projection lens

Abstract

The application provides a projection lens, which comprises six lenses in sequence along an optical axis from a projection surface to an image source surface, wherein the first lens has negative optical power, and the image source side surface is a concave surface; the second lens has positive optical power, and the projection side surface is a concave surface, and the image source side surface is a convex surface; the third lens has optical power, and the projection side surface is a concave surface, and the image source side surface is a convex surface; the fourth lens has negative optical power, and the projection side surface and the image source side surface are both concave surfaces; the fifth lens has positive optical power, and the projection side surface and the image source side surface are both convex surfaces; and the sixth lens has positive optical power, and the image source side surface is a convex surface. The application improves the imaging quality of the projection lens, reduces aberration, and improves the projection quality of the projection lens by reasonably configuring the surface types of the lenses and reasonably matching the optical powers.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of imaging lenses, in particular to a projection lens. BACKGROUND

[0002] With the increasing demand for driving experience, vehicle application type projection lenses are increasingly used in intelligent driving, and vehicle projection lenses are continuously improving in the automotive industry. The head-up display (HUD) is also known as the automotive head-up display system, which uses optical reflection principles to project driving assistance information, navigation information, inspection control information, and ADAS information on the windshield or about 2m in front of the engine cover tip. It can also display warning information from various driving assistance systems, such as lane departure warnings, pedestrian avoidance warnings from night vision assistance systems with pedestrian recognition, etc., to avoid drivers frequently looking down at the instrument or vehicle screen during driving, which plays a good auxiliary role for driving safety.

[0003] However, the projection lenses for vehicle HUD on the market have the defects that the projected patterns are prone to dark corners, the brightness at the projection surface is not enough, and the patterns are not clear, which cannot meet the use requirements. SUMMARY

[0004] To solve the above problems, the present application aims to provide a projection lens with high imaging quality.

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

[0006] a first lens with negative optical power, the image source side surface of which is a concave surface;

[0007] a second lens with positive optical power, the projection side surface of which is a concave surface, and the image source side surface of which is a convex surface;

[0008] a third lens with optical power, the projection side surface of which is a concave surface, and the image source side surface of which is a convex surface;

[0009] a fourth lens with negative optical power, both the projection side surface and the image source side surface of which are concave surfaces;

[0010] a fifth lens with positive optical power, both the projection side surface and the image source side surface of which are convex surfaces;

[0011] a sixth lens with positive optical power, the image source side surface of which is a convex surface;

[0012] The effective focal length f of the projection lens and the projection side surface radius of curvature R3 of the second lens satisfy: R3 / f<-4.1; the effective focal length f of the projection lens and the projection side surface radius of curvature R5 of the third lens satisfy: R5 / f<-0.5.

[0013] Further preferably, the chief ray angle of incidence CRA at the maximum image height of the projection lens satisfies: CRA<2.1°.

[0014] Further preferably, the effective focal length f of the projection lens and the maximum field of view FOV and the real image height IH corresponding to the maximum field of view satisfy: 0.95<(IH / 2) / (fxtan(FOV / 2))<1.05.

[0015] Further preferably, the effective focal length f of the projection lens and the back focal length BFL of the projection lens satisfy: BFL / f>1.8.

[0016] Further preferably, the effective focal length f of the projection lens and the focal length f2 of the second lens satisfy: 1.8<f2 / f<3.8.

[0017] Further preferably, the effective focal length f of the projection lens and the focal length f6 of the sixth lens satisfy: 1.3<f6 / f<3.1.

[0018] Further preferably, a diaphragm is arranged between the second lens and the third lens or between the third lens and the fourth lens, and the effective focal length f of the projection lens and the focal length fb6 of the lens group located after the diaphragm satisfy: 1<fb6 / f<2.3.

[0019] Further preferably, the effective focal length f of the projection lens and the image source side surface radius of curvature R6 of the third lens satisfy: -1<R6 / f<-0.3.

[0020] Further preferably, the projection side surface radius of curvature R3 of the second lens and the image source side surface radius of curvature R4 of the second lens satisfy: 0.3<(R3-R4) / (R3+R4)<1.

[0021] Further preferably, the projection side surface half-aperture radius d3 of the second lens and the projection side surface sag Sag3 of the second lens satisfy: -0.2<Sag3 / d3<0; the projection side surface half-aperture radius d5 of the third lens and the projection side surface sag Sag5 of the third lens satisfy: -0.5<Sag5 / d5<-0.1.

