Coupling-out diffraction element, diffraction optical waveguide, display module and electronic equipment
By adjusting the center deviation of the diffraction structure of the diffraction unit in the diffraction light waveguide, the efficiency uniformity and appearance consistency of the diffraction light waveguide are achieved, and the problems of low efficiency and color change in the prior art are solved.
Patent Information
- Application Number
- CN202421089369.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-17
- Publication Date
- 2025-01-10
- Estimated Expiration
- 2034-05-17
AI Technical Summary
When diffraction optical waveguides are dilated in two-dimensional pupils, the efficiency and uneven distribution are caused by uneven light energy division and transmission losses. The existing technology can easily lead to appearance color changes during modulation, which affects the user experience.
By periodically arranging the diffraction unit in the coupled diffraction element, adjusting the center of the diffraction structure to deviate from the center of the unit, thereby adjusting the diffraction efficiency, achieving targeted efficiency modulation, avoiding grating height and duty cycle adjustment, and maintaining a consistent appearance.
Improves the efficiency uniformity of the diffraction optical waveguide, optimizes the user experience, and avoids color changes in different modulation areas.
Smart Images
Figure CN222337359U_ABST
Abstract
Description
Technical Field
[0001] The present disclosure generally relates to the field of optical technology. More specifically, the present disclosure relates to an outcoupling diffraction element, a diffraction optical waveguide, a display module, and an electronic device. Background Art
[0002] Optical waveguides are optical components that use total internal reflection to guide light. They are commonly used in fiber-optic communications, optical sensors, and optoelectronic devices. In augmented reality or virtual reality devices, optical waveguides help bend and combine light to direct it toward the user's eyes for viewing.
[0003] Based on the coupling structure of light entering and exiting the waveguide, optical waveguide structures can be generally divided into two types: geometric waveguides and diffractive waveguides. Among them, when diffractive waveguides are used for two-dimensional pupil expansion, because they need to split the light energy into multiple parts and distribute them evenly to each exit pupil position, the energy per unit area is reduced, resulting in lower energy efficiency. In addition, due to the different transmission losses when the light energy reaches different exit pupil positions, the light energy finally distributed to each exit pupil position will be inconsistent, which in turn affects the efficiency uniformity of the diffractive waveguide.
[0004] To address the efficiency uniformity issue of diffraction waveguides, existing techniques typically locally adjust the grating height and duty cycle of the outcoupling diffraction element in the diffraction waveguide to achieve efficiency modulation. However, this outcoupling diffraction element can easily lead to noticeable color variations in the appearance of different modulation areas, impacting the user experience of the diffraction waveguide.
[0005] In view of this, there is an urgent need to provide a solution for coupling out a diffraction element so as to achieve diffraction efficiency modulation without affecting the appearance of the modulation area of the diffraction optical waveguide. Utility Model Content
[0006] In order to at least solve one or more technical problems mentioned above, the present disclosure proposes relevant solutions for coupling out diffraction elements in multiple aspects.
[0007] In a first aspect, the present disclosure provides an outcoupling diffraction element comprising: a plurality of periodically arranged diffraction units; in the plurality of periodically arranged diffraction units, the centers of the diffraction structures within a plurality of the diffraction units deviate from the centers of the diffraction units in which they are located.
[0008] In some embodiments, the outcoupling diffraction element is a two-dimensional grating, and the diffraction structure is a grating structure.
[0009] In some embodiments, the out-coupling diffraction element is used in conjunction with the in-coupling diffraction element, and the center offset of the diffraction structure in multiple diffraction units in the out-coupling diffraction element is negatively correlated with the distance from the corresponding diffraction unit to the in-coupling diffraction element.
[0010] In some embodiments, the outcoupling diffraction element includes several sub-regions, and each sub-region includes a plurality of diffraction units.
[0011] In some embodiments, for the diffraction units in the same sub-region, the distances from the diffraction units to the coupling-in diffraction elements used in conjunction with the coupling-out diffraction elements are within the same distance range.
[0012] In some embodiments, the direction of the line connecting the center points of the plurality of sub-regions matches the propagation direction of the light in the outcoupling diffraction element.
[0013] In some embodiments, for diffraction units in the same sub-region, the center offsets of their diffraction structures are the same.
[0014] In some embodiments, in the out-coupling diffraction element, the center offset of the diffraction structure of the diffraction unit in the sub-region is negatively correlated with the distance from the sub-region to the in-coupling diffraction element used in conjunction with the out-coupling diffraction element.
[0015] In some embodiments, in the diffraction direction of the preset diffraction order of the out-coupling diffraction element, the center offset of the diffraction structure of the diffraction unit in the sub-region gradually decreases, where the preset diffraction order includes: (0, 0), (+1, +1) and / or (+1, -1).
[0016] In some embodiments, the deviation direction of the diffractive structure includes at least one of the following directions: transverse and longitudinal.
