projection lens

Abstract

The present application provides a kind of projection lens, including successively along optical axis from projection surface to image source surface: the first lens with positive focal power, its projection side surface is convex;Second lens with negative focal power, its projection side surface is convex, its image source side surface is concave;The third lens with positive focal power, its projection side surface is concave, its image source side surface is convex;Fourth lens with negative focal power, its projection side surface is concave;The fifth lens with positive focal power, its projection side surface is concave, its image source side surface is convex;The sixth lens with positive focal power, its projection side surface is convex, its image source side surface is convex;Prism;Protective glass;Flat glass is arranged between the prism and protective glass, flat glass can be located in first position or second position by switching device.The present application provides the clear imaging at two different projection distances by the switching of flat glass, and completes the switching of close-up and long shot.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of imaging lenses, and particularly 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 playing an increasingly important role 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, and can also display warning information from various driving assistance systems, such as lane departure warning, pedestrian avoidance warning from night vision assistance systems with pedestrian recognition function, 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 cannot meet the clear imaging of different distances under the premise of fixed focus. SUMMARY

[0004] To solve the above problems, the present application provides a projection lens with excellent imaging quality.

[0005] The present application provides a projection lens, which comprises, in order along the optical axis from the projection surface to the image source surface:

[0006] a first lens with positive focal power, whose projection side surface is convex;

[0007] a second lens with negative focal power, whose projection side surface is convex and whose image source side surface is concave;

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

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

[0010] a fifth lens with positive focal power, whose projection side surface is concave and whose image source side surface is convex;

[0011] a sixth lens with positive focal power, whose projection side surface is convex and whose image source side surface is convex;

[0012] The prism comprises an incident plane, a reflection plane and an exit plane, all of which are planes, light rays enter the prism along an optical axis from the incident plane, are reflected by the reflection plane, and exit from the exit plane; the reflection plane and the optical axis of the incident plane and the optical axis of the exit plane form an included angle of 45° respectively;

[0013] The protective glass has a planar projection side surface and a planar image source side surface;

[0014] A flat glass is arranged between the prism and the protective glass, and can be switched between a first position and a second position by a switching device; when the flat glass is in the first position, the light path does not pass through the flat glass; when the flat glass is in the second position, the flat glass is located on the optical axis and between the prism and the protective glass, the flat glass is parallel to the protective glass, and the light path passes through the flat glass.

[0015] Further preferably, the projection surface has a first inclination angle with a vertical plane; the protective glass and the image source surface have a second inclination angle with a horizontal plane.

[0016] Further preferably, the first inclination angle is 14°-16°; the second inclination angle is 1°-3°.

[0017] Further preferably, when the flat glass is in the first position, the distance CT0 from the projection surface to the first lens satisfies 155mm<CT0<165mm; when the flat glass is in the second position, the distance CT0 from the projection surface to the first lens satisfies 190mm<CT0<200mm.

[0018] Further preferably, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy -2.4<f2 / f<-1.

[0019] Further preferably, the real image height IH corresponding to the maximum field angle of the projection lens and the aperture value Fno of the projection lens satisfy 4mm<IH / Fno<4.5mm.

[0020] Further preferably, the back focal length BFL of the projection lens and the effective focal length f of the projection lens satisfy 0.2<BFL / f<0.25.

[0021] Further preferably, the projection side surface curvature radius R5 of the third lens and the image source side surface curvature radius R6 of the third lens satisfy 1<(R5+R6) / (R5-R6)<2.1.

[0022] It is further preferred that the projection-side surface half-aperture radius sag of the first lens SAG11, the image source-side surface half-aperture radius sag of the first lens SAG12 and the central thickness CT1 of the first lens satisfy: -0.3 < (SAG12-SAG11) / CT1 < -0.1.

[0023] It is further preferred that the projection-side surface half-aperture radius DM11 of the first lens and the image source-side surface half-aperture radius DM62 of the sixth lens satisfy: 0.9 < DM11 / DM62 < 1.3.

[0024] The projection lens provided by the application realizes clear imaging at two different projection distances through switching of the flat glass, completes switching of close-range and long-range, and effectively improves the convenience and safety of driving. Meanwhile, through reasonable configuration of the surface shape of each lens and reasonable matching of the optical power, the imaging quality of the projection lens is improved, the aberration is reduced, the projection quality of the projection lens is improved, and the lens has one or more advantages such as small distortion, small CRA, uniform illumination, high imaging quality and the like. BRIEF DESCRIPTION OF DRAWINGS

[0025] The above and / or additional aspects and advantages of the application will become apparent and be readily appreciated from the description of the embodiments, taken in conjunction with the following drawings in which:

[0026] Figure 1 Structure diagram of the projection lens without flat glass in the embodiment 1 of the application Figure One .

[0027] Figure 2 Structure diagram of the projection lens without flat glass in the embodiment 1 of the application Figure Two .

[0028] Figure 3 Structure diagram of the projection lens with flat glass in the embodiment 1 of the application Figure One .