[0022] The projection lens provided by the present application improves the imaging quality of the projection lens, reduces aberration, improves the projection quality of the projection lens, and makes the lens have one or more advantages of small distortion, large aperture, large image surface, and high imaging quality. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the following drawings of which:

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

[0025] Figure 2 It is the F-Tanθ distortion curve of the projection lens in the embodiment 1 of the present application.

[0026] Figure 3 It is the MTF curve of the projection lens in the embodiment 1 of the present application.

[0027] Figure 4 It is the sagittal chromatic aberration curve of the projection lens in the embodiment 1 of the present application.

[0028] Figure 5 It is the relative illumination curve of the projection lens in the embodiment 1 of the present application.

[0029] Figure 6 It is a structural schematic diagram of the projection lens in the embodiment 2 of the present application.

[0030] Figure 7 It is the F-Tanθ distortion curve of the projection lens in the embodiment 2 of the present application.

[0031] Figure 8 It is the MTF curve of the projection lens in the embodiment 2 of the present application.

[0032] Figure 9 It is the sagittal chromatic aberration curve of the projection lens in the embodiment 2 of the present application.

[0033] Figure 10 It is the relative illumination curve of the projection lens in the embodiment 2 of the present application.

[0034] Figure 11 It is a structural schematic diagram of the projection lens in the embodiment 3 of the present application.

[0035] Figure 12 It is the F-Tanθ distortion curve of the projection lens in the embodiment 3 of the present application.

[0036] Figure 13 It is the MTF curve of the projection lens in the embodiment 3 of the present application.

[0037] Figure 14 The sagittal chromatic aberration curve of the projection lens in Embodiment 3 of the present application.

[0038] Figure 15 The relative illumination curve of the projection lens in Embodiment 3 of the present application.

[0039] The following detailed description will further describe the present application with reference to the above drawings. DETAILED DESCRIPTION

[0040] For a better understanding of the present application, various aspects of the present application will be described in more detail below with reference to the accompanying drawings. It is to be noted that these detailed descriptions are only descriptions of embodiments of the present application and are not intended in any way to limit the scope of the present application. Throughout the specification, like drawing reference numerals refer to like elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0041] It is to be noted that, in the present specification, the expressions first, second, third and the like are used only to distinguish one feature from another feature, and do not indicate any limitation on the features. Thus, the first lens discussed below can also be referred to as the second lens or the third lens without departing from the teachings of the present application.

[0042] In the drawings, the thickness, size, and shape of lenses have been slightly exaggerated for the sake of explanation. Specifically, the shape of a spherical surface or an aspherical surface shown in the drawings is shown by way of example. That is, the shape of a spherical surface or an aspherical surface is not limited to the shape of a spherical surface or an aspherical surface shown in the drawings. The drawings are merely examples and are not drawn to scale.

[0043] In the present specification, the paraxial region refers to a region near the optical axis. If a lens surface is convex and the position of the convex surface is not specified, it means that the lens surface is convex at least in the paraxial region. If a lens surface is concave and the position of the concave surface is not specified, 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 referred to as the projection-side surface of the lens, and the surface of each lens closest to the image source plane is referred to as the image-source-side surface of the lens.

[0044] It is also to be understood that the use of the terms "include", "includes", "including", "comprise", "comprises", "comprising", "have", "has", "having", or "contains" or "containing", when used in this specification, means that there are other features, elements, or components that are not listed, but are present in the described application. In addition, when expressions such as "at least one of... " appear after the list of one or more features, the phrase "at least one of... " does not mean "one or more of the listed features, but means "one or more of the features in the list. In addition, when describing embodiments of the present application, the use of "may" means "one or more embodiments of the present application". Furthermore, the term "exemplary" is intended to mean an example or an illustration.

[0045] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0046] It should be noted that the embodiments and the features in the embodiments in the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0047] The projection lens provided by the embodiment of the present application comprises six lenses, which are sequentially arranged along the optical axis from the projection surface to the image source surface as the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens.

[0048] The first lens can have a negative focal power, the projection side surface thereof can be a concave surface or a convex surface, and the image source side surface thereof is a concave surface. The second lens can have a positive focal power, the projection side surface thereof is a concave surface, and the image source side surface thereof is a convex surface. The third lens can have a focal power, the projection side surface thereof is a concave surface, and the image source side surface thereof is a convex surface. The fourth lens can have a negative focal power, the projection side surface and the image source side surface thereof are both concave surfaces. The fifth lens can have a positive focal power, the projection side surface and the image source side surface thereof are both convex surfaces. The sixth lens can have a positive focal power, the projection side surface thereof can be a concave surface or a convex surface, and the image source side surface thereof is a convex surface.

