Projection lens

Abstract

The present invention provides a projection lens, which has a total of six lenses, and includes, along the optical axis from the projection surface to the image source surface, in sequence: a first lens with negative optical power, whose projection side surface is convex, and whose image source side surface is concave; a second lens with positive optical power, whose projection side surface is convex, and whose image source side surface is concave; a third lens with positive optical power, whose projection side surface is concave, and whose image source side surface is convex; a fourth lens with negative optical power, whose projection side surface is concave; a fifth lens with positive optical power, whose image source side surface is convex; a sixth lens with positive optical power, whose projection side surface and image source side surface are both convex; wherein a curvature radius R11 of the projection side surface of the sixth lens and a curvature radius R12 of the image source side surface of the sixth lens satisfy: -0.8<(R11+R12) / (R11-R12)<0.1. The projection lens provided by the present invention improves the projection quality of the projection lens through reasonable configuration of the surface shapes of each lens and reasonable matching of the optical focal length.

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 make it 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, whose projection side surface is convex and whose image source side surface is concave;

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

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

[0009] a fourth lens having negative optical power, whose projection side surface is concave;

[0010] a fifth lens element having positive refractive power, whose image source side surface is convex;

[0011] a sixth lens having positive refractive power, wherein both a projection side surface and an image source side surface thereof are convex surfaces;

[0012] Among them, 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: -0.8 < (R11 + R12) / (R11 - R12) < 0.1.

[0013] Further preferably, the effective focal length f of the projection 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: 0.99 < (IH / 2) / (f×Tan(FOV / 2)) < 1.03; 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: 3.2 < d1 / (IH / 2) / tan(FOV / 2) < 3.8.

[0014] Further preferably, the maximum field of view angle FOV of the projection lens and the aperture value Fno of the projection lens satisfy: 16° < FOV / Fno < 18°; 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: 2.4 < IH / EPD < 2.7.

[0015] Further preferably, the overall optical length TTL of the projection 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: 68 < 180°×TTL / IH / FOV < 81; the combined focal length f12 of the first lens and the second lens and the combined focal length f3456 of the third lens, the fourth lens, the fifth lens, and the sixth lens satisfy: 1.8 < f12 / f3456 < 3.9.

[0016] Further preferably, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 0.9 < f2 / f < 1.2; the curvature radius R3 of the projection side surface of the second lens and the effective focal length f of the projection lens satisfy: 0.7 < R3 / f < 1; the curvature radius R4 of the image source side surface of the second lens and the effective focal length f of the projection lens satisfy: 3.8 < R4 / f < 6.3.

[0017] Further preferably, the focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: 1.8 < f3 / f < 3; the focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 1.2 < f6 / f < 1.7.

[0018] Further preferably, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: -0.8 < f4 / f < -0.5; the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 1 < f5 / f < 1.4.

[0019] More preferably, 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: -3.8 < R5 / f < -0.6; 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: -1.7 < R6 / f < -0.6; 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 satisfy: 1.1 < R5 / R6 < 2.4.

[0020] More preferably, 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: 1 < R11 / f < 1.4; 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: -6.5 < R12 / f < -1.2; 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 satisfy: -1.1 < R11 / R12 < -0.1.

[0021] More preferably, the radius of curvature R3 of the projection side surface of the second lens and the radius of curvature R4 of the image source side surface of the second lens satisfy: -0.9 < (R3 - R4) / (R3 + R4) < -0.6; 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 < (R5 - R6) / (R5 + R6) < 0.5; a prism is provided between the sixth lens and the image source surface.

[0022] 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 through the reasonable configuration of each lens surface type and the reasonable matching of the optical power, so that the lens has one or more advantages such as small distortion, small CRA, large image surface, and high imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein:

[0024] Figure 1 It is a schematic structural diagram of the projection lens in Embodiment 1 of the present invention.

[0025] Figure 2 It is a field curvature curve diagram of the projection lens in Embodiment 1 of the present invention.

[0026] Figure 3 It is an F-Tan(Theta) distortion curve diagram of the projection lens in Embodiment 1 of the present invention.

[0027] Figure 4 It is an axial aberration curve diagram of the projection lens in Embodiment 1 of the present invention.

[0028] Figure 5 : is the vertical axis chromatic aberration curve of the projection lens in Example 1 of the present invention.

[0029] Figure 6 is a relative illumination curve diagram of the projection lens in Example 1 of the present invention.

