projection lens

Abstract

The application provides a projection lens, which comprises five lenses in sequence along an optical axis from a projection surface to an image source surface, and the five lenses comprise: a first lens with positive focal power, wherein an image source side surface of the first lens is a convex surface; a second lens with positive focal power, wherein a projection side surface of the second lens is a convex surface, and an image source side surface of the second lens is a concave surface; a third lens with negative focal power, wherein both a projection side surface and an image source side surface of the third lens are concave surfaces; a fourth lens with positive focal power, wherein both a projection side surface and an image source side surface of the fourth lens are convex surfaces; and a fifth lens with positive focal power, wherein an image source side surface of the fifth lens is a convex surface; wherein a maximum field of view FOV of the projection lens and an aperture value Fno of the projection lens satisfy: 17.5°<FOV / Fno<23.5°; and a curvature radius R2 of the image source side surface of the first lens and an effective focal length f of the projection lens satisfy:‑1.4<R2 / f<‑0.4. Through reasonable configuration of each lens surface type and reasonable matching of focal power, the application improves the imaging quality of the projection lens, reduces aberration, and improves the projection quality of the projection lens.

Description

Technical Field

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

[0002] As people's demands for driving experience continue to rise, the function of vehicle headlights is gradually shifting from simple illumination to multi-functional applications. Traditional smart headlights typically have tens of thousands of pixels, which also possess high precision, but relatively speaking, their beam control capability is slightly lower, unable to achieve the extremely precise area illumination of megapixel headlights. Megapixel headlights can usually support more complex intelligent lighting functions, such as projecting holiday greetings and weather information when stationary, and realizing multiple functions such as cornering light carpet illumination, distance indication, narrow road width indication, lane change indication, lane safety guidance, and pedestrian yielding when dynamic, effectively improving the driver's driving experience and attracting increasing attention from consumers.

[0003] The projection principle of intelligent headlights in vehicles is similar to that of traditional optical projection, both based on optical imaging technology and achieved through reflection and virtual imaging. The in-vehicle system drives the projector to generate an image based on real-time information, which is then reflected by a mirror and focused onto the projection lens, ultimately projecting the image precisely onto the road or environment. Existing lenses suffer from low pixel counts and poor image quality. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a projection lens with the advantage of high image quality.

[0005] This invention provides a projection lens comprising five lenses, arranged sequentially along the optical axis from the projection surface to the image source surface:

[0006] The first lens with positive optical power has a convex surface on its image source side.

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

[0008] The third lens with negative optical power has concave surfaces on both its projection side and image source side.

[0009] The fourth lens with positive optical power has convex surfaces on both its projection side and image source side.

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

[0011] Among them, the maximum field of view angle FOV of the projection lens and the aperture value Fno of the projection lens satisfy: 17.5° < FOV / Fno < 23.5°; the curvature radius R2 of the image source side surface of the first lens and the effective focal length f of the projection lens satisfy: -1.4 < R2 / f < -0.4.

[0012] Further preferably, the chief ray angle of incidence CRA at the maximum image height of the projection lens satisfies: 5.1° < CRA < 6.9°; the back focal length BFL of the projection lens and the total optical length TTL of the projection lens satisfy: 0.35 < BFL / TTL < 0.6.

[0013] Further preferably, the total optical length TTL of the projection lens and the true image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 4.2 < TTL / IH < 6.1.

[0014] Further preferably, the effective focal length f of the projection lens and the true image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 0.3 < IH / / f < 0.5.

[0015] Further preferably, the effective focal length f of the projection lens and the focal length f1 of the first lens satisfy: 1.2 < f1 / f < 1.7; the curvature radius R2 of the image source side surface of the first lens and the focal length f1 of the first lens satisfy: -0.8 < R2 / f1 < -0.3.

[0016] Further preferably, there is an aperture between the second lens and the third lens. The combined focal length f before of the lenses before the aperture and the effective focal length f of the projection lens satisfy: 1.1 < f before / f < 1.6; the combined focal length f after of the lenses after the aperture and the effective focal length f of the projection lens satisfy: 0.8 < f after / f < 2.1.

