A composite diffractive optical waveguide lens

Abstract

The present application relates to a kind of composite diffraction optical waveguide glasses, it includes at least two waveguide substrates of laminated arrangement, the in-coupling grating being arranged in one of waveguide substrate surface, and the out-coupling grating being arranged between two waveguide substrates, the refractive index of the at least two waveguide substrates is same or decreasing along the direction away from incident light source, the in-coupling grating is coupled into the at least two waveguide substrates by incident light beam, after total reflection of the light beam coupled into the at least two waveguide substrates, by the out-coupling grating, light beam from different waveguide substrates is respectively coupled out with different diffraction orders.The present application has the effect that the exit pupil continuity is improved and rainbow stripe effect is indirectly inhibited, and the transmittance of grating area can be significantly improved by 3-14%.

Description

Technical Field

[0001] This invention relates to the technical field of optical elements, and in particular to a composite diffractive waveguide lens. Background Technology

[0002] Augmented reality (AR) glasses, with their immersive interaction and near-eye display advantages, are widely regarded as ideal terminal carriers for artificial intelligence applications. Currently, most mainstream AR glasses display modules employ diffractive waveguide solutions, which use grating structures to couple, expand, and couple light beams, offering advantages such as good mass production performance and high yield. A typical diffractive waveguide lens consists of a substrate (glass or resin, etc.) and surface-processed gratings (such as surface-embossed gratings). Parameters such as the period and duty cycle of the coupling grating directly affect the exit pupil continuity, display uniformity, and optical transmittance. First, there is an inherent constraint between exit pupil continuity and the rainbow effect, based on the step size S = 2 × t × tan(θ) and the diffraction angle θ = arcsin(mλ / d), where t is the waveguide thickness, m is the diffraction order, d is the grating period, and λ is the incident light wavelength. Since the exit pupil continuity W is determined by the difference between the step size and the spot size, increasing the grating period can shorten the step size and improve the exit pupil continuity W ≤ 4mm. However, increasing the period will significantly exacerbate the rainbow effect (i.e., color separation caused by different wavelengths of light at different angles), severely affecting visual perception. Second, the transmittance of traditional diffractive waveguides in the grating region is relatively low, typically only 75-93%, resulting in poor ambient light transmittance and affecting the see-through effect of AR glasses. To improve exit pupil continuity and increase transmittance, existing technologies have proposed various improvement schemes.

[0003] Chinese patent CN120652674A discloses a method for optimizing the exit pupil discontinuity of an optical waveguide system. The method includes: Step 1: Establishing an optical waveguide-exit pupil mapping model based on the optical waveguide system; Step 2: Calculating the reflection propagation path of the light beam inside the waveguide based on the optical waveguide-exit pupil mapping model, and extracting the exit pupil coordinates based on the intersection point of the light beam and the waveguide plane in the reflection propagation path; Step 3: Constructing a quantitative evaluation index for exit pupil discontinuity based on the exit pupil coordinates; Step 4: Constructing a discontinuity optimization algorithm based on the quantitative evaluation index for exit pupil discontinuity, solving the discontinuity optimization algorithm, and obtaining the optimized structural parameters of the optical waveguide system. However, this method only optimizes the exit pupil continuity by adjusting parameters such as the grating period, neglecting the problem of rainbow ripple deterioration caused by increasing the period.

[0004] Chinese patent CN220730471U discloses a diffractive waveguide, comprising a waveguide substrate and a grating structure located on one side of the waveguide substrate; the grating structure includes at least two layers in a direction perpendicular to the plane of the waveguide substrate; the refractive indices of the different layers in the grating structure decrease sequentially in the direction away from the plane of the waveguide substrate. While the aforementioned diffractive waveguide uses a layered grating structure to improve transmittance, it suffers from difficulties in manufacturing and complex processing.