[0017] In some embodiments, in the outcoupling diffraction element, the diffraction structures of all diffraction units are offset from the center of the diffraction unit in which they are located.
[0018] In some embodiments, in the out-coupling diffraction element, the deviation directions of the diffraction structures of all the diffraction units include horizontal and vertical directions.
[0019] In some embodiments, in the outcoupling diffraction element, the center offsets of the diffraction structures of all diffraction units are the same.
[0020] In some embodiments, the (0, 0) diffraction order direction of the out-coupling diffraction element and the coupling-in diffraction element used in conjunction therewith forms a preset angle, so that the out-coupling diffraction element forms two asymmetric regions on both sides of the (0, 0) diffraction order direction of the coupling-in diffraction element, and the center offset of the diffraction structure in the horizontal and vertical directions is determined according to the efficiency ratio of the two regions formed by the out-coupling diffraction element.
[0021] In a second aspect, the present disclosure provides a diffraction optical waveguide comprising: at least one substrate, an incoupling diffraction element, and an outcoupling diffraction element as described in any one of the first aspects, wherein the incoupling diffraction element and the outcoupling diffraction element are both disposed on the substrate.
[0022] In a third aspect, the present disclosure provides a display module comprising: the diffractive light waveguide according to the second aspect.
[0023] In a fourth aspect, the present disclosure provides an electronic device including: the display module as described in the third aspect.
[0024] By using the outcoupling diffraction element provided above, the disclosed embodiments adjust the diffraction structure's position away from the center of the periodically arranged diffraction units by selecting some or all of them, thereby adjusting the diffraction efficiency of the diffraction structure. This in turn achieves targeted modulation of the outcoupling diffraction efficiency of the outcoupling diffraction element, thereby improving the efficiency uniformity of the diffraction waveguide in which the outcoupling diffraction element resides. Because the outcoupling diffraction element does not involve adjustment of the grating height and duty cycle, different modulation areas achieving different diffraction efficiency modulations do not produce noticeable color changes in appearance, thus optimizing the user experience. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present disclosure are shown in an illustrative and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:
[0026] Figure 1 An exemplary structural diagram of an outcoupling diffraction element according to an embodiment of the present disclosure is shown;
[0027] Figure 2 An exemplary structural diagram of a diffraction unit according to some embodiments of the present disclosure is shown;
[0028] Figure 3 shows an exemplary structural diagram of a diffraction unit according to some other embodiments of the present disclosure;
[0029] Figure 4 shows an exemplary structural diagram of a diffraction unit according to some other embodiments of the present disclosure;
[0030] Figure 5 An exemplary structural diagram of a portion of an outcoupling diffraction element according to some embodiments of the present disclosure is shown;
[0031] Figure 6 shows an exemplary structural diagram of an outcoupling diffraction element according to some other embodiments of the present disclosure;
[0032] Figure 7a A schematic diagram showing the diffraction orders of an outcoupling diffraction element according to some embodiments of the present disclosure;
[0033] Figure 7b Shown Figure 7a The diffraction efficiency diagram of the two diffraction orders (+1, +1) and (+1, -1) of the out-coupling diffraction element;
[0034] Figure 8 Schematic diagram showing diffraction orders of outcoupling diffraction elements according to other embodiments of the present disclosure;
[0035] Figure 9 An exemplary structural diagram of the outcoupling diffraction element according to some further embodiments of the present disclosure is shown. DETAILED DESCRIPTION
[0036] The following will clearly and completely describe the technical solutions in the embodiments of this disclosure in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of this disclosure, not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this disclosure.
[0037] It should be understood that the terms “include” and “comprising” used in the specification and claims of the present disclosure indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.
[0038] It should also be understood that the terminology used in this disclosure is for the purpose of describing specific embodiments only and is not intended to limit the disclosure. As used in this disclosure and the claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It should be further understood that the term "and / or" as used in this disclosure and the claims refers to any and all possible combinations of one or more of the associated listed items, including and including these combinations.
[0039] As used in this specification and claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.
[0040] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.
[0041] Example application scenarios
[0042] Optical waveguides, due to their thinness and high light penetration, play a crucial role in the application and promotion of consumer AR glasses. In AR glasses, for optical signals to be transmitted without loss or leakage, they must be reflected back and forth within the waveguide without being transmitted, a process known as total internal reflection. With optical waveguides as a transmission channel, the optical engine and imaging system of AR glasses can be moved away from the glasses, to the top or side of the forehead. This significantly reduces the optical system's obstruction to the outside world, thereby improving the wearing experience of AR glasses.
[0043] Based on the coupling structure of light entering and exiting the waveguide, optical waveguide structures can be generally divided into two types: geometric waveguides and diffractive waveguides. Among them, when diffractive waveguides are used for two-dimensional pupil expansion, because they need to split the light energy into multiple parts and distribute them evenly to each exit pupil position, the energy per unit area is reduced, resulting in lower energy efficiency. In addition, due to the different transmission losses when the light energy reaches different exit pupil positions, the light energy finally distributed to each exit pupil position will be inconsistent, which in turn affects the efficiency uniformity of the diffractive waveguide.