[0030] Figure 7 This is an MTF curve diagram of the projection lens in Example 1 of the present invention.

[0031] Figure 8 Schematic diagram of the structure of the projection lens in Embodiment 2 of the present invention.

[0032] Fig. 9 It is a field curvature curve diagram of the projection lens in Example 2 of the present invention.

[0033] Fig.10 FIG. 4 is a graph showing the F-Tan (Theta) distortion curve of the projection lens in Example 2 of the present invention.

[0034] Fig.11 Graph showing the axial aberration of the projection lens in Embodiment 2 of the present invention.

[0035] Fig.12 Graph showing the vertical axis chromatic aberration of the projection lens in Embodiment 2 of the present invention.

[0036] Fig.13 is a relative illumination curve diagram of the projection lens in Example 2 of the present invention.

[0037] Fig.14 This is an MTF curve diagram of the projection lens in Example 2 of the present invention.

[0038] Fig.15 Schematic diagram of the structure of the projection lens in Embodiment 3 of the present invention.

[0039] Fig.16 It is a field curvature curve diagram of the projection lens in Example 3 of the present invention.

[0040] Fig.17 FIG. 4 is a graph showing the F-Tan (Theta) distortion curve of the projection lens in Example 3 of the present invention.

[0041] Fig.18 Graph showing the axial aberration of the projection lens in Embodiment 3 of the present invention.

[0042] Fig.19 : is the vertical axis chromatic aberration curve of the projection lens in Example 3 of the present invention.

[0043] Fig. 20 This is a relative illumination curve diagram of the projection lens in Example 3 of the present invention.

[0044] Fig.21 This is an MTF curve diagram of the projection lens in Example 3 of the present invention.

[0045] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] In some embodiments, the first lens may have negative optical power, its projection side surface is convex, and its image source side surface is concave. The second lens may have positive optical power, its projection side surface is convex, and its image source side surface is concave. The third lens may have positive optical power, its projection side surface is concave, and its image source side surface is convex. The fourth lens may have negative optical power, its projection side surface is concave, and its image source side surface may be concave or convex. The fifth lens may have positive optical power, its projection side surface may be concave or convex, and its image source side surface is convex. The sixth lens may have positive optical power, and both its projection side surface and its image source side surface are convex.

[0055] 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.

[0056] In some embodiments, the projection lens may further include an aperture, and the aperture may be located between the second lens and the third lens. It is understood that the aperture is used to limit the amount of light entering to change the brightness of the image. When the aperture is located between the third lens and the fourth lens, it is convenient to correct the aperture aberration.

[0057] 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 protects the projection lens, prevents the photosensitive chip from being damaged, and can improve the impact resistance and scratch resistance of the projection lens, while having almost no effect on the imaging quality of the projection lens.

[0058] In some embodiments, the fourth lens and the fifth lens can be cemented to form a cemented lens group with negative optical power, which can effectively correct the chromatic aberration of the projection lens, reduce the decentration 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.

[0059] In some embodiments, 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: -0.8 < (R11 + R12) / (R11 - R12) < 0.1. Meeting the above range helps to control the light beam trend in the edge field of view to increase the image height and, at the same time, reduce the off-axis aberration of the projection lens. More specifically, -0.74 < (R11 + R12) / (R11 - R12) < 0.04.

[0060] In some embodiments, the effective focal length f of the projection 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: 0.99 < (IH / 2) / (f × Tan(FOV / 2)) < 1.03. Meeting the above range, the optical distortion of the projection lens is better controlled, the resolution of the projection lens is improved, a better projection effect can be obtained, and it is more suitable for human eyes to watch.

[0061] In some embodiments, 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: 3.2 < d1 / (IH / 2) / tan(FOV / 2) < 3.8. Meeting the above range, while satisfying the projection lens with a large field of view angle and a large image plane, the front aperture diameter is small, which is beneficial to the miniaturization of the projection lens. More specifically, 3.29 < d1 / (IH / 2) / tan(FOV / 2) < 3.77.

[0062] 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° < FOV / Fno < 18°. Meeting the above range, it is defined that the projection lens has a suitable field of view angle and f-number, and can collect light at large angles and obtain good imaging quality. More specifically, 16.42° < FOV / Fno < 17.97°.

[0063] 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: 2.4 < IH / EPD < 2.7. Meeting the above range, it is possible to increase the width of the light beam incident on the projection lens, improve the relative illumination, and avoid vignetting. More specifically, 2.4 < IH / EPD < 2.65.

