projection lens

Abstract

This invention provides a projection lens. The projection lens includes a lens group comprising at least eight lenses, which, from a first side to a second side, are sequentially: a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with optical power, a seventh lens with optical power, and an eighth lens with optical power. At least one group of lenses from the fourth to the eighth lens is cemented together to form a cemented doublet lens or a cemented triplet lens. The ratio between the combined focal length of the cemented doublet lens and the focal length of the second lens group is greater than or equal to 1 and less than or equal to 8; or, the ratio between the focal length of the cemented triplet lens and the focal length of the second lens group is greater than or equal to 0 and less than or equal to 14. This invention solves the problem in existing projection lenses where it is difficult to simultaneously achieve both high-quality projection and miniaturization.

Description

Technical Field

[0001] This invention relates to the field of optical projection equipment technology, and more specifically, to a projection lens. Background Technology

[0002] With the development of the projection display industry, people's requirements for projection lenses used in projection devices are no longer limited to large projection screens and high resolution performance, but also include a compact and lightweight appearance. This requires projection lenses to use fewer lenses while ensuring image quality and a smaller overall lens length. Most current projection lens solutions use more lenses or sacrifice the field of view to solve the problem of projection distortion.

[0003] In other words, existing projection lenses suffer from the problem of simultaneously failing to achieve both high-quality projection and miniaturization. Summary of the Invention

[0004] The main objective of this invention is to provide a projection lens that solves the problem that existing projection lenses cannot simultaneously achieve both high-quality projection and miniaturization.

[0005] To achieve the above objectives, the present invention provides a projection lens, including a lens group comprising at least eight lenses. The eight lenses, from a first side to a second side, are sequentially: a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with optical power, a seventh lens with optical power, and an eighth lens with optical power. At least one of the first to third lenses is an aspherical lens, and the refraction of at least one of the first to third lenses... The refractive index is greater than or equal to 1.8 and less than 2.0; or, at least two of the fourth to eighth lenses are glass lenses, and at least one lens has a refractive index greater than or equal to 1.6 and less than 2.0; or, at least one group of the fourth to eighth lenses is cemented together to form a cemented doublet or a cemented triplets lens; the ratio between the combined focal length of the cemented doublet and the focal length of the second lens group is greater than or equal to 1 and less than or equal to 8; or, the ratio between the focal length of the cemented triplets and the focal length of the second lens group is greater than or equal to 0 and less than or equal to 14, and the second lens group includes at least the seventh and eighth lenses.

[0006] Furthermore, the lens group consists of eight lenses, with the sixth lens having positive optical power, the seventh lens having positive optical power, and the eighth lens having positive optical power; or, the lens group consists of nine lenses, including a ninth lens located on the second side of the eighth lens, with the sixth lens having positive optical power, the seventh lens having negative optical power, the eighth lens having positive optical power, and the ninth lens having positive optical power; or, the lens group consists of eleven lenses, including a ninth, tenth, and eleventh lens sequentially arranged on the second side of the eighth lens, with the sixth lens having negative optical power, the seventh lens having positive optical power, the eighth lens having negative optical power, the ninth lens having positive optical power, the tenth lens having positive optical power, and the eleventh lens having positive optical power.

[0007] Furthermore, the projection lens also includes an aperture stop. When the lens group consists of eight or nine lenses, the aperture stop is located between the third and fourth lenses to divide the lens group into a first lens group and a second lens group. The first lens group includes the first to the third lenses, and the second lens group includes the fourth to the eighth lenses or the fourth to the ninth lenses. When the lens group consists of eleven lenses, the aperture stop is located between the sixth and the seventh lenses to divide the lens group into a first lens group and a second lens group. The first lens group includes the first to the sixth lenses, and the second lens group includes the seventh to the eleventh lenses.

[0008] Furthermore, the first lens is an aspherical lens; and / or the refractive index dn of the eighth lens satisfies the following relationship with the temperature dt of the eighth lens: -8 <dn / dt<-2。

[0009] Furthermore, the second lens group includes at least one cemented doublet or cemented triplicate lens, wherein at least one of the cemented doublet or cemented triplicate lenses has an Abbe number greater than or equal to 55 and less than or equal to 95.

[0010] Furthermore, the fourth and fifth lenses are cemented together to form a cemented doublet, and the sixth and seventh lenses are cemented together to form another cemented doublet. One lens in the cemented doublet has positive optical power, and the other has negative optical power. The combined focal length F of the fourth and fifth lenses is... L4～L5 The focal length F2 of the second lens group satisfies: 4 ≤ F L4～L5 / F2≤7; and / or, the combined focal length F of the sixth and seventh lenses. L6～L7 The focal length F2 of the second lens group satisfies: 2 ≤ F L6～L7 / F2≤6; and / or, the combined focal length F of the fourth, fifth, sixth, and seventh lenses. L4～L7 The focal length F2 of the second lens group satisfies: 2 ≤ F L4～L7 / F2≤5.

[0011] Furthermore, the seventh, eighth, and ninth lenses are cemented together to form a cemented triplet lens, and the combined focal length F of the seventh, eighth, and ninth lenses is... L7～L9 The focal length F2 of the second lens group satisfies: 0 ≤ F L7～L9 / F2≤6; or, the fourth, fifth, and sixth lenses are cemented together to form a cemented triplet lens, and the combined focal length of the fourth, fifth, and sixth lenses is F. L4～L6 The focal length F2 of the second lens group satisfies: 2 ≤ F L4～L6 / F2≤13.

[0012] Furthermore, the first lens group includes at least a first lens, a second lens, and a third lens, and the projection lens satisfies at least one of the following conditions: the focal length F1 of the first lens group satisfies: -140mm≤F1≤-25mm; the focal length F2 of the second lens group satisfies: -30mm≤F2≤-5mm; the focal length F1 of the first lens group and the total focal length EFL of the projection lens satisfy: -13.5≤F1 / EFL≤-3.5; the focal length F2 of the second lens group and the total focal length EFL of the projection lens satisfy -5≤F2 / EFL≤0mm.