[0044] Existing technologies typically locally adjust the grating height and duty cycle of the outcoupling diffraction element in a diffractive waveguide to achieve efficiency modulation, thereby addressing the issue of uniform efficiency within the diffractive waveguide. However, this outcoupling diffraction element can easily lead to noticeable color variations between modulation areas, impacting the user experience of the diffractive waveguide.
[0045] Exemplary application scenarios
[0046] In light of this, the disclosed embodiments provide a solution for an outcoupling diffraction element. This solution adjusts the diffraction efficiency of a periodically arranged diffraction unit by adjusting some or all of the diffraction structures, specifically by shifting the position of the diffraction structure away from the center of the diffraction unit. This allows for targeted modulation of the outcoupling diffraction efficiency of the outcoupling diffraction element. This modulation method produces no noticeable color changes between modulation areas, optimizing the user experience.
[0047] Figure 1 An exemplary structural diagram of the outcoupling diffraction element of the embodiment of the present disclosure is shown in FIG. Figure 1As shown, the outcoupling diffraction element 100 in the embodiment of the present disclosure includes a plurality of diffraction units 110, and the plurality of diffraction units 110 are periodically arranged in the outcoupling diffraction element 100. For example, in the outcoupling diffraction element 100 shown in the embodiment of the present disclosure, the number of the diffraction units 110 can reach more than one million, such as Figure 1 As shown, in these diffraction units 110 , the centers of the diffraction structures 111 in a plurality of diffraction units 110 deviate from the center of the diffraction unit 110 in which they are located.
[0048] Furthermore, the outcoupling diffraction element 100 can be a two-dimensional grating, and the diffraction structure within the diffraction unit is a grating structure. The diffraction principle of a two-dimensional grating is that diffraction occurs when light passes through a grating with a two-dimensional periodic structure. The grating is composed of equally spaced transparent or opaque stripes. A two-dimensional grating can be understood as a grating element with equally spaced transparent or opaque stripes in both the horizontal and vertical directions. When light passes through the two-dimensional grating, diffraction may occur in all directions.
[0049] It should be noted that the horizontal and vertical directions refer to the two relative directions of the grating structure in the two-dimensional grating. In this embodiment, the horizontal direction can also be called the vertical direction, and the vertical direction can also be called the horizontal direction, that is, the horizontal direction can be any one of the two diffraction directions of the two-dimensional grating, and does not specifically refer to a certain direction. The same applies to the vertical direction.
[0050] In diffraction phenomena, a diffraction pattern typically consists of a primary maximum and secondary maximums. The primary maximum refers to the brightest diffraction fringe in the diffraction pattern, while the secondary maximum refers to the darker diffraction fringe in the diffraction pattern. Secondary maximums can be further divided based on the brightness of the diffraction fringe. To facilitate the description of diffraction fringes of varying brightness, they can be distinguished by diffraction order. The primary maximum is defined as order 0, and the secondary maximum orders are defined as ±1, ±2, ±3, and so on, in descending order of brightness.
[0051] The above description is the definition of the diffraction order of a one-dimensional grating. Furthermore, since a two-dimensional grating will produce diffraction in both the horizontal and vertical directions, the diffraction order of the brightest diffraction pattern in the diffraction image can be defined as (0, 0) in combination with the diffraction orders in the horizontal and vertical directions, that is, the diffraction pattern is the main maximum in both the horizontal and vertical directions. By analogy, the following diffraction orders can be defined, including but not limited to: (+1, +1) and (+1, -1). As an example, the (+1, +1) diffraction order represents the +1 diffraction order in the horizontal direction and the +1 diffraction order in the vertical direction, and the (+1, -1) diffraction order represents the +1 diffraction order in the horizontal direction and the -1 diffraction order in the vertical direction.
[0052] Because the diffraction efficiency of the grating structure varies at different locations within the diffraction element, the outcoupling efficiency of the region at that location within the outcoupling diffraction element can be adjusted by adjusting the center position of the grating structure at a specific location, thereby achieving an efficiency modulation effect. For example, the grating structure within the diffraction element in a high-efficiency region of the outcoupling diffraction element can be offset, thereby suppressing the outcoupling efficiency and modulating the overall efficiency of that high-efficiency region to a lower level, thereby equalizing the efficiency of other relatively low-efficiency regions and improving the efficiency uniformity of the diffraction waveguide where the outcoupling diffraction element is located.
