Diffractive optical waveguide and display device

Abstract

The application discloses a kind of diffractive optical waveguide and display equipment.Diffractive optical waveguide includes substrate and dielectric layer;At least one side of substrate is provided with grating structure, dielectric layer is located at the side of grating structure away from substrate;Wherein, the refractive index of substrate is greater than 2, the absolute value of refractive index difference between dielectric layer and substrate is greater than or equal to 0.5, the thickness of dielectric layer is greater than 3 μm.Above-mentioned scheme is adopted, dielectric layer can play the protection effect to grating structure, since the contact area of dielectric layer and substrate is larger, the better protection and fixed effect can be achieved by using thin dielectric layer, on the basis of guaranteeing the reliability of diffractive optical waveguide, the thickness of diffractive optical waveguide is reduced, and the weight of display equipment is reduced.In addition, by designing the refractive index of substrate and the refractive index difference between substrate and dielectric layer, the diffraction efficiency of grating structure can be improved, large field angle transmission and single piece full color transmission can be realized, so as to improve the overall performance of diffractive optical waveguide.

Description

Technical Field

[0001] The present invention relates to the field of optical waveguide technology, and more particularly to a diffractive optical waveguide and a display device. Background Technology

[0002] Augmented Reality (AR) is a technology that overlays and merges virtual scenes or information with the real physical environment, presenting them interactively to the user and creating a shared space between the virtual and real worlds. AR display devices (such as AR glasses) have become widely used as a new generation of electronic interactive devices, but currently, AR display devices suffer from problems such as heavy weight and uneven display brightness, affecting the user experience. Summary of the Invention

[0003] In view of this, the present invention provides a diffractive waveguide and a display device to reduce the thickness of the diffractive waveguide, reduce the weight of the display device, and improve the uniformity of display brightness.

[0004] In a first aspect, embodiments of the present invention provide a diffractive optical waveguide, comprising a substrate and a dielectric layer;

[0005] A grating structure is provided on at least one side of the substrate, and the dielectric layer is located on the side of the grating structure away from the substrate;

[0006] Among them, the refractive index of the substrate is greater than 2, the absolute value of the difference between the refractive indices of the dielectric layer and the substrate is greater than or equal to 0.5, and the thickness of the dielectric layer is greater than 3 μm.

[0007] Secondly, embodiments of the present invention also provide a display device, including the diffractive waveguide provided in any embodiment of the present invention.

[0008] In this embodiment of the invention, a dielectric layer is provided in the diffractive waveguide. The dielectric layer protects the grating structure. Since the contact area between the dielectric layer and the substrate is large, a thin dielectric layer can achieve good protection and fixation. While ensuring the reliability of the diffractive waveguide, the thickness of the waveguide is reduced, thereby lowering the weight of the display device. Furthermore, by designing the refractive index of the substrate and the refractive index difference between the substrate and the dielectric layer, the diffraction efficiency of the grating structure can be improved, enabling large field-of-view transmission and single-chip full-color transmission, thus enhancing the overall performance of the diffractive waveguide. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of a diffractive waveguide provided in an embodiment of the present invention;

[0010] Figure 2 This is a schematic diagram of another diffractive waveguide structure provided in an embodiment of the present invention;

[0011] Figure 3 This is a schematic diagram of another diffractive waveguide structure provided in an embodiment of the present invention;

[0012] Figure 4 This is a schematic diagram of another diffractive waveguide structure provided in an embodiment of the present invention;

[0013] Figure 5 This is a schematic diagram of another diffractive waveguide structure provided in an embodiment of the present invention;

[0014] Figure 6 This is a schematic diagram of another diffractive waveguide structure provided in an embodiment of the present invention. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0016] Diffractive waveguides are widely used in AR display devices due to their superior display quality and thinness. Taking AR glasses as an example, in related technologies, the diffractive waveguide in AR glasses includes a waveguide substrate and a protective sheet. The waveguide substrate and the protective sheet are bonded together by edge adhesive bonding, with the protective sheet protecting the grating on the waveguide substrate. The inventors discovered that to ensure the bonding strength between the waveguide substrate and the protective sheet, a relatively thick edge adhesive is generally required, typically exceeding 200 μm. Furthermore, in the adhesive bonding method, the protective sheet is the primary source of reliability, requiring a thickness greater than 500 μm. This results in a relatively large overall thickness of the diffractive waveguide, leading to a heavier AR glasses and impacting the user experience. Additionally, the diffractive waveguides in related technologies exhibit poor uniformity of emitted light brightness. Uneven brightness can cause image distortion, and prolonged viewing can lead to eye discomfort and visual fatigue.

