projection lens

Abstract

The application provides a projection lens, which comprises six lenses in sequence along an optical axis from a projection surface to an image source surface, and the six lenses comprise: a first lens with positive optical power; a second lens with negative optical power, wherein an image source side surface of the second lens is a concave surface; a third lens with positive optical power, wherein a projection side surface of the third lens is a concave surface and an image source side surface of the third lens is a convex surface; a fourth lens with negative optical power, wherein an image source side surface of the fourth lens is a concave surface; a fifth lens with positive optical power, wherein both the projection side surface and the image source side surface of the fifth lens are convex surfaces; and a sixth lens with positive optical power, wherein an image source side surface of the sixth lens is a convex surface; wherein a radius of curvature R5 of the projection side surface of the third lens and a radius of curvature R12 of the image source side surface of the sixth lens satisfy: -0.8<(R5-R12) / (R5+R12)<0. The application improves the imaging quality of the projection lens, reduces aberration and improves the projection quality of the projection lens by reasonable configuration of the surface type of each lens and reasonable matching of optical power.

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 increase, the use of in-vehicle projection lenses in intelligent driving is growing, and their status in the automotive industry is constantly rising. Head-up display (HUD), also known as a car head-up display system, uses optical reflection to project driving assistance information, navigation information, inspection and control information, and ADAS information onto the windshield or about 2 meters in front of the driver, above the tip of the hood. It can also display warnings from various driving assistance systems, such as lane departure warnings and pedestrian avoidance warnings from night vision systems with pedestrian recognition capabilities. This avoids drivers frequently looking down at the instrument panel or in-vehicle screens while driving, playing a significant role in enhancing driving safety.

[0003] However, projection lenses used in vehicle HUDs on the market have defects such as dark corners in the projected image and insufficient brightness at the projection surface, resulting in unclear images, which make it difficult to meet the usage requirements. 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 six lenses, arranged sequentially along the optical axis from the projection surface to the image source surface:

[0006] A first lens with positive optical power;

[0007] The second lens with negative optical power has a concave surface on the image source side.

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

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

[0010] The fifth lens with positive optical power has convex surfaces on both its projection side and image source side.

[0011] The sixth lens, which has positive optical power, has a convex surface on its image source side.

[0012] The radius of curvature R5 of the projection side surface of the third lens and the radius of curvature R12 of the image source side surface of the sixth lens satisfy: -0.8<(R5-R12) / (R5+R12)<0.

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

[0014] Further preferably, the effective focal length f of the projection lens, the maximum field angle FOV, and the true image height IH corresponding to the maximum field angle satisfy: 0.95 < (IH / 2) / (f × tan(FOV / 2)) < 1.

[0015] Further preferably, the effective focal length f of the projection lens and the back focal length BFL of the projection lens satisfy: BFL / f > 1.4.

[0016] Further preferably, the effective focal length f of the projection lens and the focal length f3 of the third lens satisfy: f3 / f > 1.9.

[0017] Further preferably, the effective focal length f of the projection lens and the combined focal length f456 of the fourth lens, the fifth lens, and the sixth lens satisfy: 0.8 < f456 / f < 2.2.

[0018] Further preferably, the effective focal length f of the projection lens and the radius of curvature R5 of the projection-side surface of the third lens satisfy: R5 / f < -0.5.

[0019] Further preferably, the effective focal length f of the projection lens and the radius of curvature R12 of the image-source-side surface of the sixth lens satisfy: R12 / f < -1.

[0020] Further preferably, the focal length f5 of the fifth lens and the radius of curvature R12 of the image-source-side surface of the sixth lens satisfy: 0.1 < R5 / R12 < 1.1.

[0021] Further preferably, the clear aperture semi-diameter d5 of the projection-side surface of the third lens and the sagittal height Sag5 of the projection-side surface of the third lens satisfy: -0.4 < Sag5 / d5 < -0.1; the clear aperture semi-diameter d12 of the image-source-side surface of the sixth lens and the sagittal height Sag12 of the image-source-side surface of the sixth lens satisfy: -0.5 < Sag12 / d12 < -0.1.

[0022] 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 by reasonably configuring the surface shapes of each lens and rationally matching the optical powers, 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

[0023] 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, wherein:

[0024] Figure 1 This is a schematic diagram of the projection lens in Embodiment 1 of the present invention.

[0025] Figure 2 This is the F-Tanθ distortion curve of the projection lens in Embodiment 1 of the present invention.

[0026] Figure 3 This is an MTF curve of the projection lens in Embodiment 1 of the present invention.

[0027] Figure 4 This is the vertical chromatic aberration curve of the projection lens in Embodiment 1 of the present invention.