[0049] In some embodiments, the projection lens can further comprise a diaphragm, which can be arranged between the second lens and the third lens or between the third lens and the fourth lens. It can be understood that the diaphragm is used to limit the amount of light to change the brightness of the imaging. When the diaphragm is arranged between the second lens and the third lens or between the third lens and the fourth lens, the correction of the diaphragm aberration is facilitated.

[0050] In some embodiments, the projection lens can further comprise a reflecting element and a protective glass, which are sequentially arranged along the optical axis between the sixth lens and the image source surface. The reflecting element is used to turn the light beam emitted by the image source to be incident into the lens group at the front end of the projection lens, thereby reducing the total optical length. For example, the reflecting element can be selected from a prism, a 45° placed plane mirror, a beam splitter, a curved mirror, a reflective polarizer and the like. The protective glass plays a role of protecting the projection lens, preventing the light-emitting chip from being damaged, and can improve the impact resistance and scratch resistance of the projection lens, while having little effect on the imaging quality of the projection lens.

[0051] In some embodiments, the effective focal length f of the projection lens and the radius of curvature R3 of the projection-side surface of the second lens satisfy: R3 / f <-4.1; the effective focal length f of the projection lens and the radius of curvature R5 of the projection-side surface of the third lens satisfy: R5 / f <-0.5. Satisfying the above ranges can effectively correct aberration, reduce chromatic aberration, and improve the projection quality of the projection lens. More specifically, -16.7 < R3 / f < -4.5; -0.8 < R5 / f < -0.5.

[0052] In some embodiments, the chief ray angle of incidence CRA at the maximum image height of the projection lens satisfies: CRA < 2.1°. Satisfying the above range limits the projection lens to have a smaller CRA, so that the brightness uniformity of the projection image of the projection lens is better. More specifically, CRA < 2°.

[0053] In some embodiments, the effective focal length f of the projection lens and the maximum field of view FOV and the real image height IH corresponding to the maximum field of view satisfy: 0.95 < (IH / 2) / (f*tan(FOV / 2)) < 1.05. Satisfying the above range can better control the optical distortion of the projection lens, improve the resolution of the projection lens, and achieve better projection effect, which is more suitable for human eyes to watch. More specifically, 0.95 < (IH / 2) / (f*tan(FOV / 2)) < 1.02.

[0054] In some embodiments, the effective focal length f of the projection lens and the back focal length BFL of the projection lens satisfy: BFL / f > 1.8. Satisfying the above range can help to balance between obtaining good imaging quality and optical back focal length easy to assemble, ensure the imaging quality of the projection lens, avoid interference between the lens and other elements, and reduce the difficulty of lens module assembly process. More specifically, 1.8 < BFL / f < 2.8.

[0055] In some embodiments, the effective focal length f of the projection lens and the focal length f2 of the second lens satisfy: 1.8 < f2 / f < 3.8. Satisfying the above range can make the second lens have appropriate positive refractive power, effectively balance the lens aberration, and improve the imaging quality. More specifically, 2.2 < f2 / f < 3.5.

[0056] In some embodiments, the effective focal length f of the projection lens and the focal length f6 of the sixth lens satisfy: 1.3 < f6 / f < 3.1. Satisfying the above range can make the sixth lens have appropriate positive refractive power, which is conducive to converging light rays while reducing the light ray deflection angle, allowing the light rays to transition smoothly, and improving the projection quality of the projection lens. More specifically, 1.7 < f6 / f < 2.7.

[0057] In some embodiments, the effective focal length f of the projection lens and the focal length fb6 of the lens group located after the stop satisfy: 1 < fb6 / f < 2.3. Satisfying the above range, the lens group located after the stop of the projection lens has a suitable focal length, which can effectively correct the aberration generated by the lens group located before the stop, and improve the imaging quality of the projection lens. More specifically, 1.1 < fb6 / f < 2.1.

[0058] In some embodiments, the effective focal length f of the projection lens and the radius of curvature R6 of the image source side surface of the third lens satisfy: -1 < R6 / f < -0.3. Satisfying the above range, the radius of curvature of the image source side surface of the third lens is controlled within the above range, which is conducive to reducing the difficulty of correcting the edge field aberration of the projection lens. More specifically, -0.9 < R6 / f < -0.4.

[0059] In some embodiments, the radius of curvature R3 of the projection side surface of the second lens and the radius of curvature R4 of the image source side surface of the second lens satisfy: 0.3 < (R3-R4) / (R3+R4) < 1. Satisfying the above range, the light path can be controlled to be smooth, the degree of deflection of the light passing through the lens is reduced, the difficulty of correcting the off-axis aberration is reduced, and the imaging quality of the projection lens is improved. More specifically, 0.4 < (R3-R4) / (R3+R4) < 0.9.