[0017] In view of the shortcomings of the aforementioned related technologies, this invention proposes a diffractive optical waveguide. Figure 1 This is a schematic diagram of a diffractive waveguide structure provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the diffractive waveguide includes a substrate 1 and a dielectric layer 2; a grating structure 4 is disposed on at least one side of the substrate 1, and the dielectric layer 2 is located on the side of the grating structure 4 away from the substrate 1; wherein, the refractive index of the substrate 1 is greater than 2, the absolute value of the difference between the refractive indices of the substrate 1 and the dielectric layer 2 is greater than or equal to 0.5, and the thickness of the dielectric layer 2 is greater than 3 μm.

[0018] Specifically, substrate 1 can be a glass substrate, but is not limited to it; other substrate materials used in diffractive waveguides are also within the scope of protection of this invention. Substrate 1 includes two surfaces arranged opposite each other, and at least one surface of substrate 1 is provided with a grating structure 4. Figure 1 Taking the example of a grating structure 4 being provided on one side surface of the substrate 1, the invention is not limited to this. In embodiments not shown in the present invention, grating structures 4 can be provided on both opposite sides of the substrate 1.

[0019] It is worth mentioning that, such as Figure 1 As shown in the embodiment of the present invention, a dielectric layer 2 can be disposed on at least one side of the substrate 1. The dielectric layer 2 is a continuous layer covering the surface of the substrate 1 on which the grating structure 4 is disposed, and also covering the grating structure 4 to protect the grating structure 4. The dielectric layer 2 can function as an edge adhesive with a protective film in related technologies. In this way, the side of the substrate 1 with the grating structure 4 is bonded to the continuous dielectric layer 2, greatly improving the fixing reliability of the diffractive waveguide. In addition, the thickness of the dielectric layer 2 can be set to 3μm or more to ensure the reliability of the dielectric layer 2 in protecting the grating structure 4. Compared with the 200μm thickness of the edge adhesive in the prior art, the thickness of the dielectric layer 2 in the present invention is greatly reduced, which is beneficial to reducing the thickness of the diffractive waveguide.

[0020] Furthermore, in this embodiment of the invention, by setting the substrate to have a large refractive index (greater than 2), the diffractive waveguide can achieve both large field-of-view transmission and monolithic full-color transmission, thereby improving the overall performance of the diffractive waveguide. Additionally, setting the absolute value of the difference between the refractive indices of the substrate and the dielectric layer to be greater than or equal to 0.5 is beneficial for improving the diffraction efficiency of the diffractive waveguide.

[0021] In this invention, the specific refractive indices of the substrate and dielectric layer are not limited. When the refractive indices of the substrate and dielectric layer change, the propagation paths of the light emitted from the optomechanical system within the diffractive waveguide may differ. When the propagation paths of the light emitted from the optomechanical system differ among the layers within the diffractive waveguide, the uniformity of the final emitted light may be affected. For example, the step size of light rays incident at different angles and / or light rays of different wavelengths entering the diffractive waveguide may differ, resulting in differences in energy at different coupling points and affecting the uniformity of display brightness. The refractive indices of the layers in the diffractive waveguide can be designed according to actual application requirements to adjust the light propagation path, thereby improving the uniformity of light emission, enhancing the display effect of the display device, and ensuring a better visual experience for the user.

[0022] In this embodiment of the invention, the material of the dielectric layer is not limited. For example, the dielectric layer may use the edge adhesive material in the prior art, but it is not limited thereto.

[0023] In this embodiment of the invention, a dielectric layer is provided in the diffractive waveguide. The dielectric layer protects the grating structure. Since the contact area between the dielectric layer and the substrate is large, a thin dielectric layer can achieve good protection and fixation. While ensuring the reliability of the diffractive waveguide, the thickness of the protective sheet is reduced, thereby reducing the weight of the display device. Furthermore, by designing the refractive index of the substrate and the refractive index difference between the substrate and the dielectric layer, the diffraction efficiency of the grating structure can be improved, enabling large field-of-view transmission and single-chip full-color transmission, thereby enhancing the overall performance of the diffractive waveguide.

[0024] Optionally, in some embodiments of the present invention, the grating structure can be integrally formed with the substrate, for example, the grating structure can be fabricated on the substrate by an etching process; when the grating structure is integrally formed with the substrate, the grating structure and the substrate are made of the same material, and the refractive index of the grating structure is the same as the refractive index of the substrate, and the absolute value of the difference between the refractive index of the grating structure and the dielectric layer is greater than or equal to 0.5.

[0025] In other embodiments of the present invention, the grating structure can be independent of the substrate. For example, an imprinting adhesive layer can be formed on at least one side of the substrate, and then the grating structure is formed in the imprinting adhesive layer using a nanoimprinting process. When the grating structure is independently disposed from the substrate, the material of the grating structure is different from the material of the substrate. In this case, the absolute value of the refractive index difference between the grating structure and the dielectric layer can be set to be greater than or equal to 0.5 to ensure the diffraction efficiency of the grating structure. That is, the absolute value of the refractive index difference between the imprinting adhesive layer and the dielectric layer is set to be greater than or equal to 0.5.

