Projection system and optical display apparatus

Abstract

The embodiment of the invention provides a projection system and optical display equipment. Wherein the projection system comprises a lens group, a prism and a display chip which are arranged in sequence; wherein the lens group is composed of a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged, and the refractive index of the first lens, the refractive index of the second lens, the refractive index of the third lens and the refractive index of the fourth lens are larger than 1.6; the refractive index of the prism 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.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of optical imaging technology, and more specifically, relate to a light projection system and an optical display device. Background Art

[0002] With the rise of the concept of the metaverse, AR optical display devices have gradually entered people's lives. As one of the key optical components of AR optical display devices, the size, weight and optical performance of the projection machine are crucial to the user experience. In recent years, the rapid development of uLED (i.e. MicroLED) technology has provided new solutions for projection machines, which have the advantages of small size, low weight, high brightness and simple structure, and have gradually become the mainstream choice in AR optical display devices.

[0003] However, there are still some challenges in the existing projection optical machine, especially in the field of small FOV (diagonal FOV less than 25°). For example, how to achieve good optical performance, small temperature drift and easy production while ensuring small size and low weight is a problem that needs to be solved urgently. 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, an embodiment of the present application provides a projection system. The projection system includes a lens group, a prism, and a display chip arranged in sequence;

[0006] The lens group is composed of a first lens, a second lens, a third lens and a fourth lens which are arranged in sequence, and the refractive indexes of the first lens, the second lens, the third lens and the fourth lens are greater than 1.6;

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

[0008] 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.

[0009] Optionally, the projection system satisfies: [(v1+v2) / 2-(v3+v4) / 2]>20; wherein 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 Abbe number of the prism is 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 central thickness of the first lens is T1, the optical effective 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 central thickness of the second lens is T2, the optical effective 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 central thickness of the third lens is T3, the optical effective 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 f4,1 mm <f4<11mm;

[0023] The central thickness of the fourth lens is T4, the optical effective aperture of the fourth lens is L4, and 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 arranged between the first lens and the second lens and between the third lens and the fourth lens, and the thermal expansion coefficient of the metal spacers is 22 to 24×10 -6 ℃ -1.

[0027] Optionally, the projection system further comprises an aperture, and the aperture is located at a light exit side of the first lens;

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

[0029] Optionally, the diameter of the aperture is 3 mm to 5 mm, so as to match the entrance pupil diameter of an external optical waveguide device.

[0030] In a second aspect, the present application embodiment HIA provides an optical display device. The optical display device includes:

[0031] The projection system according to the first aspect; and

[0032] The optical waveguide device has an aperture diameter that matches the entrance pupil diameter of the optical waveguide device.

[0033] The beneficial effects of this application are:

[0034] The projection system provided in the embodiment of the present application is optimized for the field of small FOV (diagonal FOV less than 25°), and has the characteristics of small size, low weight, good optical performance and easy production. By accurately designing the parameters of each lens and adopting a specific lens combination, the projection system ensures clear imaging quality, low aberration and distortion while maintaining a small size and light weight.

[0035] Other features and advantages of the present specification will become apparent from the following detailed description of exemplary embodiments of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0037] Figure 1 One of the structural schematic diagrams of the projection system provided in the embodiment of the present application;

[0038] Figure 2 The second structural schematic diagram of the projection system provided in the embodiment of the present application;

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

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

[0041] Figure 5 for Figure 2 Modulation transfer function plots of the provided projection systems;

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

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

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

[0045] Fig. 9 The third structural diagram of the projection system provided in the embodiment of the present application;

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

[0047] Fig.11 for Fig. 9 Vertical axis chromatic aberration diagram of the provided projection system;

[0048] Fig.12 for Fig. 9 Modulation transfer function plots of the provided projection systems;

[0049] Fig.13 for Fig. 9 The off-axis curve of the provided projection system at a temperature of 25°;

[0050] Fig.14 for Fig. 9 The off-axis curve of the projection system provided at a temperature of -10°;

[0051] Fig.15 for Fig. 9 The off-axis curves of the projection system are provided at a temperature of 70°.