[0060] In some embodiments, the half-aperture radius d3 of the projection side surface of the second lens and the sag Sag3 of the half-aperture radius of the projection side surface of the second lens satisfy: -0.2 < Sag3 / d3 < 0; the half-aperture radius d5 of the projection side surface of the third lens and the sag Sag5 of the half-aperture radius of the projection side surface of the third lens satisfy: -0.5 < Sag5 / d5 < -0.1. Satisfying the above range helps to control the path of the edge field light and highlight the detail information of the central field of the projection lens. More specifically, -0.08 < Sag3 / d3 < -0.01; -0.35 < Sag5 / d5 < -0.28.

[0061] In some embodiments, the distance OD on the optical axis from the projection side surface of the first lens to the projection surface and the total optical length TTL of the projection lens satisfy: 1.5 < OD / TTL < 2. Satisfying the above range, the projection lens can realize high-definition projection on a screen with a distance of 130mm-150mm, which meets the requirement of the limited space inside the vehicle-mounted HUD. More specifically, 1.58 < OD / TTL < 1.61.

[0062] In some embodiments, the effective focal length f of the projection lens and the total track length TTL satisfy: TTL / f < 8.1. Satisfying the above range, the long focal length characteristic and small volume of the lens can be achieved, and the length of the lens can be effectively limited, which is beneficial to the miniaturization of the projection lens. More specifically, 4.7 < TTL / f < 8.1.

[0063] In some embodiments, the total track length TTL of the projection lens and the real image height IH corresponding to the maximum field of view of the projection lens satisfy: 7.5 < TTL / IH < 10.6. Satisfying the above condition, the balance between the volume and the large image surface of the projection lens can be achieved. More specifically, 8.2 < TTL / IH < 9.8.

[0064] In some embodiments, the maximum field of view FOV of the projection lens and the aperture value Fno of the projection lens satisfy: 16.8° < FOV / Fno < 27.7°. Satisfying the above range, the projection lens is limited to have a suitable field of view and aperture value, which can collect light rays of a large angle and obtain good imaging quality. More specifically, 18° < FOV / Fno < 25.2°.

[0065] In some embodiments, the real image height IH corresponding to the maximum field of view of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 0.9 < IH / EPD < 1.9. Satisfying the above range, the width of the light beam entering the projection lens can be increased, the relative luminance is improved, and the dark corner is avoided. More specifically, 1 < IH / EPD < 1.8.

[0066] In some embodiments, the effective focal length f of the projection lens and the real image height IH corresponding to the maximum field of view satisfy: 0.5 < IH / f < 1. Satisfying the above range, the large image surface characteristic can be achieved, and the imaging quality of the projection lens is improved. More specifically, 0.5 < IH / f < 0.9.

[0067] In some embodiments, the effective focal length f of the projection lens and the focal length f1 of the first lens satisfy: -2.3 < f1 / f < -1.2. Satisfying the above condition, the first lens can have a proper negative focal length, so that the light rays are greatly diverged after passing through the first lens, and thus the size of the projection surface is large enough to better meet the use requirements of the vehicle-mounted HUD. More specifically, -2 < f1 / f < -1.6.

[0068] In some embodiments, the effective focal length f of the projection lens and the focal length f4 of the fourth lens satisfy: -2.6 < f4 / f < -0.2. Satisfying the above range, the fourth lens can have a proper negative focal length, the imaging area of the lens is increased, and the imaging quality is improved. More specifically, -2.3 < f4 / f < -0.5.

[0069] In some embodiments, the effective focal length f of the projection lens and the focal length f5 of the fifth lens satisfy: 0.5 < f5 / f < 2.5. Satisfying the above range, the fifth lens can have appropriate positive power, which is conducive to converging light rays while reducing the light ray deflection angle, allowing the light ray to transition smoothly, and improving the projection quality of the projection lens. More specifically, 0.8 < f5 / f < 2.2.

[0070] In some embodiments, the effective focal length f of the projection lens, the focal length f3 of the third lens, and the focal length f1a of the lens group located before the stop satisfy: |f3 / f + f1a / f| > 10. Satisfying the above range, the focal length proportions of the lens group before the stop and the third lens are reasonably controlled, the focal lengths of the lenses at the front end of the entire projection lens are reasonably divided, and the spherical aberration is reduced. More specifically, |f3 / f + f1a / f| > 12.

[0071] In some embodiments, the effective focal length f of the projection lens and the radius of curvature R7 of the projection side surface of the fourth lens satisfy: R7 / f < -0.6. Satisfying the above range, the radius of curvature of the projection side surface of the fourth lens is controlled within the above range, which is conducive to reducing the difficulty of correcting the edge field aberration of the projection lens. More specifically, -10.3 < R7 / f < -0.7.

