Projection lens

Abstract

The invention provides a projection lens, which sequentially comprises a first lens with positive focal power from a projection surface to an image source surface along an optical axis, a second lens with negative focal power, a third lens with positive focal power and a fourth lens with negative focal power from the projection surface to the image source surface, the surface of the projection side of the second lens is a convex 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 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 surface of the projection side of the fifth lens is a convex surface, and the surface of the image source side of the fifth lens is a convex surface; the surface of the projection side of the sixth lens is a convex surface, and the surface of the image source side of the sixth lens is a convex surface; a prism; and protective glass. The projection lens provided by the invention has one or more advantages of sunlight backflow prevention, large aperture, small distortion and the like.

Description

Technical Field

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

[0002] With the development of automotive intelligence, Head-Up Display (HUD) systems are becoming increasingly widely used. Their core relies on the Picture Generation Unit (PGU), and the projection lens, as a key component of the PGU, directly determines the image display effect and is crucial to the overall performance of the HUD. In automotive scenarios, sunlight backflow is a major challenge. Sunlight entering the lens from the opposite direction causes stray light interference, leading to image blurring, reduced contrast, and accelerated aging of internal components in the PGU, shortening the product's lifespan. To address this issue, the industry employs the Scharm lens principle in its projection lens design. By optimizing the tilt angle, stray light is suppressed, ensuring the HUD outputs a stable and clear image under complex lighting conditions, thus extending its lifespan. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a projection lens with the advantage of excellent image quality.

[0004] The technical solution adopted in this invention is as follows: A projection lens, comprising, along the optical axis from the projection surface to the image source surface, the following components in sequence: The first lens with positive optical power has a convex projection-side surface and a concave image-source-side surface; The second lens with negative optical power has a convex projection side surface and a concave image source side surface; The third lens with positive optical power has a convex projection side surface; The fourth lens with negative optical power has a concave projection side surface and a concave image source side surface. The fifth lens with positive optical power has a convex projection side surface and a convex image source side surface. The sixth lens with positive optical power has a convex projection side surface and a convex image source side surface. A prism includes an incident surface, a reflecting surface, and an exiting surface, all of which are planar. Light rays are incident on the prism from the incident surface along the optical axis, reflected by the reflecting surface, and exiting from the exiting surface. The reflecting surface forms an angle of 45° with the optical axis of the incident surface and the optical axis of the exiting surface, respectively. The protective glass has a flat surface on both the projection side and the image source side. The projection surface has a first tilt angle with the vertical plane; the protective glass and the image source surface have a second tilt angle with the horizontal plane. The total optical length TTL of the projection lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 3.5 < TTL / IH < 22.

[0005] Further preferably, the first tilt angle is 14° to 16°; the second tilt angle is 1° to 3°.

[0006] Further preferably, the clear aperture semi-diameter d4 of the image source side surface of the second lens and the curvature radius R4 of the image source side surface of the second lens satisfy: 1.4 < 2×d4 / R4 < 1.8.

[0007] Further preferably, the clear aperture semi-diameter d12 of the image source side surface of the sixth lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 0.9 < 2×d12 / IH < 1.7.

[0008] Further preferably, the combined focal length f123 of the first lens, the second lens and the third lens and the combined focal length f456 of the fourth lens, the fifth lens and the sixth lens satisfy: -145 < f123 / f456 < -4.2.

[0009] Further preferably, the distance BL from the image source side surface of the sixth lens of the projection lens to the image source plane on the optical axis and the effective focal length f of the projection lens satisfy: 0.9 < BL / f < 1.4.

[0010] Further preferably, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: -1.1 < f2 / f < -0.6; the curvature radius R3 of the projection side surface of the second lens and the effective focal length f of the projection lens satisfy: 0.5 < R3 / f < 0.9; 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: 0.22 < R4 / f < 0.36.

[0011] Further preferably, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: -0.9 < f4 / f < -0.5; the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 0.48 < f5 / f < 1.

[0012] Further preferably, the curvature radius R1 of the projection side surface of the first lens and the curvature radius R2 of the image source side surface of the first lens satisfy: -4 < (R1 + R2) / (R1 - R2) < -1.3.

[0013] Further preferably, 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: 2 < (R3 + R4) / (R3 - R4) < 2.8.

[0014] The projection lens provided by this invention, through specific surface shape matching and reasonable optical power distribution, can improve the imaging quality of the projection lens, reduce aberrations, and enhance the projection quality, giving the lens one or more advantages such as preventing sunlight backflow, large aperture, low distortion, high resolution, and low cost. Simultaneously, the tilt of the projection surface and image source surface gives the system a large depth of field, which is beneficial for lens assembly and improving the overall yield rate. Attached Figure Description

[0015] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the projection lens in Embodiment 1 of the present invention. Figure 1 .

[0016] Figure 2 This is a schematic diagram of the projection lens in Embodiment 1 of the present invention. Figure 2 .

[0017] Figure 3 This is a field curvature curve diagram of the projection lens in Embodiment 1 of the present invention.

[0018] Figure 4 This is an F-Tan (Theta) distortion curve of the projection lens in Embodiment 1 of the present invention.

[0019] Figure 5 This is a chromatic aberration curve of the projection lens in Embodiment 1 of the present invention.

[0020] Figure 6 This is a relative illumination curve of the projection lens in Embodiment 1 of the present invention.

[0021] Figure 7 This is a schematic diagram of the projection lens in Embodiment 2 of the present invention. Figure 1 .

[0022] Figure 8 This is a schematic diagram of the projection lens in Embodiment 2 of the present invention. Figure 2 .