[0052] Description of reference numerals:

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

[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 of components and steps, numerical expressions and numerical values ​​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 in nature and is in no way intended to limit the present application, its application, or uses.

[0056] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0057] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0058] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0059] The projection system and optical display device provided in the embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0060] According to an embodiment of the present application, a projection system is provided. Figure 1 and Figure 2 , the projection system includes a lens group, a prism 5 and a display chip 6 arranged in sequence; wherein the lens group is composed of a first lens 1, a second lens 2, a third lens 3 and a fourth lens 4 arranged in sequence, and the refractive indexes of the first lens 1, the second lens 2, the third lens 3 and the fourth lens 4 are 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 the embodiment of the present application can be applied in the field of optical display with small FOV (for example, diagonal FOV less than 25°). Specifically, the projection system provided in the embodiment of the present application can have the characteristics of small size, low weight, good optical performance, small temperature drift and easy production in the field of small FOV (for example, diagonal FOV less than 25°), so that it has better performance in AR optical display applications.

[0062] The projection system provided in the embodiment of the present application, see Figure 1 and Figure 2 The projection system is mainly composed of a plurality of 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 light of different colors into one path) and a display chip 6. The specific refractive indexes 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 the embodiment of the present application includes a lens group, and the lens group can be composed of only four lenses. In other words, the projection system provided in the present application can achieve small volume and high-quality imaging through 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 the present application is composed of four lenses, specifically, the first lens 1 to the fourth lens 4 are 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. This refractive index design shows that these lenses use high refractive index materials. High refractive index materials help to reduce the physical size of the lens while maintaining its optical performance. This is crucial for designing a miniaturized and compact projection system.

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

[0067] The refractive index of the prism 5 of the present 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, which helps to reduce dispersion 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 Figure 1 , which is used to synthesize light of different colors, and the synthesized light then passes through the fourth lens 4, the third lens 3, the second lens 2 in sequence, and finally exits through the first lens 1. This process ensures the precise synthesis and transmission of light of different colors.

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

[0070] Figure 2 for Figure 1 , which intuitively shows how the light emitted by the display chip 6 directly enters the prism 5 and is emitted after being processed by the prism 5. Figure 2 Although some details are 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 the present application satisfies the condition: 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. 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 to measure the balance between compactness and optical performance of the projection system. A smaller TTL / f value means a more compact system.

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

[0074] The projection system provided in the embodiment of the present application can still maintain excellent optical performance, including clear imaging quality, low aberration and distortion, etc., through precise optical parameter design and material selection, despite the reduction in the size of the entire system.

[0075] In summary, this application realizes a small FOV projection system that is miniaturized, compact, and has excellent optical performance through specific lens and prism refractive index requirements and TTL / f ratio requirements. These technical features together provide strong technical support for the development of the wearable device field.

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

[0077] In some examples of the present application, 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.

[0078] In this example of the present 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 respectively represent the Abbe numbers of the first lens 1, the second lens 2, the third lens 3 and the fourth lens 4. It should be noted that the Abbe number is an important parameter to describe the dispersion ability of the lens material, which is closely related to the imaging quality of the lens.

[0079] In this example of the present application, the dispersion correction of the projection system is optimized by setting the condition [(v1+v2) / 2-(v3+v4) / 2]>20. 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] In order to meet the above conditions, the selection of lens material becomes crucial.

[0081] Materials with high Abbe numbers have lower dispersion and can reduce the color deviation caused by light passing through the 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 the present application, the combination of different lenses has a crucial influence 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] Vertical chromatic aberration refers to the phenomenon that after light of different wavelengths passes through a lens system, the focus point deviates not only in the axial direction (i.e., the direction of the optical axis), but also in the vertical direction (i.e., the direction perpendicular to the optical axis).