[0029] Figure 4 Structure diagram of the projection lens with flat glass in the embodiment 1 of the application Figure Two .

[0030] Figure 5 Field curvature curve of the projection lens in the embodiment 1 of the application.

[0031] Figure 6 F-Tan(Theta) distortion curve of the projection lens in the embodiment 1 of the application.

[0032] Figure 7 Axial aberration curve of the projection lens in the embodiment 1 of the application.

[0033] Figure 8 The sagittal chromatic aberration curve of the projection lens in Embodiment 1 of the present application.

[0034] Figure 9 The relative illumination curve of the projection lens in Embodiment 1 of the present application.

[0035] Figure 10 The structure diagram of the projection lens without flat glass in Embodiment 2 of the present application Figure One .

[0036] Figure 11 The structure diagram of the projection lens without flat glass in Embodiment 2 of the present application Figure Two .

[0037] Figure 12 The structure diagram of the projection lens with flat glass in Embodiment 2 of the present application Figure One .

[0038] Figure 13 The structure diagram of the projection lens with flat glass in Embodiment 2 of the present application Figure Two .

[0039] Figure 14 The field curvature curve of the projection lens in Embodiment 2 of the present application.

[0040] Figure 15 The F-Tan(Theta) distortion curve of the projection lens in Embodiment 2 of the present application.

[0041] Figure 16 The axial aberration curve of the projection lens in Embodiment 2 of the present application.

[0042] Figure 17 The sagittal chromatic aberration curve of the projection lens in Embodiment 2 of the present application.

[0043] Figure 18 The relative illumination curve of the projection lens in Embodiment 2 of the present application.

[0044] Figure 19 The structure diagram of the projection lens without flat glass in Embodiment 3 of the present application Figure One .

[0045] Figure 20 The structure diagram of the projection lens without flat glass in Embodiment 3 of the present application Figure Two .

[0046] Figure 21 The structure diagram of the projection lens with flat glass in Embodiment 3 of the present application Figure One .

[0047] Figure 22Structure diagram of the projection lens with a flat glass in Embodiment 3 of the present application Figure Two .

[0048] Figure 23 Field curvature graph of the projection lens in Embodiment 3 of the present application

[0049] Figure 24 F-Tan(Theta) distortion graph of the projection lens in Embodiment 3 of the present application

[0050] Figure 25 Axial aberration graph of the projection lens in Embodiment 3 of the present application

[0051] Figure 26 Vignetting graph of the projection lens in Embodiment 3 of the present application

[0052] Figure 27 Relative illumination graph of the projection lens in Embodiment 3 of the present application

[0053] The following detailed description will further describe the present application with reference to the above drawings. DETAILED DESCRIPTION

[0054] 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 understood that the detailed description is merely descriptive of embodiments of the present application and is not intended to limit the scope of the present application in any way. Throughout the specification, like reference numerals refer to like elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0055] It is noted that, in this specification, the expressions first, second, third, etc. are merely used 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.

[0056] 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.

[0057] In the present disclosure, 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.

[0058] It should also be understood that the words "comprise", "comprising", "include", "including", and / or "contain", when used in this specification, specify the presence of stated features, elements, and / or components, but do not preclude the presence or addition of one or more other features, elements, components, and / or groups thereof. In addition, when expressions such as "at least one of... " appear after a list of features, it modifies the entire list of features and not the individual elements of the list. Furthermore, when describing embodiments of the present application, the word "may" means "one or more embodiments of the present application". Also, the word "exemplary" is intended to mean an example or an illustration.

[0059] 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 should also be understood that the terms 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.

[0060] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0061] The projection lens provided by the embodiments of the present application comprises, in order along the optical axis from the projection plane to the image source plane, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a prism, and a protective glass.

[0062] The variable position flat glass is arranged between the prism and the protective glass, and the flat glass can be located at a first position or a second position through a switching device. When the flat glass is at the first position, the light path does not pass through the flat glass; when the flat glass is at the second position, the flat glass is located on the optical axis and between the prism and the protective glass, the flat glass is parallel to the protective glass, and the light path passes through the flat glass. Through the switching of the flat glass, clear imaging at two different projection distances can be achieved, and the design of the projection lens can effectively improve the convenience and safety of driving. When the flat glass is not added, close-range imaging can be realized; when the flat glass is added between the prism and the chip protective glass (the flat glass is added or removed through an automatic controllable switching device), long-range projection imaging can be realized. According to the inserted and non-inserted states of the flat glass, the switching of the close-range and long-range projection is completed. It can be understood that the light propagates in the flat glass for a longer optical path than in the air, increasing the effective length of the light path and increasing the effective image distance of the system. Since the object and image move on the same side, the corresponding projection object distance increases. The insertion of the flat glass does not change the focal length of the projection lens, but changes the projection distance required for clear imaging of the system through light path control, thereby realizing double focal plane switching.