[0064] In some embodiments, the total optical length TTL of the projection 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: 17 < 180°×TTL / IH / FOV < 21. Satisfying the above range is beneficial to balancing the relationship among the total length, image height, and field of view angle of the projection lens. More specifically, 17.09 < 180°×TTL / IH / FOV < 20.14.

[0065] In some embodiments, the combined focal length f12 of the first lens and the second lens and the combined focal length f3456 of the third lens, the fourth lens, the fifth lens, and the sixth lens satisfy: 1.8 < f12 / f3456 < 3.9. Satisfying the above range is beneficial to balancing the aberrations generated by the lens groups before and after the aperture and improving the imaging quality of the projection lens. More specifically, 1.87 < f12 / f3456 < 3.89.

[0066] In some embodiments, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 0.9 < f2 / f < 1.2; the curvature radius R3 of the projection side surface of the second lens and the effective focal length f of the projection lens satisfy: 0.7 < R3 / f < 1; the curvature radius R4 of the image source side surface of the second lens and the effective focal length f of the projection lens satisfy: 3.8 < R4 / f < 6.3. Satisfying the above range can enable the second lens to have an appropriate positive optical power, effectively balance the lens aberrations, and improve the imaging quality. More specifically, 0.99 < f2 / f < 1.17; 0.7 < R3 / f < 0.91; 3.8 < R4 / f < 6.27.

[0067] In some embodiments, the focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: 1.8 < f3 / f < 3. Satisfying the above range can enable the third lens to have an appropriate positive optical power, be beneficial to the smooth transition of light, and at the same time correct various aberrations of the projection lens, improving the imaging quality of the projection lens. More specifically, 1.82 < f3 / f < 2.97.

[0068] In some embodiments, the focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 1.2 < f6 / f < 1.7. Satisfying the above range can enable the sixth lens to have an appropriate positive optical power, be 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, 1.27 < f6 / f < 1.66.

[0069] In some embodiments, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: -0.8 < f4 / f < -0.5. Meeting the above range can endow the fourth lens with 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, -0.78 < f4 / f < -0.54.

[0070] In some embodiments, the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 1 < f5 / f < 1.4. Meeting the above range can endow the fifth lens with an appropriate positive optical power, which is beneficial to converging light while reducing the light deflection angle, enabling the light trend to transition smoothly, and improving the projection quality of the projection lens. More specifically, 1.05 < f5 / f < 1.4.

[0071] In some embodiments, 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: -3.8 < R5 / f < -0.6; 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: -1.7 < R6 / f < -0.6; 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 satisfy: 1.1 < R5 / R6 < 2.4. Meeting the above range can effectively correct spherical aberration, reduce chromatic aberration, and improve the projection quality of the projection lens. More specifically, -3.8 < R5 / f < -0.68; -1.62 < R6 / f < -0.61; 1.12 < R5 / R6 < 2.36.

[0072] In some embodiments, 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: 1 < R11 / f < 1.4; 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: -6.5 < R12 / f < -1.2; 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 satisfy: -1.1 < R11 / R12 < -0.1. Meeting the above range can endow the projection side surface and the image source side surface of the sixth lens with appropriate surface profiles, which is beneficial to correcting the spherical aberration of the projection lens and improving the imaging quality of the projection lens. More specifically, 1 < R11 / f < 1.32; -6.46 < R12 / f < -1.23; -1.07 < R11 / R12 < -0.15.

[0073] In some embodiments, the radius of curvature R3 of the projection-side surface of the second lens and the radius of curvature R4 of the image-source-side surface of the second lens satisfy: -0.9 < (R3 - R4) / (R3 + R4) < -0.6. Meeting the above range, by reasonably setting the surface shape of the second 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, -0.81 < (R3 - R4) / (R3 + R4) < -0.67.

[0074] In some embodiments, 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 < (R5 - R6) / (R5 + R6) < 0.5. Meeting the above range, by reasonably setting the 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, 0.05 < (R5 - R6) / (R5 + R6) < 0.41.

[0075] In some embodiments, the effective focal length f of the projection lens and the total optical length TTL of the projection lens satisfy: 4.4 < TTL / f < 4.6. Meeting the above range, the telephoto characteristics of the lens can be achieved, the length of the lens can be effectively limited, which is beneficial to the miniaturization of the projection lens. More specifically, 4.42 < TTL / f < 4.59.