[0013] Furthermore, the first lens has a concave first side surface and a concave or convex second side surface; the second lens has a concave first side surface and a concave second side surface; the third lens has a convex first side surface and a convex second side surface; the fourth lens has a planar, concave, or convex first side surface and a concave or convex second side surface; the fifth lens has both convex first and second side surfaces or both concave second side surfaces; the sixth lens has a convex or concave first side surface and a convex second side surface; the seventh lens has a concave or convex first side surface and a convex second side surface; the eighth lens has a concave first side surface and a convex or concave second side surface; the ninth lens has a convex first side surface and a convex second side surface; the tenth lens has a convex first side surface and a convex second side surface; and the eleventh lens has a convex first side surface and a convex second side surface.

[0014] Furthermore, the diameter of each lens in the lens group is greater than 0 mm and less than 35 mm; the optical total length (TTL) of the projection lens and the total focal length (EFL) of the projection lens satisfy the following relationship: 8 ≤ TTL / EFL ≤ 14; the back focal length (BFL) of the projection lens and the optical total length (TTL) of the projection lens satisfy the following relationship: 0.2 ≤ BFL / TTL ≤ 0.4; the back focal length (BFL) of the projection lens and the total focal length (EFL) of the projection lens satisfy the following relationship: 3 ≤ BFL / EFL ≤ 4; the total focal length (EFL) of the projection lens satisfies the following relationship: 5 mm ≤ EFL ≤ 15 mm; the aperture number (Fno) of the projection lens satisfies the following relationship: 1 ≤ Fno ≤ 3; the optical total length (TTL) of the projection lens satisfies the following relationship: 110 mm ≤ TTL ≤ 135 mm; the system field of view of the projection lens is greater than or equal to 60° and less than or equal to 30°; the ratio of the projection distance to the screen width (TR) of the projection lens satisfies the following relationship: 0.8 ≤ TR ≤ 1.2.

[0015] Applying the technical solution of this invention, the projection lens includes a lens group, which includes at least eight lenses. The eight lenses, from the first side to the second side, are sequentially: a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with optical power, a seventh lens with optical power, and an eighth lens with optical power. Specifically, at least one of the first to third lenses is an aspherical lens, and the refractive index of at least one of the first to third lenses is greater than [missing value]. The refractive index is equal to 1.8 and less than 2.0; or, at least two of the fourth to eighth lenses are glass lenses, and the refractive index of at least one lens is greater than or equal to 1.6 and less than 2.0; or, at least one group of the fourth to eighth lenses is cemented together to form a cemented doublet or a cemented triplets lens; the ratio between the combined focal length of the cemented doublet and the focal length of the second lens group is greater than or equal to 1 and less than or equal to 8; or, the ratio between the focal length of the cemented triplets and the focal length of the second lens group is greater than or equal to 0 and less than or equal to 14, and the second lens group includes at least the seventh and eighth lenses.

[0016] By rationally planning the number of lenses and their optical power within the lens group, it is beneficial to plan the light path, ensuring a smooth transition of light and guaranteeing projection stability and reliability. By setting at least one aspherical lens among the first to third lenses, aspherical lenses can significantly correct distortion, astigmatism, and sine aberration. Furthermore, this effectively reduces the number of lenses and shortens the overall length of the projection lens, thereby reducing the overall weight and cost. By designing at least one lens among the first to third lenses to have a refractive index greater than or equal to 1.8 and less than 2.0, and by using at least two glass lenses among the fourth to eighth lenses, with at least one lens among the fourth to eighth lenses having a refractive index greater than or equal to 1.6 and less than 2.0, and by using high-refractive-index materials for at least one lens among the first to third lenses and at least one lens among the fourth to eighth lenses, thermal compensation can be performed on the entire optical system. This compensates for thermal defocusing of the entire optical system, allowing it to maintain high resolution even at high temperatures. By cementing at least one set of lenses from the fourth to the eighth lens group to form a cemented doublet or a cemented triplet lens; the ratio between the combined focal length of the cemented doublet lens and the focal length of the second lens group is greater than or equal to 1 and less than or equal to 8; or, the ratio between the focal length of the cemented triplet lens and the focal length of the second lens group is greater than or equal to 0 and less than or equal to 14. By reasonably setting the cemented lenses, chromatic aberration can be effectively corrected while meeting the requirements for size compression. The projection lens of this application reduces the number of lenses, lowers the processing difficulty, is suitable for mass production, and can ensure clear imaging over a large projection area while having sufficiently small distortion. The image source target area can support a 0.37-inch chip with unidirectional longitudinal axis shift of -100% to +100%. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 A schematic diagram of the projection lens according to Embodiment 1 of the present invention is shown;

[0019] Figure 2 It shows Figure 1 Field curvature diagram of the projection lens in the image;

[0020] Figure 3 It shows Figure 1 The distortion diagram of the projection lens in the image;

[0021] Figure 4 A schematic diagram of the projection lens of Embodiment 2 of the present invention is shown;

[0022] Figure 5A schematic diagram of the projection lens of Embodiment 3 of the present invention is shown.

[0023] The above figures include the following reference numerals:

[0024] 10. Projection screen; STO, aperture stop; L1, first lens; L2, second lens; L3, third lens; L4, fourth lens; L5, fifth lens; L6, sixth lens; L7, seventh lens; L8, eighth lens; L9, ninth lens; L10, tenth lens; L11, eleventh lens; 20. Galvanometer; 30. Protective glass; 40. Polarizer; 50. Half-wave plate; 60. LCOS chip. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0027] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0028] In this paper, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the first side is called the first side surface of the lens, and the surface of each lens closest to the second side is called the second side surface of the lens. The determination of the surface shape in the paraxial region can be based on the judgment method commonly used by those knowledgeable in the field, using the R value (R refers to the radius of curvature of the paraxial region, usually the R value in the lens database of optical software) to determine concavity or convexity. For the first side surface, when the R value is positive, it is determined to be convex; when the R value is negative, it is determined to be concave; when the R value is ±∞, it is determined to be flat. For the second side surface, when the R value is positive, it is determined to be concave; when the R value is negative, it is determined to be convex; when the R value is ±∞, it is determined to be flat.

[0029] In this application, the left side of the projection lens is the first side, and the right side is the second side. In a specific embodiment of this application, the first side of the projection lens is the projection screen 10 side, and the second side is the LCOS chip side. During projection, light from the LCOS chip can form an image on the projection screen 10 side.

[0030] To address the problem that existing projection lenses cannot simultaneously achieve both high-quality projection and miniaturization, this invention provides a projection lens.