[0084] By carefully designing the Abbe number of the lens and making it meet the conditions in this example of the present application, the vertical axis chromatic aberration of the projection system can be effectively corrected. Specifically, the lens with a high Abbe number, namely the first lens 1 and the second lens 2, can reduce the focus deviation of short-wavelength light in the vertical axis direction, while the lens with a low Abbe number, namely the third lens 3 and the fourth lens 4, may have a better correction effect on long-wavelength light. The combination of the two can balance and reduce the vertical axis chromatic aberration to a certain extent. A projection system that meets this condition can significantly reduce the vertical axis chromatic aberration, thereby improving the clarity and color accuracy of the image. This is especially important for application scenarios that require high imaging quality (such as AR glasses).

[0085] In addition, by properly matching lens materials with different Abbe numbers, it is possible to achieve excellent optical performance while keeping the projection system small and compact.

[0086] It can be seen that the condition [(v1+v2) / 2-(v3+v4) / 2]>20 is an effective means to reduce vertical axis chromatic aberration by carefully selecting the Abbe number of the lens. It helps to improve the imaging quality and color accuracy of the projection system and provides a better optical solution for application scenarios such as AR glasses.

[0087] According to the example provided by 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 restrictions 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 of the present application achieves optimization of the color correction of the projection system by setting a specific Abbe number condition. This technical feature not only improves the color reproduction and image clarity, but also provides strong support for the overall performance optimization of the system.

[0091] In some examples of the present 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 present application, the four lenses in the lens group of the projection system and a prism combination are given 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 present 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, which means that they have a strong ability to correct dispersion. Dispersion is a phenomenon when a lens forms an image, which causes light of different wavelengths to focus at different positions, thus affecting the clarity of the image. Lenses with high Abbe numbers can reduce this dispersion effect, making the color of the image more accurate and clear.

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

[0096] Low Abbe number lenses (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 reasonable optical design, the dispersion introduced by the low Abbe number lens can be compensated to a certain 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 good as high Abbe number lenses in reducing dispersion, in a specific combination, they can be used in conjunction with high Abbe number lenses to balance the dispersion correction of the entire system. This combination may help reduce the dispersion of long-wave light (such as red light) and further reduce vertical axis chromatic aberration.

[0099] The Abbe number v5 of the prism 5 is greater than 50, indicating that it also has excellent dispersion correction capabilities. In a projection system, a prism is usually used to synthesize light of different colors. By using a prism material with a high Abbe number, it can be ensured that the color of the synthesized light is more accurate and consistent.

[0100] The prism 5 is usually used to combine or redirect light in a projection system. Using a prism with a high Abbe number can reduce the dispersion of light when it propagates inside the prism 5, thereby maintaining the high quality and color accuracy of the light. This is also important for reducing vertical axis chromatic aberration.

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

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

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

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

[0105] In some examples of this application, see 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 the present application, the lens group in the projection system adopts a specific type of lens combination, that is, 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 the meniscus lens is convex and the other surface is concave. This shape helps to correct aberrations. As positive lenses, they have a converging effect on light, which helps to accurately project the light from the display chip 6 onto the target plane.

[0108] The third lens 3 is a meniscus negative lens. The third lens 3 also adopts a meniscus design, but as a negative lens, it has a divergent effect on light. In a projection system, a negative lens is used to correct system aberrations, especially field curvature and distortion, thereby improving the flatness and accuracy of the image.

[0109] The fourth lens is an aspherical positive lens, which can converge light and further reduce aberration and improve imaging quality through its aspherical design.

[0110] By adopting 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 imaging.

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

[0112] In the projection system provided by the embodiment of the present application, the refractive powers of the first lens 1 to the fourth lens 4 are positive, positive, negative, positive in sequence. The surface shapes of the first lens 1 to the fourth lens 4 are convex-concave lens, convex-concave lens, convex-concave lens, and aspherical lens in sequence.

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

[0114] In this example of the present application, the effective focal length f of the projection system is set in the range of 6 mm to 8 mm. This specific focal length selection is based on comprehensive considerations of the projection system performance, volume, weight, and imaging quality.

