Projection system and optical display device

Abstract

Embodiments of the present application provide a projection system and an optical display device; wherein the projection system comprises a lens group, a prism and a display chip arranged in sequence; wherein the lens group is composed of a first lens, a second lens, a third lens and a fourth lens arranged in sequence, and the refractive index of the first lens, the second lens, the third lens and the fourth lens is >1.6; the refractive index of the prism is <1.55; the projection system satisfies: 1≤TTL / f≤1.5; wherein TTL is the total optical length of the projection system, and f is the effective focal length of the projection system.

Description

Technical Field

[0001] This application relates to the field of optical imaging technology, and more specifically, to a light projection system and an optical display device. Background Technology

[0002] With the rise of the metaverse concept, AR optical display devices are gradually entering people's lives. As one of the key optical components of AR optical display devices, the size, weight, and optical performance of the projection optical engine are crucial to the user experience. In recent years, the rapid development of uLED (MicroLED) technology has provided a new solution for projection optical engines, offering advantages such as small size, low weight, high brightness, and simple structure, gradually becoming the mainstream choice in AR optical display devices.

[0003] However, existing projection optical engines, especially in the field of small FOV (diagonal FOV less than 25°), still face some challenges. For example, how to achieve good optical performance, low temperature drift, and ease of manufacturing while ensuring small size and low weight is a problem that urgently needs to be solved. Summary of the Invention

[0004] The purpose of this application is to provide a new technical solution for a projection system and an optical display device.

[0005] In a first aspect, embodiments of this application provide a projection system. The projection system includes a lens group, a prism, and a display chip arranged sequentially.

[0006] The lens group consists of a first lens, a second lens, a third lens, and a fourth lens arranged sequentially, and the refractive index of the first lens, the second lens, the third lens, and the fourth lens is greater than 1.6.

[0007] The refractive index of the prism is <1.55;

[0008] The projection system satisfies: 1≤TTL / f≤1.5; where TTL is the total optical length of the projection system and f is the effective focal length of the projection system.

[0009] Optionally, the projection system satisfies: [(v1+v2) / 2-(v3+v4) / 2]>20; where v1 is the Abbe number of the first lens, v2 is the Abbe number of the second lens, v3 is the Abbe number of the third lens, and v4 is the Abbe number of the fourth lens.

[0010] Optionally, the Abbe number v1 of the first lens and the Abbe number v2 of the second lens are both greater than 40, and the Abbe number v3 of the third lens and the Abbe number v4 of the fourth lens are both less than 40.

[0011] The prism has an Abbe number of v5, and v5 is greater than 50.

[0012] Optionally, the first lens and the second lens are meniscus positive lenses;

[0013] The third lens is a meniscus negative lens;

[0014] The fourth lens is an aspherical positive lens.

[0015] Optionally, the effective focal length f of the projection system is: 6mm ≤ f ≤ 8mm.

[0016] Optionally, the effective focal length of the first lens is f1, and 2mm. <f1<12mm;

[0017] The center thickness of the first lens is T1, the effective optical aperture of the first lens is L1, and 0.1≤T1 / L1≤0.3.

[0018] Optionally, the effective focal length of the second lens is f2, and 1mm. <f2<11mm;

[0019] The center thickness of the second lens is T2, the effective optical aperture of the second lens is L2, and 0.2≤T2 / L2≤0.4.

[0020] Optionally, the effective focal length of the third lens is f3, and -0.5mm. <f3<-7mm;

[0021] The center thickness of the third lens is T3, the effective optical aperture of the third lens is L3, and 0.05≤T3 / L3≤0.25.

[0022] Optionally, the effective focal length of the fourth lens is f4, 1mm. <f4<11mm;

[0023] The center thickness of the fourth lens is T4, and the effective optical aperture of the fourth lens is L4, where 0.15≤T4 / L4≤0.35.

[0024] Optionally, the thickness of the prism is L, and 3mm. <L<5mm。

[0025] Optionally, the first lens, the second lens, the third lens, the fourth lens, and the prism are made of glass.

[0026] Optionally, the second lens and the third lens are close to each other, and metal spacers are respectively provided between the first lens and the second lens and between the third lens and the fourth lens. The coefficient of thermal expansion of the metal spacers is 22 to 24 × 10⁻⁶. -6 ℃ -1.

[0027] Optionally, the projection system further includes an aperture stop located on the light-emitting side of the first lens;

[0028] The distance between the aperture and the first lens is less than 0.1 mm.

[0029] Optionally, the diameter of the aperture is 3mm to 5mm, which is used to match the entrance pupil diameter of the peripheral optical waveguide device.

[0030] Secondly, embodiments of this application provide an optical display device. The optical display device includes:

[0031] The projection system as described in the first aspect; and

[0032] An optical waveguide device, wherein the diameter of the aperture of the projection system is matched with the entrance pupil diameter of the optical waveguide device.

[0033] The beneficial effects of this application are as follows:

[0034] The projection system provided in this application is optimized for the small FOV (diagonal FOV less than 25°) field, achieving features such as small size, low weight, good optical performance, and ease of manufacturing. By precisely designing the parameters of each lens and using a specific lens combination, the projection system ensures clear image quality, low aberrations, and distortion while maintaining a small size and lightweight design.

[0035] Other features and advantages of this specification will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0036] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of this specification and, together with their description, serve to explain the principles of this specification.