[0023] Figure 9 This is a field curvature curve diagram of the projection lens in Embodiment 2 of the present invention.

[0024] Figure 10 This is the F-Tan (Theta) distortion curve of the projection lens in Embodiment 2 of the present invention.

[0025] Figure 11 This is a chromatic aberration curve of the projection lens in Embodiment 2 of the present invention.

[0026] Figure 12This is a relative illumination curve of the projection lens in Embodiment 2 of the present invention.

[0027] Figure 13 This is a schematic diagram of the projection lens in Embodiment 3 of the present invention. Figure 1 .

[0028] Figure 14 This is a schematic diagram of the projection lens in Embodiment 3 of the present invention. Figure 2 .

[0029] Figure 15 This is a field curvature curve diagram of the projection lens in Embodiment 3 of the present invention.

[0030] Figure 16 This is the F-Tan (Theta) distortion curve of the projection lens in Embodiment 3 of the present invention.

[0031] Figure 17 This is a chromatic aberration curve of the projection lens in Embodiment 3 of the present invention.

[0032] Figure 18 This is a relative illumination curve of the projection lens in Embodiment 3 of the present invention.

[0033] Figure 19 This is a schematic diagram of the projection lens in Embodiment 4 of the present invention. Figure 1 .

[0034] Figure 20 This is a schematic diagram of the projection lens in Embodiment 4 of the present invention. Figure 2 .

[0035] Figure 21 This is a field curvature curve diagram of the projection lens in Embodiment 4 of the present invention.

[0036] Figure 22 This is the F-Tan (Theta) distortion curve of the projection lens in Embodiment 4 of the present invention.

[0037] Figure 23 This is a chromatic aberration curve of the projection lens in Embodiment 4 of the present invention.

[0038] Figure 24 This is a relative illumination curve of the projection lens in Embodiment 4 of the present invention.

[0039] Figure 25 This is a schematic diagram of the projection lens in Embodiment 5 of the present invention. Figure 1 .

[0040] Figure 26 This is a schematic diagram of the projection lens in Embodiment 5 of the present invention. Figure 2 .

[0041] Figure 27This is a field curvature curve diagram of the projection lens in Embodiment 5 of the present invention.

[0042] Figure 28 This is an F-Tan (Theta) distortion curve of the projection lens in Embodiment 5 of the present invention.

[0043] Figure 29 This is a chromatic aberration curve of the projection lens in Embodiment 5 of the present invention.

[0044] Figure 30 This is a relative illumination curve of the projection lens in Embodiment 5 of the present invention.

[0045] Figure 31 This is a schematic diagram of the projection lens structure in Embodiment 6 of the present invention. Figure 1 .

[0046] Figure 32 This is a schematic diagram of the projection lens structure in Embodiment 6 of the present invention. Figure 2 .

[0047] Figure 33 This is a field curvature curve diagram of the projection lens in Embodiment 6 of the present invention.

[0048] Figure 34 This is an F-Tan (Theta) distortion curve of the projection lens in Embodiment 6 of the present invention.

[0049] Figure 35 This is a chromatic aberration curve of the projection lens in Embodiment 6 of the present invention.

[0050] Figure 36 This is a relative illumination curve of the projection lens in Embodiment 6 of the present invention.

[0051] Figure 37 This is a schematic diagram of the projection lens in Embodiment 7 of the present invention. Figure 1 .

[0052] Figure 38 This is a schematic diagram of the projection lens in Embodiment 7 of the present invention. Figure 2 .

[0053] Figure 39 This is a field curvature curve diagram of the projection lens in Embodiment 7 of the present invention.

[0054] Figure 40 This is the F-Tan (Theta) distortion curve of the projection lens in Embodiment 7 of the present invention.

[0055] Figure 41 This is a chromatic aberration curve of the projection lens in Embodiment 7 of the present invention.

[0056] Figure 42 This is a relative illumination curve of the projection lens in Embodiment 7 of the present invention.

[0057] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0058] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of embodiments of this application and are not intended to limit the scope of this 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.

[0059] It should be noted that in this specification, the terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of the invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0060] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not strictly to scale.

[0061] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the subject is called the object-side surface of the lens, and the surface of each lens closest to the imaging plane is called the image-side surface of the lens.

[0062] It should also be understood that the terms "comprising," "including," "having," "containing," 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. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features, not individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0063] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formal sense unless expressly so specified herein.

[0064] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0065] This invention provides a projection lens, which consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a prism, and a protective glass, arranged sequentially along the optical axis from the projection surface to the image source surface.

[0066] Specifically, the first lens may have positive optical power, its projection-side surface may be convex, and its image-source-side surface may be concave. The second lens may have negative optical power, its projection-side surface may be convex, and its image-source-side surface may be concave. The third lens may have positive optical power, its projection-side surface may be convex, and its image-source-side surface may be either concave or convex. The fourth lens may have negative optical power, its projection-side surface may be concave, and its image-source-side surface may be concave. The fifth lens may have positive optical power, its projection-side surface may be convex, and its image-source-side surface may be convex. The sixth lens may have positive optical power, its projection-side surface may be convex, and its image-source-side surface may be convex.

[0067] A prism can be a right-angled triangular prism, comprising an incident surface, a reflecting surface, and an exit surface; all three surfaces are planes. The reflecting surface of the prism forms a 45° angle with the optical axes of the incident and exit surfaces. It can be understood that the incident surface faces the projection plane, and the exit surface faces the image source plane. Light rays enter the prism from the incident surface, are reflected by the reflecting surface, and exit from the exit surface, with an angle of 90° between the incident and exit surfaces. Using a prism can change the direction of the light path, bending it so that the direction of the incident light rays is perpendicular to the arrangement of the multiple lenses, thus reducing the overall thickness of the optical system.