[0028] Figure 5 This is a relative illumination curve of the projection lens in Embodiment 1 of the present invention.

[0029] Figure 6 This is a schematic diagram of the projection lens in Embodiment 2 of the present invention.

[0030] Figure 7 This is the F-Tanθ distortion curve of the projection lens in Embodiment 2 of the present invention.

[0031] Figure 8 This is the MTF curve of the projection lens in Embodiment 2 of the present invention.

[0032] Figure 9 This is the vertical chromatic aberration curve of the projection lens in Embodiment 2 of the present invention.

[0033] Figure 10 This is a relative illumination curve of the projection lens in Embodiment 2 of the present invention.

[0034] Figure 11 This is a schematic diagram of the projection lens in Embodiment 3 of the present invention.

[0035] Figure 12 This is the F-Tanθ distortion curve of the projection lens in Embodiment 3 of the present invention.

[0036] Figure 13 This is the MTF curve of the projection lens in Embodiment 3 of the present invention.

[0037] Figure 14 This is the vertical chromatic aberration curve of the projection lens in Embodiment 3 of the present invention.

[0038] Figure 15 This is a relative illumination curve of the projection lens in Embodiment 3 of the present invention.

[0039] Figure 16 This is a schematic diagram of the projection lens in Embodiment 4 of the present invention.

[0040] Figure 17 This is the F-Tanθ distortion curve of the projection lens in Embodiment 4 of the present invention.

[0041] Figure 18 This is the MTF curve of the projection lens in Embodiment 4 of the present invention.

[0042] Figure 19 This is the vertical chromatic aberration curve of the projection lens in Embodiment 4 of the present invention.

[0043] Figure 20 This is a relative illumination curve of the projection lens in Embodiment 4 of the present invention.

[0044] Figure 21 This is a schematic diagram of the projection lens in Embodiment 5 of the present invention.

[0045] Figure 22 This is the F-Tanθ distortion curve of the projection lens in Embodiment 5 of the present invention.

[0046] Figure 23 This is the MTF curve of the projection lens in Embodiment 5 of the present invention.

[0047] Figure 24 This is the vertical chromatic aberration curve of the projection lens in Embodiment 5 of the present invention.

[0048] Figure 25 This is a relative illumination curve of the projection lens in Embodiment 5 of the present invention.

[0049] Figure 26 This is a schematic diagram of the projection lens in Embodiment 6 of the present invention.

[0050] Figure 27 This is the F-Tanθ distortion curve of the projection lens in Embodiment 6 of the present invention.

[0051] Figure 28 This is the MTF curve of the projection lens in Embodiment 6 of the present invention.

[0052] Figure 29 This is the vertical chromatic aberration curve of the projection lens in Embodiment 6 of the present invention.

[0053] Figure 30 This is a relative illumination curve of the projection lens in Embodiment 6 of the present invention.

[0054] Figure 31 This is a schematic diagram of the projection lens in Embodiment 7 of the present invention.

[0055] Figure 32 This is the F-Tanθ distortion curve of the projection lens in Embodiment 7 of the present invention.

[0056] Figure 33This is the MTF curve of the projection lens in Embodiment 7 of the present invention.

[0057] Figure 34 This is the vertical chromatic aberration curve of the projection lens in Embodiment 7 of the present invention.

[0058] Figure 35 This is a relative illumination curve of the projection lens in Embodiment 7 of the present invention. The following detailed description, in conjunction with the above-mentioned figures, will further illustrate the present invention. Detailed Implementation

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] The projection lens provided in this embodiment of the invention has a total of six 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, a fifth lens, and a sixth lens.

[0067] The first lens may have positive optical power, and its projection-side surface may be concave or convex, and its image-source-side surface may be concave or convex. The second lens may have negative optical power, and its projection-side surface may be concave or convex, while its image-source-side surface is concave. The third lens may have positive optical power, and its projection-side surface may be concave, while its image-source-side surface is convex. The fourth lens may have negative optical power, and its projection-side surface may be concave or convex, while its image-source-side surface is concave. The fifth lens may have positive optical power, and both its projection-side and image-source-side surfaces are convex. The sixth lens may have positive optical power, and its projection-side surface may be concave or convex, while its image-source-side surface is convex.

[0068] In some embodiments, the projection lens may also include an aperture stop, which may be located between the third and fourth lenses. 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 third and fourth lenses, it facilitates the correction of aperture aberrations.