[0037] Figure 1 This is one of the structural schematic diagrams of the projection system provided in the embodiments of this application;

[0038] Figure 2 This is a second schematic diagram of the projection system provided in the embodiments of this application;

[0039] Figure 3 for Figure 2 Field curvature and distortion diagrams of the provided projection system;

[0040] Figure 4 for Figure 2 The provided chromatic aberration diagram of the projection system;

[0041] Figure 5 for Figure 2 A modulation transfer function diagram of the provided projection system;

[0042] Figure 6 for Figure 2 Off-axis curve of the provided projection system at a temperature of 25°C;

[0043] Figure 7 for Figure 2 Off-axis curve of the provided projection system at a temperature of -10°C;

[0044] Figure 8 for Figure 2 Off-axis curve of the provided projection system at a temperature of 70°C;

[0045] Figure 9 This is the third schematic diagram of the projection system provided in the embodiments of this application;

[0046] Figure 10 for Figure 9 Field curvature and distortion diagrams of the provided projection system;

[0047] Figure 11 for Figure 9 The provided chromatic aberration diagram of the projection system;

[0048] Figure 12 for Figure 9 A modulation transfer function diagram of the provided projection system;

[0049] Figure 13 for Figure 9 Off-axis curve of the provided projection system at a temperature of 25°C;

[0050] Figure 14 for Figure 9 Off-axis curve of the provided projection system at a temperature of -10°C;

[0051] Figure 15 for Figure 9 The off-axis curve of the provided projection system at a temperature of 70°C.

[0052] Explanation of reference numerals in the attached figures:

[0053] 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Prism; 6. Display chip; 01. Aperture. Detailed Implementation

[0054] 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.

[0055] 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.

[0056] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0057] 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.

[0058] 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.

[0059] The projection system and optical display device provided in the embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0060] According to one embodiment of this application, a projection system is provided, see [link to relevant documentation]. Figure 1 and Figure 2 The projection system includes a lens group, a prism 5, and a display chip 6 arranged sequentially. The lens group consists of a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4 arranged sequentially, and the refractive index of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 is greater than 1.6. The refractive index of the prism 5 is less than 1.55. The projection system satisfies: 1 ≤ TTL / f ≤ 1.5. Wherein, TTL is the total optical length of the projection system, and f is the effective focal length of the projection system.

[0061] The projection system provided in this application embodiment can be applied in the field of small FOV (e.g., diagonal FOV less than 25°) optical displays. Specifically, the projection system in this application embodiment, in the field of small FOV (e.g., diagonal FOV less than 25°), can achieve characteristics such as small size, low weight, good optical performance, low temperature drift, and ease of production, making it perform well in AR optical display applications.

[0062] The projection system provided in this application embodiment is referred to, see... Figure 1 and Figure 2 The projection system mainly consists of several key optical components arranged in a specific order: a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a prism 5 (i.e., an X-cube color combining prism, used to combine different colors of light into one path), and a display chip 6. The specific refractive indices of these optical components and the TTL / f ratio requirements of the projection system together constitute the core technical features.

[0063] It should be noted that the projection system provided in this application includes a lens group, which may consist of only four lenses. In other words, the projection system provided in this application can achieve small-volume and high-quality imaging using only four lenses.

[0064] Regarding the refractive index requirements of each lens in the lens group of the projection system of this application:

[0065] The lens group of this application consists of four lenses, specifically lenses 1 through 4 arranged sequentially, with the refractive index of each of the first lens 1, second lens 2, third lens 3, and fourth lens 4 greater than 1.6. This refractive index design indicates that these lenses are made of a high-refractive-index material. High-refractive-index materials help reduce the physical size of the lenses while maintaining their optical performance. This is crucial for designing miniaturized and compact projection systems.

[0066] Regarding the refractive index requirements of the prism 5 in the projection system of this application:

[0067] The refractive index of the prism 5 in this application is set to be less than 1.55. The refractive index of the prism 5 is different from that of the four lenses in the above-mentioned lens group. The prism 5 is made of a low refractive index material. This combination helps to reduce chromatic aberration and aberration, and also helps to reduce the overall weight and cost of the entire projection system.

[0068] It should be noted that the prism 5 is an X-cube color combining prism, see [link / reference]. Figure 1 It is used to synthesize light of different colors into a single beam. This synthesized light then passes sequentially through the fourth lens 4, the third lens 3, and the second lens 2, and finally exits through the first lens 1. This process ensures the precise synthesis and transmission of light of different colors.

[0069] See Figure 1 , Figure 1 The working mechanism of the display chip 6 is demonstrated: it emits red, blue, and green light respectively, which are then combined into a single beam by the prism 5 (X-cube color combining prism) through a specially designed optical path. This process demonstrates the precise control of color synthesis throughout the projection system.

[0070] Figure 2 for Figure 1 A simplified representation, which intuitively shows how the light emitted from the display chip 6 directly enters the prism 5 and exits after being processed by the prism 5. Although Figure 2 While some details have been omitted, it still clearly conveys the core process of light synthesis and transmission, making it easy to quickly understand the basic working principle of the entire projection system.

[0071] The projection system provided in this application satisfies the condition: 1 ≤ TTL / f ≤ 1.5; where TTL is the total optical length of the projection system and f is the effective focal length of the projection system. This ratio requirement ensures that the projection system can provide sufficient optical performance while maintaining a compact structure.

[0072] The TTL / f ratio is an important indicator of the balance between compactness and optical performance in a projection system. A smaller TTL / f value means a more compact system.

[0073] The projection system provided in this application achieves significant miniaturization and compactness by employing high-refractive-index lens materials and low-refractive-index prism materials, combined with specific TTL / f ratio requirements. This is crucial for wearable devices requiring a compact structure, such as AR glasses.

[0074] The projection system for the cabinet in this application embodiment, despite its reduced overall system size, maintains excellent optical performance through precise optical parameter design and material selection. This includes clear image quality, low aberrations, and distortion.

[0075] In summary, this application, through specific lens and prism refractive index requirements and TTL / f ratio requirements, achieves a miniaturized, compact, and optically superior small FOV projection system. These technical features collectively provide strong technical support for the development of wearable devices.

[0076] It should be noted that the projection system provided in this application embodiment is a core component of the projection optical engine.