[0068] The protective glass has flat surfaces on both the projection side and the image source side. It protects the projection lens, preventing damage to the image sensor and improving the lens's impact and scratch resistance.

[0069] In some embodiments, the fourth lens and the fifth lens can be glued together to form a glued lens group with optical power, which can effectively correct the chromatic aberration of the projection lens, reduce the eccentricity sensitivity of the projection lens, balance the aberration of the projection lens, and improve the imaging quality of the projection lens; it can also reduce the assembly sensitivity of the projection lens, thereby reducing the processing difficulty of the projection lens and improving the assembly yield of the projection lens.

[0070] In some embodiments, the projection lens may further include an aperture, and the aperture may be located between the third lens and the fourth lens. It can be understood that the aperture is used to limit the amount of incident light to change the brightness of the imaging.

[0071] In some embodiments, the projection plane has a first inclination angle with respect to the vertical plane, and the first inclination angle is 14°-16°; the protective glass and the image source plane have a second inclination angle with respect to the horizontal plane, and the second inclination angle is 1°-3°. It can be understood that the projection plane is inclined with respect to the first lens; the protective glass and the image source plane are inclined with respect to the prism.

[0072] In some embodiments, the total optical length TTL of the projection lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 3.5 < TTL / IH < 22. Meeting the above range can better achieve the miniaturization of the lens, and at the same time ensure that the lens has a larger image plane under the same total length to achieve high-definition projection imaging.

[0073] In some embodiments, the clear aperture radius d4 of the image source side surface of the second lens and the radius of curvature R4 of the image source side surface of the second lens satisfy: 1.4 < 2×d4 / R4 < 1.8. Meeting the above range can avoid the lens being super hemispherical and greatly reduce the processing difficulty of the second lens.

[0074] In some embodiments, the clear aperture radius d12 of the image source side surface of the sixth lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 0.9 < 2×d12 / IH < 1.7. Meeting the above range is beneficial for the chief ray of the edge field to emerge parallel to the image source plane, which is beneficial for achieving a small CRA.

[0075] In some embodiments, the combined focal length f123 of the first lens, the second lens and the third lens and the combined focal length f456 of the fourth lens, the fifth lens and the sixth lens satisfy: -145 < f123 / f456 < -4.2. Meeting the above range, the refractive powers of the front and rear lens groups of the aperture cooperate with each other to achieve the purpose of correcting aberration, field curvature and distortion, and improve the imaging quality of the projection lens.

[0076] In some embodiments, the distance BL from the image source side surface of the sixth lens of the projection lens to the image source plane on the optical axis and the effective focal length f of the projection lens satisfy: 0.9 < BL / f < 1.4. Meeting the above range is beneficial to achieving a balance between obtaining good imaging quality and easy assembly. While ensuring the imaging quality of the projection lens, it avoids interference between the lens and other components, and reduces the assembly process difficulty of the camera module.

[0077] In some embodiments, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: -1.1 < f2 / f < -0.6; 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: 0.5 < R3 / f < 0.9; 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: 0.22 < R4 / f < 0.36. Meeting the above range, the second lens has a negative focal length and a relatively small focal length, which can adjust the full-field beam, deflect the large-field beam, and turn the beam to the relay lens group, thus facilitating the realization of a large field of view of the projection lens. At the same time, the second lens is overall in the shape of a meniscus with the concave surface facing the projection side, which can slow down the trend of marginal rays and is beneficial to improving the imaging quality of the projection lens.

[0078] In some embodiments, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: -0.9 < f4 / f < -0.5; the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 0.4 < f5 / f < 1. Meeting the above range, the fourth lens and the fifth lens are cemented to form a cemented lens. The two can have opposite optical powers, and the fourth lens has a strong negative optical power, and the fifth lens has a strong positive optical power, so that various aberrations of the projection lens are fully corrected, the resolution can be improved, and high resolution can be achieved.

[0079] In some embodiments, the radius of curvature R1 of the projection side surface of the first lens and the radius of curvature R2 of the image source side surface of the first lens satisfy: -4 < (R1 + R2) / (R*1 - R2) < -1.3. Meeting the above range, the radii of curvature of the projection side surface and the image source side surface of the first lens near the optical axis are reasonably controlled, which is beneficial to controlling the shape of the first lens, correcting the aberrations generated by itself, and improving the imaging quality.

[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: 2 < (R3 + R4) / (R3 - R4) < 2.8. Meeting the above range is beneficial to the convergence of light rays in the wide-angle field of view, thereby adjusting the trend of marginal beams and ensuring that the projection lens has a large field angle.

[0081] In some embodiments, the combined focal length f123 of the first lens, the second lens, and the third lens and the effective focal length f of the projection lens satisfy: -90 < f123 / f < -2.8. Meeting the above range, by reasonably distributing the optical power of the first lens to the third lens, the deflection angle of the light rays at the front end of the lens is reduced, and the generation of various off-axis aberrations is reduced.

[0082] In some embodiments, the combined focal length f456 of the fourth lens, the fifth lens, and the sixth lens and the effective focal length f of the projection lens satisfy: 0.55 < f456 / f < 0.77. Meeting the above range, by reasonably distributing the optical power of the fourth lens to the sixth lens, the focal length of the projection lens is balanced, the correction ability of various aberrations at the rear end of the lens is improved, and the imaging quality of the projection lens is enhanced.

[0083] In some embodiments, the combined focal length f45 of the fourth lens and the fifth lens and the effective focal length f of the projection lens satisfy: 1.3 < f45 / f < 3.3. Meeting the above range, reasonably limiting the proportion of the optical power of the cemented lens composed of the fourth lens and the fifth lens is beneficial to reducing chromatic aberration and spherical aberration and improving the imaging quality.

