Projection lens

Abstract

The invention provides a projection lens, which comprises eight lenses in total, and sequentially comprises a first lens with positive focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with negative focal power, a fifth lens with positive focal power and a sixth lens with negative focal power from a projection surface to an image source surface along an optical axis, the surface of the projection side of the second lens is a concave surface, and the surface of the image source side of the second lens is a concave surface; the surface of the projection side of the third lens is a concave surface, and the surface of the image source side of the third lens is a convex surface; the surface of the projection side of the fourth lens is a concave surface, and the surface of the image source side of the fourth lens is a concave surface; the fifth lens has positive focal power; the sixth lens has negative focal power; the seventh lens has positive focal power; and the eighth lens has positive focal power. The projection lens provided by the invention has one or more advantages of small distortion, small CRA, large image plane, high projection quality and the like, has different amplification factors in the meridian direction and the sagittal direction, and can meet the use requirements of a projection target area.

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 expectations for a better driving experience continue to rise, the use of in-vehicle projection lenses for intelligent driving is increasing, and their status in the automotive industry continues to rise. A head-up display (HUD), also known as a head-up display, utilizes optical reflection principles to project driver assistance information, navigation information, check and control information, and ADAS information onto the windshield, approximately 2 meters ahead, or above the tip of the hood. It can also display warnings from various driver assistance systems, such as lane departure warnings and pedestrian avoidance warnings from night vision assistance systems with pedestrian recognition. This prevents drivers from frequently looking down at the instrument panel or onboard screen while driving, significantly enhancing driving safety.

[0003] However, the projection lenses currently used for automotive HUDs have a very low utilization rate of the display chip due to the large difference between the aspect ratio of the image plane (field of view ratio) and the aspect ratio of the object plane (i.e. the aspect ratio of the display chip, such as 16:9). At the same time, the field of view is small, and the projected pattern is prone to vignetting. The brightness at the projection surface is insufficient, resulting in unclear patterns and other defects, making 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 characteristic of excellent projection quality.

[0005] The technical solution adopted in the present invention is: A projection lens, comprising eight lenses, including the following lenses in order from the projection plane to the image source plane along the optical axis: a first lens having positive refractive power, wherein the projection-side surface thereof is convex and the image-source-side surface thereof is convex; a second lens having negative optical power, wherein the projection-side surface thereof is concave and the image-source-side surface thereof is concave; a third lens element having positive refractive power, whose projection-side surface is concave and whose image-source-side surface is convex; a fourth lens element having negative optical power, wherein the projection-side surface thereof is concave and the image-source-side surface thereof is concave; a fifth lens element having positive refractive power, whose projection-side surface is concave and whose image-source-side surface is convex; a sixth lens element having negative optical power, wherein the projection-side surface thereof is concave and the image-source-side surface thereof is concave; a seventh lens element having positive refractive power, wherein the projection-side surface thereof is convex and the image-source-side surface thereof is convex; The eighth lens with a positive optical power, having a convex projection-side surface and a convex image-source side surface; The first lens and the second lens are cylindrical lenses, having optical power in the sagittal section direction, i.e., the y direction, and no optical power in the meridional section direction, i.e., the x direction; Wherein, the combined focal length f12345x of the first lens, the second lens, the third lens, the fourth lens and the fifth lens in the x direction and the combined focal length f678 of the sixth lens, the seventh lens and the eighth lens satisfy: -3.7 < f12345x / f678 < -2.8; the combined focal length f12345y of the first lens, the second lens, the third lens, the fourth lens and the fifth lens in the y direction and the combined focal length f678 of the sixth lens, the seventh lens and the eighth lens satisfy: -5.5 < f12345y / f678 < -4.

[0006] Further preferably, the true image height IHx corresponding to the maximum field angle of view of the projection lens in the x direction, the effective focal length fx of the projection lens in the x direction and the maximum field angle of view FOVx of the projection lens in the x direction satisfy: 1.03 < (IHx / 2) / (fx*Tan(FOVx / 2)) < 1.05; the true image height IHy corresponding to the maximum field angle of view of the projection lens in the y direction, the effective focal length fy of the projection lens in the y direction and the maximum field angle of view FOVy of the projection lens in the y direction satisfy: 0.98 < (IHy / 2) / (fy*Tan(FOVy / 2)) < 1.

[0007] Further preferably, the clear aperture radius d1 of the projection-side surface of the first lens, the true image height IHx corresponding to the maximum field angle of view of the projection lens in the x direction and the maximum field angle of view FOVx of the projection lens in the x direction satisfy: 32 < d1 / (IHx / 2) / tan(FOVx / 2) < 33; the clear aperture radius d1 of the projection-side surface of the first lens, the true image height IHy corresponding to the maximum field angle of view of the projection lens in the y direction and the maximum field angle of view FOVy of the projection lens in the y direction satisfy: 14 < d1 / (IHy / 2) / tan(FOVy / 2) < 15.

[0008] More preferably, the focal length f3 of the third lens and the effective focal length fx of the projection lens in the x direction satisfy: 2.9 < f3 / fx < 3.6; the radius of curvature R5 of the projection-side surface of the third lens and the effective focal length fx of the projection lens in the x direction satisfy: -7.3 < R5 / fx < -4.5; the radius of curvature R6 of the image-source-side surface of the third lens and the effective focal length fx of the projection lens in the x direction satisfy: -2.3 < R6 / fx < -1.8.