[0077] In some examples of this application, the projection system satisfies: [(v1+v2) / 2-(v3+v4) / 2]>20; where v1 is the Abbe number of the first lens 1, v2 is the Abbe number of the second lens 2, v3 is the Abbe number of the third lens 3, and v4 is the Abbe number of the fourth lens 4.

[0078] In this example of the application, the projection system is designed to satisfy a specific Abbe number condition: [(v1+v2) / 2-(v3+v4) / 2]>20; in this condition, v1, v2, v3, and v4 represent the Abbe numbers of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4, respectively. It should be noted that the Abbe number is an important parameter describing the dispersion capability of a lens material, and it is closely related to the imaging quality of the lens.

[0079] In this example of the application, the chromatic dispersion correction of the projection system is optimized by setting the condition [(v1+v2) / 2-(v3+v4) / 2]>20. See also Figure 1 and Figure 2 This condition requires that the average Abbe number of the first two lenses in the lens group, namely the first lens 1 and the second lens 2, must be significantly higher than the average Abbe number of the last two lenses, namely the third lens 3 and the fourth lens 4.

[0080] To meet the above conditions, the selection of lens material becomes crucial.

[0081] Materials with high Abbe numbers have lower dispersion, which reduces color deviation when light passes through a lens. Therefore, the first lens 1 and the second lens 2 are made of glass or special optical materials with high Abbe numbers to ensure good dispersion correction. The third lens 3 and the fourth lens 4 are made of materials with lower Abbe numbers, but these materials have advantages in other aspects such as refractive index, cost, or processing performance.

[0082] In the projection system of this application, the combination of different lenses has a crucial impact on its optical performance. In particular, the Abbe number of the lens is directly related to the dispersion correction capability of the projection system.

[0083] Transverse chromatic aberration refers to the phenomenon that when light of different wavelengths passes through a lens system, the focal point deviates not only in the axial direction (i.e., the optical axis direction) but also in the transverse direction (i.e., the direction perpendicular to the optical axis).

[0084] By carefully designing the Abbe number of the lenses to meet the conditions in this example, the transverse chromatic aberration of the projection system can be effectively corrected. Specifically, high Abbe number lenses, namely the first lens 1 and the second lens 2, can reduce the focal point deviation of short-wavelength light in the transverse direction, while low Abbe number lenses, namely the third lens 3 and the fourth lens 4, may have a better correction effect on long-wavelength light. The combination of these two can balance and reduce transverse chromatic aberration to a certain extent. A projection system that meets this condition can significantly reduce transverse chromatic aberration, thereby improving image sharpness and color accuracy. This is particularly important for applications requiring high image quality, such as AR glasses.

[0085] Furthermore, by appropriately combining lens materials with different Abbe numbers, excellent optical performance can be achieved while maintaining the miniaturization and compactness of the projection system.

[0086] Therefore, the condition [(v1+v2) / 2-(v3+v4) / 2]>20 is an effective means of reducing transverse chromatic aberration by carefully selecting the Abbe number of the lens. It helps improve the imaging quality and color accuracy of the projection system, providing a superior optical solution for applications such as AR glasses.

[0087] Based on the example provided in this application, at least the following technical effects can be achieved:

[0088] (1) Improved color reproduction: By precisely controlling the Abbe number of each lens, the projection system can significantly reduce color deviation, thereby improving color reproduction and image clarity.

[0089] (2) Miniaturization and compactness: Although the choice of Abbe number imposes certain limitations on lens materials, the projection system can maintain the advantages of miniaturization and compactness through reasonable optical design and material matching.

[0090] In summary, this example optimizes color correction in a projection system by setting specific Abbe number conditions. This technical feature not only improves color reproduction and image sharpness but also provides strong support for overall system performance optimization.

[0091] In some examples of this application, the Abbe number v1 of the first lens 1 and the Abbe number v2 of the second lens 2 are both greater than 40, the Abbe number v3 of the third lens 3 and the Abbe number v4 of the fourth lens 4 are both less than 40; the Abbe number of the prism 5 is v5, and v5 is greater than 50.

[0092] In this example of the application, the four lenses and one prism in the lens group of the projection system are assigned specific Abbe number requirements. Specifically, the Abbe numbers of the first lens 1 and the second lens 2 are both greater than 40, while the Abbe numbers of the third lens 3 and the fourth lens 4 are both less than 40. The Abbe number of the prism 5 is required to be greater than 50. The following is an analysis of this example of the application and a description of its technical effects.

[0093] High Abbe number lens (v1, v2 > 40):

[0094] The first lens 1 and the second lens 2 are made of high Abbe number materials, meaning they have a strong ability to correct for chromatic aberration. Chromatic aberration is a phenomenon that occurs during lens imaging, causing light of different wavelengths to focus at different positions, thus affecting image sharpness. High Abbe number lenses can reduce this chromatic aberration effect, making the colors in the image more accurate and clearer.

[0095] The Abbe numbers v1 and v2 of the first lens 1 and the second lens 2 are both greater than 40. High Abbe number lenses are very effective in reducing chromatic aberration. Therefore, using the first lens 1 and the second lens 2 with high Abbe numbers helps to reduce the chromatic aberration of short-wavelength light (such as blue light), thereby reducing transverse chromatic aberration.

[0096] Low Abbe number lens (v3, v4 < 40):

[0097] In contrast, the third lens 3 and the fourth lens 4 are made of low Abbe number materials. Low Abbe number materials may have a higher refractive index, which helps to further reduce the size and weight of the lens. In addition, through proper optical design, the dispersion introduced by the low Abbe number lens can be compensated for to some extent.

[0098] The Abbe numbers v3 and v4 of the third lens 3 and the fourth lens 4 are both less than 40: although low Abbe number lenses are not as effective as high Abbe number lenses in reducing chromatic aberration, in certain combinations, they can be used in conjunction with high Abbe number lenses to balance the overall system's dispersion correction. This combination may help reduce dispersion of long-wavelength light (such as red light), further reducing transverse chromatic aberration.

