projection lens

Abstract

The application provides a projection lens, which comprises successively along the optical axis from the projection surface to the image source surface: a first lens with positive focal length, the projection side surface of which is a convex surface and the image source side surface of which is a concave surface; a second lens with positive focal length, the projection side surface of which is a convex surface and the image source side surface of which is a convex surface; a third lens with negative focal length, the projection side surface of which is a concave surface and the image source side surface of which is a concave surface; a fourth lens with negative focal length, the projection side surface of which is a concave surface and the image source side surface of which is a concave surface; a fifth lens with positive focal length, the projection side surface of which is a convex surface and the image source side surface of which is a convex surface; a sixth lens with positive focal length, the projection side surface of which is a convex surface and the image source side surface of which is a convex surface; a prism; and a protective glass. The projection lens provided by the application has one or more advantages of preventing sunlight from flowing back, large aperture, small distortion and the like.

Description

Projection lens Technical Field

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

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

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

[0004] The technical solution adopted in this invention is as follows:

[0005] A projection lens, comprising, along the optical axis from the projection surface to the image source surface, the following components in sequence:

[0006] The first lens with positive optical power has a convex projection-side surface and a concave image-source-side surface;

[0007] The second lens with positive optical power has a convex projection-side surface and a convex image-source-side surface;

[0008] The third lens with negative optical power has a concave projection side surface and a concave image source side surface.

[0009] The fourth lens with negative optical power has a concave projection side surface and a concave image source side surface.

[0010] The fifth lens with positive optical power has a convex projection side surface and a convex image source side surface.

[0011] The sixth lens with positive optical power has a convex projection side surface and a convex image source side surface.

[0012] A prism, including an incident surface, a reflecting surface, and an exit surface that are all planar. Light enters the prism along the optical axis from the incident surface, is reflected by the reflecting surface, and exits from the exit surface. The reflecting surface forms an angle of 45° with the optical axes of the incident surface and the exit surface respectively.

[0013] A protective glass, whose projection-side surface and image-source-side surface are both planar.

[0014] The projection surface has a first inclination angle with respect to the vertical plane; the protective glass and the image-source surface have a second inclination angle with respect to the horizontal plane.

[0015] The combined focal length f123 of the first lens, second lens, and third lens and the combined focal length f456 of the fourth lens, fifth lens, and sixth lens satisfy: -15.5 < f123 / f456 < -4.5.

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

[0017] Further preferably, the combined focal length f23 of the second lens and third lens and the effective focal length f of the projection lens satisfy: -1.2 < f23 / f < -0.8.

[0018] Further preferably, the clear aperture semi-diameter d12 on the image-source side surface of the sixth lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 1.1 < 2×d12 / IH < 1.5.

[0019] Further preferably, the overall optical length TTL of the projection lens and the effective focal length f of the projection lens satisfy: 2.7 < TTL / f < 3.8.

[0020] Further preferably, the overall optical length TTL of the projection lens, the true image height IH corresponding to the maximum field angle of the projection lens, and the maximum field angle FOV of the projection lens satisfy: 0.1 / ° < TTL / IH / FOV < 0.25 / °.

[0021] Further preferably, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 0.85 < f2 / f < 1.3; the curvature radius R3 of the projection-side surface of the second lens and the effective focal length f of the projection lens satisfy: 0.55 < R3 / f < 0.9; the curvature radius R4 of the image-source-side surface of the second lens and the effective focal length f of the projection lens satisfy: -8 < R4 / f < -2.5.

[0022] Further preferably, the central thickness CT4 of the fourth lens and the central thickness CT5 of the fifth lens satisfy: 0.32 < CT4 / CT5 < 1.

[0023] Further preferably, the radius of curvature R11 of the projection-side surface of the sixth lens and the radius of curvature R12 of the image-source-side surface of the sixth lens satisfy: -1.1 <R11 / R12<-0.4。

[0024] Further preferably, the radius of curvature R7 of the projection side surface of the fourth lens and the radius of curvature R8 of the image source side surface of the fourth lens satisfy: -0.2<(R7+R8) / (R7-R8)<0.17.

[0025] The projection lens provided by this invention, through specific surface shape matching and reasonable optical power distribution, can improve the imaging quality of the projection lens, reduce aberrations, and enhance the projection quality, giving the lens one or more advantages such as preventing sunlight backflow, large aperture, low distortion, high resolution, and low cost. Simultaneously, the tilt of the projection surface and image source surface gives the system a large depth of field, which is beneficial for lens assembly and improving the overall yield rate. Attached Figure Description

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

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

[0028] Figure 2 is a schematic diagram of the projection lens in Embodiment 1 of the present invention.

[0029] Figure 3 is a field curvature curve of the projection lens in Embodiment 1 of the present invention.

