Projection lens

Abstract

The present invention provides a projection lens, which has six lenses in total. Along the optical axis, from the projection surface to the image source surface, it successively includes: a first lens with a negative optical power; a second lens with a positive optical power, whose projection side surface is convex; a third lens with a negative optical power, whose projection side surface is convex and whose image source side surface is concave; a fourth lens with a negative optical power, whose projection side surface and image source side surface are both concave; a fifth lens with a positive optical power, whose projection side surface and image source side surface are both convex; a sixth lens with a positive optical power, whose projection side surface is concave and whose image source side surface is convex; the focal length f3 of the third lens and the focal length f6 of the sixth lens satisfy: -2.2 < f3 / f6 < -1.5; the curvature radius R5 of the projection side surface of the third lens and the curvature radius R11 of the projection side surface of the sixth lens satisfy: -8.7 < (R5 - R11) / (R5 + R11) < -3.9. The projection lens provided by the present invention improves the projection quality of the projection lens through the reasonable configuration of the surface types of each lens and the reasonable matching of the optical powers.

Description

Technical Field

[0001] The present invention relates to the technical field of imaging lenses, and in particular to a projection lens. Background Art

[0002] As people's requirements for driving experience continue to increase, the use of in-vehicle application projection lenses in intelligent driving is increasing, and the status of in-vehicle projection lenses in the automotive-related industry is constantly improving. The head-up display system (HUD), also known as the automotive head-up display system, uses the principle of optical reflection to project the car's driving assistance information, navigation information, check control information, and ADAS information on the windshield or about 2 meters in front, above the tip of the engine hood. At the same time, it can also display warning information from various driving assistance systems, such as lane departure warnings, pedestrian avoidance warnings from night vision assistance systems with pedestrian recognition functions, etc., to prevent drivers from frequently looking down at the instrument or in-vehicle screen during driving, which plays a good auxiliary role in driving safety.

[0003] However, the projection lenses used for vehicle-mounted HUD on the market have defects such as large size, unstable performance under high and low temperature conditions, dark corners in the projected patterns, insufficient brightness on the projection surface, resulting in unclear patterns, etc., which are difficult to meet usage requirements. Summary of the invention

[0004] In view of the above problems, an object of the present invention is to provide a projection lens having the advantage of excellent imaging quality.

[0005] The present invention provides a projection lens, which has six lenses in total, and includes the following lenses in order from the projection surface to the image source surface along the optical axis:

[0006] a first lens having negative optical power;

[0007] A second lens having positive refractive power, whose projection side surface is convex;

[0008] a third lens having negative power, whose projection side surface is convex and whose image source side surface is concave;

[0009] A fourth lens having negative optical power, wherein both a projection side surface and an image source side surface thereof are concave surfaces;

[0010] A fifth lens having positive refractive power, wherein both a projection side surface and an image source side surface thereof are convex surfaces;

[0011] a sixth lens having positive refractive power, whose projection side surface is concave and whose image source side surface is convex;

[0012] Among them, the focal length f3 of the third lens and the focal length f6 of the sixth lens satisfy: -2.2 < f3 / f6 < -1.5; the curvature radius R5 of the projection-side surface of the third lens and the curvature radius R11 of the projection-side surface of the sixth lens satisfy: -8.7 < (R5 - R11) / (R5 + R11) < -3.9.

[0013] Further preferably, the effective focal length f of the projection lens and the overall optical length TTL of the projection lens satisfy: 4.2 < TTL / f < 4.9; the overall optical length TTL of the projection lens and the true image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 5.1 < TTL / IH < 5.7.

[0014] Further preferably, the maximum field of view angle FOV of the projection lens and the f-number Fno of the projection lens satisfy: 16.9° < FOV / Fno < 17.4°; the true image height IH corresponding to the maximum field of view angle of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 2.3 < IH / EPD < 2.6.

[0015] Further preferably, the clear aperture radius d1 of the projection-side surface of the first lens, the true image height IH corresponding to the maximum field of view angle of the projection lens, and the maximum field of view angle FOV of the projection lens satisfy: 4.4 < d1 / (IH / 2) / tan(FOV / 2) < 5; the clear aperture radius d1 of the projection-side surface of the first lens and the clear aperture radius d12 of the image-source-side surface of the sixth lens satisfy: 1.5 < d1 / d12 < 1.7.

[0016] Further preferably, the effective focal length f of the projection lens and the focal length f1 of the first lens satisfy: -6.1 < f1 / f < -3.5; the curvature radius R1 of the projection-side surface of the first lens and the curvature radius R2 of the image-source-side surface of the first lens satisfy: 0.3 < R1 / R2 < 2.6.

[0017] Further preferably, the focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: -2.3 < f3 / f < -1.6; the curvature radius R5 of the projection-side surface of the third lens and the effective focal length f of the projection lens satisfy: 0.35 < R5 / f < 0.55; the curvature radius R6 of the image-source-side surface of the third lens and the effective focal length f of the projection lens satisfy: 0.2 < R6 / f < 0.3; the curvature radius R5 of the projection-side surface of the third lens and the curvature radius R6 of the image-source-side surface of the third lens satisfy: 0.25 < (R5 - R6) / (R5 + R6) < 0.35.

[0018] More preferably, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: -0.9 < f4 / f < -0.7; the effective focal length f of the projection lens and the curvature radius R7 of the projection-side surface of the fourth lens satisfy: -2.3 < R7 / f < -1.1; the effective focal length f of the projection lens and the curvature radius R8 of the image-source-side surface of the fourth lens satisfy: 1 < R8 / f < 1.7.

[0019] More preferably, the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 0.6 < f5 / f < 0.8; the effective focal length f of the projection lens and the combined focal length f456 of the fourth lens, the fifth lens, and the sixth lens satisfy: 0.6 < f456 / f < 0.8.