[0084] In some embodiments, the clear aperture radius d1 of the projection side surface of the first lens and the clear aperture radius d12 of the image source side surface of the sixth lens satisfy: 1.1 < d1 / d12 < 1.8. Meeting the above range, by reasonably setting the ratio of the apertures of the first and last lenses, the lens can have a smaller head size while having a larger imaging surface, and can better meet the balance of miniaturization and high pixels.

[0085] In some embodiments, the sagittal height SAG4 of the clear aperture of the image source side surface of the second lens, the sagittal height SAG3 of the clear aperture of the projection side surface of the second lens, and the central thickness CT2 of the second lens satisfy: -0.33 < (SAG4 - SAG3) / CT2 < 0.2. Meeting the above range, the degree of central depression of the second lens can be restricted, and the difficulty of aberration correction in the marginal field of view can be reduced.

[0086] In some embodiments, the sagittal height SAG8 of the clear aperture of the image source side surface of the fourth lens, the sagittal height SAG7 of the clear aperture of the projection side surface of the fourth lens, and the central thickness CT4 of the fourth lens satisfy: 0.25 < (SAG8 - SAG7) / CT4 < 1.6. Meeting the above range, the surface shape of the projection surface of the fourth lens can be controlled, which is beneficial to the manufacturing and molding of the fourth lens, reduces the rejection rate. In addition, it can also prevent the surface shape from being too curved and complex, making the system field curvature tend to be balanced.

[0087] In some embodiments, the sagittal height SAG12 of the image source side surface of the sixth lens, the sagittal height SAG11 of the projection side surface of the sixth lens, and the central thickness CT6 of the sixth lens satisfy: -0.7 < (SAG12 - SAG11) / CT6 < -0.33. Meeting the above range, by controlling the relationship between the height difference of the sagittal heights of the image source side surface and the projection side surface of the sixth lens and the central thickness of the sixth lens, it is beneficial to correct the coma of the off-axis field of view and improve the imaging quality of the off-axis field of view of the projection lens.

[0088] In some embodiments, the total optical length TTL of the projection lens and the effective focal length f of the projection lens satisfy: 2.5 < TTL / f < 9. Meeting the above range can effectively limit the length of the lens and is beneficial to the miniaturization of the projection lens.

[0089] In some embodiments, the true image height IH corresponding to the maximum field of view angle of the projection lens, the effective focal length f of the projection lens, and the maximum field of view angle FOV of the projection lens satisfy: 0.9 < (IH / 2) / (f × tan(FOV / 2)) < 1.1. Meeting the above range indicates that the optical distortion of the projection lens is well controlled, improving the resolution of the projection lens. At the same time, it meets the special distortion specifications, ensuring that the edge field of view occupies a larger proportion in the entire imaging picture and making the imaging of the edge of the field of view clearer.

[0090] In some embodiments, the maximum field of view angle FOV of the projection lens and the f-number Fno of the projection lens satisfy: 8.5° < FOV / Fno < 19°. Meeting the above range is beneficial to increasing the light input of the lens, enabling the lens to achieve high-definition imaging in a dim environment.

[0091] 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: 0.9 < IH / EPD < 1.9. Meeting the above range, while having a large image plane, the projection lens can also ensure sufficient image plane brightness in the edge field of view, preventing the occurrence of vignetting and thus improving the imaging quality.

[0092] In some embodiments, the true image height IH corresponding to the maximum field of view angle of the projection lens and the effective focal length f of the projection lens satisfy: 0.4 < IH / f < 0.8. Meeting the above range can achieve a larger field of view angle and imaging range, and can achieve the characteristics of a large image plane while ensuring the depth of field of the projection lens, thereby improving the imaging quality of the optical system.

[0093] In some embodiments, the total optical length TTL of the projection lens, the true image height IH corresponding to the maximum field angle of the projection lens, and the maximum field angle FOV of the projection lens satisfy: 0.05 / ° < TTL / IH / FOV < 0.9 / °. Meeting the above range can achieve a balance among large image height, long focal length, and miniaturization, and improve the imaging quality of the projection lens.

[0094] In some embodiments, the effective focal length f of the projection lens, the maximum field angle FOV of the projection lens, and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 48° < f × FOV / IH < 60°. Meeting the above range is conducive to achieving the balance between the field angle of the projection lens and large target surface imaging by reasonably restricting the relationship among the focal length, field angle, and image height of the projection lens, and better meeting the usage requirements of high image quality projection of the projection lens.

[0095] In some embodiments, the sum of the central thicknesses ΣCT of the six lenses and the total optical length TTL of the projection lens satisfy: 0.1 < ΣCT / TTL < 0.45. Meeting the above range can effectively compress the total length of the projection lens, and is conducive to the structural design and production process of the projection lens.

[0096] In some embodiments, the clear aperture radius d1 on the projection side surface of the first lens, the true image height IH corresponding to the maximum field angle of the projection lens, and the maximum field angle FOV of the projection lens satisfy: 1.7 < d1 / IH / tan(FOV / 2) < 5.5. Meeting the above range can ensure the balance between the size of the projection lens, the field angle, and the image plane.

[0097] In some embodiments, the central thickness CT1 of the first lens and the central thickness CT2 of the second lens satisfy: 0.5 < CT1 / CT2 < 1.9. Meeting the above range, by reasonably configuring the ratio of the central thicknesses of the first lens and the second lens, the first lens and the second lens can regulate each other, and then maintain the characteristics of miniaturization of the optical system.

