Diffractive optical waveguide

Abstract

The application provides a diffraction optical waveguide, comprising: a waveguide substrate, a surface of the waveguide substrate comprising a grating structure region and a non-grating structure region; at least a coupling-in grating structure and a coupling-out grating structure are arranged in the grating structure region, the coupling-in grating structure is used for coupling image light into the waveguide substrate, and the coupling-out grating structure is used for coupling image light out of the waveguide substrate; the non-grating structure region is provided with a first auxiliary structure, a region corresponding to the coupling-out grating structure is provided with a second auxiliary structure, the first auxiliary structure is used for modulating the transmittance of the non-grating structure region, the second auxiliary structure is used for modulating the transmittance of the grating structure region, and the change trend of the transmittance of the grating structure region and the non-grating structure region in the visible light waveband is basically consistent. The application can weaken the recognizable features of the grating structure under naked eye observation, and improve the use experience of the diffraction optical waveguide.

Description

Technical Field

[0001] This application relates to the field of augmented reality display technology, and more particularly to a diffractive optical waveguide. Background Technology

[0002] Augmented reality is a technology that blends the real world with virtual information. Augmented reality display systems typically include micro-projectors and optical displays. The micro-projectors provide virtual display content for the augmented reality display system, which is then projected onto the viewer's eyes through the optical displays. The optical displays are usually transparent optical components, so that users can also see the real world through the optical displays at the same time.

[0003] However, the grating structure within the grating region of current diffractive waveguides is generally visible to the naked eye, affecting the appearance of the diffractive waveguide and the user's acceptance and experience. Therefore, developing a diffractive waveguide that can effectively hide the grating structure and weaken its identifiable features under naked-eye observation has become a key technical challenge that urgently needs to be addressed by those skilled in the art. Utility Model Content

[0004] This application provides a diffractive waveguide that can reduce the visual identifiability of grating structures, thereby improving user acceptance and experience.

[0005] A diffractive waveguide includes: a waveguide substrate, the surface of which includes a grating structure region and a non-grating structure region; at least an input grating structure and an output grating structure are disposed within the grating structure region, the input grating structure being used to couple image light into the waveguide substrate, and the output grating structure being used to couple image light out of the waveguide substrate; a first auxiliary structure is disposed within the non-grating structure region, and a second auxiliary structure is disposed within the region corresponding to the output grating structure, the first auxiliary structure being used to modulate the transmittance of the non-grating structure region, and the second auxiliary structure being used to modulate the transmittance of the grating structure region, wherein the transmittance of the grating structure region and the non-grating structure region exhibits the same trend in the visible light band.

[0006] In practice, both the first auxiliary structure and the second auxiliary structure are periodically arranged auxiliary microstructures, or both the first auxiliary structure and the second auxiliary structure are dielectric material layers; wherein the period of the auxiliary microstructure is less than the period of any grating structure within the grating structure region.

[0007] In practice, the structural parameters of the first auxiliary structure and the second auxiliary structure are different, so that the trend of the transmittance of the grating structure region and the non-grating structure region in the visible light band before and after the first auxiliary structure and the second auxiliary structure are set is changed from being different to being consistent.

[0008] In practice, the first auxiliary structure is a periodically arranged auxiliary microstructure, and the second auxiliary structure is a dielectric material layer; or, the first auxiliary structure is a dielectric material layer, and the second auxiliary structure is a periodically arranged auxiliary microstructure; wherein the period of the auxiliary microstructure is less than the period of any grating structure within the grating structure region.

[0009] In practice, a low-refractive-index material layer is formed on the surface of the waveguide substrate on the side where the grating structure is located. The low-refractive-index material layer fills the groove of the grating structure, and the top of the low-refractive-index material layer is flush with the top of the grating structure. The second auxiliary structure is disposed on the low-refractive-index material layer.

