Projection lens

Abstract

The present invention provides a projection lens, which has seven lenses in total, and includes the following in order from the projection surface to the image source surface along the optical axis: a first lens with negative optical focal length, whose image source side surface is concave; a second lens with positive optical focal length, whose projection side surface is concave and whose image source side surface is convex; a third lens with negative optical focal length, whose projection side surface is convex and whose image source side surface is concave; a fourth lens with positive optical focal length, whose projection side surface is convex and whose image source side surface is concave; a fifth lens with negative optical focal length, whose image source side surface is concave; a sixth lens with positive optical focal length, whose projection side surface and image source side surface are both convex; and a seventh lens with positive optical focal length, whose image source side surface is convex. 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 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 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 seven lenses in total, and includes the following lenses in order from the projection surface to the image source surface along the optical axis:

[0006] The first lens has a negative optical power and its image source side surface is concave;

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

[0010] a fifth lens element having negative optical power, whose image source side surface is concave;

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

[0013] Among them, 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 < (R3 - R4) / (R3 + R4) < 0.4; 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: -6 < (R7 + R8) / (R7 - R8) < -3.8.

[0014] 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)) < 1.01; 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: 3.1 < d1 / (IH / 2) / tan(FOV / 2) < 5.6.

[0015] Further preferably, the maximum field of view angle FOV of the projection lens and the f-number Fno of the projection lens satisfy: 15° < 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: 2.2 < IH / EPD < 2.6.

[0016] Further preferably, the effective focal length f of the projection lens and the true image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 0.75 < IH / f < 0.95; 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.

[0017] 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: 19 < 180°×TTL / IH / FOV < 24; the effective focal length f of the projection lens and the combined focal length f567 of the fifth lens, the sixth lens, and the seventh lens satisfy: 0.7 < f567 / f < 1.4.

[0018] Further preferably, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 3.7 < f2 / f < 5.5; the curvature radius R3 of the projection side surface of the second lens and the effective focal length f of the projection lens satisfy: -4.8 < R3 / f < -1.4; 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: -2.2 < R4 / f < -1.2.

[0019] Further preferably, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: 1.3 < f4 / f < 2; the effective focal length f of the projection lens and the curvature radius R7 of the projection-side surface of the fourth lens satisfy: 0.3 < R7 / f < 0.9; 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: 0.5 < R8 / f < 1.5.

[0020] Further preferably, the focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 0.4 < f6 / f < 1.1; the focal length f7 of the seventh lens and the effective focal length f of the projection lens satisfy: 1.2 < f7 / f < 2.

[0021] Further preferably, the focal length f1 of the first lens and the focal length f7 of the seventh lens satisfy: -2.7 < f1 / f7 < -0.9; the curvature radius R1 of the projection-side surface of the first lens and the curvature radius R13 of the projection-side surface of the seventh lens satisfy: 1 < R1 / R13 < 2.3.

[0022] Further preferably, the curvature radius R3 of the projection-side surface of the second lens and the curvature radius R14 of the image-source-side surface of the second lens satisfy: 1 < R3 / R4 < 2.3; 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: 0.5 < R7 / R8 < 0.8; a prism is provided between the seventh lens and the image source surface.

[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 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. Description of the Drawings

[0024] 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:

[0025] Figure 1 is a schematic structural diagram of the projection lens in Embodiment 1 of the present invention.

[0026] Figure 2 is a field curvature curve diagram of the projection lens in Embodiment 1 of the present invention.

[0027] Figure 3 is an F-Tan(Theta) distortion curve diagram of the projection lens in Embodiment 1 of the present invention.

[0028] Figure 4 is an axial aberration curve diagram of the projection lens in Embodiment 1 of the present invention.

[0029] Figure 5 : is the vertical axis chromatic aberration curve of the projection lens in Example 1 of the present invention.

[0030] Figure 6 is a relative illumination curve diagram of the projection lens in Example 1 of the present invention.

[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 20°C.

[0032] Figure 8 This is an MTF curve diagram of the projection lens in Example 1 of the present invention when the working temperature is -40°C.

[0033] Fig. 9 This is an MTF curve diagram of the projection lens in Example 1 of the present invention when the working temperature is 85°C.

[0034] Fig.10 Schematic diagram of the structure of the projection lens in Embodiment 2 of the present invention.