[0063] Specifically, the first lens can have a positive refractive power, the projection side surface thereof is a convex surface, and the image source side surface thereof can be a concave surface or a convex surface. The second lens can have a negative refractive power, the projection side surface thereof is a convex surface, and the image source side surface thereof is a concave surface. The third lens can have a positive refractive 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 refractive power, the projection side surface thereof is a concave surface, and the image source side surface thereof can be a concave surface or a convex surface. The fifth lens can have a positive refractive power, the projection side surface thereof is a concave surface, and the image source side surface thereof is a convex surface. The sixth lens can have a positive refractive power, the projection side surface thereof is a convex surface, and the image source side surface thereof is a convex surface. The protective glass has a plane projection side surface and a plane image source side surface, and the protective glass serves to protect the projection lens and prevent the photosensitive chip from being damaged.

[0064] The prism can be a right-angled triangular prism, including an incident plane, a reflection plane and an exit plane which are all planes. Light rays enter the prism from the incident plane along the optical axis, are reflected by the reflection plane, and exit from the exit plane. The reflection plane and the optical axis of the incident plane and the optical axis of the exit plane form an included angle of 45°. Through the arrangement of the prism, the direction of the light path can be changed, the light path is bent, the direction of the incident light is perpendicular to the arrangement direction of the multiple lenses, and the overall thickness of the optical system is reduced.

[0065] In some embodiments, the third lens and the fourth lens can be cemented to form a cemented lens group with optical power, which can effectively correct chromatic aberration of the projection lens, reduce sensitivity of the projection lens to decentration, balance aberration of the projection lens, and improve imaging quality of the projection lens; and can also reduce assembly sensitivity of the projection lens, thereby reducing the difficulty of the processing technology of the projection lens and improving the assembly yield of the projection lens.

[0066] In some embodiments, the projection lens can further include a diaphragm, which can be located between the second lens and the third 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 located between the second lens and the third lens, the correction of the diaphragm aberration is facilitated.

[0067] In some embodiments, the projection surface has a first inclination angle with respect to a vertical plane, and the protective glass and the image source surface have a second inclination angle with respect to a horizontal plane. The first inclination angle is 14°-16°, and the second inclination angle is 1°-3°. It can be understood that the projection surface is arranged to be inclined with respect to the first lens, and the flat glass, the protective glass, and the image source surface are arranged to be inclined with respect to the prism.

[0068] In some embodiments, when the flat glass is in the first position, the distance CT0 from the projection surface to the first lens satisfies 155mm<CT0<165mm; and when the flat glass is in the second position, the distance CT0 from the projection surface to the first lens satisfies 190mm<CT0<200mm. After the flat glass is added, the corresponding optimal projection surface distance is farther, which can satisfy clear imaging at two different projection distances, and can effectively improve the convenience and safety of driving.

[0069] In some embodiments, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy -2.4<f2 / f<-1. Satisfying the above condition, the negative lens of the second lens can adjust the chief ray angle and reduce lens distortion.

[0070] In some embodiments, the real image height IH corresponding to the maximum field angle of the projection lens and the aperture value Fno of the projection lens satisfy 4mm<IH / Fno<4.5mm. Satisfying the above range is conducive to realizing large image surface characteristics and improving the imaging quality of the projection lens.

[0071] In some embodiments, the back focal length BFL of the projection lens and the effective focal length f of the projection lens satisfy 0.2<BFL / f<0.25. Satisfying the above range is helpful to realize short back focus and limit the length of the lens.

[0072] 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: 1 < (R5+R6) / (R5-R6) < 2.1. Satisfying the above range can make the light ray trend more stable; at the same time, coma and field curvature can be corrected, the flatness of imaging is improved, and the imaging quality of the projection lens is improved.

[0073] In some embodiments, the half-aperture sagittal height SAG11 of the projection-side surface of the first lens, the half-aperture sagittal height SAG12 of the image source-side surface of the first lens, and the central thickness CT1 of the first lens satisfy: -0.3 < (SAG12-SAG11) / CT1 < -0.1. Satisfying the above range helps to control the trend of the edge field of view light, and highlights the detail information of the central field of view of the projection lens.

[0074] In some embodiments, the half-aperture diameter DM11 of the projection-side surface of the first lens and the half-aperture diameter DM62 of the image source-side surface of the sixth lens satisfy: 0.9 < DM11 / DM62 < 1.3. Satisfying the above range, by reasonably setting the aperture relationship of the first and last lenses, the area of the light ray entering the image plane is increased while ensuring that as many light rays as possible enter the system, and high relative illumination of the lens is realized.

[0075] In some embodiments, the back focal length BFL of the projection lens and the total optical length TTL of the projection lens satisfy: 0.06 < BFL / TTL < 0.08. The back focal length BFL is the distance on the optical axis from the prism exit surface to the image source surface. Satisfying the above condition, reasonably configuring the ratio of the back focal length of the projection lens to the total optical length of the projection lens is beneficial to realize the short back focal length of the projection lens, and in the case of ensuring that the installation of the optical element (flat glass) has sufficient space, it is beneficial to realize the miniaturization of the projection lens.