[0072] 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: 2.2 < R3 / R4 < 10.9. Satisfying the above range, the surface shape of the second lens is reasonably controlled to have a meniscus shape, which has the characteristic of correcting field curvature, and is conducive to correcting the aberration of the entire projection lens. More specifically, 2.4 < R3 / R4 < 10.5.

[0073] In some embodiments, the radius of curvature R5 of the projection side surface of the third lens and the radius of curvature R6 of the image source side surface of the third lens satisfy: 0.5 < R5 / R6 < 1.6. Satisfying the above range, the surface shape of the third lens is reasonably controlled to have a meniscus shape, which has the characteristic of correcting field curvature, and is conducive to correcting the aberration of the entire projection lens. More specifically, 0.7 < R5 / R6 < 1.3.

[0074] In some embodiments, the radius of curvature R7 of the projection side surface of the fourth lens and the radius of curvature R8 of the image source side surface of the fourth lens satisfy: -3.9 < R7 / R8 < -0.3. Satisfying the above range, the surface shape of the fourth lens is reasonably controlled, so that the light rays are greatly diverged after passing through the fourth lens, which is conducive to increasing the imaging area and the field of view. More specifically, -3.7 < R7 / R8 < -0.5.

[0075] In some embodiments, the focal length f2 of the second lens and the radius of curvature R3 of the projection-side surface of the second lens satisfy: R3 / f2 <-1.1. By satisfying the above range, the control of the second lens image source-side surface radius of curvature and the second lens focal length within a reasonable range helps to control the smoothness of the light ray, so that as many light rays as possible are directed to the projection surface, which can effectively improve the brightness of the projection lens. More specifically, -7.6 < R3 / f2 < -1.3.

[0076] In some embodiments, the total length TTL of the projection lens and the sum ∑CT of the center thicknesses of the first lens to the sixth lens along the optical axis satisfy: 3 < TTL / ∑CT < 3.9. By satisfying the above range, the total length of the projection lens can be effectively compressed, and the structure design and production process of the projection lens are facilitated. More specifically, 3.1 < TTL / ∑CT < 3.6.

[0077] In some embodiments, the distance CTab of the lens closest to the diaphragm before and after the diaphragm along the optical axis and the center thickness CTb of the lens closest to the diaphragm after the diaphragm satisfy: 5.2 < CTab / CTb < 10.1. By satisfying the above range, the assembly of the lens is facilitated, the sensitivity of the lens near the diaphragm is reduced, and the yield of the lens is improved. More specifically, 5.8 < CTab / CTb < 9.2.

[0078] In some embodiments, the center thickness CT1 of the first lens along the optical axis and the center thickness CT2 of the second lens along the optical axis satisfy: 9.5 < CT2 / CT1 < 11.2. By satisfying the above range, the center thickness ratio between the first lens and the second lens is reasonably controlled, and the machinability of the lens and the reasonable arrangement in the optical system are maintained. More specifically, 10.1 < CT2 / CT1 < 10.4.

[0079] In some embodiments, the projection lens satisfies the condition: 9.8mm < f < 20.2mm, 4.6mm < EPD < 11.2mm, 82mm < TTL < 93mm, 1.6 < Fno < 2.2, 8.2mm < IH < 11.8mm, 28° < FOV < 56°, BFL > 28mm; wherein f represents the effective focal length of the projection lens, EPD represents the entrance pupil diameter of the projection lens, TTL represents the total optical length of the projection lens, Fno represents the aperture value of the projection lens, IH represents the real image height corresponding to the maximum field of view angle of the projection lens, FOV represents the maximum field of view angle of the projection lens, and BFL represents the back focal length of the projection lens. Satisfying the above conditions indicates that the projection lens provided by the embodiments of the present application at least has the characteristics of large aperture, large field of view angle, large image surface, long back focal length, etc. More specifically, 10.9mm < f < 18.4mm, 5.2mm < EPD < 10.4mm, 87.7mm < TTL < 87.9mm, 1.7 < Fno < 2.1, 8.8mm < IH < 10.8mm, 32° < FOV < 50.2°, 29.5mm < BFL < 33.8mm.

[0080] In some embodiments, the fourth lens and the fifth lens can be bonded to form a bonded lens, which can effectively correct the chromatic aberration of the projection lens, reduce the sensitivity of the projection lens to eccentricity, balance the aberration of the projection lens, and improve the imaging quality of the projection lens; and 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.