[0069] In some embodiments, the projection lens may further include a reflective element and a protective glass, which are sequentially disposed along the optical axis between the sixth lens and the image source surface. The reflective element deflects the light beam emitted from the image source so that it enters the lens group at the front end of the projection lens, thereby reducing the overall optical length. For example, the reflective element may be a prism, a plane mirror placed at 45°, a beam splitter, a curved reflector, a reflective polarizer, etc. The protective glass protects the projection lens from damage to the light-emitting chip and improves the projection lens's impact and scratch resistance, while having almost no impact on the image quality of the projection lens.

[0070] In some embodiments, the radius of curvature R5 of the projection-side surface of the third lens and the radius of curvature R12 of the image-source-side surface of the sixth lens satisfy: -0.8 < (R5 - R12) / (R5 + R12) < 0. Satisfying this range reasonably defines the shapes of the projection-side surface of the third lens and the image-source-side surface of the sixth lens, which helps to balance higher-order aberrations of the projection lens and improve the imaging quality of the projection lens. More specifically, -0.57 < (R5 - R12) / (R5 + R12) < -0.01.

[0071] In some implementations, the principal ray incident angle CRA at the maximum image height of the projection lens satisfies: CRA < 2.1°. Meeting this range limits the projection lens to have a smaller CRA, resulting in better brightness uniformity of the projected image. More specifically, CRA < 2°.

[0072] In some implementations, the effective focal length f of the projection lens, the maximum field of view (FOV), and the corresponding true image height IH satisfy the following condition: 0.95 < (IH / 2) / (f × tan(FOV / 2)) < 1. Meeting this range allows for better control of the optical distortion of the projection lens, improving its resolution and achieving a better projection effect that is more suitable for human viewing.

[0073] In some implementations, the effective focal length f and the back focal length BFL of the projection lens satisfy the condition: BFL / f > 1.4. Meeting this range helps to achieve a balance between good image quality and an easily assembled optical back focal length, ensuring the image quality of the projection lens while avoiding interference between the lens and other components, and reducing the difficulty of lens module assembly. More specifically, 1.4 <BFL / f<2.4。

[0074] In some embodiments, the effective focal length f of the projection lens and the focal length f3 of the third lens satisfy: f3 / f > 1.9. Meeting the above range can endow the third lens with an appropriate positive optical power, which is conducive to converging light while reducing the light deflection angle, enabling the light path to transition smoothly and improving the projection quality of the projection lens. More specifically, 2 < f3 / f < 26.8.

[0075] In some embodiments, the effective focal length f of the projection lens and the combined focal length f456 of the fourth, fifth, and sixth lenses satisfy: 0.8 < f456 / f < 2.2. Meeting the above range can define an appropriate focal length for the lens group behind the aperture of the projection lens, effectively correcting the aberration generated by the lens group in front of the aperture and improving the imaging quality of the projection lens. More specifically, 1 < f456 / f < 2.

[0076] In some embodiments, the effective focal length f of the projection lens and the curvature radius R5 of the projection-side surface of the third lens satisfy: R5 / f < -0.5. The effective focal length f of the projection lens and the curvature radius R6 of the image-source-side surface of the third lens satisfy: -1.2 < R6 / f < -0.3. Meeting the above range can effectively correct aberration, reduce chromatic aberration, and improve the projection quality of the projection lens. More specifically, -2.5 < R5 / f < -0.6; -1.1 < R6 / f < -0.5.

[0077] In some embodiments, the effective focal length f of the projection lens and the curvature radius R12 of the image-source-side surface of the sixth lens satisfy: R12 / f < -1. Meeting the above range is conducive to increasing the imaging area, reducing chromatic aberration, and improving the imaging quality. More specifically, -3.5 < R12 / f < -1.1.

[0078] In some embodiments, the focal length f5 of the fifth lens and the curvature radius R12 of the image-source-side surface of the sixth lens satisfy: 0.1 < R5 / R12 < 1.1. Meeting the above range can reasonably define the ratio of the curvature radius of the projection-side surface of the third lens to the curvature radius of the image-source-side surface of the sixth lens, which helps to balance the aberration of the projection lens and improve the imaging quality of the projection lens. More specifically, 0.2 < R5 / R12 < 1.

[0079] In some embodiments, the clear aperture semi-diameter d5 of the projection side surface of the third lens and the sagittal height Sag5 of the clear aperture of the projection side surface of the third lens satisfy: -0.4 < Sag5 / d5 < -0.1; the clear aperture semi-diameter d12 of the image source side surface of the sixth lens and the sagittal height Sag12 of the clear aperture of the image source side surface of the sixth lens satisfy: -0.5 < Sag12 / d12 < -0.1. Meeting the above ranges helps to control the trend of light rays in the marginal field of view and highlight the detailed information of the central field of view of the projection lens. More specifically, -0.29 < Sag5 / d5 < -0.1; -0.47 < Sag12 / d12 < -0.12.

