Projection engines, optical projection systems, and AR optical display devices

Abstract

This application discloses a projection optical engine, an optical projection system, and an AR optical display device. The projection optical engine includes a projection lens. The projection lens includes a cemented lens, the cementing surface of which is aspherical, and the angle between the tangent at any point on the cementing surface of the cemented lens and the optical axis of the projection lens is α, where 45°≤α≤90°.

Description

Technical Field

[0001] This application belongs to the field of optical display technology. Specifically, this application relates to a projection optical engine, an optical projection system, and an AR optical display device. Background Technology

[0002] With the rise of the metaverse concept, AR glasses, as a key hardware carrier, have received widespread attention. The key to the widespread adoption of AR glasses lies in their miniaturization and lightweight design. As a core component of AR glasses, the miniaturization of the projection optical engine has become a significant trend in current technological development. Optical engines based on μLED technology are considered the ultimate choice in the industry due to their simple structure, small size, and high display performance potential. However, traditional AR lens designs suffer from the problem of aberrations and chromatic aberration that are difficult to completely eliminate, affecting image quality. Therefore, developing new lens structures has become crucial for improving the optical performance of projection lenses. Summary of the Invention

[0003] The purpose of this application is to provide a new technical solution for a projection optical engine, an optical projection system, and an AR optical display device.

[0004] According to a first aspect of this application, an embodiment of this application provides a projection optical engine, the projection optical engine including a projection lens;

[0005] The projection lens includes a cemented lens, the cementing surface of the cemented lens is aspherical, and the angle between the tangent at any point on the cementing surface of the cemented lens and the optical axis of the projection lens is α, where 45°≤α≤90°.

[0006] Optionally, the cemented lens includes a second lens and a third lens arranged along the same optical axis and cemented together with each other;

[0007] The center thickness of the second lens is T2, and the effective optical aperture of the second lens is L2, where 0.25≤T2 / L2≤0.45;

[0008] The center thickness of the third lens is T3, and the effective optical aperture of the third lens is L3, where 0.1 ≤ T3 / L3 ≤ 0.3.

[0009] Optionally, the curvature of the surface of the second lens away from the third lens is K1, the curvature of the cemented surface where the second lens and the third lens are cemented together is K2, the curvature of the surface of the third lens away from the second lens is K3, and the total effective focal length of the cemented lens is f, 0.05≤(K1+K2+K3) / |f|≤0.3.

[0010] Optionally, the Abbe number of the second lens is v2, and the Abbe number of the third lens is v3, where |v2-v3|>20.

[0011] Optionally, the refractive index of the second lens is n2, and the refractive index of the third lens is n3, where n2 / n3 > 1.5.

[0012] Optionally, both the second lens and the third lens are aspherical lenses, and the optical power of the cemented lens is positive.

[0013] Optionally, the projection lens further includes a first lens and a fourth lens, the cemented lens is located between the first lens and the fourth lens, the first lens is located on the side closer to the second lens, and the fourth lens is located on the side closer to the third lens;

[0014] The first lens, the second lens, and the fourth lens have positive optical power, and the third lens has negative optical power.

[0015] Optionally, the first lens is a meniscus lens, the second lens is a biconvex lens, the third lens is a biconcave lens, and the fourth lens is a meniscus lens.

[0016] Optionally, the total effective focal length (EFL) of the projection lens is 5mm. <EFL<12mm。

[0017] Optionally, the effective focal length of the first lens is f1.4mm. <f1<12mm;

[0018] The effective focal length of the second lens is f2, 1mm. <f2<7mm;

[0019] The effective focal length of the third lens is f3, -8mm. <f3<-0.8mm;

[0020] The effective focal length of the fourth lens is f4.8mm. <f4<80mm。

[0021] Optionally, the center thickness of the first lens is T1, where 0.3 mm < T1 < 1 mm;

[0022] The center thickness of the second lens is T2, where 0.5mm < T2 < 1.5mm;

[0023] The center thickness of the third lens is T3, where 0.25mm < T3 < 1mm;

[0024] The center thickness of the fourth lens is T4, where 0.3mm < T4 < 1.2mm.

[0025] Optionally, the projection optical engine further includes a color combining prism and an image source;

[0026] The projection lens and the image source are respectively disposed on the periphery of the color combining prism, wherein the projection lens is located on the light-emitting side of the color combining prism;

[0027] An aperture is provided on the side of the projection lens that is away from the color combining prism.

[0028] Optionally, the aperture stop is the front aperture stop of the projection optical engine, the first lens is close to the aperture stop, and the fourth lens is far from the aperture stop;

[0029] The air gap between the first lens and the aperture stop is A0, where 0 ≤ A0 < 3 mm;

[0030] The air gap between the first lens and the second lens is A1, where 0.08mm ≤ A1 < 1mm;

[0031] The air gap between the second lens and the third lens is A2, where A2 = 0;

[0032] The air gap between the third lens and the fourth lens is A3, where 0.3mm ≤ A3 < 3mm;

[0033] The air gap between the fourth lens and the color-combining prism is A4, where 0.1mm ≤ A4 < 1mm.

[0034] Optionally, the radius of curvature of the surface of the first lens near the aperture is R1, where 1mm < R1 < 10mm; the radius of curvature of the surface of the first lens near the second lens is R2, where R2 < 30mm.

[0035] The radius of curvature of the surface of the second lens near the first lens is R3, 1mm < R3 < 10mm; the radius of curvature of the cemented surface of the second lens and the third lens is R4, -10mm < R4 < 200mm; the radius of curvature of the surface of the third lens near the fourth lens is R6, 0.8mm < R6 < 8mm.

[0036] The radius of curvature of the surface of the fourth lens near the third lens is R7, -10mm < R7 < 50mm; the radius of curvature of the surface of the fourth lens near the color-combining prism is R8, -10mm < R8 < -1mm.

[0037] Optionally, the image source is a Micro LED, and the size of each pixel on the image source is a panel pixel, where 2μm < panel pixel < 5μm;

[0038] The image height H of the image source is: 0 < H ≤ 6 mm.

[0039] According to a second aspect of this application, embodiments of this application provide an optical projection system, the optical projection system comprising:

[0040] The projection optical engine as described in the first aspect; and

[0041] An optical waveguide sheet is used to propagate the projection light emitted from the projection optical engine to the target position for imaging;

[0042] The distance between the exit pupil of the projection optical engine and the entrance pupil of the optical waveguide is 2mm to 5mm.

[0043] According to a third aspect of this application, embodiments of this application provide an AR optical display device, the AR optical display device including the optical projection system as described in the second aspect.

[0044] One beneficial effect of the embodiments of this application is that:

[0045] The projection optical engine proposed according to the embodiments of this application aims to achieve a high-performance and miniaturized projection optical engine by optimizing the optical design of the projection lens; wherein, by optimizing the surface shape of the cementing surface of the cemented lens, the cementing between aspherical lenses is realized, so that aspherical cemented lenses can be introduced into the projection lens, which can effectively reduce transverse chromatic aberration and on-axis and off-axis aberrations, and improve imaging quality.