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

[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 in 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, and 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 in 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 the thickness to the 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, and 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 restricted 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 intended 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 of the third lens 3 to the optical effective aperture L3 is restricted 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 of the fourth lens to the optical effective aperture L4 is restricted 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 the prism 5, the entire projection system can maintain a small size and weight, making it very suitable for integration into small devices such as AR glasses. Appropriate control of the lens thickness and aperture ratio can prevent the lens from being easily damaged due to being too thin, or from adding unnecessary weight and volume due to being too thick. At the same time, the stability and durability of the prism are also guaranteed.

[0132] In some examples of the present 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] In the projection system provided in the embodiment of the present application, four lenses and one prism 5 are all made of glass material.

[0134] Glass materials have excellent optical transparency, which can reduce the scattering and absorption of light inside the lens, thereby improving the clarity and contrast of imaging. In addition, the refractive index and dispersion characteristics of glass lenses are relatively stable, which helps to reduce chromatic aberration and further improve imaging quality.

[0135] Glass has a relatively low coefficient of thermal expansion and good thermal conductivity, so the lens is less likely to deform when the temperature changes and can maintain stable optical performance. This is especially important for applications such as AR glasses that need to work for long periods of time or in different temperature environments, and can reduce the degradation of image quality caused by temperature changes.

[0136] Glass has high hardness and toughness, and can resist external impact and wear, thus extending the service life of the lens. For applications such as AR glasses that need to be frequently exposed to the external environment, this can reduce lens damage caused by accidental collisions or wear.

[0137] Since all lenses and prisms in the projection system are made of glass, their thermal expansion coefficients and physical properties are relatively consistent, which helps reduce system instability and performance degradation caused by material differences. This is crucial to 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 of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4 and the prism 5 can significantly improve the optical performance, thermal stability, mechanical strength and overall system stability of the projection system. These advantages make the projection system more suitable for small-sized, high-performance application scenarios such as AR glasses.

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

[0140] Among them, 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 arranged between the first lens 1 and the second lens 2 and between the third lens 3 and the fourth lens 4.

[0141] The close design of the second lens 2 and the third lens 3 helps to reduce the gap between lens components, thereby reducing the volume of the entire 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 introduced between the third lens 3 and the fourth lens 4. By precisely controlling thermal expansion, the lens displacement caused by temperature change can be reduced, thereby reducing the temperature drift of the system and ensuring the stability of imaging.

[0143] Aluminum alloy spacers not only have stable thermal expansion performance, but also have high strength and toughness. They can effectively support and protect the lens, prevent lens displacement or damage caused by external shock or vibration, 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 thermal expansion coefficient of 22 to 24×10 -6 ℃ -1 The metal spacer is provided, and the second lens 2 and the third lens 3 are designed to be close to each other. The example of the present application has achieved remarkable technical effects in reducing volume and weight, controlling thermal expansion, improving system stability, optimizing imaging quality, and simplifying assembly and debugging.

[0146] In some examples of this application, see Figure 1 and Figure 2 The projection system further includes an aperture 01, which is located at the light exit side of the first lens 1; and the interval between the aperture 01 and the first lens 1 is less than 0.1 mm.

[0147] See also Figure 1 and Figure 2 , the projection system of the present application further includes an aperture 01, and the aperture 01 is located on the light exit side of the first lens 1. In particular, the distance between the aperture 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 01 and the first lens 1 helps to reduce the overall volume of the projection system. In addition, the close spacing reduces the scattering and loss of light between the aperture and the lens, thereby improving the light utilization efficiency. This helps to enhance the brightness and contrast of the projection system and improve the imaging quality.

[0148] In some examples of the present application, the diameter of the aperture 01 is 3 mm to 5 mm, so as to match the entrance pupil diameter of an external optical waveguide device.

[0149] In this example of the present application, the diameter of the aperture 01 is 3 mm to 5 mm, and this size range is specially designed to match the entrance pupil diameter of an external optical waveguide device.