[0076] 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 < 3. Satisfying the above condition can effectively limit the length of the lens, which is beneficial to realize the miniaturization of the projection lens.

[0077] In some embodiments, the effective focal length f of the projection lens, the maximum field of view angle FOV of the projection lens, and the real image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 50° < (f x FOV) / IH < 60°. Satisfying the above condition formula, by reasonably limiting the relationship between the focal length, the field of view angle, and the image height of the projection lens, it is beneficial to realize the balance of the super-large field of view angle and the larger target surface imaging of the projection lens.

[0078] In some embodiments, a real image height IH corresponding to a maximum field angle of the projection lens and an effective focal length f of the projection lens satisfy: 0.5 < IH / f < 0.6. Satisfying the above condition, a larger field angle and imaging range can be achieved, the large image surface characteristics can be realized while the depth of field of the projection lens is ensured, and thus the imaging quality of the optical system is improved.

[0079] In some embodiments, an optical total length TTL of the projection lens and the real image height IH corresponding to the maximum field angle of the projection lens satisfy: 4.5 < TTL / IH < 5.5. Satisfying the above condition, the miniaturization of the lens can be better achieved, and meanwhile, the lens has a larger image surface under the condition of the same total length, which can match a larger imaging chip to realize high-definition imaging.

[0080] In some embodiments, a focal length f1 of the first lens and the effective focal length f of the projection lens satisfy: 1.7 < f1 / f < 3.6. Satisfying the above range, by reasonably setting the focal length of the first lens, the change degree of the refraction angle of the incident light can be slowed down, and the refraction change is avoided from being too strong to generate too much aberration, and meanwhile, more light can enter the rear optical system, the field angle of the lens is increased, and the overall imaging quality is improved.

[0081] In some embodiments, a focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: 0.3 < f3 / f < 0.55; and a focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: -0.5 < f4 / f < -0.25. Satisfying the above conditions, the third lens and the fourth lens are glued to form a double-glued lens. The third lens and the fourth lens can have opposite positive and negative focal powers, so that various aberrations of the optical system are fully corrected, the resolution is improved, and the optical performance such as distortion is optimized under the premise of compact structure.

[0082] In some embodiments, a focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 1 < f5 / f < 1.5. Satisfying the above condition, by reasonably setting the focal length of the fifth lens, the light can be smoothly transitioned, the correction of astigmatism and field curvature is facilitated, the imaging quality of the projection lens is improved, and the stability of the optical system is ensured.

[0083] In some embodiments, a focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 1.1 < f6 / f < 1.4. Satisfying the above range, the sixth lens can have appropriate positive focal power, which is conducive to converging light while reducing the light deflection angle, so that the light trend is smoothly transitioned, and the projection quality of the projection lens is improved.

[0084] In some embodiments, a real image height IH corresponding to a maximum field angle of the projection lens and an entrance pupil diameter EPD of the projection lens satisfy: 1.3<IH / EPD<1.6. Satisfying the above range can increase the width of the light bundle entering the projection lens, improve the relative luminance, and avoid the generation of dark corners.

[0085] In some embodiments, a projection side surface radius of curvature R1 of the first lens and an image source side surface radius of curvature R2 of the first lens satisfy: -0.8<R1 / R2<0.2. Satisfying the above range can reasonably set the surface shape of the first lens and enhance the light collecting ability of the first lens.

[0086] In some embodiments, a projection side surface radius of curvature R5 of the third lens and an image source side surface radius of curvature R6 of the third lens satisfy: 2.8<R5 / R6<22. By making the optical system satisfy the above relationship, the ratio of the projection side surface radius of curvature of the third lens and the image source side surface radius of curvature of the third lens is reasonably configured, the shape of the third lens is controlled, the spherical aberration, chromatic aberration and field curvature of the optical system are comprehensively balanced, the risk of ghosting is reduced, the resolving power of the optical system is improved, and the processing difficulty of the third lens is also reduced.

[0087] In some embodiments, a projection side surface radius of curvature R3 of the second lens and an image source side surface radius of curvature R4 of the second lens satisfy: 3<(R3+R4) / (R3-R4)<5. Satisfying the above range can reduce the angle between the incident light and the projection side surface of the first lens, effectively reduce the working aperture of the first lens, and facilitate the miniaturization of the projection lens.

[0088] In some embodiments, a projection side surface radius of curvature R11 of the sixth lens and an image source side surface radius of curvature R12 of the sixth lens satisfy: -0.5<(R11+R12) / (R11-R12)<0.2. Satisfying the above range can increase the divergence of the light, increase the area of the light entering the imaging surface, realize large target surface imaging of the lens, and improve the imaging quality of the projection lens.