[0017] Further preferably, 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: 1 < R4 / f < 4.5; the curvature radius R10 of the image source side surface of the fifth lens and the effective focal length f of the projection lens satisfy: -1.8 < R10 / f < -1.1.

[0018] Further preferably, the curvature radius R4 of the image source side surface of the second lens and the curvature radius R5 of the projection side surface of the third lens satisfy: 1.5 < (R4 - R5) / (R4 + R5) < 4.4.

[0019] Further preferably, the clear aperture semi-diameter d4 of the image source side surface of the second lens and the sagittal height Sag4 of the clear aperture semi-diameter of the image source side surface of the second lens satisfy: 0.05 < Sag4 / d4 < 0.3; the clear aperture semi-diameter d10 of the image source side surface of the fifth lens and the sagittal height Sag10 of the clear aperture semi-diameter of the image source side surface of the fifth lens satisfy: -0.35 < Sag10 / d10 < -0.1.

[0020] Further preferably, the central thickness CT2 of the second lens, the central thickness CT3 of the third lens and the central thickness CT4 of the fourth lens satisfy: 0.1 < (CT2 + CT3) / CT4 < 0.4.

[0021] The projection lens provided by the present invention improves the imaging quality of the projection lens, reduces aberration, and improves the projection quality of the projection lens through the reasonable configuration of each lens surface type and the reasonable matching of optical power, so that the lens has one or more advantages such as small distortion, large aperture, large image plane, and high imaging quality. Brief Description of the Drawings

[0022] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0023] Figure 1 is a schematic structural diagram of the projection lens in Embodiment 1 of the present invention.

[0024] Figure 2 is the F-Tanθ distortion curve of the projection lens in Embodiment 1 of the present invention.

[0025] Figure 3 is the MTF curve graph of the projection lens in Embodiment 1 of the present invention.

[0026] Figure 4 is the relative illumination curve graph of the projection lens in Embodiment 1 of the present invention.

[0027] Figure 5 is a schematic structural diagram of the projection lens in Embodiment 2 of the present invention.

[0028] Figure 6 is the F-Tanθ distortion curve of the projection lens in Embodiment 2 of the present invention.

[0029] Figure 7 is the MTF curve graph of the projection lens in Embodiment 2 of the present invention.

[0030] Figure 8 is the relative illumination curve graph of the projection lens in Embodiment 2 of the present invention.

[0031] Figure 9 is a schematic structural diagram of the projection lens in Embodiment 3 of the present invention.

[0032] Figure 10 This is the F-Tanθ distortion curve of the projection lens in Embodiment 3 of the present invention.

[0033] Figure 11 This is the MTF curve of the projection lens in Embodiment 3 of the present invention.

[0034] Figure 12 This is a relative illumination curve of the projection lens in Embodiment 3 of the present invention.

[0035] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0036] 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.

[0037] 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.

[0038] 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.

[0039] In this paper, 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 projection plane is called the projection-side surface of the lens, and the surface of each lens closest to the image source plane is called the image source-side surface of the lens.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The projection lens provided in this embodiment of the invention has a total of five lenses, which are arranged sequentially from the projection surface to the image source surface along the optical axis as a first lens, a second lens, a third lens, a fourth lens, and a fifth lens.

[0044] In some embodiments, the first lens may have positive optical power, and its projection-side surface may be concave or convex, while its image-source-side surface is convex. The second lens may have positive optical power, and its projection-side surface may be convex, while its image-source-side surface is concave. The third lens may have negative optical power, and both its projection-side and image-source-side surfaces are concave. The fourth lens may have positive optical power, and both its projection-side and image-source-side surfaces are convex. The fifth lens may have positive optical power, and its projection-side surface may be concave or convex, while its image-source-side surface is convex.

[0045] In some embodiments, the projection lens may also include an aperture stop, which may be located between the second lens and the third lens. It is understood that the aperture stop is used to limit the amount of light entering the lens to change the brightness of the image. When the aperture stop is located between the second and third lenses, it facilitates the correction of aperture aberrations.