[0009] More preferably, the focal length f7 of the seventh lens and the effective focal length fx of the projection lens in the x direction satisfy: 2.1 < f7 / fx < 2.6; the radius of curvature R13 of the projection-side surface of the seventh lens and the effective focal length fx of the projection lens in the x direction satisfy: 4.1 < R13 / fx < 5.2; the radius of curvature R14 of the image-source-side surface of the seventh lens and the effective focal length fx of the projection lens in the x direction satisfy: -1.5 < R14 / fx < -1.3.

[0010] More preferably, the focal length f1 of the first lens and the effective focal length fy of the projection lens in the y direction satisfy: 3.6 < f1 / fy < 4.6; the focal length f2 of the second lens and the effective focal length fy of the projection lens in the y direction satisfy: -4.3 < f2 / fy < -3.4.

[0011] More preferably, the focal length f3 of the third lens and the effective focal length fy of the projection lens in the y direction satisfy: 2.2 < f3 / fy < 2.8; the radius of curvature R5 of the projection-side surface of the third lens and the effective focal length fy of the projection lens in the y direction satisfy: -5.8 < R5 / fy < -3.5; the radius of curvature R6 of the image-source-side surface of the third lens and the effective focal length fy of the projection lens in the y direction satisfy: -1.8 < R6 / fy < -1.3.

[0012] More preferably, the focal length f7 of the seventh lens and the effective focal length fy of the projection lens in the y direction satisfy: 1.7 < f / fy < 2.1; the radius of curvature R13 of the projection-side surface of the seventh lens and the effective focal length fy of the projection lens in the y direction satisfy: 3.2 < R13 / fy < 4; the radius of curvature R14 of the image-source-side surface of the seventh lens and the effective focal length fy of the projection lens in the y direction satisfy: -1.2 < R14 / fy < -1.

[0013] More preferably, the radius of curvature R5 of the object side surface of the third lens and the radius of curvature R6 of the image side surface of the third lens satisfy: 2.4 < R5 / R6 < 3.5; the radius of curvature R7 of the object side surface of the fourth lens and the radius of curvature R8 of the image side surface of the fourth lens satisfy: -1.8 < R7 / R8 < -1.3.

[0014] More preferably, the radius of curvature R5 of the object side surface of the third lens and the radius of curvature R6 of the image side surface of the third lens satisfy: 0.3 < (R5 - R6) / (R5 + R6) < 0.7; the radius of curvature R7 of the object side surface of the fourth lens and the radius of curvature R8 of the image side surface of the fourth lens satisfy: 0 < (R7 + R8) / (R7 - R8) < 0.4.

[0015] Compared with the prior art, 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 combination of optical powers, making the lens have one or more advantages such as small distortion, small CRA, large image plane, and high projection quality. At the same time, by using a cylindrical lens, the projection lens can have different magnification ratios in the meridian direction and the sagittal direction, enabling the projection lens to have the characteristic that the size ratios of the object plane in the meridian direction and the sagittal direction are different from those of the projection plane in the meridian direction and the sagittal direction, meeting the usage requirements of the projection target area. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and easy to understand from the following description of the embodiments in conjunction with the accompanying drawings, in which: Figure 1 is a schematic structural diagram of the projection lens in Embodiment 1 of the present invention.

[0017] Figure 2 is a perspective view of the first lens and the second lens in the projection lens in Embodiment 1 of the present invention.

[0018] Figure 3 is a graph of F-Tan(Theta) distortion in the x direction of the projection lens in Embodiment 1 of the present invention.

[0019] Figure 4 is a graph of F-Tan(Theta) distortion in the y direction of the projection lens in Embodiment 1 of the present invention.

[0020] Figure 5 is a MTF graph of the projection lens in Embodiment 1 of the present invention.

[0021] Figure 6 is a schematic structural diagram of the projection lens in Embodiment 2 of the present invention.

[0022] Figure 7FIG. 4 is a graph showing the F-Tan (Theta) distortion curve in the x-direction of the projection lens in Example 2 of the present invention.

[0023] Figure 8 FIG. 4 is a graph showing the F-Tan (Theta) distortion curve in the y direction of the projection lens in Example 2 of the present invention.

[0024] Figure 9 This is an MTF curve diagram of the projection lens in Example 2 of the present invention.

[0025] Figure 10 Schematic diagram of the structure of the projection lens in Example 3 of the present invention.

[0026] Figure 11 FIG. 4 is a graph showing the F-Tan (Theta) distortion curve in the x-direction of the projection lens in Example 3 of the present invention.

[0027] Figure 12 FIG. 4 is a graph showing the F-Tan (Theta) distortion curve in the y direction of the projection lens in Example 3 of the present invention.

[0028] Figure 13 This is an MTF curve diagram of the projection lens in Example 3 of the present invention.

[0029] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0030] For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely descriptions of 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.

[0031] It should be noted that in this specification, the terms "first," "second," "third," etc., are used solely to distinguish one feature from another and do not limit the features. Thus, the first lens discussed below could also be referred to as the second lens or the third lens without departing from the teachings of the present invention.

[0032] In the drawings, the thickness, size, and shape of the lenses are slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical and aspherical surfaces shown in the drawings are provided by way of example. That is, the shapes of the spherical and aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustration only and are not drawn strictly to scale.