[0099] The Abbe number v5 of prism 5 is greater than 50, indicating that it also has excellent dispersion correction capabilities. In projection systems, prisms are commonly used to synthesize light of different colors. By using prism materials with high Abbe numbers, it is possible to ensure that the synthesized light has more accurate and consistent colors.

[0100] The prism 5 is typically used in projection systems to combine or redirect light beams. Using a high Abbe number prism reduces chromatic dispersion as light propagates within the prism 5, thus maintaining high light quality and color accuracy. This is also important for reducing transverse chromatic aberration.

[0101] From the perspective of reducing transverse chromatic aberration, this Abbe number combination design of lens and prism has significant technical advantages:

[0102] (1) Balanced dispersion correction: By combining high Abbe number and low Abbe number lenses, the projection system can achieve more balanced dispersion correction at different wavelengths, thereby reducing transverse chromatic aberration.

[0103] (2) Improve image quality: Reducing chromatic aberration means that light of different wavelengths can be focused more accurately on the same plane, thereby improving the clarity and color accuracy of the image.

[0104] (3) Optimize overall system performance: This combination of Abbe numbers provides greater flexibility in system design, allowing for miniaturization and compactness while achieving excellent optical performance.

[0105] See some examples in this application. Figure 1 and Figure 2 The first lens 1 and the second lens 2 are meniscus positive lenses, the third lens 3 is a meniscus negative lens, and the fourth lens 4 is an aspherical positive lens.

[0106] In some examples of this application, the lens group in the projection system employs a specific type of lens combination, namely, the first lens 1 and the second lens 2 are meniscus positive lenses, the third lens 3 is a meniscus negative lens, and the fourth lens 4 is an aspherical positive lens.

[0107] The first lens 1 and the second lens 2 are meniscus positive lenses. One surface of a meniscus lens is convex, and the other surface is concave. This shape helps correct aberrations. As positive lenses, they converge light, helping to accurately project light from the display chip 6 onto the target plane.

[0108] The third lens 3 is a meniscus negative lens. While also employing a meniscus design, as a negative lens, it diverges light. In projection systems, negative lenses are used to correct system aberrations, particularly field curvature and distortion, thereby improving image smoothness and accuracy.

[0109] The fourth lens is an aspherical positive lens. While converging light rays, its aspherical design further reduces aberrations and improves image quality.

[0110] By employing the above lens combination, the projection system can effectively correct various aberrations, such as spherical aberration, coma, field curvature, and distortion, thereby improving the clarity and accuracy of the image.

[0111] The lens combination used in the curved lens application—a meniscus positive lens, a meniscus negative lens, and an aspherical positive lens—significantly improves the imaging quality and performance of the projection system through its unique design characteristics and combination method.

[0112] The projection system provided in this application embodiment has the following refractive power order: positive, positive, negative, positive. The surface shapes of the first lens 1 to the fourth lens 4 are, in order: convex-concave lens, convex-concave lens, convex-concave lens, and aspherical lens.

[0113] In some examples of this application, the effective focal length f of the projection system is: 6mm ≤ f ≤ 8mm.

[0114] In this example of the application, the effective focal length f of the projection system is set in the range of 6mm to 8mm. This specific focal length selection is based on a comprehensive consideration of factors such as the performance, size, weight, and image quality of the projection system.

[0115] The choice of focal length has a direct impact on image quality. Within the focal length range of 6mm to 8mm, the projection system can effectively correct aberrations, thereby ensuring image sharpness and accuracy.

[0116] For portable devices such as AR glasses, the volume and weight of the projection system are crucial considerations. A smaller focal length helps reduce the diameter and thickness of the lens, thereby decreasing the volume and weight of the entire projection system, making it more suitable for integration into small devices such as AR glasses.

[0117] It should be emphasized that this application is directed to a projection system with a small FOV (diagonal FOV less than 25 degrees). At a smaller focal length, the projection system can provide a sufficient field of view to meet application requirements while maintaining compactness.

[0118] The choice of focal length also affects the management of light. At a smaller focal length, the divergence angle of the light after passing through the lens is larger, which helps project the light more evenly onto the target plane, improving the brightness and uniformity of the image.

[0119] In summary, the effective focal length f of the projection system in this application is set within the range of 6 mm to 8 mm, based on a comprehensive consideration of imaging quality, system volume and weight, field of view, and light management. This focal length selection provides excellent performance for the projection system, making it a small, lightweight, and high-quality color projection solution.

[0120] In some examples of this application, the effective focal length of the first lens 1 is f1, and 2 mm < f1 < 12 mm; the central thickness of the first lens 1 is T1, the optical effective aperture of the first lens 1 is L1, and 0.1 ≤ T1 / L1 ≤ 0.3.

[0121] In this example of this application, the effective focal length f1 of the first lens 1 is set within the range of 2 mm to 12 mm. At the same time, the ratio of the central thickness T1 to the optical effective aperture L1 of the first lens 1 is limited between 0.1 and 0.3. Specifically, the focal length range of 2 mm to 12 mm allows the first lens 1 to maintain a small volume and weight while providing sufficient imaging ability, which is crucial for miniaturized applications such as AR glasses. And the ratio control of thickness to aperture: T1 / L1 helps ensure the mechanical stability and optical performance of the first lens 1. An appropriate ratio can prevent the first lens 1 from being easily damaged due to being too thin or increasing unnecessary weight and volume due to being too thick.

[0122] In some examples of this application, the effective focal length of the second lens 2 is f2, and 1 mm < f2 < 11 mm; the central thickness of the second lens 2 is T2, the optical effective aperture of the second lens 2 is L2, and 0.2 ≤ T2 / L2 ≤ 0.4.