[0020] More preferably, the focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 0.9 < f6 / f < 1.2; the curvature radius R11 of the projection-side surface of the sixth lens and the effective focal length f of the projection lens satisfy: -68 < R11 / f < -33; the curvature radius R12 of the image-source-side surface of the sixth lens and the effective focal length f of the projection lens satisfy: -0.7 < R12 / f < -0.5.

[0021] More preferably, the curvature radius R11 of the projection-side surface of the sixth lens and the curvature radius R12 of the image-source-side surface of the sixth lens satisfy: 56 < R11 / R12 < 104; the curvature radius R7 of the projection-side surface of the fourth lens and the curvature radius R8 of the image-source-side surface of the fourth lens satisfy: -0.2 < (R7 + R8) / (R7 - R8) < 0.4.

[0022] More preferably, the semi-aperture d11 of the projection-side surface of the sixth lens and the sagittal height Sag11 of the projection-side surface of the sixth lens satisfy: -0.1 < Sag11 / d11 < 0; the semi-aperture d12 of the image-source-side surface of the sixth lens and the sagittal height Sag12 of the image-source-side surface of the sixth lens satisfy: -0.6 < Sag12 / d12 < -0.45; a prism is provided between the sixth lens and the image source plane.

[0023] The projection lens provided by the present invention improves the imaging quality of the projection lens, reduces aberration, and improves the projection quality of the projection lens by reasonably configuring the surface shapes of each lens and reasonably matching the optical powers, enabling the lens to have one or more advantages such as small distortion, small CRA, large image plane, and high imaging quality. Description of the Drawings

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of the embodiments in conjunction with the accompanying drawings, where:

[0025] Figure 1 Schematic diagram of the structure of the projection lens in Embodiment 1 of the present invention.

[0026] Figure 2 is the F-Tan (Theta) distortion curve of the projection lens in Example 1 of the present invention.

[0027] Figure 3 : is the vertical axis chromatic aberration curve of the projection lens in Example 1 of the present invention.

[0028] Figure 4 is a relative illumination curve diagram of the projection lens in Example 1 of the present invention.

[0029] Figure 5 This is an MTF curve diagram of the projection lens in Example 1 of the present invention when the working temperature is 20°C.

[0030] Figure 6 This is an MTF curve diagram of the projection lens in Example 1 of the present invention when the working temperature is -40°C.

[0031] Figure 7 This is an MTF curve diagram of the projection lens in Example 1 of the present invention when the working temperature is 85°C.

[0032] Figure 8 Schematic diagram of the structure of the projection lens in Embodiment 2 of the present invention.

[0033] Fig. 9 is the F-Tan (Theta) distortion curve of the projection lens in Example 2 of the present invention.

[0034] Fig.10 Graph showing the vertical axis chromatic aberration of the projection lens in Embodiment 2 of the present invention.

[0035] Fig.11 is a relative illumination curve diagram of the projection lens in Example 2 of the present invention.

[0036] Fig.12 This is an MTF curve diagram of the projection lens in Example 2 of the present invention when the working temperature is 20°C.

[0037] Fig.13 This is an MTF curve diagram of the projection lens in Example 2 of the present invention when the working temperature is -40°C.

[0038] Fig.14 This is an MTF curve diagram of the projection lens in Example 2 of the present invention when the working temperature is 85°C.

[0039] Fig.15 Schematic diagram of the structure of the projection lens in Embodiment 3 of the present invention.

[0040] Fig.16 is the F-Tan (Theta) distortion curve of the projection lens in Example 3 of the present invention.

[0041] Fig.17 : is the vertical axis chromatic aberration curve of the projection lens in Example 3 of the present invention.

[0042] Fig.18 This is a relative illumination curve diagram of the projection lens in Example 3 of the present invention.

[0043] Fig.19 This is an MTF curve diagram of the projection lens in Example 3 of the present invention when the working temperature is 20°C.

[0044] Fig. 20 This is an MTF curve diagram of the projection lens in Example 3 of the present invention when the working temperature is -40°C.

[0045] Fig.21 This is an MTF curve diagram of the projection lens in Example 3 of the present invention when the working temperature is 85°C.

[0046] Fig. 22 Schematic diagram of the structure of the projection lens in Embodiment 4 of the present invention.

[0047] Fig.23 is the F-Tan (Theta) distortion curve of the projection lens in Example 4 of the present invention.

[0048] Fig.24 4 is a vertical axis chromatic aberration curve of the projection lens in Example 4 of the present invention.

[0049] Fig.25 This is a relative illumination curve diagram of the projection lens in Example 4 of the present invention.

[0050] Fig.26 This is an MTF curve diagram of the projection lens in Example 4 of the present invention when the working temperature is 20°C.

[0051] Fig. 27 This is an MTF curve diagram of the projection lens in Example 4 of the present invention when the working temperature is -40°C.

[0052] Fig.28 This is an MTF curve diagram of the projection lens in Example 4 of the present invention when the working temperature is 85°C.

[0053] Fig.29 Schematic diagram of the structure of the projection lens in Embodiment 5 of the present invention.

[0054] Fig.30 is the F-Tan (Theta) distortion curve of the projection lens in Example 5 of the present invention.

[0055] Fig.31 : is the vertical axis chromatic aberration curve of the projection lens in Example 5 of the present invention.

[0056] Fig.32 This is a relative illumination curve diagram of the projection lens in Example 5 of the present invention.

[0057] Fig.33 This is an MTF curve diagram of the projection lens in Example 5 of the present invention when the working temperature is 20°C.

[0058] Fig.34 This is an MTF curve diagram of the projection lens in Example 5 of the present invention when the working temperature is -40°C.

