Diffraction optical waveguide and near-to-eye display equipment
By setting an auxiliary diffraction structure on the outermost protective sheet of the diffraction waveguide, the surface reflectivity is modulated, which solves the problem that the diffraction structure is easily noticeable, improves the appearance and user experience, and reduces the rainbow effect and light leakage.
Patent Information
- Application Number
- CN202520450526.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-14
- Publication Date
- 2026-01-09
- Estimated Expiration
- 2035-03-14
AI Technical Summary
The existing diffraction structure region of diffractive waveguides is obvious and easily noticeable to onlookers, affecting the appearance and user acceptance.
An auxiliary diffraction structure is set on the entire outermost protective sheet of the diffraction waveguide to modulate the surface reflectivity, improve its uniformity, and hide the diffraction structure.
It effectively conceals the diffraction structure, improves the appearance, enhances market acceptance and user experience, reduces rainbow effects and light leakage, and protects user privacy.
Smart Images
Figure CN223784518U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of augmented reality, and more particularly to a diffractive waveguide and a near-eye display device. 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 diffraction structure region of diffractive waveguides is quite obvious at present. When users use diffractive waveguide-related products, bystanders can easily see the existence of the diffraction structure with the naked eye, which affects the appearance of diffractive waveguides and users' acceptance of diffractive waveguides.
[0004] Therefore, developing a diffraction waveguide that can effectively conceal the diffraction structure and reduce its visual observability has become a key technical challenge that needs to be addressed by those skilled in the art. Utility Model Content
[0005] This application provides a diffractive waveguide and a near-eye display device. An auxiliary diffraction structure is provided on the entire inner side of the outermost protective sheet of the diffractive waveguide. This auxiliary diffraction structure improves the uniformity of visible reflectivity on the outer surface of the diffractive waveguide, making it difficult for onlookers to detect the existence of the diffraction structure region of the waveguide sheet.
[0006] This application provides a diffractive optical waveguide, comprising:
[0007] At least one waveguide sheet and at most two protective sheets; the waveguide sheet and the protective sheets are stacked, and when the number of waveguide sheets is greater than or equal to two, there is no protective sheet between any two waveguide sheets; one of the at most two protective sheets is located on the outermost side away from the human eye;
[0008] The waveguide sheet includes at least an in-line diffraction structure and an out-line diffraction structure, and the outermost protective sheet has an auxiliary diffraction structure on its entire surface facing the waveguide sheet.
[0009] In practice, the difference in external visible reflectance of the auxiliary diffraction structures at different locations on the protective sheet in the visible light band is less than or equal to 5%.
[0010] In practice, the external visible reflectance of the auxiliary diffraction structure is substantially equal to the external visible reflectance of the coupled diffraction structure.
[0011] In practice, the coupled-in diffraction structure, the coupled-out diffraction structure, and the auxiliary diffraction structure are all diffraction grating structures, and the grating period of the auxiliary diffraction structure is smaller than the grating period of the coupled-out diffraction structure.
[0012] In practice, at least one of the following: grating morphology, grating depth, grating duty cycle, and refractive index of the auxiliary diffraction structure varies at different locations on the protective sheet.
[0013] In practice, the gaps between the waveguide sheet and the protective sheet, as well as between the waveguide sheets, are air gaps; or, the gaps are filled with an optical material layer with a refractive index lower than that of the waveguide sheet.
[0014] In practice, the coupled-out diffraction structure includes a first coupled-out diffraction structure and a second coupled-out diffraction structure, the first coupled-out diffraction structure and the second coupled-out diffraction structure being used for the left and right eyes of the human eye, respectively; wherein, along the target direction, the first coupled-out diffraction structure, the coupled-in diffraction structure and the second coupled-out diffraction structure are arranged in sequence.
[0015] In practice, the size of the region where the coupled-in diffraction structure is located in the first direction matches the size of the projected light spot on the coupled-in plane in the first direction, and the size of the region where the coupled-in diffraction structure is located in the second direction is greater than the size of the projected light spot on the coupled-in plane in the second direction, with the first direction and the second direction being orthogonal.
[0016] In practice, the outer contour of the region where the coupled-in diffraction structure is located is capsule-shaped; the outer contours of the regions where the first coupled-out diffraction structure and the second coupled-out diffraction structure are located are polygonal.
