A low-distortion wide-angle lens

Abstract

The application discloses a low-distortion wide-angle lens, which comprises a front lens group and a rear lens group arranged in sequence along an optical axis from an object plane to an image plane; the front lens group comprises a first lens, a second lens and a third lens arranged in sequence along the optical axis from the object plane to the image plane; the rear lens group comprises a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence along the optical axis from the object plane to the image plane; the fourth lens and the fifth lens constitute a cemented lens group; the first lens, the second lens and the fifth lens are negative-power lenses; the third lens, the fourth lens, the sixth lens and the seventh lens are positive-power lenses; the first lens is a convex-concave lens; the second lens is a convex-concave lens; the third lens is a double-convex lens; the fourth lens is a double-convex lens; and the fifth lens is a concave-convex lens. The low-distortion wide-angle lens has a compact overall structure and improves imaging quality.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and in particular to a low-distortion wide-angle lens. Background Technology

[0002] Low-distortion wide-angle lenses are widely used in security monitoring, video conferencing, smart homes, vehicle monitoring, and smart education, among other fields. However, existing wide-angle lenses on the market typically exhibit significant distortion, affecting the image quality. Furthermore, wide-angle lenses often have an excessively long time-to-weight ratio (TTL) from the center of the object-side surface of the first lens to the image plane, resulting in large lens sizes and inconvenient installation. Therefore, there is a need to develop a lens with excellent imaging performance and very low distortion to address these issues. Summary of the Invention

[0003] This invention provides a low-distortion wide-angle lens with a compact overall structure, while improving image quality.

[0004] This invention provides a low-distortion wide-angle lens, comprising a front lens group and a rear lens group arranged sequentially along the optical axis from the object plane to the image plane. The front lens group includes a first lens, a second lens, and a third lens arranged sequentially along the optical axis from the object plane to the image plane. The rear lens group includes a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the object plane to the image plane. The fourth lens and the fifth lens constitute a cemented lens group.

[0005] The first lens, the second lens, and the fifth lens are all negative power lenses, while the third lens, the fourth lens, the sixth lens, and the seventh lens are all positive power lenses.

[0006] The surface of the lens adjacent to the object plane is called the object-side surface, and the surface of the lens adjacent to the image plane is called the image-side surface. The object-side surface of the first lens convexes towards the object plane, and the image-side surface of the first lens convexes towards the object plane. The object-side surface of the second lens convexes towards the object plane, and the image-side surface of the second lens convexes towards the object plane. The object-side surface of the third lens convexes towards the object plane, and the image-side surface of the third lens convexes towards the image plane. The object-side surface of the fourth lens convexes towards the object plane, and the image-side surface of the third lens convexes towards the image plane. The object-side surface of the fifth lens convexes towards the object plane, and the image-side surface of the fifth lens is a plane.

[0007] Optionally, the optical power of the first lens is Φ1, the optical power of the second lens is Φ2, the optical power of the third lens is Φ3, the optical power of the fourth lens is Φ4, the optical power of the fifth lens is Φ5, the optical power of the sixth lens is Φ6, the optical power of the seventh lens is Φ7, the optical power of the front lens group is ΦA, and the optical power of the rear lens group is ΦB, wherein:

[0008] 2.45≤Φ1 / ΦA≤3.85;0.65≤Φ2 / ΦA≤0.98;-2.45≤Φ3 / ΦA≤-1.25;1.05≤Φ4 / ΦB≤1.35;-1.65≤Φ5 / ΦB≤-1.05;0.55≤Φ6 / ΦB≤0.95;0.35≤Φ7 / ΦB≤0.65。

[0009] Optionally, the fourth and fifth lenses are both glass spherical lenses, while the first, second, third, sixth, and seventh lenses are all plastic aspherical lenses.

[0010] Optionally, the fourth lens has a refractive index of Nd4 and an Abbe number of Vd4; the fifth lens has a refractive index of Nd5 and an Abbe number of Vd5; wherein:

[0011] 1.45 <Nd4<1.65,55<Vd4<95;1.62<Nd5<2.10,18.55<Vd5<23.57。

[0012] Optionally, half the image height corresponding to the maximum field of view of the low-distortion wide-angle lens is 1 mgH, and the aperture number of the low-distortion wide-angle lens is FNO; wherein:

[0013] 1.45mm < ImgH / FNO < 1.65mm.

