive waveguide device of the first embodiment, except that in the seventeenth embodiment, a first receiving groove and a second receiving groove are provided on the first surface 211 of the waveguide substrate 21, the first receiving groove is spaced from the second receiving groove, the in-coupling grating 225 is provided in the first receiving groove, and the out-coupling grating 222 is provided in the second receiving groove. The included angle θ of the base vectors of the out-coupling grating 222 is 90° or 80°≤θ≤100°; the size of the period (i.e. the mode length) of the first base vector is equal to the size of the period (i.e. the mode length) of the second base vector or the size of the period (i.e. the mode length) of the first base vector is equal to N times the size of the period (i.e. the mode length) of the second base vector, and the range of N is: 0.5≤N≤2; in this embodiment, the included angle θ of the base vectors of the out-coupling grating 222 is 90°, the absolute value of the first period (i.e. the first mode length) is equal to N times the absolute value of the second period (i.e. the first mode length), i.e. the range of N is: 0.5≤|N|≤2, and the out-coupling grating region of the out-coupling grating 222 is rectangular, so that the two-dimensional pupil expanding angle of the out-coupling grating 222 is 180°.

[0107] Referring to Figure 37 , Figure 37 Figure 18 is a structural schematic diagram of a diffractive waveguide device provided by the eighteenth embodiment of the present application; the diffractive waveguide device provided by the eighteenth embodiment of the present application is similar in structure to the diffractive waveguide device of the first embodiment, except that in the eighteenth embodiment, the in-coupling grating 225 and the out-coupling grating 222 are both provided on the second surface 213. The included angle θ of the base vectors of the out-coupling grating 222 is 90° or 80°≤θ≤100°; the size of the period (i.e. the first mode length) of the first base vector is equal to the size of the period (i.e. the first mode length) of the second base vector or the size of the period (i.e. the first mode length) of the first base vector is equal to N times the size of the period (i.e. the second mode length) of the second base vector, and the range of N is: 0.5≤N≤2; in this embodiment, the included angle between the first direction and the second direction of the grating unit of the out-coupling grating 222 is 90°, and the absolute value of the first period (i.e. the first mode length) is equal to the absolute value of the second period (i.e. the second mode length), i.e. the range of N is: 0.5≤|N|≤2, and the out-coupling grating region of the out-coupling grating 222 is rectangular, so that the two-dimensional pupil expanding angle of the out-coupling grating 222 is 180°.

[0108] Referring to Figure 38 , Figure 38This is a schematic diagram of the structure of the diffraction waveguide device provided in the nineteenth embodiment of this application. The diffraction waveguide device provided in the nineteenth embodiment of this application is similar in structure to the diffraction waveguide device in the first embodiment, except that: the coupling grating 225 and the coupling grating 222 are respectively disposed on the first surface 211 and the second surface 213. In this embodiment, the coupling grating 225 is disposed on the first surface 211 and the coupling grating 222 is disposed on the second surface 213. The included angle θ of the basis vectors of the coupling grating 222 is 90° or 80°≤θ≤100°; the period (i.e., the first mode length) of the first basis vector is equal to the period (i.e., the second mode length) of the second basis vector, or the period (i.e., the first mode length) of the first basis vector is equal to N times the period (i.e., the second mode length) of the second basis vector, where N is in the range of 0.5≤N≤2; in this embodiment, the included angle θ between the first direction and the second direction of the grating unit of the coupling grating 222 is 80°≤θ≤100°, and the absolute value of the first period (i.e., the first mode length) is equal to N times the absolute value of the second period (i.e., the second mode length), where N is in the range of 0.5≤|N|≤2; the coupling grating region of the coupling grating 222 is rectangular, such that the two-dimensional pupil angle of the coupling grating 222 is 180°.

[0109] Please see Figure 39 , Figure 39 This is a schematic diagram of the structure of the diffraction waveguide device provided in the twentieth embodiment of this application. The diffraction waveguide device provided in the twentieth embodiment of this application has a similar structure to the diffraction waveguide device in the nineteenth embodiment, except that the coupling grating 225 is disposed on the second surface 213 and the coupling grating 222 is disposed on the first surface 211.

[0110] Please see Figure 40 , Figure 40 This is a schematic diagram of the structure of the diffraction waveguide device provided in the twenty-first embodiment of this application. The diffraction waveguide device provided in the twenty-first embodiment of this application is structurally similar to the diffraction waveguide device in the first embodiment, except that the diffraction waveguide device in the twenty-first embodiment further includes a protective sheet 226. The protective sheet 226 covers the surface of the coupling grating 222 facing away from the waveguide substrate 21, and is used to protect the coupling grating 222 from damage. The material of the protective sheet 226 can be, but is not limited to, glass, plastic, etc.

