Projection lens

Abstract

The invention provides a projection lens, which comprises five lenses from a projection surface to an image source surface along an optical axis in sequence: a first lens with positive focal power, a second lens with negative focal power, a third lens with positive focal power and a fourth lens with negative focal power, the surface of the projection side of the second lens is a convex surface, and the surface of the image source side of the second lens is a concave surface; the projection side surface and the image source side surface of the third lens are concave surfaces; the projection side surface and the image source side surface of the fourth lens are convex surfaces; the surface of the image source side of the fifth lens is a convex surface; wherein the maximum field angle FOV of the projection lens and the aperture value Fno of the projection lens meet the following conditions: 17.5 degree lt; an FOV / Fnot; 23.5 DEG C; the curvature radius R2 of the surface of the image source side of the first lens and the effective focal length f of the projection lens meet the following conditions:-1.4 lt; r2 / flt; and-0.4. Through reasonable configuration of the surface types of the lenses and reasonable matching of the focal power, the imaging quality of the projection lens is improved, the aberration is reduced, and the projection quality of the projection lens is improved.

Description

Technical Field

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

[0002] As people's demand for driving experience continues to increase, the function of vehicle headlights has gradually shifted from single lighting to multi-functional applications. Traditional smart headlights are usually megapixels and have high precision, but relatively speaking, their beam control ability is slightly lower, and they cannot achieve extremely fine regional lighting like megapixel headlights. Million-pixel headlights can usually support more complex intelligent lighting functions. For example, when static, they can project holiday greetings, weather and other functions. When dynamic, they can realize multiple functions such as cornering light blanket lighting, vehicle distance prompts, narrow road width indication, lane change prompts, lane safety guidance, and pedestrian courtesy. It can effectively improve the driver's driving experience and is being paid attention to by more and more consumers.

[0003] The projection principle of vehicle smart headlights is similar to traditional optical projection, both based on optical imaging technology, and realized through reflection and virtual imaging. The on-board system drives the projector to generate images based on real-time information, which are reflected and focused to the projection lens through the reflector, and finally the image is accurately projected onto the road or environment. Existing lenses have problems such as low pixels and low imaging quality. Summary of the invention

[0004] In view of the above problems, an object of the present invention is to provide a projection lens having the advantage of high imaging quality.

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

[0006] The first lens has positive refractive power and its image source side surface is convex;

[0007] A second lens having positive refractive power, whose projection side surface is convex and whose image source side surface is concave;

[0008] A third lens having negative optical power, wherein both the projection side surface and the image source side surface thereof are concave surfaces;

[0009] a fourth lens having positive refractive power, wherein both its projection side surface and its image source side surface are convex surfaces;

[0010] a fifth lens element having positive refractive power, whose image source side surface is convex;

[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 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.

[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 radius of curvature 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, a diaphragm is provided between the second lens and the third lens, and the combined focal length ffront of the lenses before the diaphragm 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 after the diaphragm and the effective focal length f of the projection lens satisfy: 0.8 < fback / f < 2.1.

[0017] Further preferably, 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: 1 < R4 / f < 4.5; 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: -1.8 < R10 / f < -1.1.

[0018] Further preferably, the radius of curvature R4 of the image source side surface of the second lens and the radius of curvature 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 combination of optical powers, enabling the lens to have 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 apparent and be readily understood from the following description of the embodiments in conjunction with the accompanying 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] Fig. 9 is a schematic structural diagram of the projection lens in Embodiment 3 of the present invention.

[0032] Fig.10 is the F-Tanθ distortion curve of the projection lens in Example 3 of the present invention.

[0033] Fig.11 This is an MTF curve diagram of the projection lens in Example 3 of the present invention.

[0034] Fig.12 This is a relative illumination curve diagram of the projection lens in Example 3 of the present invention.

[0035] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0036] In order to better understand the present application, a more detailed description will be made of various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of the embodiments of the present application, and are not intended to limit the scope of the present 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 expressions of first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching of the present invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0038] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of explanation. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are only examples and are not drawn strictly to scale.

[0039] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface 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 position of the concave surface 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 surface is called the projection side surface of the lens, and the surface of each lens closest to the image source surface is called the image source side surface of the lens.

[0040] It should also be understood that the terms "comprises", "including", "having", "includes" 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. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0041] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this article have the same meaning as commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that terms (such as terms defined in commonly used dictionaries) should be interpreted as having the same meaning as their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0042] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0043] The projection lens provided by the embodiment of the present invention comprises five lenses in total, which are a first lens, a second lens, a third lens, a fourth lens and a fifth lens in order from the projection plane to the image source plane along the optical axis.