[0098] In some embodiments, the central thickness CT4 of the fourth lens and the central thickness CT5 of the fifth lens satisfy: 0.15 < CT4 / CT5 < 0.95. Meeting the above range can reduce the sensitivity of system performance, while ensuring the lens processing performance and assembly stability, and improving the assembly yield.

[0099] In some embodiments, the focal length f2 of the second lens and the focal length f3 of the third lens satisfy: -0.3 < f2 / f3 < 0. Meeting the above range, by reasonably setting the focal lengths of the second and third lenses, better light convergence can be achieved, shortening the distance for light to enter the next lens, which is conducive to the miniaturization of the projection lens.

[0100] In some embodiments, the focal length f5 of the fifth lens and the focal length f6 of the sixth lens satisfy: 0.35 < f5 / f6 < 0.95. Meeting the above range is beneficial to expanding the width of the light beam. After the light passes through the fifth lens and the sixth lens and is refracted, the light beam width of the projection lens is larger, and then it can be fully transmitted to the high-pixel image source surface, enabling the projection lens to obtain a wider field of view range. At the same time, it is also beneficial for the projection lens to achieve high-pixel and large-image-plane imaging.

[0101] In some embodiments, the focal length f1 of the first lens and the effective focal length f of the projection lens satisfy: 1.3 < f1 / f < 2.5; the radius of curvature R1 of the projection side surface of the first lens and the effective focal length f of the projection lens satisfy: 0.65 < R1 / f < 1.8; the radius of curvature R2 of the image source side surface of the first lens and the effective focal length f of the projection lens satisfy: 1.1 < R2 / f < 12. Meeting the above range, the first lens expands the field angle range of the projection lens and is beneficial to reducing the sensitivity of the projection lens, realizing the miniaturized design of the projection lens. At the same time, the first lens is a meniscus positive lens. By reasonably configuring the ratio of the radius of curvature of the projection side surface and the image source side surface of the first lens to the effective focal length of the projection lens, the light transmission amount of the projection lens can be increased, effectively expanding the field of view range of the projection lens.

[0102] In some embodiments, the focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: 2.6 < f3 / f < 14; the radius of curvature R5 of the projection side surface of the third lens and the effective focal length f of the projection lens satisfy: 0.25 < R5 / f < 5.5; the radius of curvature R6 of the image source side surface of the third lens and the effective focal length f of the projection lens satisfy: -5.5 < R6 / f < 0.5. Meeting the above range, the third lens is a positive lens, which transmits the light beam to the final imaging lens group and realizes aberration complementarity with the front and rear optical systems, thereby achieving high imaging quality of the projection lens. At the same time, the third lens can adjust the trend of the light, and also helps to reduce the aperture of the subsequent lens, thereby realizing cost reduction.

[0103] In some embodiments, the radius of curvature R7 of the projection side surface of the fourth lens and the effective focal length f of the projection lens satisfy: -1.15 < R7 / f < -0.7; the radius of curvature R8 of the image source side surface of the fourth lens and the effective focal length f of the projection lens satisfy: 0.8 < R8 / f < 1.9. Meeting the above range, the fourth lens can have appropriate optical power and surface shape, which is beneficial to balancing the astigmatism and field curvature of the projection lens and improving the imaging quality of the projection lens.

[0104] In some embodiments, the radius of curvature R9 of the projection side surface of the fifth lens and the effective focal length f of the projection lens satisfy: 0.8 < R9 / f < 1.9; the radius of curvature R10 of the image source side surface of the fifth lens and the effective focal length f of the projection lens satisfy: -0.6 < R10 / f < -0.4. Meeting the above ranges, the fifth lens is a biconvex lens, which is beneficial for gently converging and converging the front beam, beneficial for improving the imaging quality of the projection lens, and reducing the aperture of the rear sixth lens, thereby achieving miniaturization.

[0105] In some embodiments, the focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 0.85 < f6 / f < 1.55; the radius of curvature R11 of the projection side surface of the sixth lens and the effective focal length f of the projection lens satisfy: 1.1 < R11 / f < 3.4; the radius of curvature R12 of the image source side surface of the sixth lens and the effective focal length f of the projection lens satisfy: -1.5 < R12 / f < -0.8. Meeting the above ranges, the sixth lens has a positive optical power, which is beneficial for converging light, reducing the light deflection angle, making the light trend transition smoothly, and improving the projection quality of the projection lens. At the same time, effectively converging and converging the beam helps to achieve a small CRA and high imaging quality of the projection lens.

[0106] In some embodiments, the radius of curvature R11 of the projection side surface of the sixth lens and the radius of curvature R12 of the image source side surface of the sixth lens satisfy: -0.1 < (R11 + R12) / (R11 - R12) < 0.5. Meeting the above ranges is beneficial for suppressing the angle of the marginal field incident on the image source surface, effectively transmitting more beams to the image source surface, and at the same time being able to balance the field curvature and spherical aberration of the projection lens, and improving the imaging quality of the projection lens.

[0107] In some embodiments, the projection lens satisfies the following conditional expressions: 15.4mm < f < 25.9mm; 22.5° < FOV < 40.3°; 6.5mm < EPD < 10.8mm; 43.7mm < TTL < 212.6mm; 2.1 < Fno < 2.5; 1o.1mm < IH < 11.6mm; 2.2° < CRA < 11.1°; 20.1mm < BL < 28.6mm. In the above conditional expressions, f represents the effective focal length of the projection lens, TTL represents the total optical length of the projection lens, Fno represents the aperture value of the projection lens, CRA represents the principal ray incident angle at the maximum image height of the projection lens, IH represents the true image height corresponding to the maximum field angle of the projection lens, FOV represents the maximum field angle of the projection lens, EPD represents the entrance pupil diameter of the projection lens, and BL represents the distance from the image source side surface of the sixth lens of the projection lens to the image source surface on the optical axis. Meeting the above ranges, the projection lens has at least one or more advantages such as a large aperture, small distortion, and high resolution.