[0059] Fig.35 This is an MTF curve diagram of the projection lens in Example 5 of the present invention when the working temperature is 85°C.

[0060] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0061] In order to better understand the present application, a more detailed description will be made of various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of the embodiments of the present application, and are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0062] It should be noted that in this specification, the expressions of first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching of the present invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0063] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of explanation. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are only examples and are not drawn strictly to scale.

[0064] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface 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 position of the concave surface 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 projection surface is called the projection side surface of the lens, and the surface of each lens closest to the image source surface is called the image source side surface of the lens.

[0065] It should also be understood that the terms "comprises", "including", "having", "includes" and / or "comprising", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0066] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this article have the same meaning as commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that terms (such as terms defined in commonly used dictionaries) should be interpreted as having the same meaning as their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0067] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0068] The projection lens provided by the embodiment of the present invention comprises six lenses in total, which are a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens in order from the projection plane to the image source plane along the optical axis.

[0069] In some embodiments, the first lens may have negative optical power, and its projection side surface may be concave or convex, and its image source side surface may be concave or convex. The second lens may have positive optical power, and its projection side surface is convex, and its image source side surface may be concave or convex. The third lens may have negative optical power, and its projection side surface is convex, and its image source side surface is concave. The fourth lens may have negative optical power, and its projection side surface and image source side surface are both concave. The fifth lens may have positive optical power, and its projection side surface and image source side surface are both convex. The sixth lens may have positive optical power, and its projection side surface is concave, and its image source side surface is convex.

[0070] In some embodiments, the projection lens further includes a prism, and the prism is disposed between the sixth lens and the image source surface. The prism is used to deflect the light beam emitted by the image source so that it is incident on the lens group at the front end of the projection lens, thereby reducing the volume of the projection lens. The prism can be a right-angle prism, and the direction of the light path can be changed by setting the right-angle prism, and the light path can be bent so that the direction of the incident light is perpendicular to the arrangement direction of the multiple lenses, thereby reducing the overall thickness of the optical system.

[0071] In some embodiments, the projection lens may further include a diaphragm, which may be located between the third lens and the fourth lens. It can be understood that the diaphragm is used to limit the amount of incident light to change the brightness of the image. When the diaphragm is located between the third lens and the fourth lens, it is convenient for correcting the diaphragm aberration.

[0072] In some embodiments, the projection lens may further include a protective glass, which may be disposed between the prism and the image source surface. The protective glass plays a role in protecting the projection lens, preventing the photosensitive chip from being damaged, and can improve the shock resistance and scratch resistance of the projection lens, while having almost no impact on the imaging quality of the projection lens.

[0073] In some embodiments, the fourth lens and the fifth lens may be glued together to form a glued lens group with positive optical power, which can effectively correct the chromatic aberration of the projection lens, reduce the eccentricity sensitivity of the projection lens, balance the aberration of the projection lens, and improve the imaging quality of the projection lens; it can also reduce the assembly sensitivity of the projection lens, thereby reducing the processing difficulty of the projection lens and improving the assembly yield of the projection lens.

[0074] In some embodiments, the focal length f3 of the third lens and the focal length f6 of the sixth lens satisfy: -2.2 < f3 / f6 < -1.5. By satisfying the above range and limiting the focal length ratio of the third lens and the sixth lens, the light deflection angle can be reduced, the light path can be made more stable, the aberration can be corrected, the imaging flatness can be improved, and the imaging quality of the projection lens can be improved. More specifically, -2.12 < f3 / f6 < -1.51.

[0075] In some embodiments, the curvature radius R5 of the projection side surface of the third lens and the curvature radius R11 of the projection side surface of the sixth lens satisfy: -8.7 < (R5 - R11) / (R5 + R11) < -3.9. By satisfying the above range and reasonably defining the shapes of the projection side surfaces of the third lens and the sixth lens, it helps to balance the high-order aberration of the projection lens and improve the imaging quality of the projection lens. More specifically, -8.7 < (R5 - R11) / (R5 + R11) < -3.99.

[0076] In some embodiments, the effective focal length f of the projection lens and the optical total length TTL of the projection lens satisfy: 4.2 < TTL / f < 4.9. By satisfying the above range, the long focal length characteristic of the lens can be realized, the length of the lens can be effectively limited, which is beneficial to the miniaturization of the projection lens. More specifically, 4.27 < TTL / f < 4.88.

[0077] In some embodiments, the total optical length TTL of the projection lens and the true image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 5.1 < TTL / IH < 5.7. Meeting the above range is conducive to achieving a balance between the volume of the projection lens and the large image plane. More specifically, 5.13 < TTL / IH < 5.65.

[0078] In some embodiments, the maximum field of view angle FOV of the projection lens and the f-number Fno of the projection lens satisfy: 16.9° < FOV / Fno < 17.4°. Meeting the above range defines that the projection lens has an appropriate field of view angle and f-number, can collect light at large angles and obtain good imaging quality. More specifically, 16.94° < FOV / Fno < 17.4°.

[0079] In some embodiments, the true image height IH corresponding to the maximum field of view angle of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 2.3 < IH / EPD < 2.6. Meeting the above range can increase the width of the light beam incident on the projection lens, improve the relative illumination, and avoid vignetting. More specifically, 2.31 < IH / EPD < 2.56.

[0080] In some embodiments, the clear aperture semi-diameter d1 of the projection side surface of the first lens, the true image height IH corresponding to the maximum field of view angle of the projection lens, and the maximum field of view angle FOV of the projection lens satisfy: 4.4 < d1 / (IH / 2) / tan(FOV / 2) < 5. Meeting the above range can have a small front aperture while meeting the requirements of a large field of view angle and a large image plane for the projection lens, which is beneficial to the miniaturization of the projection lens. More specifically, 4.41 < d1 / (IH / 2) / tan(FOV / 2) < 4.98.