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

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

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

[0153] The projection system of the present application has significant technical effects, which are mainly reflected in the following aspects:

[0154] (1) Small size and light weight:

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

[0156] (2) Good optical properties:

[0157] The projection system of the present application ensures clear imaging quality, low aberration and distortion while maintaining a small size, thereby improving the overall optical performance by precisely designing the parameters and combination of each lens.

[0158] (3) Small temperature drift characteristics:

[0159] By using materials with stable thermal expansion coefficients (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 reproduction:

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

[0162] The projection system of the present application is suitable for the optical display field with small FOV (diagonal FOV less than 25°), such as AR glasses, etc. At different temperatures (such as -10°C, 25°C, 70°C), 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 the present application shows significant technical advantages in terms of volume, weight, optical performance, temperature drift control, color reproduction, production difficulty and application prospects.

[0164] According to another embodiment of the present application, an optical display device is provided. The optical display device includes the projection system and the optical waveguide device as described above. 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 the present application, an optical display device is provided, which integrates the aforementioned projection system and optical waveguide device. In particular, 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 and 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 to maintain the collimation and focus of the light, thereby avoiding image blur and distortion caused by light scattering or defocusing, which 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, the stability of the entire optical display system can be enhanced. This helps ensure that the system can provide stable imaging effects in a variety of usage environments.

[0169] Optical display devices that integrate efficient 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 is described in detail below through Example 1 and Example 2.

[0171] Example 1

[0172] See also Figure 2 , the projection system is composed of a lens group, a prism 5 and a display chip 6 arranged in sequence; wherein the lens group is composed 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 made of glass;

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

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

[0177] The optical parameters of the lenses and prisms in the projection system provided in Example 1 are shown in Table 1.

[0178] Table 1

[0179]

[0180]

[0181] The even-order aspheric surface satisfies the following relationship:

[0182]

[0183] Wherein, Y is the center height of the fourth lens 4, Z is the displacement value of the aspheric structure at a height of Y along the optical axis direction, with the surface vertex as a reference from the optical axis, C is the vertex curvature radius of the aspheric surface, K is the cone coefficient; αi represents the i-th aspheric coefficient. For the optical parameters of the fourth lens 4, please refer to Table 2.

[0184] Table 2

[0185] Surface serial number Cone 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] The optical performance of the projection system provided in Example 1 of the present application can be seen in Figures 3 to 8 :

[0187] See also Figure 3 : Figure 3 The figure shows the field curvature and optical distortion of the projection system. Figure 3 It can be seen that the projection system of Example 1 of the present 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 also Figure 4 : Figure 4 The vertical chromatic aberration diagram of the projection system is shown. Vertical chromatic aberration refers to the fact that the image points formed by light of different wavelengths on the imaging plane are not at the same height, resulting in color edges in the image. Figure 4 The distribution of light of different wavelengths on the imaging plane is shown in Figure 1. It can be seen that the projection system has good control over vertical chromatic aberration, and the image points formed by light of different wavelengths are relatively concentrated, which helps to reduce the color deviation of the image.

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

[0190] See also Figures 6 to 8 : Off-axis curves at 25°, -10°, and 70°. The off-axis curve describes the distribution of off-axis light on the imaging plane of the projection system at different temperatures. The change of the off-axis curve can reflect the imaging stability of the lens at different temperatures.

[0191] From Figure 6 to Figure 8It can be seen that at different temperatures, the off-axis curve of Example 1 maintains good consistency, indicating that it has good temperature drift control capability, which helps to ensure that the projection system can provide stable imaging quality at different ambient temperatures.

[0192] In summary, the projection system of this embodiment 1 has excellent optical performance, with low field curvature and distortion, good vertical axis chromatic aberration control, high contrast transmission capability and excellent temperature drift control capability. These advantages make the projection system very suitable for application scenarios with high optical performance requirements, such as AR glasses.