[0017] A near-eye display device, the near-eye display device comprising a projection optical engine and a diffractive waveguide as described in any of the preceding claims.
[0018] This application provides a diffractive waveguide and a near-eye display device, wherein the diffractive waveguide includes a waveguide sheet and a protective sheet. The waveguide sheet includes at least an input diffraction structure and an output diffraction structure. The outermost part of the diffractive waveguide is the protective sheet, and the entire inner surface of the protective sheet is provided with an auxiliary diffraction structure. With the help of the auxiliary diffraction structure, the uniformity of visible reflectivity of the outer surface of the diffractive waveguide can be improved, making it difficult for onlookers to detect the existence of the diffraction structure area of the waveguide sheet, effectively hiding the diffraction structure, thereby effectively improving the appearance of the diffractive waveguide, increasing the market acceptance of the diffractive waveguide and the user experience.
[0019] Furthermore, the auxiliary diffraction structure on the protective sheet can be set as a grating structure with a grating period smaller than that of the coupled diffraction structure. This can reduce the amount of ambient light entering the user's field of view through the diffraction waveguide, alleviate the rainbow phenomenon caused by ambient light, and improve the display effect.
[0020] In addition, the auxiliary diffraction structure on the protective sheet can be set as a grating structure with a grating period smaller than that of the coupled diffraction structure. This can reduce the amount of image light of the leakage order entering the external environment, alleviate light leakage, protect user privacy from being leaked, and further improve the market acceptance of diffraction waveguides and the user experience. Attached Figure Description
[0021] 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.
[0022] Figure 1 A schematic diagram of a diffractive waveguide provided in an embodiment of this application;
[0023] Figure 2 This is a schematic diagram of another diffractive waveguide structure provided in an embodiment of this application;
[0024] Figure 3 This is a schematic diagram of another diffractive waveguide structure provided in an embodiment of this application;
[0025] Figure 4 This is a schematic diagram of another diffractive waveguide structure provided in an embodiment of this application;
[0026] Figure 5 This is a schematic diagram of another diffractive waveguide structure provided in an embodiment of this application;
[0027] Attached image labels:
[0028] 1000: Diffractive waveguide;
[0029] 1100: Waveguide sheet; 1110: Coupled-in diffraction structure; 1120: Coupled-out diffraction structure; 1121: First coupled-out diffraction structure; 1122: Second coupled-out diffraction structure;
[0030] 1200: Protective sheet; 1210: Auxiliary diffraction structure;
[0031] 1300: Projected light spot. Detailed Implementation
[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0033] The technical solution of this application will be described in detail below with reference to specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.
[0034] This application provides a diffractive waveguide comprising: at least one waveguide sheet and at most two protective sheets; the waveguide sheet and the protective sheets are stacked, and when the number of waveguide sheets is greater than or equal to two, there is no protective sheet between any two waveguide sheets; one of the at most two protective sheets is disposed on the outermost side away from the human eye; wherein, the waveguide sheet includes at least an in-line diffraction structure and an out-of-line diffraction structure, and the outermost protective sheet has an auxiliary diffraction structure disposed on the entire side facing the waveguide sheet.
[0035] The auxiliary diffraction structure is a micro / nano structure, with a size on the order of visible light wavelengths. It is used to modulate the surface reflectivity of the protective sheet, that is, to modulate the surface reflectivity of the diffraction waveguide. This auxiliary diffraction structure can be formed by wet etching, dry etching, nanoimprinting, or other methods.
[0036] For example, refer to Figure 1 and Figure 2 The two figures illustrate schematic diagrams of the diffractive waveguide structure in different embodiments provided in this application. As can be seen, the diffractive waveguide 1000 includes a waveguide sheet 1100 and a protective sheet 1120. The waveguide sheet 1100 is provided with an in-line diffraction structure 1110 and an out-of-line diffraction structure 1120. The outermost protective sheet 1100 has auxiliary diffraction structures 1210 all over its surface facing the human eye.