[0035] Fig.11 It is a field curvature curve diagram of the projection lens in Example 2 of the present invention.

[0036] Fig.12 FIG. 4 is a graph showing the F-Tan (Theta) distortion curve of the projection lens in Example 2 of the present invention.

[0037] Fig.13 Graph showing the axial aberration of the projection lens in Embodiment 2 of the present invention.

[0038] Fig.14 Graph showing the vertical axis chromatic aberration of the projection lens in Embodiment 2 of the present invention.

[0039] Fig.15 is a relative illumination curve diagram of the projection lens in Example 2 of the present invention.

[0040] Fig.16 This is an MTF curve diagram of the projection lens in Example 2 of the present invention when the working temperature is 20°C.

[0041] Fig.17 This is an MTF curve diagram of the projection lens in Example 2 of the present invention when the working temperature is -40°C.

[0042] Fig.18 This is an MTF curve diagram of the projection lens in Example 2 of the present invention when the working temperature is 85°C.

[0043] Fig.19 Schematic diagram of the structure of the projection lens in Embodiment 3 of the present invention.

[0044] Fig. 20 It is a field curvature curve diagram of the projection lens in Example 3 of the present invention.

[0045] Fig.21 FIG. 4 is a graph showing the F-Tan (Theta) distortion curve of the projection lens in Example 3 of the present invention.

[0046] Fig. 22 Graph showing the axial aberration of the projection lens in Embodiment 3 of the present invention.

[0047] Fig.23 : is the vertical axis chromatic aberration curve of the projection lens in Example 3 of the present invention.

[0048] Fig.24 This is a relative illumination curve diagram of the projection lens in Example 3 of the present invention.

[0049] Fig.25 This is an MTF curve diagram of the projection lens in Example 3 of the present invention when the working temperature is 20°C.

[0050] Fig.26 This is an MTF curve diagram of the projection lens in Example 3 of the present invention when the working temperature is -40°C.

[0051] Fig. 27 This is an MTF curve diagram of the projection lens in Example 3 of the present invention when the working temperature is 85°C.

[0052] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] The projection lens provided by the embodiment of the present invention comprises seven lenses in total, which are a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens in order from the projection plane to the image source plane along the optical axis.

[0061] In some embodiments, the first lens may have negative optical power, its projection side surface may be concave or convex, and its image source side surface is concave. The second lens may have positive optical power, its projection side surface is concave, and its image source side surface is convex. The third lens may have negative optical power, its projection side surface is convex, and its image source side surface is concave. The fourth lens may have positive optical power, its projection side surface is convex, and its image source side surface is concave. The fifth lens may have negative optical power, its projection side surface may be concave or convex, and its image source side surface is concave. The sixth lens may have positive optical power, and both its projection side surface and image source side surface are convex. The seventh lens may have positive optical power, its projection side surface may be concave or convex, and its image source side surface is convex.

[0062] In some embodiments, the projection lens further includes a prism, and the prism is disposed between the seventh 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 arrangement of the right-angle prism can change the direction of the light path, bend the light path, make the direction of the incident light perpendicular to the arrangement direction of the multiple lenses, and reduce the overall thickness of the optical system.

[0063] In some embodiments, the projection lens may further include an aperture, and the aperture may be located between the fourth lens and the fifth lens. It is understood that the aperture is used to limit the amount of incoming light to change the brightness of the image. When the aperture is located between the fourth lens and the fifth lens, it is convenient to correct the aperture aberration.

[0064] 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.

[0065] In some embodiments, the fifth lens and the sixth lens can be glued 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 difficulty of the processing technology of the projection lens and improving the assembly yield of the projection lens.

[0066] 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 < (R3 - R4) / (R3 + R4) < 0.4. Meeting the above range, by reasonably setting the surface shape of the second lens, it is beneficial for the smooth transition of light, and at the same time corrects various aberrations of the projection lens, improving the imaging quality of the projection lens. More specifically, 0.04 < (R3 - R4) / (R3 + R4) < 0.4.

[0067] 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: -6 < (R7 + R8) / (R7 - R8) < -3.8. Meeting the above range, it 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-end lens of the projection lens; and it is beneficial for the smooth trend of light, improving the imaging quality of the projection lens. More specifically, -5.89 < (R7 + R8) / (R7 - R8) < -3.89.