[0046] In some embodiments, a protective glass is also provided between the fifth lens and the image source surface. The protective glass serves to protect the light-emitting chip, preventing it from being damaged, while having almost no impact on the image quality of the projection lens.

[0047] In some embodiments, the maximum field of view angle FOV of the projection lens and the aperture value Fno of the projection lens satisfy: 17.5° < FOV / Fno < 23.5°; the radius of curvature R2 of the image source side surface of the first lens and the effective focal length f of the projection lens satisfy: -1.4 < R2 / f < -0.4. Satisfying the above ranges defines that the projection lens has a suitable field of view angle, aperture value, and the surface shape of the image source side surface of the first lens, can collect light at large angles, and obtain good imaging quality. More specifically, 19.94° < FOV / Fno < 21.48°; -1.19 < R2 / f < -0.52.

[0048] In some embodiments, the chief ray angle of incidence CRA at the maximum image height of the projection lens satisfies: 5.1° < CRA < 6.9°. Satisfying the above range defines that the projection lens has a smaller CRA, making the brightness uniformity of the projection screen of the projection lens better. More specifically, 5.68° < CRA < 6.45°.

[0049] In some embodiments, the back focal length BFL of the projection lens and the total optical length TTL of the projection lens satisfy: 0.35 < BFL / TTL < 0.6. Satisfying the above range can make the lens have a suitable back focus, ensure the imaging quality of the projection lens, avoid interference between the lens and other components, and reduce the assembly process difficulty of the lens module. More specifically, 0.37 < BFL / TTL < 0.56.

[0050] In some embodiments, the total optical length TTL of the projection lens and the true image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 4.2 < TTL / IH < 6.1. Satisfying the above conditions is beneficial to achieving the balance between the volume of the projection lens and the large image plane. More specifically, 4.61 < TTL / IH < 5.76.

[0051] In some embodiments, the effective focal length f of the projection lens and the true image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 0.3 < IH / f < 0.5. Satisfying the above range is beneficial to achieving the large image plane characteristic and improving the imaging quality of the projection lens. More specifically, 0.31 < IH / f < 0.48.

[0052] In some embodiments, the effective focal length f of the projection lens and the focal length f1 of the first lens satisfy: 1.2 < f1 / f < 1.7; the radius of curvature R2 of the object-side surface of the first lens and the focal length f1 of the first lens satisfy: -0.8 < R2 / f1 < -0.3. Meeting the above ranges, by reasonably setting the focal length of the first lens and the ratio of the radius of curvature of the object-side surface of the first lens, it is beneficial to slow down the degree of change in the refraction angle of the incident light and avoid excessive aberration caused by overly strong refraction changes. More specifically, 1.36 < f1 / f < 1.53; -1.03 < R2 / f1 < -0.18.

[0053] In some embodiments, an aperture is provided between the second lens and the third lens. The combined focal length ffront of the lenses located before the aperture and the effective focal length f of the projection lens satisfy: 1.1 < ffront / f < 1.6; the combined focal length fback of the lenses located after the aperture and the effective focal length f of the projection lens satisfy: 0.8 < fback / f < 2.1. Meeting the above ranges, by limiting the focal lengths of the lens groups before and after the aperture of the projection lens, the aberration generated by the lens groups before and after the aperture can be effectively corrected, improving the imaging quality of the projection lens. More specifically, 1.16 < ffront / f < 1.52; 1.15 < fback / f < 1.94.

[0054] In some embodiments, the radius of curvature R4 of the object-side surface of the second lens and the effective focal length f of the projection lens satisfy: 1 < R4 / f < 4.5; the radius of curvature R10 of the object-side surface of the fifth lens and the effective focal length f of the projection lens satisfy: -1.8 < R10 / f < -1.1. Meeting the above ranges, by controlling the radius of curvature of the object-side surface of the second lens and the radius of curvature of the object-side surface of the fifth lens within a reasonable range, the aberration can be effectively corrected, improving the projection quality of the projection lens. More specifically, 1.14 < R4 / f < 4.45; -1.62 < R10 / f < -1.29.