[0005] Chinese Patent CN118377081B discloses a light guide device, including a substrate and a first diffraction structure disposed on the substrate. The first diffraction structure includes a first grating; the first grating includes a plurality of first grating units, which are arranged at intervals of a first period P1 along a first vector direction u1 and at intervals of a second period P2 along a second vector direction u2; the light guide device further includes a second diffraction structure disposed on the substrate; the second diffraction structure is used to couple an incident light beam into the substrate; the substrate is used to propagate the incident light beam from the second diffraction structure through total internal reflection to the first diffraction structure; the first diffraction structure is used to couple out the light beam, and the first diffraction structure is composed of the first grating, which is an improved one-dimensional grating with a period of P and a vector direction of u; the first grating satisfies the following relationship: 2π×u IC / P IC +2π×u / P+2π×u² / P²=0; where P IC For the grating period of the second diffraction structure, u IC P represents the vector direction of the second diffraction structure. IC and u IC The grating vector information that makes up the second diffraction structure. The above-mentioned light guide device improves the transmittance of the grating region by dividing the one-dimensional grating into a two-dimensional grating, but it has problems such as high difficulty in manufacturing and complex processing. Summary of the Invention

[0006] The present invention addresses the aforementioned shortcomings of existing technologies by providing a composite diffractive waveguide lens. This solution overcomes the problems of existing diffractive waveguides, such as difficulty in simultaneously achieving exit pupil continuity and rainbow effect suppression, low transmittance in the grating region, complex manufacturing processes, and lens thickness. It employs a composite structure of waveguide substrate-coupled grating-waveguide substrate. Without reducing overall coupling efficiency, it increases beam density by introducing multiple coupled optical paths, thereby improving exit pupil continuity and indirectly suppressing rainbow effect. This significantly increases the transmittance of the grating region by 3-14%. Furthermore, this structure eliminates the need for a traditional cover plate, effectively reducing the overall weight and thickness of the lens, enabling a lightweight and thin design. The manufacturing process is compatible with existing wafer-level processing technologies, offering the advantage of easy mass production.

[0007] The above-mentioned objective of this invention is achieved through the following technical solutions: A composite diffractive waveguide lens includes at least two waveguide substrates stacked together, an insertion grating disposed on the surface of one of the waveguide substrates, and an exit grating disposed between the two waveguide substrates. The refractive indices of the at least two waveguide substrates are the same or decrease in the direction away from the incident light source. The insertion grating couples the incident light beam into the at least two waveguide substrates. After total internal reflection in the at least two waveguide substrates, the exit grating couples the light beams from the different waveguide substrates out at different diffraction orders.

[0008] Furthermore, the at least two waveguide substrates are configured as a first substrate and a second substrate, the refractive index of the first substrate exceeds the refractive index of the second substrate, the coupling grating is a reflective grating, the coupling grating is disposed on the surface of the first substrate or the second substrate away from the incident light source, and the coupling grating is disposed between the first substrate and the second substrate.

[0009] Furthermore, the at least two waveguide substrates are configured as a first substrate and a second substrate, the refractive index of the first substrate exceeds the refractive index of the second substrate, the coupling grating is a transmission grating, the coupling grating is disposed on the surface of the first substrate or the second substrate near the incident light source, and the coupling grating is disposed between the first substrate and the second substrate.

[0010] Furthermore, the output grating is configured as a one-dimensional straight grating, a one-dimensional blazed grating, a one-dimensional tilted grating, or a one-dimensional gradient grating, and a bend grating is selectively provided on the surface of one of the waveguide substrates. The bend grating is used to receive the light beam coupled into the input grating and guide the light beam to the output grating region.

[0011] Furthermore, the coupled grating is configured as a two-dimensional straight grating, a two-dimensional blazed grating, a two-dimensional tilted grating, or a two-dimensional gradient grating, and the coupled grating is used for two-dimensional pupil expansion.

[0012] Furthermore, the materials of the at least two waveguide substrates are each independently optical glass, optical resin, lithium niobate, or silicon carbide.

[0013] Furthermore, the thickness of each of the at least two waveguide substrates is independently 0.10~1.0 mm.

[0014] Furthermore, the materials of the coupling-in grating and the coupling-out grating are each independently optical glass, optical resin, lithium niobate, silicon carbide, titanium dioxide, or silicon nitride.

[0015] Furthermore, the structural parameters of the coupled grating satisfy at least one of the following conditions: The grating period is 250~400nm; The grating height is 30~250nm; Duty cycle is 20-80%.

[0016] Furthermore, the structural parameters of the coupling grating satisfy at least one of the following conditions: The grating period is 250~400nm; The grating height is 30~250nm; Duty cycle is 20-80%.