[0010] Implementably, the period of the auxiliary microstructure is less than the quotient of the working wavelength and the refractive index of the auxiliary microstructure; and / or, the aspect ratio of the auxiliary microstructure is in the range of [λ / 540, λ / 100], where λ is the working wavelength; and / or, the height of the auxiliary microstructure is greater than one-quarter of the working wavelength and less than one-half of the working wavelength.

[0011] In practice, the dielectric material layer includes one or more anti-reflective layers, and the material of the anti-reflective layer includes magnesium fluoride, silicon oxide, and titanium oxide.

[0012] In practice, the thickness of the antireflective layer can range from 20 nanometers to 300 nanometers.

[0013] In practice, the surface of the coupling grating structure is provided with the dielectric material layer, and the side surface of the waveguide substrate on which the coupling grating structure is not provided is also provided with the dielectric material layer at the position opposite to the coupling grating structure.

[0014] In practice, a transition grating structure is provided within the grating structure region, and a second auxiliary structure is provided in the region corresponding to the transition grating structure; the second auxiliary structure provided corresponding to the transition grating structure differs from the second auxiliary structure provided corresponding to the coupling grating structure in terms of material or structural parameters.

[0015] This application provides a diffractive waveguide that cleverly achieves visual concealment of the grating region through optical structure design. Specifically, a first auxiliary structure and a second auxiliary structure are introduced into the non-grating structure region and the grating structure region of the waveguide substrate, respectively, to adjust the transmittance of the two regions in the visible light band. This ensures that the transmittance curves of the grating structure region and the non-grating structure region are essentially consistent with the visible light wavelength. Visually, the uniformity of the overall transmittance variation makes it impossible for the human eye to visually distinguish the specific distribution range or boundary position of the grating structure, fundamentally eliminating the inherent visual distinctiveness of the grating structure. This significantly improves the visual integrity of the diffractive waveguide and the sensory comfort of the user. While achieving visual concealment, this diffractive waveguide maintains efficient coupling and transmission performance of guided light within the operating wavelength range, balancing functionality and aesthetics.

[0016] Furthermore, the first and second auxiliary structures can be microstructure arrays or composite film systems. By optimizing the material combination, geometric parameters, and layer thickness configuration of the first and second auxiliary structures, precise control of the reflection characteristics in the visible light band can be achieved. Thus, without affecting the diffraction efficiency of the guided light, the transmittance of the two regions in the visible light band can be adjusted respectively, so that the grating area and the non-grating area present a consistent visual effect. This ensures that the transmittance at different wavelengths under different viewing angles remains at a high level, achieving the effects of wide band, wide viewing angle, and ultra-low reflection. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a diffractive waveguide provided in one embodiment of this application;

[0019] Figure 2 A schematic diagram of a diffractive waveguide provided in another embodiment of this application;

[0020] Figure 3 A schematic diagram of a diffractive waveguide provided in another embodiment of this application;

[0021] Figure 4 A schematic diagram of a diffractive waveguide provided in another embodiment of this application;

[0022] Figure 5Transmittance curves of the non-grating structure region and the grating structure region in the visible light band after adding a first auxiliary structure and a second auxiliary structure to the diffractive waveguide according to one embodiment of this application.

[0023] Figure 6 Transmittance curves of the non-grating structure region and the grating structure region in the visible light band after adding a first auxiliary structure and a second auxiliary structure to the diffractive waveguide, as provided in another embodiment of this application.

[0024] Figure label:

[0025] 100: Diffractive waveguide; 110: Waveguide substrate; 120: Coupled-in grating structure; 130: Coupled-out grating structure; 140: First auxiliary structure; 150: Second auxiliary structure. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] This application provides a diffractive waveguide, characterized in that it comprises: a waveguide substrate, the surface of which includes a grating structure region and a non-grating structure region; at least an input grating structure and an output grating structure are disposed within the grating structure region, the input grating structure being used to couple image light into the waveguide substrate, and the output grating structure being used to couple image light out of the waveguide substrate; a first auxiliary structure is disposed within the non-grating structure region, and a second auxiliary structure is disposed within the region corresponding to the output grating structure, the first auxiliary structure being used to modulate the transmittance of the non-grating structure region, and the second auxiliary structure being used to modulate the transmittance of the grating structure region, wherein the transmittance of the grating structure region and the non-grating structure region exhibits the same trend in the visible light band. It should be noted that the "same trend in transmittance" in this application does not require absolute mathematical consistency, but can be implemented as essentially consistent, within the range allowed by performance indicators.