[0053] It needs to be further explained that Figure 2 An exemplary structural diagram of a diffraction unit according to some embodiments of the present disclosure is shown. Figure 2 As shown, due to the different periodic parameters, in the outcoupling diffraction element 100, each diffraction unit 110 includes, in addition to a complete diffraction structure 111, a portion 112 of other diffraction structures surrounding the diffraction structure 111. When implementing efficiency modulation, if the diffraction unit 110 includes portions of other diffraction structures, only the center of the complete diffraction structure therein deviates from the center of the diffraction unit in which it is located. Figure 3 FIG. 1 shows an exemplary structural diagram of a diffraction unit in some other embodiments of the present disclosure. When the diffraction unit 110 includes a local portion 112 of other diffraction structures, the adjusted diffraction unit 110 is as follows: Figure 3 As shown, compared with Figure 2 In the diffraction unit shown, the center of the complete diffraction structure 111 deviates from the center of the diffraction unit, and the parts of other diffraction structures are not subjected to the offset processing.
[0054] Furthermore, the embodiment disclosed herein does not have a strict limitation on the deviation direction of the diffraction structure. For the diffraction unit with a center offset, the deviation direction of the diffraction structure includes at least one of the following directions: horizontal and vertical. It is understood that Figure 4 illustrative structural diagrams of diffraction units according to some other embodiments of the present disclosure are shown. Figure 4 As shown, in some embodiments, the diffraction structure can deviate from the center of the diffraction unit in which it is located in both the horizontal and vertical directions.
[0055] For the out-coupling diffraction element, a single deviation direction can simplify the processing process, thereby reducing the processing difficulty and cost. Therefore, in practical applications, a single direction can be preferentially selected as the deviation direction of the diffraction structure in the out-coupling diffraction element.
[0056] In the diffraction unit, the center offset of the diffraction structure determines the efficiency change of the diffraction unit. Therefore, by flexibly configuring the center offset of the diffraction structure in each diffraction unit, the efficiency of the outcoupling diffraction element can be flexibly modulated.
[0057] To address the issue of uniform efficiency, this embodiment takes into account the distribution of transmission loss during light transmission and designs the center offset of the diffraction structure within each diffraction unit in the outcoupling diffraction element. In a diffraction waveguide, the outcoupling diffraction element 100 is typically used in conjunction with the incoupling diffraction element 200. Light enters the diffraction waveguide through the incoupling diffraction element 200, is transmitted to the outcoupling diffraction element 100, and is then coupled out through the outcoupling diffraction element 100. In this process, the closer the position to the incoupling diffraction element is, the lower the transmission loss and the higher the efficiency. Therefore, in this embodiment, the center offset of the diffraction structure within the outcoupling diffraction element is configured based on the distance between the diffraction unit and the incoupling diffraction element.
[0058] Figure 5 An exemplary structural diagram of the outcoupling diffraction element of some embodiments of the present disclosure is shown, as shown in FIG. Figure 5 As shown, in this embodiment, the center offset of the diffraction structure within the multiple diffraction elements in the out-coupling diffraction element is negatively correlated with the distance between the corresponding diffraction element and the in-coupling diffraction element. In other words, for a diffraction element farther from the in-coupling diffraction element, the center offset of its internal diffraction structure is smaller than that of a diffraction element closer to the in-coupling diffraction element.
[0059] For a clearer explanation, the following examples use a first diffraction element closest to the in-coupling diffraction element and a second diffraction element farthest from the in-coupling diffraction element. In this example, the distance between the first diffraction element and the in-coupling diffraction element is the minimum, and the center offset of the diffraction structure within the first diffraction element is the maximum. At this point, the diffraction element's outcoupling efficiency is low, allowing other efficiencies to continue to propagate backward. When the distance between the second diffraction element and the in-coupling diffraction element is the maximum, the center offset of the diffraction structure within the second diffraction element is the minimum. In one embodiment, the minimum offset can be 0, achieving the highest outcoupling efficiency and maximizing the efficiency of the transmission end.
[0060] It should be noted that within a diffraction element, when the center of the diffraction structure coincides with the center of the diffraction element, that is, when the center offset is 0, the diffraction element achieves maximum efficiency. Therefore, in this embodiment, by increasing the center offset corresponding to diffraction elements closer to the in-coupling diffraction element and decreasing the center offset corresponding to diffraction elements farther from the in-coupling diffraction element, the out-coupling efficiency can be increased in areas with higher transmission loss and decreased in areas with lower transmission loss. This allows regions with different transmission losses to be adjusted to a state of uniform overall efficiency through modulation of the out-coupling efficiency. In other words, this embodiment can achieve efficiency adjustment by increasing the out-coupling efficiency in areas with low transmission efficiency, thereby improving the efficiency uniformity of the diffraction waveguide where the out-coupling diffraction element is located.
[0061] It should be further explained that, in practical applications, the size of the area where the outcoupling diffraction element is located is in the cm or mm level, while the size of the diffraction unit is in the nm level. In other words, an outcoupling diffraction element may include more than one million diffraction units. However, for the sake of convenience, Figure 5 Taking a part of an out-coupling diffraction element composed of three complete diffraction structures as an example, the configuration of the center offset is explained. In practical applications, the above-mentioned configuration scheme of the center offset can be applied to out-coupling diffraction elements composed of other numbers of diffraction units.