[0076] 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: 4.7 < TTL / IH < 5.2. Meeting the above range, it is beneficial to achieve the balance between the volume of the projection lens and the large image plane. More specifically, 4.77 < TTL / IH < 5.15.

[0077] 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, 0.85 < IH / f < 0.95.

[0078] In some embodiments, the effective focal length f of the projection lens and the back focal length BFL of the projection lens satisfy: 1.2 < BFL / f < 1.5. 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, 1.29 < BFL / f < 1.47.

[0079] 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: 0.4 < ∑CT / TTL < 0.6. Satisfying 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, 0.42 < ∑CT / TTL < 0.51.

[0080] 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: 1.9 < ∑CT / f < 2.3. Satisfying 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, 1.94 < ∑CT / f < 2.28.

[0081] In some embodiments, the effective focal length f of the projection lens and the focal length f1 of the first lens satisfy: -1.6 < f1 / f < -1.3. Satisfying the above range can make the first lens have an appropriate negative optical power, can slow down the deflection degree of the incident light, helps light in a larger range to enter the optical system, and is beneficial to expanding the lens field of view angle. More specifically, -1.57 < f1 / f < -1.3.

[0082] In some embodiments, the clear aperture radius d5 of the projection side surface of the third lens and the sagittal height Sag5 of the clear aperture of the projection side surface of the third lens satisfy: -0.15 < Sag5 / d5 < 0; the clear aperture radius d12 of the image source side surface of the sixth lens and the sagittal height Sag12 of the clear aperture of the image source side surface of the sixth lens satisfy: -0.3 < Sag12 / d12 < 0.1. Satisfying the above range helps to control the trend of the marginal field light and highlights the detailed information of the central field of the projection lens. More specifically, -0.14 < Sag5 / d5 < -0.02; -0.25 < Sag12 / d12 < 0.04.

[0083] In some embodiments, the projection lens satisfies the conditional formula: 15 mm < f < 16.5 mm, 5.4 mm < EPD < 5.9 mm, 69 mm < TTL < 73 mm, 2.7 < Fno < 2.9, 13 mm < IH < 15 mm, 45° < FOV < 51°, 19 mm < BFL < 24 mm, 0.7° < CRA < 0.8°; 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, 15.22 mm < f < 16.25 mm, 5.43 mm < EPD < 5.81 mm, 69.69 mm < TTL < 72.01 mm, 2.79 < Fno < 2.81, 13.79 mm < IH < 14.68 mm, 45.59° < FOV < 50.3°, 19.86 mm < BFL < 23.41 mm, 0.72° < CRA < 0.79°.

[0084] 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 second lens, the third lens, the fourth lens, and the fifth lens in the projection lens provided by the present invention can adopt glass materials, and the first lens and the sixth lens can adopt plastic materials.

[0085] 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 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 first lens and the sixth lens can adopt aspherical lenses.

[0086] 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 equations:

[0087] ;

[0088] 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.

[0089] 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.

[0090] Example 1

[0091] See also Figure 1 , shown is a schematic diagram of the structure of the projection lens 100 provided in Example 1 of the present invention. The projection lens 100 includes, along the optical axis from the projection surface to the image source surface, a first lens L1, a second lens L2, an aperture ST, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a prism G1 and a protective glass G2.

[0092] The first lens L1 has negative optical power, its projection side surface S1 is convex, and its image source side surface S2 is concave;

[0093] The second lens L2 has positive refractive power, its projection side surface S3 is convex, and its image source side surface S4 is concave;

[0094] The third lens L3 has positive refractive power, its projection side surface S5 is concave, and its image source side surface S6 is convex;

[0095] The fourth lens L4 has negative refractive power, and its projection side surface S7 and image source side surface S8 are both concave surfaces;

[0096] The fifth lens L5 has positive refractive power, and its projection side surface S9 and image source side surface S10 are both convex surfaces;

[0097] The sixth lens L6 has positive refractive power, and its projection-side surface S11 and image-source-side surface S12 are both convex surfaces;

[0098] The prism G1 may be a right angle prism;

[0099] The projection side surface S13 and the image source side surface S14 of the protection glass G2 are both planes;

[0100] The image source surface S15 is a plane.

[0101] The second lens L2, the third lens L3, the fourth lens L4 and the fifth lens L5 are all glass spherical lenses; the first lens L1 and the sixth lens L6 are plastic aspherical lenses.

[0102] The relevant parameters of each lens in the projection lens 100 in Example 1 are shown in Table 1-1.