[0033] In this article, the paraxial region refers to the area near the optical axis. If a lens surface is convex and the location of the convex surface is undefined, it means that the lens surface is convex at least in the paraxial region. If a lens surface is concave and the location of the concave surface is undefined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the projection plane is called the projection-side surface of the lens, and the surface of each lens closest to the image source plane is called the image source-side surface of the lens.

[0034] 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 preclude 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 list of 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.

[0035] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and will not be interpreted in an idealized or overly formal sense unless expressly defined as such herein.

[0036] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this 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.

[0037] The projection lens provided in an embodiment of the present invention comprises eight lenses, comprising, in order from the projection plane to the image source plane, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens, along the optical axis. Both the first and second lenses are cylindrical lenses. The first and second lenses have optical power in the sagittal cross-section, i.e., the y-direction, and no optical power in the meridional cross-section, i.e., the x-direction. Cylindrical lenses can control asymmetric optical paths and are suitable for applications requiring one-dimensional focusing, beam shaping, or astigmatism correction. It is understood that cylindrical lenses only have refractive power for light in the sagittal direction, enabling the projection lens to have different magnifications in the meridional and sagittal directions, thereby improving the utilization of the effective area of the light-emitting chip. Furthermore, to meet the requirements of the projection target area, the projection lens has different dimensional ratios in the meridional and sagittal directions of the image source plane than in the meridional and sagittal directions of the projection plane. This allows for a suitable dimensional ratio in the meridional and sagittal directions of the projection plane to meet the requirements.

[0038] Specifically, the first lens may have positive focal power, with its projection-side surface being convex and its image-source-side surface being convex. The second lens may have negative focal power, with its projection-side surface being concave and its image-source-side surface being concave. The third lens may have positive focal power, with its projection-side surface being concave and its image-source-side surface being convex. The fourth lens may have negative focal power, with its projection-side surface being concave and its image-source-side surface being concave. The fifth lens may have positive focal power, with its projection-side surface being concave and its image-source-side surface being convex. The sixth lens may have negative focal power, with its projection-side surface being concave and its image-source-side surface being concave. The seventh lens may have positive focal power, with its projection-side surface being convex and its image-source-side surface being convex. The eighth lens may have positive focal power, with its projection-side surface being convex and its image-source-side surface being convex.

[0039] In some embodiments, the projection lens may further include an aperture, which may be located between the fifth and sixth lenses. It will be appreciated that the aperture is used to limit the amount of light entering, thereby varying the brightness of the resulting image. Positioning the aperture between the fifth and sixth lenses facilitates correction of aperture aberrations.

[0040] In some embodiments, the projection lens may further include a protective glass disposed between the eighth lens and the image source surface. The protective glass protects the projection lens and prevents the light-emitting chip from being damaged and affecting the imaging effect of the lens.

[0041] In some embodiments, the sixth lens and the seventh lens can be cemented to form a cemented lens, 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 projection 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.

[0042] In some embodiments, the combined focal length f12345x of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens in the x direction and the combined focal length f678 of the sixth lens, the seventh lens, and the eighth lens satisfy: -3.7 < f12345x / f678 < -2.8; the combined focal length f12345y of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens in the y direction and the combined focal length f678 of the sixth lens, the seventh lens, and the eighth lens satisfy: -5.5 < f12345y / f678 < -4. Meeting the above ranges is beneficial to balancing the aberrations generated by the lens groups before and after the aperture and improving the projection quality of the projection lens. More specifically, -3.35 < f12345x / f678 < -3.07; -4.95 < f12345y / f678 < -4.5.

[0043] In some embodiments, the true image height IHx corresponding to the maximum field angle in the x direction of the projection lens, the effective focal length fx of the projection lens in the x direction, and the maximum field angle FOVx of the projection lens in the x direction satisfy: 1.03 < (IHx / 2) / (fx*Tan(FOVx / 2)) < 1.05; the true image height IHy corresponding to the maximum field angle in the y direction of the projection lens, the effective focal length fy of the projection lens in the y direction, and the maximum field angle FOVy of the projection lens in the y direction satisfy: 0.98 < (IHy / 2) / (fy*Tan(FOVy / 2)) < 1. Meeting the above ranges enables better control of the optical distortion of the projection lens in the sagittal section direction and in the meridional section direction, improves the resolution of the projection lens, and can achieve a better projection effect, making it more suitable for human eyes to view.

[0044] In some embodiments, the clear aperture semi-diameter d1 of the projection side surface of the first lens, the true image height IHx corresponding to the maximum field angle in the x direction of the projection lens, and the maximum field angle FOVx of the projection lens in the x direction satisfy: 32 < d1 / (IHx / 2) / tan(FOVx / 2) < 33; the clear aperture semi-diameter d1 of the projection side surface of the first lens, the true image height IHy corresponding to the maximum field angle in the y direction of the projection lens, and the maximum field angle FOVy of the projection lens in the y direction satisfy: 14 < d1 / (IHy / 2) / tan(FOVy / 2) < 15. Meeting the above ranges can have a small front port diameter while meeting the requirements of the projection lens having a large field angle and a large image plane, which is beneficial to the miniaturization of the projection lens. More specifically, 32.85 < d1 / (IHx / 2) / tan(FOVx / 2) < 32.89; 14.58 < d1 / (IHy / 2) / tan(FOVy / 2) < 14.61.