[0026] The present invention does not limit the refractive index design scheme for the substrate and dielectric layer; those skilled in the art can set it according to actual needs. Several optional refractive index design schemes for the inner film layer of the diffractive waveguide are described below.

[0027] Optional, you can continue to refer to Figure 1 The grating structure 4 includes a coupling grating 41, through which light enters the diffraction waveguide. The region where the coupling grating 41 is located is the coupling grating region. The outgoing light from the optomechanism is directed toward the coupling grating region, and then diffracts after passing through the coupling grating 41 and continues to propagate in the diffraction waveguide.

[0028] For example, such as Figure 1 As shown, in some embodiments, the refractive index of the dielectric layer 2 is... satisfy: , The maximum refractive index of dielectric layer 2 when all light rays undergo total internal reflection within substrate 1. Let be the minimum refractive index of dielectric layer 2 when all light rays exit from substrate 1; where,

[0029] ; Formula (1)

[0030] ; Formula (2)

[0031] The refractive index of air, The center wavelength of light, For the period of the coupling grating 41, The minimum incident angle of the light rays incident on the coupling grating 41. The maximum angle of the light rays incident on the coupling grating 41.

[0032] According to formula (1), based on the above parameters, the maximum refractive index of the dielectric layer 2 can be calculated when all rays of the same color (rays with the same center wavelength) emitted by the optical engine enter the substrate 1 through the coupling grating 41 and undergo total internal reflection within the substrate 1. That is, the maximum refractive index requirement satisfied by the dielectric layer 2 (i.e., the relatively optically less dense medium) when all rays entering the substrate 1 do not enter the dielectric layer 2 and only undergo total internal reflection at the interface between the substrate 1 and the dielectric layer 2. According to formula (2), the minimum refractive index requirement satisfied by the dielectric layer 2 when all rays entering the substrate 1 do not undergo total internal reflection at the interface between the substrate 1 and the dielectric layer 2, that is, when all rays enter the dielectric layer 2, can be calculated. It can be understood that the minimum refractive index of the dielectric layer 2 that allows all rays to exit from the substrate is the minimum refractive index of the dielectric layer 2. It should be greater than the maximum refractive index of the dielectric layer 2 that ensures total internal reflection of all light rays within the substrate. .

[0033] It is understood that total internal reflection only occurs when light travels from an optically denser medium to an optically less dense medium. Therefore, in one alternative embodiment, the refractive index of the dielectric layer 2 can be set. Greater than and less than This avoids total internal reflection of all light rays at the interface between substrate 1 and dielectric layer 2, allowing at least a portion of the light rays in substrate 1 to enter dielectric layer 2. The propagation step length and number of steps of the light rays entering dielectric layer 2 in the diffraction waveguide are increased, thereby improving the uniformity of the energy of the outgoing light rays.

[0034] Among them, such as Figure 1As shown, the light rays entering the diffractive waveguide may include a first portion 51 and a second portion 52. The transmission angle of the first portion of light rays within the substrate 1 is smaller than that of the second portion of light rays within the substrate 1. The transmission angle of the light rays within the substrate 1 can be understood as the diffraction angle of the light rays after passing through the coupling grating 41. The first portion 51 represents the portion of light rays with the smaller transmission angle among all the light rays entering the substrate 1; the second portion 52 represents the portion of light rays with the larger transmission angle among all the light rays entering the substrate 1. The incident angle of the first portion 51 when it enters the coupling grating 41 is smaller than that of the second portion 52 when it enters the coupling grating 41. Figure 1 Different thicknesses are used to distinguish different types of light.

[0035] It is understandable that the condition for total internal reflection at the interface between two media is also related to the incident angle of the light (the angle at which the light enters the dielectric layer 2, i.e., the transmission angle of the light in the substrate 1). When the incident angle is greater than or equal to the critical angle, total internal reflection can occur at the interface; otherwise, it will not. In other words, to a certain extent, light entering the dielectric layer 2 at a larger angle is more likely to undergo total internal reflection at the interface between the substrate 1 and the dielectric layer 2, while light entering the dielectric layer 2 at a smaller angle may enter the dielectric layer 2 and continue propagating. In this embodiment, the refractive index of the dielectric layer 2 can be set. lie in and In this configuration, the first portion of light 51 with a smaller transmission angle in substrate 1 enters the dielectric layer 2, while the second portion of light 52 with a larger transmission angle in substrate 1 undergoes total internal reflection within substrate 1. With this configuration, while the step length and number of steps for the long-step light (i.e., the second portion of light 52) ​​remain unchanged, the step length for the short-step light (i.e., the first portion of light 51) increases while the number of steps decreases, effectively improving the uniformity of light output.