[0081] In some embodiments, the lens materials in the projection lens provided by the present application can be glass or plastic. When the lens material is plastic, the production cost can be effectively reduced. When the lens material is glass, the geometric chromatic aberration of the optical system can be effectively corrected by the low dispersion characteristic of the glass itself. More specifically, the first lens, the second lens, the fourth lens, the fifth lens and the sixth lens in the projection lens provided by the present application can be glass lenses, and the third lens can be a plastic lens, thereby reducing the cost.

[0082] In some embodiments, the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens can adopt a spherical lens or an aspherical lens. Compared with the spherical structure, the aspherical structure can effectively reduce the aberration of the optical system, thereby reducing the number of lenses and the size of the lenses, and better realizing the miniaturization of the lens. More specifically, the first lens, the second lens, the fourth lens, the fifth lens and the sixth lens in the projection lens provided by the present application can adopt a spherical lens, and the third lens can adopt an aspherical lens.

[0083] In various embodiments of the present application, when the lens adopts an aspherical lens, the shape of each aspherical surface of the projection lens satisfies the following equation:

[0084]

[0085] wherein z is the distance of the curved surface from the vertex of the curved surface in the direction of the optical axis, h is the distance from the optical axis to the curved surface, c is the curvature of the vertex of the curved surface, 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.

[0086] The present application is further described in the following embodiments. In each of the embodiments, the thickness, the radius of curvature, and the material selection of each lens in the projection lens are different, and the specific differences can be found in the parameter table of each embodiment. The following embodiments are merely preferred embodiments of the present application, and the embodiments of the present application are not limited to the following embodiments. Any changes, substitutions, combinations, or simplifications made without departing from the innovative points of the present application should be considered as equivalent replacement manners and should be included in the protection scope of the present application.

[0087] Embodiment 1

[0088] Referring to FIG. 1, a structure schematic diagram of a projection lens provided in Embodiment 1 of the present application is shown, which includes, in order along the optical axis from the projection surface to the image source surface, a first lens L1, a second lens L2, a diaphragm ST, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a reflecting element G1, and a protective glass G2. Figure 1 The first lens L1 has a negative focal power, and both the projection side surface S1 and the image source side surface S2 thereof are concave surfaces.

[0089] The second lens L2 has a positive focal power, and the projection side surface S3 thereof is a concave surface, and the image source side surface S4 thereof is a convex surface.

[0090] The third lens L3 has a positive focal power, and the projection side surface S5 thereof is a concave surface, and the image source side surface S6 thereof is a convex surface.

[0091] The fourth lens L4 has a negative focal power, and both the projection side surface S7 and the image source side surface S8 thereof are concave surfaces.

[0092] The fifth lens L5 has a positive focal power, and both the projection side surface S8 and the image source side surface S9 thereof are convex surfaces.

[0093] The fourth lens L4 and the fifth lens L5 form a cemented lens group with a negative focal power, and 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.

[0094]

[0095] ​The sixth lens L6 has positive refractive power, the projection side surface S10 is a concave surface, and the image source side surface S11 is a convex surface;

[0096] The projection side surface S12 and the image source side surface S13 of the reflecting element G1 are both planar surfaces;

[0097] The projection side surface S14 and the image source side surface S15 of the protective glass G2 are both planar surfaces;

[0098] The image source surface S16 is a planar surface.

[0099] The first lens L1, the second lens L2, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all glass spherical lenses; and the third lens L3 is a plastic aspherical lens.

[0100] The related parameters of the lenses in the projection lens in Example 1 are shown in Table 1-1.

[0101] Table 1-1

[0102]

[0103] The aspherical lens surface parameters of the projection lens in Example 1 are shown in Table 1-2.

[0104] Table 1-2

[0105] Face number K B C D E F S5 7.99E-01 -2.41E-05 6.61E-06 1.75E-08 9.90E-10 2.21E-11 S6 -8.15E-01 -2.33E-05 5.12E-06 -1.45E-07 4.04E-09 -3.28E-11

[0106] Figure 2 The F-Tanθ distortion curve of Example 1 is shown, which represents the F-Tanθ distortion of light rays at different image heights on the imaging surface. The horizontal axis represents the F-Tanθ distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the F-Tanθ distortion of the projection lens is controlled within -1% to 0, the image compression in the edge angle region is relatively flat, and the clarity of the expanded image is effectively improved.

[0107] Figure 3 The MTF (Modulation Transfer Function) curve of Example 1 is shown, which represents the imaging modulation degree of the lens at different spatial frequencies under each field of view. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. As can be seen from the figure, the MTF value of the present embodiment is above 0.28 in the full field of view, and in the range of 0-60 lp / mm, the MTF curve uniformly and smoothly decreases from the center to the edge of the field of view, indicating that the projection lens has good imaging quality and good detail resolution capability.