[0037] It is understandable that light passing through a diffractive waveguide will undergo reflection and transmission; at least reflected and transmitted light exist. The human eye can distinguish between diffractive and non-diffractive structure regions based on the difference in reflected light or transmitted light between these regions within the visible light band, thus observing the existence of the diffractive structure. In this application, an auxiliary diffractive structure is provided across the entire outermost protective sheet of the diffractive waveguide. This auxiliary diffractive structure modulates the visible reflection of the surface, making the entire area of the diffractive waveguide appear uniformly reflective to an observer. In other words, the entire area of the protective sheet exhibits a basically consistent surface reflectivity, making it difficult for an observer to perceive the existence of the diffractive structure region of the waveguide sheet. This effectively hides the diffractive structure, thereby effectively improving the appearance of the diffractive waveguide, increasing its market acceptance, and enhancing the user experience.
[0038] In practice, the difference in external visible reflectance of auxiliary diffraction structures at different locations on the protective sheet in the visible light band is less than or equal to 5%. It can be understood that when the difference in external visible reflectance of auxiliary diffraction structures at different locations in the visible light band is less than or equal to 5%, the external visible reflectance of the auxiliary diffraction structures at different locations can be considered very close, and the human eye can hardly perceive the difference through visual observation.
[0039] In practice, the external visible reflectance of the auxiliary diffraction structure is approximately equal to that of the coupled diffraction structure. This allows the coupled diffraction structure to be better concealed using the auxiliary diffraction structure.
[0040] In practice, the gaps between the waveguide sheet and the protective sheet, as well as between waveguide sheets, are air gaps, or the gaps are filled with an optical material layer with a refractive index lower than that of the waveguide sheet.
[0041] The lower the refractive index of the medium used in the gaps between the waveguide sheet and the protective sheet, and between the waveguide sheets themselves, the better. This prevents image light transmitted in the waveguide sheet from passing through the gaps into the protective sheet and subsequently being negatively affected by the auxiliary diffraction structure on the protective sheet, thus impacting the imaging effect. Implementably, air gaps are used between the waveguide sheet and the protective sheet, and between the waveguide sheets themselves, with air having a refractive index of 1. These gaps can also be filled with optical material layers with a refractive index lower than 1.55, or even lower than 1.3.
[0042] For example, refer to Figure 1 An air gap exists between the waveguide sheet and the protective sheet; Reference Figure 2 The gaps between the waveguide sheet and the protective sheet, and between the waveguide sheets themselves, are filled with optical material layers.
[0043] Further implementably, the coupled-in diffraction structure, the coupled-out diffraction structure, and the auxiliary diffraction structure are all diffraction grating structures, and the grating period of the auxiliary diffraction structure is smaller than the grating period of the coupled-out diffraction structure.
[0044] It is understandable that diffractive waveguides utilize grating structures to diffract light to achieve image propagation and display. When ambient light (such as sunlight or lamplight) is incident on the grating structure of a diffractive waveguide, light of different wavelengths will be deflected and propagated at different angles during diffraction due to their wavelength differences. This difference in the separation and propagation of different wavelengths of light results in a rainbow-like effect, or halo effect, when observed from a specific angle. In particular, the rainbow effect caused by large-angle ambient light will appear within the user's normal field of vision, reducing image clarity and contrast, and to some extent affecting the display effect and user experience of diffractive waveguide devices.
[0045] This application, based on improving the visibility of the diffraction structure of the waveguide by utilizing the auxiliary diffraction structure on the protective sheet, further designs the auxiliary diffraction structure as a diffraction grating structure with a grating period smaller than that of the coupled diffraction structure. After ambient light is incident on the protective sheet, it is coupled into the protective sheet by the diffraction grating structure on the protective sheet and transmitted through total internal reflection, or it is converted into an evanescent wave and rapidly attenuated by the diffraction grating structure on the protective sheet. This reduces the amount of ambient light incident on the diffraction structure of the waveguide, especially ambient light at large angles, and can alleviate the rainbow phenomenon caused by ambient light.
[0046] Furthermore, when a diffractive waveguide uses a grating structure to diffract image light, transmission and reflection orders with opposite transmission directions exist simultaneously. While one diffraction order is effectively used for human eye imaging, the other diffraction order may leak into the external environment. In this application, the leakage order from the coupling grating structure first enters the protective sheet before leaking into the external environment. It is then coupled into the protective sheet by the diffraction grating structure and transmitted through total internal reflection within the protective sheet. Alternatively, it is converted into an evanescent wave and rapidly attenuated by the diffraction grating structure on the protective sheet, reducing the amount of image light leaking into the external environment and mitigating the light leakage phenomenon.