[0014] Optionally, the distance on the optical axis from the image-side surface of the second lens to the object-side surface of the third lens is AT23, the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens is AT34, and the thickness of the third lens on the optical axis is CT3; wherein:

[0015] 0.15<(AT23+AT34) / CT3<0.25.

[0016] Optionally, the maximum effective aperture on the object-side side of the first lens is SD11, and the maximum effective aperture on the image-side side of the seventh lens is SD72; wherein:

[0017] 1.20 < SD11 / SD72 < 1.75.

[0018] Optionally, the effective focal length of the first lens is f1, and the thickness of the first lens along the optical axis is CT1; wherein:

[0019] -2.15 < f1 / CT1 < -1.65.

[0020] Optionally, the low-distortion wide-angle lens may also include an aperture stop;

[0021] The aperture is located in the optical path between the third lens and the fourth lens.

[0022] Optionally, the distance from the object-side surface of the first lens to the aperture stop on the optical axis is DOS1, the distance from the aperture stop to the image-side surface of the seventh lens on the optical axis is DOS2, and TTL is the distance from the object-side surface of the first lens to the imaging plane of the low-distortion wide-angle lens on the optical axis; wherein:

[0023] 0.35<DOS1 / TTL<0.50; 0.25<DOS2 / TTL≤5.3708 / 14.5248.

[0024] The low-distortion wide-angle lens provided in this embodiment of the invention improves the image quality of the lens by reasonably setting the number of lenses and the optical power of each lens. At the same time, by reasonably setting the surface shape of each lens, the optical lens can be made compact and highly integrated, thereby reducing the size of the lens.

[0025] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a low-distortion wide-angle lens provided in Embodiment 1 of the present invention;

[0028] Figure 2 This is a spherical aberration curve of a low-distortion wide-angle lens provided in Embodiment 1 of the present invention;

[0029] Figure 3 This is a field curvature distortion diagram of a low-distortion wide-angle lens provided in Embodiment 1 of the present invention;

[0030] Figure 4 This is a schematic diagram of the structure of a low-distortion wide-angle lens provided in Embodiment 2 of the present invention;

[0031] Figure 5 This is a spherical aberration curve of a low-distortion wide-angle lens provided in Embodiment 2 of the present invention;

[0032] Figure 6This is a field curvature distortion diagram of a low-distortion wide-angle lens provided in Embodiment 2 of the present invention;

[0033] Figure 7 This is a schematic diagram of the structure of a low-distortion wide-angle lens provided in Embodiment 3 of the present invention;

[0034] Figure 8 This is a spherical aberration curve of a low-distortion wide-angle lens provided in Embodiment 3 of the present invention;

[0035] Figure 9 This is a field curvature distortion diagram of a low-distortion wide-angle lens provided in Embodiment 3 of the present invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0037] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0038] Example 1

[0039] Figure 1 This is a schematic diagram of the structure of a low-distortion wide-angle lens provided in Embodiment 1 of the present invention, as shown below. Figure 1As shown, the low-distortion wide-angle lens includes a front lens group and a rear lens group arranged sequentially from the object plane to the image plane along the optical axis. The front lens group includes a first lens 101, a second lens 102, and a third lens 103 arranged sequentially from the object plane to the image plane along the optical axis. The rear lens group includes a fourth lens 104, a fifth lens 105, a sixth lens 106, and a seventh lens 107 arranged sequentially from the object plane to the image plane along the optical axis. The fourth lens 104 and the fifth lens 105 constitute a cemented lens group. The first lens 101, the second lens 102, and the fifth lens 105 are all negative power lenses, while the third lens 103, the fourth lens 104, the sixth lens 106, and the seventh lens 107 are all negative power lenses. Positive power lens; the surface of the lens adjacent to the object plane is the object-side surface, and the surface of the lens adjacent to the image plane is the image-side surface; the object-side surface of the first lens 101 convexes towards the object plane, and the image-side surface of the first lens 101 convexes towards the object plane; the object-side surface of the second lens 102 convexes towards the object plane, and the image-side surface of the second lens 102 convexes towards the object plane; the object-side surface of the third lens 103 convexes towards the object plane, and the image-side surface of the third lens 103 convexes towards the image plane; the object-side surface of the fourth lens 104 convexes towards the object plane, and the image-side surface of the fourth lens 104 convexes towards the image plane; the object-side surface of the fifth lens 105 convexes towards the image plane, and the image-side surface of the fifth lens 105 convexes towards the image plane.