[0031] like Figures 1 to 5 As shown, the present invention provides a projection lens, including a lens group comprising at least eight lenses, the eight lenses being sequentially arranged from the first side to the second side as follows: a first lens L1 with negative optical power, a second lens L2 with negative optical power, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a fifth lens L5 with positive optical power, a sixth lens L6 with optical power, a seventh lens L7 with optical power, and an eighth lens L8 with optical power; wherein, at least one of the first lens L1 to the third lens L3 is an aspherical lens, and at least one of the first lens L1 to the third lens L3 has a refractive index of... The refractive index is greater than or equal to 1.8 and less than 2.0; or, at least two of the fourth lens L4 to the eighth lens L8 are glass lenses, and at least one lens has a refractive index greater than or equal to 1.6 and less than 2.0; or, at least one group of the fourth lens L4 to the eighth lens L8 is cemented together to form a cemented doublet or a cemented tripet; the ratio between the combined focal length of the cemented doublet and the focal length of the second lens group is greater than or equal to 1 and less than or equal to 8; or, the ratio between the focal length of the cemented tripet and the focal length of the second lens group is greater than or equal to 0 and less than or equal to 14, and the second lens group includes at least the seventh lens L7 and the eighth lens L8.

[0032] By rationally planning the number of lenses and their optical power within the lens group, it is beneficial to plan the light path, ensuring a smooth transition of light and guaranteeing projection stability and reliability. By setting at least one aspherical lens among the first to third lenses, aspherical lenses can significantly correct distortion, astigmatism, and sine aberration. Furthermore, this effectively reduces the number of lenses and shortens the overall length of the projection lens, thereby reducing the overall weight and cost. By designing at least one lens among the first to third lenses to have a refractive index greater than or equal to 1.8 and less than 2.0, and by using at least two glass lenses among the fourth to eighth lenses, with at least one lens among the fourth to eighth lenses having a refractive index greater than or equal to 1.6 and less than 2.0, and by using high-refractive-index materials for at least one lens among the first to third lenses and at least one lens among the fourth to eighth lenses, thermal compensation can be performed on the entire optical system. This compensates for thermal defocusing of the entire optical system, allowing it to maintain high resolution even at high temperatures. By cementing at least one set of lenses from the fourth to the eighth lens group to form a cemented doublet or a cemented triplet lens; the ratio between the combined focal length of the cemented doublet lens and the focal length of the second lens group is greater than or equal to 1 and less than or equal to 8; or, the ratio between the focal length of the cemented triplet lens and the focal length of the second lens group is greater than or equal to 0 and less than or equal to 14. By reasonably setting the cemented lenses, chromatic aberration can be effectively corrected while meeting the requirements for size compression. The projection lens of this application reduces the number of lenses, lowers the processing difficulty, is suitable for mass production, and can ensure clear imaging over a large projection area while having sufficiently small distortion. The image source target area can support a 0.37-inch chip with unidirectional longitudinal axis shift of -100% to +100%.

[0033] In different embodiments of the application, the ratio between the combined focal length of the cemented doublet lens and the focal length of the second lens group is 2, 3.4, 4, 4.5, 6, and 7.

[0034] In different embodiments of the application, the ratio between the focal length of the cemented triplex lens and the focal length of the second lens group is 2, 4, 6, 7, 9, 12, and 13.

[0035] Furthermore, by combining aspherical lenses and cemented lenses, the projection lens of this application achieves a compact design while maintaining high optical performance, greatly improving the portability and installation flexibility of the projection device. The use of cemented lenses ensures that the projection lens maintains stable imaging performance despite temperature variations, making it suitable for use in various environmental conditions, such as outdoor projection and industrial projection applications in high- or low-temperature working environments.

[0036] In one embodiment of this application, the lens group consists of eight lenses, namely, the first lens L1 to the eighth lens L8. In this case, the sixth lens L6, the seventh lens L7, and the eighth lens L8 have positive optical power. The projection lens also includes an aperture stop STO, located between the third lens L3 and the fourth lens L4, to divide the lens group into a first lens group and a second lens group. The first lens group includes the first lens L1, the second lens L2, and the third lens L3, and the second lens group includes the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8.

[0037] In another embodiment of this application, the lens group consists of nine lenses, including a first lens L1 to an eighth lens L8, and a ninth lens L9 located on the second side of the eighth lens L8. In this case, the sixth lens L6 has positive optical power, the seventh lens L7 has negative optical power, the eighth lens L8 has positive optical power, and the ninth lens L9 has positive optical power. An aperture stop STO is located between the third lens L3 and the fourth lens L4 to divide the lens group into a first lens group and a second lens group. The first lens group includes the first lens L1, the second lens L2, and the third lens L3, and the second lens group includes the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the ninth lens L9.

[0038] In another optional embodiment of this application, the lens group consists of eleven lenses, including a first lens L1 to an eighth lens L8, and further including a ninth lens L9, a tenth lens L10, and an eleventh lens L11 sequentially disposed on the second side of the eighth lens L8. In this case, the sixth lens L6 has negative optical power, the seventh lens L7 has positive optical power, the eighth lens L8 has negative optical power, the ninth lens L9 has positive optical power, the tenth lens L10 has positive optical power, and the eleventh lens L11 has positive optical power. The aperture stop STO is located between the sixth lens L6 and the seventh lens L7, dividing the lens group into a first lens group and a second lens group. The first lens group includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6. The second lens group includes a seventh lens L7, an eighth lens L8, a ninth lens L9, a tenth lens L10, and an eleventh lens L11.

[0039] Through this variable lens combination, it is possible to meet the diverse requirements of different projection devices for focal length, field angle, and imaging quality, improving the adaptability and flexibility of the projection lens. In addition, by adjusting the optical powers of the seventh lens L7 and the eighth lens L8, the chromatic aberration and distortion of the optical lens can be optimized, making it suitable for professional projection applications with high requirements for color reproducibility and image fidelity, such as art exhibitions, high-end photography displays, etc. By placing the aperture STO at a specific position in the lens group, the amount of incident light and the light direction can be effectively controlled, reducing the impact of non-imaging light on the projection screen, so that a clear and high-contrast projection image can be obtained even in a complex light environment. This design is particularly suitable for application scenarios with variable light conditions such as stage lighting and outdoor advertising, ensuring excellent projection effects under any lighting conditions.

[0040] Specifically, the first lens L1 is an aspherical lens. By setting the first lens L1 as an aspherical lens, it is beneficial to correct distortion, simultaneously correct astigmatism and sine difference, and in addition, it can effectively reduce the number of lenses and shorten the total length of the projection lens.