[0103] Table 1-1

[0104]

[0105] The surface parameters of the aspheric lens of the projection lens 100 in Example 1 are shown in Table 1-2.

[0106] Table 1-2

[0107]

[0108] Figure 2 The field curvature curve of Example 1 is shown, which indicates the degree of curvature of light of different wavelengths on the meridional image plane and the sagittal image plane, the horizontal axis indicates the offset (unit: mm), and the vertical axis indicates the half field angle (unit: °). It can be seen from the figure that the field curvature of the meridional image plane and the sagittal image plane is controlled within ±0.06mm, indicating that the projection lens can well correct the field curvature.

[0109] Figure 3 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 0~1.2%, the image compression in the edge angle area is relatively gentle, and the clarity of the expanded image is effectively improved.

[0110] Figure 4 The axial aberration curve of Example 1 is shown, which represents the aberration of each wavelength on the optical axis at the imaging plane, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial aberration is controlled within -0.02mm~0.04mm, indicating that the projection lens can correct the axial aberration well.

[0111] Figure 5The 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 0~6μm, 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.

[0112] Figure 6 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 80% at the maximum half viewing angle, indicating that the projection lens has good relative illumination.

[0113] Figure 7 The MTF (Modulation Transfer Function) curve of Example 1 is shown, which represents the imaging modulation degree 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 0.38 in the entire field of view, and in the range of 0 to 120 lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, with good imaging quality and good detail resolution.

[0114] Example 2

[0115] 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, the main differences between this embodiment and Example 1 are that: the image source side surface S8 of the fourth lens L4 is a convex surface; and the optical parameters such as the curvature radius and lens thickness of each lens surface are different.

[0116] The relevant parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2-1.

[0117] Table 2-1

[0118]

[0119] The surface parameters of the aspheric lens of the projection lens 200 in Example 2 are shown in Table 2-2.

[0120] Table 2-2

[0121]

[0122] from Fig. 9It can be seen that the field curvature of the meridional image plane and the sagittal image plane is controlled within ±0.08mm, indicating that the projection lens can correct the field curvature well.

[0123] from Fig.10 It can be seen that the F-Tan (Theta) distortion of the projection lens is controlled within 0~1.2%, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the expanded image.

[0124] from Fig.11 It can be seen that the offset of the axial aberration is controlled within ±0.04mm, which means that the projection lens can correct the axial aberration well.

[0125] from Fig.12 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.

[0126] from Fig.13 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 95%, indicating that the projection lens has very good relative illumination.

[0127] from Fig.14 It can be seen that the MTF value of this embodiment is above 0.3 in the whole field of view. In the range of 0 to 120 lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, with good imaging quality and good detail resolution.

[0128] Example 3

[0129] See also Fig.15 , shown is a schematic diagram of the structure of a projection lens 300 provided in Example 3 of the present invention. Compared with Example 1, this embodiment has the following main differences: the fourth lens L4 and the fifth lens L5 form a cemented lens group with negative optical power; the image source side surface of the fourth lens L4 is convex; the projection side surface of the fifth lens L5 is concave; 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 300 in Example 3 are shown in Table 3-1.

[0131] Table 3-1

[0132]

[0133] The surface parameters of the aspherical lens of the projection lens 300 in Example 3 are shown in Table 3-2.

[0134] Table 3-2

[0135]

[0136] from Fig.16 It can be seen that the field curvature of the meridional image plane and the sagittal image plane is controlled within ±0.07mm, indicating that the projection lens can correct the field curvature well.

[0137] from Fig.17 It can be seen that the F-Tan (Theta) distortion of the projection lens is controlled within 0~1.2%, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the expanded image.

[0138] from Fig.18 It can be seen that the offset of axial aberration is controlled within -0.02mm~0.05mm, which means that the projection lens can correct axial aberration well.

[0139] from Fig.19 It can be seen that the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within 0~6μm, 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.

[0140] from Fig. 20 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 95%, indicating that the projection lens has very good relative illumination.

[0141] from Fig.21 It can be seen that the MTF value of this embodiment is above 0.4 in the whole field of view. In the range of 0 to 120 lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, with good imaging quality and good detail resolution.

[0142] Please refer to Table 4, 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.