[0036] It should be noted that, due to the different center wavelengths of light in practical applications... The period of the coupled grating 41 The minimum angle of incidence of light Maximum incident angle of light Since they are all different, the specific refractive index value of the dielectric layer 2 is not limited in the embodiments of the present invention.

[0037] For example, Figure 2 A schematic diagram of another diffractive waveguide structure provided in an embodiment of the present invention can be referred to. Figure 2 In other embodiments, the refractive index of dielectric layer 2 is... satisfy: ;in, The above formula (2) is still used for calculation.

[0038] Figure 2 In the illustrated embodiment, the light rays incident on the diffractive waveguide may still include the first portion ray 51 and the second portion ray 52 described above. This is achieved by adjusting the refractive index of the dielectric layer 2. The minimum refractive index of dielectric layer 2 All light rays within the substrate 1 (including the first part of light rays 51 and the second part of light rays 52) can enter the dielectric layer 2. The light rays entering the diffraction waveguide propagate simultaneously within the dielectric layer 2 and the substrate 1. The step length of all light rays becomes longer and the number of steps decreases, effectively improving uniformity.

[0039] For example, Figure 3 A schematic diagram of another diffractive waveguide provided in an embodiment of the present invention can be referred to. Figure 3 In some other embodiments, the refractive index of dielectric layer 2 is... ;in, The above formula (1) is still used for calculation.

[0040] By setting the refractive index of dielectric layer 2 to be less than This ensures that the refractive index difference between the dielectric layer 2 and the substrate 1 meets the requirements for total internal reflection. All light rays within the substrate 1 are still totally internally reflected at the interface between the substrate 1 and the dielectric layer 2, and the step size remains unchanged. In this configuration, the dielectric layer 2 only serves a fixing effect and does not modulate the light. When the technology is not yet mature, using the range of refractive index of the dielectric layer 2 can avoid the impact of low flatness or defects in the dielectric layer 2 and the protective layer 3.

[0041] Optional, Figure 4 A schematic diagram of another diffractive waveguide provided in an embodiment of the present invention can be referred to. Figure 4 In a possible embodiment, the diffractive waveguide further includes a protective layer 3, which is located on the side of the dielectric layer 2 facing away from the substrate 1. The substrate 1 and the protective layer 3 are fixed together by the dielectric layer 2. It should be noted that the fixing of the substrate 1 and the protective layer 3 by the dielectric layer 2 can be achieved by the dielectric layer 2 itself having adhesive properties, directly bonding the protective layer 3 to the substrate 1 through the dielectric layer 2; or by forming an adhesive layer on the surface of the dielectric layer 2, and then bonding the protective layer 3 through the adhesive layer; or by forming a ring of adhesive around the surface of the dielectric layer 2, and then bonding the protective layer 3 through the outer adhesive layer.

[0042] Specifically, as an optional embodiment, the diffractive waveguide may include a substrate 1, a dielectric layer 1, and a protective layer 3 stacked together. The dielectric layer 2 fills the space between the substrate 1 and the protective layer 3, thereby fixing the substrate 1 and the protective layer 2. Thus, the dielectric layer 2 and the protective layer 3 together protect the grating structure 4. By using two layers as the protective structure of the diffractive waveguide, the thickness of both the dielectric layer 2 and the protective layer 3 can be set to be relatively thin, or a very thin hardened coating can be used instead of the protective layer 3, further reducing the overall thickness of the diffractive waveguide. Furthermore, compared to using edge adhesive to fix the protective layer 3, in this embodiment, the thinner dielectric layer 2 can achieve the fixing effect of a thicker edge adhesive, making the diffractive waveguide both lightweight and reliable.

[0043] In this invention, the material of the protective layer is not limited. For example, the protective layer may use the material of the existing protective sheet, but it is not limited thereto.

[0044] Optionally, in some embodiments, the thickness of the dielectric layer is d1, where 3 μm < d1 < 200 μm; and the thickness of the protective layer is d2, where 0 μm < d2 < 500 μm.

[0045] A dielectric layer is filled between the substrate and the protective layer to fix the substrate and the protective layer. The thickness of both the dielectric layer and the protective layer is reduced to a certain extent. The thickness of the dielectric layer can be set in the range of 3~200μm, and the thickness of the protective layer can be set within 500μm.

[0046] Furthermore, in some embodiments, the thickness of the dielectric layer can be set to 10 μm and the thickness of the protective layer to 50 μm. Actual process data shows that when the dielectric layer thickness is around 10 μm, the fixing strength can be achieved as with an edge adhesive thickness of 200 μm. In addition, while ensuring the reliability of the diffractive waveguide, the thickness of the protective layer can be reduced to 50 μm, which greatly reduces the overall thickness of the diffractive waveguide. This not only reduces the weight of the display device but also meets the application requirements of more miniaturized display devices.