[0111] Please see Figure 41 , Figure 41is a structural schematic diagram of a diffractive waveguide device provided by a twenty-second embodiment of the present application; the diffractive waveguide device provided by the twenty-second embodiment of the present application is similar in structure to the diffractive waveguide device of the nineteenth embodiment, except that the diffractive waveguide device in the twenty-second embodiment further comprises a protective sheet 226, which covers the surface of the out-coupling grating 222 facing away from the waveguide substrate 21, for protecting the grating structure 22 from damage. The protective sheet 226 can be made of, but is not limited to, glass, plastic, etc.

[0112] The out-coupling grating 222 in each embodiment is in an integral structure with the waveguide substrate 21.

[0113] Referring to Figure 42 , Figure 42 is a schematic diagram of a near-eye display device 100 provided by an embodiment of the present application. The near-eye display device 100 comprises a diffractive waveguide device as provided by any of the preceding embodiments.

[0114] In one embodiment, the near-eye display device 100 further comprises a wearing frame 130. The wearing frame 130 has two spaced-apart window regions 131, at least one of the two window regions 131 being provided with a diffractive waveguide device as described above. When one of the two window regions 131 is provided with the diffractive waveguide device, the one window region 131 can allow a human eye to see a virtual image, while the in-coupling grating 225 region itself can be transparent to ambient light, so that the one window region 131 can achieve the effect of augmented reality. When both of the two window regions 131 are provided with the diffractive waveguide device, both of the two window regions 131 can achieve the effect of augmented reality. In the schematic diagram of the present embodiment, both of the two window regions 131 are provided with the grating structure 22, for example, and each in-coupling grating 225 is located on one side of the corresponding out-coupling grating 222; preferably, the in-coupling grating 225 is located in the middle of the corresponding out-coupling grating 222.

[0115] Referring to Figure 43 , Figure 43A schematic diagram of a near-eye display device 100a according to another embodiment of the present application is shown. The near-eye display device 100a includes a wearing frame 130, a wearing bracket 160, an image source 30, and an optical lens assembly 170. The wearing bracket 160 is connected to the wearing frame 130. The image source 30, also referred to as a projection light engine, is disposed on one side of the waveguide substrate 21 and configured to generate light rays according to an image to be displayed. The optical lens assembly 170 is disposed between the image source 30 and the in-coupling grating 225 and configured to project the light rays into the in-coupling grating 225 according to a preset rule. At least one of the image source 30 and the optical lens assembly 170 is disposed at a connection between the wearing frame 130 and the wearing bracket 160. Each in-coupling grating 225 is located on one side of a corresponding out-coupling grating 222, i.e., in a side projection mode. Preferably, the in-coupling grating 225 is located in a middle portion of the side of the corresponding out-coupling grating 222.

[0116] Specifically, the near-eye display device is an AR glass, and the wearing bracket 160 is also referred to as a glass leg.

[0117] When the near-eye display device is an AR glass, in order to make the waveguide substrate structure formed by the waveguide substrate 21, the in-coupling grating 225, and the out-coupling grating 222 as close as possible to the shape of the glass, the in-coupling grating 225 can be disposed close to the connection between the wearing frame 130 and the wearing bracket 160. The image source 30 and the optical lens assembly 170 are placed at the connection between the wearing frame 130 and the wearing bracket 160, and the in-coupling grating 225 is arranged on one side of the viewing window 131. When the near-eye display device has two viewing windows 131, the two in-coupling gratings 225 are respectively located on opposite sides of the two viewing windows 131. When the AR glass is worn, the two in-coupling gratings 225 are distributed on opposite sides of the human eye.

[0118] Referring to Figure 44 , Figure 44 A schematic diagram of a near-eye display device 100b according to another embodiment of the present application is shown. The near-eye display device 100b according to the embodiment has a structure similar to that of the near-eye display device 100 described above, except that the in-coupling grating 225 in each viewing window 131 is located on a top side of the out-coupling grating 222, i.e., the in-coupling grating 225 is arranged in a top projection mode. Preferably, the in-coupling grating 225 is located in a middle portion of the top side of the out-coupling grating 222.

[0119] Referring to Figure 45 , Figure 45is a schematic diagram of a near-eye display device 100c provided by another embodiment of the present application. The near-eye display device 100c of the present embodiment has a structure similar to that of the near-eye display device 100a described above, except that the in-coupling grating 225 in each eyebox 131 is located on the top side of the out-coupling grating 222, i.e., the in-coupling grating 225 is arranged in a top projection mode; preferably, the in-coupling grating 225 is located in the middle of the top side of the out-coupling grating 222.