[0055] In some embodiments, the radius of curvature R4 of the object-side surface of the second lens and the radius of curvature R5 of the image-side surface of the third lens satisfy: 1.5 < (R4 - R5) / (R4 + R5) < 4.4. Meeting the above ranges is beneficial to the smooth trend of light rays and reduces the aberration correction pressure of the rear-end lenses of the projection lens. More specifically, 1.55 < (R4 - R5) / (R4 + R5) < 4.35.

[0056] In some embodiments, the clear aperture semi-diameter d4 of the image source side surface of the second lens and the sagittal height Sag4 of the clear aperture of the image source side surface of the second lens satisfy: 0.05 < Sag4 / d4 < 0.3; the clear aperture semi-diameter d10 of the image source side surface of the fifth lens and the sagittal height Sag10 of the clear aperture of the image source side surface of the fifth lens satisfy: -0.35 < Sag10 / d10 < -0.1. Meeting the above ranges helps to control the trend of light rays in the peripheral field of view and highlight the detailed information of the central field of view of the projection lens. More specifically, 0.05 < Sag4 / d4 < 0.21; -0.27 < Sag10 / d10 < -0.19.

[0057] In some embodiments, the central thickness CT2 of the second lens, the central thickness CT3 of the third lens, and the central thickness CT4 of the fourth lens satisfy: 0.1 < (CT2 + CT3) / CT4 < 0.4. Meeting the above ranges can balance the ratio of the central thicknesses of the front-end and rear-end lenses, which is beneficial to lens assembly and improve the qualified rate. More specifically, 0.21 < (CT2 + CT3) / CT4 < 0.36.

[0058] In some embodiments, the effective focal length f of the projection lens and the total optical length TTL satisfy: 1.8 < TTL / f < 2.3. Meeting the above ranges can achieve the long focal length characteristics and small volume of the lens, effectively limit the length of the lens, and is beneficial to reducing the volume of the projection lens. More specifically, 1.85 < TTL / f < 2.22.

[0059] In some embodiments, the effective focal length f of the projection lens and the focal length f2 of the second lens satisfy: f2 / f > 8; 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: 1 < R3 / f < 2.9. Meeting the above ranges limits the second lens to have an appropriate positive optical power and the surface shape of the projection side surface of the second lens, which is beneficial to converging light rays while reducing the light deflection angle, making the light trend transition smoothly, and improving the projection quality of the projection lens. More specifically, f2 / f > 8.79; 1.15 < R3 / f < 2.74.

[0060] In some embodiments, the effective focal length f of the projection lens and the focal length f3 of the third lens satisfy: -1.05 < f3 / f < -0.55; 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: -1.5 < R5 / f < -0.6; 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: 1.7 < R6 / f < 3.71. Satisfying the above ranges defines that the third lens has an appropriate negative optical power and the surface shape of the third lens, which can effectively balance lens aberrations and improve imaging quality. More specifically, -1.03 < f3 / f < -0.59; -1.34 < R5 / f < -0.71; 1.8 < R6 / f < 3.6.

[0061] In some embodiments, the effective focal length f of the projection lens and the focal length f4 of the fourth lens satisfy: 0.8 < f4 / f < 1.3; 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: 2.4 < R7 / f < 5.2; 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: -1.2 < R8 / f < -0.6. Satisfying the above ranges defines that the fourth lens has an appropriate positive optical power and the surface shape of the fourth lens, which is beneficial to converging light while reducing the light deflection angle, enabling the light to transition smoothly, and improving the projection quality of the projection lens. More specifically, 0.86 < f4 / f < 1.22; 2.56 < R7 / f < 5.06; -1.04 < R8 / f < -0.85.

[0062] In some embodiments, the effective focal length f of the projection lens and the focal length f5 of the fifth lens satisfy: 1.1 < f5 / f < 2.7. Satisfying the above range defines that the fifth lens has an appropriate positive optical power, which is beneficial to converging light while reducing the light deflection angle, enabling the light to transition smoothly, and improving the projection quality of the projection lens. More specifically, 1.13 < f5 / f < 2.49.