[0030] Figure 4 is an F-Tan (Theta) distortion curve of the projection lens in Embodiment 1 of the present invention.

[0031] Figure 5 is a chromatic aberration curve of the projection lens in Embodiment 1 of the present invention.

[0032] Figure 6 is a relative illumination curve of the projection lens in Embodiment 1 of the present invention.

[0033] Figure 7 is a schematic diagram of the projection lens in Embodiment 2 of the present invention.

[0034] Figure 8 is a schematic diagram of the projection lens in Embodiment 2 of the present invention.

[0035] Figure 9 is a field curvature curve of the projection lens in Embodiment 2 of the present invention.

[0036] Figure 10 is an F-Tan (Theta) distortion curve of the projection lens in Embodiment 2 of the present invention.

[0037] Figure 11 is a chromatic aberration curve of the projection lens in Embodiment 2 of the present invention.

[0038] Figure 12 is a relative illumination curve of the projection lens in Embodiment 2 of the present invention.

[0039] Figure 13 is a schematic diagram of the projection lens in Embodiment 3 of the present invention.

[0040] Figure 14 is a schematic diagram of the projection lens in Embodiment 3 of the present invention.

[0041] Figure 15 is a field curvature curve of the projection lens in Embodiment 3 of the present invention.

[0042] Figure 16 is an F-Tan (Theta) distortion curve of the projection lens in Embodiment 3 of the present invention.

[0043] Figure 17 is a chromatic aberration curve of the projection lens in Embodiment 3 of the present invention.

[0044] Figure 18 is a relative illumination curve of the projection lens in Embodiment 3 of the present invention.

[0045] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0046] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of embodiments of this application and are not intended to limit the scope of this application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0047] It should be noted that in this specification, the terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of the invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0048] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not strictly to scale.

[0049] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the subject is called the object-side surface of the lens, and the surface of each lens closest to the imaging plane is called the image-side surface of the lens.

[0050] It should also be understood that the terms "comprising," "including," "having," "containing," and / or "comprising," when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features, not individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0051] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formal sense unless expressly so specified herein.

[0052] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0053] This invention provides a projection lens, which consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a prism, and a protective glass, arranged sequentially along the optical axis from the projection surface to the image source surface.

[0054] Specifically, the first lens may have positive optical power, its projection-side surface may be convex, and its image-source-side surface may be concave. The second lens may have positive optical power, its projection-side surface may be convex, and its image-source-side surface may be convex. The third lens may have negative optical power, its projection-side surface may be concave, and its image-source-side surface may be concave. The fourth lens may have negative optical power, its projection-side surface may be concave, and its image-source-side surface may be concave. The fifth lens may have positive optical power, its projection-side surface may be convex, and its image-source-side surface may be convex. The sixth lens may have positive optical power, its projection-side surface may be convex, and its image-source-side surface may be convex.

[0055] The prism can be a right-angled triangular prism, including an incident surface, a reflection surface, and an exit surface; its incident surface, reflection surface, and exit surface are all flat surfaces. The reflection surface of the prism forms a 45° angle with the optical axes of the incident surface and the exit surface of the prism respectively. It can be understood that the incident surface faces the projection surface, and the exit surface faces the image source surface. Light rays enter the prism from the incident surface, are reflected by the reflection surface, and exit from the exit surface. The angle between the incident surface and the exit surface is 90°. Setting the prism can change the optical path direction, bend the optical path, make the direction of the incident light perpendicular to the arrangement direction of multiple lenses, and reduce the overall thickness of the optical system.

[0056] The protective glass has flat surfaces on both the projection side and the image source side. The protective glass plays a role in protecting the projection lens, preventing the photosensitive chip from being damaged, and can improve the impact resistance and scratch resistance of the projection lens.

[0057] In some embodiments, the second lens and the third lens can be glued together to form a glued lens group with optical power, which can effectively correct the chromatic aberration of the projection lens, reduce the eccentricity sensitivity of the projection lens, balance the aberration of the projection lens, and improve the imaging quality of the projection lens; it can also reduce the assembly sensitivity of the projection lens, thereby reducing the processing difficulty of the projection lens and improving the assembly yield of the projection lens.

[0058] In some embodiments, the projection lens may further include an aperture stop, and the aperture stop may be located between the third lens and the fourth lens. It can be understood that the aperture stop is used to limit the amount of incident light to change the brightness of the image.

[0059] In some embodiments, the projection surface has a first inclination angle with the vertical plane, and the first inclination angle is 14° to 16°; the protective glass and the image source surface have a second inclination angle with the horizontal plane, and the second inclination angle is 1° to 3°. It can be understood that the projection surface is inclined relative to the first lens; the protective glass and the image source surface are inclined relative to the prism.