[0040] Optical power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light. The larger the absolute value of the optical power, the stronger the bending ability of light; the smaller the absolute value, the weaker the bending ability. When the optical power is positive, the refraction of light is converging; when the optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a system formed by multiple lenses (i.e., a lens group). In the low-distortion wide-angle lens provided in this embodiment, all lenses can be fixed in a single lens barrel (…). Figure 1In the (not shown) section, both the first lens 101 and the second lens 102 are negative power lenses with negative refractive power. The object-side surface of the first lens 101 convexes towards the object plane, and the image-side surface of the first lens 101 convexes towards the object plane. Similarly, the object-side surface of the second lens 102 convexes towards the object plane, thus facilitating the deflection of light rays incident at large angles to achieve the wide viewing angle characteristic of the optical system. The third lens 103 is a positive power lens with positive refractive power. Both the object-side surface and the image-side surface of the third lens 103 convex towards the object plane. This allows the third lens 103 to converge light rays from the first lens 101 and the second lens 102 in a timely manner, while also helping to adjust field curvature aberrations at the edges of the field of view. The fourth lens 104 and the fifth lens 105 together form a cemented lens group. On the one hand, this facilitates a smooth transition of incident light as it passes through the cemented lens group, further correcting field curvature and astigmatism. On the other hand, the cemented arrangement allows the cumulative tolerance of the two lenses to be set into the tolerance of a single integrated lens, reducing eccentricity sensitivity, lowering system assembly sensitivity, solving lens manufacturing and assembly problems, improving yield, reducing costs, and also reducing the overall length of the lens. The arrangement of the sixth lens 106 and the seventh lens 107 deflects the incident light, sharing the deflection burden of the object-side lens, thereby increasing the smooth transition of incident light by the rear group of the low-distortion wide-angle lens. Especially for optical systems with wide viewing angles, this effectively corrects aberrations over a large field of view. For example, the equivalent focal length of the low-distortion wide-angle lens is 2.0mm, the field of view (FOV) is 123°, the total optical length (TTL) is less than 15.0mm, the distance (BFL) from the image side of the seventh lens (107) to the imaging surface of the low-distortion wide-angle lens on the optical axis is greater than 3.2mm, the optical distortion is less than 10%, the maximum effective diameter of the lens is less than 9.0mm, and the imaging target surface is greater than φ6.4mm, ensuring a compact overall structure and strong practicality.

[0041] Optionally, the optical power of the first lens 101 is Φ1, the optical power of the second lens 102 is Φ2, the optical power of the third lens 103 is Φ3, the optical power of the fourth lens 104 is Φ4, the optical power of the fifth lens 105 is Φ5, the optical power of the sixth lens 106 is Φ6, the optical power of the seventh lens 107 is Φ7, the optical power of the front group of the lens is ΦA, and the optical power of the rear group of the lens is ΦB, wherein: 2.45≤Φ1 / ΦA≤3.85; 0.65≤Φ2 / ΦA≤0.98; -2.45≤Φ3 / ΦA≤-1.25; 1.05≤Φ4 / ΦB≤1.35; -1.65≤Φ5 / ΦB≤-1.05; 0.55≤Φ6 / ΦB≤0.95; 0.35≤Φ7 / ΦB≤0.65. By controlling the shape of the first lens 101 and the optical power ratio and position of each lens element, a wide-angle view is achieved. Simultaneously, by controlling the optical path of each field of view, the imaging requirement of less than 10% optical distortion is met, ensuring that the image quality is not affected by excessive distortion. By rationally allocating the optical power of each lens in the low-distortion wide-angle lens, aberrations such as spherical aberration, coma, and chromatic aberration are corrected, resulting in excellent image quality and improved image quality.