[0063] In some embodiments, the focal length f1 of the first lens and the focal length f4 of the fourth lens satisfy: 1.1 < f1 / f4 < 1.8. Satisfying the above conditions, by reasonably setting the ratio of the focal lengths of the first lens and the fourth lens in the lens, it is beneficial to the smooth transition of light, and at the same time corrects various aberrations of the projection lens, improving the imaging quality of the projection lens. More specifically, 1.13 < f1 / f4 < 1.76.

[0064] In some embodiments, the radius of curvature R2 of the image source side surface of the first lens and the radius of curvature R3 of the projection side surface of the second lens satisfy: -1.2 < R2 / R3 < -0.1. Meeting the above range, by reasonably setting the ratio of the radius of curvature of the image source side surface of the first lens and the radius of curvature of the projection side surface of the second lens, it is beneficial to slow down the change degree of the refraction angle of the incident light and avoid excessive aberration caused by too strong refraction change. More specifically, -1.03 < R2 / R3 < -0.18.

[0065] In some embodiments, the radius of curvature R6 of the image source side surface of the third lens and the radius of curvature R7 of the projection side surface of the fourth lens satisfy: 0.6 < R6 / R7 < 0.9. Meeting the above range, by reasonably setting the ratio of the radius of curvature of the image source side surface of the third lens and the radius of curvature of the projection side surface of the fourth lens, it is beneficial to slow down the change degree of the refraction angle of the incident light and avoid excessive aberration caused by too strong refraction change. More specifically, 0.69 < R6 / R7 < 0.8.

[0066] 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: -3.3 < (R5 - R6) / (R5 + R6) < -1.5. Meeting the above range can effectively correct aberration and improve the projection quality of the projection lens. More specifically, -2.96 < (R5 - R6) / (R5 + R6) < -1.73.

[0067] 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: 1.4 < (R7 - R8) / (R7 + R8) < 2.2. Meeting the above range can effectively correct aberration and improve the projection quality of the projection lens. More specifically, 1.42 < (R7 - R8) / (R7 + R8) < 2.01.

[0068] In some embodiments, the radius of curvature R9 of the projection side surface of the fifth lens and the radius of curvature R10 of the image source side surface of the fifth lens satisfy: 0.5 < (R9 - R10) / (R9 + R10) < 3.6. Meeting the above range can reduce spherical aberration and improve the relative illumination of the edge field of view at the same time. More specifically, 0.64 < (R9 - R10) / (R9 + R10) < 3.32.

[0069] In some embodiments, the radius of curvature R1 of the projection-side surface of the first lens and the radius of curvature R2 of the image-source-side surface of the first lens satisfy: 0.2 < (R1 + R2) / (R1 - R2) < 2.8. Satisfying the above range can reduce the angle between the incident light and the projection-side surface of the first lens, and can effectively reduce the working aperture of the first lens, which is beneficial to the miniaturization of the projection lens. More specifically, 0.3 < (R1 + R2) / (R1 - R2) < 2.7.

[0070] In some embodiments, the clear aperture semi-diameter d2 of the image-source-side surface of the first lens and the sagittal height Sag2 of the clear aperture of the image-source-side surface of the first lens satisfy: -0.3 < Sag2 / d2 < -0.05; the clear aperture semi-diameter d3 of the projection-side surface of the second lens and the sagittal height Sag3 of the clear aperture of the projection-side surface of the second lens satisfy: 0.05 < Sag3 / d3 < 0.3. Satisfying the above range helps to control the trend of the marginal field light and highlights the detailed information of the central field of the projection lens. More specifically, -0.24 < Sag2 / d2 < -0.06; 0.09 < Sag3 / d3 < 0.22.

[0071] In some embodiments, the total optical length TTL of the projection lens and the sum ∑CT of the central thicknesses of the first lens to the fifth lens along the optical axis satisfy: 2.3 < TTL / ∑CT < 3.5. Satisfying 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. More specifically, 2.55 < TTL / ∑CT < 3.13.