[0108] Figure 4The vertical color aberration curve of the projection lens of Example 1 is shown, which represents the color aberration of each wavelength at different image heights on the imaging plane relative to the central wavelength (0.55 μm), the horizontal axis represents the vertical color aberration value of each wavelength relative to the central wavelength (unit: μm), and the vertical axis represents the normalized field angle. As can be seen from the figure, the vertical color aberration of the longest wavelength and the shortest wavelength is controlled within -1 μm ~ 5 μm, which shows that the projection lens can very well correct the color aberration of the edge field of view.

[0109] Figure 5 The relative illumination curve of Example 1 is shown, which represents the relative illumination value of different field angles on the imaging plane, the horizontal axis represents the half field 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 angle, which shows that the projection lens has very good relative illumination.

[0110] Example 2

[0111] Referring to Figure 6 , a structure schematic diagram of the projection lens provided in Example 2 of the present application is shown, and the main difference between this embodiment and Example 1 is that the diaphragm ST is located between the third lens L3 and the fourth lens L4; the third lens L3 has a negative focal power; the fourth lens L4 and the fifth lens L5 are not cemented lens groups; the projection side surface S1 of the first lens L1 is a convex surface; the projection side surface S11 of the sixth lens L6 is a convex surface; and the optical parameters such as the curvature radius and the lens thickness of each lens surface are different.

[0112] The related parameters of each lens in the projection lens in Example 2 are shown in Table 2-1.

[0113] Table 2-1

[0114]

[0115]

[0116] The surface type parameters of the aspheric lens of the projection lens in Example 2 are shown in Table 2-2.

[0117] Table 2-2

[0118] Face number K B C D E F S5 -5.86E-01 4.49E-04 9.29E-06 -3.01E-07 6.10E-09 -4.28E-11 S6 -1.38E+00 1.87E-04 5.24E-06 -1.65E-08 -2.51E-09 5.24E-11

[0119] As can be seen from Figure 7 , the F-Tanθ distortion of the projection lens is controlled within -5% ~ 0, the image compression in the edge angle region is relatively flat, and the clarity of the expanded image is effectively improved.

[0120] As can be seen from Figure 8As can be seen, the MTF value of this embodiment is above 0.3 throughout the entire field of view. Within the range of 0 to 60 lp / mm, the MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens has good imaging quality and good detail resolution.

[0121] from Figure 9 As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within 0 to 6 μm, indicating that the projection lens can correct the chromatic aberration at the edge of the field of view very well.

[0122] from Figure 10 As can be seen, the relative illuminance value of the projection lens is still greater than 97% at the maximum half field of view, indicating that the projection lens has good relative illuminance.

[0123] Example 3

[0124] Please see Figure 11 The diagram shows a schematic of the projection lens provided in Embodiment 3 of the present invention. The main difference between this embodiment and Embodiment 1 is that: the aperture ST is located between the third lens L3 and the fourth lens L4; the third lens L3 has negative optical power; the fourth lens L4 and the fifth lens L5 form a cemented lens group with positive optical power; the projection side surface S1 of the first lens L1 is convex; the projection side surface S10 of the sixth lens L6 is convex; and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0125] The relevant parameters of each lens in the projection lens in Example 3 are shown in Table 3-1.

[0126] Table 3-1

[0127]

[0128]

[0129] The surface profile parameters of the aspherical lens in the projection lens of Example 3 are shown in Table 3-2.

[0130] Table 3-2

[0131] Face number K B C D E F S5 -5.47E-01 7.32E-04 4.17E-06 -8.17E-08 1.29E-09 -4.87E-12 S6 -1.85E+00 2.24E-04 4.33E-06 -5.50E-08 3.04E-10 6.96E-12

[0132] from Figure 12 As can be seen, the F-Tanθ distortion of the projection lens is controlled within -5% to 0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the unfolded image.

[0133] from Figure 13It can be seen from the MTF curves that the MTF values of the projection lens of the embodiment are all above 0.3 in the full field of view, and the MTF curves are uniformly and smoothly decreased from the center to the edge of the field of view in the range of 0-60 lp / mm, which indicates that the projection lens has good imaging quality and good detail resolution capability.

[0134] From Figure 14 It can be seen from the MTF curves that the MTF values of the projection lens of the embodiment are all above 0.3 in the full field of view, and the MTF curves are uniformly and smoothly decreased from the center to the edge of the field of view in the range of 0-60 lp / mm, which indicates that the projection lens has good imaging quality and good detail resolution capability.