[0062] The above embodiments describe a method for configuring the center offset of each diffraction element individually. This method can achieve high-precision efficiency modulation. However, due to the complexity of the manufacturing process, the processing cost and difficulty of the outcoupling diffraction elements in this method are relatively high. To address this issue, some embodiments of the present disclosure provide an optical method for configuring the center offset in batches.
[0063] Figure 6 Schematic diagrams of the outcoupling diffraction elements of other embodiments of the present disclosure are shown. Figure 6 As shown, the outcoupling diffraction element is divided into a plurality of sub-regions, the number of which is greater than or equal to 3, wherein each sub-region includes a plurality of diffraction units. It should be noted that in actual applications, the size of the region where the outcoupling diffraction element is located is on the order of cm or mm, the size of the divided sub-regions is also on the order of cm or mm, and the size of the diffraction units is on the order of nm. Therefore, the sub-regions in this embodiment include at least one million diffraction units.
[0064] exist Figure 6 In the illustrated out-coupling diffraction element, the sub-regions are divided based on their distance from the in-coupling diffraction element. This distance refers to the distance from the center of the sub-region to the in-coupling diffraction element, and is used to set the center offset of the diffraction structure within the sub-region. Because a sub-region is composed of multiple diffraction elements, the addition or deletion of diffraction elements affects the shape and position of the sub-region, thereby affecting the center of the sub-region and, consequently, the distance from the center of the sub-region to the in-coupling diffraction element. As an example, the sub-regions can be divided based on the distance from the diffraction element to the in-coupling diffraction element. For example, for diffraction elements within the same sub-region, their distances to the in-coupling diffraction element used in conjunction with the out-coupling diffraction element are within the same distance range.
[0065] It should be further explained that in the outcoupling diffraction element of this embodiment, the direction of the line connecting the center points of the subregions matches the propagation direction of light in the outcoupling diffraction element. For example, the connecting direction is consistent with the propagation direction of the light. In some embodiments, the subregions of the outcoupling diffraction element are divided according to the propagation direction of light in the outcoupling diffraction element, and the partition boundaries do not need to be strictly limited. For example, if light in the outcoupling diffraction element propagates forward in a fishbone pattern, the outcoupling diffraction element is also divided in a fishbone pattern.
[0066] As an example, in an outcoupling diffraction element of this embodiment, Figure 6 The diffraction units marked with ④ are located in the same sub-area, and the distances from the diffraction units marked with ④ to the coupling diffraction element are all within the distance range of (0, a). Figure 6 The diffraction units labeled ③ are located in the same sub-area, and the distances from the diffraction units labeled ③ to the coupled diffraction elements are all within the distance range of (a, b). Figure 6 The diffraction units labeled ② are located in the same sub-area, and the distances from the diffraction units labeled ② to the coupled diffraction elements are all within the distance range of (b, c). Figure 6 The diffraction units marked with ① are located in the same sub-area, and the distances from the diffraction units marked with ① to the coupling diffraction elements are all within the distance range of (c, d), where 0 <a<b<c<d。
[0067] After the out-coupling diffraction element is divided into several sub-areas according to the distance between the diffraction unit and the in-coupling diffraction element, the configuration accuracy of the center offset can be adjusted from a single diffraction unit to a sub-area. For the diffraction units in the same sub-area, the center offset of their diffraction structures is the same, thereby reducing the processing difficulty, processing time and processing cost of the out-coupling diffraction element.
[0068] Combined with Figure 5 Similar to the configuration described above, in the out-coupling diffraction element of this embodiment, the center offset of the diffraction structure of the diffraction unit in the sub-region is negatively correlated with the distance from the sub-region to the in-coupling diffraction element.
[0069] Taking the outcoupling diffraction element shown in the previous embodiment as an example, the center offsets of the diffraction structures in the diffraction elements labeled ④, ③, ②, and ① are gradually reduced. Since the transmission loss in the diffraction elements labeled ④, ③, ②, and ① gradually increases, configuring the center offsets in the above manner allows the lower center offsets to compensate for the higher transmission loss, thereby reducing the efficiency differences between different regions of the outcoupling diffraction element.
[0070] Furthermore, in a diffraction waveguide, a two-dimensional grating often uses two diffraction orders (+1, +1) and (+1, -1). Figure 7a Schematic diagram showing the diffraction orders of the outcoupling diffraction element of some embodiments of the present disclosure, Figure 7b Shown Figure 7a The diffraction efficiency diagram of the two diffraction orders (+1, +1) and (+1, -1) of the out-coupling diffraction element. Figure 7a and Figure 7b As shown, when the center line of the coupling-in diffraction element coincides with the center line of the coupling-out diffraction element, it can be seen from the diffraction efficiency diagram that the efficiencies of the two diffraction orders (+1, +1) and (+1, -1) remain consistent.