[0047] When a protective layer is incorporated into the diffractive waveguide, the refractive index of the protective layer can be designed according to actual requirements. For examples, please refer to... Figure 4 In some implementations, when the refractive index of dielectric layer 2 satisfies: At that time, the refractive index of protective layer 3 satisfy: .

[0048] Specifically, in Under these conditions, the refractive index of protective layer 3 can be further adjusted. The refractive index is greater than that of dielectric layer 2. This ensures that the first portion of light 51 entering the dielectric layer 2 does not undergo total internal reflection at the interface between the dielectric layer 2 and the protective layer 3, allowing all light entering the dielectric layer 2 to be directed towards the protective layer 3. With the step length and number of steps for long-step light remaining constant, the step length for short-step light can be further increased and the number of steps for short-step light decreased, thereby further improving the uniformity of light output.

[0049] For example, Figure 5 This is a schematic diagram of another diffractive waveguide structure provided in an embodiment of the present invention, with reference to... Figure 5 When the refractive index of dielectric layer 2 satisfies: In other embodiments, the refractive index of the protective layer 3 is... satisfy: .

[0050] Specifically, the first portion of light 51 may include a third portion of light 53 and a fourth portion of light 54, wherein the transmission step size of the third portion of light 53 in the dielectric layer 2 is smaller than the transmission step size of the fourth portion of light 54 in the dielectric layer 2. In this embodiment, in Under these conditions, the refractive index of protective layer 3 can be further increased. Settings and Between these layers, the first portion of light rays 51 with a smaller transmission angle within substrate 1 can enter dielectric layer 2. A portion of light rays with a short step length (which can also be understood as light rays with a smaller transmission angle within dielectric layer 2) within dielectric layer 2 can enter protective layer 3. A portion of light rays with a long step length (which can also be understood as light rays with a larger transmission angle within dielectric layer 2) within dielectric layer 2 undergoes total internal reflection. That is, the longer step length light rays (i.e., the second portion of light rays 52) within substrate 1 are transmitted only within substrate 1, with the step length and number of steps remaining unchanged. The medium step length light rays (i.e., the fourth portion of light rays 54) within substrate 1 can be transmitted simultaneously within substrate 1 and dielectric layer 2, with the step length of the medium step length light increasing to a certain extent and the number of steps decreasing to a certain extent. The shorter step length light rays (i.e., the third portion of light rays 53) within substrate 1 can be transmitted simultaneously within substrate 1, dielectric layer 2, and protective layer 3, resulting in a significant increase in the step length of the short step length light rays and a significant decrease in the number of steps, thereby making the number of steps for light rays of different step lengths closer together and further improving the uniformity of light output.

[0051] For example, Figure 6 A schematic diagram of another diffractive waveguide provided in an embodiment of the present invention can be referred to. Figure 6 In some other embodiments, the refractive index of dielectric layer 2 satisfies: At that time, the refractive index of protective layer 3 satisfy: .

[0052] Specifically, in Under these conditions, the refractive index of protective layer 3 can be further adjusted. Greater than This allows all light rays within the dielectric layer 2 (including the first part of light rays 51 and the second part of light rays 52) to enter the protective layer 3, further increasing the step length and reducing the number of steps for all light rays, effectively improving uniformity.

[0053] Continue to refer to Figure 5 The grating structure 4 also includes an output grating 42. The output grating 42 and the input grating 41 are arranged along the plane of the substrate 1. Light rays in the diffracting waveguide are emitted through the output grating 42. The output grating 42 includes a first output point 42a and a second output point 42b, which are two edge output points corresponding to the same observation point. Figure 5 As shown, taking AR glasses as an example, ab represents the visible range of the lens for the diffracted waveguide image, meaning that every point between ab can completely see the image; points a and b are the observation points mentioned above. The first coupling point 42a may include the first sub-coupling point 42a1 and the second sub-coupling point 42a2, and the second coupling point 42b may include the third sub-coupling point 42b1 and the fourth sub-coupling point 42b2. The first sub-coupling point 42a1 and the third sub-coupling point 42b1 can be regarded as two edge coupling points corresponding to point a, and the second sub-coupling point 42a2 and the fourth sub-coupling point 42b2 can be regarded as two edge coupling points corresponding to point b. ab represents the visible range of the lens for the image, meaning that every point between ab can completely see the image. Light rays with the maximum transmission angle within the substrate 1 are emitted through the first sub-coupling point 42a1 and the second sub-coupling point 42a2, while light rays with the minimum transmission angle within the substrate 1 are emitted through the third sub-coupling point 42b1 and the fourth sub-coupling point 42b2.