[0080] In some embodiments, the distance OD on the optical axis from the projection side surface of the first lens to the projection plane and the total optical length TTL of the projection lens satisfy: 1.5 < OD / TTL < 2. Meeting the above range enables the projection lens to achieve high-definition projection on a screen with a distance of 130 mm to 150 mm, meeting the requirements of the limited space inside the vehicle HUD. More specifically, 1.63 < OD / TTL < 1.76.

[0081] In some embodiments, the effective focal length f of the projection lens and the total optical length TTL satisfy: TTL / f < 6.7. Meeting the above range can achieve the telephoto characteristics and small volume of the lens, effectively limit the length of the lens, and is conducive to the miniaturization of the projection lens. More specifically, 3.9 < TTL / f < 6.7.

[0082] 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: 6.8 < TTL / IH < 9.6. Meeting the above conditions is conducive to achieving the balance between the volume and large image plane of the projection lens. More specifically, 7.5 < TTL / IH < 8.9.

[0083] In some embodiments, the maximum field of view angle FOV of the projection lens and the f-number Fno of the projection lens satisfy: 15.6° < FOV / Fno < 24.3°. Meeting the above range limits the projection lens to have an appropriate field of view angle and f-number, can collect light rays at large angles, and obtain good imaging quality. More specifically, 17.9° < FOV / Fno < 22.2°.

[0084] In some embodiments, the true image height IH corresponding to the maximum field of view angle of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 0.6 < IH / EPD < 1.8. Meeting the above range can increase the width of the light beam entering the projection lens, improve the relative illumination, and avoid vignetting. More specifically, 0.8 < IH / EPD < 1.6.

[0085] In some embodiments, the effective focal length f of the projection lens and the true image height IH corresponding to the maximum field angle satisfy: 0.3 < IH / f < 1. Meeting the above range is beneficial to achieving the characteristics of a large image plane and improving the imaging quality of the projection lens. More specifically, 0.5 < IH / f < 0.8.

[0086] In some embodiments, the effective focal length f of the projection lens and the focal length f1 of the first lens satisfy: 1.1 < f1 / f < 4.3. Meeting the above range, by reasonably setting the focal length of the first 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, 1.3 < f1 / f < 4.1.

[0087] In some embodiments, the effective focal length f of the projection lens and the focal length f2 of the second lens satisfy: -1.6 < f2 / f < -0.3. Meeting the above range can make the second lens have an appropriate negative optical power, effectively balance the lens aberration, and improve the imaging quality. More specifically, -1.3 < f2 / f < -0.5.

[0088] In some embodiments, the effective focal length f of the projection lens and the focal length f4 of the fourth lens satisfy: -2.6 < f4 / f < -0.4. Meeting the above range can make the fourth lens have an appropriate negative optical power, increase the imaging area of the lens, and improve the imaging quality. More specifically, -2.3 < f4 / f < -0.6.

[0089] In some embodiments, the effective focal length f of the projection lens and the focal length f5 of the fifth lens satisfy: 0.5 < f5 / f < 2.3. Meeting the above range can make the fifth lens have 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, 0.8 < f5 / f < 1.9.

[0090] In some embodiments, the effective focal length f of the projection lens and the focal length f6 of the sixth lens satisfy: 0.8 < f6 / f < 2.9. Meeting the above range can make the sixth lens have 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, 1.2 < f6 / f < 2.5.

[0091] In some embodiments, the effective focal length f of the projection lens and the radius of curvature R4 of the image source side surface of the second lens satisfy: 0.3 < R4 / f < 0.9. Meeting the above range can control the light to move smoothly, reduce the deflection degree of the light passing through the lens, reduce the difficulty of off-axis aberration correction, and improve the imaging quality of the projection lens. More specifically, 0.5 < R4 / f < 0.8.

[0092] In some embodiments, the effective focal length f of the projection lens and the radius of curvature R10 of the image source side surface of the fifth lens satisfy: -2.3 < R10 / f < -0.5. Satisfying the above range and controlling the radius of curvature of the image source side surface of the fifth lens within the above range is beneficial to reducing the difficulty of correcting the off-axis aberration of the projection lens. More specifically, -2 < R10 / f < -0.8.

[0093] In some embodiments, the focal length f3 of the third lens and the radius of curvature R5 of the projection side surface of the third lens satisfy: -0.9 < R5 / f3 < 0. Satisfying the above range and controlling the radius of curvature of the projection side surface of the third lens and the focal length of the third lens within a reasonable range can effectively correct aberration, reduce chromatic aberration, and improve the projection quality of the projection lens. More specifically, -0.87 < R5 / f3 < -0.02.