[0029] It is understood that the grating structure region contains diffraction coupling elements capable of realizing virtual image light imaging, such as coupling-in grating structures and coupling-out grating structures, while the non-grating structure region is left blank or contains other optical structures that do not affect the imaging function. That is to say, the optical structures included in the grating structure region and the non-grating structure region are different, and their modulation effects on incident ambient light are also different. Specifically, in this application, by introducing a first auxiliary structure and a second auxiliary structure in the non-grating structure region and the grating structure region respectively, the transmittance difference between the grating structure region and the non-grating structure region in the visible light band is effectively balanced, reducing visual distortion and optical crosstalk caused by the inconsistency in transmittance between regions, and improving the uniformity of imaging and visual comfort. The first auxiliary structure and the second auxiliary structure can be set on the same side of the diffractive waveguide or on different sides of the diffractive waveguide. The first auxiliary structure and the second auxiliary structure can adopt the same optical structure but different structural parameters, or they can adopt different optical structures. By differentiating the first auxiliary structure and the second auxiliary structure, the optical characteristics of their respective regions can be matched, thereby achieving the coordination and consistency of the overall transmittance.

[0030] In some embodiments, the first auxiliary structure and the second auxiliary structure may be the same optical structure. Specifically, both the first and second auxiliary structures may be periodically arranged auxiliary microstructures, with the period of the auxiliary microstructures being less than the period of any grating structure within the grating structure region. Alternatively, both the first and second auxiliary structures may be dielectric material layers.

[0031] Further implementably, the structural parameters of the first auxiliary structure and the second auxiliary structure are different, so that the trend of the change in transmittance of the grating structure region and the non-grating structure region in the visible light band before and after the first auxiliary structure and the second auxiliary structure are set is changed from being different to being consistent.

[0032] In some embodiments, the first auxiliary structure and the second auxiliary structure may be selected from different optical structures. Specifically, the first auxiliary structure may be a periodically arranged auxiliary microstructure, and the second auxiliary structure may be a dielectric material layer; or, the first auxiliary structure may be a dielectric material layer, and the second auxiliary structure may be a periodically arranged auxiliary microstructure; wherein the period of the auxiliary microstructure is less than the period of any grating structure within the grating structure region.

[0033] In an implementable manner, a low-refractive-index material layer is formed on the surface of the waveguide substrate on the side where the grating structure is located. The low-refractive-index material layer fills the groove of the grating structure, and the top of the low-refractive-index material layer is flush with the top of the grating structure. A second auxiliary structure is disposed on the low-refractive-index material layer. The low-refractive-index material layer may cover only the grating structure area or it may cover the entire surface of the waveguide substrate. Of course, in some embodiments, the top of the low-refractive-index material layer does not need to be flush with the top of the grating structure, but the top of the low-refractive-index material layer is flat.

[0034] When the second auxiliary structure is a dielectric material layer, the low-refractive-index material layer is the dielectric material layer. When there is more than one dielectric material layer, the low-refractive-index material layer is the bottom layer of the dielectric material layer, and the top of the low-refractive-index material layer does not need to be flush with the top of the grating structure, but the top of the dielectric material layer is flat.