[0089] In some embodiments, a projection side surface radius of curvature R1 of the first lens and an effective focal length f of the projection lens satisfy: 1.2<R1 / f<5. Satisfying the above range can effectively improve the brightness of the projection lens by reasonably setting the surface shape of the projection side of the first lens.

[0090] In some embodiments, an image source side surface radius of curvature R12 of the sixth lens and an effective focal length f of the projection lens satisfy: -3.3<R12 / f<-1.2. Satisfying the above range can increase the imaging area, reduce chromatic aberration, and improve the imaging quality.

[0091] In some embodiments, the focal length f1 of the first lens and the focal length f6 of the sixth lens satisfy: 1.5 < f1 / f6 < 2.8. By satisfying the above condition, by reasonably setting the focal length relationship of the first and last lenses in the lens, while ensuring that as many light rays as possible enter the system, the area of the light entering the imaging surface is increased, which is conducive to realizing large image surface imaging of the lens, while increasing the amount of light entering, improving the relative luminance of the system.

[0092] In some embodiments, the central thickness CT1 of the first lens and the central thickness CT2 of the second lens satisfy: 0.9 < CT1 / CT2 < 1.5. By satisfying the above condition, the ratio of the thickness of the first lens on the optical axis and the thickness of the second lens on the optical axis is reasonably configured, and the first lens and the second lens can regulate each other, maintaining the characteristics of miniaturization of the optical system.

[0093] In some embodiments, the total length TTL of the projection lens and the sum ∑CT of the central thicknesses of the first lens to the sixth lens along the optical axis satisfy: 0.3 < ∑CT / TTL < 0.45. By satisfying the above condition, the total length of the projection lens can be effectively compressed.

[0094] In some embodiments, the central thickness CT2 of the second lens and the edge thickness ET2 of the second lens satisfy: 1.1 < CT2 / ET2 < 1.4. By making the optical system satisfy the above relationship, it is beneficial for the processing and molding of the lens, it is beneficial for reducing the difficulty of assembly, and it can effectively correct the field curvature of the system.

[0095] In some embodiments, the projection side surface radius of curvature R1 of the first lens, the image source side surface radius of curvature R2 of the first lens, and the central thickness CT1 of the first lens satisfy: -0.8 < R1 / (R2+CT1) < 0.3. By satisfying the above range, the correction difficulty of the edge field distortion can be reduced, and the distortion can be controlled within a reasonable range.

[0096] In some embodiments, the projection side surface half-aperture sagittal height SAG61 of the sixth lens, the image source side surface half-aperture sagittal height SAG62 of the sixth lens, and the central thickness CT6 of the sixth lens satisfy: -0.7 < (SAG62-SAG61) / CT6 < -0.5. By satisfying the above range, by controlling the height difference between the image source side surface and the projection side surface of the sixth lens and the relationship with the central thickness of the sixth lens, it is beneficial to correct the coma of the off-axis field, and it is beneficial to improve the imaging quality of the off-axis field of the projection lens.

[0097] In some embodiments, the projection side surface half-aperture DM11 of the first lens and the real image height IH corresponding to the maximum field angle of the projection lens satisfy: 0.8 < DM11 / IH < 1. By satisfying the above range, the balance between the size of the front aperture of the projection lens and the image surface can be ensured.

[0098] In some embodiments, the effective focal length f of the projection lens, the maximum field of view FOV of the projection lens, and the real image height IH corresponding to the maximum field of view FOV of the projection lens satisfy: 0.98 < (2xfxtan(FOV / 2)) / IH < 1. Satisfying the above condition means that the distortion of the projection lens is ≤2%, which can make the lens have a smaller distortion value, can provide a high-definition imaging effect, improve the resolving power of the projection lens, and can achieve a better projection effect, and is more suitable for human eyes to watch.

[0099] In some embodiments, the chief ray angle of incidence CRA at the maximum image height of the projection lens satisfies: 0.85 < CRA < 1. Satisfying the above range limits the projection lens to have a smaller CRA, so that the brightness uniformity of the projection picture of the projection lens is better.

[0100] In some embodiments, the projection lens satisfies the condition: 18mm < f < 20mm, 50mm < TTL < 60mm, 2.5 < Fno < 2.6, 10mm < IH < 12mm, 30° < FOV < 35°; wherein 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, IH represents the real image height corresponding to the maximum field of view FOV of the projection lens, and FOV represents the maximum field of view of the projection lens. Satisfying the above condition means that the projection lens provided by the embodiments of the present application at least has the characteristics of large image, miniaturization, etc.

[0101] In some embodiments, the lens material 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 six lenses in the projection lens provided by the present application can all be glass spherical lenses, which can improve the imaging stability of the projection lens under different temperature environments on the premise of meeting high pixels.

[0102] The present application will be further described in the following embodiments. In each embodiment, the thickness, curvature radius, and material selection of each lens in the projection lens are different, and the specific differences can be referred to the parameter table of each embodiment. The following embodiments are only preferred embodiments of the present application, but the embodiments of the present application are not limited to the following embodiments only, and any changes, substitutions, combinations or simplifications made without departing from the innovative points of the present application should be regarded as equivalent replacement methods, and are all included in the protection scope of the present application.