[0017] In summary, the beneficial technical effects of the present invention are as follows: 1. Since the present invention uses at least two waveguide substrates stacked together and places the coupling grating between two of the waveguide substrates, the light beam can propagate in different substrates and be coupled out through the coupling grating in a variety of different diffraction orders. This can increase the number of coupling optical paths and increase the beam density without reducing the total coupling efficiency, and ultimately achieve the technical effect of improving the continuity of the exit pupil and indirectly suppressing the rainbow effect. 2. In this invention, the preferred configuration is as follows: the refractive indices of the two waveguide substrates are the same or decrease along the direction away from the incident light source, and the coupling grating is set as a one-dimensional grating or a two-dimensional grating; through the optimized configuration of the multi-substrate structure and the interface grating, the diffraction loss of visible light in the grating area can be effectively reduced, while eliminating the traditional cover plate structure, which can increase the transmittance of the grating area by 3.3~14% compared with the traditional structure, and achieve a reduction in the overall thickness and weight of the lens; 3. The lens structure provided by the present invention arranges the coupling grating on the surface of one of the waveguide substrates and the coupling grating between the two substrates. The bonding or adhesive bonding process is used to achieve the bonding and assembly of the multi-layer substrates. It is compatible with existing wafer-level grating processing and cutting technology, and has the comprehensive advantages of simple manufacturing process, easy mass production, and applicability to both one-dimensional and two-dimensional pupil expansion scenarios. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the composite diffractive waveguide lens of Embodiment 1 of the present invention.

[0019] Figure 2 This is a schematic diagram of the composite diffractive waveguide lens of Embodiment 3 of the present invention.

[0020] Figure 3 This is a schematic diagram of the structure of the composite diffractive waveguide lens in Embodiment 5 of the present invention.

[0021] Figure 4 This is a schematic diagram of the structure of the composite diffractive waveguide lens of Embodiment 6 of the present invention.

[0022] Figure 5This is a schematic diagram of the structure of the composite diffractive waveguide lens in Embodiment 7 of the present invention.

[0023] Figure 6 This is a schematic diagram of the composite diffractive waveguide lens of Embodiment 8 of the present invention.

[0024] Figure 7 This is a schematic diagram of the composite diffractive waveguide lens of Embodiment 9 of the present invention.

[0025] Figure 8 This is a schematic diagram of the structure of the composite diffractive waveguide lens of Embodiment 10 of the present invention.

[0026] Figure 9 This is a schematic diagram of the composite diffractive waveguide lens of Comparative Example 1 of the present invention.

[0027] Figure 10 This is a schematic diagram of the composite diffractive waveguide lens of Comparative Example 2 of the present invention.

[0028] Figure 11 This is a schematic diagram of the composite diffractive waveguide lens of Comparative Example 3 of the present invention.

[0029] Figure 12 This is a schematic diagram of the composite diffractive waveguide lens of Comparative Example 4 of the present invention.

[0030] Figure 13 This is a schematic diagram of the composite diffractive waveguide lens of Embodiment 1 and Comparative Example 1 of the present invention.

[0031] Figure 14 This is a schematic diagram of the composite diffractive waveguide lens of Embodiment 3 and Comparative Example 5 of the present invention.

[0032] In the figure, 1 is the waveguide substrate; 11 is the first substrate; 12 is the second substrate; 2 is the coupling grating; and 3 is the coupling grating. Detailed Implementation

[0033] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Example

[0034] Example 1: Refer to Figure 1This invention discloses a composite diffractive waveguide lens, comprising at least two waveguide substrates 1 stacked together, a coupling grating 2 disposed on the surface of one of the waveguide substrates 1, and a coupling grating 3 disposed between the two waveguide substrates 1. The refractive indices of the waveguide substrates 1 are the same or decrease in the direction away from the incident light source. The coupling grating 2 couples the incident light beam into the waveguide substrates 1. After total internal reflection in the waveguide substrates 1, the coupling grating 3 couples the light beams from different waveguide substrates 1 out at different diffraction orders.