[0041] Specifically, the refractive index dn of the eighth lens L8 and the temperature dt of the eighth lens L8 satisfy: -8 < dn / dt < -2. By programming dn / dt to be negative, the refractive index of the material decreases as the temperature increases, so that the eighth lens L8 can achieve thermal defocus compensation, compensating for the thermal defocus of the entire optical system, and enabling the entire optical system to still maintain a high resolution at high temperatures. In different embodiments of the present application, dn / dt = -7.9, -6.3, -5.7, -4.5, -3.8, -2.1.

[0042] Specifically, the second lens group includes at least one doublet lens or at least one triplet lens, and the Abbe number of at least one lens in the doublet lens or triplet lens is greater than or equal to 55 and less than or equal to 95. By reasonably setting the doublet lens or triplet lens, and programming the Abbe number of at least one lens in the doublet lens to be greater than or equal to 55 and less than or equal to 95, and the Abbe number of at least one lens in the triplet lens to be greater than or equal to 55 and less than or equal to 95, at least one lens in the cemented lens is a high-Abbe number lens. By using cemented lenses with high and low Abbe numbers, it is beneficial to correct chromatic aberration, can significantly reduce the dispersion effect, and improve color reproducibility.

[0043] In an embodiment of the present application, the fourth lens and the fifth lens are cemented to form a doublet lens, the sixth lens and the seventh lens are cemented to form a doublet lens, one lens in the doublet lens has a positive optical power, and the other lens has a negative optical power; the combined focal length F of the fourth lens L4 and the fifth lens L5 L4～L5 and the focal length value F2 of the second lens group satisfy: 4 ≤ F L4～L5 / F2≤7; The combined focal length F of the sixth lens L6 and the seventh lens L7 L6～L7 The focal length F2 of the second lens group satisfies: 2 ≤ F L6～L7 / F2≤6. In this case, the lens group can consist of nine lenses, but other numbers are also possible; this application does not impose any restrictions. By rationally planning the ratio range between the combined focal length of the cemented doublet lenses and the focal length F2 of the second lens group, it is beneficial to balance the focal length of the cemented doublet lenses. High-precision focal length control allows the projection lens of this application to adapt to different projection distances, ensuring image clarity and detail for both near-field projection and long-field demonstrations. Furthermore, this configuration enables the projection lens of this application to achieve a significant improvement in optical performance, while ensuring the compactness, cost-effectiveness, thermal stability, and support for high-resolution chips, ultimately providing users with a high-quality, cost-effective projection solution. In different embodiments of this application, F... L4～L5 / F2 = 4.00, 4.85, 5.21, 6.11, 7.00; F L6～L7 / F2 = 2.00, 4.26, 5.78, 6.00.

[0044] Specifically, the fourth and fifth lenses are cemented together to form a cemented doublet, and the sixth and seventh lenses are cemented together to form a cemented doublet. The combined focal length F of the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7 is... L4～L7 The focal length F2 of the second lens group satisfies: 2 ≤ F L4～L7 / F2≤5. This helps to balance the proportion of the focal length of the cemented lens to the focal length of the second lens group, improving projection quality and sharpness through reasonable focal length allocation, and reducing ghosting and aberrations. In different embodiments of this application, F L4～L7 / F2 = 2.74, 3.85, 4.22, 5.00.

[0045] In another embodiment of this application, the seventh lens L7, the eighth lens L8, and the ninth lens L9 are cemented together to form a cemented triplet lens, and the combined focal length F of the seventh lens L7, the eighth lens L8, and the ninth lens L9 is... L7～L9 The focal length F2 of the second lens group satisfies: 0 ≤ F L7～L9 / F2≤6; In this case, the lens group can consist of eleven lenses, but other numbers are also possible, and this application does not impose any restrictions. This is beneficial for balancing the ratio of the focal length of the cemented triplet lens to the focal length of the second lens group, improving projection quality and sharpness through reasonable focal length allocation, and reducing ghosting and aberrations. In different embodiments of this application, F L7～L9 / F2 = 2.33, 4.75, 5.38, 6.00.

[0046] In another embodiment of this application, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are cemented together to form a cemented triplet lens. The combined focal length FL4~L6 of the fourth lens L4, the fifth lens L5, and the sixth lens L6 satisfies the following relationship with the focal length F2 of the second lens group: 2≤F L4～L6 / F2≤13. In this case, the lens group can consist of eight lenses, but other numbers are also possible; this application does not impose any limitations. This helps to balance the ratio of the focal length of the cemented triplet lens to the focal length of the second lens group, improving projection quality and sharpness through reasonable focal length allocation, and reducing ghosting and aberrations. In different embodiments of this application, F... L4～L6 / F2 = 2.75, 3.56, 4.79, 8.23, 10.50, 12.79.

[0047] Specifically, the projection lens must meet at least one of the following conditions: The focal length F1 of the first lens group satisfies: -140mm ≤ F1 ≤ -25mm; the focal length F2 of the second lens group satisfies: -30mm ≤ F2 ≤ -5mm. By rationally planning the focal lengths of the first and second lens groups, it is beneficial to balance the aberrations generated by the front and rear lenses, effectively improving off-axis aberrations while maintaining the balance of the entire optical system. It can also correct off-axis chromatic aberration, reduce the dispersion of light of different wavelengths passing through the lens, and ensure the accuracy of image colors and the overall clarity of the image. The focal length F1 of the first lens group and the total focal length EFL of the projection lens must satisfy: -13.5 ≤ F1 / EFL ≤ -3.5; the focal length F2 of the second lens group and the total focal length EFL of the projection lens must satisfy: -5 ≤ F2 / EFL ≤ 0mm. This setting facilitates the allocation of focal length proportions among the lens groups, ensuring effective focal length distribution, thereby improving aberrations, correcting chromatic aberration, and guaranteeing the quality of the projected image.