[0071] against Figure 7a In the case shown, some embodiments of the present disclosure set one or more of (0, 0), (+1, +1), and (+1, -1) as preset diffraction orders. In the diffraction directions of these preset diffraction orders, if the number of sub-regions of the outcoupling diffraction element is greater than or equal to 2, the center offsets corresponding to these sub-regions gradually decrease, where the center offsets corresponding to the sub-regions refer to the center offsets of the diffraction structures of all diffraction units within the sub-region. Furthermore, the center offsets of the diffraction structures of the diffraction units within the same sub-region are the same.
[0072] In addition, the diffraction structure's deviation direction includes at least one of the following directions: horizontal and vertical. Furthermore, the diffraction structures of the diffraction elements within the same sub-region may have the same or different deviation directions, without further limitation. Considering manufacturing difficulty and cost, the diffraction structures of the diffraction elements within the same sub-region preferably have the same deviation direction.
[0073] Combined with the previous article Figure 2 Similar to the described embodiment, a single diffraction unit may also include a part of the diffraction structure. In this case, during efficiency modulation, only the center offset processing is performed on the complete diffraction structure.
[0074] As an example, this embodiment assumes that the structural parameters of the two-dimensional grating are as follows:
[0075] Grating period: horizontal period Px = 358nm, vertical period Py = 620nm;
[0076] Grating height: 128nm;
[0077] Horizontal fill factor xFillFactor = 40%;
[0078] Vertical fill factor yFillFactor = 40%;
[0079] The lateral center offset base X1 = Px / 2.0 × xFillFactor = 71.6 nm;
[0080] The longitudinal center offset base Y1 = Py / 2.0 × yFillFactor = 124 nm.
[0081] exist Figure 7a In the case shown, the center line of the coupling diffraction element coincides with the center line of the coupling diffraction element, and the efficiency of the two diffraction orders (+1, +1) and (+1, -1) remains consistent. Therefore, with the diffraction direction of the diffraction order (0, 0) as the boundary, the center offset of the diffraction structure in the diffraction units on both sides can be set symmetrically. Figure 6 Taking the outcoupling diffraction element shown as an example, the center offset of the diffraction structure in the diffraction unit labeled ④ can be calculated by multiplying the center offset base by a multiple of 1.5, the center offset of the diffraction structure in the diffraction unit labeled ③ can be calculated by multiplying the center offset base by a multiple of 1, the center offset of the diffraction structure in the diffraction unit labeled ② can be calculated by multiplying the center offset base by a multiple of 0.5, and the center offset of the diffraction structure in the diffraction unit labeled ① can be calculated by multiplying the center offset base by a multiple of 0, that is, the diffraction structure in the diffraction unit labeled ① is not offset. In actual application, the size of the center offset can be adjusted by controlling the multiple used when calculating the center offset. For the diffraction units labeled ④ to ① above, gradually reducing the multiple can configure a gradually decreasing center offset.
[0082] It should be noted that the specific values for the multipliers mentioned above are merely examples in this embodiment. In actual applications, different multipliers can be set based on actual conditions, and no excessive restrictions are imposed herein. Furthermore, the center offset base used in the above calculations can be either or both of a horizontal center offset base and a vertical center offset base, thereby respectively calculating the horizontal and / or vertical center offsets of the diffractive structure within the diffractive element.
[0083] Figure 8 Schematic diagrams of diffraction orders of outcoupling diffraction elements of other embodiments of the present disclosure are shown. Figure 8 As shown in Figure 1, when the center line of the coupling-in diffraction element does not coincide with the center line of the coupling-out diffraction element, the transmission of the diffraction order will also change. Figure 8 Taking the case shown as an example, the out-coupling diffraction element is divided by the light transmission direction of the diffraction order (0, 0) of the in-coupling diffraction element, forming an upper half with stronger light intensity and energy and a lower half with weaker light intensity and energy.
[0084] The following is for Figure 8 The following describes the situation shown. Figure 8In the situation shown, the center line of the coupling-in diffraction element does not coincide with the center line of the coupling-out diffraction element, that is, the (0, 0) diffraction order direction of the coupling-out diffraction element and the coupling-in diffraction element used in conjunction with it form a preset angle. At this time, the coupling-out diffraction element forms two asymmetric regions on both sides of the (0, 0) diffraction order direction of the coupling-in diffraction element, and the light intensity energy of these two regions is different.
[0085] Figure 9 : shows an exemplary structural diagram of the outcoupling diffraction element of some other embodiments of the present disclosure, such as Figure 9 As shown, in order to adjust the efficiency uniformity, in the out-coupling diffraction element, the diffraction structures of all diffraction units deviate from the center of the diffraction unit in which they are located, and the deviation directions of the diffraction structures of all diffraction units include horizontal and vertical directions, wherein the center offset of the diffraction structure in the horizontal and vertical directions is determined according to the efficiency ratio of the two areas formed by the out-coupling diffraction element.