[0094] In some embodiments, the focal length f6 of the sixth lens and the radius of curvature R12 of the image source side surface of the sixth lens satisfy: R12 / f6 < -0.4. Satisfying the above range is beneficial to increasing the imaging area and the field angle. More specifically, -1.6 < R12 / f6 < -0.5.

[0095] 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 sixth lens along the optical axis respectively satisfy: 2.6 < TTL / ∑CT < 4.8. 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, 2.7 < TTL / ∑CT < 4.5.

[0096] In some embodiments, the distance CT23 between the second lens and the third lens on the optical axis and the central thickness CT3 of the third lens on the optical axis satisfy: 1.6 < CT23 / CT3 < 10.9. Satisfying the above range is beneficial to the structural design and production process of the projection lens on the premise of ensuring the imaging quality of the lens. More specifically, 1.6 < CT23 / CT3 < 9.6.

[0097] In some implementations, the projection lens satisfies the condition: 11.5mm <f<22.8mm,5.8mm<EPD<13.7mm,78mm<TTL<89mm,1.6<Fno<2.1,8.6mm<IH<11.8mm,28°<FOV<50°,BFL> 29.4mm; 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 of the projection lens, FOV represents the maximum field of view 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 in this embodiment of the invention has at least the characteristics of a large aperture, a large field of view, a large image plane, and a long back focal length. More specifically, 12.8mm <f<20.5mm,6.4mm<EPD<12.3mm,79.8mm<TTL<85.2mm,1.6<Fno<2.0,9.4mm<IH<10.8mm,29.8°<FOV<44.2°,29.4mm<BFL<29.6mm。

[0098] In some embodiments, the fourth lens and the fifth lens can be cemented together to form a cemented lens, which can effectively correct chromatic aberration of the projection lens, reduce the eccentricity sensitivity of the projection lens, balance the aberrations of the projection lens, and improve the imaging quality of the projection lens; it can also reduce the assembly sensitivity of the projection lens, thereby reducing the processing difficulty of the projection lens and improving the assembly yield of the projection lens.

[0099] 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, production costs can be effectively reduced. Conversely, when the lens material is glass, the low dispersion characteristic of glass itself can effectively correct geometric chromatic aberration of the optical system. More specifically, the first, second, fourth, fifth, and sixth lenses in the projection lens provided by the present invention can be glass lenses, and the third lens can be a plastic lens, thus reducing costs.

[0100] In some embodiments, the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens can be spherical lenses or aspherical lenses. Compared with spherical structures, aspherical structures can effectively reduce the aberrations of the optical system, thereby reducing the number of lenses and the size of the lenses, and better achieving lens miniaturization. More specifically, in the projection lens provided by the present invention, the first lens, second lens, fourth lens, fifth lens, and sixth lens can be spherical lenses, and the third lens can be an aspherical lens.

[0101] In various embodiments of the present invention, when an aspherical lens is used, the shapes of each aspherical surface of the projection lens satisfy the following equations:

[0102]

[0103] 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.

[0104] 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 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 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.

[0105] Example 1

[0106] Please see Figure 1 The diagram shows a schematic of the projection lens provided in Embodiment 1 of the present invention. The projection lens 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, a third lens L3, an aperture ST, a fourth lens L4, a fifth lens L5, a sixth lens L6, a reflective element G1, and a protective glass G2.

[0107] Among them, the first lens L1 has positive optical power, its projection side surface S1 is concave, and its image source side surface S2 is convex.

[0108] The second lens L2 has negative optical power, and its projection side surface S3 and image source side surface S4 are both concave.

[0109] The third lens L3 has positive optical power, and its projection side surface S5 is concave and its image source side surface S6 is convex.

[0110] The fourth lens L4 has negative optical power, and both its projection side surface S7 and image source side surface S8 are concave.

[0111] The fifth lens L5 has positive optical power, and both its projection side surface S8 and image source side surface S9 are convex.

[0112] The fourth lens L4 and the fifth lens L5 form a cemented lens group with positive optical power, that is, the cemented surface of the image source side surface of the fourth lens L4 and the projection side surface of the fifth lens L5 is S8.

[0113] The sixth lens L6 has positive optical power, and both its projection side surface S10 and image source side surface S11 are convex.

[0114] The projection-side surface S12 and the image source-side surface S13 of the reflective element G1 are both planar.

[0115] The projection-side surface S14 and the image source-side surface S15 of the protective glass G2 are both planar.

[0116] Image source plane S16 is a plane.

[0117] The first lens L1, the second lens L2, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are all glass spherical lenses; the third lens L3 is a plastic aspherical lens.