[0035] The fabrication process of the composite diffractive waveguide lens is as follows: after wafer-level grating processing, substrate cleaning and spin coating of imprinted adhesive are performed in sequence. The interface bonding of the first substrate 11 and the second substrate 12 is achieved through bonding process. The bonding is completed by pressure holding and UV curing (a resin impregnation hardening process can be added according to application requirements to improve mechanical strength). Subsequently, an anti-reflection film (AR film) is prepared. Finally, the composite diffractive waveguide lens is obtained by precision cutting.

[0036] Compared to conventional waveguide lenses, this method offers more coupling paths while maintaining almost the same total output energy. This means a reduction in the grating period 'd', which decreases the impact of rainbow patterns and improves exit pupil continuity. Furthermore, it enhances the transmittance of the diffractive waveguide in the grating structure region and, by eliminating the cover, effectively reduces the lens's weight and thickness. Notably, this method is applicable not only to one-dimensional and two-dimensional pupil expansion but also to EPE and coupling gratings. We also provide different fabrication processes tailored to different substrate materials. For homogeneous rigid substrates such as glass, lithium niobate, and silicon carbide, a bonding process is used to obtain composite diffractive waveguide lenses; for heterogeneous or non-rigid substrates such as glass and resin, a cementing process is used to obtain composite diffractive waveguide lenses.

[0037] Specifically, in this embodiment, the composite diffractive waveguide lens includes, The first substrate 11 is arranged close to the incident light source, and is made of optical resin with n=1.71 and a thickness of 0.35mm; The second substrate 12 is stacked on the surface of the first substrate 11 facing away from the incident light source, and is made of optical resin with n=1.71 and has a thickness of 0.35mm. The coupling grating 2 is configured as a one-dimensional reflective straight grating and is disposed on the surface of the second substrate 12 away from the incident light source. It is made of optical resin with n=1.71, has a grating period of 410nm, a grating height of 61.8nm, and a duty cycle of 40.5%. The coupling grating 3 is configured as a one-dimensional transmission straight grating and is disposed between the first substrate 11 and the second substrate 12. It is made of optical resin with n=1.71, the grating period is 336nm, the grating height is 40nm, and the duty cycle is 55%.

[0038] Example 2: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 1 is that the coupling grating 3 is a one-dimensional reflective straight grating.

[0039] Example 3: Reference Figure 2 This invention discloses a composite diffractive waveguide lens, comprising at least two waveguide substrates 1 stacked together, a coupling grating 2 disposed on the surface of one of the waveguide substrates 1, and a coupling grating 3 disposed between the two waveguide substrates 1. The refractive indices of the waveguide substrates 1 are the same or decrease in the direction away from the incident light source. The coupling grating 2 couples the incident light beam into the waveguide substrates 1. After total internal reflection in the waveguide substrates 1, the coupling grating 3 couples the light beams from different waveguide substrates 1 out at different diffraction orders.

[0040] The fabrication process of the composite diffractive waveguide lens is as follows: First, two pieces of glass are cut into lenses, and then surface tempering and deep tempering are completed respectively. After wafer-level high-precision grating processing is completed on the surface-tempered glass substrate, the lens is cut. The first substrate 11 after cutting is firmly bonded to another homogeneous hard second substrate 12 through a bonding process. Then, the grating is locally coated with metal (as required by the grating process) and an anti-reflection film is prepared to obtain the composite diffractive waveguide lens.

[0041] Specifically, in this embodiment, the composite diffractive waveguide lens includes, The first substrate 11 is arranged close to the incident light source, and is made of optical glass with n=2.00 and a thickness of 0.35mm; The second substrate 12 is stacked on the surface of the first substrate 11 facing away from the incident light source, and is made of optical glass with n=2.00 and a thickness of 0.35mm. The coupling grating 2 is configured as a one-dimensional reflective straight grating and is disposed on the surface of the second substrate 12 away from the incident light source. The material is titanium dioxide with n=2.40, the grating period is 385nm, the grating height is 40nm, and the duty cycle is 48%. The coupling grating 3 is configured as a one-dimensional transmission straight grating and is disposed between the first substrate 11 and the second substrate 12. It is made of titanium dioxide with n=2.40, the grating period is 352nm, the grating height is 35nm, and the duty cycle is 60%.

[0042] Example 4: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 3 is that the coupling grating 3 is a one-dimensional transmission straight grating.