[0047] Implementably, at least one of the following: grating morphology, grating depth, grating duty cycle, and refractive index of the auxiliary diffraction structure varies at different locations on the protective sheet.
[0048] Specifically, the grating parameters of the auxiliary diffraction structure, such as grating morphology, grating depth, grating duty cycle, and refractive index, can be locally or globally modulated to further optimize rainbow and light leakage phenomena.
[0049] For example, refer to Figure 3In outdoor scenarios, sunlight is incident on the diffractive waveguide at a large angle. It first passes through the outermost protective sheet of the diffractive waveguide. The grating parameters of the diffraction grating structure on the protective sheet are designed so that most of the sunlight is diffracted into the protective sheet for transmission, thereby reducing the light energy reaching the waveguide sheet and weakening the rainbow effect.
[0050] For example, refer to Figure 4 When a user uses a diffractive waveguide, the leakage order away from the human eye first passes through the outermost protective sheet of the diffractive waveguide. The grating parameters of the diffraction grating structure on the protective sheet are designed so that most of the image light of the leakage order is diffracted into the protective sheet and transmitted by total internal reflection, thereby reducing the light energy of the image light reaching the external environment and reducing the light leakage phenomenon.
[0051] In some embodiments, the diffractive waveguide provided in this application can also be used for binocular displays. Specifically, the coupled-out diffraction structure includes a first coupled-out diffraction structure and a second coupled-out diffraction structure, which are respectively used for the left and right eyes of the human eye; wherein, the first coupled-out diffraction structure, the coupled-in diffraction structure, and the second coupled-out diffraction structure are arranged sequentially along the target direction.
[0052] Specifically, after the image light emitted from the projection optical engine is incident on the coupling diffraction structure, a portion of the image light is driven into the waveguide by the coupling diffraction structure and transmitted through total internal reflection towards the first coupling diffraction structure. This portion of the image light is coupled out through the first coupling diffraction structure and enters the left eye. Another portion of the image light is driven into the waveguide by the coupling diffraction structure and transmitted through total internal reflection towards the second coupling diffraction structure. This portion of the image light is coupled out through the second coupling diffraction structure and enters the right eye. In this way, binocular display is achieved through a single projection optical engine.
[0053] For example, refer to Figure 5 Taking a Cartesian coordinate system as an example, the coupling plane of the diffracting waveguide 1000 is defined as the XOY plane, and the target direction is the X-axis direction. It can be seen that the waveguide sheet 1100 includes a coupling-in diffraction structure 1110, a first coupling-out diffraction structure 1121, and a second coupling-out diffraction structure 1122. Furthermore, the first coupling-out diffraction structure 1121, the coupling-in diffraction structure 1110, and the second coupling-out diffraction structure 1122 are arranged sequentially along the X-axis direction.
[0054] In practice, the size of the region where the coupling diffraction structure is located in the first direction matches the size of the projected light spot on the coupling plane in the first direction, and the size of the region where the coupling diffraction structure is located in the second direction is greater than the size of the projected light spot on the coupling plane in the second direction, with the first direction and the second direction being orthogonal.
[0055] It is understandable that in the prior art, in order to maximize the light utilization efficiency of the diffractive waveguide by receiving as much image light as possible from the projector, a prevailing view has emerged that the coupling structure should avoid field-of-view loss and light leakage when receiving image light from the projector. Consequently, it is generally believed that the size of the coupling structure should be comparable to the projection spot projected onto the coupling plane, and that the optical axis of the projector should be aligned with the center of the coupling structure. However, this application breaks with this technical bias by specifically designing that the size of the region containing the coupling diffractive structure in the second direction is larger than the size of the projection spot on the coupling plane in the second direction, without affecting the original effective light propagation path; moreover, it eliminates the requirement that the optical axis of the projector be aligned with the center of the coupling structure, thus enabling the adaptation to more optical engine positions and diffractive waveguide shapes. That is, from... Figure 5 As can be seen, the size of the region where the coupled diffraction structure 1110 is located in the Y-axis direction is expanded, which is significantly larger than the size of the region where the coupled diffraction structure 1110 is located in the X-axis direction, and significantly larger than the size of the projected spot 1300.