[0081] In some embodiments, the clear aperture semi-diameter d1 of the projection side surface of the first lens and the clear aperture semi-diameter d12 of the image source side surface of the sixth lens satisfy: 1.5 < d1 / d12 < 1.7. Meeting the above range rationally matches the aperture ratio of the first lens and the sixth lens, facilitates the structural design, and at the same time helps to improve the imaging quality of the projection lens. More specifically, 1.5 < d1 / d12 < 1.69.

[0082] In some embodiments, the effective focal length f of the projection lens and the focal length f1 of the first lens satisfy: -6.1 < f1 / f < -3.5; the radius of curvature R1 of the projection-side surface of the first lens and the radius of curvature R2 of the image-source-side surface of the first lens satisfy: 0.3 < R1 / R2 < 2.6. Satisfying the above ranges can make the first lens have an appropriate negative optical power and surface shape, reduce the degree of deflection of incident light, help light enter the optical system within a larger range, and is beneficial to expanding the field of view angle of the lens. More specifically, -6.04 < f1 / f < -3.55; 0.32 < R1 / R2 < 2.55.

[0083] In some embodiments, the focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: -2.3 < f3 / f < -1.6; the radius of curvature R5 of the projection-side surface of the third lens and the effective focal length f of the projection lens satisfy: 0.35 < R5 / f < 0.55; the radius of curvature R6 of the image-source-side surface of the third lens and the effective focal length f of the projection lens satisfy: 0.2 < R6 / f < 0.3; the radius of curvature R5 of the projection-side surface of the third lens and the radius of curvature R6 of the image-source-side surface of the third lens satisfy: 0.25 < (R5 - R6) / (R5 + R6) < 0.35. Satisfying the above ranges, by reasonably setting the focal length and surface shape of the third lens, it is beneficial to the smooth transition of light, while correcting various aberrations of the projection lens and improving the imaging quality of the projection lens. More specifically, -2.28 < f3 / f < -1.68; 0.38 < R5 / f < 0.52; 0.22 < R6 / f < 0.28; 0.26 < (R5 - R6) / (R5 + R6) < 0.33.

[0084] In some embodiments, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: -0.9 < f4 / f < -0.7; the effective focal length f of the projection lens and the radius of curvature R7 of the projection-side surface of the fourth lens satisfy: -2.3 < R7 / f < -1.1; the effective focal length f of the projection lens and the radius of curvature R8 of the image-source-side surface of the fourth lens satisfy: 1 < R8 / f < 1.7. Satisfying the above ranges can make the fourth lens have an appropriate negative optical power, increase the imaging area of the lens, optimize the chromatic aberration of the lens, and improve the imaging quality. More specifically, -0.84 < f4 / f < -0.7; -2.22 < R7 / f < -1.14; 1.08 < R8 / f < 1.66.

[0085] In some embodiments, the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 0.6 < f5 / f < 0.8. Satisfying the above ranges can make the fifth lens have an appropriate positive optical power, which is beneficial to converging light while reducing the light deflection angle, making the light trend transition smoothly, and improving the projection quality of the projection lens. More specifically, 0.66 < f5 / f < 0.77.

[0086] In some embodiments, the effective focal length f of the projection lens and the combined focal length f456 of the fourth lens, the fifth lens, and the sixth lens satisfy: 0.6 < f456 / f < 0.8. Meeting the above conditions is beneficial to balancing the aberrations generated by the front lens group of the aperture stop and improving the imaging quality of the projection lens. More specifically, 0.67 < f456 / f < 0.78.

[0087] In some embodiments, the focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 0.9 < f6 / f < 1.2; the radius of curvature R11 of the projection-side surface of the sixth lens and the effective focal length f of the projection lens satisfy: -68 < R11 / f < -33; the radius of curvature R12 of the image-source-side surface of the sixth lens and the effective focal length f of the projection lens satisfy: -0.7 < R12 / f < -0.5; the radius of curvature R11 of the projection-side surface of the sixth lens and the radius of curvature R12 of the image-source-side surface of the sixth lens satisfy: 56 < R11 / R12 < 104. Meeting the above ranges can make the sixth lens have an appropriate positive optical power and surface shape, which is beneficial to converging light while reducing the light deflection angle, enabling the light to transition smoothly, and improving the projection quality of the projection lens. More specifically, 0.99 < f6 / f < 1.12; -67.01 < R11 / f < -33.03; -0.67 < R12 / f < -0.58; 56.28 < R11 / R12 < 103.69.

[0088] In some embodiments, the radius of curvature R7 of the projection-side surface of the fourth lens and the radius of curvature R8 of the image-source-side surface of the fourth lens satisfy: -0.2 < (R7 + R8) / (R7 - R8) < 0.4. Meeting the above range can receive as much light as possible from the front-edge field of view of the projection lens; at the same time, it can correct spherical aberration and field curvature, reducing the aberration correction pressure on the rear lenses of the projection lens; and it is beneficial to the smooth trend of light and improving the imaging quality of the projection lens. More specifically, -0.19 < (R7 + R8) / (R7 - R8) < 0.35.

[0089] In some embodiments, the clear aperture semi-diameter d11 of the projection-side surface of the sixth lens and the sagittal height Sag11 of the projection-side surface of the sixth lens satisfy: -0.1 < Sag11 / d11 < 0; the clear aperture semi-diameter d12 of the image-source-side surface of the sixth lens and the sagittal height Sag12 of the image-source-side surface of the sixth lens satisfy: -0.6 < Sag12 / d12 < -0.45. Meeting the above ranges helps to control the trend of light in the edge field of view and highlight the detailed information in the central field of view of the projection lens. More specifically, -0.08 < Sag11 / d11 < -0.03; -0.57 < Sag12 / d12 < -0.49.