[0060] In some embodiments, the combined focal length f123 of the first lens, the second lens, and the third lens and the combined focal length f456 of the fourth lens, the fifth lens, and the sixth lens satisfy: -15.5 < f123 / f456 < -4.5. Meeting the above range, the refractive powers of the front and rear lens groups of the aperture stop cooperate with each other to achieve the purpose of correcting aberration, field curvature, and distortion, and improving the imaging quality of the projection lens.

[0061] In some embodiments, the combined focal length f23 of the second lens and the third lens and the effective focal length f of the projection lens satisfy: -1.2 < f23 / f < -0.8. Meeting the above range, the second lens and the third lens are glued to form a glued lens group, and reasonably limiting the proportion of the optical power of the glued lens group is beneficial to reducing chromatic aberration and spherical aberration and improving the imaging quality.

[0062] In some embodiments, the clear aperture radius d12 of the image source side surface of the sixth lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 1.1 < 2×d12 / IH < 1.5. Meeting the above range is beneficial for the chief ray of the marginal field to emerge parallel to the image source plane, which is beneficial for achieving a small CRA.

[0063] In some embodiments, the overall optical length TTL of the projection lens and the effective focal length f of the projection lens satisfy: 2.7 < TTL / f < 3.8. Meeting the above range can effectively limit the length of the lens, which is beneficial for miniaturizing the projection lens.

[0064] In some embodiments, the overall optical length TTL of the projection lens, the true image height IH corresponding to the maximum field angle of the projection lens, and the maximum field angle FOV of the projection lens satisfy: 0.1 / ° < TTL / IH / FOV < 0.25 / °. Meeting the above range can achieve a balance among a large image height, a long focal length, and miniaturization, and improve the imaging quality of the projection lens.

[0065] In some embodiments, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 0.85 < f2 / f < 1.3; the radius of curvature R3 of the projection side surface of the second lens and the effective focal length f of the projection lens satisfy: 0.55 < R3 / f < 0.9; the radius of curvature R4 of the image source side surface of the second lens and the effective focal length f of the projection lens satisfy: -8 < R4 / f < -2.5. Meeting the above range, the second lens has a positive optical power, which can complement the aberration with the front and rear optical systems, thereby achieving high imaging quality of the projection lens. At the same time, the second lens is a biconvex lens, which is beneficial for gently converging and focusing the front beam.

[0066] In some embodiments, the central thickness CT4 of the fourth lens and the central thickness CT5 of the fifth lens satisfy: 0.32 < CT4 / CT5 < 1. Meeting the above range can reduce the sensitivity of the system performance, while ensuring the lens processing performance and assembly stability, and improving the assembly yield. <s

[0067] In some embodiments, the radius of curvature R11 of the projection side surface of the sixth lens and the radius of curvature R12 of the image source side surface of the sixth lens satisfy: -1.1 < R11 / R12 < -0.4. Meeting the above range is beneficial for increasing the divergence degree of light, increasing the area of light entering the image source plane, achieving large target surface imaging of the lens, and improving the imaging quality of the projection lens.

[0068] 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: -0.2 < (R7 + R8) / (R7 - R8) < 0.17. Satisfying the above range can make the light path more stable, and at the same time can correct coma and field curvature, improve the flatness of imaging, and enhance the imaging quality of the projection lens.

[0069] In some embodiments, the combined focal length f123 of the first lens, the second lens and the third lens and the effective focal length f of the projection lens satisfy: -9 < f123 / f < -3.1. Satisfying the above range, by reasonably distributing the optical power of the first lens to the third lens, the deflection angle of the light at the front end of the lens is reduced, and the generation of various off-axis aberrations is reduced.

[0070] In some embodiments, the combined focal length f456 of the fourth lens, the fifth lens and the sixth lens and the effective focal length f of the projection lens satisfy: 0.5 < f456 / f < 0.8. Satisfying the above range, by reasonably distributing the optical power of the fourth lens to the sixth lens, the focal length of the projection lens is balanced, the correction ability of various aberrations at the rear end of the lens is improved, and the imaging quality of the projection lens is enhanced.

[0071] In some embodiments, the clear aperture semi-diameter d1 of the projection-side surface of the first lens and the clear aperture semi-diameter d12 of the image-source-side surface of the sixth lens satisfy: 1.5 < d1 / d12 < 2. Satisfying the above range, by reasonably setting the ratio of the apertures of the first and last lenses, the lens can have a smaller head size while having a larger imaging surface, and can better meet the balance of miniaturization and high pixels.

[0072] In some embodiments, the clear aperture semi-diameter d3 of the projection-side surface of the second lens and the radius of curvature R3 of the projection-side surface of the second lens satisfy: 1.1 < 2 × d3 / R3 < 1.5. Satisfying the above range can avoid the lens being super hemispherical and greatly reduce the processing difficulty of the second lens.