[0143] Table 4

[0144]

[0145] In summary of the above embodiments, the projection lens provided by the present invention can achieve telephoto characteristics through the reasonable configuration of the lens surface and the reasonable matching of the optical power, which can effectively limit the length of the lens, which is conducive to the 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. The imaging quality of the projection lens is improved, the aberration is reduced, the distortion is small, the picture is not deformed, and the imaging quality of the projection lens is improved.

[0146] 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.

[0147] 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: 依次包括沿光轴从投影面到像源面的: 第一透镜,具有负光焦度,其投影侧表面为凸面,其像源侧表面为凹面; 第二透镜,具有正光焦度,其投影侧表面为凸面,其像源侧表面为凹面; 第三透镜,具有正光焦度,其投影侧表面为凹面,其像源侧表面为凸面; 第四透镜,具有负光焦度,其投影侧表面为凹面; 第五透镜,具有正光焦度,其像源侧表面为凸面; 第六透镜,具有正光焦度,其投影侧表面和像源侧表面均为凸面; 其中,第六透镜的投影侧表面曲率半径R11与第六透镜的像源侧表面曲率半径R12满足:-0.8 < (R11 + R12) / (R11 - R12) < 0.1;第一透镜和第二透镜的组合焦距f12与第三透镜、第四透镜、第五透镜和第六透镜的组合焦距f3456满足:1.8 < f12 / f3456 < 3.9。 2. The projection lens according to claim 1, characterized in that: 投影镜头的有效焦距f、投影镜头的最大视场角所对应的真实像高IH与投影镜头的最大视场角FOV满足:0.99 < (IH / 2) / (f×Tan(FOV / 2)) < 1.03;第一透镜的投影侧表面通光半口径d1、投影镜头的最大视场角所对应的真实像高IH与投影镜头的最大视场角FOV满足:3.2 < d1 / (IH / 2) / tan(FOV / 2) < 3.8。 3. The projection lens according to claim 1, characterized in that: 投影镜头的最大视场角FOV与投影镜头的光圈值Fno满足:16° < FOV / Fno < 18°;投影镜头的最大视场角所对应的真实像高IH与投影镜头的入瞳直径EPD满足:2.4 < IH / EPD < 2.7。 4. The projection lens according to claim 1, characterized in that: 投影镜头的光学总长TTL、投影镜头的最大视场角所对应的真实像高IH与投影镜头的最大视场角FOV满足:17 < 180°×TTL / IH / FOV < 21;第一透镜和第二透镜的组合焦距f12与第三透镜、第四透镜、第五透镜和第六透镜的组合焦距f3456满足:1.87 < f12 / f3456 < 3.89;第六透镜的投影侧表面曲率半径R11与第六透镜的像源侧表面曲率半径R12满足:-0.74 < (R11 + R12) / (R11 - R12) < 0.04。 5. The projection lens according to claim 1, wherein: 第二透镜的焦距f2与投影镜头的有效焦距f满足:0.9 < f2 / f < 1.2;第二透镜的投影侧表面曲率半径R3与投影镜头的有效焦距f满足:0.7 < R3 / f < 1;第二透镜的像源侧表面曲率半径R4与投影镜头的有效焦距f满足:3.8 < R4 / f < 6.3。 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: 1.8 < f3 / f < 3; the focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 1.2 < f6 / f < 1.

7.

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: -0.8 < f4 / f < -0.5; the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 1 < f5 / f < 1.

4.

8. The projection lens according to claim 1, wherein: The curvature radius R5 of the projection side surface of the third lens and the effective focal length f of the projection lens satisfy: -3.8 < R5 / f < -0.6; 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: -1.7 < R6 / f < -0.6; the curvature radius R5 of the projection side surface of the third lens and the curvature radius R6 of the image source side surface satisfy: 1.1 < R5 / R6 < 2.

4.

9. The projection lens according to claim 1, wherein: The curvature radius R11 of the projection side surface of the sixth lens and the effective focal length f of the projection lens satisfy: 1 < R11 / f < 1.4; 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: -6.5 < R12 / f < -1.2; the curvature radius R11 of the projection side surface of the sixth lens and the curvature radius R12 of the image source side surface satisfy: -1.1 < R11 / R12 < -0.

1.

10. The projection lens according to claim 1, wherein: The curvature radius R3 of the projection side surface of the second lens and the curvature radius R4 of the image source side surface of the second lens satisfy: -0.9 < (R3 - R4) / (R3 + R4) < -0.6; 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 < (R5 - R6) / (R5 + R6) < 0.5; a prism is provided between the sixth lens and the image source surface.

Images