[0046] The surface design of the cemented lens provided in this application ensures the smooth progress of the aspherical thermal bonding process while guaranteeing that the surfaces of the two aspherical lenses can fit tightly together after bonding. This not only improves the success rate of cemented aspherical lens manufacturing but also enhances the stability and durability of the cemented lens, laying the foundation for the miniaturization, high-precision imaging, and long-term stable operation of projection optical engines.

[0047] Other features and advantages of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0048] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the present application and, together with their description, serve to explain the principles of the present application.

[0049] Figure 1 This is one of the structural schematic diagrams of the projection optical engine provided in the embodiments of this application;

[0050] Figure 2 This is a second schematic diagram of the structure of the projection optical engine provided in the embodiments of this application;

[0051] Figure 3 This is a schematic diagram of the projection optical engine provided in Embodiment 1 of this application;

[0052] Figure 4 for Figure 3 The MTF diagram of the projection lens in the projection optical engine is shown.

[0053] Figure 5 for Figure 3 The diagram shows the optical distortion of the projection lens in the projection engine;

[0054] Figure 6 for Figure 3 The defocus MTF diagram of the projection lens in the projection optical engine is shown.

[0055] Figure 7 for Figure 3 The diagram shows the relative illumination of the projection lens in the projection engine;

[0056] Figure 8 for Figure 3 The diagram showing the transverse chromatic aberration of the projection lens in the projection engine is shown.

[0057] Figure 9 This is a schematic diagram of the projection optical engine provided in Embodiment 2 of this application;

[0058] Figure 10 for Figure 9 The MTF diagram of the projection lens in the projection optical engine is shown.

[0059] Figure 11 for Figure 9 The diagram shows the optical distortion of the projection lens in the projection engine;

[0060] Figure 12 for Figure 9 The defocus MTF diagram of the projection lens in the projection optical engine is shown.

[0061] Figure 13 for Figure 9 The diagram shows the relative illumination of the projection lens in the projection engine;

[0062] Figure 14 for Figure 9 The diagram shows the transverse chromatic aberration of the projection lens in the projection engine.

[0063] Explanation of reference numerals in the attached figures:

[0064] 1. Aperture; 2. Projection lens; 21. First lens; 211. First surface; 212. Second surface; 22. Second lens; 221. Third surface; 222. Fourth surface; 23. Third lens; 231. Fifth surface; 232. Sixth surface; 24. Fourth lens; 241. Seventh surface; 242. Eighth surface; 3. Color combining prism; 4. Image source. Detailed Implementation

[0065] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0066] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0067] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0068] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0069] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0070] The projection engine, optical projection system, and AR optical display device provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0071] According to one embodiment of this application, a projection optical engine is provided, see [link to relevant documentation]. Figure 1 and Figure 2 The projection optical engine includes a projection lens 2, which includes a cemented lens. The cemented surface of the cemented lens is aspherical, and the angle between the tangent at any point on the cemented surface of the cemented lens and the optical axis of the projection lens is α, where 45°≤α≤90°.

[0072] The projection optical engine provided in this application incorporates a cemented lens in its projection lens, and the cementing surface of this cemented lens is aspherical. This design combines the advantages of aspherical lenses in reducing on-axis and off-axis aberrations with the effect of cemented lenses in reducing transverse chromatic aberration, thereby improving the overall imaging quality of the projection optical engine. In other words, the use of an aspherical cemented lens in the projection lens of this application effectively reduces transverse chromatic aberration and on-axis and off-axis aberrations, significantly improving the sharpness and imaging quality of the projected image.

[0073] In the technical solution provided in this application embodiment, the bonding surface of the cemented lens is constrained such that the angle α between the tangent at any point on the bonding surface and the optical axis of the entire projection lens is limited to between 45° and 90° (inclusive of the two endpoints, 45° and 90°). By precisely controlling the angle range of the bonding surface, the smooth progress of the thermal bonding process is ensured, while the tightness of the aspherical lens after bonding is enhanced, thereby improving the stability and durability of the cemented lens and providing a guarantee for the long-term stable operation of the projection optical engine.

[0074] In the embodiments of this application, the projection lens includes the above-mentioned cemented lens, and the air gap between the cemented lenses is zero. This design not only simplifies the projection lens structure, but also helps to reduce light interference during propagation and further improve the clarity of the image.

[0075] In the embodiments of this application, an aspherical cemented lens is introduced into the projection lens. This design can effectively reduce on-axis and off-axis aberrations, while also reducing transverse chromatic aberration, enabling the projection engine to output higher quality images and meet users' requirements for clarity and color reproduction. Furthermore, the aspherical cemented lens design also contributes to the miniaturization and weight reduction of the overall projection engine structure, aligning with current market trends towards portable and highly integrated products.

[0076] The projection optical engine proposed in the embodiments of this application achieves high performance and miniaturization by optimizing the optical design of the projection lens; wherein, by optimizing the surface shape of the cementing surface of the cemented lens, the cementing between aspherical lenses is realized, so that aspherical cemented lenses can be introduced into the projection lens, which can effectively reduce transverse chromatic aberration and on-axis and off-axis aberrations, and improve imaging quality.

[0077] The surface design of the cemented lens provided in this application ensures the smooth progress of the aspherical thermal bonding process while guaranteeing that the surfaces of the two aspherical lenses can fit tightly together after bonding. This not only improves the success rate of cemented aspherical lens manufacturing but also enhances the stability and durability of the cemented lens, laying the foundation for the miniaturization, high-precision imaging, and long-term stable operation of projection optical engines.

[0078] In summary, the projection optical engine provided in this application significantly improves imaging quality and manufacturing feasibility by employing aspherical cemented lenses and a fine cemented surface shape constraint design, providing strong support for technological advancements and market applications in fields such as AR smart glasses and related areas.

[0079] See some examples in this application. Figure 1 and Figure 2The cemented lens includes a second lens 22 and a third lens 23 arranged along the same optical axis and cemented together; the center thickness of the second lens 22 is T2, and the effective optical aperture of the second lens 22 is L2, 0.25≤T2 / L2≤0.45; the center thickness of the third lens 23 is T3, and the effective optical aperture of the third lens 23 is L3, 0.1≤T3 / L3≤0.3.

[0080] In this example of the application, the design of the cemented lens has been further optimized. By controlling the ratio of the center thickness of the second lens 22 and the third lens 23 to the effective optical aperture, the optical performance of the lens has been significantly improved, thereby improving the optical performance of the entire cemented lens.

[0081] Specifically, for the second lens 22, the ratio between its center thickness T2 and its effective optical aperture L2 is 0.25 ≤ T2 / L2 ≤ 0.45. For the third lens 23, the ratio between its center thickness T3 and its effective optical aperture L3 is 0.1 ≤ T3 / L3 ≤ 0.3.

[0082] By controlling the ratio of the center thickness to the effective optical aperture of the two cemented lenses, namely the second lens 22 and the third lens 23, the optical power of the entire projection engine can be rationally allocated without sacrificing image quality. This optimization helps reduce the tolerance sensitivity of each lens, thereby improving the manufacturing yield and stability of the projection lens.