[0090] In some embodiments, the effective focal length f of the projection lens and the true image height IH corresponding to the maximum field of view angle satisfy: 0.8 < IH / f < 1. Meeting the above range helps to achieve a large image plane and improve the imaging quality of the projection lens. More specifically, 0.82 < IH / f < 0.92.

[0091] In some embodiments, the effective focal length f of the projection lens and the back focal length BFL of the projection lens satisfy: 1.1 < BFL / f < 1.3. Meeting the above range is beneficial to achieving a balance between obtaining good imaging quality and an optical back focal length that is easy to assemble. While ensuring the imaging quality of the projection lens, it avoids interference between the lens and other components and reduces the assembly process difficulty of the lens module. More specifically, 1.1 < BFL / f < 1.27.

[0092] In some embodiments, the total optical length TTL of the projection lens and the sum ∑CT of the central thicknesses of the first lens to the sixth lens along the optical axis satisfy: 0.3 < ∑CT / TTL < 0.5. Meeting the above range can effectively compress the total length of the projection lens and is beneficial to the structural design and production process of the projection lens. More specifically, 0.33 < ∑CT / TTL < 0.5.

[0093] In some embodiments, the sum ∑CT of the central thicknesses of the first lens to the sixth lens along the optical axis and the effective focal length f of the projection lens satisfy: 1.5 < ∑CT / f < 2.1. Meeting the above range can effectively correct the field curvature and distortion of the projection lens and improve the imaging quality of the projection lens. More specifically, 1.58 < ∑CT / f < 2.1.

[0094] In some embodiments, the effective focal length f of the projection lens and the focal length f2 of the second lens satisfy: 1.5 < f2 / f < 2.5. Meeting the above range can make the second lens have an appropriate positive optical power, effectively balance the lens aberration, and improve the imaging quality. More specifically, 1.53 < f2 / f < 2.41.

[0095] In some embodiments, the combined focal length f45 of the fourth lens and the fifth lens and the effective focal length f of the projection lens satisfy: 1.9 < f45 / f < 2.8. Meeting the above range, by setting the fourth lens and the fifth lens to form a cemented lens with positive optical power, helps to reduce the chromatic aberration of the projection lens and improve the imaging quality of the projection lens. More specifically, 1.99 < f45 / f < 2.8.

[0096] In some embodiments, the projection lens satisfies the conditional formula: 14.9 mm < f < 16.6 mm, 5.3 mm < EPD < 6 mm, 70 mm < TTL < 76 mm, 2.7 < Fno < 2.9, 13 mm < IH < 14 mm, 47° < FOV < 49°, 17 mm < BFL < 19 mm, 0.1° < CRA < 1.3°; where f represents the effective focal length of the projection lens, EPD represents the entrance pupil diameter of the projection lens, TTL represents the total optical length of the projection lens, Fno represents the aperture value of the projection lens, IH represents the true image height corresponding to the maximum field of view angle of the projection lens, FOV represents the maximum field of view angle of the projection lens, BFL represents the back focal length of the projection lens, and CRA represents the chief ray angle of incidence CRA at the maximum image height of the projection lens. Meeting the above conditions indicates that the projection lens provided by the embodiments of the present invention has at least the characteristics of a small CRA, a large image plane, and a long back focal length. More specifically, 14.92 mm < f < 16.57 mm, 5.32 mm < EPD < 5.92 mm, 70.79 mm < TTL < 75.68 mm, 2.79 < Fno < 2.81, 13.41 mm < IH < 13.77 mm, 47.45° < FOV < 48.69°, 17.36 mm < BFL < 18.88 mm, 0.19° < CRA < 1.21°.

[0097] In some embodiments, the lens material in the projection lens provided by the present invention can be glass or plastic. When the lens material is plastic, the production cost can be effectively reduced. When the lens material is glass, the geometric chromatic aberration of the optical system can be effectively corrected by the low dispersion characteristic of the glass itself. More specifically, the six lenses in the projection lens provided by the present invention can all be glass lenses, which can improve the imaging stability of the projection lens in different temperature environments on the premise of meeting high pixels.

[0098] In some embodiments, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens can adopt spherical lenses or aspherical lenses. Compared with the spherical structure, the aspherical structure can effectively reduce the aberration of the optical system, thereby reducing the number of lenses and the size of the lenses, and better realizing the miniaturization of the lens. More specifically, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens in the projection lens provided by the present invention can adopt spherical lenses, and the sixth lens can adopt an aspherical lens.

[0099] In various embodiments of the present invention, when the lens adopts an aspherical lens, the shapes of the aspherical surfaces of the projection lens satisfy the following equation:

[0100] ;

[0101] Among them, z is the distance between the surface and the vertex of the surface in the direction of the optical axis, h is the distance from the optical axis to the surface, c is the curvature of the surface vertex, K is the quadratic surface coefficient, B, C, D, and E are the fourth-order, sixth-order, eighth-order, and tenth-order surface coefficients respectively.

[0102] The present invention is further described below in multiple embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the projection lens are different. For specific differences, please refer to the parameter table of each embodiment. The following embodiments are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments. Any other changes, substitutions, combinations or simplifications that do not deviate from the innovative points of the present invention should be regarded as equivalent replacement methods and are included in the protection scope of the present invention.

[0103] Example 1

[0104] See also Figure 1 , which is a schematic diagram of the structure of the projection lens 100 provided in Embodiment 1 of the present invention, wherein the projection lens 100 includes, in sequence from the projection surface to the image source surface along the optical axis: a first lens L1, a second lens L2, a third lens L3, an aperture ST, a fourth lens L4, a fifth lens L5, a sixth lens L6, a prism G1 and a protective glass G2.