[0054] The energy of the light ray emitted from the elution point is calculated using the following formula:

[0055] Formula (3)

[0056] Formula (4)

[0057] Formula (5)

[0058] Formula (6)

[0059] Formula (7)

[0060] (Formula 8)

[0061] Formula (9)

[0062] in, The refractive index of substrate 1, The minimum transmission angle of light within substrate 1. The maximum angle of light transmission within substrate 1. The angle at which light can enter the dielectric layer 2 propagates in the substrate 1. The angle at which light rays can enter dielectric layer 2 propagate within dielectric layer 2. The angle at which light rays can enter the protective layer 3 are transmitted within the protective layer 3; The step size of the light beam. For a substrate thickness of 1, The thickness of dielectric layer 2, For the thickness of protective layer 3, The number of light step sizes in the coupled grating 41 The diameter of the coupling grating 41, The energy of the light entering substrate 1. The energy of the light beam as it leaves the coupling grating 41. The light extraction efficiency at the coupling grating 42 is given.

[0063] Based on the above formulas (3) to (6), the transmission angle of light rays that can enter the dielectric layer 2 in the dielectric layer 2 can be calculated. And the transmission angle of light that can enter the protective layer 3 within the protective layer 3. Thus, the light output energy of each coupling point can be calculated according to formulas (7) to (9).

[0064] Actual tests show that when the refractive index of dielectric layer 2... and the refractive index of protective layer 3 When the refractive index requirements of any of the above embodiments are met, the difference in light output energy between the first sub-outlet point 42a1 and the third sub-outlet point 42b1 corresponding to point a, and the difference in light output energy between the second sub-outlet point 42a2 and the fourth sub-outlet point 42b2 corresponding to point b can be reduced, and the uniformity of light output energy between points a and b is improved, thereby improving the viewing effect.

[0065] Optionally, assume that the emitted light energy at the first coupling point 42a is The emitted light energy at the second coupling point 42 is , can be set This ensures uniform light output.

[0066] The above embodiments primarily aim to design the refractive index of each film layer in the diffractive waveguide by modulating the propagation paths of light rays of the same color incident at different angles. In the following embodiments, the refractive index of each film layer can be designed to modulate the propagation paths of light rays of different colors incident at the same angle into the diffractive waveguide.

[0067] For example, in a possible embodiment, the grating structure still includes a coupling grating, through which light enters the diffraction waveguide. The diffraction waveguide also includes a protective layer located on the side of the dielectric layer facing away from the substrate, and the substrate and the protective layer are fixed together by the dielectric layer. The light entering the diffraction waveguide includes a first color light and a second color light, the center wavelength of the first color light being [missing information]. The center wavelength of the second color light is , Among the substrate, dielectric layer, and protective layer, any two opposing layers through which light passes in sequence are designated as the first and second layers; the refractive index of the first layer... satisfy: , Let be the maximum refractive index of the second film when the first color light is totally internally reflected within the first film at all incident angles. Let be the minimum refractive index of the first film layer when the second color light is totally internally reflected within the first film layer at all incident angles; where

[0068] ; Formula (10)

[0069] ; Formula (11)

[0070] The refractive index of the second film layer satisfy: , Let be the maximum refractive index of the second-color light layer when it undergoes total internal reflection within the first layer at all incident angles; where .

[0071] ; Formula (12)

[0072] The refractive index of air, The period of the coupled grating, The minimum incident angle of the light rays incident on the coupling grating. The maximum angle of the light rays incident on the coupling grating.

[0073] Specifically, different colors of light have different center wavelengths. The first color light and the second color light can refer to any two different colors of light emitted by the optical engine. The first film and the second film do not refer to the fixed film in the diffractive waveguide. If the light propagates in the substrate and the dielectric layer, then the first film represents the substrate and the second film represents the dielectric layer; if the light propagates in the substrate, the dielectric layer, and the protective layer, then the first film can represent the substrate and the second film can represent the dielectric layer, or the first film can represent the dielectric layer and the second film can represent the protective layer.

[0074] In this embodiment, the maximum refractive index requirement satisfied by the second film layer when the first color light with a longer wavelength enters the first film layer and undergoes total internal reflection in the first film layer can be calculated according to formula (10). The minimum refractive index requirement satisfied by the first film layer when the second color light with a shorter wavelength enters the first film layer and undergoes total internal reflection in the first film layer can be calculated according to formula (11). The maximum refractive index requirement satisfied by the second film layer when the second color light with a shorter wavelength enters the first film layer and undergoes total internal reflection in the first film layer can be calculated according to formula (12).