[0083] The ratio of the lens's center thickness to its effective optical aperture directly impacts image quality. Adhering to this ratio ensures that the projection lens maintains good imaging consistency across various fields of view, reducing aberrations and distortion, thus providing a clearer projected image. This is of great significance for improving the overall imaging performance of a projection optical engine.

[0084] While maintaining imaging performance, a well-designed lens thickness also helps reduce the overall size and weight of the projection lens. This is crucial for optical display products such as AR smart glasses that prioritize portability and comfortable wearing experience.

[0085] A well-designed ratio of center thickness to effective optical aperture helps enhance the mechanical strength and stability of the lens, reducing the risk of lens deformation or damage due to stress concentration. This is crucial for maintaining the long-term stability of the lens's optical performance.

[0086] Furthermore, from the perspective of optimizing lens processing and assembly, precisely controlling the ratio of the lens's center thickness to its effective optical aperture ensures that the lens processing difficulty is moderate—neither overly complex nor prone to errors. This helps improve the lens's yield and processing efficiency, while also facilitating the subsequent assembly process and ensuring precise fit between components.

[0087] Therefore, by precisely controlling the ratio of the center thickness of the second lens 22 and the third lens 23 in the cemented lens to the effective optical aperture, this application not only optimizes the processing, assembly and performance stability of the lens, but also further improves the imaging quality, providing strong support for the miniaturization, weight reduction and high performance of projection optical engines.

[0088] In some examples of this application, the curvature of the surface of the second lens 22 facing away from the third lens 23 is K1, the curvature of the cemented surface where the second lens 22 and the third lens 23 are cemented together is K2, the curvature of the surface of the third lens 23 facing away from the second lens 22 is K3, and the total effective focal length of the cemented lens is f, 0.05≤(K1+K2+K3) / |f|≤0.3.

[0089] In this example of the application, a specific constraint is introduced regarding the proportional relationship between the three surface curvatures K1, K2, and K3 and the total effective focal length f of the cemented lens, namely 0.05 ≤ (K1 + K2 + K3) / |f| ≤ 0.3. This design brings about several technical benefits, as detailed below.

[0090] By controlling the proportional relationship between the curvature of each surface in a cemented lens and the total effective focal length of the lens, the optical characteristics of the cemented lens can be managed more effectively. This constraint helps reduce aberrations, thereby improving image quality. In particular, for aspherical lenses, properly controlling the curvature distribution of the surfaces can significantly enhance their ability to modulate light, allowing light to be focused more accurately after passing through the lens, forming a clear image.

[0091] See Figure 2 The three surfaces of the cemented lens are the non-cemented surface of the second lens 22 (i.e., the third surface 221), the cemented surface of the second lens 22 and the third lens 23, respectively. Figure 2The fourth surface 222 and the fifth surface 231, as well as the non-cemented surface of the third lens 23 (i.e., the sixth surface 232), are shown in the diagram. The reasonable distribution of curvature on these three surfaces helps reduce the risk of deformation of the cemented lens due to stress concentration. Lens stability is crucial for maintaining the long-term optical performance of the system. In this application, by optimizing the ratio of the curvature of each surface in the cemented lens (which is a core lens in the projection lens of this application) to the total focal length of the cemented lens, the mechanical strength of the cemented lens can be enhanced, thereby improving the stability of the entire projection lens 2.

[0092] The constraints presented in this example also provide guiding principles for the lens manufacturing process, helping to precisely control the lens's curvature parameters during production. This not only improves lens processing accuracy but also reduces scrap rates and increases production efficiency. Furthermore, due to the direct correlation between curvature parameters and lens focal length, it is easier to control the lens focal length by adjusting the curvature.

[0093] In some examples of this application, the Abbe number of the second lens 22 is v2, the Abbe number of the third lens 23 is v3, and |v2-v3|>20.

[0094] In the embodiments of this application, the cemented lens in the projection lens 2 comprises a second lens 22 and a third lens 23 cemented together. Regarding the material selection for the second lens 22 and the third lens 23, it is explicitly stipulated that the difference between their Abbe numbers v2 and v3 should be greater than 20, i.e., |v2-v3|>20. This constraint aims to significantly improve the achromatic function of the cemented aspherical lens by optimizing the dispersion characteristics of the lens material.

[0095] The Abbe number is an important parameter for measuring the dispersion characteristics of optical materials, reflecting the difference in refractive index of the material for different wavelengths of light.

[0096] In the cemented lens design provided in this application, by selecting two materials with significantly different Abbe numbers to fabricate the second lens 22 and the third lens 23 respectively, the two materials can be made to have different dispersion characteristics for light of different wavelengths. When these two lenses are cemented together, their dispersion difference can be effectively compensated, thereby significantly reducing transverse chromatic aberration and other aberrations caused by dispersion. This improved achromatic aberration capability is a significant advantage of cemented aspherical lenses in image quality compared to conventional single lenses.

[0097] By controlling the Abbe number differences in lens materials, cemented aspherical lenses can maintain excellent imaging performance at various wavelengths. This not only reduces color fringing but also improves image sharpness. This technology is particularly important for applications requiring high-precision imaging, such as augmented reality glasses.

[0098] In some examples of this application, the refractive index of the second lens 22 is n2, and the refractive index of the third lens 23 is n3, where n2 / n3 > 1.5.

[0099] In the cemented lens of this application, a specific ratio is set for the refractive indices of the second lens 22 and the third lens 23, namely, the ratio of the refractive index n2 of the second lens to the refractive index n3 of the third lens is greater than 1.5 (n2 / n3>1.5). This constraint aims to ensure that the aspherical cemented lens can achieve its maximum capability in modulating light by optimizing the refractive indices of the two lenses.

[0100] Refractive index is a physical quantity that describes the speed of light in a medium and is also an important indicator of a lens's ability to control the direction of light. In optical systems, lenses with high refractive index can better bend light rays, causing them to propagate along a predetermined path.

[0101] In this application, by setting a large refractive index difference between the second lens 22 and the third lens 23, light undergoes a more significant directional change when passing through the cemented lens composed of these two lenses, thereby enhancing the modulation capability of the aspherical lens. This is crucial for improving the resolution, contrast, and sharpness of the imaging system. Enhanced modulation capability of the aspherical lens means that light can be more precisely focused to a predetermined position after passing through the lens, forming a clearer image. This helps reduce aberrations and distortion, improving the overall optical performance of the projection lens. In applications such as augmented reality (AR) glasses, this technical effect has a significant impact on improving user experience and visual effects.

[0102] In summary, by setting a large refractive index ratio (n2 / n3 > 1.5) between the second lens 22 and the third lens 23, this application effectively enhances the light modulation capability of the aspherical cemented lens, thereby improving image quality, increasing design flexibility, and promoting technological innovation. This technical effect is of great significance for improving the overall performance of the projection optical engine and meeting diverse application needs.

[0103] In some examples of this application, the second lens 22 and the third lens 23 are both aspherical lenses, and the optical power of the cemented lens is positive.