[0108] In some embodiments, the lens material in the projection lens provided by the present invention can be glass or plastic. When the lens is made of plastic, production costs can be effectively reduced. Conversely, when the lens is made of glass, the low dispersion characteristic of glass itself can effectively correct geometric chromatic aberration of the optical system. More specifically, all six lenses with optical power in the present invention are made of glass. The all-glass structure improves the stability of the lens under high and low temperature conditions.

[0109] In some embodiments, the first, second, third, fourth, fifth, and sixth lenses can be spherical or aspherical lenses. Compared to spherical structures, aspherical structures can effectively reduce aberrations in the optical system, thereby reducing the number of lenses and their size, and better achieving lens miniaturization. More specifically, all six lenses with optical power in this invention are spherical lenses.

[0110] The present invention will be further described below with reference to several embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the projection lens are different; for specific differences, please refer to the parameter tables of each embodiment. The following embodiments are merely preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments. Any changes, substitutions, combinations, or simplifications made without departing from the innovative points of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention.

[0111] Example 1 Please see Figure 1 and Figure 2 The diagram shows a schematic of the projection lens 100 provided in Embodiment 1 of the present invention. The projection lens 100 includes, along the optical axis from the projection surface S0 to the image source surface S16, the following components in sequence: a first lens L1, a second lens L2, a third lens L3, an aperture ST, a fourth lens L4, a fifth lens L5, a sixth lens L6, a prism L7, and a protective glass G1.

[0112] The projection surface S0 has a first tilt angle of 15° with the vertical plane; the protective glass G1 and the image source surface S16 have a second tilt angle of 2° with the horizontal plane. It can be understood that the projection surface is tilted relative to the first lens L1; the protective glass G1 and the image source surface S16 are tilted relative to the prism L7.

[0113] Among them, the first lens L1 has positive optical power, its projection side surface S1 is convex, and its image source side surface S2 is concave. The second lens L2 has negative optical power, its projection side surface S3 is convex, and its image source side surface S4 is concave. The third lens L3 has positive optical power, its projection side surface S5 is convex, and its image source side surface S6 is concave. The fourth lens L4 has negative optical power, its projection side surface S7 is concave, and its image source side surface is concave. The fifth lens L5 has positive optical power, its projection side surface is convex, and its image source side surface S9 is convex. The fourth lens L4 and the fifth lens L5 form a cemented lens group with optical power, that is, the cemented surface of the image source side surface of the fourth lens L4 and the projection side surface of the fifth lens L5 is S8. The sixth lens L6 has positive optical power, its projection side surface S10 is convex, and its image source side surface S11 is convex. Prism L7 can be a right-angled triangular prism, comprising an incident surface S12, a reflecting surface R0, and an exit surface S13; all three surfaces are planes. The reflecting surface of the prism forms a 45° angle with the optical axes of the incident and exit surfaces. It can be understood that the incident surface S12 faces the projection plane, and the exit surface S13 faces the image source plane. Light rays enter the prism from the incident surface, are reflected by the reflecting surface, and exit from the exit surface, with an angle of 90° between the incident and exit surfaces.

[0114] The projection-side surface S14 and the image source-side surface S15 of the protective glass G1 are both planar. Image source plane S16 is a plane.

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

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

[0117] Table 1 In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, lateral chromatic aberration curve, and relative illuminance curve of the projection lens 100 are respectively as follows: Figures 3 to 6 As shown.

[0118] Figure 3 The field curvature curve of Embodiment 1 is shown, which represents the degree of curvature of light of different wavelengths in the meridional and sagittal image planes. The horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field of view (unit: °). As can be seen from the figure, the field curvature of the meridional and sagittal image planes is controlled within -0.05 mm to 0.1 mm, indicating that the projection lens 100 can effectively correct the field curvature.

[0119] Figure 4The F-Tan (Theta) distortion curve of Example 1 is shown, which represents the F-Tan (Theta) distortion at different image heights on the imaging plane. The horizontal axis represents the distortion value (unit: %), and the vertical axis represents the half field of view (unit: °). As can be seen from the figure, the F-Tan (Theta) distortion of the projection lens 100 is controlled within -2% to 0%, indicating that the distortion of the projection lens 100 is well corrected.

[0120] Figure 5 The diagram shows the transverse chromatic aberration curves for Example 1, representing the chromatic aberration of each wavelength relative to the center wavelength (0.530 μm) at different image heights on the imaging plane. The horizontal axis represents the transverse chromatic aberration value of each wavelength relative to the center wavelength (unit: μm), and the vertical axis represents the normalized field of view. As can be seen from the diagram, the transverse chromatic aberration of the longest and shortest wavelengths is controlled within -1 μm to 3 μm, indicating that the projection lens 100 can effectively correct transverse chromatic aberration.

[0121] Figure 6 The relative illumination curve of Example 1 is shown, which represents the relative illumination value at different field-of-view angles on the imaging plane. The horizontal axis represents the half-field-of-view angle (unit: °), and the vertical axis represents the relative illumination (unit: %). As can be seen from the figure, the relative illumination value of the projection lens is still greater than 95% at the maximum half-field-of-view angle, indicating that the projection lens 100 has good relative illumination.