[0045] In some embodiments, the focal length f3 of the third lens and the effective focal length fx of the projection lens in the x direction satisfy: 2.9 < f3 / fx < 3.6; the radius of curvature R5 of the projection side surface of the third lens and the effective focal length fx of the projection lens in the x direction satisfy: -7.3 < R5 / fx < -4.5; the radius of curvature R6 of the image source side surface of the third lens and the effective focal length fx of the projection lens in the x direction satisfy: -2.3 < R6 / fx < -1.8. The focal length f3 of the third lens and the effective focal length fy of the projection lens in the y direction satisfy: 2.2 < f3 / fy < 2.8; the radius of curvature R5 of the projection side surface of the third lens and the effective focal length fy of the projection lens in the y direction satisfy: -5.8 < R5 / fy < -3.5; the radius of curvature R6 of the image source side surface of the third lens and the effective focal length fy of the projection lens in the y direction satisfy: -1.8 < R6 / fy < -1.3. Meeting the above ranges can enable the third lens to have an appropriate positive optical power and surface shape, effectively balance lens aberrations, and improve the projection quality. More specifically, 3.16 < f3 / fx < 3.29; -6.75 < R5 / fx < -5.06; -2.09 < R6 / fx < -1.93; 2.44 < f3 / fy < 2.55; -5.24 < R5 / fy < -3.91; -1.62 < R6 / fy < -1.49.

[0046] In some embodiments, the focal length f7 of the seventh lens and the effective focal length fx of the projection lens in the x direction satisfy: 2.1 < f7 / fx < 2.6; the radius of curvature R13 of the projection side surface of the seventh lens and the effective focal length fx of the projection lens in the x direction satisfy: 4.1 < R13 / fx < 5.2; the radius of curvature R14 of the image source side surface of the seventh lens and the effective focal length fx of the projection lens in the x direction satisfy: -1.5 < R14 / fx < -1.3. The focal length f7 of the seventh lens and the effective focal length fy of the projection lens in the y direction satisfy: 1.7 < f7 / fy < 2.1; the radius of curvature R13 of the projection side surface of the seventh lens and the effective focal length fy of the projection lens in the y direction satisfy: 3.2 < R13 / fy < 4; the radius of curvature R14 of the image source side surface of the seventh lens and the effective focal length fy of the projection lens in the y direction satisfy: -1.2 < R14 / fy < -1. Meeting the above ranges, the seventh lens has an appropriate positive optical power, which is beneficial to converging light while reducing the light deflection angle, making the light trend transition smoothly, and improving the projection quality of the projection lens. More specifically, 2.34 < f7 / fx < 2.42; 4.155 < R13 / fx < 4.74; -1.41 < R14 / fx < -1.35. 1.81 < f7 / fy < 1.88; 3.52 < R13 / fy < 3.67; -1.09 < R14 / fy < -1.04.

[0047] In some embodiments, the focal length f1 of the first lens and the effective focal length fy of the projection lens in the y direction satisfy: 3.6 < f1 / fy < 4.6; the focal length f2 of the second lens and the effective focal length fy of the projection lens in the y direction satisfy: -4.3 < f2 / fy < -3.4. Meeting the above ranges can balance the distribution of the focal lengths of the front-end lenses of the projection lens, reduce the aberration correction pressure on the rear-end lenses, and improve the projection quality of the projection lens. More specifically, 3.97 < f1 / fy < 4.15; -3.92 < f2 / fy < -3.72. It can be understood that the first lens and the second lens are cylindrical lenses, having optical power in the sagittal section direction, i.e., the y direction, and no optical power in the meridional section direction, i.e., the x direction. That is, f1 is also the focal length of the first lens in the y direction, and f2 is also the focal length of the second lens in the y direction.

[0048] In some embodiments, the radius of curvature R5 of the object side surface of the third lens and the radius of curvature R6 of the image side surface of the third lens satisfy: 2.4 < R5 / R6 < 3.5; the radius of curvature R5 of the object side surface of the third lens and the radius of curvature R6 of the image side surface of the third lens satisfy: 0.3 < (R5 - R6) / (R5 + R6) < 0.7. Meeting the above ranges, the third lens has a meniscus shape, which is beneficial to correcting the distortion of the projection lens. More specifically, 2.6 < R5 / R6 < 3.25; 0.44 < (R5 - R6) / (R5 + R6) < 0.54.

[0049] In some embodiments, the radius of curvature R7 of the object side surface of the fourth lens and the radius of curvature R8 of the image side surface of the fourth lens satisfy: -1.8 < R7 / R8 < -1.3; the radius of curvature R7 of the object side surface of the fourth lens and the radius of curvature R8 of the image side surface of the fourth lens satisfy: 0 < (R7 + R8) / (R7 - R8) < 0.4. Meeting the above ranges, the fourth lens has a biconcave shape, which is beneficial to the divergence of light rays, increases the imaging area while achieving a large field of view. More specifically, -1.65 < R7 / R8 < -1.43; 0.17 < (R7 + R8) / (R7 - R8) < 0.25.

[0050] In some embodiments, the total optical length TTL of the projection lens and the effective focal length fx of the projection lens in the x direction satisfy: 6.5 < TTL / fx < 7.2; the total optical length TTL of the projection lens and the effective focal length fy of the projection lens in the y direction satisfy: 5 < TTL / fy < 5.5. Meeting the above ranges can achieve the long focal length characteristics of the lens, effectively limit the length of the lens, and is beneficial to the miniaturization of the projection lens. More specifically, 6.98 < TTL / fx < 7.01; 5.4 < TTL / fy < 5.43.