[0118] The relevant parameters of each lens in the projection lens in Example 1 are shown in Table 1-1.

[0119] Table 1-1

[0120]

[0121]

[0122] The surface profile parameters of the aspherical lens in the projection lens of Example 1 are shown in Table 1-2.

[0123] Table 1-2

[0124] Face number K B C D E F S5 7.25E-01 -6.60E-05 1.21E-06 -3.71E-08 -4.01E-10 1.33E-11 S6 -7.36E+00 -3.32E-04 2.47E-06 3.71E-08 -2.29E-09 2.48E-11

[0125] 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 -5% to 0, and the image compression in the edge angle region is relatively smooth, effectively improving the clarity of the unfolded image.

[0126] Figure 3 The MTF (Modulation Transfer Function) curve of Example 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 example is above 0.3 throughout the entire field of view. Within the range of 0–60 lp / mm, the MTF curve decreases smoothly and uniformly from the center to the edge of the field of view, indicating that the projection lens has good imaging quality and good detail resolution.

[0127] Figure 4The diagram shows the transverse chromatic aberration curves for Example 1, representing the chromatic aberration of each wavelength relative to the center wavelength (0.55 μm) at different image heights on the imaging plane. The horizontal axis represents the transverse chromatic aberration value of each wavelength relative to the center wavelength (unit: μm), and the vertical axis represents the normalized field of view. As can be seen from the diagram, the transverse chromatic aberration of the longest and shortest wavelengths is controlled within -1 μm to 5 μm, indicating that the projection lens can effectively correct chromatic aberration at the edges of the field of view.

[0128] Figure 5 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 has good relative illumination.

[0129] Example 2

[0130] Please see Figure 6 The figure shows a schematic diagram of the projection lens 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 a convex surface; the projection side surface S3 of the second lens L2 is a convex surface; and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

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

[0132] Table 2-1

[0133]

[0134] The surface profile parameters of the aspherical lens in the projection lens of Example 2 are shown in Table 2-2.

[0135] Table 2-2

[0136] Face number K B C D E F S5 -1.59E+00 1.41E-05 1.89E-06 2.83E-08 -1.19E-09 1.51E-11 S6 -3.41E+00 -1.46E-04 2.63E-06 1.52E-09 -4.36E-10 5.54E-12

[0137] from Figure 7 As can be seen, the F-Tanθ distortion of the projection lens is controlled within -5% to 0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the unfolded image.

[0138] from Figure 8 As can be seen, the MTF value of this embodiment is above 0.4 throughout the entire field of view. Within the range of 0 to 60 lp / mm, the MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens has good imaging quality and good detail resolution.

[0139] from Figure 9As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within -1μm to 5μm, indicating that the projection lens can correct the chromatic aberration at the edge of the field of view very well.

[0140] from Figure 10 As can be seen, the relative illuminance value of the projection lens is still greater than 98% at the maximum half field of view, indicating that the projection lens has good relative illuminance.

[0141] Example 3

[0142] Please see Figure 11 The diagram shows a schematic of the projection lens provided in Embodiment 3 of the present invention. The main difference between this embodiment and Embodiment 1 is that: the fourth lens L4 and the fifth lens L5 form a cemented lens group with negative optical power; the projection side surface S1 of the first lens L1 is convex; the projection side surface S10 of the sixth lens L6 is concave; and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0143] The relevant parameters of each lens in the projection lens in Example 3 are shown in Table 3-1.

[0144] Table 3-1

[0145]

[0146] The surface profile parameters of the aspherical lens in the projection lens of Example 3 are shown in Table 3-2.

[0147] Table 3-2

[0148] Face number K B C D E F S5 7.43E-01 1.41E-05 1.89E-06 2.83E-08 -1.19E-09 1.51E-11 S6 -2.84E+00 -1.46E-04 2.63E-06 1.52E-09 -4.36E-10 5.54E-12

[0149] from Figure 12 As can be seen, the F-Tanθ distortion of the projection lens is controlled within -4% to 0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the unfolded image.

[0150] from Figure 13 As can be seen, the MTF value of this embodiment is above 0.3 throughout the entire field of view. Within the range of 0 to 60 lp / mm, the MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens has good imaging quality and good detail resolution.

[0151] from Figure 14 As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within -1μm to 5μm, indicating that the projection lens can correct the chromatic aberration at the edge of the field of view very well.

[0152] from Figure 15As can be seen, the relative illuminance value of the projection lens is still greater than 98% at the maximum half field of view, indicating that the projection lens has good relative illuminance.