[0043] Example 5: Refer to Figure 3 This invention discloses a composite diffractive waveguide lens, which differs from Embodiment 1 in that the coupling grating 2 is configured as a one-dimensional transmission straight grating and is disposed on the surface of the first substrate 11 near the incident light source.

[0044] Example 6: Refer to Figure 4 This invention discloses a composite diffractive waveguide lens, which differs from Embodiment 5 in that the coupling grating 3 is a one-dimensional reflective straight grating.

[0045] Example 7: Refer to Figure 5 This invention discloses a composite diffractive waveguide lens, which differs from Embodiment 1 in that the coupling grating 2 is configured as a one-dimensional reflective straight grating and is disposed on the surface of the first substrate 11 away from the incident light source, that is, between the first substrate 11 and the second substrate 12.

[0046] Example 8: Refer to Figure 6 This is a composite diffractive waveguide lens disclosed in this invention. The difference between this lens and Example 7 is that the coupling grating 3 is a one-dimensional reflective straight grating.

[0047] Example 9: Refer to Figure 7 This invention discloses a composite diffractive waveguide lens, which differs from Embodiment 1 in that the coupling grating 2 is configured as a one-dimensional transmission straight grating and is disposed on the surface of the second substrate 12 near the incident light source, that is, between the first substrate 11 and the second substrate 12.

[0048] Example 10: Refer to Figure 8 This is a composite diffractive waveguide lens disclosed in this invention. The difference between this lens and Example 9 is that the coupling grating 3 is a one-dimensional reflective straight grating.

[0049] Example 11: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 1 is that the output grating 3 is set as a one-dimensional tilted grating, and a turning grating (not shown in the figure) is also provided between the first substrate 11 and the second substrate 12. The turning grating is used to receive the light beam coupled into the input grating 2 and guide the light beam to the region of the output grating 3.

[0050] Example 12: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 1 is that the coupling grating 3 is set as a two-dimensional blazed grating and used for two-dimensional pupil expansion.

[0051] Example 13: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 1 is that the first substrate 11 is made of silicon carbide with n=2.70 and the second substrate 12 is made of optical glass with n=2.00.

[0052] Example 14: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 1 is that the first substrate 11 is made of lithium niobate with n=2.30, and the second substrate 12 is made of optical resin with n=1.71.

[0053] Example 15: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 1 is that the coupling grating 2 and the coupling grating 3 are made of optical glass.

[0054] Example 16: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 1 is that the coupling grating 2 and the coupling grating 3 are made of lithium niobate.

[0055] Example 17: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 1 is that the coupling grating 2 and the coupling grating 3 are made of silicon carbide.

[0056] Example 18: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 1 is that the coupling grating 2 and the coupling grating 3 are made of silicon nitride.

[0057] Comparative Example 1: Reference Figure 9 This is a composite diffractive waveguide lens disclosed in this invention. The difference from Embodiment 2 is that it does not include the second substrate 12, the thickness of the first substrate 11 is 0.70 mm, and the coupling grating 2 is disposed on the surface of the first substrate 11 away from the incident light source.

[0058] Comparative Example 2: This is a composite diffractive waveguide lens disclosed in this invention. The difference from Example 3 is that it does not include the second substrate 12, the thickness of the first substrate 11 is 0.70 mm, and the coupling grating 2 is disposed on the surface of the first substrate 11 away from the incident light source.

[0059] Comparative Example 3: Reference Figure 10 This is a composite diffractive waveguide lens disclosed in this invention. The difference from Embodiment 6 is that it does not include the second substrate 12, the thickness of the first substrate 11 is 0.70 mm, and the coupling grating 2 is disposed on the surface of the first substrate 11 near the incident light source.

[0060] Comparative Example 4: Reference Figure 11This is a composite diffractive waveguide lens disclosed in this invention. The difference from Embodiment 8 is that it does not include the second substrate 12, the thickness of the first substrate 11 is 0.70 mm, and the coupling grating 2 is disposed on the surface of the first substrate 11 away from the incident light source.

[0061] Comparative Example 5: Reference Figure 12 This is a composite diffractive waveguide lens disclosed in this invention. The difference from embodiment 10 is that it does not include the second substrate 12, the thickness of the first substrate 11 is 0.70 mm, and the coupling grating 2 is disposed on the surface of the first substrate 11 away from the incident light source.