[0042] Optionally, the fourth lens 104 and the fifth lens 105 are both glass spherical lenses, while the first lens 101, the second lens 102, the third lens 103, the sixth lens 106 and the seventh lens 107 are all plastic aspherical lenses.

[0043] The aspherical lens corrects all advanced aberrations. Since plastic lenses are significantly cheaper than glass lenses, the low-distortion wide-angle lens provided in this embodiment of the invention, by incorporating five plastic aspherical lenses, achieves good image quality, low cost, and a lighter overall weight. Furthermore, the mutual compensation between the two materials ensures the practicality of the low-distortion wide-angle lens.

[0044] Optionally, the fourth lens 104 has a refractive index of Nd⁴ and an Abbe number of Vd⁴; the fifth lens 105 has a refractive index of Nd⁵ and an Abbe number of Vd⁵; where: 1.45 <Nd4<1.65,55<Vd4<95;1.62<Nd5<2.10,18.55<Vd5<23.57。

[0045] Refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium, primarily used to describe a material's ability to refract light; different materials have different refractive indices. Abbe number is an index used to represent the dispersion ability of a transparent medium; the more severe the dispersion, the smaller the Abbe number; conversely, the less severe the dispersion, the larger the Abbe number. Thus, by adjusting the refractive indices and Abbe numbers of the lenses in a low-distortion wide-angle lens, the rear group of the lens uses a cemented glass lens group consisting of a fourth lens 104 and a fifth lens 105, along with a sixth plastic aspherical lens 106 and a seventh plastic aspherical lens 107. By using combinations of materials with different dispersion coefficients and matching them with the actual optical power, aberrations are corrected, and image quality is improved.

[0046] Optionally, half of the image height corresponding to the maximum field of view of the low-distortion wide-angle lens is ImgH, and the aperture number of the low-distortion wide-angle lens is FNO; where: 1.45mm < ImgH / FNO < 1.65mm.

[0047] Compared to typical low-distortion wide-angle lenses with a wide field of view, satisfying the above relationship allows for the matching of higher-pixel image sensors, improving image resolution. It also ensures sufficient light transmission to match the image sensor size, further enhancing image sharpness. Below the lower limit of the relationship, insufficient light intake or insufficient image height can lead to a failure to simultaneously achieve both sharp imaging and a wide field of view. Above the upper limit, the aperture of the low-distortion wide-angle lens becomes too small, resulting in excessive and difficult-to-manage aberrations.

[0048] Optionally, a filter 10 is also provided along the object plane to the image plane; the filter 10 is located on the image plane side of the seventh lens 107. It can filter out unwanted stray light, thereby improving the image quality of the optical lens.

[0049] Optionally, the distance on the optical axis from the image side of the second lens 102 to the object side of the third lens 103 is AT23, the distance on the optical axis from the image side of the third lens 103 to the object side of the fourth lens 104 is AT34, and the thickness of the third lens 103 on the optical axis is CT3; wherein: 0.15 < (AT23 + AT34) / CT3 < 0.25.

[0050] When the above relationships are satisfied, the center thickness of the third lens 103 and the spacing between the third lens 103 and the front and rear lenses can be reasonably controlled, so that the third lens 103 can work with the second lens 102 and the fourth lens 104 to better handle the incident light, so that the light rays incident at large angles can become smooth when passing through these three lenses, thereby reducing aberrations; within this range, the spacing is reasonable, which helps to improve the assembly yield and reduce the assembly difficulty; at the same time, by adjusting the distance between the lens and the aperture, astigmatism, coma, distortion and transverse aberration can be well corrected.

[0051] Optionally, the maximum effective aperture of the object side of the first lens 101 is SD11, and the maximum effective aperture of the image side of the seventh lens 107 is SD72; where: 1.20 < SD11 / SD72 < 1.75.