[0153] Example 4

[0154] Please see Figure 16 The diagram shows a schematic of the projection lens provided in Embodiment 4 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 convex; the projection side surface S7 of the fourth lens L4 is convex; the projection side surface S10 of the sixth lens L6 is concave; and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0155] The relevant parameters of each lens in the projection lens in Example 4 are shown in Table 4-1.

[0156] Table 4-1

[0157]

[0158]

[0159] The surface profile parameters of the aspherical lens in the projection lens of Example 4 are shown in Table 4-2.

[0160] Table 4-2

[0161] Face number K B C D E F S5 -2.29E+00 1.41E-05 1.89E-06 2.83E-08 -1.19E-09 1.51E-11 S6 -2.15E+00 -1.46E-04 2.63E-06 1.52E-09 -4.36E-10 5.54E-12

[0162] from Figure 17 As can be seen, the F-Tanθ distortion of the projection lens is controlled within -5% to 0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the unfolded image.

[0163] from Figure 18 As can be seen, the MTF value of this embodiment is above 0.2 throughout the entire field of view. Within the range of 0 to 60 lp / mm, the MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens has good imaging quality and good detail resolution.

[0164] from Figure 19 As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within -2μm to 5μm, indicating that the projection lens can correct the chromatic aberration at the edge of the field of view very well.

[0165] from Figure 20 As can be seen, the relative illuminance value of the projection lens is still greater than 98% at the maximum half field of view, indicating that the projection lens has good relative illuminance.

[0166] Example 5

[0167] Please see Figure 21 The diagram shows a schematic of the projection lens provided in Embodiment 5 of the present invention. The main difference between this embodiment and Embodiment 1 is that: the fourth lens L4 and the fifth lens L5 form a cemented lens group with positive optical power; the projection side surface S1 of the first lens L1 is convex; the image source side surface S2 of the first lens L1 is concave; and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0168] The relevant parameters of each lens in the projection lens in Example 5 are shown in Table 5-1.

[0169] Table 5-1

[0170]

[0171]

[0172] The surface profile parameters of the aspherical lens in the projection lens of Example 5 are shown in Table 5-2.

[0173] Table 5-2

[0174] Face number K B C D E F S5 -2.04E+00 1.41E-05 1.89E-06 2.83E-08 -1.19E-09 1.51E-11 S6 -3.75E+00 -1.46E-04 2.63E-06 1.52E-09 -4.36E-10 5.54E-12

[0175] from Figure 22 As can be seen, the F-Tanθ distortion of the projection lens is controlled within -5% to 0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the unfolded image.

[0176] from Figure 23 As can be seen, the MTF value of this embodiment is above 0.25 throughout the entire field of view. Within the range of 0 to 60 lp / mm, the MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens has good imaging quality and good detail resolution.

[0177] from Figure 24 As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within -1μm to 4μm, indicating that the projection lens can correct the chromatic aberration at the edge of the field of view very well.

[0178] from Figure 25 As can be seen, the relative illuminance value of the projection lens is still greater than 98% at the maximum half field of view, indicating that the projection lens has good relative illuminance.

[0179] Example 6

[0180] Please see Figure 26The diagram shows a schematic of the projection lens provided in Embodiment 6 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 convex, and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0181] The relevant parameters of each lens in the projection lens in Example 6 are shown in Table 6-1.

[0182] Table 6-1

[0183]

[0184] The surface profile parameters of the aspherical lens in the projection lens of Example 6 are shown in Table 6-2.

[0185] Table 6-2

[0186] Face number K B C D E F S5 -1.85E+00 4.14E-05 3.97E-07 2.36E-08 5.64E-11 -8.58E-12 S6 -7.92E+01 -1.79E-03 9.74E-05 -3.21E-06 5.85E-08 -4.44E-10

[0187] from Figure 27 As can be seen, the F-Tanθ distortion of the projection lens is controlled within -5% to 0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the unfolded image.

[0188] from Figure 28 As can be seen, the MTF value of this embodiment is above 0.3 throughout the entire field of view. Within the range of 0 to 60 lp / mm, the MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens has good imaging quality and good detail resolution.

[0189] from Figure 29 As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within -1μm to 6μm, indicating that the projection lens can correct the chromatic aberration at the edge of the field of view very well.

[0190] from Figure 30 As can be seen, the relative illuminance value of the projection lens is still greater than 98% at the maximum half field of view, indicating that the projection lens has good relative illuminance.

[0191] Example 7

[0192] Please see Figure 31 The diagram shows a schematic of the projection lens provided in Embodiment 7 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 convex, the projection side surface S7 of the fourth lens L4 is convex, and the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0193] The relevant parameters of each lens in the projection lens in Example 7 are shown in Table 7-1.