[0051] In some embodiments, the back focal length BFL of the projection lens and the effective focal length fx of the projection lens in the x-direction satisfy: 2.3 < BFL / fx < 2.4; the back focal length BFL of the projection lens and the effective focal length fy of the projection lens in the y-direction satisfy: 1.8 < BFL / fy < 1.9. Meeting the above ranges is conducive to achieving a balance between obtaining good imaging quality and an optical back focal length that is easy to assemble. While ensuring the projection 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, 2.33 < BFL / fx < 2.36; 1.8 < BFL / fy < 1.83.

[0052] In some embodiments, the sum ∑CT of the central thicknesses of the first lens to the eighth lens along the optical axis respectively and the effective focal length fx of the projection lens in the x-direction satisfy: 2.3 < ∑CT / fx < 2.5; the sum ∑CT of the central thicknesses of the first lens to the eighth lens along the optical axis respectively and the effective focal length fy of the projection lens in the y-direction satisfy: 1.8 < ∑CT / fy < 1.9. Meeting the above ranges can effectively correct the field curvature and distortion of the projection lens and improve the projection quality of the projection lens. More specifically, 2.33 < ∑CT / fx < 2.43; 1.81 < ∑CT / fy < 1.88.

[0053] In some embodiments, the effective focal length fx of the projection lens in the x-direction and the effective focal length fy of the projection lens in the y-direction satisfy: 0.76 < fx / fy < 0.79. Meeting the above ranges, setting the effective focal length in the sagittal section direction (y-direction) of the projection lens to be greater than the effective focal length in the meridional section direction (x-direction) realizes different magnification ratios in the sagittal and meridional directions, and thus obtains appropriate size ratios in the sagittal and meridional directions on the projection plane to meet the usage requirements of the projection target area.

[0054] In some embodiments, the focal length f8 of the eighth lens and the effective focal length fx of the projection lens in the x-direction satisfy: 1.7 < f8 / fx < 1.8; the focal length f8 of the eighth lens and the effective focal length fy of the projection lens in the y-direction satisfy: 1.3 < f8 / fy < 1.4. Meeting the above ranges, the eighth lens has an appropriate positive optical power, which is conducive to converging light while reducing the light deflection angle, enabling the light to transition smoothly, and improving the projection quality of the projection lens. More specifically, 1.74 < f8 / fx < 1.77; 1.35 < f8 / fy < 1.37.

[0055] In some embodiments, the radius of curvature R7 of the projection side surface of the fourth lens and the effective focal length fx of the projection lens in the x direction satisfy: -1.6 < R7 / fx < -1.3; the radius of curvature R8 of the image source side surface of the fourth lens and the effective focal length fx of the projection lens in the x direction satisfy: 0.9 < R8 / fx < 1.1; the radius of curvature R7 of the projection side surface of the fourth lens and the effective focal length fy of the projection lens in the y direction satisfy: -1.3 < R7 / fy < -1; the radius of curvature R8 of the image source side surface of the fourth lens and the effective focal length fy of the projection lens in the y direction satisfy: 0.6 < R8 / fy < 0.9. Meeting the above ranges, the fourth lens has a double concave shape, which is conducive to the divergence of light, increases the projection area while achieving a large viewing field. More specifically, -1.53 < R7 / fx < -1.4; 0.92 < R8 / fx < 0.99; -1.19 < R7 / fy < -1.08; 0.71 < R8 / fy < 0.77.

[0056] In some embodiments, the projection lens satisfies the conditional formula: 12 mm < fx < 13 mm, 6.4 mm < EPDx < 6.5 mm, 0.6° < CRAx < 0.7°, 4.5 mm < IHx < 4.6 mm, 19° < FOVx < 20°; 16 mm < fy < 17 mm, 8.3 mm < EPDy < 8.4 mm, 1° < CRAy < 1.1°, 7.6 mm < IHy < 7.7 mm, 26° < FOVy < 27°; 89 mm < TTL < 90 mm, 1.9 < Fno < 2.1, 30 mm < BFL < 32 mm, 30° < DFOV < 35°, where fx and fy respectively represent the effective focal lengths of the projection lens in the x-direction and the y-direction, EPDx and EPDy respectively represent the entrance pupil diameters of the projection lens in the x-direction and the y-direction, CRAx and CRAy respectively represent the principal ray incident angles at the maximum image height of the projection lens in the x-direction and the y-direction, IHx and IHy respectively represent the true image heights corresponding to the maximum field angles of the projection lens in the x-direction and the y-direction, FOVx and FOVy respectively represent the maximum field angles of the projection lens in the x-direction and the y-direction, TTL represents the total optical length of the projection lens, Fno represents the aperture value of the projection lens, BFL represents the back focal length of the projection lens, and DFOV represents the maximum diagonal field angle of the projection lens. Meeting the above conditions indicates that the projection lens provided by the embodiments of the present invention at least has characteristics such as a small CRA, a large image plane, and a long back focal length. More specifically, 12.84 mm < fx < 12.86 mm, 6.46 mm < EPDx < 6.48 mm, 0.63° < CRAx < 0.69°, 4.58 mm < IHx < 4.6 mm, 19.54° < FOVx < 19.57°; 16.57 mm < fy < 16.62 mm, 8.33 mm < EPDy < 8.37 mm, 1.02° < CRAy < 1.09°, 7.64 mm < IHy < 7.66 mm, 26.2° < FOVy < 26.23°; 89.89 mm < TTL < 89.91 mm, 1.98 < Fno < 2, 30.02 mm < BFL < 30.16 mm, 32.68° < DFOV < 32.72°.