[0072] In some embodiments, the projection lens satisfies the conditional expressions: 27mm < f < 45mm, 28mm < EPD < 48mm, 58mm < TTL < 86mm, 0.8 < Fno < 1.1, 12.6mm < IH < 15.8mm, 17° < FOV < 22°, 29mm < BFL < 36mm; where f represents the effective focal length of the projection lens, EPD represents the entrance pupil diameter of the projection lens, TTL represents the total optical length of the projection lens, Fno represents the aperture value of the projection lens, IH represents the true image height corresponding to the maximum field angle of the projection lens, FOV represents the maximum field angle of the projection lens, and BFL represents the back focal length of the projection lens. Meeting the above conditions indicates that the projection lens provided by the embodiments of the present invention has at least the characteristics of a large aperture, a relatively large field angle, a relatively large image plane, a long back focal length, etc. More specifically, 29.51mm < f < 43.26mm, 31.07mm < EPD < 45.55mm, 64.69mm < TTL < 80.57mm, 0.9 < Fno < 1, 13.92mm < IH < 14.04mm, 17.98° < FOV < 20.42°, 30.7mm < BFL < 35.93mm.

[0073] In some embodiments, the lens material in 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, the second lens, the third lens, the fourth lens, and the fifth lens in the projection lens provided by the present invention can be glass lenses, and the first lens can be a plastic lens to reduce costs.

[0074] In some embodiments, the first lens, the second lens, the third lens, the fourth lens, and the fifth 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 achieving the miniaturization of the lens. More specifically, the second lens, the third lens, the fourth lens, and the fifth lens in the projection lens provided by the present invention can adopt spherical lenses, and the first lens can adopt an aspherical lens.

[0075] In each embodiment of the present invention, when the lens adopts an aspherical lens, the shapes of the aspherical surfaces of the projection lens satisfy the following equations:

[0076]

[0077] Where z is the distance between the surface and the vertex of the surface in the direction of the optical axis, h is the distance from the optical axis to the surface, c is the curvature of the vertex of the surface, K is the quadratic surface coefficient, and B, C, D, E, and F are the fourth, sixth, eighth, tenth, and twelfth order surface coefficients, respectively.

[0078] The present invention will be further described below with reference to several embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the projection are different; for specific differences, please refer to the parameter tables of each embodiment. The following embodiments are merely preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments. Any changes, substitutions, combinations, or simplifications made without departing from the innovative points of the present invention should be considered as equivalent substitutions and are included within the protection scope of the present invention.

[0079] Example 1

[0080] Please see Figure 1 The diagram shows a schematic of the projection lens 100 provided in Embodiment 1 of the present invention. The projection lens 100 includes, along the optical axis from the projection surface to the image source surface, the following components in sequence: a first lens L1, a second lens L2, an aperture ST, a third lens L3, a fourth lens L4, a fifth lens L5, and a protective glass G1.

[0081] The first lens L1 has positive optical power, and its projection side surface S1 and image source side surface S2 are both convex surfaces.

[0082] The second lens L2 has positive optical power, and its projection side surface S3 is convex, while its image source side surface S4 is concave.

[0083] The third lens L3 has negative optical power, and its projection side surface S5 and image source side surface S6 are both concave.

[0084] The fourth lens L4 has positive optical power, and both its projection side surface S7 and image source side surface S8 are convex.

[0085] The fifth lens L5 has positive optical power, and both its projection side surface S9 and image source side surface S10 are convex.

[0086] The projection-side surface S11 and the image source-side surface S12 of the protective glass G1 are both planar.

[0087] Image source plane S13 is a plane.

[0088] The second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are all glass spherical lenses; the first lens L1 is a plastic aspherical lens.

[0089] The relevant parameters of each lens in the projection lens 100 in Example 1 are shown in Table 1-1.

[0090] Table 1-1

[0091]

[0092]

[0093] The surface profile parameters of the aspherical lens of the projection lens 100 in Example 1 are shown in Table 1-2.