[0068] 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)) < 1.01. 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.

[0069] 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: 3.1 < d1 / (IH / 2) / tan(FOV / 2) < 5.6. Meeting the above range, it is possible to 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 for the miniaturization of the projection lens. More specifically, 3.14 < d1 / (IH / 2) / tan(FOV / 2) < 5.58.

[0070] In some embodiments, the maximum field of view angle FOV of the projection lens and the f-number Fno of the projection lens satisfy: 15° < FOV / Fno < 18°. Meeting the above range, it defines that the projection lens has a suitable field of view angle and f-number, and can collect light at a large angle and obtain good imaging quality. More specifically, 15.5° < FOV / Fno < 17.42°.

[0071] 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: 2.2 < IH / EPD < 2.6. Meeting the above range can increase the width of the light beam incident on the projection lens, improve the relative illuminance, and avoid vignetting. More specifically, 2.22 < IH / EPD < 2.54.

[0072] 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 of the projection lens satisfy: 0.75 < IH / f < 0.95. Meeting the above range helps to achieve a large image plane and improve the imaging quality of the projection lens. More specifically, 0.79 < IH / f < 0.91.

[0073] 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 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 can avoid interference between the lens and other components and reduce the assembly process difficulty of the lens module. More specifically, 1.23 < BFL / f < 1.48.

[0074] 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 FOV of the projection lens satisfy: 19 < 180°×TTL / IH / FOV < 24. Meeting the above range is beneficial to balance the relationship among the total length, image height, and field of view angle of the projection lens. More specifically, 19.71 < 180°×TTL / IH / FOV < 23.69.

[0075] In some embodiments, the effective focal length f of the projection lens and the combined focal length f567 of the fifth lens, the sixth lens, and the seventh lens satisfy: 0.7 < f567 / f < 1.4. Meeting the above range is beneficial to balance the aberrations generated by the lens group in front of the aperture and improve the imaging quality of the projection lens. More specifically, 0.77 < f567 / f < 1.34.

[0076] In some embodiments, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 3.7 < f2 / f < 5.5; the radius of curvature R3 of the projection-side surface of the second lens and the effective focal length f of the projection lens satisfy: -4.8 < R3 / f < -1.4; the radius of curvature R4 of the image-source side surface of the second lens and the effective focal length f of the projection lens satisfy: -2.2 < R4 / f < -1.2. Satisfying the above ranges can enable the second lens to have an appropriate positive optical power and surface shape, effectively balance lens aberrations, and improve imaging quality. More specifically, 3.79 < f2 / f < 5.48; -4.76 < R3 / f < -1.41; -2.11 < R4 / f < -1.28.

[0077] In some embodiments, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: 1.3 < f4 / f < 2; 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: 0.3 < R7 / f < 0.9; 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: 0.5 < R8 / f < 1.5. Satisfying the above ranges can enable the fourth lens to have an appropriate positive optical power and surface shape, effectively balance lens aberrations, and improve imaging quality. More specifically, 1.32 < f4 / f < 1.92; 0.36 < R7 / f < 0.86; 0.52 < R8 / f < 1.45.

[0078] In some embodiments, the focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 0.4 < f6 / f < 1.1; the focal length f7 of the seventh lens and the effective focal length f of the projection lens satisfy: 1.2 < f7 / f < 2. Satisfying the above ranges can enable the sixth lens and the seventh lens to have appropriate positive optical powers, 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, 0.48 < f6 / f < 1.07; 1.2 < f7 / f < 1.99.

[0079] In some embodiments, the focal length f1 of the first lens and the focal length f7 of the seventh lens satisfy: -2.7 < f1 / f7 < -0.9; the radius of curvature R1 of the projection-side surface of the first lens and the radius of curvature R13 of the projection-side surface of the seventh lens satisfy: 1 < R1 / R13 < 2.3. Satisfying the above conditions, by reasonably setting the focal length relationship between the first and last lenses in the lens, while ensuring that as much light as possible enters the system, the area of light entering the imaging surface is increased, which is beneficial to achieving large image surface imaging of the lens, while increasing the light input and improving the relative illumination of the system. More specifically, -2.68 < f1 / f7 < -0.92; 1.01 < R1 / R13 < 2.27.