[0075] The refractive index of the first film layer can be set. lie in and Between, the refractive index of the second film layer Greater than Thus, the first color light undergoes total internal reflection in the first film layer and does not enter the second film layer, meaning the first color light only propagates in the first film layer; the second color light can enter the second film layer, which is equivalent to increasing the propagation depth of the second color light in the diffraction waveguide, that is, the distance in the thickness direction of the diffraction waveguide. This results in a larger propagation step size for the second color light with a shorter wavelength and a smaller propagation step size for the first color light with a longer wavelength, thereby making the step sizes of different colors of light tend to be the same in the whole lens and improving uniformity.

[0076] For example, in one specific embodiment, the different colored light rays entering the diffractive waveguide include red light, green light, and blue light, and the light rays generated by the optomechanism include red light, green light, and blue light, with the center wavelength of the red light being [missing information]. The center wavelength of green light is The center wavelength of blue light is ,in, .

[0077] Formula (10) can be transformed into:

[0078] ; Formula (13)

[0079] ; Formula (14)

[0080] ; Formula (15)

[0081] Formula (11) can be transformed into:

[0082] ; Formula (16)

[0083] ; Formula (17)

[0084] ; Formula (18)

[0085] is the maximum refractive index of an optically less dense medium when red light undergoes total internal reflection in all incident angles; Let be the minimum refractive index of the optically dense medium when red light undergoes total internal reflection in all incident angles. The maximum refractive index of an optically less dense medium is given when green light undergoes total internal reflection in all incident angles. Let be the minimum refractive index of the optically dense medium when green light undergoes total internal reflection within the medium at all incident angles; The maximum refractive index of an optically less dense medium is given when blue light undergoes total internal reflection in all incident angles. It is the minimum refractive index of an optically dense medium when blue light is totally reflected in the medium at all incident angles.

[0086] The refractive index of the substrate can be set. satisfy: refractive index of dielectric layer satisfy: The refractive index of the protective layer satisfy: This allows red light to propagate only in the substrate, green light to propagate in both the substrate and the dielectric layer, and blue light to propagate in the substrate, the dielectric layer, and the protective layer.

[0087] For full-color waveguides, the refractive indices of the substrate, dielectric layer, and protective layer are set according to the above conditions so that the three colors of light can propagate through different film layers in the diffractive waveguide, that is, the propagation distances in the thickness direction of the diffractive waveguide are different, so that the step size of the three colors of light in the waveguide tends to be consistent, thus improving uniformity.

[0088] The following describes two specific embodiments provided by the present invention.

[0089] Example 1

[0090] In this embodiment, substrate refractive index The thickness is 2.0, and the substrate thickness is... The thickness is 500 μm, and the refractive index of the dielectric layer is... The dielectric layer thickness is 1.5. The thickness is 250 μm, and the refractive index of the protective layer is... The thickness is 2.0, and the protective layer thickness is... 500 μm, coupled grating period The maximum angle of light incident on the coupling grating is 350nm. =15°, the minimum angle of light incident on the coupling grating. =15°, center wavelength of light =532nm.

[0091] According to the above formulas (3) to (9), the maximum and minimum transmission angles of light entering the substrate through the coupling grating are respectively: =60.383°, =38.051°;

[0092] The minimum transmission angle Light rays can enter the dielectric layer, and the angle at which they propagate within the dielectric layer is... =55.268°.

[0093] by =100%, =90% calculation was performed. The data of the edge coupling points at points a and b corresponding to the diffracting waveguide with and without a dielectric layer are shown in Table 1 below; the division of coupling points can be referred to Figure 1 The first sub-coupling point 42a1 and the third sub-coupling point 42b1 can be regarded as two edge coupling points corresponding to point a, and the second sub-coupling point 42a2 and the fourth sub-coupling point 42b2 can be regarded as two edge coupling points corresponding to point b.

[0094] Referring to Table 1, it can be seen that the uniformity of the diffractive waveguide with the dielectric layer is improved at both points a and b: the difference at point a is reduced from 47.83% to 90.00% to 65.61% to 90.00%; the difference at point b is reduced from 1.64% to 22.88% to 12.16% to 22.88%.

[0095] Table 1

[0096]

[0097] Example 2

[0098] In this embodiment, , substrate refractive index The thickness is 2.0, and the substrate thickness is... The thickness is 500 μm, and the refractive index of the dielectric layer is... The dielectric layer thickness is 1.7. The thickness is 200 μm, and the refractive index of the protective layer is [missing information]. The thickness of the protective layer is 1.4. 200μm, coupled grating period The maximum angle of light incident on the coupling grating is 350nm. =15°, the midpoint of the light rays incident on the coupling grating The minimum angle of light incident on the coupling grating at 0° =-15°, center wavelength of light =532nm.

[0099] According to the above formulas (3) to (9), the maximum transmission angle, intermediate transmission angle, and minimum transmission angle of the light entering the substrate through the coupling grating can be calculated as follows: =60.383°, =47.98° =38.051°.