[0052] When the above relationship is satisfied, on the one hand, light rays from a wider range of angles in the object space can be gathered by the first lens 101 to enter the low-distortion wide-angle lens, thereby increasing the field of view of the low-distortion wide-angle lens; on the other hand, light rays can be smoothly emitted from the seventh lens 107 to the imaging surface, thereby helping to reduce the incident angle of the principal ray on the imaging surface, thereby improving the image quality of the system.

[0053] Optionally, the effective focal length of the first lens 101 is f1, and the thickness of the first lens 101 on the optical axis is CT1; wherein: -2.15 < f1 / CT1 < -1.65.

[0054] When the above relationship is satisfied, the refractive power and center thickness of the first lens 101 can be reasonably matched, which helps to correct aberrations in low-distortion wide-angle lenses, expand the field of view of low-distortion wide-angle lenses, and improve the molding yield of the first lens 101. When the value is below the lower limit of the relationship, the absolute value of the effective focal length of the first lens 101 is too large, the refractive power is insufficient, which is not conducive to expanding the field of view of the optical system, and is not conducive to suppressing higher-order aberrations, thus resulting in higher-order spherical aberration, coma, and other phenomena that affect the resolution and imaging quality of low-distortion wide-angle lenses; or it may lead to the first lens 101 being too thin, increasing the molding difficulty. When the value exceeds the upper limit of the relationship, the absolute value of the effective focal length of the first lens 101 is too small, the refractive power is too strong, which causes the incident beam in the edge field of view to rapidly contract relative to the optical axis when passing through the first lens 101, thereby increasing the incident angle of the light rays to the image-side lens group, increasing the burden on the image-side lens group to reduce the incident angle of the light rays on the imaging plane.

[0055] Optionally, the low-distortion wide-angle lens also includes an aperture stop; the aperture stop is located in the optical path between the third lens 103 and the fourth lens 104.

[0056] By placing the aperture stop in the optical path between the third lens 103 and the fourth lens 104, the front and rear lens groups are arranged symmetrically with respect to the aperture stop. This allows for adjustment of the beam propagation direction and the angle of incidence, which helps improve image quality.

[0057] Optionally, the distance from the object-side surface of the first lens 101 to the aperture stop on the optical axis is DOS1, the distance from the aperture stop to the image-side surface of the seventh lens 107 on the optical axis is DOS2, and the distance from the object-side surface of the first lens 101 to the imaging plane of the low-distortion wide-angle lens on the optical axis is TTL; where: 0.35 < DOS1 / TTL < 0.50; 0.25 < DOS2 / TTL ≤ 5.3708 / 14.5248. When the above relationships are satisfied, the overall structure of the low-distortion wide-angle lens can be made more compact, the optical lens integration is high, thereby achieving miniaturization design.

[0058] The low-distortion wide-angle lens provided in this embodiment of the invention, by reasonably allocating the optical power, surface shape, refractive index, Abbe number, etc. of each lens, ensures a compact overall structure of the low-distortion wide-angle lens under the premise of low cost, while improving imaging quality and meeting the requirements of high-definition image quality.

[0059] As a feasible implementation method, the curvature radius, thickness, material, and K-coefficient of each lens surface in a low-distortion wide-angle lens are described below.

[0060] Table 1. Design values ​​for a low-distortion wide-angle lens

[0061]

[0062] Continue to refer to Figure 1The low-distortion wide-angle lens provided in Embodiment 1 of the present invention includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, and a seventh lens 107 arranged sequentially along the optical axis from the object plane to the image plane. Table 1 shows the optical physical parameters such as the radius of curvature, thickness, and material of each lens in the low-distortion wide-angle lens provided in Embodiment 1. The surface number is determined by the order of the lenses' surfaces. For example, "STO" represents the aperture stop of a low-distortion wide-angle lens, "1" represents the object surface of the first lens 101, "2" represents the image surface of the first lens 101, "10" represents the object surface of the sixth lens 106, "11" represents the image surface of the sixth lens 106, and so on. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image surface, and a negative value indicates that the surface bends towards the object surface. "INF" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance from the current surface to the next surface. Both the radius of curvature and the thickness are in millimeters (mm). A blank space indicates that the current position is air with a refractive index of 1. The k-value represents the magnitude of the conic coefficient of the aspherical surface.