[0104] In the projection lens provided in this application embodiment, the second lens 22 and the third lens 23 are designed as aspherical lenses and are tightly bonded together into a single cemented lens using a specific "thermal bonding" process, and this cemented lens has positive optical power. This design choice is beneficial for enhancing the optical performance of the entire projection lens, and even the entire projection optical engine.

[0105] Compared to spherical lenses, aspherical lenses offer greater freedom in optical design and can better correct various aberrations. By designing both the second lens 22 and the third lens 23 as aspherical and cementing them together as a single unit, the propagation path of light passing through the lens can be controlled more effectively, significantly reducing on-axis and off-axis aberrations, thereby improving image quality.

[0106] Aspherical lenses combined with cemented bonding processes not only reduce aberrations but also minimize transverse chromatic aberration by precisely matching lens materials and thicknesses to minimize the positional deviation of different wavelengths of light on the imaging plane. This is crucial for improving color reproduction and image sharpness.

[0107] In this example of the application, the cemented lens has a positive optical power, which helps to optimize the optical power distribution of the entire projection lens 2. A positive optical power cemented aspherical lens allows for more flexible allocation of optical power in the overall projection lens design. Because aspherical lenses can more precisely control the direction of light, higher optical performance can be achieved while maintaining the miniaturization of the projection lens.

[0108] By using aspherical cemented lenses, the number of lenses in the projection lens can be reduced or the lens combination can be simplified without sacrificing image quality, thereby reducing the size and weight of the projection lens and meeting the miniaturization and lightweight requirements of portable optical display devices such as AR glasses.

[0109] Although the fabrication of aspherical lenses is relatively complex, once they are cemented together to form a single lens, their processing in projection lens assembly becomes relatively simple. Furthermore, the adoption of a positive optical power design strategy reduces the tolerance sensitivity of the entire projection lens, contributing to improved production yield.

[0110] See some examples in this application. Figure 1 and Figure 2 The projection lens 2 further includes a first lens 21 and a fourth lens 24. The cemented lens is located between the first lens 21 and the fourth lens 24. The first lens 21 is located on the side closer to the second lens 22, and the fourth lens 24 is located on the side closer to the third lens 23. The first lens 21, the second lens 22, and the fourth lens 24 have positive optical power, and the third lens 23 has negative optical power.

[0111] In this example of the application, the projection lens 2 is designed with four lenses—a first lens 21, a second lens 22, a third lens 23, and a fourth lens 24. The second lens 22 and the third lens 23 form a cemented lens, and their optical power is allocated accordingly, achieving a significant technical effect. Specifically:

[0112] (1) Balanced distribution of optical power:

[0113] By assigning positive optical power to the first lens 21, the second lens 22, and the fourth lens 24, while assigning negative optical power to the third lens 23, a balanced distribution of optical power is achieved. This arrangement not only ensures a smooth transition of light between the lenses but also makes the optical correction task borne by each lens relatively balanced, without requiring extreme optical parameters.

[0114] (2) Application and aberration control of cemented aspherical lenses:

[0115] The cemented aspherical lens, composed of the second lens 22 and the third lens 23, is the core component of the projection lens of this application. By employing an advanced "thermal bonding" process, a tight bond between the aspherical lens surfaces is ensured, thereby fully leveraging the advantages of aspherical lenses in reducing on-axis and off-axis aberrations. Furthermore, the structure of the cemented lens effectively reduces transverse chromatic aberration, improving overall image quality.

[0116] (3) Improved image quality:

[0117] Thanks to the introduction of cemented aspherical lenses, the projection lens performs exceptionally well in terms of color reproduction, contrast, and sharpness. This characteristic is crucial for high-precision imaging devices such as augmented reality (AR) glasses, enabling users to experience a more realistic and immersive visual experience.

[0118] In some examples of this application, the first lens 21 is a meniscus lens, the second lens 22 is a biconvex lens, the third lens 23 is a biconcave lens, and the fourth lens 24 is a meniscus lens.

[0119] In this example of the application, the projection lens is designed to employ four specific types of lenses: a meniscus-shaped first lens 21, a biconvex second lens 22, a biconcave third lens 23, and a meniscus-shaped fourth lens 24.

[0120] The first lens 21 and the fourth lens 24 are meniscus lenses. The design of the meniscus lens helps to provide a smooth optical transition in the optical path and reduce unnecessary light reflection and scattering. Using a meniscus lens at the light-incident position of the projection lens 2 can effectively collect and guide light into the projection lens; while using a meniscus lens at the light-out position can fine-tune the light after the complex optical path processing to ensure that the light is projected onto the imaging surface at an ideal angle.

[0121] The second lens 22 is a biconvex lens. As part of a cemented aspherical lens formed with the third lens 23, the biconvex design enhances positive optical power, helps converge light rays, and reduces spherical aberration. When cemented with a biconcave lens, it can better correct aberrations and improve image sharpness.

[0122] The third lens 23 is a biconcave lens. The biconcave design gives the lens negative optical power. When used in combination with the biconvex lens (second lens 22), through precise cementing, it can effectively correct field curvature and reduce on-axis and off-axis aberrations, especially field curvature and distortion.

[0123] In the projection lens of this application, the second lens 22 and the third lens 23 are cemented together to form a cemented aspherical lens, which not only significantly reduces chromatic aberration along the transverse axis but also improves color reproduction. The biconvex and biconcave cementing design allows the advantages of the aspherical lens to be fully utilized, further optimizing the optical performance of the projection lens.

[0124] In this example of the application, this lens combination method also helps to design a more compact and reasonable lens barrel and AR optomechanical module structure, further promoting the mass production and market penetration of the product.

[0125] In some examples of this application, the total effective focal length (EFL) of the projection lens 2 is 5mm. <EFL<12mm。

[0126] In this example of the application, the total effective focal length (EFL) of the projection lens 2 is set between 5mm and 12mm. This focal length range is designed to balance various factors such as image quality, field of view (FOV), projection lens size, and applicable scenarios.

[0127] Shorter focal lengths (e.g., 5mm–12mm) help achieve a wider field of view, which is especially important in augmented reality (AR) applications because it provides a wider field of view, allowing users to naturally immerse themselves in a virtual-to-real environment. However, excessively short focal lengths (below 5mm) may increase aberrations and affect image quality.

[0128] Setting the upper limit of the total effective focal length (EFL) of the projection lens 2 at 12mm ensures a certain field of view while providing sufficient design space for aberration correction. This focal length range allows for a balance between field of view and image quality through meticulous optical design, ensuring that users can enjoy clear, distortion-free images while obtaining a wide field of view.

[0129] In portable optical display devices such as AR glasses, miniaturization and lightweighting of the projection lens are crucial. A shorter effective focal length helps reduce the physical size and weight of the projection lens, thus meeting the requirements of miniaturizing the projection optical engine therein. By setting the EFL of the projection lens 2 between 5 mm and 12 mm, a compact design of the projection lens can be achieved while maintaining good imaging performance, thereby realizing the miniaturization of the projection optical engine.