[0103] Embodiment 1

[0104] Please refer to Figures 1 to 4Fig. 1 is a structural schematic diagram of a projection lens 100 provided in Embodiment 1 of the present application, the projection lens 100 comprising, in sequence along an optical axis from a projection surface S0 to an image source surface S18, 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 prism L7, and a protective glass G1; meanwhile, a position-variable flat glass G2 is arranged between the prism L7 and the protective glass G1, and the flat glass G2 can be located in a first position or a second position by switching means. When the flat glass G2 is in the first position, the light path does not pass through the flat glass G2; when the flat glass G2 is in the second position, the flat glass G2 is located on the optical axis and between the prism L7 and the protective glass G1, and the flat glass G2 is parallel to the protective glass G1, and the light path passes through the flat glass G2.

[0105] The projection surface S0 has a first inclination angle of 15° with a vertical plane; the protective glass G1 and the image source surface S18 have a second inclination angle of 2° with a horizontal plane. It can be understood that the projection surface is arranged to be inclined relative to the first lens L1; the flat glass G2, the protective glass G1, and the image source surface S18 are arranged to be inclined relative to the prism L7.

[0106] The first lens L1 has positive focal power, the projection side surface S1 thereof is a convex surface, and the image source side surface S2 thereof is a convex surface.

[0107] The second lens L2 has negative focal power, the projection side surface S3 thereof is a convex surface, and the image source side surface S4 thereof is a concave surface.

[0108] The third lens L3 has positive focal power, the projection side surface S5 thereof is a concave surface, and the image source side surface S6 thereof is a convex surface.

[0109] The fourth lens L4 has negative focal power, the projection side surface S7 thereof is a concave surface, and the image source side surface S8 thereof is a concave surface.

[0110] The third lens L3 and the fourth lens L4 form a cemented lens group with focal power, i.e., the cemented surface S6 of the image source side surface of the third lens L3 and the projection side surface of the fourth lens L4.

[0111] The fifth lens L5 has positive focal power, the projection side surface S8 thereof is a concave surface, and the image source side surface S9 thereof is a convex surface.

[0112] The sixth lens L6 has positive focal power, the projection side surface S10 thereof is a convex surface, and the image source side surface S11 thereof is a convex surface.

[0113] The prism L7 can be a right-angled triangular prism, comprising an incident surface S12, a reflecting surface R0 and an exit surface S13; the incident surface S12, the reflecting surface R0 and the exit surface S13 of the prism are all planes. The reflecting surface of the prism forms a 45° angle with the optical axis of the incident surface and the exit surface of the prism. It can be understood that the incident surface S12 faces the projection surface, and the exit surface S13 faces the image source surface. The light ray is incident from the incident surface to the prism, reflected by the reflecting surface, and exits from the exit surface, and the angle between the incident surface and the exit surface is 90°.

[0114] The projection side surface S14 and the image source side surface S15 of the flat glass G2 are both planes;

[0115] The projection side surface S16 and the image source side surface S17 of the protective glass G1 are both planes;

[0116] The image source surface S18 is a plane.

[0117] 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.

[0118] The related parameters of the lenses in the projection lens 100 in Example 1 are shown in Table 1-1 and Table 1-2. When the flat glass G2 is in the first position (i.e. there is no flat glass between the prism L7 and the protective glass G1), the parameters are shown in Table 1-1; when the flat glass G2 is in the second position (i.e. there is a flat glass between the prism L7 and the protective glass G1), the parameters are shown in Table 1-2.

[0119] Table 1-1

[0120]

[0121] Table 1-2

[0122]

[0123] As shown in the table, when the flat glass G2 is in the first position, the distance between the projection surface S0 and the first lens L1 on the optical axis is 159.612 mm; when the flat glass G2 is in the second position, the distance between the projection surface S0 and the first lens L1 on the optical axis is 193.388 mm. It can be understood that the corresponding optimal projection surface distance will be farther after the addition of the flat glass.

[0124] Figure 5 The field curvature curve of Example 1 is shown, which represents the degree of curvature of light rays of different wavelengths on the meridional image surface and the sagittal image surface, the horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the field curvature of the meridional image surface and the sagittal image surface is controlled within ±0.1 mm, which indicates that the projection lens can well correct the field curvature.

[0125] Figure 6 F-Tan(Theta) distortion curve of the projection lens of Example 1 is shown, which represents the F-Tan(Theta) distortion of light rays at different field angles on the imaging plane, the horizontal axis represents the F-Tan(Theta) distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the F-Tan(Theta) distortion of the projection lens is controlled within-1%~0, which shows that the projection lens can well correct the distortion.