[0194] Table 7-1

[0195]

[0196] The surface profile parameters of the aspherical lens in the projection lens of Example 7 are shown in Table 7-2.

[0197] Table 7-2

[0198] Face number K B C D E F S5 -1.58E+00 3.90E-05 2.00E-06 7.97E-09 -5.74E-10 8.61E-12 S6 -3.34E+00 -1.44E-04 2.90E-06 -1.50E-08 -3.33E-11 1.92E-12

[0199] from Figure 27 As can be seen, the F-Tanθ distortion of the projection lens is controlled within -5% to 0, and the image compression in the edge angle area is relatively smooth, which effectively improves the clarity of the unfolded image.

[0200] from Figure 28 As can be seen, the MTF value of this embodiment is above 0.5 throughout the entire field of view. Within the range of 0 to 60 lp / mm, the MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens has good imaging quality and good detail resolution.

[0201] from Figure 29 As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within -1μm to 5μm, indicating that the projection lens can correct the chromatic aberration at the edge of the field of view very well.

[0202] from Figure 30 As can be seen, the relative illuminance value of the projection lens is still greater than 98% at the maximum half field of view, indicating that the projection lens has good relative illuminance.

[0203] Please refer to Table 8 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.

[0204] Table 8

[0205]

[0206]

[0207] 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.

[0208] 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.

[0209] 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 six lenses, characterized in that, In order from the projection plane to the image source plane along the optical axis, it includes: A first lens with positive optical power; A second lens with negative optical power, whose image source side surface is concave; A third lens with positive optical power, whose projection side surface is concave and the image source side surface is convex; A fourth lens with negative optical power, whose image source side surface is concave; A fifth lens with positive optical power, whose projection side surface and image source side surface are both convex; A sixth lens with positive optical power, whose image source side surface is convex; Wherein, the curvature radius R5 of the projection side surface of the third lens and the curvature radius R12 of the image source side surface of the sixth lens satisfy: -0.8 < (R5 - R12) / (R5 + R12) < 0; The effective focal length f of the projection lens, the maximum field angle FOV, and the true image height IH corresponding to the maximum field angle satisfy: 0.95 < (IH / 2) / (f × tan(FOV / 2)) < 1.

2. The projection lens according to claim 1, characterized in that, The chief ray angle of incidence CRA at the maximum image height of the projection lens satisfies: 1.18 ≤ CRA < 2.1°.

3. The projection lens according to claim 1, characterized in that, The curvature radius R5 of the projection side surface of the third lens and the curvature radius R12 of the image source side surface of the sixth lens satisfy: -0.57 < (R5 - R12) / (R5 + R12) < -0.01; The effective focal length f of the projection lens, the maximum field angle FOV, and the true image height IH corresponding to the maximum field angle satisfy: 0.96 ≤ (IH / 2) / (f × tan(FOV / 2)) ≤ 0.

98.

4. The projection lens according to claim 1, characterized in that, The effective focal length f of the projection lens and the back focal length BFL of the projection lens satisfy: 1.4 < BFL / f < 2.

4.

5. The projection lens according to claim 1, characterized in that, The effective focal length f of the projection lens and the focal length f3 of the third lens satisfy: 2 < f3 / f < 26.

8.

6. The projection lens according to claim 1, characterized in that, The effective focal length f of the projection lens and the combined focal length f456 of the fourth lens, the fifth lens, and the sixth lens satisfy: 0.8 < f456 / f < 2.

2.

7. The projection lens according to claim 1, characterized in that, The effective focal length f of the projection lens and the curvature radius R5 of the projection side surface of the third lens satisfy: -2.49 ≤ R5 / f < -0.

5.

8. The projection lens according to claim 1, characterized in that, The effective focal length f of the projection lens and the curvature radius R12 of the image source side surface of the sixth lens satisfy: -3.5 < R12 / f < -1.

1.

9. The projection lens according to claim 1, characterized in that, The focal length f5 of the fifth lens and the curvature radius R12 of the image source side surface of the sixth lens satisfy: 0.1 < R5 / R12 < 1.

1.

10. The projection lens according to claim 1, characterized in that, The clear aperture semi-diameter d5 of the projection side surface of the third lens and the sagitta Sag5 of the clear aperture semi-diameter of the projection side surface of the third lens satisfy: -0.4 < Sag5 / d5 < -0.1; the clear aperture semi-diameter d12 of the image source side surface of the sixth lens and the sagitta Sag12 of the clear aperture semi-diameter of the image source side surface of the sixth lens satisfy: -0.5 < Sag12 / d12 < -0.1.

Images