[0130] In some examples of the present application, the effective focal length of the first lens 21 is f1, 4 mm < f1 < 12 mm; the effective focal length of the second lens 22 is f2, 1 mm < f2 < 7 mm; the effective focal length of the third lens 23 is f3, -8 mm < f3 < -0.8 mm; the effective focal length of the fourth lens 24 is f4, 8 mm < f4 < 80 mm.

[0131] In this example of the present application, the effective focal length ranges of the respective lenses in the projection lens 2 are described.

[0132] The effective focal length f1 of the first lens 21 is: 4 mm < f1 < 12 mm. As the first lens of the projection lens 2, it is responsible for collecting and initially focusing light ( Figure 1 and Figure 2 the optical path in is the reverse optical path design). The set range of the effective focal length f1 ensures sufficient converging ability while leaving a design margin to accommodate different optical configurations.

[0133] The effective focal length f2 of the second lens 22 is: 1 mm < f2 < 7 mm. The effective focal length f3 of the third lens is: -8 mm < f3 < -0.8 mm. Among them, as part of the cemented aspherical lens, the second lens 22 with a shorter focal length enhances the positive optical power and helps further converge light. After being cemented with the third lens 23 (negative optical power), the two jointly correct aberrations and improve the imaging quality. The third lens 23, with its negative optical power design, is used to correct field curvature and other off-axis aberrations.

[0134] The effective focal length f4 of the fourth lens 24 is: 8 mm < f4 < 80 mm. The relatively large effective focal length range enables the fourth lens 24 to play a role in fine-tuning the light direction in the optical path, ensuring that the light is projected onto the imaging surface at an ideal angle. In addition, it helps reduce residual aberrations and improve imaging clarity.

[0135] In this example of the present application, the effective focal lengths of the four lenses are set. By precisely controlling the effective focal length ranges of the respective lenses, a reasonable distribution of optical power is achieved. This distribution method not only optimizes the optical performance but also reduces the tolerance sensitivity of each lens.

[0136] Because of the uniform distribution of optical power, the impact of each lens on the overall optical performance is dispersed, making it easier for projection lenses to meet design requirements during the manufacturing process. This reduces the extreme dependence on processing precision and improves production stability and yield.

[0137] In some examples of this application, the center thickness of the first lens 21 is T1, 0.3mm < T1 < 1mm; the center thickness of the second lens 22 is T2, 0.5mm < T2 < 1.5mm; the center thickness of the third lens 23 is T3, 0.25mm < T3 < 1mm; and the center thickness of the fourth lens 24 is T4, 0.3mm < T4 < 1.2mm.

[0138] The center thickness T1 of the first lens 21 is 0.3mm < T1 < 1mm. This constraint ensures that the thickness of the first lens 21 is moderate, neither too thin to increase the processing difficulty and insufficient strength, nor too thick to cause unnecessary material waste and increase the size of the projection lens.

[0139] The center thickness T2 of the second lens 22 is 0.5mm < T2 < 1.5mm. As an important component of the projection lens 2, the proper control of the thickness of the second lens 22 helps to balance optical performance and manufacturing cost.

[0140] The center thickness T3 of the third lens 23 is 0.25mm < T3 < 1mm. The third lens 23 is a lens with a specific optical function (such as a negative power biconcave lens), and precise control of its thickness is crucial to achieving this function. A thinner lens design helps to achieve miniaturization of the optical mechanism, but it also requires ensuring sufficient processing accuracy and stability.

[0141] The center thickness T4 of the fourth lens 24 is 0.3mm < T4 < 1.2mm. As the last lens in the projection lens 2, its thickness setting has a significant impact on the final image quality. At the same time, a thinner lens design also helps to achieve miniaturization and weight reduction of the optical engine.

[0142] This example describes the center thickness of the four lenses that make up the projection lens. By setting a reasonable range for the center thickness of the lenses, the processing difficulties and strength problems caused by lenses that are too thin are avoided, as are the unnecessary processing costs and difficulties caused by lenses that are too thick. This helps to improve production efficiency and yield.

[0143] See some examples in this application. Figure 1 and Figure 2The projection optical engine also includes a color combining prism 3 and an image source 4; the projection lens 2 and the image source 4 are respectively disposed on the periphery of the color combining prism 3, wherein the projection lens 2 is located on the light-emitting side of the color combining prism 3; an aperture 1 is provided on the side of the projection lens 2 away from the color combining prism 3.

[0144] The structure of the projection optical engine provided in this application embodiment can be referred to... Figure 1 As shown, the components placed along the optical path are, in order: a front aperture 1, a projection lens 2 (containing four lenses, including a cemented aspherical lens), a color-combining prism 3, and an image source 4. For ease of design and evaluation, the optical structure has been simplified. The simplified optical structure can be found in the following reference. Figure 2 The color combining prism 3 is equivalent to a cube prism, and the three R / G / B image sources 4 are equivalent to one RGB image source 4.

[0145] The color combining prism 3, for example, is an Xcube color combining prism, which plays a crucial role in the entire projection optical engine. It combines light from different color image sources to form a full-color image. In this example of the application, the color combining prism 3 is responsible for combining light from multiple monochrome image sources 4 into a single full-color beam. See [link to relevant documentation]. Figure 1 .

[0146] The image source 4 provides the light signals required for AR displays. It refers to three monochrome MicroLEDs (μLED image sources) for R, G, and B colors, which produce red, green, and blue light respectively. In applications, these image sources can be controlled by driving circuits to generate the desired image content.

[0147] The projection lens 2 is responsible for receiving full-color light from the color combining prism and converging it onto the display area of ​​the AR glasses. The design of the projection lens is crucial to image quality, including sharpness, color reproduction, and field of view.

[0148] The aperture stop 1 is located in front of the projection lens 2 and is used to limit the range of light passing through the projection lens, thereby controlling the aperture size and depth of field of the image. The setting of the aperture stop plays an important role in adjusting the depth of field and image quality of the lens.

[0149] The projection optical engine provided in this application embodiment has a compact optical layout. By separately distributing the projection lens 2 and the image source 4 on the periphery of the color combining prism 3, and placing the projection lens 2 on the light-emitting side of the color combining prism 3, this layout effectively saves space, making the entire projection optical engine more compact. This is crucial for achieving miniaturization and weight reduction of projection optical devices (such as AR glasses).

[0150] The color combining prism 3 is located between the projection lens 2 and the image source 4, and can efficiently combine monochromatic light from different image sources into a full-color light beam, ensuring the color richness and fidelity of the image display.

[0151] In some examples of this application, the aperture 1 is the front aperture of the projection optical engine, the first lens 21 is close to the aperture 1, and the fourth lens 24 is far from the aperture 1; the air gap between the first lens 21 and the aperture 1 is A0, 0≤A0<3mm; the air gap between the first lens 21 and the second lens 22 is A1, 0.08mm≤A1<1mm; the air gap between the second lens 22 and the third lens 23 is A2, A2=0; the air gap between the third lens 23 and the fourth lens 24 is A3, 0.3mm≤A3<3mm; and the air gap between the fourth lens 24 and the color combining prism 3 is A4, 0.1mm≤A4<1mm.