[0193] Example 2

[0194] See also Fig. 9 , the projection system is composed of a lens group, a prism 5 and a display chip 6 arranged in sequence; wherein the lens group is composed 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 made of glass;

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

[0198] The projection system has a total optical 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 the lenses and prisms in the projection system provided in Example 2 are shown in Table 3.

[0200] Table 3

[0201]

[0202] The even-order aspheric surface satisfies the following relationship:

[0203]

[0204] Wherein, Y is the center height of the fourth lens 4, Z is the displacement value of the aspheric structure at a height of Y along the optical axis direction, with the surface vertex as a reference from the optical axis, C is the vertex curvature radius of the aspheric surface, K is the cone coefficient; αi represents the i-th aspheric coefficient. Please refer to Table 4 for the optical parameters of the fourth lens 4.

[0205] Table 4

[0206]

[0207]

[0208] The optical performance of the projection system provided in Example 2 of the present application can be found in Figures 10 to 15 :

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

[0210] See also Fig.11 : Fig.11 The vertical axis chromatic aberration diagram of the projection system is shown. Vertical axis chromatic aberration means that the image points formed by light of different wavelengths on the imaging plane are not at the same height, which will cause color fringes to appear at the edge of the image. Fig.11 The distribution of light of different wavelengths on the imaging plane is shown. It can be seen that the vertical axis chromatic aberration has been effectively controlled, and the image points formed by light of different wavelengths are relatively concentrated, which helps to reduce the color deviation of the image and improve the color reproduction.

[0211] See also Fig.12 : Fig.12 shows the modulation transfer function (MTF) of the projection system. Fig.12 It can be seen that the MTF curve maintains 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 also Figures 13 to 15 : Off-axis curves at temperatures of 25°, -10°, and 70° These graphs show the off-axis light distribution of the lens at different temperatures, reflecting the temperature drift performance of the projection system.

[0213] Fig.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] Fig.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] Fig.15 (70℃): Under high temperature conditions, the off-axis curve remains stable, indicating that the projection system can maintain good temperature drift control capabilities in high temperature environments.

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

[0217] In summary, the projection system of Example 2 also performs well in terms of optical performance. Through the field curvature and distortion diagram, vertical axis chromatic aberration diagram, MTF diagram, and off-axis curve diagrams at different temperatures, the imaging quality, color reproduction, contrast transmission capability, and temperature drift control capability of the projection system can be fully evaluated. These chart data provide strong support for performance verification and optimization of the projection system.

[0218] The above embodiments focus on 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. Considering the simplicity of the text, they will not be repeated here.

[0219] Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are only for illustration, not for limiting the scope of the present application. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A projection system, characterized in that: It comprises a lens group, a prism (5) and a display chip (6) which are arranged in sequence; The lens group is composed of a first lens (1), a second lens (2), a third lens (3) and a fourth lens (4) which are 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 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.

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, and 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; 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.

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; 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.

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; 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.

9. The projection system according to claim 8, characterized in that: The effective focal length of the fourth lens (4) is f4,1 mm <f4<11mm; 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.

10. The projection system according to claim 1, characterized in that: The thickness of the prism (5) is L, and 3mm <L<5mm。 11. The projection system according to any one of claims 1 to 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 11, characterized in that: The second lens (2) and the third lens (3) are close to each other, and metal spacers are respectively arranged between the first lens (1) and the second lens (2) and between the third lens (3) and the fourth lens (4), and the thermal expansion coefficient of the metal spacers is 22 to 24×10 -6 ℃ -1 .

13. The projection system according to claim 12, characterized in that: The projection system further comprises an aperture (01), wherein the aperture (01) is located on the light exit side of the first lens (1); The distance between the aperture (01) and the first lens (1) is less than 0.1 mm.

14. The projection system according to claim 13, characterized in that: The diameter of the aperture (01) is 3 mm to 5 mm, and is used to match the entrance pupil diameter of an external optical waveguide device.

15. An optical display device, characterized in that: include: The projection system according to any one of claims 1 to 14; and The optical waveguide device has an aperture diameter that matches the entrance pupil diameter of the optical waveguide device.

Images