[0105] The first lens L1 has negative optical power, its projection side surface S1 is convex, and its image source side surface S2 is concave;

[0106] The second lens L2 has positive refractive power, its projection side surface S3 is convex, and its image source side surface S4 is concave;

[0107] The third lens L3 has negative refractive power, its projection side surface S5 is convex, and its image source side surface S6 is concave;

[0108] The fourth lens L4 has negative refractive power, and its projection side surface S7 and image source side surface S8 are both concave surfaces;

[0109] The fifth lens L5 has positive refractive power, and its projection side surface S8 and image source side surface S9 are both convex surfaces;

[0110] The fourth lens L4 and the fifth lens L5 form a cemented lens group with positive refractive power, that is, the cemented surface of the image source side surface of the fourth lens L4 and the projection side surface of the fifth lens L5 is S8;

[0111] The sixth lens L6 has positive refractive power, a projection-side surface S10 thereof is a concave surface, and an image-source-side surface S11 thereof is a convex surface;

[0112] The prism G1 may be a right angle prism;

[0113] The projection side surface S12 and the image source side surface S13 of the protection glass G2 are both planes;

[0114] The image source surface S14 is a plane.

[0115] The first lens L1, the second lens L2, the third lens L3, the fourth lens L4 and the fifth lens L5 are all glass spherical lenses; the sixth lens L6 is a glass aspherical lens.

[0116] The relevant parameters of each lens in the projection lens 100 in Example 1 are shown in Table 1-1.

[0117] Table 1-1

[0118]

[0119] The surface parameters of the aspheric lens of the projection lens 100 in Example 1 are shown in Table 1-2.

[0120] Table 1-2

[0121]

[0122] Figure 2 The F-Tan (Theta) distortion curve of Example 1 is shown, which represents the F-Tan (Theta) distortion of light of different wavelengths at different image heights on the imaging surface, the horizontal axis represents the F-Tan (Theta) distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). It can be seen from the figure that the F-Tan (Theta) distortion of the projection lens is controlled within -3%~0, the image compression in the edge angle area is relatively gentle, and the clarity of the expanded image is effectively improved.

[0123] Figure 3 The vertical chromatic aberration curve of Example 1 is shown, which represents the chromatic aberration of each wavelength relative to the central wavelength (0.53 μm) at different image heights on the imaging surface, the horizontal axis represents the vertical chromatic aberration value of each wavelength relative to the central wavelength (unit: μm), and the vertical axis represents the normalized field angle. It can be seen from the figure that the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within -1 μm~4 μm, indicating that the projection lens can perfectly correct the chromatic aberration of the edge field of view and the secondary spectrum of the entire image surface.

[0124] Figure 4 The relative illumination curve of Example 1 is shown, which represents the relative illumination values ​​at different viewing angles on the imaging plane, the horizontal axis represents the half viewing angle (unit: °), and the vertical axis represents the relative illumination (unit: %). It can be seen from the figure that the relative illumination value of the projection lens is still greater than 78% at the maximum half viewing angle, indicating that the projection lens has good relative illumination.

[0125] Figure 5The MTF (Modulation Transfer Function) curve of Example 1 at an operating temperature of 20°C is shown, which represents the imaging modulation of the lens at different spatial frequencies in each field of view, the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.48 in the entire field of view, and in the range of 0 to 60 lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution under normal temperature conditions.

[0126] Figure 6 The MTF (Modulation Transfer Function) curve of Example 1 at an operating temperature of -40°C is shown, which represents the imaging modulation of the lens at different spatial frequencies in each field of view, the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.48 in the entire field of view, and in the range of 0 to 60 lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution under low temperature conditions.

[0127] Figure 7 The MTF (Modulation Transfer Function) curve of Example 1 at an operating temperature of 85°C is shown, which represents the imaging modulation of the lens at different spatial frequencies under each field of view, the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.48 in the entire field of view, and in the range of 0 to 60 lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution under high temperature conditions.

[0128] Example 2

[0129] See also Figure 8 , which is a schematic diagram of the structure of a projection lens 200 provided in Example 2 of the present invention. Compared with Example 1, this embodiment mainly differs in that the optical parameters such as the curvature radius of each lens surface and the lens thickness are different.

[0130] The relevant parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2-1.

[0131] Table 2-1

[0132]

[0133] The surface parameters of the aspherical lens of the projection lens 200 in Example 2 are shown in Table 2-2.

[0134] Table 2-2

[0135]

[0136] from Fig. 9 It can be seen that the F-Tan (Theta) distortion of the projection lens is controlled within -6%~0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the expanded image.

[0137] from Fig.10 It can be seen that the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within 0~4μm, which means that the projection lens can extremely well correct the chromatic aberration of the edge field of view and the secondary spectrum of the entire image plane.

[0138] from Fig.11 It can be seen that at the maximum half field of view angle, the relative illumination value of the projection lens is still greater than 78%, indicating that the projection lens has very good relative illumination.

[0139] from Fig.12 It can be seen that the MTF value of this embodiment is above 0.5 in the whole field of view when the working temperature is 20°C. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability at normal temperature.

[0140] from Fig.13 It can be seen that the MTF value of this embodiment is above 0.5 in the whole field of view when the working temperature is -40°C. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability under low temperature conditions.

[0141] from Fig.14 It can be seen that the MTF value of this embodiment when the working temperature is 85°C is above 0.5 in the whole field of view. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution under higher temperature conditions.