[0152] In this example of the application, the air gap A0 between the aperture stop 1 and the first lens 21 is 0 ≤ A0 < 3 mm. This setting limits the minimum distance between the aperture stop 1 and the first lens 21, avoiding stray light or interference problems caused by excessive distance. It also provides sufficient space for assembling the projection lens 2, facilitating precise adjustment of the aperture stop position and ensuring accurate light transmission through the projection lens 2. This setting also helps reduce the volume of the front end of the projection lens 2, contributing to the miniaturization of the entire projection optical engine.

[0153] In this example of the application, the air gap A1 between the first lens 21 and the second lens 22 is 0.08mm ≤ A1 < 1mm. By controlling the distance between the first lens 21 and the second lens 22, it is ensured that light can smoothly enter the second lens 22 after passing through the first lens 21, reducing light energy loss. A narrower but reasonable air gap helps maintain the compactness of the projection lens 2 while ensuring stable optical performance.

[0154] In this example of the application, the air gap A2 between the second lens 22 and the third lens 23 is 0. This is because the second lens 22 and the third lens 23 are directly cemented together without any air gap between them, thus forming a cemented aspherical lens to optimize aberration correction and chromatic aberration reduction. The cemented lens design helps improve the imaging quality and optical performance of the projection lens 2, especially in reducing aberrations and chromatic aberration.

[0155] In this example of the application, the air gap A3 between the third lens 23 and the fourth lens 24 is 0.3mm ≤ A3 < 3mm. An appropriate air gap allows sufficient space for light to diffuse and refocus after passing through the third lens, reducing interference or stray light that may occur due to the lenses being too close together. Simultaneously, this gap also provides space for fine-tuning the assembly of the projection lens 2, ensuring that the fourth lens can be precisely positioned in the imaging optical path.

[0156] In this example of the application, the air gap between the fourth lens 24 and the color-combining prism 3 is A4: 0.1mm ≤ A4 < 1mm. Controlling the distance between the fourth lens 24 and the color-combining prism 3 ensures that full-color light can accurately enter the color-combining prism for color mixing. An appropriate gap also helps reduce light loss during transmission and improves the utilization rate of light energy.

[0157] This application's example, through precise control of each air gap, ensures the stability and rationality of the projection lens 2 structure, avoiding potential optical performance degradation due to improper spacing. The compact structural design facilitates the miniaturization and weight reduction of the optical engine. Furthermore, the reasonable air gaps provide sufficient space and flexibility for the assembly of the projection lens 2, making the assembly process smoother and more precise. This reduces potential errors and difficulties during assembly, improving production efficiency and yield.

[0158] In some examples of this application, the radius of curvature of the surface of the first lens 21 near the aperture 1 is R1, 1mm < R1 < 10mm; the radius of curvature of the surface of the first lens 21 near the second lens 22 is R2, R2 < 30mm.

[0159] The radius of curvature of the surface of the second lens 22 near the first lens 21 is R3, 1mm < R3 < 10mm; the radius of curvature of the cemented surface of the second lens 22 and the third lens 23 is R4, -10mm < R4 < 200mm; the radius of curvature of the surface of the third lens 23 near the fourth lens 24 is R6, 0.8mm < R6 < 8mm.

[0160] The radius of curvature of the surface of the fourth lens 24 near the third lens 23 is R7, -10mm < R7 < 50mm; the radius of curvature of the surface of the fourth lens 24 near the color-combining prism 3 is R8, -10mm < R8 < -1mm.

[0161] In this example of the application, see Figure 2 The radius of curvature of the first lens 21 is designed as follows:

[0162] The radius of curvature R1 of the first lens 21 near the aperture stop 1, i.e., the first surface 211, is 1mm < R1 < 10mm. This constraint ensures that the curvature of the incident surface of the first lens is neither too large nor too small, which helps to control the angle at which light enters the projection lens 2 and avoids excessive aberrations. The radius of curvature R2 of the first lens 21 near the second lens 22, i.e., the second surface 212, is R2 < 30mm. A larger radius of curvature helps to reduce manufacturing difficulty while ensuring good image quality.

[0163] In this example of the application, see Figure 2 The radii of curvature of the second lens 22 and the third lens 23 are designed as follows:

[0164] The radius of curvature R3 of the third surface 221 of the second lens 22, which is close to the first lens 21, is 1 mm < R3 < 10 mm. This constraint helps to control the transmission of light between the first lens 21 and the second lens 22, and maintains a small aberration.

[0165] The radius of curvature R4 of the bonding surface (fourth surface 222) between the second lens 22 and the third lens 23 is -10mm < R4 < 200mm. This wide constraint range allows for adjustments based on specific optical design requirements while ensuring that the bonding process is of moderate difficulty.

[0166] The bonding surface between the third lens 23 and the second lens 22 is the fifth surface 231. The fifth surface 231 has the same radius of curvature as the fourth surface 222. The radius of curvature of the fifth surface 231 is defined as R5: -10mm < R4 = R5 < 200mm.

[0167] The surface of the third lens 23 closest to the fourth lens 24, i.e., the sixth surface 232, has a radius of curvature R6 of 0.8 mm < R6 < 8 mm. This range limits the size of the radius of curvature, which helps to control the modulation effect of the lens on light while maintaining reasonable manufacturing difficulty.

[0168] In this example of the application, see Figure 2 The radius of curvature of the fourth lens 24 is designed as follows:

[0169] The surface of the fourth lens 24 closest to the third lens 23, i.e., the seventh surface 241, has a radius of curvature R7: -10mm < R7 < 50mm. A moderate radius of curvature helps maintain the imaging performance of the lens without excessively increasing the manufacturing difficulty.

[0170] The fourth lens 24, located near the surface of the color-combining prism 3 (i.e., the eighth surface 242), has a radius of curvature R8 of -10mm < R8 < -1mm. The negative radius of curvature helps to disperse or converge light, and can be adjusted according to the specific design to meet imaging requirements.

[0171] In this example of the application, the radius of curvature of each lens in the projection lens 2 is described. By constraining the radius of curvature appropriately, extreme curvatures are avoided, making the lens manufacturing process more stable and controllable, and reducing the scrap rate and cost during production. Appropriate radius of curvature design helps reduce lens aberrations and distortions, improving the image clarity and color reproduction of the projection lens. This is crucial for the design of the projection optical engine and directly affects the user's visual experience.

[0172] In some examples of this application, the image source 4 is a Micro LED, and the size of each pixel on the image source 4 is a panel pixel, 2μm < panel pixel < 5μm; the image height H of the image source 4 is 0 < H ≤ 6mm.

[0173] The image source 4 is Micro LED (μLED), a novel display technology based on LED technology, which boasts advantages such as high brightness, high contrast, high resolution, and fast response. Using Micro LED as the image source in a projection engine can significantly improve display quality and user experience.