[0062] Experimental Example 1: The coupling energy of the composite diffractive waveguide lens obtained in Example 1 and Comparative Example 1 was simulated and analyzed. The calculation conditions were set as follows: field of view (FOV) = 20°, aspect ratio 4:3, and nine typical field of view points were selected to calculate the coupling diffraction efficiency and transmittance. Since the refractive indices of the first substrate 11 and the second substrate 12 are the same, T... -1 R0, T0, R -1 The diffraction efficiencies of all orders are equal. Table 1 shows the diffraction efficiencies and overall coupling efficiencies at each field of view, and their transmittance in the visible light band is compared as follows: Figure 13 As shown.

[0063] Table 1 FOV-1 1.61% 1.24% 0.32% 0.33% 96.78% 1.61% 1.52% FOV-2 1.43% 1.19% 0.32% 0.30% 96.91% 1.43% 1.46% FOV-3 1.42% 1.17% 0.32% 0.33% 96.92% 1.42% 1.44% FOV-4 1.94% 1.08% 0.39% 1.39% 95.81% 1.94% 1.43% FOV-5 1.79% 1.01% 0.37% 1.38% 95.96% 1.79% 1.34% FOV-6 1.75% 0.97% 0.37% 1.48% 95.92% 1.75% 1.31% FOV-7 1.92% 0.89% 0.50% 4.14% 93.12% 1.92% 1.35% FOV-8 1.81% 0.79% 0.49% 4.24% 93.20% 1.81% 1.25% FOV-9 1.75% 0.74% 0.49% 4.52% 93.00% 1.75% 1.20% From Table 1 and Figure 13 It can be seen that the maximum difference in coupling energy between the composite diffractive waveguide lens of Example 1 and the traditional structure of Comparative Example 1 is between -0.03 and 0.57%, and the overall coupling efficiency is basically the same. The traditional structure of Comparative Example 1 has an average transmittance of 93.7% in the 400-700nm band, while the composite diffractive waveguide lens of Example 1 has an average transmittance of 97%, which is 3.3% higher than the traditional solution.

[0064] Experimental Example 1: The coupling energy of the composite diffractive waveguide lenses obtained in Example 3 and Comparative Example 5 was simulated and analyzed. The calculation conditions were set as follows: field of view (FOV) = 25°, aspect ratio 4:3, and nine typical field of view points were selected to calculate the coupling diffraction efficiency and transmittance. Since the refractive indices of the first substrate 11 and the second substrate 12 are the same, T... -1 R0, T0, R -1 The diffraction efficiencies of all orders are equal. Table 2 shows the diffraction efficiencies and overall coupling efficiencies at each field of view, and their transmittance in the visible light band is compared as follows: Figure 14 As shown.

[0065] Table 2 FOV-1 4.22% 2.19% 1.58% 1.73% 88.48% 4.22% 3.63% FOV-2 3.95% 2.17% 1.07% 2.57% 87.75% 3.95% 3.16% FOV-3 3.48% 2.22% 1.21% 3.97% 85.99% 3.48% 3.35% FOV-4 4.20% 2.13% 1.13% 1.58% 89.33% 4.20% 3.17% FOV-5 4.23% 2.22% 1.15% 0.68% 90.33% 4.23% 3.24% FOV-6 4.02% 2.26% 1.46% 0.43% 90.61% 4.02% 3.59% FOV-7 3.78% 2.29% 1.61% 0.28% 90.50% 3.78% 3.75% FOV-8 3.31% 2.19% 1.22% 1.01% 89.75% 3.31% 3.31% FOV-9 3.23% 2.21% 1.59% 0.70% 90.35% 3.23% 3.66% From Table 2 and Figure 14It can be seen that the maximum difference in coupling energy between the composite diffractive waveguide lens of Example 3 and the traditional structure of Comparative Example 5 is between 0.13% and 1.03%, and the overall coupling efficiency is basically the same. The traditional structure of Comparative Example 5 has an average transmittance of 75% in the 400-700nm band, while the composite diffractive waveguide lens of Example 3 has an average transmittance of 89%, which is significantly improved by 14% compared with the traditional solution.