[0048] In this application, the first lens L1 has a concave first side surface and a concave or convex second side surface; the second lens L2 has a concave first side surface and a concave second side surface; the third lens L3 has a convex first side surface and a convex second side surface; the fourth lens L4 has a planar, concave, or convex first side surface and a concave or convex second side surface; the fifth lens L5 has both a convex first side surface and both a concave second side surface; the sixth lens L6 has a convex or concave first side surface and a convex second side surface; the seventh lens L7 has a concave or convex first side surface and a convex second side surface; the eighth lens L8 has a concave first side surface and a convex or concave second side surface; the ninth lens L9 has a convex first side surface and a convex second side surface; the tenth lens L10 has a convex first side surface and a convex second side surface; and the eleventh lens L11 has a convex first side surface and a convex second side surface. By carefully designing the lens surface shape, various aberrations are effectively reduced, maintaining high image clarity and sharpness even under high-resolution projection conditions. This makes it ideal for high-resolution projections such as 4K and 8K, meeting the demanding detail requirements of professional users. Furthermore, this also helps improve the uniformity of the projected image, ensuring consistent brightness and color across every area of ​​the screen, making it suitable for display applications requiring high image uniformity.

[0049] Specifically, the radius of curvature of the first side of the first lens L1 is greater than or equal to -30mm and less than or equal to -10mm; the radius of curvature of the first side of the second lens L2 is greater than or equal to -60mm and less than or equal to -27mm, and the radius of curvature of the second side is greater than or equal to 10mm and less than or equal to 43mm; the radius of curvature of the first side of the third lens L3 is greater than or equal to 43mm and less than or equal to 100mm, and the radius of curvature of the second side is greater than or equal to -80mm and less than or equal to -40mm; the radius of curvature of the second side of the sixth lens L6 is greater than or equal to -63mm and less than or equal to -13mm; the radius of curvature of the second side of the seventh lens L7 is greater than or equal to -400mm and less than or equal to -21mm; and the radius of curvature of the first side of the eighth lens L8 is greater than or equal to -416mm and less than or equal to -21mm. This high-precision radius of curvature design makes the refraction of light through the lenses more accurate, reduces edge aberrations, and improves the uniformity and resolution of the entire image.

[0050] Specifically, the diameter of each lens in the lens group is greater than 0 mm and less than 35 mm. By limiting the diameter of the lenses, it is possible to miniaturize the projection lens, making it suitable for portable and space-constrained projection devices, such as micro projectors and embedded projection systems, providing users with a wider range of application options and a better user experience.

[0051] Specifically, the total optical length (TTL) of the projection lens and the total focal length (EFL) of the projection lens satisfy the following condition: 8 ≤ TTL / EFL ≤ 14. Specifically, TTL is the on-axis distance from the first side surface of the first lens L1 to the LCOS chip 60. Constraining this condition helps to compress the overall system length to achieve miniaturization. In different embodiments of this application, TTL / EFL = 8.5, 9.3, 11.5, 13.0, 13.2, and 13.2.

[0052] Specifically, the back focal length (BFL) of the projection lens and the total optical length (TTL) of the projection lens satisfy the following condition: 0.2 ≤ BFL / TTL ≤ 0.4. Specifically, BFL is the on-axis distance from the second side surface of the last lens on the second side of the lens group to the LCOS chip 60. This setting helps ensure that the back focal length meets adjustment requirements, achieving adjustable functionality while maintaining miniaturization. In different embodiments of this application, BFL / TTL = 0.2, 0.3, and 0.4. The back focal length of the projection lens can also be called the back focal length; the back focal length of the projection lens refers to the distance on the optical axis between the second side surface of the lens closest to the LCOS chip and the LCOS chip.

[0053] Specifically, the back focal length (BFL) and total focal length (EFL) of the projection lens satisfy the following ratio: 3 ≤ BFL / EFL ≤ 4. This setting significantly optimizes the imaging performance and structural compactness of the projection lens. This ratio ensures sufficient back focal space, which is beneficial for internal layout design, while avoiding an increase in the overall length of the projection lens due to an excessively long back focal length. It helps maintain lens miniaturization, reduces weight, and makes the projection device more portable. Furthermore, an appropriate BFL / EFL ratio also helps improve MTF performance, reduce aberrations, and ensure high resolution and low distortion even when imaging over a wide area, presenting users with a clearer and more realistic image. In different embodiments of this application, BFL / EFL = 3.0, 3.3, 3.6, and 4.0.

[0054] Furthermore, the total focal length (EFL) of the projection lens satisfies: 5mm ≤ EFL ≤ 15mm. The aperture number (Fno) of the projection lens satisfies: 1 ≤ Fno ≤ 3. The total optical length (TTL) of the projection lens satisfies: 110mm ≤ TTL ≤ 135mm. The system field of view of the projection lens is greater than or equal to 60° and less than or equal to 30°; the ratio of the projection distance to the screen width (TR) of the projection lens satisfies: 0.8 ≤ TR ≤ 1.2. By reasonably optimizing optical parameters, such as the combination of short focal length and large field of view, the projection lens of this application can achieve large-screen projection within a limited space.

[0055] In summary, the projection lens of this application can effectively improve the chromatic aberration of the system and suppress the occurrence of system distortion. Under the design requirement of a target diameter of 12.5mm, the number of lenses used is small, the structure is simplified, the distortion is low, the cost is low, and a high performance MTF value can be ensured at high temperatures.

[0056] Furthermore, by optimizing the curvature, material properties, spacing, and coordination between aspherical lenses in the optical system, a large-aperture, high-performance, low-distortion fixed-focus projection lens is obtained. When used with a 0.37-inch LCOS chip, it can project a 90-inch image at a working distance of 2390mm. The projection lens exhibits good MTF performance in the visible light range of 460nm to 625nm at the spatial limit frequency of 118lp / mm, with low distortion of less than 0.5%. It also features a simple structure and good image quality.

[0057] Specifically, the projection lens also includes a galvanometer 20, an optical compensator, a polarizer 40, a protective glass 30, and an LCOS chip 60, sequentially arranged on the second side of the lens group away from the lens group. The optical compensator can be a half-wave plate 50. The LCOS chip 60 has a resolution of 118 lp / mm. The galvanometer 20 can be a dithering galvanometer, enabling the projection lens to simultaneously obtain the inherent resolution of the LCOS chip 60 when the galvanometer 20 is stationary and the 4K high resolution when the galvanometer 20 is dithering.

[0058] The projection lens of this application will now be described with reference to preferred embodiments and accompanying drawings. It should be noted that the following embodiments are merely preferred embodiments and should not be construed as limiting the scope of this application.

[0059] Example 1

[0060] like Figures 1 to 3 As shown, the projection lens of Embodiment 1 is described. Figure 1 A schematic diagram of the projection lens of Embodiment 1 is shown.