[0174] Each pixel in the image source 4 has a size of a panel pixel, satisfying the condition 2μm < panel pixel < 5μm. This size range was chosen based on a trade-off between display precision and manufacturing cost. Smaller pixel sizes can provide higher resolution and finer image quality, but also increase manufacturing costs and complexity. Therefore, this range was chosen to control manufacturing costs while maintaining high display quality.

[0175] The image height H of the image source 4 is 0 < H ≤ 6 mm. This constraint limits the maximum imaging height of the image source, which is crucial for designing a compact and efficient projection optical engine. A smaller image height means that the optical engine can achieve a smaller size and lighter weight while maintaining image quality, which is especially important for wearable devices.

[0176] In this application, Micro LED is used as the image source 4. Combined with its high brightness, high contrast, and high resolution, the display effect of the projection engine can be significantly improved. This allows users to obtain a clearer and more realistic visual experience when wearing devices such as AR glasses.

[0177] Since projection optical engines are primarily used for imaging in the visible light range, the design of image source parameters needs to ensure good performance within this wavelength range. By precisely controlling pixel size and image height, the image source parameters in this application can ensure high-quality imaging results in the visible light wavelength range.

[0178] According to another embodiment of this application, an optical projection system is provided, the optical projection system comprising:

[0179] The projection optical engine as described in the first aspect; and

[0180] An optical waveguide sheet is used to propagate the projection light emitted from the projection optical engine to the target position for imaging;

[0181] The distance between the exit pupil of the projection optical engine and the entrance pupil of the optical waveguide is 2mm to 5mm.

[0182] The optical projection system provided in this application mainly consists of two parts, as detailed below:

[0183] (1) Projection optical engine: Based on the projection optical engine design in this application, in particular a 0.13″μLED monochrome μLED chip, an Xcube color combining prism and a projection lens 2 including a cemented aspherical lens is adopted;

[0184] (2) Optical waveguide: used to propagate the projection light emitted from the projection optical engine to the target position for imaging, so as to realize the transmission and display of the image.

[0185] Regarding the compatibility between the projection optical engine and the optical waveguide sheet:

[0186] This application specifies that the distance between the exit pupil of the projection optical engine and the entrance pupil of the optical waveguide is 2mm to 5mm. This design constraint is crucial for the integration and imaging quality of the entire optical projection system. A detailed analysis follows:

[0187] In this application, the distance between the exit pupil of the projection optical engine and the entrance pupil of the optical waveguide is 2mm to 5mm. This distance helps to reduce the overall size of the optical projection system, making it more compact and in line with the trend of miniaturization and lightweighting of AR glasses. Furthermore, this distance setting ensures that energy loss and aberrations are minimized during the transmission of light from the projection optical engine to the optical waveguide, thereby guaranteeing the clarity and brightness of the image.

[0188] According to another embodiment of this application, an AR optical display device is provided, the AR optical display device including: a housing and the optical projection system as described above.

[0189] It should be noted that the AR optical display device provided in the embodiments of this application is, for example, an AR head-mounted display device.

[0190] Furthermore, the AR head-mounted display device may be, for example, AR smart glasses or AR smart helmets.

[0191] The specific implementation of the AR optical display device in this application can refer to the above-described embodiments of the projection optical engine and optical projection system. Therefore, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0192] The projection optical engine provided in this application will be specifically described below through Examples 1 and 2.

[0193] Example 1

[0194] See Figure 3 The projection optical engine includes an aperture stop 1, a projection lens 2, a color combining prism 3, and an image source 4. The projection lens 2 and the image source 4 are respectively arranged around the color combining prism 3. The aperture stop 1 is a front aperture stop and is located on the side of the projection lens 2 away from the color combining prism 3.

[0195] The projection lens 2 includes a first lens 21, a second lens 22, a third lens 23, and a fourth lens 24 arranged sequentially. The second lens 22 and the third lens 23 are both aspherical lenses. The second lens 22 and the third lens 23 are cemented together to form a cemented lens, and the cementing surface of the two is aspherical. The first lens 21 is located on one side of the near stop 1, and the fourth lens 24 is located on one side of the color combining prism 3.

[0196] The angle between the tangent at any point on the cemented surface of the cemented lens and the optical axis of the projection lens is α, where 45°≤α≤90°;

[0197] The Abbe number of the second lens 22 is v2, and the Abbe number of the third lens 23 is v3, |v2-v3|>20;

[0198] The refractive index of the second lens 22 is n2, and the refractive index of the third lens 23 is n3, where n2 / n3 > 1.5;

[0199] The first lens 21 is a meniscus lens with positive optical power, the second lens 22 is a biconvex lens with positive optical power, the third lens 23 is a biconcave lens with negative optical power, and the fourth lens 24 is a meniscus lens with positive optical power; the optical power of the cemented lens formed by the second lens 22 and the third lens 23 is positive.

[0200] The projection lens provided in this embodiment 1 has an optical total length of 9.16 mm, an entrance pupil diameter of 3.3 mm, an F number of 2.46, an effective focal length EFFL of 8.3 mm, and a field of view (FOV) of 22°.

[0201] The wavelength of the projected light was set to 455:525:630nm = 1:5:3.

[0202] The dimensions of the image source 4 are 640*480*4μm.

[0203] Table 1 shows the specific optical parameters of the optical projection system in this embodiment 1.

[0204] Table 1

[0205]

[0206]

[0207] The projection optical engine provided in Embodiment 1 has the following optical performance: Figures 4 to 8 As shown:

[0208] Figure 4 The MTF diagram of the projection lens provided in this embodiment 1 shows that the average MTF of each field of view is >0.6, indicating good imaging.

[0209] Figure 5 The optical distortion diagram of the projection lens provided in this embodiment 1 shows that the optical distortion is <1.03%, which is beneficial for image restoration.

[0210] Figure 6 The defocus MTF diagram of the projection lens provided in this embodiment 1 shows that the defocus range of MTF > 0.4 is greater than 0.018mm, which has a large defocus range and is beneficial to assembly and optical mechanism stability.

[0211] Figure 7 The relative illuminance diagram of the projection lens provided in this embodiment 1 shows that the illuminance of the outermost edge relative to the center is >79%, indicating that the brightness of the image image of the projection lens is uniform, the light energy loss at the edge is small, and the utilization rate of the illumination light is high.

[0212] Figure 8 The lateral chromatic aberration diagram of the projection lens provided in this embodiment 1 has a lateral chromatic aberration value of <2μm = 0.5 pixels, which meets the imaging requirements of the projection optical engine.

[0213] Example 2

[0214] See Figure 9 The optical architecture of the projection optical engine shown in this embodiment 2 is the same as that of the projection optical engine shown in embodiment 1 above.

[0215] The projection lens provided in this embodiment 2 has an optical total length of 9.22mm, an entrance pupil diameter of 3.3mm, an F number of 2.44, an effective focal length EFFL of 8.3mm, and a field of view of 22°.

[0216] The wavelengths of the projected light are set to 455:525:630nm = 1:5:3. The dimensions of the image source 4 are 640*480*4μm.