[0135] From Figure 15 It can be seen from the MTF curves that the MTF values of the projection lens of the embodiment are all above 0.3 in the full field of view, and the MTF curves are uniformly and smoothly decreased from the center to the edge of the field of view in the range of 0-60 lp / mm, which indicates that the projection lens has good imaging quality and good detail resolution capability.

[0136] Please refer to Table 4 for the optical properties corresponding to the above embodiments, including the effective focal length f, the total optical length TTL, the aperture value Fno, the real image height IH corresponding to the maximum field of view angle, the chief ray angle of incidence CRA at the maximum image height, the maximum field of view angle FOV of the projection lens, and the numerical values corresponding to each conditional expression in each embodiment.

[0137] Table 4

[0138]

[0139]

[0140] In summary of the above embodiments, the projection lens provided by the present application improves the imaging quality of the projection lens, reduces aberration, and improves the imaging quality of the projection lens by reasonable configuration of each lens surface and reasonable matching of optical power. At the same time, the projection lens has a large aperture, which is conducive to improving the brightness and increasing the light energy utilization rate; has a small CRA, the brightness uniformity of the projection picture is good, has small chromatic aberration and distortion, so that the picture is not deformed, and the imaging quality is good.

[0141] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0142] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A projection lens, in total six pieces of lenses, characterized in that, In order from the projection surface to the image source surface along the optical axis: a first lens with negative optical power, the image source side surface of which is a concave surface; a second lens with positive optical power, the projection side surface of which is a concave surface and the image source side surface of which is a convex surface; a third lens with optical power, the projection side surface of which is a concave surface and the image source side surface of which is a convex surface; a fourth lens with negative optical power, both the projection side surface and the image source side surface of which are concave surfaces; a fifth lens with positive optical power, both the projection side surface and the image source side surface of which are convex surfaces; a sixth lens with positive optical power, the image source side surface of which is a convex surface; wherein the effective focal length f of the projection lens and the projection side surface curvature radius R3 of the second lens satisfy -16.7 < R3 / f < -4.1; the effective focal length f of the projection lens and the projection side surface curvature radius R5 of the third lens satisfy -0.8 < R5 / f < -0.5; the chief ray angle of incidence CRA at the maximum image height of the projection lens satisfies 1.77° ≤ CRA < 2.1°.

2. The projection lens according to claim 1, characterized in that the effective focal length f of the projection lens and the projection side surface curvature radius R3 of the second lens satisfy -16.76 ≤ R3 / f ≤ -4.51; the effective focal length f of the projection lens and the projection side surface curvature radius R5 of the third lens satisfy -0.7 ≤ R5 / f ≤ -0.52; the chief ray angle of incidence CRA at the maximum image height of the projection lens satisfies 1.77° ≤ CRA ≤ 1.91°.

3. The projection lens of claim 1, wherein the effective focal length f of the projection lens, the maximum field of view FOV and the real image height IH corresponding to the maximum field of view satisfy 0.95 < (IH / 2) / (f*tan(FOV / 2)) < 1.

05.

4. The projection lens of claim 1, wherein the effective focal length f of the projection lens and the back focal length BFL of the projection lens satisfy 1.8 < BFL / f < 2.

8.

5. The projection lens of claim 1, wherein the effective focal length f of the projection lens and the focal length f2 of the second lens satisfy 1.8 < f2 / f < 3.

8.

6. The projection lens of claim 1, wherein the effective focal length f of the projection lens and the focal length f6 of the sixth lens satisfy 1.3 < f6 / f < 3.

1.

7. The projection lens of claim 1, wherein a diaphragm is arranged between the second lens and the third lens or between the third lens and the fourth lens, and the effective focal length f of the projection lens and the focal length fb6 of the lens group located after the diaphragm satisfy 1 < fb6 / f < 2.

3.

8. The projection lens of claim 1, wherein, the effective focal length f of the projection lens and the image source side surface curvature radius R6 of the third lens satisfy -1 < R6 / f < -0.

3.

9. The projection lens of claim 1, wherein, the projection side surface curvature radius R3 of the second lens and the image source side surface curvature radius R4 of the second lens satisfy 0.3 < (R3-R4) / (R3+R4) < 1.

10. The projection lens of claim 1, wherein, the projection side surface half diameter d3 of the second lens and the projection side surface half diameter sag3 of the second lens satisfy -0.2 < sag3 / d3 < 0; the projection side surface half diameter d5 of the third lens and the projection side surface half diameter sag5 of the third lens satisfy -0.5 < sag5 / d5 < -0.1.

Images