[0123] The effective focal length f2 of the second lens 2 is set within the range of 1 mm to 11 mm, and the ratio of the central thickness T2 to the optical effective aperture L2 is limited between 0.2 and 0.4. It should be noted that similar to the first lens 1, the focal length range of the second lens is also designed to achieve a balance between miniaturization and high performance. Compared with the first lens 1, the T2 / L2 ratio range of the second lens 2 is narrower, which helps to further precisely control the size and weight of the lens while maintaining its optical performance.

[0124] In some examples of the present application, the effective focal length of the third lens 3 is f3, and -0.5 mm < f3 < -7 mm; the central thickness of the third lens 3 is T3, the optical effective aperture of the third lens 3 is L3, and 0.05 ≤ T3 / L3 ≤ 0.25.

[0125] The effective focal length f3 of the third lens 3 is set to be negative, within the range of -0.5 mm to -7 mm, and the ratio of the central thickness T3 to the optical effective aperture L3 of the third lens 3 is limited between 0.05 and 0.25. Specifically, the third lens 3 with a negative focal length helps to achieve aberration correction of the projection system, especially the correction of field curvature and distortion, thereby improving the imaging quality. In addition, although it has a negative focal length, by controlling the ratio of T3 / L3, the third lens 3 can still maintain a small volume and weight.

[0126] In some examples of the present application, the effective focal length of the fourth lens 4 is f4, 1 mm < f4 < 11 mm; the central thickness of the fourth lens 4 is T4, the optical effective aperture of the fourth lens 4 is L4, and 0.15 ≤ T4 / L4 ≤ 0.35.

[0127] The effective focal length f4 of the fourth lens 4 is set within the range of 1 mm to 11 mm, and the ratio of the central thickness T4 to the optical effective aperture L4 of the fourth lens is limited between 0.15 and 0.35. Specifically, the focal length range of the fourth lens 4 allows it to provide sufficient imaging ability while maintaining a small volume and weight. And the control of the ratio of T4 / L4 helps to ensure the mechanical stability and optical performance of the fourth lens 4.

[0128] In some examples of the present application, the thickness of the prism 5 is L, and 3 mm < L < 5 mm.

[0129] The thickness range of the prism 5 helps to maintain the miniaturization and light weight of the prism, which is crucial for miniaturized applications such as AR glasses.

[0130] Combining the above five examples (the first lens 1 to the fourth lens 4 and the prism 5), it can be seen that the projection system of the present application has optimized technical effects in multiple aspects:

[0131] By precisely controlling the focal length, thickness, and aperture ratio of the four lenses, as well as the thickness of prism 5, the entire projection system can maintain a small size and weight, making it ideal for integration into small devices such as AR glasses. Appropriate lens thickness and aperture ratio control prevents lenses from being easily damaged due to being too thin, or from adding unnecessary weight and size due to being too thick. At the same time, the stability and durability of the prism are also guaranteed.

[0132] In some examples of this application, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, and the prism 5 are made of glass.

[0133] The projection system provided in this application embodiment is made of glass material, including four lenses and one prism 5.

[0134] Glass has excellent optical transparency, which reduces light scattering and absorption inside the lens, thereby improving image sharpness and contrast. Furthermore, the refractive index and dispersion characteristics of glass lenses are relatively stable, helping to reduce chromatic aberration and other aberrations, further enhancing image quality.

[0135] Glass has a relatively low coefficient of thermal expansion and good thermal conductivity, so lenses made of glass are less prone to deformation when temperatures change, maintaining stable optical performance. This is especially important for applications such as AR glasses that need to operate for extended periods or in varying temperature environments, reducing image quality degradation caused by temperature variations.

[0136] Glass has high hardness and toughness, which can resist external impacts and wear, thus extending the lifespan of the lens. This is especially beneficial for applications such as AR glasses that are frequently exposed to the external environment, reducing lens damage caused by accidental collisions or abrasions.

[0137] Because all lenses and prisms in the projection system are made of glass, their coefficients of thermal expansion and physical properties are relatively consistent, which helps reduce system instability and performance degradation caused by material differences. This is crucial for ensuring the stability and reliability of the entire projection system, providing users with a more stable and reliable imaging experience.

[0138] In summary, using glass as the material for the first lens 1, second lens 2, third lens 3, fourth lens 4, and prism 5 can significantly improve the optical performance, thermal stability, mechanical strength, and overall system stability of the projection system. These advantages make this projection system more suitable for miniaturized, high-performance applications such as AR glasses.

[0139] In some examples of this application, the second lens 2 and the third lens 3 are close to each other, and metal spacers are respectively provided between the first lens 1 and the second lens 2 and between the third lens 3 and the fourth lens 4. The coefficient of thermal expansion of the metal spacers is 22 to 24 × 10⁻⁶. -6 ℃ -1 .

[0140] The second lens 2 and the third lens 3 are designed to be close to each other. At the same time, metal spacers with a thermal expansion coefficient of 22 to 24 × 10^-6℃-1, such as aluminum alloy spacers, are respectively provided between the first lens 1 and the second lens 2 and between the third lens 3 and the fourth lens 4.

[0141] The close proximity of the second lens 2 and the third lens 3 helps to reduce the gap between the lens assemblies, thereby reducing the overall size of the projection system.

[0142] An aluminum alloy spacer is introduced between the first lens 1 and the second lens 2, and an aluminum alloy spacer is also introduced between the third lens 3 and the fourth lens 4. By precisely controlling thermal expansion, the lens displacement caused by temperature changes can be reduced, thereby reducing the temperature drift of the system and ensuring the stability of imaging.

[0143] Aluminum alloy spacers not only possess stable thermal expansion properties but also exhibit high strength and toughness. They effectively support and protect the lens, preventing lens displacement or damage caused by external impacts or vibrations, thereby improving the stability and reliability of the entire projection system.

[0144] By reducing imaging deviations caused by temperature changes or external interference, the clarity and contrast of the projection system can be improved, providing users with a better visual experience.