[0094] Table 1-2

[0095] Face number K B C D E F S1 4.15E+00 2.59E-06 3.93E-09 8.71E-13 -1.37E-14 2.69E-17 S2 -1.06E+01 4.83E-06 -1.89E-09 -2.96E-12 3.00E-14 -1.80E-17

[0096] Figure 2 The F-Tanθ distortion curve of Example 1 is shown, which represents the F-Tanθ distortion of light at different image heights on the imaging plane. The horizontal axis represents the F-Tanθ distortion value (unit: %), and the vertical axis represents the half field of view (unit: °). As can be seen from the figure, the F-Tanθ distortion of the projection lens is controlled within 0 to 0.5%, indicating that the projection lens 100 can effectively correct distortion, and the image compression in the edge angle region is relatively smooth, effectively improving the clarity of the unfolded image.

[0097] Figure 3 The MTF (Modulation Transfer Function) curve of Embodiment 1 is shown, which represents the lens imaging modulation at different spatial frequencies in each field of view. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. As can be seen from the figure, the MTF value of this embodiment is above 0.28 throughout the entire field of view. The MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens 100 has good imaging quality and good detail resolution.

[0098] Figure 4 The relative illumination curves for Example 1 are shown, representing the relative illumination values ​​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 98% at the maximum half-field angle, indicating that the projection lens 100 has good relative illumination.

[0099] Example 2

[0100] Please see Figure 5 The diagram shows a schematic 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 projection side surface S1 of the first lens L1 is concave; the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0101] The relevant parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2-1.

[0102] Table 2-1

[0103]

[0104] The surface profile parameters of the aspherical lens of the projection lens 200 in Example 2 are shown in Table 2-2.

[0105] Table 2-2

[0106] Face number K B C D E F S1 -1.55E+00 6.30E-06 4.95E-07 -2.59E-09 2.93E-12 2.01E-15 S2 -3.58E+01 -1.68E-04 1.75E-06 -7.61E-09 1.35E-11 -7.02E-15

[0107] from Figure 6 As can be seen, the F-Tanθ distortion in this embodiment is controlled within -1% to 0, indicating that the projection lens 200 can correct the distortion well, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the unfolded image.

[0108] from Figure 7 As can be seen, the MTF value of this embodiment is above 0.28 throughout the entire field of view. The MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens 200 has good imaging quality and good detail resolution.

[0109] from Figure 8 As can be seen, the relative illumination value of the projection lens is still greater than 95% at the maximum half field of view, indicating that the projection lens 200 has good relative illumination.

[0110] Example 3

[0111] Please see Figure 9 The diagram shows a schematic of the projection lens 300 provided in Embodiment 3 of the present invention. The main difference between this embodiment and Embodiment 1 is that the projection side surface S1 of the first lens L1 is concave; the projection side surface S9 of the fifth lens L5 is concave; and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0112] The relevant parameters of each lens in the projection lens 300 in Example 3 are shown in Table 3-1.

[0113] Table 3-1

[0114]

[0115] The surface profile parameters of the aspherical lens of the projection lens 300 in Example 3 are shown in Table 3-2.

[0116] Table 3-2

[0117] Face number K B C D E F S1 -1.65E+00 5.67E-06 4.94E-07 -2.61E-09 2.84E-12 2.16E-15 S2 -3.54E+01 -1.66E-04 1.75E-06 -7.59E-09 1.36E-11 -7.29E-15

[0118] from Figure 10As can be seen, the F-Tanθ distortion in this embodiment is controlled within -1% to 0, indicating that the projection lens 300 can correct the distortion well, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the unfolded image.

[0119] from Figure 11 As can be seen, the MTF value of this embodiment is above 0.2 throughout the entire field of view. The MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens 300 has good imaging quality and good detail resolution.

[0120] from Figure 12 As can be seen, the relative illumination value of the projection lens is still greater than 95% at the maximum half field of view, indicating that the projection lens 300 has good relative illumination.

[0121] Please refer to Table 4 for the optical characteristics corresponding to each of the above embodiments, including the effective focal length f, total optical length TTL, aperture value Fno, true image height IH corresponding to the maximum field of view, principal ray incident angle CRA at the maximum image height, and maximum field of view FOV, as well as the values ​​corresponding to each conditional expression in each embodiment.