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

[0045] In some embodiments, the projection lens may further include an aperture, and the aperture may be located between the second lens and the third lens. It is understood that the aperture is used to limit the amount of light entering to change the brightness of the image. When the aperture is located between the second lens and the third lens, it is convenient to correct the aperture aberration.

[0046] In some embodiments, a protective glass is provided between the fifth lens and the image source surface. The protective glass protects the light-emitting chip and prevents the light-emitting chip from being damaged, while having almost no effect on the imaging quality of the projection lens.

[0047] In some embodiments, the maximum field of view (FOV) of the projection lens and the f-number (Fno) of the projection lens satisfy: 17.5° < FOV / Fno < 23.5°; the radius of curvature R2 of the object-side surface of the first lens and the effective focal length f of the projection lens satisfy: -1.4 < R2 / f < -0.4. Meeting the above ranges defines that the projection lens has an appropriate field of view, f-number, and the surface shape of the object-side surface of the first lens, enabling it to 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 (CRA) at the maximum image height of the projection lens satisfies: 5.1° < CRA < 6.9°. Meeting the above range defines that the projection lens has a smaller CRA, resulting in better brightness uniformity of the projection screen of the projection lens. 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. Meeting the above range can make the lens have an appropriate back focus, ensuring the imaging quality of the projection lens while avoiding interference with other components and reducing 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 of the projection lens satisfy: 4.2 < TTL / IH < 6.1. Meeting the above conditions is beneficial for 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 of the projection lens satisfy: 0.3 < IH / f < 0.5. Meeting the above range is beneficial for 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, a diaphragm is provided between the second lens and the third lens. The combined focal length ffront of the lenses located before the diaphragm and the effective focal length f of the projection lens satisfy: 1.1 < ffront / f < 1.6; the combined focal length frear of the lenses located after the diaphragm and the effective focal length f of the projection lens satisfy: 0.8 < frear / f < 2.1. Meeting the above ranges, by limiting the focal lengths of the lens groups before and after the diaphragm of the projection lens, the aberration generated by the lens groups before and after the diaphragm can be effectively corrected, improving the imaging quality of the projection lens. More specifically, 1.16 < ffront / f < 1.52; 1.15 < frear / 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 range is beneficial for 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 for lens assembly and improving the qualification 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 overall 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 for 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 for converging light rays while reducing the light deflection angle, enabling the light rays to 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 for the light to transition smoothly, and at the same time correct 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 degree of change of the refraction angle of the incident light and avoid excessive aberration caused by overly strong refraction changes. 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 degree of change of the refraction angle of the incident light and avoid excessive aberration caused by overly strong refraction changes. 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 aberrations 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 aberrations 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 at the same time improve the relative illumination of the edge field of view. 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, which can effectively reduce the working aperture of the first lens and is beneficial to the miniaturization of the projection lens. More specifically, 0.3 < (R1 + R2) / (R1 - R2) < 2.7.

[0070] In some embodiments, the half-aperture d2 of the light passing through the image-source-side surface of the first lens and the sagittal height Sag2 of the half-aperture of the light passing through the image-source-side surface of the first lens satisfy: -0.3 < Sag2 / d2 < -0.05; the half-aperture d3 of the light passing through the projection-side surface of the second lens and the sagittal height Sag3 of the half-aperture of the light passing through 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 formula: 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 of view angle of the projection lens, FOV represents the maximum field of view angle of the projection lens, and BFL represents the back focal length of the projection lens. 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 of view 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 due to 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 realizing 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] Among them, 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 surface vertex, K is the quadratic surface coefficient, B, C, D, E, and F are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order surface coefficients respectively.

[0078] The present invention is further described below in multiple 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 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 to the following embodiments. Any other changes, substitutions, combinations, or simplifications that do not deviate 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.

[0079] Example 1

[0080] See also Figure 1 , which is a schematic diagram of the structure of the projection lens 100 provided in Embodiment 1 of the present invention, wherein the projection lens 100 includes, in sequence from the projection surface to the image source surface along the optical axis: 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 refractive power, and its projection side surface S1 and image source side surface S2 are both convex surfaces;

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

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

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

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

[0086] The projection side surface S11 and the image source side surface S12 of the protection glass G1 are both planes;

[0087] The image source surface 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 parameters of the aspheric 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 surface, the horizontal axis represents the F-Tanθ distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). It can be seen from the figure that the F-Tanθ distortion of the projection lens is controlled within 0 to 0.5%, indicating that the projection lens 100 can correct the distortion well, the image compression in the edge angle area is relatively gentle, and the clarity of the expanded image is effectively improved.