[0122] Example 2 Please see Figure 7 and Figure 8 The diagram shown is a schematic diagram of the projection lens 200 provided in Embodiment 2 of the present invention. The main difference between this embodiment and Embodiment 1 is that the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0123] The relevant parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2.

[0124] Table 2 In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, lateral chromatic aberration curve, and relative illuminance curve of the projection lens 200 are respectively as follows: Figures 9 to 12 As shown.

[0125] from Figure 9 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within -0.1mm to 0mm, indicating that the projection lens 200 can effectively correct the field curvature.

[0126] from Figure 10As can be seen, the F-Tan (Theta) distortion of the projection lens 200 is controlled within -2% to 0%, indicating that the distortion of the projection lens 200 has been well corrected.

[0127] from Figure 11 As can be seen, the vertical chromatic difference between the longest and shortest wavelengths is controlled within -1μm to 3μm, indicating that the projection lens 200 can effectively correct the vertical chromatic difference.

[0128] from Figure 12 As can be seen, the relative illumination value of the projection lens is still greater than 95% at the maximum half field of view, indicating that the projection lens 200 has good relative illumination.

[0129] Example 3 Please see Figure 13 and Figure 14 The diagram shows a schematic of the projection lens 300 provided in Embodiment 3 of the present invention. The main difference between this embodiment and Embodiment 1 is that the protective glass G1 and the image source surface S16 have a second tilt angle with the horizontal plane, and the second tilt angle is 1.7°; the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0130] The relevant parameters of each lens in the projection lens 300 in Example 3 are shown in Table 3.

[0131] Table 3 In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, lateral chromatic aberration curve, and relative illuminance curve of the projection lens 300 are respectively as follows: Figures 15 to 18 As shown.

[0132] from Figure 15 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within -0.1mm to 0mm, indicating that the projection lens 300 can effectively correct the field curvature.

[0133] from Figure 16 As can be seen, the F-Tan (Theta) distortion of the projection lens 300 is controlled within -2% to 0%, indicating that the distortion of the projection lens 300 has been well corrected.

[0134] from Figure 17 As can be seen, the vertical chromatic difference between the longest and shortest wavelengths is controlled within -1μm to 3μm, indicating that the projection lens 300 can effectively correct the vertical chromatic difference.

[0135] from Figure 18As can be seen, the relative illuminance value of the projection lens is still greater than 90% at the maximum half field of view, indicating that the projection lens 300 has good relative illuminance.

[0136] Example 4 Please see Figure 19 and Figure 20 The diagram shows a schematic of the projection lens 400 provided in Embodiment 4 of the present invention. The main difference between this embodiment and Embodiment 1 is that the protective glass G1 and the image source surface S16 have a second tilt angle with the horizontal plane, and the second tilt angle is 1.43°; the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0137] The relevant parameters of each lens in the projection lens 400 in Example 4 are shown in Table 4.

[0138] Table 4 In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, lateral chromatic aberration curve, and relative illuminance curve of the projection lens 400 are respectively as follows: Figures 21 to 24 As shown.

[0139] from Figure 21 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within -0.15mm to 0mm, indicating that the projection lens 400 can effectively correct the field curvature.

[0140] from Figure 22 As can be seen, the F-Tan (Theta) distortion of the projection lens 400 is controlled within -2% to 0%, indicating that the distortion of the projection lens 400 has been well corrected.

[0141] from Figure 23 As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within -2μm to 4μm, indicating that the projection lens 400 can effectively correct the chromatic aberration.

[0142] from Figure 24 As can be seen, the relative illuminance value of the projection lens is still greater than 90% at the maximum half field of view, indicating that the projection lens 400 has good relative illuminance.

[0143] Example 5 Please see Figure 25 and Figure 26The diagram shows a schematic of the projection lens 500 provided in Embodiment 5 of the present invention. The main difference between this embodiment and Embodiment 1 is that: the image source side surface S6 of the third lens L3 is convex; the protective glass G1, the image source surface S16 and the horizontal plane have a second tilt angle of 1.5404°; and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0144] The relevant parameters of each lens in the projection lens 500 in Example 5 are shown in Table 5.

[0145] Table 5 In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, lateral chromatic aberration curve, and relative illuminance curve of the projection lens 500 are respectively as follows: Figures 27 to 30 As shown.

[0146] from Figure 27 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within -0.2mm to 0mm, indicating that the projection lens 500 can effectively correct the field curvature.

[0147] from Figure 28 As can be seen, the F-Tan (Theta) distortion of the projection lens 500 is controlled within -2% to 0%, indicating that the distortion of the projection lens 500 has been well corrected.

[0148] from Figure 29 As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within -1μm to 4μm, indicating that the projection lens 500 can effectively correct the chromatic aberration.

[0149] from Figure 30 As can be seen, the relative illumination value of the projection lens is still greater than 90% at the maximum half field of view, indicating that the projection lens 500 has good relative illumination.

[0150] Example 6 Please see Figure 31 and Figure 32 The diagram shows a schematic of the projection lens 600 provided in Embodiment 6 of the present invention. The main difference between this embodiment and Embodiment 1 is that: the image source side surface S6 of the third lens L3 is convex; the protective glass G1, the image source surface S16 and the horizontal plane have a second tilt angle of 1.43°; and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0151] The relevant parameters of each lens in the projection lens 600 in Example 6 are shown in Table 6.

[0152] Table 6 In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, lateral chromatic aberration curve, and relative illuminance curve of the projection lens 600 are respectively as follows: Figures 33 to 36 As shown.

[0153] from Figure 33 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within -0.15mm to 0mm, indicating that the projection lens 600 can effectively correct the field curvature.