[0080] 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: 1 < R3 / R4 < 2.3; 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: 0.5 < R7 / R8 < 0.8. Satisfying the above ranges can make the second lens and the fourth lens have a meniscus shape, while better correcting aberration and ensuring the low sensitivity of the system, and improving the resolution. More specifically, 1.09 < R3 / R4 < 2.27; 0.58 < R7 / R8 < 0.72.

[0081] In some embodiments, the effective focal length f of the projection lens and the overall optical length TTL of the projection lens satisfy: 4.5 < TTL / f < 5.5. Satisfying the above range can achieve the telephoto characteristics of the lens, effectively limit the length of the lens, and is beneficial to the miniaturization of the projection lens. More specifically, 4.54 < TTL / f < 5.46.

[0082] In some embodiments, 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: 5.3 < TTL / IH < 6.2. Satisfying the above range is beneficial to achieving the balance between the volume of the projection lens and the large image plane. More specifically, 5.33 < TTL / IH < 6.12.

[0083] In some embodiments, the overall 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. Satisfying the above range can effectively compress the overall length of the projection lens, and is beneficial to the structural design and production process of the projection lens. More specifically, 0.3 < ∑CT / TTL < 0.45.

[0084] In some embodiments, the sum ∑CT of the central thicknesses of the first lens to the seventh lens along the optical axis and the effective focal length f of the projection lens satisfy: 1.3 < ∑CT / f < 2.4. 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, 1.39 < ∑CT / f < 2.38.

[0085] In some embodiments, the effective focal length f of the projection lens and the focal length f1 of the first lens satisfy: -3.3 < f1 / f < -1.8. Satisfying the above range can make the first lens have an appropriate negative optical power, can slow down the degree of deflection of the incident light, help more light enter the optical system within a larger range, and is beneficial to expanding the field of view angle of the lens. More specifically, -3.25 < f1 / f < -1.82.

[0086] In some embodiments, the focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: -12.5 < f3 / f < -1.8. Meeting the above range, by reasonably setting the focal length 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, -12.43 < f3 / f < -1.85.

[0087] In some embodiments, the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: -1.2 < f5 / f < -0.5. Meeting the above range can endow the fifth lens with an appropriate negative optical power, which 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, -1.11 < f5 / f < -0.51.

[0088] In some embodiments, the radius of curvature R3 of the projection-side surface of the second lens, the radius of curvature R4 of the image-source-side surface of the second lens, and the central thickness CT2 of the second lens satisfy: 0.6 < (R3 + CT2) / R4 < 2.2. Meeting the above range can effectively reduce the optical path difference between the center and the periphery of the lens, which is beneficial to correcting the distortion of the projection lens. More specifically, 0.61 < (R3 + CT2) / R4 < 2.18.

[0089] In some embodiments, the radius of curvature R7 of the projection-side surface of the fourth lens, the radius of curvature R8 of the image-source-side surface of the fourth lens, and the central thickness CT4 of the fourth lens satisfy: 0.7 < (R7 + CT4) / R8 < 1. Meeting the above range can effectively reduce the optical path difference between the center and the periphery of the lens, which is beneficial to correcting the distortion of the projection lens. More specifically, 0.78 < (R7 + CT4) / R8 < 0.95.

[0090] In some embodiments, the semi-aperture d3 of the projection-side surface of the second lens and the sagittal height Sag3 of the projection-side surface of the second lens satisfy: -0.25 < Sag3 / d3 < -0.05; the semi-aperture d8 of the image-source-side surface of the fourth lens and the sagittal height Sag8 of the image-source-side surface of the fourth lens satisfy: 0.05 < Sag8 / d8 < 0.2. Meeting the above range helps to control the trend of the light rays in the marginal field of view and highlight the detailed information of the central field of view of the projection lens. More specifically, -0.21 < Sag3 / d3 < -0.07; 0.08 < Sag8 / d8 < 0.19.

[0091] In some embodiments, the projection lens satisfies the conditional formula: 13 mm < f < 16.5 mm, 4.7 mm < EPD < 5.8 mm, 70 mm < TTL < 74 mm, 2.7 < Fno < 2.9, 11 mm < IH < 14 mm, 43° < FOV < 49°, 19 mm < BFL < 20 mm, 0.5° < CRA < 1.4°; 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, 13.4 mm < f < 16.05 mm, 4.78 mm < EPD < 5.74 mm, 70.11 mm < TTL < 73.14 mm, 2.79 < Fno < 2.81, 11.97 mm < IH < 13.14 mm, 43.43° < FOV < 48.75°, 19.64 mm < BFL < 19.87 mm, 0.57° < CRA < 1.32°.