[0035] For example, refer to Figure 1 This figure illustrates a schematic diagram of a diffractive waveguide according to an embodiment of this application. The diffractive waveguide 100 includes a waveguide substrate 110. The surface of the waveguide substrate 110 includes a grating structure region and a non-grating structure region. The region enclosed by the short dashed box is the grating structure region. The left region is the coupling-in region, in which a coupling-in grating structure 120 is disposed, used to couple image light into the waveguide substrate 110. The right region is the coupling-out region, in which a coupling-out grating structure 130 is disposed, used to couple image light out from the waveguide substrate. A first auxiliary structure 140 is disposed in the non-grating structure region, and a second auxiliary structure 150 is arranged on the coupling-out grating structure 130. The first auxiliary structure 140 and the second auxiliary structure 150 are disposed on the same side of the diffractive waveguide and on the same side as the diffraction coupling structure. The first auxiliary structure 140 and the second auxiliary structure 150 can be periodically arranged auxiliary microstructures or dielectric material layers. Of course, in other implementations, such as Figure 2 As shown, the first auxiliary structure 140 and the second auxiliary structure 150 can also be disposed on the same side of the diffractive waveguide, but on a different side from the diffractive coupling structure; for example... Figure 3 As shown, the first auxiliary structure 140 and the second auxiliary structure 150 can also be disposed on different sides of the diffractive waveguide; for example... Figure 4As shown, a second auxiliary structure 150 can also be provided on both sides of the diffractive waveguide.

[0036] It is understood that when diffractive waveguides are assembled into near-eye display devices, the coupling region is typically encapsulated within the near-eye display device and not exposed to the external environment, making it invisible to the naked eye. Based on this, when modulating the transmittance and structural visibility of the diffractive waveguide in the visible light band, only the area exposed to the external environment and visible to the naked eye needs to be considered. For areas not exposed to the external environment, there is no need to set up the first and second auxiliary structures, thus simplifying the process and reducing costs. For example, refer to... Figure 2 and Figure 3 In this embodiment, the first and second auxiliary structures are not provided for the coupling area and its surrounding parts that are not exposed to the external environment. The first auxiliary structure 140 and the second auxiliary structure 150 are only provided in the coupling area and its surrounding visible range, thereby ensuring the consistency of transmittance in the appearance area while reducing unnecessary process steps. This design effectively reduces manufacturing complexity and cost while ensuring optical performance, and is especially suitable for mass-produced near-eye display devices.

[0037] Furthermore, when the first and second auxiliary structures provided in this application are implemented as periodically arranged auxiliary microstructures, specifically:

[0038] In practice, the period of the auxiliary microstructure is less than the quotient of the operating wavelength and the refractive index of the auxiliary microstructure. Specifically, the grating structure is distributed in a periodic array on the surface of the waveguide substrate, including several independent grating units, with regularly arranged groove structures formed between adjacent grating units. When the second auxiliary structure disposed on the surface coupled out of the grating structure is a periodically arranged auxiliary microstructure, the auxiliary microstructure can be formed directly on the grating structure, or a filling layer can be formed on the grating structure before the auxiliary microstructure is formed.

[0039] To avoid the auxiliary microstructure introducing new diffraction orders and creating additional propagable diffraction orders, the period of the auxiliary microstructure should be less than λ / n1, where λ is the operating wavelength and n1 is the refractive index of air. More preferably, considering its effective wavelength within the medium, the period of the auxiliary microstructure should be less than λ / n2, where n2 is the refractive index of the auxiliary microstructure. Implementably, the period of the auxiliary microstructure can be less than λ / 4.

[0040] In practice, the height of the auxiliary microstructure is greater than one-quarter and less than one-half of the operating wavelength. Specifically, the height of the auxiliary microstructure mainly determines the initial modulation intensity of the incident / emitted light. If the height of the auxiliary microstructure is too shallow, the resulting optical path difference will be too small, and the corresponding phase shift will be insufficient to achieve the desired effect. If the height of the auxiliary microstructure is too deep, it will introduce higher-order diffraction or loss. Based on this, the height of the auxiliary microstructure is generally designed to be λ / 4 to λ / 2 to achieve specific phase compensation.

[0041] Implementably, the aspect ratio of the auxiliary microstructure can range from [λ / 540, λ / 100], where λ is the operating wavelength. For example, the aspect ratio of the auxiliary microstructure can range from [1, 5].