[0061] like Figure 1As shown, the projection lens, from the first side to the second side, includes a first lens group, an aperture stop (STO), a second lens group, a galvanometer 20, a half-wave plate 50, a polarizer 40, a protective glass 30, and an LCOS chip 60. The first lens group, from the first side to the second side, sequentially includes a first lens L1 with negative optical power, a second lens L2 with negative optical power, and a third lens L3 with positive optical power. The second lens group, from the first side to the second side, sequentially includes a fourth lens L4 with negative optical power, a fifth lens L5 with positive optical power, a sixth lens L6 with positive optical power, a seventh lens L7 with negative optical power, an eighth lens L8 with positive optical power, and a ninth lens L9 with positive optical power. In this embodiment, focusing is achieved through the second lens group; that is, when the projection distance (i.e., the distance from the object surface to the projection side) changes to obtain different image sizes, focusing can be achieved by adjusting the interval between the second lens group and the LCOS chip 60.

[0062] In this embodiment, the first lens L1 has a concave first side and a concave second side. The second lens L2 has a concave first side and a concave second side. The third lens L3 has a convex first side and a convex second side. The fourth lens L4 has a flat first side and a concave second side. The fifth lens L5 has a convex first side and a convex second side. The sixth lens L6 has a convex first side and a convex second side. The seventh lens L7 has a concave first side and a convex second side. The eighth lens L8 has a concave first side and a convex second side. The ninth lens L9 has a convex first side and a convex second side.

[0063] In this embodiment, the fourth lens L4 and the fifth lens L5 are cemented together to form a cemented doublet, and the sixth lens L6 and the seventh lens L7 are cemented together to form a cemented doublet. The two cemented doublets can be made of a combination of a low-refractive-index, high-Abbe-number material and a high-refractive-index, low-Abbe-number material, allowing for achromatic design and ensuring minimal chromatic aberration in the entire optical system. Optionally, the fourth lens L4 can be configured to have positive optical power, the fifth lens L5 to have negative optical power, the sixth lens L6 to have negative optical power, and the seventh lens L7 to have positive optical power.

[0064] In this embodiment, the radius of curvature of the first side of the first lens L1 is greater than or equal to -30 mm and less than or equal to -10 mm, and the radius of curvature of the second side is greater than or equal to 70 mm and less than or equal to 100 mm. The radius of curvature of the first side of the second lens L2 is greater than or equal to -60 mm and less than or equal to -30 mm, and the radius of curvature of the second side is greater than or equal to 10 mm and less than or equal to 30 mm. The radius of curvature of the first side of the third lens L3 is greater than or equal to 60 mm and less than or equal to 100 mm, and the radius of curvature of the second side is greater than or equal to -80 mm and less than or equal to -40 mm. The radius of curvature of the first side of the fourth lens L4 is greater than or equal to -100 mm and less than or equal to 0 mm, and the radius of curvature of the second side is greater than or equal to 0 mm and less than or equal to 35 mm. The radius of curvature of the first side of the fifth lens L5 is greater than or equal to 0 mm and less than or equal to 35 mm, and the radius of curvature of the second side is greater than or equal to -60 mm and less than or equal to -15 mm. The radius of curvature of the first side of the sixth lens L6 is greater than or equal to 20 mm and less than or equal to 60 mm, and the radius of curvature of the second side is greater than or equal to -63 mm and less than or equal to -13 mm. The radius of curvature of the first side of the seventh lens L7 is greater than or equal to -30 mm and less than or equal to 0 mm, and the radius of curvature of the second side is greater than or equal to -150 mm and less than or equal to -100 mm. The radius of curvature of the first side of the eighth lens L8 is greater than or equal to -416 mm and less than or equal to -370 mm, and the radius of curvature of the second side is greater than or equal to -50 mm and less than or equal to -21 mm. The radius of curvature of the first side of the ninth lens L9 is greater than or equal to 60 mm and less than or equal to 90 mm, and the radius of curvature of the second side is greater than or equal to -90 mm and less than or equal to -40 mm.

[0065] Table 1 below shows the basic structural parameters of the projection lens in Embodiment 1.

[0066] Table 1

[0067]

[0068]

[0069] In Embodiment 1, the first lens L1 is an aspherical lens and a resin lens, while the remaining lenses are all spherical lenses. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formula:

[0070]

[0071] In the formula, parameter c is the curvature corresponding to the radius of curvature, r is the radial height of the lens, k is the conic constant, and α1 to α7 are the aspherical coefficients corresponding to orders two to fourteen, respectively. Table 2 below shows the conic constant k and the aspherical coefficients α2 to α7 that can be used for the aspherical lens surfaces S1 and S2 in Example 1.

[0072] When the coefficient k is less than -1, the surface shape of the lens is a hyperbola; when the coefficient k is equal to -1, the surface shape of the lens is a parabola; when the coefficient k is between -1 and 0, the surface shape of the lens is an ellipse; when the coefficient k is equal to 0, the surface shape of the lens is a circle; when the coefficient k is greater than 0, the surface shape of the lens is an oval.

[0073] Table 2

[0074] k α2 α3 α4 α5 α6 α7 α8 S1 0 3.68E-04 -3.24E-06 2.23E-08 -1.45E-10 3.58E-13 -5.99E-16 4.71E-19 S2 0 3.32E-04 -1.35E-06 -1.63E-08 3.67E-10 -3.13E-12 1.29E-14 -2.17E-17

[0075] Figure 2 The field curvature diagram of the projection lens in this embodiment is shown. Figure 3 The distortion diagram of the projection lens in this embodiment is shown. Figure 2 and Figure 3 It can be seen that the projection lens in this embodiment can achieve good projection quality.

[0076] Example 2

[0077] like Figure 4 As shown, the projection lens of Embodiment 2 is described. Figure 4 A schematic diagram of the projection lens in Embodiment 2 is shown.

[0078] like Figure 4 As shown, the projection lens, from the first side to the second side, includes a first lens group, an aperture stop (STO), a second lens group, a galvanometer 20, a half-wave plate 50, a polarizer 40, a protective glass 30, and an LCOS chip 60. The first lens group, from the first side to the second side, sequentially includes a first lens L1 with negative optical power, a second lens L2 with negative optical power, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a fifth lens L5 with positive optical power, and a sixth lens L6 with negative optical power. The second lens group, from the first side to the second side, sequentially includes a seventh lens L7 with positive optical power, an eighth lens L8 with negative optical power, a ninth lens L9 with positive optical power, a tenth lens L10 with positive optical power, and an eleventh lens L11 with positive optical power.