[0056] In practice, the outer contour of the region containing the coupled-in diffraction structure is capsule-shaped. The outer contours of the regions containing the first coupled-out diffraction structure and the second coupled-out diffraction structure are both polygonal.
[0057] For example, continue to refer to Figure 5 As can be seen, the region where the coupled-in diffraction structure 1110 is located is capsule-shaped, with semicircles at both ends and a rectangle in the middle. The regions where the first coupled-out diffraction structure 1121 and the second coupled-out diffraction structure 1122 are located are quadrilaterals.
[0058] This application also provides a near-eye display device, which includes a projection optical engine and a diffractive waveguide as described in any of the foregoing embodiments. The optical engine is used to project light carrying image information over a predetermined field of view. In this application, the optical engine can be of different types, such as uLED, LCOS, DLP, LBS, OLED, etc. Since the near-eye display device includes the aforementioned diffractive waveguide, it possesses all the advantages of the aforementioned diffractive waveguide.
[0059] Furthermore, the diffractive waveguide provided in this application can also be used in other augmented reality display devices or mixed reality display devices, such as head-up displays. These devices retain all the advantages of the diffractive waveguide provided in this application.
[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A diffractive optical waveguide, characterized in that, The diffractive waveguide includes: At least one waveguide sheet and at most two protective sheets; the waveguide sheet and the protective sheets are stacked, and when the number of waveguide sheets is greater than or equal to two, there is no protective sheet between any two waveguide sheets; one of the at most two protective sheets is located on the outermost side away from the human eye; The waveguide sheet includes at least an in-line diffraction structure and an out-line diffraction structure, and the outermost protective sheet has an auxiliary diffraction structure on its entire surface facing the waveguide sheet.
2. The diffractive waveguide according to claim 1, characterized in that, The difference in external visible reflectance of the auxiliary diffraction structures at different positions on the protective sheet in the visible light band is less than or equal to 5%.
3. The diffractive waveguide according to claim 2, characterized in that, The external visible reflectance of the auxiliary diffraction structure is substantially equal to the external visible reflectance of the coupled diffraction structure.
4. The diffractive waveguide according to claim 1, characterized in that, The coupled-in diffraction structure, the coupled-out diffraction structure, and the auxiliary diffraction structure are all diffraction grating structures, and the grating period of the auxiliary diffraction structure is smaller than the grating period of the coupled-out diffraction structure.
5. The diffractive waveguide according to claim 4, characterized in that, At least one of the following characteristics of the auxiliary diffraction structure—grating morphology, grating depth, grating duty cycle, and refractive index—may differ at different locations on the protective sheet.
6. The diffractive waveguide according to claim 1, characterized in that, The gaps between the waveguide sheet and the protective sheet, as well as between the waveguide sheets, are air gaps, or the gaps are filled with an optical material layer with a refractive index lower than that of the waveguide sheet.
7. The diffractive waveguide according to claim 1, characterized in that, The coupled-out diffraction structure includes a first coupled-out diffraction structure and a second coupled-out diffraction structure, which are respectively used for the left and right eyes of the human eye; wherein, the first coupled-out diffraction structure, the coupled-in diffraction structure, and the second coupled-out diffraction structure are arranged sequentially along the target direction.
8. The diffractive waveguide according to claim 7, characterized in that, The size of the region where the coupled-in diffraction structure is located in the first direction matches the size of the projected light spot on the coupled-in plane in the first direction. The size of the region where the coupled-in diffraction structure is located in the second direction is larger than the size of the projected light spot on the coupled-in plane in the second direction. The first direction and the second direction are orthogonal.
9. The diffractive waveguide according to claim 8, characterized in that, The outer contour of the region where the coupled-in diffraction structure is located is capsule-shaped; the outer contours of the regions where the first coupled-out diffraction structure and the second coupled-out diffraction structure are located are polygonal.
10. A near-eye display device, characterized in that, The near-eye display device includes a projection optical engine and a diffractive waveguide as described in any one of claims 1-9.