[0092] 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 seven 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.

[0093] The present invention will be further described below with multiple embodiments. In each embodiment, the thickness, curvature radius, and material selection of each lens in the projection lens are partially different. For specific differences, refer to the parameter tables of each embodiment. The following embodiments are only the preferred embodiments of the present invention, but the embodiments of the present invention are not limited only by the following embodiments. Any other changes, substitutions, combinations, or simplifications made without departing 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.

[0094] Embodiment 1

[0095] Please refer to 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, a fourth lens L4, an aperture ST, a fifth lens L5, a sixth lens L6, a seventh lens L7, a prism G1 and a protective glass G2.

[0096] The first lens L1 has negative optical power, its projection side surface S1 is convex, and its image source side surface S2 is concave;

[0097] The second lens L2 has positive refractive power, its projection side surface S3 is concave, and its image source side surface S4 is convex;

[0098] The third lens L3 has negative refractive power, its projection side surface S5 is convex, and its image source side surface S6 is concave;

[0099] The fourth lens L4 has positive refractive power, a projection-side surface S7 thereof is a convex surface, and an image-source-side surface S8 thereof is a concave surface;

[0100] The fifth lens L5 has negative refractive power, and its projection side surface S9 and image source side surface S10 are both concave surfaces;

[0101] The sixth lens L6 has positive refractive power, and its projection-side surface S10 and image-source-side surface S11 are both convex surfaces;

[0102] The fifth lens L5 and the sixth lens L6 form a cemented lens group with positive power, that is, the cemented surface between the image source side surface of the fifth lens L5 and the projection side surface of the sixth lens L6 is S10;

[0103] The seventh lens L7 has positive refractive power, and its projection side surface S12 and image source side surface S13 are both convex surfaces;

[0104] The prism G1 may be a right angle prism;

[0105] The projection side surface S14 and the image source side surface S15 of the protection glass G2 are both planes;

[0106] The image source surface S16 is a plane.

[0107] The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6 and the seventh lens L7 are all glass spherical lenses.

[0108] The relevant parameters of each lens in the projection lens 100 in Example 1 are shown in Table 1-1.

[0109] Table 1-1

[0110]

[0111] 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, with the horizontal axis indicating the offset (unit: mm) and the vertical axis indicating 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 ±0.08 mm, indicating that the projection lens can well correct the field curvature.

[0112] 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 -1.2%~0, the image compression in the edge angle area is relatively gentle, and the clarity of the expanded image is effectively improved.

[0113] 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~0.08mm, indicating that the projection lens can correct the axial aberration well.

[0114] Figure 5 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 0~5 μm, 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 surface.

[0115] 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 90% at the maximum half viewing angle, indicating that the projection lens has good relative illumination.

[0116] Figure 7The 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 0.5 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.

[0117] Figure 8 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 0.5 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.

[0118] Fig. 9 The MTF (Modulation Transfer Function) curve of Example 1 at an operating temperature of 85°C is shown, which indicates the imaging modulation of the lens at different spatial frequencies under each field of view, the horizontal axis indicates the spatial frequency (unit: lp / mm), and the vertical axis indicates the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.5 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.

[0119] Example 2

[0120] See also Fig.10 , 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 projection side surface S1 of the first lens L1 is a concave surface; the projection side surface S12 of the seventh lens L7 is a concave surface; and the optical parameters such as the curvature radius of each lens surface and the lens thickness are different.

[0121] The relevant parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2-1.

[0122] Table 2-1

[0123]

[0124] from Fig.11It can be seen that the field curvature of the meridian image plane and the sagittal image plane is controlled within -0.04mm~0.1mm, indicating that the projection lens can correct the field curvature well.

[0125] from Fig.12 It can be seen that the F-Tan (Theta) distortion of the projection lens is controlled within -1.2%~0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the expanded image.

[0126] from Fig.13 It can be seen that the offset of the axial aberration is controlled within -0.02mm~0.1mm, which means that the projection lens can correct the axial aberration well.

[0127] from Fig.14 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.

[0128] from Fig.15 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.