[0142] Example 3

[0143] See also Fig.15 , which is a schematic diagram of the structure of a projection lens 300 provided in Example 3 of the present invention. Compared with Example 1, the main differences of this embodiment are: the image source side surface S4 of the second lens L2 is a convex surface; and the optical parameters such as the curvature radius and lens thickness of each lens surface are different.

[0144] The relevant parameters of each lens in the projection lens 300 in Example 3 are shown in Table 3-1.

[0145] Table 3-1

[0146]

[0147] The surface parameters of the aspherical lens of the projection lens 300 in Example 3 are shown in Table 3-2.

[0148] Table 3-2

[0149]

[0150] from Fig.16 It can be seen that the F-Tan (Theta) distortion of the projection lens is controlled within 0~1%, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the expanded image.

[0151] from Fig.17 It can be seen that the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within -1μm~4μm, indicating that the projection lens can extremely well correct the chromatic aberration of the edge field of view and the secondary spectrum of the entire image plane.

[0152] from Fig.18 It can be seen that at the maximum half field of view angle, the relative illumination value of the projection lens is still greater than 70%, indicating that the projection lens has very good relative illumination.

[0153] from Fig.19 It can be seen that the MTF value of this embodiment is above 0.6 in the whole field of view when the working temperature is 20°C. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability at normal temperature.

[0154] from Fig. 20 It can be seen that the MTF value of this embodiment is above 0.6 in the whole field of view when the working temperature is -40°C. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability under low temperature conditions.

[0155] from Fig.21 It can be seen that the MTF value of this embodiment is above 0.58 in the whole field of view when the working temperature is 85°C. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability under higher temperature conditions.

[0156] Example 4

[0157] See also Fig. 22, which is a schematic diagram of the structure of a projection lens 400 provided in Example 4 of the present invention. Compared with Example 1, the main differences of this embodiment are: the image source side surface S4 of the second lens L2 is a convex surface; and the optical parameters such as the curvature radius and lens thickness of each lens surface are different.

[0158] The relevant parameters of each lens in the projection lens 400 in Example 4 are shown in Table 4-1.

[0159] Table 4-1

[0160]

[0161] The surface parameters of the aspheric lens of the projection lens 400 in Example 4 are shown in Table 4-2.

[0162] Table 4-2

[0163]

[0164] from Fig.23 It can be seen that the F-Tan (Theta) distortion of the projection lens is controlled within 0~2%, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the expanded image.

[0165] from Fig.24 It can be seen that the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within -2μm~4μm, which means that the projection lens can extremely well correct the chromatic aberration of the edge field of view and the secondary spectrum of the entire image plane.

[0166] from Fig.25 It can be seen that at the maximum half field of view angle, the relative illumination value of the projection lens is still greater than 70%, indicating that the projection lens has very good relative illumination.

[0167] from Fig.26 It can be seen that the MTF value of this embodiment is above 0.5 in the whole field of view when the working temperature is 20°C. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability at normal temperature.

[0168] from Fig. 27 It can be seen that the MTF value of this embodiment is above 0.5 in the whole field of view when the working temperature is -40°C. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability under low temperature conditions.

[0169] from Fig.28It can be seen that the MTF value of this embodiment when the working temperature is 85°C is above 0.5 in the whole field of view. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution under higher temperature conditions.

[0170] Example 5

[0171] See also Fig.29 , shown is a schematic diagram of the structure of a projection lens 500 provided in Example 5 of the present invention. Compared with Example 1, the main differences of this embodiment are: the projection side surface S1 of the first lens L1 is a concave surface, the image source side surface S2 of the first lens L1 is a convex surface; the image source side surface S4 of the second lens L2 is a convex surface; the optical parameters such as the curvature radius of each lens surface and the lens thickness are different.

[0172] The relevant parameters of each lens in the projection lens 500 in Example 5 are shown in Table 5-1.

[0173] Table 5-1

[0174]

[0175] The surface parameters of the aspheric lens of the projection lens 500 in Example 5 are shown in Table 5-2.

[0176] Table 5-2

[0177]

[0178] from Fig.30 It can be seen that the F-Tan (Theta) distortion of the projection lens is controlled within -9%~0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the expanded image.

[0179] from Fig.31 It can be seen that the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within 0~4μm, which means that the projection lens can extremely well correct the chromatic aberration of the edge field of view and the secondary spectrum of the entire image plane.

[0180] from Fig.32 It can be seen that at the maximum half field of view angle, the relative illumination value of the projection lens is still greater than 75%, indicating that the projection lens has very good relative illumination.

[0181] from Fig.33 It can be seen that the MTF value of this embodiment is above 0.55 in the whole field of view when the working temperature is 20°C. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability at normal temperature.

[0182] from Fig.34 It can be seen that the MTF value of this embodiment is above 0.55 in the whole field of view when the working temperature is -40°C. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability under low temperature conditions.

[0183] from Fig.35 It can be seen that the MTF value of this embodiment is above 0.55 in the whole field of view when the working temperature is 85°C. In the range of 0 to 60lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution under higher temperature conditions.

[0184] Please refer to Table 6, which shows the optical characteristics corresponding to the above embodiments, including the effective focal length f of the projection lens, the total optical length TTL, the aperture value Fno, the real image height IH corresponding to the maximum field of view angle, the chief ray incident angle CRA at the maximum image height, and the maximum field of view angle FOV, as well as the numerical values ​​corresponding to each conditional expression in each embodiment.

[0185] Table 6

[0186]

[0187] In summary of the above embodiments, the projection lens provided by the present invention can achieve telephoto characteristics through the reasonable configuration of each lens surface shape and the reasonable matching of optical focal length, which can effectively limit the length of the lens, and is conducive to miniaturization of the projection lens and easy assembly. It has a small CRA and good uniformity; at the same time, the back focal length will not interfere with the projection system. At the same time, the high and low temperature performance is stable, and the performance is stable within the temperature range of -40℃-85℃, and the image quality is maintained at a high level. The imaging quality of the projection lens is improved, the aberration is reduced, and it has small distortion, so that the picture is not deformed, and the imaging quality of the projection lens is improved.