[0042] For example, in a specific embodiment, the diffractive waveguide includes a waveguide substrate with a refractive index ranging from 1.58 to 2.5; a grating structure is disposed on the surface of the waveguide substrate with a refractive index ranging from 1.7 to 2.5, a height ranging from 20 to 250 nm, and a period ranging from 250 to 500 nm; a low-refractive-index material layer is formed on the grating structure to fill the grooves of the grating structure, the thickness of the low-refractive-index material layer being consistent with the height of the grating structure, and the refractive index of the low-refractive-index material layer ranging from 1.15 to 2; an auxiliary microstructure is formed on the low-refractive-index material layer, the auxiliary microstructure covering the entire surface of the waveguide substrate, the refractive index of the auxiliary microstructure ranging from 1.15 to 1.6, the height of the auxiliary microstructure ranging from 70 to 200 nm, the duty cycle of the auxiliary microstructure ranging from 0.3 to 0.7, and the period of the auxiliary microstructure ranging from 20 to 180 nm.

[0043] Furthermore, when the first and second auxiliary structures provided in this application are implemented as dielectric material layers, specifically:

[0044] In practice, the dielectric material layer may include one or more anti-reflective layers, and the anti-reflective layer may be made of materials such as magnesium fluoride, silicon oxide, or titanium oxide.

[0045] In practice, the thickness of the anti-reflective layer can range from 20 nanometers to 300 nanometers.

[0046] In practice, a dielectric material layer is provided on the surface of the coupling grating structure, and a dielectric material layer is also provided on the side of the waveguide substrate where the coupling grating structure is not provided, at the position opposite to the coupling grating structure.

[0047] For example, refer to Figure 5This figure illustrates the transmittance curves of the non-grating structure region and the grating structure region in the visible light band after adding a first auxiliary structure and a second auxiliary structure to the diffractive waveguide according to an embodiment provided in this application. In this embodiment, the first auxiliary structure is a periodically arranged auxiliary microstructure, positioned opposite to the diffraction coupling structure. The microstructure unit is a cylindrical structure with a period of 150 nm, a duty cycle of 0.3, and a height of 40 nm. The second microstructure is a silicon dioxide layer, also positioned opposite to the diffraction coupling structure, with a thickness of 60 nm. The horizontal axis of the figure represents wavelength, and the vertical axis represents transmittance. It can be seen that the transmittance trends of the grating structure region and the non-grating structure region in the visible light band are basically the same. Moreover, the transmittance difference between the two regions is approximately 2% in the blue light band, approximately 1% in the green light band, and approximately 0.3% in the red light band.

[0048] For example, refer to Figure 6 This figure illustrates the transmittance curves of the non-grating structure region and the grating structure region in the visible light band after adding a first auxiliary structure and a second auxiliary structure to the diffractive waveguide in one embodiment of this application. In this embodiment, the first auxiliary structure is a periodically arranged auxiliary microstructure, disposed on the opposite side of the diffraction coupling structure. The microstructure unit is a cylindrical structure with a period of 150 nm, a duty cycle of 0.5, and a height of 85 nm. The second microstructure is a silicon dioxide layer, disposed on both sides of the diffractive waveguide, with a thickness of 110 nm. The horizontal axis of the figure represents wavelength, and the vertical axis represents transmittance. It can be seen that the transmittance trends of the grating structure region and the non-grating structure region in the visible light band are basically the same. Moreover, the transmittance difference between the two regions is approximately 3% in the blue light band, approximately 3% in the green light band, and approximately 0.3% in the red light band.

[0049] contrast Figure 5 and Figure 6 As can be seen, when the transmittance trends of the grating structure region and the non-grating structure region in the visible light band are basically the same, the overall transmittance is higher when a second auxiliary structure is set on both sides of the grating structure region compared to the case where a second auxiliary structure is set on only one side, especially in the green and blue light bands.