[0145] In summary, by setting a coefficient of thermal expansion of 22 to 24 × 10⁻⁶ between the first lens 1 and the second lens 2, and between the third lens 3 and the fourth lens 4, -6 ℃ -1 The metal spacer ring and the design of the second lens 2 and the third lens 3 being close to each other have achieved significant technical effects in reducing volume and weight, controlling thermal expansion, improving system stability, optimizing imaging quality, and simplifying assembly and debugging.

[0146] See some examples in this application. Figure 1 and Figure 2 The projection system further includes an aperture stop 01, which is located on the light-emitting side of the first lens 1; the distance between the aperture stop 01 and the first lens 1 is less than 0.1 mm.

[0147] See Figure 1 and Figure 2 The projection system of this application also includes an aperture stop 01, which is located on the light-emitting side of the first lens 1. Specifically, the distance between the aperture stop 01 and the front surface of the first lens 1 is controlled to be less than 0.1 mm. The close spacing between the aperture stop 01 and the first lens 1 helps to reduce the overall size of the projection system. Furthermore, the close spacing reduces light scattering and loss between the aperture stop and the lens, thereby improving light utilization efficiency. This helps to enhance the brightness and contrast of the projection system and improve image quality.

[0148] In some examples of this application, the diameter of the aperture 01 is 3mm to 5mm, which is used to match the entrance pupil diameter of the optical waveguide device of the peripheral.

[0149] In this example of the application, the diameter of the aperture 01 is 3mm to 5mm, a size range specifically designed to match the entrance pupil diameter of the peripheral optical waveguide device.

[0150] For AR technology, the light emitted from the projection system needs to be transmitted to the human eye for imaging through an optical waveguide device.

[0151] In this application, the aperture stop 01 is used to control the exit pupil diameter of the projection system. The diameter of the aperture stop 01 matches the entrance pupil diameter of the peripheral optical waveguide device, which helps reduce light loss during coupling and improves coupling efficiency. This helps ensure that the light emitted by the projection system can be efficiently transmitted to the optical waveguide device and thus presented to the user.

[0152] The diameter range of the aperture 01 provided in this application can match the entrance pupil size of most optical waveguide devices.

[0153] The projection system of this application has significant technical advantages, mainly reflected in the following aspects:

[0154] (1) Small size and lightweight:

[0155] By employing a combination of four high-refractive-index lenses (refractive index > 1.6) and one low-refractive-index prism (refractive index < 1.55), and optimizing the TTL / f ratio (1 ≤ TTL / f ≤ 1.5), the projection system has been miniaturized and made lightweight, making it suitable for wearable devices such as AR glasses.

[0156] (2) Good optical performance:

[0157] The projection system of this application, while maintaining a small size, ensures clear image quality, low aberrations and distortion, and improves overall optical performance by precisely designing the parameters and combinations of each lens.

[0158] (3) Small temperature drift characteristics:

[0159] By using materials with stable coefficients of thermal expansion (such as glass lenses and specific metal spacers) and optimizing the design structure, the impact of temperature changes on the imaging quality of the projection system is effectively reduced, and the system's temperature drift control capability is improved.

[0160] (4) High color fidelity:

[0161] By setting specific Abbe number conditions (such as [(v1+v2) / 2-(v3+v4) / 2]>20), the dispersion correction capability of the four lens materials was optimized, significantly reducing color deviation and improving color reproduction and image clarity.

[0162] The projection system described in this application is suitable for optical display applications with small FOV (diagonal FOV less than 25°), such as AR glasses. At different temperatures (e.g., -10℃, 25℃, 70℃), the off-axis curve of the projection system maintains good consistency, indicating that it has good imaging stability and can provide stable imaging quality under various environmental conditions.

[0163] In summary, the projection system of this application exhibits significant technical advantages in terms of size, weight, optical performance, temperature drift control, color reproduction, manufacturing difficulty, and application prospects.

[0164] According to another embodiment of this application, an optical display device is also provided, the optical display device including a projection system and an optical waveguide device as described above, wherein the diameter of the aperture 01 of the projection system matches the entrance pupil diameter of the optical waveguide device.

[0165] In another embodiment of this application, an optical display device is provided that integrates the aforementioned projection system and optical waveguide device. Specifically, the diameter of the aperture 01 of the projection system is designed to match the entrance pupil diameter of the optical waveguide device.

[0166] The precise matching of the diameter of the aperture 01 with the entrance pupil diameter of the optical waveguide device of the optical display device ensures that the light emitted by the projection system can be efficiently coupled into the optical waveguide device. This efficient coupling reduces light loss and improves the overall brightness of the optical display device.

[0167] The exit pupil diameter of the projection system matches the entrance pupil diameter of the optical waveguide device, which helps maintain the collimation and focusing of the light, thereby avoiding image blurring and distortion caused by light scattering or defocusing. This provides users with a clearer visual experience.

[0168] By precisely matching the aperture diameter of the projection system and the entrance pupil diameter of the optical waveguide device, the stability of the entire optical display system can be enhanced. This helps ensure that the system provides stable imaging performance in various operating environments.

[0169] Optical display devices that integrate high-efficiency projection systems and optical waveguide devices can provide users with clearer images and a more comfortable wearing experience. This is especially important for miniaturized and lightweight optical display devices such as AR glasses.

[0170] The present application will be described in detail below through Examples 1 and 2.

[0171] Example 1

[0172] See Figure 2 The projection system consists of a lens group, a prism 5, and a display chip 6 arranged in sequence; wherein the lens group consists of a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4 arranged in sequence.

[0173] The first lens 1 is a meniscus positive lens with an effective focal length f1 of 6.66 mm and is made of glass; the second lens 2 is a meniscus positive lens with an effective focal length f2 of 4.83 mm and is made of glass; the third lens 3 is a meniscus negative lens with an effective focal length f3 of -1.81 mm and is made of glass; the fourth lens 4 is an aspherical positive lens with an effective focal length f4 of 5.53 mm and is made of glass.