[0057] In some embodiments, all eight lenses in the projection lens can be made of plastic lenses or adopt a structure with a combination of glass and plastic materials. Preferably, the projection lens of the present invention adopts a structure of eight lenses with a combination of glass and plastic, which can improve the thermal stability performance. Specifically, the fifth lens can be made of a plastic lens, and the first lens, the second lens, the third lens, the fourth lens, the sixth lens, the seventh lens, and the eighth lens are all glass lenses; adopting a glass-plastic hybrid structure can effectively reduce costs, correct aberrations, reduce the volume, and provide a projection lens product with higher cost performance.

[0058] In some embodiments, the first, second, third, fourth, fifth, sixth, seventh, and eighth lenses may be spherical or aspherical lenses. Compared to spherical lenses, aspherical structures can effectively reduce aberrations in the optical system, thereby reducing the number and size of lenses and achieving better lens miniaturization. More specifically, in the projection lens provided by the present invention, the fifth and eighth lenses may be aspherical lenses, while the first, second, third, fourth, sixth, and seventh lenses may be spherical lenses.

[0059] In various embodiments of the present invention, when the lens is an aspheric lens, the shapes of the aspheric surfaces of the projection lens satisfy the following equations: ; Where z is the distance between the surface and the vertex 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, and B, C, D, E, and F are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order surface coefficients, respectively.

[0060] The present invention is further illustrated below with reference to several embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens vary; for details, please refer to the parameter tables for each embodiment. The following embodiments are merely preferred embodiments of the present invention, but the present invention is not limited to these embodiments. Any other changes, substitutions, combinations, or simplifications that do not deviate from the novelties of the present invention shall be considered equivalent replacements and are within the scope of protection of the present invention.

[0061] Example 1 See also Figure 1 , Figure 1 is a schematic structural diagram of the projection lens 100 provided in Example 1 of the present invention, Figure 2 : This is a stereoscopic diagram of the first lens L1 and the second lens L2 in the projection lens 100. The projection lens 100 includes, in order from the projection plane to the image source plane S22 along the optical axis: the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the aperture stop ST, the sixth lens L6, the seventh lens L7, the eighth lens L8, the protective glass G1, the protective glass G2, and the protective glass G3.

[0062] The first lens L1 has positive refractive power, its projection-side surface S1 is convex, and its image-source-side surface S2 is convex; The second lens L2 has negative refractive power, its projection-side surface S3 is concave, and its image-source-side surface S4 is concave; The third lens L3 has positive refractive power, its projection-side surface S5 is concave, and its image-source-side surface S6 is convex; The fourth lens L4 has negative refractive power, its projection-side surface S7 is concave, and its image-source-side surface S8 is concave; The fifth lens L5 has positive refractive power, its projection-side surface S9 is concave, and its image-source-side surface S10 is convex; The sixth lens L6 has negative refractive power, its projection-side surface S11 is concave, and its image-source-side surface is also concave. The seventh lens L7 has positive refractive power, its projection-side surface is convex, and its image-source-side surface S13 is convex. The sixth lens L6 and the seventh lens L7 form a cemented lens group with negative refractive power. The cemented surface between the image source side surface of the sixth lens L6 and the projection side surface of the seventh lens L7 is S12. The eighth lens L8 has positive refractive power, its projection-side surface S14 is convex, and its image-source-side surface S15 is convex. The first lens L1 and the second lens L2 are glass cylindrical lenses. It should be understood that in this application, both the first lens L1 and the second lens L2 are cylindrical lenses. The first lens L1 and the second lens L2 have optical power in the y-direction (sagittal cross-section direction) and no optical power in the x-direction (meridional cross-section direction). Cylindrical lenses can control asymmetric optical paths and are suitable for applications requiring one-dimensional focusing, beam shaping, or astigmatism correction.

[0063] The fifth lens L5 is a plastic aspherical lens, the eighth lens L8 is a glass aspherical lens, and the third lens L3, the fourth lens L4, the sixth lens L6, and the seventh lens L7 are all glass spherical lenses.

[0064] The relevant parameters of each lens in the projection lens 100 in Example 1 are shown in Table 1-1.

[0065] Table 1-1 The surface parameters of the aspheric lens of the projection lens 100 in Example 1 are shown in Table 1-2.

[0066] Table 1-2 In this embodiment, the F-Tan (Theta) distortion curve in the x-direction, the F-Tan (Theta) distortion curve in the y-direction, and the MTF curve of the projection lens 100 are shown as follows: Figure 3 、 Figure 4 、 Figure 5 shown.

[0067] Figure 3The F-Tan (Theta) distortion curve in the x-direction for Example 1 shows distortion at different field angles on the image source plane. The horizontal axis represents the distortion value (unit: %), and the vertical axis represents the half field angle (unit: degrees). As can be seen from the figure, the distortion of projection lens 100 is controlled within a range of -2% to 0, indicating that projection lens 100 is capable of effectively correcting distortion.