[0086] Furthermore, in order to simplify the processing difficulty, Figure 9 In the outcoupling diffraction element shown, the center offset of the diffraction structures of all diffraction units is the same.
[0087] As an example, let's assume that the structural parameters of the two-dimensional grating are as follows:
[0088] Grating period: horizontal period Px = 358nm, vertical period Py = 620nm;
[0089] Grating height: 128nm;
[0090] Horizontal fill factor xFillFactor = 40%;
[0091] Vertical fill factor yFillFactor = 40%;
[0092] The lateral center offset base X1 = Px / 2.0 × xFillFactor = 71.6 nm;
[0093] The longitudinal center offset base Y1 = Py / 2.0 × yFillFactor = 124 nm.
[0094] against Figure 8 In the case shown, the diffraction structure in each diffraction unit is shifted in both the horizontal and vertical directions, wherein the horizontal center shift is 1.5*X1=107.4 nm, and the vertical center shift is 1.5*Y1=186 nm. Figure 9 The diffraction efficiencies of the (+1, +1) and (+1, -1) diffraction orders of the outcoupling diffraction element are inconsistent. Specifically, the diffraction efficiency of (+1, +1) is low, while the diffraction efficiency of (+1, -1) is high. Therefore, Figure 9 The outcoupling diffraction element can just be Figure 8 The transmission efficiency of the two systems complements each other to achieve the regulation of efficiency uniformity.
[0095] It should be noted that the calculation of the horizontal center offset and the vertical center offset is only an example given in this embodiment, and its specific value can be adjusted according to actual conditions, and no excessive restrictions are imposed here. Figure 7a Similar to the described embodiment, in actual application, the size of the center offset can also be adjusted by controlling the multiple used when calculating the center offset. The same multiple or different multiples can be used when calculating the horizontal center offset and the vertical center offset. The specific value is determined according to the efficiency ratio of the two areas formed by the out-coupling diffraction element, and no excessive restrictions are imposed here.
[0096] Any outcoupling diffraction element described in the foregoing embodiments can be processed using an electron beam etching method. Its specific processing flow is as follows: prepare a substrate and perform preliminary processing on the substrate, wherein the preliminary processing may include cleaning and modification, etc. After the preliminary processing is completed, a layer of photoresist is evenly coated on the substrate, and then an electron beam lithography machine is used to etch it. After etching, it is subjected to a development process, and finally the required grating structure is obtained to obtain the required outcoupling diffraction element. After etching is completed, the residual photoresist can be removed by using a solvent. The solvent used can be corresponding to the type of photoresist used in the previous process. As an example, when using a photoresist of ZEP520 model during electron beam etching, it is possible to consider adopting NMP (N-Methylpyrrolidone) as a degumming solvent.
[0097] In addition, the outcoupling diffraction element described in the above embodiment may also be prepared by using processing techniques such as ultraviolet lithography or nanoimprinting, and no excessive restrictions are imposed here.
[0098] In summary, the disclosed embodiments provide an outcoupling diffraction element that, by selecting some or all of a periodically arranged plurality of diffraction units and adjusting the position of the diffraction structure therein to a position offset from the center of the diffraction unit, adjusts the diffraction efficiency of the diffraction structure, thereby achieving targeted modulation of the outcoupling diffraction efficiency of the outcoupling diffraction element, thereby improving the efficiency uniformity of the diffraction waveguide in which the outcoupling diffraction element is located. Because the outcoupling diffraction element does not involve adjustment of the grating height and duty cycle, the different modulation areas that achieve different diffraction efficiency modulations do not produce noticeable color changes in appearance, thus optimizing the user experience.
[0099] Some embodiments of the present disclosure also provide an out-coupling diffraction element, in which the center offset corresponding to the diffraction units at different positions can be set to different values, which are determined according to the distance from the diffraction unit to the in-coupling diffraction element, thereby modulating the overall efficiency of the diffraction optical waveguide in combination with the transmission efficiency and the out-coupling efficiency to achieve efficiency uniformity regulation.
[0100] Other embodiments disclosed herein also introduce a partitioning mechanism, which divides several diffraction units that are close to the coupling-in diffraction element into the same sub-area, thereby configuring the center offset for the sub-area, reducing the processing difficulty and cost of the coupling-out diffraction element.
[0101] For special scenarios where the centerline of the in-coupling diffraction element does not coincide with the centerline of the out-coupling diffraction element, some embodiments disclosed herein further provide an out-coupling diffraction element in which the diffraction structure within all diffraction units is offset from the center of the diffraction unit in both the horizontal and vertical directions. By adjusting the diffraction structure, the diffraction efficiency of the diffraction orders (+1, +1) and (+1, -1) can be adjusted, thereby achieving control of efficiency uniformity. Furthermore, this arrangement can significantly reduce optimization time and ease processing difficulty.