[0174] The fifth lens is an X-cube with a thickness L of 3.6 mm and is made of glass.

[0175] The display chip 6 is a micro light-emitting diode display panel (Micro LED);

[0176] The projection system has an optical total length (TTL) of 8mm, an effective focal length (f) of 7.03mm, a half-image height of 1.25mm, a half-field of view of 10°, and an aperture number (F#) of 2.01.

[0177] The optical parameters of each lens and prism in the projection system provided in Example 1 are shown in Table 1.

[0178] Table 1

[0179]

[0180]

[0181] The even-order aspherical surfaces satisfy the following relationship:

[0182]

[0183] Where Y is the center height of the fourth lens 4, Z is the displacement of the aspherical structure at a height of Y along the optical axis, with the vertex of the surface as a reference, C is the vertex radius of curvature of the aspherical surface, K is the conic coefficient, and αi represents the aspherical coefficient of the i-th order. Please refer to Table 2 for the optical parameters of the fourth lens 4.

[0184] Table 2

[0185] Surface serial number Conic coefficient k α2 α3 α4 8 3.12 -0.028 2.064E-03 -0.011 9 100 -0.013 -1.105E-03 -7.723E-03

[0186] For the optical performance of the projection system provided in Embodiment 1 of this application, please refer to [link to documentation]. Figures 3 to 8 :

[0187] See Figure 3 : Figure 3 The diagram shown depicts the field curvature and optical distortion of the projection system. From... Figure 3 As can be seen, the projection system of Embodiment 1 of this application performs well in terms of field curvature and distortion, and the image maintains high clarity and flatness throughout the entire field of view.

[0188] See Figure 4 : Figure 4 The diagram shown is a transverse chromatic aberration diagram of the projection system. Transverse chromatic aberration refers to the phenomenon where light of different wavelengths forms image points at different heights on the imaging plane, resulting in colored edges in the image. Figure 4 The image shows the distribution of light of different wavelengths on the imaging plane. It can be seen that the projection system controls the transverse chromatic aberration well, and the image points formed by light of different wavelengths are relatively concentrated, which helps to reduce color deviation in the image.

[0189] See Figure 5 : Figure 5 The diagram shows the modulation transfer function (MTF) of the projection system. MTF measures the projection system's ability to transfer contrast at different spatial frequencies. The closer the MTF curve is to 1, the stronger the contrast transfer capability of the projection system and the higher the image quality. Figure 5 The figure shows the MTF values ​​of the projection system at different spatial frequencies. It can be seen that the projection system of this embodiment 1 maintains a high MTF value at multiple spatial frequencies, indicating that it has good contrast transfer capability and imaging quality.

[0190] See Figures 6 to 8 Off-axis projection curves are shown at temperatures of 25°C, -10°C, and 70°C. These curves describe the distribution of off-axis light rays on the imaging plane at different temperatures. Changes in the off-axis curves reflect the imaging stability of the lens at different temperatures.

[0191] From 6 in the figure Figure 8As can be seen, the off-axis curves of Example 1 maintained good consistency under different temperatures, indicating that it has good temperature drift control capabilities. This helps ensure that the projection system can provide stable imaging quality under different ambient temperatures.

[0192] In summary, the projection system of Embodiment 1 exhibits excellent optical performance, featuring low field curvature and distortion, good transverse chromatic aberration control, high contrast transfer capability, and superior temperature drift control. These advantages make this projection system highly suitable for applications with high optical performance requirements, such as AR glasses.

[0193] Example 2

[0194] See Figure 9 The projection system consists of a lens group, a prism 5, and a display chip 6 arranged in sequence; wherein the lens group consists of a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4 arranged in sequence.

[0195] The first lens 1 is a meniscus positive lens with an effective focal length f1 of 8.42 mm and is made of glass; the second lens 2 is a meniscus positive lens with an effective focal length f2 of 5.8 mm and is made of glass; the third lens 3 is a meniscus negative lens with an effective focal length f3 of -2.67 mm and is made of glass; the fourth lens 4 is an aspherical positive lens with an effective focal length f4 of 7.65 mm and is made of glass.

[0196] The fifth lens is an X-cube with a thickness L of 3.6 mm and is made of glass.

[0197] The display chip 6 is a micro light-emitting diode display panel (Micro LED);

[0198] The projection system has an optical total length (TTL) of 8.52 mm, an effective focal length (f) of 7.08 mm, a half-image height of 1.25 mm, a half-field of view of 10°, and an aperture number (F#) of 1.76.

[0199] The optical parameters of each lens and prism in the projection system provided in Example 2 are shown in Table 3.

[0200] Table 3

[0201]

[0202] The even-order aspherical surfaces satisfy the following relationship:

[0203]

[0204] Where Y is the center height of the fourth lens 4, Z is the displacement of the aspherical structure at a height of Y along the optical axis, with the vertex of the surface as a reference, C is the vertex radius of curvature of the aspherical surface, K is the conic coefficient, and αi represents the aspherical coefficient of the i-th order. Please refer to Table 4 for the optical parameters of the fourth lens 4.

[0205] Table 4

[0206]

[0207]

[0208] For the projection system provided in Embodiment 2 of this application, please refer to [link to documentation]. Its optical performance is also described in [link to documentation]. Figures 10 to 15 :

[0209] See Figure 10 : Figure 10 The diagram illustrates the field curvature and optical distortion of the projection system. Field curvature represents the degree of image bending at different viewing angles on the imaging plane, while distortion represents the degree of image distortion relative to its ideal shape. Figure 10 As can be seen, field curvature and distortion are both controlled at a low level, indicating that the projection system provided in this embodiment 2 can provide a relatively flat and accurate image, which is crucial for enhancing the user's visual experience.