[0068] Figure 4 The F-Tan (Theta) distortion curve in the y-direction of Example 1 shows distortion at different field angles on the image source plane. The horizontal axis represents the distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the distortion of projection lens 100 is controlled within a range of -2% to 0, indicating that projection lens 100 is capable of good distortion correction.

[0069] Figure 5 The MTF (Modulation Transfer Function) curve for Example 1 is shown. It represents the degree of lens modulation at different spatial frequencies across the field of view. The horizontal axis represents spatial frequency (lp / mm), and the vertical axis represents the MTF value. As can be seen from the graph, the MTF value of this example is consistently above 0.2 across the entire field of view. Within the range of 0 to 90 lp / mm, the MTF curve decreases evenly and smoothly from the center to the edges of the field of view, demonstrating excellent projection quality and detail resolution at both low and high frequencies.

[0070] Example 2 See also Figure 6 , shown is a schematic structural diagram of a projection lens 200 provided in Example 2 of the present invention. Compared with Example 1, this embodiment mainly differs in that optical parameters such as the curvature radius of each lens surface, lens thickness, and the distance between lenses are different.

[0071] The relevant parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2-1.

[0072] Table 2-1 The surface parameters of the aspheric lens of the projection lens 200 in Example 2 are shown in Table 2-2.

[0073] Table 2-2 In this embodiment, the F-Tan (Theta) distortion curve in the x-direction, the F-Tan (Theta) distortion curve in the y-direction, and the MTF curve of the projection lens 200 are shown as follows: Figure 7 、 Figure 8 、 Figure 9 shown.

[0074] from Figure 7 It can be seen from the figure that the distortion of the projection lens 200 in the x direction is controlled within a range of -2% to 0, indicating that the projection lens 200 can correct the distortion well. Figure 8 It can be seen from the figure that the distortion in the y direction of the projection lens 200 is controlled within a range of -2% to 0, indicating that the projection lens 200 can correct the distortion well. Figure 9 As can be seen from the figure, the MTF value of this embodiment is above 0.3 throughout the entire field of view. In the range of 0 to 90 lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, achieving good projection quality and detail resolution in both low-frequency and high-frequency conditions.

[0075] Example 3 See also Figure 10 , shown is a schematic structural diagram of a projection lens 300 provided in Example 3 of the present invention. Compared with Example 1, this embodiment mainly differs in that optical parameters such as the curvature radius of each lens surface, lens thickness, and the distance between lenses are different.

[0076] The relevant parameters of each lens in the projection lens 300 in Example 3 are shown in Table 3-1.

[0077] Table 3-1 The surface parameters of the aspheric lens of the projection lens 300 in Example 3 are shown in Table 3-2.

[0078] Table 3-2 In this embodiment, the F-Tan (Theta) distortion curve in the x-direction, the F-Tan (Theta) distortion curve in the y-direction, and the MTF curve of the projection lens 300 are shown as follows: Figure 11 、 Figure 12 、 Figure 13 shown.

[0079] from Figure 11 It can be seen from the figure that the distortion of the projection lens 300 in the x direction is controlled within a range of -2% to 0, indicating that the projection lens 300 can correct the distortion well. Figure 12 It can be seen from the figure that the distortion of the projection lens 300 in the y direction is controlled within a range of -2% to 0, indicating that the projection lens 300 can correct the distortion well. Figure 13 As can be seen from the figure, the MTF value of this embodiment is above 0.3 throughout the entire field of view. In the range of 0 to 90 lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, achieving good projection quality and detail resolution in both low-frequency and high-frequency conditions.

[0080] Please refer to Table 4-1 and Table 4-2, which show the optical characteristics of the projection lens of the above embodiments, including the effective focal length fx of the projection lens in the x-direction, the real image height IHx corresponding to the maximum field of view angle, and the maximum field of view angle FOVx; the effective focal length fy in the y-direction, the real image height IHy corresponding to the maximum field of view angle, and the maximum field of view angle FOVy; the total optical length TTL, the aperture value Fno, the maximum diagonal field of view angle DFOV, etc., as well as the numerical values corresponding to each conditional expression in each embodiment.

[0081] Table 4-1 Table 4-2 In summary, the projection lens provided by the present invention improves imaging quality, reduces aberrations, and enhances projection quality through the rational configuration of lens surface shapes and the rational matching of optical powers. This allows the lens to exhibit one or more advantages, including low distortion, low CRA, a large image surface, and high projection quality. Furthermore, the use of cylindrical lenses enables the projection lens to have different magnifications in the meridional and sagittal directions, resulting in different dimensional ratios between the image source plane in the meridional and sagittal directions and the projection plane in the meridional and sagittal directions, thus meeting the requirements of the projection target area.