[0217] Table 2 shows the specific optical parameters of the optical projection system in this embodiment 2.

[0218] Table 2

[0219]

[0220]

[0221] The projection optical engine provided in this embodiment 2 has the following optical performance: Figures 10 to 14 As shown:

[0222] Figure 10 The MTF diagram of the projection lens provided in this embodiment 2 shows that the average MTF of each field of view is >0.55, indicating good imaging.

[0223] Figure 11 The optical distortion diagram of the projection lens provided in this embodiment 2 shows that the optical distortion is <1.26%, which is beneficial for image restoration.

[0224] Figure 12 The defocus MTF diagram of the projection lens provided in this embodiment 2 shows that the defocus range of MTF > 0.4 is greater than 0.017mm, which has a large defocus range and is beneficial to assembly and optical mechanism stability.

[0225] Figure 13 The relative illuminance diagram of the projection lens provided in this embodiment 2 shows that the illuminance of the outermost edge relative to the center is >78%, indicating that the brightness of the image image of the lens of this invention is uniform, the light energy loss at the edge is small, and the utilization rate of the illumination light is high.

[0226] Figure 14 The lateral chromatic aberration diagram of the projection lens provided in this embodiment 2 has a lateral chromatic aberration of <2μm = 0.5 pixels, which meets the imaging requirements of the projector.

[0227] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0228] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A projection optical engine, characterized in that, The projection optical engine includes a projection lens (2); The projection lens (2) includes a cemented lens, the cementing surface of the cemented lens is aspherical, and the angle between the tangent at any point on the cementing surface of the cemented lens and the optical axis of the projection lens is α, 45°≤α≤90°; The cemented lens includes a second lens (22) and a third lens (23) arranged along the same optical axis and cemented together. The curvature of the surface of the second lens (22) facing away from the third lens (23) is K1, the curvature of the cemented surface where the second lens (22) and the third lens (23) are bonded together is K2, the curvature of the surface of the third lens (23) facing away from the second lens (22) is K3, and the total effective focal length of the cemented lens is f , 0.05≤(K1+K2+K3) / | f |≤0.3; The projection lens (2) further includes a first lens (21) and a fourth lens (24). The cemented lens is located between the first lens (21) and the fourth lens (24). The first lens (21) is located on the side closer to the second lens (22), and the fourth lens (24) is located on the side closer to the third lens (23). The first lens (21), the second lens (22) and the fourth lens (24) have positive optical power, and the third lens (23) has negative optical power.

2. The projection optical engine according to claim 1, characterized in that, The center thickness of the second lens (22) is T2, and the effective optical aperture of the second lens (22) is L2, 0.25≤T2 / L2≤0.45; The center thickness of the third lens (23) is T3, and the effective optical aperture of the third lens (23) is L3, 0.1≤T3 / L3≤0.

3.

3. The projection optical engine according to claim 1, characterized in that, The Abbe number of the second lens (22) is v2, and the Abbe number of the third lens (23) is v3, |v2-v3|>20.

4. The projection optical engine according to claim 1, characterized in that, The refractive index of the second lens (22) is n2, and the refractive index of the third lens (23) is n3, where n2 / n3 > 1.

5.

5. The projection optical engine according to claim 1, characterized in that, The second lens (22) and the third lens (23) are both aspherical lenses, and the optical power of the cemented lens is positive.

6. The projection optical engine according to claim 1, characterized in that, The first lens (21) is a meniscus lens, the second lens (22) is a biconvex lens, the third lens (23) is a biconcave lens, and the fourth lens (24) is a meniscus lens.

7. The projection optical engine according to claim 1, characterized in that, The total effective focal length (EFL) of the projection lens (2) is 5mm. <EFL<12mm。 8. The projection optical engine according to claim 1, characterized in that, The effective focal length of the first lens (21) is f1.4mm. <f1<12mm; The effective focal length of the second lens (22) is f2, 1mm. <f2<7mm; The effective focal length of the third lens (23) is f3, -8mm. <f3<-0.8mm; The effective focal length of the fourth lens (24) is f4.8mm. <f4<80mm。 9. The projection optical engine according to claim 1, characterized in that, The center thickness of the first lens (21) is T1, 0.3mm < T1 < 1mm; The center thickness of the second lens (22) is T2, 0.5mm < T2 < 1.5mm; The center thickness of the third lens (23) is T3, 0.25mm < T3 < 1mm; The center thickness of the fourth lens (24) is T4, 0.3mm < T4 < 1.2mm.

10. The projection optical engine according to claim 1, characterized in that, The projection optical engine also includes a color combining prism (3) and an image source (4); The projection lens (2) and the image source (4) are respectively disposed on the periphery of the color combining prism (3), wherein the projection lens (2) is located on the light-emitting side of the color combining prism (3); An aperture (1) is provided on the side of the projection lens (2) away from the color-combining prism (3).

11. The projection optical engine according to claim 10, characterized in that, The aperture (1) is the front aperture of the projection optical engine, the first lens (21) is close to the aperture (1), and the fourth lens (24) is far away from the aperture (1). The air gap between the first lens (21) and the aperture (1) is A0, where 0 ≤ A0 < 3 mm; The air gap between the first lens (21) and the second lens (22) is A1, 0.08mm≤A1<1mm; The air gap between the second lens (22) and the third lens (23) is A2, where A2 = 0; The air gap between the third lens (23) and the fourth lens (24) is A3, 0.3mm≤A3<3mm; The air gap between the fourth lens (24) and the color-combining prism (3) is A4, where 0.1mm ≤ A4 < 1mm.

12. The projection optical engine according to claim 11, characterized in that, The radius of curvature of the surface of the first lens (21) near the aperture (1) is R1, 1mm < R1 < 10mm; the radius of curvature of the surface of the first lens (21) near the second lens (22) is R2, R2 < 30mm; The radius of curvature of the surface of the second lens (22) near the first lens (21) is R3, 1mm < R3 < 10mm; the radius of curvature of the cemented surface of the second lens (22) and the third lens (23) is R4, -10mm < R4 < 200mm; the radius of curvature of the surface of the third lens (23) near the fourth lens (24) is R6, 0.8mm < R6 < 8mm; The radius of curvature of the surface of the fourth lens (24) near the third lens (23) is R7, -10mm < R7 < 50mm; the radius of curvature of the surface of the fourth lens (24) near the color-combining prism (3) is R8, -10mm < R8 < -1mm.

13. The projection optical engine according to claim 10, characterized in that, The image source (4) is a Micro LED, and the size of each pixel on the image source (4) is a panel pixel, 2μm < panel pixel < 5μm; The image height H of the image source (4) is: 0 < H ≤ 6 mm.

14. An optical projection system, characterized in that, include: Projection optical engine as described in any one of claims 1-13; and An optical waveguide sheet is used to propagate the projection light emitted from the projection optical engine to the target position for imaging; The distance between the exit pupil of the projection optical engine and the entrance pupil of the optical waveguide is 2mm to 5mm.

15. An AR optical display device, characterized in that, include: shell; and The optical projection system as described in claim 14.

Images