[0210] See Figure 11 : Figure 11 The diagram shows the transverse chromatic aberration of the projection system. Transverse chromatic aberration refers to the phenomenon where light of different wavelengths forms image points at different heights on the imaging plane, resulting in colored stripes at the image edges. Figure 11 This demonstrates the distribution of light of different wavelengths on the imaging plane. It can be seen that transverse chromatic aberration is effectively controlled, and the image points formed by light of different wavelengths are relatively concentrated, which helps reduce color deviation in the image and improve color reproduction.

[0211] See Figure 12 : Figure 12 The modulation transfer function (MTF) diagram of the projection system is shown. From... Figure 12 As can be seen, the MTF curve remains at a high level at different spatial frequencies, indicating that the projection system provided in this embodiment 2 has good contrast transmission capability and can present clear and delicate images.

[0212] See Figures 13 to 15 The off-axis curves at temperatures of 25°C, -10°C, and 70°C show the off-axis light distribution of the lens at different temperatures, reflecting the temperature drift performance of the projection system.

[0213] Figure 13(25℃): Under normal temperature conditions, the off-axis curve remains stable, indicating that the projection system has good imaging performance at this temperature.

[0214] Figure 14 (-10℃): Under low temperature conditions, the off-axis curve fluctuates slightly, but remains stable overall, indicating that the projection system can provide reliable imaging quality even in low temperature environments.

[0215] Figure 15 (70℃): The off-axis curve remains stable under high temperature conditions, indicating that the projection system can maintain good temperature drift control capability in high temperature environments.

[0216] In summary, the projection system provided in this embodiment 2 exhibits good stability in its off-axis curves at different temperatures, which helps ensure that the projection system can provide stable imaging quality under various environmental conditions.

[0217] In summary, the projection system of Embodiment 2 also demonstrates excellent optical performance. Through field curvature and distortion diagrams, transverse chromatic aberration diagrams, MTF diagrams, and off-axis curves at different temperatures, the imaging quality, color reproduction, contrast transfer capability, and temperature drift control of this projection system can be comprehensively evaluated. These graphical data provide strong support for the performance verification and optimization of the projection system.

[0218] 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.

[0219] 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 system, characterized in that, It includes a lens group, a prism (5) and a display chip (6) arranged in sequence; The lens group consists of a first lens (1), a second lens (2), a third lens (3) and a fourth lens (4) arranged in sequence, and the refractive index of the first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) is greater than 1.6; The refractive index of the prism (5) is <1.55; The projection system satisfies: 1≤TTL / f≤1.5; where TTL is the total optical length of the projection system and f is the effective focal length of the projection system. The center thickness of the first lens (1) is T1, the effective optical aperture of the first lens (1) is L1, and 0.1≤T1 / L1≤0.3; The center thickness of the second lens (2) is T2, the effective optical aperture of the second lens (2) is L2, and 0.2≤T2 / L2≤0.4; The center thickness of the third lens (3) is T3, the effective optical aperture of the third lens (3) is L3, and 0.05≤T3 / L3≤0.25; The center thickness of the fourth lens (4) is T4, and the effective optical aperture of the fourth lens (4) is L4, 0.15≤T4 / L4≤0.35; The second lens (2) and the third lens (3) are close to each other, and metal spacers are respectively provided between the first lens (1) and the second lens (2) and between the third lens (3) and the fourth lens (4). The coefficient of thermal expansion of the metal spacers is 22 to 24 × 10⁻⁶. -6 ℃ -1 .

2. The projection system according to claim 1, characterized in that, The projection system satisfies: [(v1+v2) / 2-(v3+v4) / 2]>20; Wherein, v1 is the Abbe number of the first lens (1), v2 is the Abbe number of the second lens (2), v3 is the Abbe number of the third lens (3), and v4 is the Abbe number of the fourth lens (4).

3. The projection system according to claim 2, characterized in that, The Abbe number v1 of the first lens (1) and the Abbe number v2 of the second lens (2) are both greater than 40, while the Abbe number v3 of the third lens (3) and the Abbe number v4 of the fourth lens (4) are both less than 40. The Abbe number of the prism (5) is v5, and v5 is greater than 50.

4. The projection system according to claim 1, characterized in that, The first lens (1) and the second lens (2) are meniscus positive lenses; The third lens (3) is a meniscus negative lens; The fourth lens (4) is an aspherical positive lens.

5. The projection system according to claim 1, characterized in that, The effective focal length f of the projection system is: 6mm≤f≤8mm.

6. The projection system according to claim 4, characterized in that, The effective focal length of the first lens (1) is f1, and 2mm. <f1<12mm。 7. The projection system according to claim 6, characterized in that, The effective focal length of the second lens (2) is f2, and 1mm. <f2<11mm。 8. The projection system according to claim 7, characterized in that, The effective focal length of the third lens (3) is f3, and -0.5mm. <f3<-7mm。 9. The projection system according to claim 8, characterized in that, The effective focal length of the fourth lens (4) is f4, 1mm. <f4<11mm。 10. The projection system according to claim 1, characterized in that, The prism (5) has a thickness of L and is 3mm. <L<5mm。 11. The projection system according to any one of claims 1-10, characterized in that, The first lens (1), the second lens (2), the third lens (3), the fourth lens (4) and the prism (5) are made of glass.

12. The projection system according to claim 1, characterized in that, The projection system also includes an aperture stop (01), which is located on the light-emitting side of the first lens (1); The distance between the aperture (01) and the first lens (1) is less than 0.1 mm.

13. The projection system according to claim 12, characterized in that, The aperture (01) has a diameter of 3mm to 5mm and is used to match the entrance pupil diameter of the peripheral optical waveguide device.

14. An optical display device, characterized in that, include: The projection system as described in any one of claims 1-13; and An optical waveguide device, wherein the diameter of the aperture of the projection system is matched with the entrance pupil diameter of the optical waveguide device.

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