[0050] In some embodiments, the grating structure region may further include grating structures such as a bend grating structure or a retractable grating structure to achieve other auxiliary virtual image light imaging. The regions corresponding to these grating structures are also provided with a second auxiliary structure. Specifically, a bend grating structure is provided within the grating structure region, and a second auxiliary structure is provided in the region corresponding to the bend grating structure. The second auxiliary structure provided for the bend grating structure differs from the second auxiliary structure provided for the corresponding coupling grating structure in terms of material or structural parameters.

[0051] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A diffractive optical waveguide, characterized in that, include: A waveguide substrate, the surface of which includes a grating structure region and a non-grating structure region; at least an input grating structure and an output grating structure are provided in the grating structure region, the input grating structure is used to couple image light into the waveguide substrate, and the output grating structure is used to couple image light out of the waveguide substrate; a first auxiliary structure is provided in the non-grating structure region, and a second auxiliary structure is provided in the region corresponding to the output grating structure, the first auxiliary structure is used to modulate the transmittance of the non-grating structure region, and the second auxiliary structure is used to modulate the transmittance of the grating structure region, and the transmittance of the grating structure region and the non-grating structure region have the same trend in the visible light band.

2. The diffractive waveguide according to claim 1, characterized in that, Both the first auxiliary structure and the second auxiliary structure are periodically arranged auxiliary microstructures, or both the first auxiliary structure and the second auxiliary structure are dielectric material layers; wherein the period of the auxiliary microstructure is less than the period of any grating structure within the grating structure region.

3. The diffractive waveguide according to claim 2, characterized in that, The first auxiliary structure and the second auxiliary structure have different structural parameters, so that the trend of the transmittance of the grating structure region and the non-grating structure region in the visible light band changes from being different to being consistent before and after the first auxiliary structure and the second auxiliary structure are set.

4. The diffractive waveguide according to claim 1, characterized in that, The first auxiliary structure is a periodically arranged auxiliary microstructure, and the second auxiliary structure is a dielectric material layer; or, the first auxiliary structure is a dielectric material layer, and the second auxiliary structure is a periodically arranged auxiliary microstructure; wherein, the period of the auxiliary microstructure is less than the period of any grating structure within the grating structure region.

5. The diffractive waveguide according to claim 2 or 4, characterized in that, A low-refractive-index material layer is formed on the surface of the waveguide substrate on the side where the grating structure is located. The low-refractive-index material layer fills the groove of the grating structure, and the top of the low-refractive-index material layer is flush with the top of the grating structure. The second auxiliary structure is disposed on the low-refractive-index material layer.

6. The diffractive waveguide according to claim 2 or 4, characterized in that, The period of the auxiliary microstructure is less than the quotient of the working wavelength and the refractive index of the auxiliary microstructure; and / or, the aspect ratio of the auxiliary microstructure is in the range of [λ / 540, λ / 100], where λ is the working wavelength; and / or, the height of the auxiliary microstructure is greater than one-quarter of the working wavelength and less than one-half of the working wavelength.

7. The diffractive waveguide according to claim 2 or 4, characterized in that, The dielectric material layer includes one or more anti-reflective layers, and the anti-reflective layer is made of materials such as magnesium fluoride, silicon oxide, and titanium oxide.

8. The diffractive waveguide according to claim 7, characterized in that, The thickness of the anti-reflective layer ranges from 20 nanometers to 300 nanometers.

9. The diffractive waveguide according to claim 7, characterized in that, The surface of the coupling grating structure is provided with the dielectric material layer, and the surface of the waveguide substrate on the side where the coupling grating structure is not provided is also provided with the dielectric material layer at the position opposite to the coupling grating structure.

10. The diffractive waveguide according to claim 1, characterized in that, A transition grating structure is provided within the grating structure region, and a second auxiliary structure is provided in the region corresponding to the transition grating structure; the second auxiliary structure provided for the transition grating structure differs from the second auxiliary structure provided for the coupling grating structure in terms of material or structural parameters.

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