[0073] In some embodiments, the sagittal height SAG4 of the clear aperture of the image-source-side surface of the second lens, the sagittal height SAG3 of the clear aperture of the projection-side surface of the second lens and the central thickness CT2 of the second lens satisfy: -0.75 < (SAG4 - SAG3) / CT2 < -0.65. Satisfying the above range can reduce the difficulty of aberration correction in the edge field of view.

[0074] In some embodiments, the sagittal height SAG8 of the clear aperture on the image source side surface of the fourth lens, the sagittal height SAG7 of the clear aperture on the projection side surface of the fourth lens, and the central thickness CT4 of the fourth lens satisfy: 0.1 < (SAG8 - SAG7) / CT4 < 0.65. Satisfying the above range can control the surface shape of the projection surface of the fourth lens, which is beneficial to the manufacturing and molding of the fourth lens, reducing the defect rate. In addition, it can also prevent the surface shape from being too curved and complex, making the system field curvature tend to be balanced.

[0075] In some embodiments, the sagittal height SAG12 of the clear aperture on the image source side surface of the sixth lens, the sagittal height SAG11 of the clear aperture on the projection side surface of the sixth lens, and the central thickness CT6 of the sixth lens satisfy: -0.58 < (SAG12 - SAG11) / CT6 < -0.3. Satisfying the above range is beneficial to correcting the coma of the off-axis field of view and improving the imaging quality of the off-axis field of view of the projection lens.

[0076] In some embodiments, the total optical length TTL of the projection lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 4.2 < TTL / IH < 6.5. Satisfying the above range can better achieve the miniaturization of the lens, and at the same time ensure that the lens has a larger image plane under the condition of the same total length, so as to achieve high-definition projection imaging.

[0077] In some embodiments, the true image height IH corresponding to the maximum field angle of the projection lens, the effective focal length f of the projection lens, and the maximum field angle FOV of the projection lens satisfy: 0.9 < (IH / 2) / (f × tan(FOV / 2)) < 1.1. Satisfying the above range indicates that the optical distortion of the projection lens is well controlled, improving the resolution of the projection lens, while meeting the special distortion specifications, ensuring that the edge field of view occupies a larger proportion in the entire imaging picture, making the edge imaging of the field of view clearer.

[0078] In some embodiments, the maximum field angle FOV of the projection lens and the f-number Fno of the projection lens satisfy: 10° < FOV / Fno < 17°. Satisfying the above range is beneficial to increasing the light input of the lens, enabling the lens to achieve high-definition imaging in a dim environment.

[0079] In some embodiments, the true image height IH corresponding to the maximum field angle of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 1.1 < IH / EPD < 1.5. Satisfying the above range, while the projection lens has a large image plane, it can also ensure sufficient image plane brightness in the edge field of view, preventing the occurrence of vignetting phenomenon, thereby improving the imaging quality.

[0080] In some embodiments, the true image height IH corresponding to the maximum field angle of the projection lens and the effective focal length f of the projection lens satisfy: 0.45 < IH / f < 0.68. Meeting the above range can achieve a larger field angle and imaging range, and can achieve the characteristics of a large image plane while ensuring the depth of field of the projection lens, thereby improving the imaging quality of the optical system.

[0081] In some embodiments, the distance BL on the optical axis from the image source side surface of the sixth lens of the projection lens to the image source plane and the effective focal length f of the projection lens satisfy: 0.9 < BL / f < 1.4. Meeting the above range is beneficial to achieving a balance between obtaining good imaging quality and easy assembly, ensuring the imaging quality of the projection lens while avoiding interference between the lens and other components, and reducing the assembly process difficulty of the camera module.

[0082] In some embodiments, the effective focal length f of the projection lens, the maximum field angle FOV of the projection lens, and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 50° < f×FOV / IH < 59°. Meeting the above range is beneficial to achieving the balance of the field angle of the projection lens and large target surface imaging by reasonably restricting the relationship among the focal length, field angle, and image height of the projection lens, and better meeting the usage requirements of high image quality projection of the projection lens.

[0083] In some embodiments, the sum ΣCT of the central thicknesses of the six lenses and the optical total length TTL of the projection lens satisfy: 0.25 < ΣCT / TTL < 0.5. Meeting the above range can effectively compress the total length of the projection lens, and is beneficial to the structural design and production process of the projection lens.

[0084] In some embodiments, the clear aperture radius d1 of the projection side surface of the first lens, the true image height IH corresponding to the maximum field angle of the projection lens, and the maximum field angle FOV of the projection lens satisfy: 3.3 < d1 / IH / tan(FOV / 2) < 4.5. Meeting the above range can ensure the balance between the size of the projection lens, the field angle, and the image plane.