[0120] Referring to Figure 46 , Figure 46 is a schematic diagram of a near-eye display device 100d provided by another embodiment of the present application. The near-eye display device 100d further includes a camera 40, an environmental sensor 60, a processor 70, and a battery 80. The image source 30, the camera 40, and the environmental sensor 60 are electrically connected to the processor 70 and are configured to work under the control of the processor 70. The camera 40 is configured to collect video data, and the environmental sensor 60 is configured to detect the surrounding environment. The battery 80 is configured to supply power to the image source 30, the camera 40, the environmental sensor 60, and the processor 70.

[0121] Referring to Figure 3 and Figure 47 , Figure 47 is a flowchart of a manufacturing method of a diffractive waveguide device provided by an embodiment of the present application. The manufacturing method includes the following steps:

[0122] S1, providing a waveguide substrate 21;

[0123] S2, forming a grating structure 22 on a surface of the waveguide substrate 21, wherein the grating structure 22 includes a plurality of grating units 221, the plurality of grating units 221 have a first period in a first direction and a second period in a second direction different from the first direction, and the first period and the second period are adjusted so that the two-dimensional pupil expansion angle of the grating structure 22 is 180°

[0124] In the step S2, the grating structure 22 can be formed on the first surface 211 and / or the second surface 213 of the waveguide substrate 21. The grating structure 22 is formed on the surface of the waveguide substrate 21 by using nanoimprinting, lithography, etching, growth, nanoimprinting, casting, molding, or injection molding, etc., so as to realize mass production.

[0125] In the step S2, the grating structure 20 is formed on the surface of the waveguide substrate 21 by a nanoimprint method, including: providing a master, wherein the master has a grating structure to be transferred corresponding to the grating structure 22, wherein the grating structure to be transferred includes grating units arranged along a first period and a second period with a base vector included angle of 90°, wherein the grating units to be transferred are consistent with the grating units in structure shape, arrangement mode, height and width; polymerizing a sub-mold by the master, wherein the sub-mold has a complementary structure complementary to the grating structure to be transferred on the master, and the complementary structure forms a cavity matching the structure shape, arrangement mode, height and width of the grating units; coating the grating substrate material of the uncured grating structure 22 on the surface of the waveguide substrate 21; imprinting the uncured grating substrate material by the sub-mold, so that the uncured grating substrate material fills the cavity of the sub-mold, and curing the grating substrate material to form the grating structure 22 on the surface of the waveguide substrate 21.

[0126] The grating substrate material can be a resin material, such as ultraviolet light curing resin material or heat curing resin material, etc., and the grating substrate material can be cured by ultraviolet light or heating to form the grating structure 22.

[0127] The principles and implementation manners of the present application are described by specific examples in the present application, and the above examples are only used to help understand the core idea of the present application; meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manners and application range can be changed, and the above description should not be understood as the limitation of the present application.

Claims

1. A diffraction waveguide device, characterized in that, The diffraction waveguide device includes: Waveguide substrate, the waveguide substrate including a first surface, the first surface being a stepped surface, the stepped surface including a first step surface located in the middle and two second step surfaces located on opposite sides of the first step surface; and A grating structure is disposed on a first surface of a waveguide substrate. The grating structure includes a plurality of grating units, each grating unit being perpendicular to a first step surface and two second step surfaces of the first surface. The end faces of each grating unit facing away from the first surface are coplanar. The plurality of grating units have a first period in a first direction and a second period in a second direction different from the first direction. By adjusting the first period and the second period, the plurality of grating units are arranged in a rectangle on the first surface at intervals of a first mode length along the first direction and a second mode length along the second direction, such that the two-dimensional pupil angle of the grating structure is 180°. The diffraction waveguide device satisfies the following condition: In the normalized k-space field distribution of the grating structure, the horizontal axis is... The vertical axis is The radii of the concentric inner and outer circles are the refractive index of the environment and the refractive index of the waveguide substrate, respectively. The central field of view is located inside the inner circle. The (0, 0) order diffraction field of view and the (-1, ±1) order diffraction field of view are located in the ring formed by the inner and outer circles. The (0, ±1) order diffraction field of view is located outside the outer circle to avoid (0, ±1) order diffraction. The pupil angle of the central field of view is 180°. Wherein, λ is the wavelength, kx is the x-direction grating vector in reciprocal space, and ky is the y-direction grating vector in reciprocal space.

2. The diffraction waveguide device as described in claim 1, characterized in that, The range of the angle θ between the first direction and the second direction is: 80°≤θ≤100°.