[0082] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0083] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A projection lens, comprising eight lenses, characterized in that: It successively includes, along the optical axis from the projection plane to the image source plane: A first lens with positive optical power, whose projection-side surface is convex and whose image-source side surface is convex; A second lens with negative optical power, whose projection-side surface is concave 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 and whose image-source side surface is concave; A fifth lens with positive optical power, whose projection-side surface is concave and whose image-source side surface is convex; A sixth lens with negative optical power, whose projection-side surface is concave and whose image-source side surface is concave; A seventh lens with positive optical power, whose projection-side surface is convex and whose image-source side surface is convex; An eighth lens with positive optical power, whose projection-side surface is convex and whose image-source side surface is convex; The first lens and the second lens are cylindrical lenses. The first lens and the second lens have optical power in the sagittal section direction, i.e., the y direction, and have no optical power in the meridional section direction, i.e., the x direction; Among them, the combined focal length f12345x of the first lens, the second lens, the third lens, the fourth lens and the fifth lens in the x direction and the combined focal length f678 of the sixth lens, the seventh lens and the eighth lens satisfy: -3.7 < f12345x / f678 < -2.8; the combined focal length f12345y of the first lens, the second lens, the third lens, the fourth lens and the fifth lens in the y direction and the combined focal length f678 of the sixth lens, the seventh lens and the eighth lens satisfy: -5.5 < f12345y / f678 < -4.

2. The projection lens according to claim 1, wherein: The true image height IHx corresponding to the maximum field angle of view of the projection lens in the x direction, the effective focal length fx of the projection lens in the x direction and the maximum field angle of view FOVx of the projection lens in the x direction satisfy: 1.03 < (IHx / 2) / (fx * Tan(FOVx / 2)) < 1.05; the true image height IHy corresponding to the maximum field angle of view of the projection lens in the y direction, the effective focal length fy of the projection lens in the y direction and the maximum field angle of view FOVy of the projection lens in the y direction satisfy: 0.98 < (IHy / 2) / (fy * Tan(FOVy / 2)) < 1.

3. The projection lens according to claim 1, wherein: The clear aperture semi-diameter d1 of the projection-side surface of the first lens, the true image height IHx corresponding to the maximum field angle of view of the projection lens in the x direction and the maximum field angle of view FOVx of the projection lens in the x direction satisfy: 32 < d1 / (IHx / 2) / tan(FOVx / 2) < 33; the clear aperture semi-diameter d1 of the projection-side surface of the first lens, the true image height IHy corresponding to the maximum field angle of view of the projection lens in the y direction and the maximum field angle of view FOVy of the projection lens in the y direction satisfy: 14 < d1 / (IHy / 2) / tan(FOVy / 2) < 15.

4. The projection lens according to claim 1, wherein: The focal length f3 of the third lens and the effective focal length fx of the projection lens in the x direction satisfy: 2.9 < f3 / fx < 3.6; the radius of curvature R5 of the projection side surface of the third lens and the effective focal length fx of the projection lens in the x direction satisfy: -7.3 < R5 / fx < -4.5; the radius of curvature R6 of the image source side surface of the third lens and the effective focal length fx of the projection lens in the x direction satisfy: -2.3 < R6 / fx < -1.

8.

5. The projection lens according to claim 1, wherein: The focal length f7 of the seventh lens and the effective focal length fx of the projection lens in the x direction satisfy: 2.1 < f7 / fx < 2.6; the radius of curvature R13 of the projection side surface of the seventh lens and the effective focal length fx of the projection lens in the x direction satisfy: 4.1 < R13 / fx < 5.2; the radius of curvature R14 of the image source side surface of the seventh lens and the effective focal length fx of the projection lens in the x direction satisfy: -1.5 < R14 / fx < -1.

3.

6. The projection lens according to claim 1, wherein: The focal length f1 of the first lens and the effective focal length fy of the projection lens in the y direction satisfy: 3.6 < f1 / fy < 4.6; the focal length f2 of the second lens and the effective focal length fy of the projection lens in the y direction satisfy: -4.3 < f2 / fy < -3.

4.

7. The projection lens according to claim 1, wherein: The focal length f3 of the third lens and the effective focal length fy of the projection lens in the y direction satisfy: 2.2 < f3 / fy < 2.8; the radius of curvature R5 of the projection side surface of the third lens and the effective focal length fy of the projection lens in the y direction satisfy: -5.8 < R5 / fy < -3.5; the radius of curvature R6 of the image source side surface of the third lens and the effective focal length fy of the projection lens in the y direction satisfy: -1.8 < R6 / fy < -1.

3.

8. The projection lens according to claim 1, wherein: The focal length f7 of the seventh lens and the effective focal length fy of the projection lens in the y direction satisfy: 1.7 < f7 / fy < 2.1; the radius of curvature R13 of the projection side surface of the seventh lens and the effective focal length fy of the projection lens in the y direction satisfy: 3.2 < R13 / fy < 4; the radius of curvature R14 of the image source side surface of the seventh lens and the effective focal length fy of the projection lens in the y direction satisfy: -1.2 < R14 / fy < -1.

9. The projection lens according to claim 1, wherein: The radius of curvature R5 of the object side surface of the third lens and the radius of curvature R6 of the image side surface of the third lens satisfy: 2.4 < R5 / R6 < 3.5; the radius of curvature R7 of the object side surface of the fourth lens and the radius of curvature R8 of the image side surface of the fourth lens satisfy: -1.8 < R7 / R8 < -1.

3.

10. The projection lens according to claim 1, wherein: The radius of curvature R5 of the object side surface of the third lens and the radius of curvature R6 of the image side surface of the third lens satisfy: 0.3 < (R5 - R6) / (R5 + R6) < 0.7; the radius of curvature R7 of the object side surface of the fourth lens and the radius of curvature R8 of the image side surface of the fourth lens satisfy: 0 < (R7 + R8) / (R7 - R8) < 0.4.

Images