[0085] In some embodiments, the distance BL on the optical axis from the image source side surface of the sixth lens of the projection lens to the image source plane and the optical total length TTL of the projection lens satisfy: 0.31 < BL / TTL < 0.45. Meeting the above range is beneficial to achieving a short back focal length of the projection lens, and is beneficial to the miniaturization of the projection lens while ensuring sufficient space for the installation and focusing of optical components.

[0086] In some embodiments, the true image height IH corresponding to the maximum field angle of the projection lens and the f-number Fno of the projection lens satisfy: 4.2 mm < IH / Fno < 5.7 mm. Meeting the above range can increase the width of the light beam entering the projection lens, improve the relative illuminance, and avoid vignetting.

[0087] In some embodiments, the focal length f1 of the first lens and the effective focal length f of the projection lens satisfy: 1.7 < f1 / f < 2.9; the radius of curvature R1 of the projection-side surface of the first lens and the effective focal length f of the projection lens satisfy: 1.3 < R1 / f < 1.9; the radius of curvature R2 of the image-source side surface of the first lens and the effective focal length f of the projection lens satisfy: 5.2 < R2 / f < 10. Meeting the above range, the first lens expands the field angle range of the projection lens, is conducive to reducing the sensitivity of the projection lens, and realizes the miniaturized design of the projection lens. At the same time, the first lens is a meniscus positive lens. By reasonably configuring the ratio of the radius of curvature of the projection-side surface and the image-source side surface of the first lens to the effective focal length of the projection lens, the light passing amount of the projection lens can be increased, and the field range of the projection lens can be effectively expanded.

[0088] In some embodiments, the focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: -0.5 < f3 / f < -0.35; the radius of curvature R5 of the projection-side surface of the third lens and the effective focal length f of the projection lens satisfy: -8 < R5 / f < -2.5; the radius of curvature R6 of the image-source side surface of the third lens and the effective focal length f of the projection lens satisfy: 0.22 < R6 / f < 0.35. Meeting the above range, the third lens has the strongest negative focal power, can adjust the full-field light beam, deflect the large-field light beam, and turn the light beam to the transition lens group, which is conducive to realizing the large field of view of the projection lens. At the same time, the spherical aberration, chromatic aberration and field curvature of the optical system can be comprehensively balanced, which is conducive to reducing the processing difficulty of the third lens.

[0089] In some embodiments, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: -1.2 < f4 / f < -0.65; the radius of curvature R7 of the projection-side surface of the fourth lens and the effective focal length f of the projection lens satisfy: -2.1 < R7 / f < -0.85; the radius of curvature R8 of the image-source side surface of the fourth lens and the effective focal length f of the projection lens satisfy: 0.95 < R8 / f < 2.6. Meeting the above range, the fourth lens has a strong negative optical power, can adjust the principal ray angle, and reduce the lens distortion. At the same time, the fourth lens can have an appropriate optical power and surface shape, which is conducive to balancing the astigmatism and field curvature of the projection lens and improving the imaging quality of the projection lens.

[0090] In some embodiments, the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 0.58 < f5 / f < 0.75; the radius of curvature R9 of the projection-side surface of the fifth lens and the effective focal length f of the projection lens satisfy: 1.1 < R9 / f < 12.5; the radius of curvature R10 of the image-source-side surface of the fifth lens and the effective focal length f of the projection lens satisfy: -0.6 < R10 / f < -0.45. Meeting the above ranges, the fifth lens has a strong positive optical power, enabling full correction of various aberrations of the projection lens, improving the resolution, and achieving high resolution. At the same time, the fifth lens is a biconvex lens, which is beneficial for gently converging and converging the front beam, improving the imaging quality of the projection lens, and reducing the aperture of the rear lens, thus achieving miniaturization.

[0091] In some embodiments, the focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 1.1 < f6 / f < 1.5; the radius of curvature R11 of the projection-side surface of the sixth lens and the effective focal length f of the projection lens satisfy: 1.1 < R11 / f < 1.55; the radius of curvature R12 of the image-source-side surface of the sixth lens and the effective focal length f of the projection lens satisfy: -3 < R12 / f < -1.3. Meeting the above ranges, the sixth lens has a positive optical power, which is beneficial for converging light, reducing the light deflection angle, enabling a smooth transition of the light trend, and improving the projection quality of the projection lens. At the same time, effectively converging and converging the beam helps to achieve a small CRA and high imaging quality of the projection lens.