[0154] from Figure 34 As can be seen, the F-Tan (Theta) distortion of the projection lens 600 is controlled within -2% to 0%, indicating that the distortion of the projection lens 600 is well corrected.

[0155] from Figure 35 As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within -2μm to 5μm, indicating that the projection lens 600 can effectively correct the chromatic aberration.

[0156] from Figure 36 As can be seen, the relative illumination value of the projection lens is still greater than 90% at the maximum half field of view, indicating that the projection lens 600 has good relative illumination.

[0157] Example 7 Please see Figure 37 and Figure 38 The diagram shows a schematic of the projection lens 700 provided in Embodiment 7 of the present invention. The main difference between this embodiment and Embodiment 1 is that: the image source side surface S6 of the third lens L3 is a convex surface; the protective glass G1, the image source surface S16 and the horizontal plane have a second tilt angle of 1.43°; and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0158] The relevant parameters of each lens in the projection lens 700 in Example 7 are shown in Table 7.

[0159] Table 7 In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, transverse chromatic aberration curve, and relative illuminance curve of the projection lens 700 are respectively as follows: Figures 39 to 42 As shown.

[0160] from Figure 39 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within -0.15mm to 0mm, indicating that the projection lens 700 can effectively correct the field curvature.

[0161] from Figure 40 As can be seen, the F-Tan (Theta) distortion of the projection lens 700 is controlled within -2% to 0%, indicating that the distortion of the projection lens 700 has been well corrected.

[0162] from Figure 41 As can be seen, the vertical chromatic difference between the longest and shortest wavelengths is controlled within 0μm~3μm, indicating that the projection lens 700 can effectively correct the vertical chromatic difference.

[0163] from Figure 42 As can be seen, the relative illumination value of the projection lens is still greater than 90% at the maximum half field of view, indicating that the projection lens 700 has good relative illumination.

[0164] Please refer to Tables 8-1 and 8-2 for 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 principal ray incident angle CRA at the maximum image height, the true image height IH corresponding to the maximum field of view, the maximum field of view FOV, the entrance pupil diameter EPD, the distance BL from the image source side surface of the sixth lens to the image source surface on the optical axis, and the values ​​corresponding to each conditional expression in each embodiment.

[0165] Table 8-1 Table 8-2 In summary, the projection lens provided by this invention, through specific surface shape matching and reasonable optical power allocation, can improve the imaging quality of the projection lens, reduce aberrations, and enhance the projection quality, giving the lens one or more advantages such as preventing sunlight backflow, large aperture, low distortion, high resolution, and low cost. Simultaneously, the tilt of the projection surface and image source surface gives the system a large depth of field, which is beneficial for lens assembly and improving the overall yield rate.

[0166] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions 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 one or more embodiments or examples.

[0167] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A projection lens characterized in that, In order from the projection surface to the image source surface along the optical axis, there are sequentially arranged: a first lens with positive focal power, a convex projection side surface and a concave image source side surface; a second lens with negative focal power, a convex projection side surface and a concave image source side surface; a third lens with positive focal power, a convex projection side surface; a fourth lens with negative focal power, a concave projection side surface and a concave image source side surface; a fifth lens with positive focal power, a convex projection side surface and a convex image source side surface; a sixth lens with positive focal power, a convex projection side surface and a convex image source side surface; a prism including an incident surface, a reflection surface and an exit surface, all of which are flat, light rays enter the prism from the incident surface, are reflected by the reflection surface and exit from the exit surface, the reflection surface forms a 45° angle with the optical axis of the incident surface and the optical axis of the exit surface; the projection surface has a first inclination angle with a vertical plane; the image source surface has a second inclination angle with a horizontal plane; the total length TTL of the projection lens and the real image height IH corresponding to the maximum field angle of the projection lens satisfy 3.5 < TTL / IH < 22.

2. The projection lens according to claim 1, characterized in that The first inclination angle is 14°-16°, and the second inclination angle is 1°-3°.

3. The projection lens of claim 1, wherein The image source side surface half aperture radius d4 of the second lens and the image source side surface curvature radius R4 of the second lens satisfy 1.4 < 2×d4 / R4 < 1.

8.

4. The projection lens of claim 1, wherein The image source side surface half aperture radius d12 of the sixth lens and the real image height IH corresponding to the maximum field angle of the projection lens satisfy 0.9 < 2×d12 / IH < 1.

7.

5. The projection lens of claim 1, wherein The combined focal length f123 of the first lens, the second lens and the third lens and the combined focal length f456 of the fourth lens, the fifth lens and the sixth lens satisfy -145 < f123 / f456 < -4.

2.

6. The projection lens of claim 1, wherein, The distance BL on the optical axis from the image source side surface of the sixth lens of the projection lens to the image source surface and the effective focal length f of the projection lens satisfy 0.9 < BL / f < 1.

4.

7. The projection lens of claim 1, wherein The focal length f2 of the second lens and the effective focal length f of the projection lens satisfy -1.1 < f2 / f < -0.6, the projection side surface curvature radius R3 of the second lens and the effective focal length f of the projection lens satisfy 0.5 < R3 / f < 0.9, and the image source side surface curvature radius R4 of the second lens and the effective focal length f of the projection lens satisfy 0.22 < R4 / f < 0.

36.

8. The projection lens of claim 1, wherein, The focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy -0.9 < f4 / f < -0.5, and the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy 0.48 < f5 / f < 1.

9. The projection lens of claim 1, wherein, The projection side surface curvature radius R1 of the first lens and the image source side surface curvature radius R2 of the first lens satisfy -4 < (R1+R2) / (R1-R2) < -1.

3.

10. The projection lens of 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: 2 < (R3+R4) / (R3-R4) < 2.8.

Images