3. The diffraction waveguide device as described in claim 1, characterized in that, The first modulus of the first period is equal to N times the second modulus of the second period, where N is in the range of 0.5 ≤ N ≤ 2.

4. The diffraction waveguide device as described in claim 1, characterized in that, A plurality of grating units are arranged in a rectangular region. With the center line of the rectangular region parallel to the first direction as the axis of symmetry, the duty cycle of each grating unit is adjusted on both sides opposite to the center line to modulate the diffraction efficiency of the plurality of grating units.

5. The diffraction waveguide device as described in claim 4, characterized in that, The radial dimension of some of the grating units gradually increases from the center line along the second direction.

6. The diffraction waveguide device as described in claim 4, characterized in that, The radial dimensions of some of the grating units gradually increase along the first direction and gradually increase from the center line along the second direction.

7. The diffraction waveguide device as described in claim 4, characterized in that, The height of some of the grating units gradually increases or decreases from the center line along the second direction toward opposite sides.

8. The diffraction waveguide device as described in claim 1, characterized in that, The height of the grating unit on the first step surface is less than the height of the grating unit on each of the second step surfaces.

9. The diffraction waveguide device as described in claim 1, characterized in that, The first mode length of the first period is 260 nm to 500 nm; the second mode length of the second period is 260 nm to 500 nm.

10. The diffraction waveguide device according to any one of claims 1-9, characterized in that... The grating structure includes an input grating and an output grating disposed on the waveguide substrate. The input grating is used to couple light into the waveguide substrate. The output grating is composed of a plurality of grating units and is used to receive light after total internal reflection by the waveguide substrate and couple the light out of the waveguide substrate after two-dimensional pupil expansion.

11. The diffraction waveguide device as described in claim 10, characterized in that, The waveguide substrate includes a second surface disposed opposite to the first surface, and the coupling-in grating and the coupling-out grating are both disposed on the first surface or the second surface; or the coupling-in grating and the coupling-out grating are respectively disposed on the first surface and the second surface.

12. The diffraction waveguide device as described in claim 10, characterized in that, The angle between the first direction and the second direction of the grating unit of the coupled grating is 90°. The absolute value of the first mode length of the first period is equal to N times the absolute value of the second mode length of the second period. The range of N is: 0.5≤N≤2. The coupled grating region of the coupled grating is rectangular, so that the two-dimensional pupil angle of the coupled grating is 180°.

13. The diffraction waveguide device as described in claim 10, characterized in that, The angle between the first direction and the second direction of the grating unit of the coupled grating is 90°, and the absolute value of the first mode length of the first period is equal to the absolute value of the second mode length of the second period. The coupled grating region of the coupled grating is rectangular, so that the two-dimensional pupil angle of the coupled grating is 180°.

14. The diffraction waveguide device as described in claim 10, characterized in that, The coupling grating and the waveguide substrate are an integral structure.

15. The diffraction waveguide device as described in claim 10, characterized in that, The projection of the coupled-in grating along the first direction is located within the region of the coupled-out grating; or the projection of the coupled-in grating along the second direction is located within the region of the coupled-out grating.

16. A near-eye display device, comprising the diffractive waveguide device as described in any one of claims 1-15.

17. The near-eye display device as described in claim 16, characterized in that, The near-eye display device includes: The wearing frame has two window areas spaced apart, and at least one of the two window areas is provided with the diffraction waveguide device.

18. The near-eye display device as described in claim 17, characterized in that, The near-eye display device also includes: A wearing frame, wherein the wearing frame is connected to the wearing frame; An image source, disposed on one side of the waveguide substrate, is used to generate light rays according to the image to be displayed; and An optical lens assembly is disposed between the image source and the coupling grating of the diffraction waveguide device, and is used to direct the light into the coupling grating according to a preset rule. At least one of the image source and the optical lens assembly is disposed at the connection point between the wearing frame and the wearing bracket.

19. A method for manufacturing a diffractive waveguide device, the method being used to manufacture the diffractive waveguide device as described in any one of claims 1-15, characterized in that, The manufacturing method includes: S1, providing the waveguide substrate; and S2. A grating structure is formed on one surface of the waveguide substrate, wherein the grating structure includes a plurality of grating units, the plurality of grating units having a first period in a first direction and a second period in a second direction different from the first direction, and by adjusting the values ​​of the first period and the second period, the two-dimensional pupil angle of the grating structure is made to be 180°.

20. The manufacturing method as described in claim 19, characterized in that, In step S2, the grating structure is formed on the surface of the waveguide substrate by selecting one of the following methods: nanoimprinting, casting, molding, and injection molding.

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