[0092] In some embodiments, the focal length f5 of the fifth lens and the focal length f6 of the sixth lens satisfy: 0.4 < f5 / f6 < 0.6. Meeting the above range is beneficial for expanding the width of the beam. After the light is refracted by the fifth lens and the sixth lens, the width of the beam entering the projection lens is larger, and then it can be fully transmitted to the high-pixel image-source surface, enabling the projection lens to obtain a wider field of view range. At the same time, it is also beneficial for the projection lens to achieve high-pixel and large-image-plane imaging.

[0093] In some embodiments, the central thickness CT1 of the first lens and the central thickness CT2 of the second lens satisfy: 0.6 < CT1 / CT2 < 0.95. Meeting the above range, the ratio of the central thicknesses of the first lens and the second lens is reasonably configured, enabling the first lens and the second lens to mutually regulate, and thus maintaining the characteristics of the miniaturization of the optical system.

[0094] In some embodiments, the radius of curvature R11 of the projection-side surface of the sixth lens and the radius of curvature R12 of the image-source-side surface of the sixth lens satisfy: -0.45 < (R11 + R12) / (R11 - R12) < 0.05. Meeting the above range is beneficial for suppressing the angle of the marginal field of view incident on the image-source surface, effectively transmitting more beams to the image-source surface, and at the same time balancing the field curvature and spherical aberration of the projection lens, improving the imaging quality of the projection lens.

[0095] In some embodiments, the projection lens satisfies the following conditional expressions: 18 mm < f < 23.7 mm; 26.7° < FOV < 34.5°; 8 mm < EPD < 9.6 mm; 51 mm < TTL < 71.4 mm; 2.1 < Fno < 2.5; 11.4 mm < IH < 11.6 mm; 2.1° < CRA < 11°; 17.8 mm < BL < 29.8 mm. In the above conditional expressions, f represents the effective focal length of the projection lens, TTL represents the total optical length of the projection lens, Fno represents the aperture value of the projection lens, CRA represents the principal ray angle of incidence at the maximum image height of the projection lens, IH represents the true image height corresponding to the maximum field angle of the projection lens, FOV represents the maximum field angle of the projection lens, EPD represents the entrance pupil diameter of the projection lens, and BL represents the distance from the image source side surface of the sixth lens of the projection lens to the image source plane on the optical axis. Meeting the above ranges, the projection lens has at least one or more advantages such as a large aperture, small distortion, and high resolution.

[0096] In some embodiments, the lens material of the projection lens provided by the present invention can be glass or plastic. When the lens material is plastic, the production cost can be effectively reduced. On the other hand, 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, all six lenses with optical power in the present invention adopt glass lenses. Adopting an all-glass structure can improve the stability of the lens under high and low temperature conditions.

[0097] In some embodiments, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens can adopt spherical lenses or aspherical lenses. 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, all six lenses with optical power in the present invention adopt spherical lenses.

[0098] The present invention will be further described below with multiple embodiments. In each embodiment, the thickness, curvature radius, and material selection of each lens in the projection lens are partially different. For specific differences, refer to the parameter table of each embodiment. The following embodiments are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited only by the following embodiments. Any other changes, substitutions, combinations, or simplifications made without departing from the innovative points of the present invention should be regarded as equivalent replacement methods and are included in the protection scope of the present invention.

[0099] Embodiment 1

[0100] Please refer to Figures 1 and 2, which show a schematic diagram of the structure of the projection lens 100 provided in Embodiment 1 of the present invention. The projection lens 100 includes, along the optical axis from the projection surface S0 to the image source surface S16, the following components in sequence: a first lens L1, a second lens L2, a third lens L3, an aperture ST, a fourth lens L4, a fifth lens L5, a sixth lens L6, a prism L7, and a protective glass G1.

[0101] The projection surface S0 has a first tilt angle of 15° with the vertical plane; the protective glass G1 and the image source surface S16 have a second tilt angle of 1.38° with the horizontal plane. It can be understood that the projection surface is tilted relative to the first lens L1; the protective glass G1 and the image source surface S16 are tilted relative to the prism L7.

[0102] Among them, the first lens L1 has positive optical power, its projection side surface S1 is convex, and its image source side surface S2 is concave.

[0103] The second lens L2 has positive optical power, its projection side surface S3 is convex, and its image source side surface is convex.

[0104] The third lens L3 has negative optical power, its projection side surface is concave, and its image source side surface S5 is concave.

[0105] The second lens L2 and the third lens L3 form a cemented lens group with optical power, that is, the cemented surface of the image source side surface of the second lens L2 and the projection side surface of the third lens L3 is S4.

[0106] The fourth lens L4 has negative optical power, its projection side surface S6 is concave, and its image source side surface S7 is concave.

[0107] The fifth lens L5 has positive optical power, its projection side surface S8 is convex, and its image source side surface S9 is convex.