[0126] Figure 7 The axial aberration curve of Example 1 is shown, which represents the aberration of each wavelength on the optical axis at the imaging plane, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the figure, the offset of the axial aberration is controlled within-0.06mm~0.02mm, which shows that the projection lens can better correct the axial aberration.

[0127] Figure 8 The axial aberration curve of Example 1 is shown, which represents the aberration of each wavelength on the optical axis at the imaging plane, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the figure, the offset of the axial aberration is controlled within-0.06mm~0.02mm, which shows that the projection lens can better correct the axial aberration.

[0128] Figure 9 The relative illumination curve of Example 1 is shown, which represents the relative illumination value at 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 88% at the maximum half field angle, which shows that the projection lens has very good relative illumination.

[0129] Example 2

[0130] Please refer to Figures 10 to 13 , which is a structural schematic diagram of the projection lens 200 provided in Example 2 of the present application. Compared with Example 1, the main difference is that the image source side surface S7 of the fourth lens L4 is a convex surface; the optical parameters such as the curvature radius and the lens thickness of each lens surface are different.

[0131] The related parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2-1 and Table 2-2.

[0132] Table 2-1

[0133]

[0134] Table 2-2

[0135]

[0136] As shown in the table, when the flat glass G2 is in the first position, the distance between the projection surface S0 and the first lens L1 on the optical axis is 157.451 mm; when the flat glass G2 is in the second position, the distance between the projection surface S0 and the first lens L1 on the optical axis is 191.079 mm. It can be understood that the corresponding optimal projection surface distance will be farther after the flat glass is added.

[0137] Figure 14 The field curvature curve of Example 2 is shown, which represents the curvature of the meridional image surface and the sagittal image surface of light rays of different wavelengths, the horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the field curvature of the meridional image surface and the sagittal image surface is controlled within ±0.1 mm, which shows that the projection lens can well correct the field curvature.

[0138] Figure 15 The F-Tan(Theta) distortion curve of Example 2 is shown, which represents the F-Tan(Theta) distortion of light rays at different field angles on the imaging surface, the horizontal axis represents the F-Tan(Theta) distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the F-Tan(Theta) distortion of the projection lens is controlled within -1%~0, which shows that the projection lens can well correct the distortion.

[0139] Figure 16 The axial aberration curve of Example 2 is shown, which represents the axial aberration of each wavelength on the optical axis at the imaging surface, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the figure, the offset of the axial aberration is controlled within -0.06 mm~0.03 mm, which shows that the projection lens can well correct the axial aberration.

[0140] Figure 17 The axial aberration curve of Example 2 is shown, which represents the axial aberration of each wavelength on the optical axis at the imaging surface, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the figure, the offset of the axial aberration is controlled within -0.06 mm~0.03 mm, which shows that the projection lens can well correct the axial aberration.

[0141] Figure 18The relative illumination curve of embodiment 2 is shown, which represents the relative illumination values of different field angles on the imaging surface, 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 at the maximum half field angle is still greater than 90%, which shows that the projection lens has very good relative illumination.

[0142] Embodiment 3

[0143] Please refer to Figures 19 to 22 , which is a structural schematic diagram of the projection lens 300 provided in embodiment 3 of the present application. Compared with embodiment 1, the main difference is that the image source side surface S2 of the first lens L1 is a concave surface; the optical parameters such as the curvature radius and the lens thickness of each lens surface are different.

[0144] The related parameters of each lens in the projection lens 300 in embodiment 3 are shown in Tables 3-1 and 3-2.

[0145] Table 3-1

[0146]

[0147] Table 3-2

[0148]

[0149] As shown in the table, when the flat glass G2 is in the first position, the distance between the projection surface S0 and the first lens L1 on the optical axis is 162.210mm; when the flat glass G2 is in the second position, the distance between the projection surface S0 and the first lens L1 on the optical axis is 195.991mm. It can be understood that after the flat glass is added, the corresponding optimal projection surface distance will be farther.

[0150] Figure 23 The field curvature curve of embodiment 3 is shown, which represents the curvature degree of light rays of different wavelengths on the meridional image surface and the sagittal image surface, the horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the field curvature of the meridional image surface and the sagittal image surface is controlled within ±0.1mm, which shows that the projection lens can well correct the field curvature.

[0151] Figure 24 The F-Tan(Theta) distortion curve of embodiment 3 is shown, which represents the F-Tan(Theta) distortion of light rays at different field angles on the imaging surface, the horizontal axis represents the F-Tan(Theta) distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the F-Tan(Theta) distortion of the projection lens is controlled within-1%~0, which shows that the projection lens can well correct the distortion.

[0152] Figure 25 Fig. 3 shows an axial aberration curve of the projection lens of Example 3, which represents the aberration of the optical axis at the imaging plane at each wavelength, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the figure, the shift of the axial aberration is controlled within -0.04 mm ~ 0.01 mm, which indicates that the projection lens can better correct the axial aberration.