[0079] In this embodiment, the first lens L1 has a concave first side and a convex second side. The second lens L2 has a concave first side and a concave second side. The third lens L3 has a convex first side and a convex second side. The fourth lens L4 has a concave first side and a concave second side. The fifth lens L5 has a convex first side and a convex second side. The sixth lens L6 has a concave first side and a convex second side. The seventh lens L7 has a convex first side and a convex second side. The eighth lens L8 has a concave first side and a concave second side. The ninth lens L9 has a convex first side and a convex second side. The tenth lens L10 has a convex first side and a convex second side. The eleventh lens L11 has a convex first side and a convex second side.

[0080] In this embodiment, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are cemented together to form a cemented triplet lens, which can effectively control transverse chromatic aberration. The seventh lens L7, the eighth lens L8, and the ninth lens L9 are cemented together to form a cemented triplet lens. In this embodiment, a cemented triplet lens is used before and after the aperture stop STO to replace the two cemented doublet lenses in the second lens group in Embodiment 1, which can effectively increase the aperture number and provide less brightness loss for the projection lens.

[0081] Table 3 below shows the basic structural parameters of the projection lens in Embodiment 2.

[0082] Table 3

[0083]

[0084]

[0085] In Example 2, the first lens L1 is an aspherical lens, while the remaining lenses are all spherical lenses. Table 4 below shows the conic quadratic coefficient k and the aspherical coefficients α2 to α7 of the aspherical lens surfaces S1 and S2 that can be used in Example 2.

[0086] Table 4

[0087] k α2 α3 α4 α5 α6 α7 α8 S1 0 0.0002 -1.5E-06 7.7E-08 -1.5E-10 3.52E-12 -2.3E-13 4.73E-14 S2 0 7.32E-04 -1.35E-06 -9.63E-08 5.67E-10 -3.1E-12 1.59E-13 -2.1E-13

[0088] Example 3

[0089] like Figure 5 As shown, the projection lens of Embodiment 3 is described. Figure 5 A schematic diagram of the projection lens in Embodiment 3 is shown.

[0090] like Figure 5As shown, the projection lens, from the first side to the second side, includes a first lens group, an aperture stop (STO), a second lens group, a galvanometer 20, a half-wave plate 50, a polarizer 40, a protective glass 30, and an LCOS chip 60. The first lens group, from the first side to the second side, sequentially includes a first lens L1 with negative optical power, a second lens L2 with negative optical power, and a third lens L3 with positive optical power. The second lens group, from the first side to the second side, sequentially includes a fourth lens L4 with positive optical power, a fifth lens L5 with negative optical power, a sixth lens L6 with positive optical power, a seventh lens L7 with positive optical power, and an eighth lens L8 with positive optical power.

[0091] In this embodiment, the first lens L1 has a concave first side and a concave second side. The second lens L2 has a concave first side and a concave second side. The third lens L3 has a convex first side and a convex second side. The fourth lens L4 has a convex first side and a convex second side. The fifth lens L5 has a concave first side and a concave second side. The sixth lens L6 has a convex first side and a convex second side. The seventh lens L7 has a convex first side and a convex second side. The eighth lens L8 has a concave first side and a convex second side.

[0092] In this embodiment, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are cemented together to form a cemented triplet lens, which is used for chromatic aberration correction and thermal compensation. This embodiment replaces the two cemented doublet lenses in the second lens group of Embodiment 1 with a single cemented triplet lens, and replaces one spherical lens in the second lens group with a glass aspherical lens, effectively reducing the number of lenses.

[0093] Table 5 below shows the basic structural parameters of the projection lens in Embodiment 3.

[0094] Table 5

[0095]

[0096]

[0097] In Embodiment 3, the first lens L1 is a plastic aspherical lens, the seventh lens L7 is a glass aspherical lens, and the remaining lenses are all spherical lenses. This allows the aspherical lenses to handle the optical power of the optical system while reducing various aberrations. Table 6 below shows the conic conic section coefficient k and the aspherical coefficients α2 to α7 of the aspherical lens surfaces S1, S2, S14, and S15 that can be used in Embodiment 3.

[0098] Table 6

[0099] k α2 α3 α4 α5 α6 α7 α8 S1 0 3.38E-04 -3.24E-06 -2.23E-08 -1.45E-10 3.18E-13 -5.99E-16 4.71E-12 S2 0 3.52E-04 -5.35E-06 -7.63E-08 3.67E-10 -3.13E-12 1.29E-14 -2.17E-17 S14 0 4.61E-19 -3.67E-10 5.67E-10 -8.23E-08 5.58E-15 -1.63E-08 3.32E-04 S15 0 2.23E-08 2.23E-08 -3.78-06 -1.35E-06 4.72E-19 3.58E-13 -1.63E-08

[0100] In summary, the structural parameters of Embodiments 1 to 3 satisfy the parameters in Table 7 below. Wherein, Ф1 represents the maximum diameter of the lens, specifically the maximum diameter of the first lens L1.

[0101] Table 7

[0102]

[0103]

[0104] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0105] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0106] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A projection lens, characterized in that, Including lens group, The lens group includes at least eight lenses, which are arranged sequentially from the first side to the second side as follows: a first lens (L1) with negative optical power, a second lens (L2) with negative optical power, a third lens (L3) with positive optical power, a fourth lens (L4) with negative optical power, a fifth lens (L5) with positive optical power, a sixth lens (L6) with optical power, a seventh lens (L7) with optical power, and an eighth lens (L8) with optical power. Wherein, at least one of the first lens (L1) to the third lens (L3) is an aspherical lens, and the refractive index of at least one of the first lens (L1) to the third lens (L3) is greater than or equal to 1.8 and less than 2.0; or, At least two of the fourth lens (L4) to the eighth lens (L8) are glass lenses, and at least one lens has a refractive index greater than or equal to 1.6 and less than 2.0; or, At least one group of lenses from the fourth lens (L4) to the eighth lens (L8) is cemented together to form a cemented doublet lens or a cemented triplet lens; the ratio between the combined focal length of the cemented doublet lens and the focal length of the second lens group is greater than or equal to 1 and less than or equal to 8; or, the ratio between the focal length of the cemented triplet lens and the focal length of the second lens group is greater than or equal to 0 and less than or equal to 14, and the second lens group includes at least the seventh lens (L7) and the eighth lens (L8).