[0108] The sixth lens L6 has positive optical power, its projection side surface S10 is convex, and its image source side surface S11 is convex.

[0109] Prism L7 can be a right-angled triangular prism, comprising an incident surface S12, a reflecting surface R0, and an exit surface S13; all three surfaces are planes. The reflecting surface of the prism forms a 45° angle with the optical axes of the incident and exit surfaces. It can be understood that the incident surface S12 faces the projection plane, and the exit surface S13 faces the image source plane. Light rays enter the prism from the incident surface, are reflected by the reflecting surface, and exit from the exit surface, with an angle of 90° between the incident and exit surfaces.

[0110] The projection-side surface S14 and the image source-side surface S15 of the protective glass G1 are both planar.

[0111] Image source plane S16 is a plane.

[0112] 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.

[0113] The relevant parameters of each lens in the projection lens 100 in Example 1 are shown in Table 1.

[0114] Table 1

[0115]

[0116] In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, lateral chromatic aberration curve, and relative illuminance curve of the projection lens 100 are shown in Figures 3 to 6, respectively.

[0117] Figure 3 shows the field curvature curve of Embodiment 1, which represents the degree of curvature of light of different wavelengths in the meridional and sagittal image planes. The horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field of view (unit: °). As can be seen from the figure, the field curvature of the meridional and sagittal image planes is controlled within -0.1 mm to 0 mm, indicating that the projection lens 100 can effectively correct the field curvature.

[0118] Figure 4 shows the F-Tan (Theta) distortion curve of Example 1, which represents the F-Tan (Theta) distortion at different image heights on the imaging plane. The horizontal axis represents the distortion value (unit: %), and the vertical axis represents the half field of view (unit: °). As can be seen from the figure, the F-Tan (Theta) distortion of the projection lens 100 is controlled within -2% to 0%, indicating that the distortion of the projection lens 100 is well corrected.

[0119] Figure 5 shows the transverse chromatic aberration curve of Example 1, which represents the chromatic aberration of each wavelength relative to the center wavelength (0.530 μm) at different image heights on the imaging plane. The horizontal axis represents the transverse chromatic aberration value of each wavelength relative to the center wavelength (unit: μm), and the vertical axis represents the normalized field of view. As can be seen from the figure, the transverse chromatic aberration of the longest and shortest wavelengths is controlled within -1 μm to 3 μm, indicating that the projection lens 100 can effectively correct the transverse chromatic aberration.

[0120] Figure 6 shows the relative illumination curve of Example 1, which represents the relative illumination value at different field-of-view 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, indicating that the projection lens 100 has good relative illumination.

[0121] Example 2

[0122] Please refer to Figures 7 and 8, which show a schematic diagram of the projection lens 200 provided in Embodiment 2 of the present invention. The main difference between this embodiment and Embodiment 1 is that the protective glass G1 and the image source surface S16 have a second tilt angle with the horizontal plane, and the second tilt angle is 1.403°; the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

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

[0124] Table 2

[0125]

[0126] In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, lateral chromatic aberration curve, and relative illuminance curve of the projection lens 200 are shown in Figures 9 to 12, respectively.

[0127] As can be seen from Figure 9, the field curvature of the meridional image plane and the sagittal image plane is controlled within -0.15mm to 0mm, indicating that the projection lens 200 can effectively correct the field curvature.

[0128] As can be seen from Figure 10, the F-Tan (Theta) distortion of the projection lens 200 is controlled within -2% to 0%, indicating that the distortion of the projection lens 200 is well corrected.

[0129] As can be seen from Figure 11, the vertical chromatic aberration of the longest and shortest wavelengths is controlled within -3μm to 5μm, indicating that the projection lens 200 can effectively correct the vertical chromatic aberration.

[0130] As can be seen from Figure 12, the relative illumination value of the projection lens is still greater than 95% at the maximum half field of view, indicating that the projection lens 200 has good relative illumination.

[0131] Example 3

[0132] Please refer to Figures 13 and 14, which show a schematic diagram of the projection lens 300 provided in Embodiment 3 of the present invention. The main difference between this embodiment and Embodiment 1 is that the protective glass G1 and the image source surface S16 have a second tilt angle with the horizontal plane, and the second tilt angle is 1.33°; the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0133] The relevant parameters of each lens in the projection lens 300 in Example 3 are shown in Table 3.

[0134] Table 3

[0135]

[0136] In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, lateral chromatic aberration curve, and relative illuminance curve of the projection lens 300 are shown in Figures 15 to 18, respectively.

[0137] As can be seen from Figure 15, the field curvature of the meridional image plane and the sagittal image plane is controlled within -0.1mm to 0.05mm, indicating that the projection lens 300 can effectively correct the field curvature.