[0063] The aspherical surface shape equation Z of the first lens 101, the second lens 102, the third lens 103, the sixth lens 106, and the seventh lens 107 satisfies:

[0064]

[0065] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th and 16th order terms of the aspherical polynomial.

[0066] For example, Table 2 details the aspherical coefficients of each lens in this embodiment with a feasible implementation method.

[0067] Table 2 Aspherical coefficients of various lenses in low-distortion wide-angle lenses

[0068]

[0069] Where 2.768195E-04 indicates that the coefficient A of face number 1 is 2.768195 * 10. -4 And so on.

[0070] The low-distortion wide-angle lens in this embodiment achieves the following technical specifications:

[0071] Focal length: f=1.922mm;

[0072] F-number: F=2.15;

[0073] Field of view: 123°;

[0074] Total optical length (TTL): 14.52 mm;

[0075] BFL: 3.264mm;

[0076] Optical distortion: -7.1%;

[0077] ImgH: 3.3mm.

[0078] Furthermore, Figure 2 This is a spherical aberration curve of a low-distortion wide-angle lens provided in Embodiment 1 of the present invention, as shown below. Figure 2 As shown, the vertical direction represents the normalized aperture, 0 indicates on the optical axis, and the vertical vertex represents the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). The spherical aberration of this low-distortion wide-angle lens is controlled within the range of (-0.04mm, +0.04mm) at different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm, and 0.656μm). The relatively concentrated curves at different wavelengths indicate that the axial aberration of this low-distortion wide-angle lens is very small. Therefore, it can be seen that the low-distortion wide-angle lens provided in Embodiment 1 of this invention can effectively correct aberrations and meet the requirements of wide-spectrum applications.

[0079] Figure 3 The field curvature distortion diagram of a low-distortion wide-angle lens provided in Embodiment 1 of the present invention is as follows: Figure 3 As shown, in the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the arc loss; from Figure 3 It can be seen that the low-distortion wide-angle lens provided in this embodiment effectively controls the field curvature from light with wavelengths from 426nm to 656nm, meaning that during imaging, the difference in image quality between the center and the periphery is small; in the coordinate system on the right, the horizontal axis represents the magnitude of distortion, in %; the vertical axis represents the normalized image height, which has no unit; from Figure 3 As can be seen, the distortion of the low-distortion wide-angle lens provided in this embodiment has been well corrected, with imaging distortion of less than 10%, which meets the requirements for low distortion.

[0080] Example 2

[0081] Figure 4 This is a schematic diagram of the structure of a low-distortion wide-angle lens provided in Embodiment 2 of the present invention, as shown below. Figure 1As shown, the low-distortion wide-angle lens includes a front lens group and a rear lens group arranged sequentially from the object plane to the image plane along the optical axis. The front lens group includes a first lens 201, a second lens 202, and a third lens 203 arranged sequentially from the object plane to the image plane along the optical axis. The rear lens group includes a fourth lens 204, a fifth lens 205, a sixth lens 206, and a seventh lens 207 arranged sequentially from the object plane to the image plane along the optical axis. The fourth lens 204 and the fifth lens 205 constitute a cemented lens group. The first lens 201, the second lens 202, and the fifth lens 205 are all negative power lenses, while the third lens 203, the fourth lens 204, the sixth lens 206, and the seventh lens 207 are all negative power lenses. Positive power lens; the surface of the lens adjacent to the object plane is the object-side surface, and the surface of the lens adjacent to the image plane is the image-side surface; the object-side surface of the first lens 201 convexes towards the object plane, and the image-side surface of the first lens 201 convexes towards the object plane; the object-side surface of the second lens 202 convexes towards the object plane, and the image-side surface of the second lens 202 convexes towards the object plane; the object-side surface of the third lens 203 convexes towards the object plane, and the image-side surface of the third lens 203 convexes towards the image plane; the object-side surface of the fourth lens 204 convexes towards the object plane, and the image-side surface of the fourth lens 204 convexes towards the image plane; the object-side surface of the fifth lens 205 convexes towards the image plane, and the image-side surface of the fifth lens 205 convexes towards the image plane.