[0122] Table 4

[0123]

[0124]

[0125] In summary, the projection lens provided by this invention improves the imaging quality, reduces aberrations, and enhances the overall image quality through the rational configuration of each lens surface and the appropriate combination of optical power. It also features a large aperture, which helps to increase brightness and light energy utilization; and a small CRA, resulting in good brightness uniformity of the projected image, minimal color difference and distortion, ensuring undistorted images and high image quality.

[0126] 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.

[0127] 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 comprising five lenses, characterized in that, From the projection plane to the image source plane along the optical axis, it successively includes: A first lens with positive optical power, and its image source side surface is convex. A second lens with positive optical power, its projection side surface is convex, and its image source side surface is concave. A third lens with negative optical power, and its projection side surface and image source side surface are both concave. A fourth lens with positive optical power, and its projection side surface and image source side surface are both convex. A fifth lens with positive optical power, and its image source side surface is convex. Among them, the maximum field angle FOV of the projection lens and the aperture value Fno of the projection lens satisfy: 17.5° < FOV / Fno < 23.5°; the curvature radius R2 of the image source side surface of the first lens and the effective focal length f of the projection lens satisfy: -1.4 < R2 / f < -0.4; 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.

1.

2. The projection lens according to claim 1, characterized in that, The main ray incident angle CRA at the maximum image height of the projection lens satisfies: 5.1° < CRA < 6.9°; the back focal length BFL of the projection lens and the total optical length TTL of the projection lens satisfy: 0.35 < BFL / TTL < 0.

6.

3. The projection lens according to claim 1, characterized in that, The maximum field angle FOV of the projection lens and the aperture value Fno of the projection lens satisfy: 19.94° < FOV / Fno < 21.48°; the curvature radius R2 of the image source side surface of the first lens and the effective focal length f of the projection lens satisfy: -1.19 < R2 / f < -0.52; 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: 4.61 < TTL / IH < 5.

76.

4. The projection lens according to claim 1, characterized in that, The effective focal length f of the projection lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 0.3 < IH / / f < 0.

5.

5. The projection lens according to claim 1, characterized in that, The effective focal length f of the projection lens and the focal length f1 of the first lens satisfy: 1.2 < f1 / f < 1.7; the curvature radius R2 of the image source side surface of the first lens and the focal length f1 of the first lens satisfy: -0.8 < R2 / f1 < -0.

3.

6. The projection lens according to claim 1, characterized in that, An aperture is provided between the second lens and the third lens. The combined focal length f before of the lenses before the aperture and the effective focal length f of the projection lens satisfy: 1.1 < f before / f < 1.6; the combined focal length f after of the lenses after the aperture and the effective focal length f of the projection lens satisfy: 0.8 < f after / f < 2.

1.

7. The projection lens according to claim 1, characterized in that, 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: 1 < R4 / f < 4.5; the curvature radius R10 of the image source side surface of the fifth lens and the effective focal length f of the projection lens satisfy: -1.8 < R10 / f < -1.

1.

8. The projection lens according to claim 1, characterized in that, The curvature radius R4 of the image source side surface of the second lens and the curvature radius R5 of the projection side surface of the third lens satisfy: 1.5 < (R4 - R5) / (R4 + R5) < 4.

4.

9. The projection lens according to claim 1, characterized in that, The clear aperture semi-diameter d4 of the image source side surface of the second lens and the sagittal height Sag4 of the clear aperture of the image source side surface of the second lens satisfy: 0.05 < Sag4 / d4 < 0.3; the clear aperture semi-diameter d10 of the image source side surface of the fifth lens and the sagittal height Sag10 of the clear aperture of the image source side surface of the fifth lens satisfy: -0.35 < Sag10 / d10 < -0.

1.

10. The projection lens according to claim 1, characterized in that, The central thickness CT2 of the second lens, the central thickness CT3 of the third lens, and the central thickness CT4 of the fourth lens satisfy: 0.1 < (CT2 + CT3) / CT4 < 0.4.

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