2. The projection lens according to claim 1, characterized in that, The lens group consists of eight lenses, wherein the sixth lens (L6), the seventh lens (L7), and the eighth lens (L8) have positive optical power; or, The lens group consists of nine lenses, including a ninth lens (L9) located on the second side of the eighth lens (L8). The sixth lens (L6) has positive optical power, the seventh lens (L7) has negative optical power, the eighth lens (L8) has positive optical power, and the ninth lens (L9) has positive optical power; or... The lens group consists of eleven lenses, including a ninth lens (L9), a tenth lens (L10), and an eleventh lens (L11) arranged sequentially on the second side of the eighth lens (L8). The sixth lens (L6) has negative optical power, the seventh lens (L7) has positive optical power, the eighth lens (L8) has negative optical power, the ninth lens (L9) has positive optical power, the tenth lens (L10) has positive optical power, and the eleventh lens (L11) has positive optical power.

3. The projection lens according to claim 2, characterized in that, The projection lens also includes an aperture stop (STO). When the lens group consists of eight or nine lenses, the aperture stop (STO) is located between the third lens (L3) and the fourth lens (L4) to divide the lens group into a first lens group and a second lens group. The first lens group includes the first lens (L1) to the third lens (L3), and the second lens group includes the fourth lens (L4) to the eighth lens (L8) or the fourth lens (L4) to the ninth lens (L9). When the lens group consists of eleven lenses, the aperture stop (STO) is located between the sixth lens (L6) and the seventh lens (L7) to divide the lens group into a first lens group and a second lens group. The first lens group includes the first lens (L1) to the sixth lens (L6), and the second lens group includes the seventh lens (L7) to the eleventh lens (L11).

4. The projection lens according to claim 1, characterized in that, The first lens (L1) is an aspherical lens; and / or the refractive index dn of the eighth lens (L8) satisfies the following relationship with the temperature dt of the eighth lens (L8): -8 <dn / dt<-2。 5. The projection lens according to claim 3, characterized in that, The second lens group includes at least one cemented doublet or cemented triplets, wherein at least one of the cemented doublet or cemented triplets has an Abbe number greater than or equal to 55 and less than or equal to 95.

6. The projection lens according to claim 1, characterized in that, The fourth lens and the fifth lens are cemented together to form a cemented doublet lens, and the sixth lens and the seventh lens are cemented together to form a cemented doublet lens. One lens in the cemented doublet lens has a positive optical power, and the other lens has a negative optical power. a combined focal length F of the fourth lens (L4) and the fifth lens (L5) L4～L5 satisfies: 4 ≤ F L4～L5 / F2 ≤ 7; and / or, The combined focal length F of the sixth lens (L6) and the seventh lens (L7) L6～L7 The focal length F2 of the second lens group satisfies the following condition: 2 ≤ F L6～L7 / F2≤6; and / or, The combined focal length F of the fourth lens (L4), the fifth lens (L5), the sixth lens (L6), and the seventh lens (L7) L4～L7 The focal length F2 of the second lens group satisfies the following condition: 2 ≤ F L4～L7 / F2≤5.

7. The projection lens according to claim 3, characterized in that, The seventh lens (L7), the eighth lens (L8), and the ninth lens (L9) are cemented together to form a cemented triplet lens, and the combined focal length F of the seventh lens (L7), the eighth lens (L8), and the ninth lens (L9) is... L7～L9 The focal length F2 of the second lens group satisfies the following condition: 0 ≤ F L7～L9 / F2≤6; or, The fourth lens (L4), the fifth lens (L5), and the sixth lens (L6) are cemented together to form a cemented triplet lens, and the combined focal length F of the fourth lens (L4), the fifth lens (L5), and the sixth lens (L6) is... L4～L6 The focal length F2 of the second lens group satisfies the following condition: 2 ≤ F L4～L6 / F2≤13.

8. The projection lens according to claim 1, characterized in that, The first lens group includes at least the first lens (L1), the second lens (L2), and the third lens (L3), and the projection lens satisfies at least one of the following conditions: The focal length F1 of the first lens group satisfies: -140mm ≤ F1 ≤ -25mm; The focal length F2 of the second lens group satisfies: -30mm ≤ F2 ≤ -5mm; The focal length F1 of the first lens group and the total focal length EFL of the projection lens satisfy the following relationship: -13.5 ≤ F1 / EFL ≤ -3.5; The focal length F2 of the second lens group and the total focal length EFL of the projection lens satisfy -5≤F2 / EFL≤0mm.

9. The projection lens according to claim 2, characterized in that, The first lens (L1) has a concave first side and a concave or convex second side; the second lens (L2) has a concave first side and a concave second side; the third lens (L3) has a convex first side and a convex second side; the fourth lens (L4) has a planar, concave, or convex first side and a concave or convex second side; the fifth lens (L5) has a convex first side and a concave second side; the sixth lens (L6) has a convex or concave first side and a convex second side; the seventh lens (L7) has a concave or convex first side and a convex second side; the eighth lens (L8) has a concave first side and a convex or concave second side; the ninth lens (L9) has a convex first side and a convex second side; the tenth lens (L10) has a convex first side and a convex second side; and the eleventh lens (L11) has a convex first side and a convex second side.

10. The projection lens according to any one of claims 1 to 9, characterized in that, The projection lens satisfies at least one of the following conditions: The diameter of each lens in the lens group is greater than 0 mm and less than 35 mm; The optical total length (TTL) of the projection lens and the total focal length (EFL) of the projection lens satisfy the following relationship: 8 ≤ TTL / EFL≤14; The back focal length (BFL) of the projection lens and the total optical length (TTL) of the projection lens satisfy the following condition: 0.2 ≤ BFL / TTL≤0.4; The back focal length (BFL) of the projection lens and the total focal length (EFL) of the projection lens satisfy the following condition: 3 ≤ BFL / EFL≤4; The total focal length (EFL) of the projection lens satisfies: 5mm ≤ EFL ≤ 15mm; The aperture number Fno of the projection lens satisfies: 1≤Fno≤3; The total optical length (TTL) of the projection lens satisfies: 110mm ≤ TTL ≤ 135mm; The system field of view of the projection lens is greater than or equal to 60° and less than or equal to 30°; The ratio TR of the projection distance to the screen width of the projection lens satisfies: 0.8 ≤ TR ≤ 1.2.

Images