[0100] The intermediate transmission angle and minimum transmission angle Light rays can penetrate the dielectric layer and propagate; the angle at which they propagate within the dielectric layer is... =60.93°, =46.48°;

[0101] in The light can then penetrate the protective layer and propagate further; the angle at which it propagates within the protective layer is... =61.71°.

[0102] by =100%, =90% calculation was performed. The data of the edge coupling points at points a and b for diffracting waveguides with and without dielectric layers are shown in Table 2 below; the division of coupling points can be referred to Figure 5 The first sub-coupling point 42a1 and the third sub-coupling point 42b1 can be regarded as two edge coupling points corresponding to point a, and the second sub-coupling point 42a2 and the fourth sub-coupling point 42b2 can be regarded as two edge coupling points corresponding to point b.

[0103] As can be seen from Table 2, the uniformity of the diffractive waveguide with the dielectric layer is improved at both points a and b: the difference at point a decreases from 47.83% to 90.00% to 72.90% to 90.00%; the difference at point b decreases from 1.64% to 22.88% to 20.59% to 22.88%.

[0104] Table 2

[0105]

[0106] Based on the same concept, embodiments of the present invention also provide a display device, including the diffractive waveguide provided in any embodiment of the present invention, possessing all the technical features and corresponding beneficial effects of the diffractive waveguide provided in any embodiment of the present invention. This display device can be any AR display device, such as AR glasses or an AR head-up display device, but is not limited thereto.

[0107] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A diffractive optical waveguide, characterized in that, Includes the substrate and dielectric layer; A grating structure is provided on at least one side of the substrate, and the dielectric layer is located on the side of the grating structure opposite to the substrate; Wherein, the refractive index of the substrate is greater than 2, the absolute value of the difference between the refractive indices of the substrate and the dielectric layer is greater than or equal to 0.5, and the thickness of the dielectric layer is greater than 3 μm; The grating structure includes a coupling grating, through which light enters the diffractive waveguide; The refractive index of the dielectric layer satisfy: , The maximum refractive index of the dielectric layer when all light rays are totally internally reflected within the substrate. The minimum refractive index of the dielectric layer when all light rays exit from the substrate; wherein, ； ； The refractive index of air, The center wavelength of light, The period of the coupled grating, The minimum incident angle of the light rays incident on the coupled grating. The maximum angle of the light rays incident on the coupled grating; The diffractive waveguide further includes a protective layer, which is located on the side of the dielectric layer away from the substrate, and the substrate and the protective layer are fixed together by the dielectric layer. The refractive index of the protective layer satisfy: .

2. The diffractive waveguide according to claim 1, characterized in that, The material of the grating structure is different from the material of the substrate, and the absolute value of the refractive index difference between the grating structure and the dielectric layer is greater than or equal to 0.

5.

3. A diffractive optical waveguide, characterized in that, Includes the substrate and dielectric layer; A grating structure is provided on at least one side of the substrate, and the dielectric layer is located on the side of the grating structure opposite to the substrate; Wherein, the refractive index of the substrate is greater than 2, the absolute value of the difference between the refractive indices of the substrate and the dielectric layer is greater than or equal to 0.5, and the thickness of the dielectric layer is greater than 3 μm; The grating structure includes a coupling grating through which light enters the diffractive waveguide. The diffractive waveguide also includes a protective layer located on the side of the dielectric layer facing away from the substrate. The substrate and the protective layer are fixed together by the dielectric layer. The light entering the diffractive waveguide includes red, green, and blue light, with the center wavelength of the red light being [missing information]. The center wavelength of green light is The center wavelength of blue light is , ; The refractive index of the substrate satisfy: The refractive index of the dielectric layer satisfy: The refractive index of the protective layer satisfy: This allows red light to propagate only in the substrate, green light to propagate in the substrate and dielectric layer, and blue light to propagate in the substrate, dielectric layer, and protective layer. is the maximum refractive index of an optically less dense medium when red light undergoes total internal reflection in all incident angles; Let be the minimum refractive index of the optically dense medium when red light undergoes total internal reflection in all incident angles. The maximum refractive index of an optically less dense medium is given when green light undergoes total internal reflection in all incident angles. Let be the minimum refractive index of the optically dense medium when green light undergoes total internal reflection within the medium at all incident angles; The maximum refractive index of an optically less dense medium is given when blue light undergoes total internal reflection in all incident angles. The minimum refractive index of an optically dense medium is given when blue light undergoes total internal reflection at all incident angles. ； ； ； ； ； ； The refractive index of air, The period of the coupled grating, The minimum incident angle of the light rays incident on the coupled grating. The maximum angle of the light rays incident on the coupled grating.

4. A display device, characterized in that, Including the diffractive waveguide as described in any one of claims 1 to 3.

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