[0097] Figure 3 The MTF (Modulation Transfer Function) curve of Example 1 is shown, which represents the imaging modulation degree of the lens at different spatial frequencies under each field of view, the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.28 in the entire field of view, and the MTF curve decreases evenly and smoothly 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 ability.

[0098] Figure 4 The relative illumination curve of Example 1 is shown, which represents the relative illumination values ​​at different viewing angles on the imaging plane, the horizontal axis represents the half viewing angle (unit: °), and the vertical axis represents the relative illumination (unit: %). It can be seen from the figure that the relative illumination value of the projection lens is still greater than 98% at the maximum half viewing angle, indicating that the projection lens 100 has a very good relative illumination.

[0099] Example 2

[0100] See also Figure 5 , shown is a schematic diagram of the structure of a projection lens 200 provided in Example 2 of the present invention. Compared with Example 1, the main differences of this embodiment are: the projection side surface S1 of the first lens L1 is a concave surface; the optical parameters such as the curvature radius of each lens surface and the lens thickness 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 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 It can be seen that the F-Tanθ distortion of this embodiment is controlled within the range of -1% to 0, which means that the projection lens 200 can correct the distortion well, and the image compression in the edge angle area is relatively gentle, which effectively improves the clarity of the expanded image.

[0108] from Figure 7 It can be seen that the MTF value of this embodiment is above 0.28 in the entire field of view, and the MTF curve decreases evenly and smoothly 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 capability.

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

[0110] Example 3

[0111] See also Fig. 9 , which is a schematic diagram of the structure of a projection lens 300 provided in Example 3 of the present invention. Compared with Example 1, this embodiment mainly differs in that: the projection side surface S1 of the first lens L1 is a concave surface; the projection side surface S9 of the fifth lens L5 is a concave surface; and the optical parameters such as the curvature radius of each lens surface and the lens thickness 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 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 Fig.10It can be seen that the F-Tanθ distortion of this embodiment is controlled within the range of -1% to 0, which means that the projection lens 300 can correct the distortion well, and the image compression in the edge angle area is relatively gentle, which effectively improves the clarity of the expanded image.

[0119] from Fig.11 It can be seen that the MTF value of this embodiment is above 0.2 in the entire field of view, and the MTF curve decreases evenly and smoothly 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 capability.

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

[0121] Please refer to Table 4, which shows 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 real image height IH corresponding to the maximum field of view angle, the chief ray incident angle CRA at the maximum image height, and the maximum field of view angle FOV, as well as the numerical values ​​corresponding to each conditional expression in each embodiment.

[0122] Table 4

[0123]

[0124]

[0125] In summary of the above embodiments, the projection lens provided by the present invention improves the imaging quality of the projection lens, reduces aberrations, and improves the imaging quality of the projection lens through the reasonable configuration of the lens surface shapes and the reasonable matching of the optical focal length. At the same time, it has a large aperture, which is conducive to improving brightness and increasing the utilization rate of light energy; it has a small CRA, the brightness uniformity of the projected image is good, and it has small chromatic aberration and distortion, so that the image is not deformed and the imaging quality is good.

[0126] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0127] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A projection lens, comprising five lenses, characterized in that: In order from the projection surface to the image source surface along the optical axis, it includes successively: A first lens with positive optical power, whose image source side surface is convex; A second lens with positive optical power, whose projection side surface is convex and image source side surface is concave; A third lens with negative optical power, whose projection side surface and image source side surface are both concave; A fourth lens with positive optical power, whose projection side surface and image source side surface are both convex; A fifth lens with positive optical power, whose image source side surface is convex; Wherein, 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.

2. The projection lens according to claim 1, characterized in that: The principal 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 overall 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 overall 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.

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 of view angle of the projection lens satisfy: 0.3 < IH / / f < 0.

5.

5. The projection lens according to claim 1, wherein: 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, wherein: A diaphragm is provided between the second lens and the third lens. The combined focal length f_front of the lenses before the diaphragm and the effective focal length f of the projection lens satisfy: 1.1 < f_front / f < 1.6; the combined focal length f_back of the lenses after the diaphragm and the effective focal length f of the projection lens satisfy: 0.8 < f_back / f < 2.

1.

7. The projection lens according to claim 1, wherein: 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, wherein: 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, wherein: The clear aperture semi-diameter d4 of the image source side surface of the second lens and the sagitta 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 sagitta Sag10 of the clear aperture semi-diameter 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, wherein: The center thickness CT2 of the second lens, the center thickness CT3 of the third lens, and the center thickness CT4 of the fourth lens satisfy: 0.1<(CT2+CT3) / CT4<0.4.

Images