[0066] The specific implementation principle of this invention is as follows: the light beam enters the composite diffractive waveguide lens from the first substrate 11. When the light beam first passes through the coupling grating 3, the composite diffractive waveguide has two more coupling paths at the coupling grating 3 compared to Comparative Example 1. The difference between Embodiment 1 and Embodiment 3 is that the interface where the light beam first reaches the coupling grating 3 is different, and the diffraction orders of the two additional coupling paths are different. The first coupling path in Comparative Example 1 is R. -1 The coupling path of the scheme in Example 1 is T. -1 R0-T -1 T0-R -1 The coupling path of the scheme in Example 3 is R. -1 R0-R -1 T0-T -1 When the energy of the coupling grating 3 reaches I, the first coupling energies for Comparative Example 1, Example 1, and Example 3 are respectively: R -1 ×I、(T -1 +R0×T -1 +T0×R -1 )×I、(R -1 +R0×R -1 +T0×T -1 )×I.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A composite diffractive waveguide lens, characterized in that: The system includes at least two waveguide substrates (1) stacked together, a coupling grating (2) disposed on the surface of one of the waveguide substrates (1), and a coupling grating (3) disposed between the two waveguide substrates (1). The refractive indices of the at least two waveguide substrates (1) are the same or decrease in the direction away from the incident light source. The coupling grating (2) couples the incident light beam into the at least two waveguide substrates (1). After the coupled light beam undergoes total internal reflection in the at least two waveguide substrates (1), the coupling grating (3) couples the light beams from different waveguide substrates (1) out at different diffraction orders.

2. The composite diffractive waveguide lens according to claim 1, characterized in that: The at least two waveguide substrates (1) are configured as a first substrate (11) and a second substrate (12), wherein the refractive index of the first substrate (11) exceeds the refractive index of the second substrate (12), the coupling grating (2) is a reflective grating, the coupling grating (2) is disposed on the surface of the first substrate (11) or the second substrate (12) away from the incident light source, and the coupling grating (3) is disposed between the first substrate (11) and the second substrate (12).

3. The composite diffractive waveguide lens according to claim 1, characterized in that: The at least two waveguide substrates (1) are configured as a first substrate (11) and a second substrate (12), the refractive index of the first substrate (11) exceeds the refractive index of the second substrate (12), the coupling grating (2) is a transmission grating, the coupling grating (2) is disposed on the surface of the first substrate (11) or the second substrate (12) near the incident light source, and the coupling grating (3) is disposed between the first substrate (11) and the second substrate (12).

4. A composite diffractive waveguide lens according to claim 1, characterized in that: The output grating (3) is configured as a one-dimensional straight grating, a one-dimensional blazed grating, a one-dimensional tilted grating or a one-dimensional gradient grating. The surface of one of the waveguide substrates (1) is also selectively provided with a bend grating. The bend grating is used to receive the light beam coupled into the input grating (2) and guide the light beam to the region of the output grating (3).

5. A composite diffractive waveguide lens according to claim 1, characterized in that: The coupling grating (3) is configured as a two-dimensional straight grating, a two-dimensional blazed grating, a two-dimensional tilted grating, or a two-dimensional gradient grating, and the coupling grating (3) is used for two-dimensional pupil expansion.

6. A composite diffractive waveguide lens according to any one of claims 1 to 5, characterized in that: The materials of the at least two waveguide substrates (1) are each independently optical glass, optical resin, lithium niobate or silicon carbide.

7. A composite diffractive waveguide lens according to claim 6, characterized in that: The thickness of each of the at least two waveguide substrates (1) is independently 0.10~1.0 mm.

8. A composite diffractive waveguide lens according to any one of claims 1 to 5, characterized in that: The materials of the coupling grating (2) and the coupling grating (3) are independently optical glass, optical resin, lithium niobate, silicon carbide, titanium dioxide or silicon nitride.

9. A composite diffractive waveguide lens according to claim 8, characterized in that: The structural parameters of the coupled grating (2) satisfy at least one of the following conditions. The grating period is 250~400nm; The grating height is 30~250nm; The duty cycle is 20-80%.

10. A composite diffractive waveguide lens according to claim 8, characterized in that: The structural parameters of the coupling grating (3) satisfy at least one of the following conditions. The grating period is 250~400nm; The grating height is 30~250nm; The duty cycle is 20-80%.

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