[0129] from Fig.16 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.

[0130] from Fig.17 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.

[0131] from Fig.18 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.

[0132] Example 3

[0133] See also Fig.19, 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, the main differences of this embodiment are: the projection side surface S9 of the fifth lens L5 is a convex surface; the optical parameters such as the curvature radius of each lens surface and the lens thickness are different.

[0134] The relevant parameters of each lens in the projection lens 300 in Example 3 are shown in Table 3-1.

[0135] Table 3-1

[0136]

[0137] from Fig. 20 It can be seen that the field curvature of the meridional image plane and the sagittal image plane is controlled within -0.06mm~0.08mm, indicating that the projection lens can correct the field curvature well.

[0138] from Fig.21 It can be seen that the F-Tan (Theta) distortion of the projection lens is controlled within -1.2%~0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the expanded image.

[0139] from Fig. 22 It can be seen that the offset of the axial aberration is controlled within -0.02mm~0.07mm, which means that the projection lens can correct the axial aberration well.

[0140] from Fig.23 It can be seen that the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within -2μm~5μm, 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.

[0141] from Fig.24 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 85%, indicating that the projection lens has very good relative illumination.

[0142] from Fig.25 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 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.

[0143] from Fig.26 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.

[0144] from Fig. 27 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.

[0145] 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.

[0146] Table 4

[0147]

[0148] 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.

[0149] 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.

[0150] 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 seven lenses, characterized in that: From the projection plane to the image source plane along the optical axis, it successively includes: A first lens with negative optical power, whose image source side surface is concave; A second lens with positive optical power, whose projection side surface is concave and whose image source side surface is convex; A third lens with negative optical power, whose projection side surface is convex and whose image source side surface is concave; A fourth lens with positive optical power, whose projection side surface is convex and whose image source side surface is concave; A fifth lens with negative optical power, whose image source side surface is concave; A sixth lens with positive optical power, whose projection side surface and image source side surface are both convex; A seventh lens with positive optical power, whose image source side surface is convex; Among them, 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 < (R3 - R4) / (R3 + R4) < 0.4; 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: -6 < (R7 + R8) / (R7 - R8) < -3.8; the effective focal length f of the projection lens and the combined focal length f567 of the fifth lens, the sixth lens and the seventh lens satisfy: 0.7 < f567 / f < 1.

4.

2. The projection lens according to claim 1, characterized in that: 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)) < 1.01; 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: 3.1 < d1 / (IH / 2) / tan(FOV / 2) < 5.

6.

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: 15° < 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: 2.2 < IH / EPD < 2.

6.

4. The projection lens according to claim 1, characterized in that: The effective focal length f of the projection lens and the true image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 0.75 < IH / f < 0.95; 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.

5. The projection lens according to claim 1, wherein: 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: 19 < 180°×TTL / IH / FOV < 24; the effective focal length f of the projection lens and the combined focal length f567 of the fifth lens, the sixth lens and the seventh lens satisfy: 0.77 < f567 / f < 1.

34.

6. The projection lens according to claim 1, wherein: The focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 3.7 < f2 / f < 5.5; the radius of curvature R3 of the projection-side surface of the second lens and the effective focal length f of the projection lens satisfy: -4.8 < R3 / f < -1.4; the radius of curvature R4 of the image-source-side surface of the second lens and the effective focal length f of the projection lens satisfy: -2.2 < R4 / f < -1.

2.

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: 1.3 < f4 / f < 2; 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: 0.3 < R7 / f < 0.9; 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: 0.5 < R8 / f < 1.

5.

8. 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: 0.4 < f6 / f < 1.1; the focal length f7 of the seventh lens and the effective focal length f of the projection lens satisfy: 1.2 < f7 / f < 2.

9. The projection lens according to claim 1, wherein: The focal length f1 of the first lens and the focal length f7 of the seventh lens satisfy: -2.7 < f1 / f7 < -0.9; the radius of curvature R1 of the projection-side surface of the first lens and the radius of curvature R13 of the projection-side surface of the seventh lens satisfy: 1 < R1 / R13 < 2.

3.

10. The projection lens according to claim 1, wherein: 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: 1 < R3 / R4 < 2.3; 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: 0.5 < R7 / R8 < 0.8; a prism is provided between the seventh lens and the image source surface.

Images