[0102] Based on the out-coupling diffraction element provided in any of the foregoing embodiments, the presently disclosed embodiment further provides a diffraction optical waveguide, which, in addition to any of the out-coupling diffraction elements described in the foregoing embodiments, further comprises: at least one layer of substrate and an in-coupling diffraction element, wherein the in-coupling diffraction element and the out-coupling diffraction element are both arranged on the substrate.
[0103] Based on the diffractive optical waveguide, the disclosed embodiments further provide a display module, which includes the diffractive optical waveguide described in the previous embodiments and transmits optical signals through the diffractive optical waveguide. In addition to the diffractive optical waveguide, the display module may also include a projection device for projecting the optical signal into an image.
[0104] The disclosed embodiments also provide an electronic device equipped with the aforementioned display module. In some embodiments, the electronic device may be a wearable smart device such as AR glasses or an AR helmet, or other electronic devices, such as a head-up display (HUD) or other in-vehicle devices, which will not be further described here.
[0105] Although a plurality of embodiments of the present disclosure have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art may conceive of many modifications, changes, and alternatives without departing from the ideas and spirit of the present disclosure. It should be understood that in practicing the present disclosure, various alternatives to the embodiments of the present disclosure described herein may be adopted. The appended claims are intended to define the scope of protection of the present disclosure and therefore cover equivalents or alternatives within the scope of these claims.
Claims
1. An outcoupling diffraction element, characterized in that: include: A plurality of periodically arranged diffraction units; In the plurality of periodically arranged diffraction units, the centers of the diffraction structures in a plurality of diffraction units deviate from the centers of the diffraction units in which they are located.
2. The outcoupling diffraction element according to claim 1, characterized in that: The out-coupling diffraction element is a two-dimensional grating, and the diffraction structure is a grating structure.
3. The outcoupling diffraction element according to claim 1, characterized in that: The out-coupling diffraction element is used in conjunction with the in-coupling diffraction element, and the center offset of the diffraction structure in the multiple diffraction units in the out-coupling diffraction element is negatively correlated with the distance from the corresponding diffraction unit to the in-coupling diffraction element.
4. The outcoupling diffraction element according to claim 1, characterized in that: The out-coupling diffraction element includes a plurality of sub-regions, and each sub-region includes a plurality of the diffraction units.
5. The outcoupling diffraction element according to claim 4, characterized in that: For the diffraction units in the same sub-region, the distances from the diffraction units to the coupling-in diffraction elements used in conjunction with the coupling-out diffraction elements are within the same distance range.
6. The outcoupling diffraction element according to claim 5, characterized in that: The direction of the line connecting the center of the plurality of sub-regions matches the propagation direction of the light in the outcoupling diffraction element.
7. The outcoupling diffractive element according to any one of claims 4 to 6, characterized in that: For the diffraction units in the same sub-region, the center offsets of their diffraction structures are the same.
8. The outcoupling diffraction element according to claim 7, characterized in that: In the out-coupling diffraction element, the center offset of the diffraction structure of the diffraction unit in the sub-region is negatively correlated with the distance from the sub-region to the in-coupling diffraction element used in conjunction with the out-coupling diffraction element.
9. The outcoupling diffraction element according to claim 8, characterized in that: In the diffraction direction of the preset diffraction order of the out-coupling diffraction element, the center offset of the diffraction structure of the diffraction unit in the sub-region gradually decreases, wherein the preset diffraction order includes: (0, 0), (+1, +1) and / or (+1, -1).
10. The outcoupling diffraction element according to any one of claims 1 to 6, characterized in that: The deviation direction of the diffraction structure includes at least one of the following directions: horizontal direction and vertical direction.
11. The outcoupling diffraction element according to claim 1, characterized in that: In the out-coupling diffraction element, the diffraction structures of all diffraction units are deviated from the center of the diffraction unit where they are located.
12. The outcoupling diffraction element according to claim 11, characterized in that: In the out-coupling diffraction element, the deviation directions of the diffraction structures of all the diffraction units include horizontal and vertical directions.
13. The outcoupling diffraction element according to claim 11 or 12, characterized in that: In the out-coupling diffraction element, the center offsets of the diffraction structures of all diffraction units are the same.
14. The outcoupling diffraction element according to claim 13, characterized in that: The out-coupling diffraction element and the coupling-in diffraction element used in conjunction therewith form a preset angle in the (0, 0) diffraction order direction, so that the out-coupling diffraction element forms two asymmetric regions on both sides of the (0, 0) diffraction order direction of the coupling-in diffraction element, and the center offset of the diffraction structure in the horizontal and vertical directions is determined according to the efficiency ratio of the two regions formed by the out-coupling diffraction element.
15. A diffractive optical waveguide, characterized in that: include: At least one substrate, an in-coupling diffraction element and an out-coupling diffraction element as claimed in any one of claims 1 to 14, wherein the in-coupling diffraction element and the out-coupling diffraction element are both arranged on the substrate.
16. A display module, characterized in that: include: A diffractive optical waveguide as claimed in claim 15.
17. An electronic device, characterized in that: include: The display module as claimed in claim 16.