[0138] As can be seen from Figure 16, the F-Tan (Theta) distortion of the projection lens 300 is controlled within -2% to 0%, indicating that the distortion of the projection lens 300 is well corrected.

[0139] As can be seen from Figure 17, the chromatic aberration of the longest and shortest wavelengths is controlled within -2μm to 6μm, indicating that the projection lens 300 can effectively correct the chromatic aberration.

[0140] As can be seen from Figure 18, the relative illumination value of the projection lens is still greater than 85% at the maximum half field of view, indicating that the projection lens 300 has good relative illumination.

[0141] Please refer to Tables 4-1 and 4-2 for the optical characteristics corresponding to the above embodiments, including the effective focal length f of the projection lens, the total optical length TTL, the aperture value Fno, the principal ray incident angle CRA at the maximum image height, the true image height IH corresponding to the maximum field of view, the maximum field of view FOV, the entrance pupil diameter EPD, the distance BL from the image source side surface of the sixth lens to the image source surface on the optical axis, and the values ​​corresponding to each conditional expression in each embodiment.

[0142] Table 4-1

[0143]

[0144] Table 4-2

[0145]

[0146]

[0147] In summary, the projection lens provided by this invention, through specific surface shape matching and reasonable optical power allocation, can improve the imaging quality of the projection lens, reduce aberrations, and enhance the projection quality, giving the lens one or more advantages such as preventing sunlight backflow, large aperture, low distortion, high resolution, and low cost. Simultaneously, the tilt of the projection surface and image source surface gives the system a large depth of field, which is beneficial for lens assembly and improving the overall yield rate.

[0148] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0149] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A projection lens, characterized in that, Along the optical axis, from the projection plane to the image source plane, it successively includes: a first lens with positive optical power, whose projection side surface is convex and whose image source side surface is concave; a second lens with positive optical power, whose projection side surface is convex and whose image source side surface is convex; a third lens with negative optical power, whose projection side surface is concave and whose image source side surface is concave; a fourth lens with negative optical power, whose projection side surface is concave and whose image source side surface is concave; a fifth lens with positive optical power, whose projection side surface is convex and whose image source side surface is convex; a sixth lens with positive optical power, whose projection side surface is convex and whose image source side surface is convex; a prism, including an incident surface, a reflecting surface and an exit surface that are all planar. Light enters the prism along the optical axis from the incident surface, is reflected by the reflecting surface, and exits from the exit surface; the reflecting surface forms an angle of 45° with the optical axes of the incident surface and the exit surface respectively; the projection plane has a first inclination angle with the vertical plane; the image source plane has a second inclination angle with the horizontal plane; the combined focal length f123 of the first lens, the second lens and the third lens and the combined focal length f456 of the fourth lens, the fifth lens and the sixth lens satisfy: -15.5 < f123 / f456 < -4.

5.

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

3. The projection lens according to claim 1, characterized in that, The combined focal length f23 of the second lens and the third lens and the effective focal length f of the projection lens satisfy: -1.2 < f23 / f < -0.

8.

4. The projection lens according to claim 1, characterized in that, The clear aperture radius d12 on the image source side surface of the sixth lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 1.1 < 2×d12 / IH < 1.

5.

5. The projection lens according to claim 1, characterized in that, The overall optical length TTL of the projection lens and the effective focal length f of the projection lens satisfy: 2.7 < TTL / f < 3.

8.

6. The projection lens according to claim 1, characterized in that, The overall optical length TTL of the projection lens, the true image height IH corresponding to the maximum field angle of the projection lens and the maximum field angle FOV of the projection lens satisfy: 0.1 / ° < TTL / IH / FOV < 0.25 / °.

7. The projection lens according to claim 1, characterized in that, The focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 0.85 < f2 / f < 1.3; the radius of curvature R3 of the projection side surface of the second lens and the effective focal length f of the projection lens satisfy: 0.55 < R3 / f < 0.9; the radius of curvature R4 of the image source side surface of the second lens and the effective focal length f of the projection lens satisfy: -8 < R4 / f < -2.

5.

8. The projection lens according to claim 1, characterized in that, The central thickness CT4 of the fourth lens and the central thickness CT5 of the fifth lens satisfy: 0.32 < CT4 / CT5 < 1.

9. The projection lens according to claim 1, characterized in that, The radius of curvature R11 of the projection side surface of the sixth lens and the radius of curvature R12 of the image source side surface of the sixth lens satisfy: -1.1 < R11 / R12 < -0.

4.

10. The projection lens according to claim 1, characterized in that, The radius of curvature R7 of the projection side surface of the fourth lens and the radius of curvature R8 of the image source side surface of the fourth lens satisfy: -0.2 < (R7 + R8) / (R7 - R8) < 0.17.

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