[0153] Figure 26 Fig. 4 shows a transverse chromatic aberration curve of the projection lens of Example 3, which represents the chromatic aberration at different image heights on the imaging plane at each wavelength relative to the central wavelength (0.53 μm), the horizontal axis represents the transverse chromatic 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 transverse chromatic aberration of the longest wavelength and the shortest wavelength is controlled within -1 μm ~ 3 μm, which indicates that the projection lens can better correct the chromatic aberration.

[0154] Figure 27 Fig. 5 shows a relative illumination curve of the projection lens of Example 3, which represents the relative illumination value at 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 90% at the maximum half field angle, which indicates that the projection lens has very good relative illumination.

[0155] Referring to Table 4, the optical properties of the above-mentioned embodiments are shown, including the effective focal length f of the projection lens, the total optical length TTL, the aperture value Fno, the real image height IHj corresponding to the maximum field angle when the flat glass is located at the first position, the chief ray angle CRAj at the maximum image height, and the maximum field angle FOVj, the real image height IHy corresponding to the maximum field angle when the flat glass is located at the second position, the chief ray angle CRAy at the maximum image height, and the maximum field angle FOVy, and the numerical value corresponding to each conditional expression in each embodiment.

[0156] Table 4

[0157]

[0158] In summary of the above embodiments, the projection lens provided by the present application realizes clear imaging at two different projection distances through switching of the flat glass, completes the switching of the close-up and the long shot, and effectively improves the convenience and safety of driving. At the same time, through reasonable configuration of each lens surface and reasonable matching of optical power, the imaging quality of the projection lens is improved, the aberration is reduced, the projection quality of the projection lens is improved, and the lens has one or more advantages such as small distortion, small CRA, uniform illumination, high imaging quality, etc.

[0159] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like 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 expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0160] The above-described embodiments only express several implementation manners of the present application, which are described in a more specific and detailed manner, but cannot be understood as a limitation on the patent scope of the present application. It should be noted that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, 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 lenses with optical power, characterized in that, In order from the projection surface to the image source surface along the optical axis, the projection lens comprises: a first lens with positive focal power, a projection side surface of which is a convex surface; a second lens with negative focal power, a projection side surface of which is a convex surface and an image source side surface of which is a concave surface; a third lens with positive focal power, a projection side surface of which is a concave surface and an image source side surface of which is a convex surface; a fourth lens with negative focal power, a projection side surface of which is a concave surface; a fifth lens with positive focal power, a projection side surface of which is a concave surface and an image source side surface of which is a convex surface; a sixth lens with positive focal power, a projection side surface of which is a convex surface and an image source side surface of which is a convex surface; a prism comprising an incident surface, a reflection surface and an exit surface, all of which are flat surfaces, light rays entering the prism from the incident surface, being reflected by the reflection surface and exiting from the exit surface along the optical axis; the reflection surface forms an angle of 45° with the optical axis of the incident surface and the optical axis of the exit surface; a protective glass, a projection side surface of which is a flat surface and an image source side surface of which is a flat surface; a flat glass is arranged between the prism and the protective glass and can be switched between a first position and a second position; when the flat glass is in the first position, the light path does not pass through the flat glass; when the flat glass is in the second position, the flat glass is arranged on the optical axis and between the prism and the protective glass, the flat glass is parallel to the protective glass, and the light path passes through the flat glass; the back focal length BFL of the projection lens and the effective focal length f of the projection lens satisfy: 0.2 < BFL / f < 0.

25.

2. The projection lens according to claim 1, characterized in that the projection surface has a first inclination angle with a vertical plane; the protective glass and the image source surface have a second inclination angle with a horizontal plane.

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

4. The projection lens of claim 1, wherein when the flat glass is in the first position, the distance CT0 from the projection surface to the first lens satisfies: 155mm < CT0 < 165mm; when the flat glass is in the second position, the distance CT0 from the projection surface to the first lens satisfies: 190mm < CT0 < 200mm.

5. 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: -2.4 < f2 / f < -1.

6. The projection lens of claim 1, wherein the real image height IH corresponding to the maximum field angle of the projection lens and the aperture value Fno of the projection lens satisfy: 4mm < IH / Fno < 4.5mm.

7. The projection lens of claim 1, wherein the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 1 < f5 / f < 1.

5.

8. The projection lens of claim 1, wherein, the projection side surface curvature radius R5 of the third lens and the image source side surface curvature radius R6 of the third lens satisfy: 1 < (R5+R6) / (R5-R6) < 2.

1.

9. The projection lens of claim 1, wherein, the projection side surface half sagittal height SAG11 of the first lens, the image source side surface half sagittal height SAG12 of the first lens and the central thickness CT1 of the first lens satisfy: -0.3 < (SAG12-SAG11) / CT1 < -0.

1.

10. The projection lens of claim 1, wherein, The projection-side surface half-aperture radius DM11 of the first lens and the image source-side surface half-aperture radius DM62 of the sixth lens satisfy: 0.9<DM11 / DM62<1.3.

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