[0188] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0189] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A projection lens, comprising six lenses, characterized in that: In order from the projection plane to the image source plane along the optical axis, it includes: A first lens with negative optical power; A second lens with positive optical power, the projection side surface of which is convex; A third lens with negative optical power, the projection side surface of which is convex and the image source side surface of which is concave; A fourth lens with negative optical power, both the projection side surface and the image source side surface of which are concave; A fifth lens with positive optical power, both the projection side surface and the image source side surface of which are convex; A sixth lens with positive optical power, the projection side surface of which is concave and the image source side surface of which is convex; Wherein, the focal length f3 of the third lens and the focal length f6 of the sixth lens satisfy: -2.2 < f3 / f6 < -1.5; the curvature radius R5 of the projection side surface of the third lens and the curvature radius R11 of the projection side surface of the sixth lens satisfy: -8.7 < (R5 - R11) / (R5 + R11) < -3.9; the effective focal length f of the projection lens and the combined focal length f456 of the fourth lens, the fifth lens and the sixth lens satisfy: 0.6 < f456 / f < 0.

8.

2. The projection lens according to claim 1, characterized in that: The effective focal length f of the projection lens and the optical total length TTL of the projection lens satisfy: 4.2 < TTL / f < 4.9; the optical total length TTL of the projection lens and the true image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 5.1 < TTL / IH < 5.

7.

3. The projection lens according to claim 1, characterized in that: The maximum field of view angle FOV of the projection lens and the f-number Fno of the projection lens satisfy: 16.9° < FOV / Fno < 17.4°; the true image height IH corresponding to the maximum field of view angle of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 2.3 < IH / EPD < 2.

6.

4. The projection lens according to claim 1, characterized in that: The clear aperture semi-diameter d1 of the projection side surface of the first lens, the true image height IH corresponding to the maximum field of view angle of the projection lens and the maximum field of view angle FOV of the projection lens satisfy: 4.4 < d1 / (IH / 2) / tan(FOV / 2) < 5; the clear aperture semi-diameter d1 of the projection side surface of the first lens and the clear aperture semi-diameter d12 of the image source side surface of the sixth lens satisfy: 1.5 < d1 / d12 < 1.

7.

5. The projection lens according to claim 1, wherein: The effective focal length f of the projection lens and the focal length f1 of the first lens satisfy: -6.1 < f1 / f < -3.5; the curvature radius R1 of the projection side surface of the first lens and the curvature radius R2 of the image source side surface of the first lens satisfy: 0.3 < R1 / R2 < 2.

6.

6. The projection lens according to claim 1, wherein: The focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: -2.3 < f3 / f < -1.6; the curvature radius R5 of the projection side surface of the third lens and the effective focal length f of the projection lens satisfy: 0.35 < R5 / f < 0.55; the curvature radius R6 of the image source side surface of the third lens and the effective focal length f of the projection lens satisfy: 0.2 < R6 / f < 0.3; the curvature radius R5 of the projection side surface of the third lens and the curvature radius R6 of the image source side surface of the third lens satisfy: 0.25 < (R5 - R6) / (R5 + R6) < 0.

35.

7. The projection lens according to claim 1, wherein: The focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: -0.9 < f4 / f < -0.7; the effective focal length f of the projection lens and the curvature radius R7 of the projection-side surface of the fourth lens satisfy: -2.3 < R7 / f < -1.1; the effective focal length f of the projection lens and the curvature radius R8 of the image-source-side surface of the fourth lens satisfy: 1 < R8 / f < 1.

7.

8. The projection lens according to claim 1, wherein: The focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 0.6 < f5 / f < 0.8; the effective focal length f of the projection lens and the combined focal length f456 of the fourth lens, the fifth lens and the sixth lens satisfy: 0.67 < f456 / f < 0.78; the focal length f3 of the third lens and the focal length f6 of the sixth lens satisfy: -2.12 < f3 / f6 < -1.51; the curvature radius R5 of the projection-side surface of the third lens and the curvature radius R11 of the projection-side surface of the sixth lens satisfy: -8.7 < (R5 - R11) / (R5 + R11) < -3.

99.

9. The projection lens according to claim 1, wherein: The focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 0.9 < f6 / f < 1.2; the curvature radius R11 of the projection-side surface of the sixth lens and the effective focal length f of the projection lens satisfy: -68 < R11 / f < -33; the curvature radius R12 of the image-source-side surface of the sixth lens and the effective focal length f of the projection lens satisfy: -0.7 < R12 / f < -0.

5.

10. The projection lens according to claim 1, wherein: The curvature radius R11 of the projection-side surface of the sixth lens and the curvature radius R12 of the image-source-side surface of the sixth lens satisfy: 56 < R11 / R12 < 104; the curvature radius R7 of the projection-side surface of the fourth lens and the curvature radius R8 of the image-source-side surface of the fourth lens satisfy: -0.2 < (R7 + R8) / (R7 - R8) < 0.

4.

11. The projection lens according to claim 1, wherein: The semi-aperture d11 of the projection-side surface of the sixth lens and the sagittal height Sag11 of the projection-side surface of the sixth lens satisfy: -0.1 < Sag11 / d11 < 0; the semi-aperture d12 of the image-source-side surface of the sixth lens and the sagittal height Sag12 of the image-source-side surface of the sixth lens satisfy: -0.6 < Sag12 / d12 < -0.45; a prism is provided between the sixth lens and the image source plane.

Images