[0082] The optical power, focal length, refractive index, and Abbe number of each lens are the same as in Example 1, and will not be repeated here.

[0083] As another feasible implementation method, the curvature radius, thickness, material, half-aperture and K-factor of each lens surface in the low distortion wide-angle lens are described below.

[0084] Table 3. Design values ​​for low-distortion wide-angle lenses

[0085]

[0086] Continue to refer to Figure 4The low-distortion wide-angle lens provided in Embodiment 2 of the present invention includes a first lens 201, a second lens 202, a third lens 203, a fourth lens 204, a fifth lens 205, a sixth lens 206, and a seventh lens 207 arranged sequentially along the optical axis from the object plane to the image plane. Table 3 shows the optical physical parameters such as the radius of curvature, thickness, and material of each lens in the low-distortion wide-angle lens provided in Embodiment 2. The surface number is determined by the order of the lenses' surfaces. For example, "STO" represents the aperture stop of a low-distortion wide-angle lens, "1" represents the object surface of the first lens 201, "2" represents the image surface of the first lens 201, "10" represents the object surface of the sixth lens 206, "11" represents the image surface of the sixth lens 206, and so on. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image surface, and a negative value indicates that the surface bends towards the object surface. "INF" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance from the current surface to the next surface. Both the radius of curvature and the thickness are in millimeters (mm). A blank space indicates that the current position is air with a refractive index of 1. The k-value represents the magnitude of the conic coefficient of the aspherical surface.

[0087] The aspherical surface shape equation Z of the first lens 201, the second lens 202, the third lens 203, the sixth lens 206, and the seventh lens 207 satisfies:

[0088]

[0089] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th and 16th order terms of the aspherical polynomial.

[0090] For example, Table 4 details the aspherical coefficients of each lens in this embodiment with a feasible implementation method.

[0091] Table 4. Aspherical coefficients of various lenses in low-distortion wide-angle lenses:

[0092]

[0093] Where 2.645664E-04 indicates that the coefficient A of face number 1 is 2.645664 * 10. -4 And so on.

[0094] The low-distortion wide-angle lens in this second embodiment achieves the following technical specifications:

[0095] Focal length: f=1.946mm;

[0096] F-number: F=2.15;

[0097] Field of view: 123°;

[0098] Total optical length (TTL): 14.52 mm;

[0099] BFL: 3.234mm;

[0100] Optical distortion: -8.3%;

[0101] ImgH: 3.3mm.

[0102] Furthermore, Figure 5 This is a spherical aberration curve of a low-distortion wide-angle lens provided in Embodiment 2 of the present invention, as shown in the figure. Figure 5 As shown, the vertical direction represents the normalized aperture, 0 indicates on the optical axis, and the vertical vertex represents the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focal point, in millimeters (mm). The spherical aberration of this low-distortion wide-angle lens is controlled within the range of (-0.04mm, +0.04mm) at different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm, and 0.656μm). The relatively concentrated curves at different wavelengths indicate that the axial aberration of this low-distortion wide-angle lens is very small. Therefore, it can be seen that the low-distortion wide-angle lens provided in Embodiment 2 of this invention can effectively correct aberrations and meet the requirements of wide-spectrum applications.

[0103] Figure 6 This is a field curvature distortion diagram of a low-distortion wide-angle lens provided in Embodiment 2 of the present invention, as shown below. Figure 6 As shown, in the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the arc loss; from Figure 6 It can be seen that the low-distortion wide-angle lens provided in this embodiment effectively controls the field curvature from light with wavelengths from 426nm to 656nm, meaning that during imaging, the difference in image quality between the center and the periphery is small; in the coordinate system on the right, the horizontal axis represents the magnitude of distortion, in %; the vertical axis represents the normalized image height, which has no unit; from Figure 6 As can be seen, the distortion of the low-distortion wide-angle lens provided in this embodiment 2 has been well corrected, with imaging distortion of less than 10%, which meets the requirements for low distortion.

[0104] Example 3

[0105] Figure 7 This is a schematic diagram of the structure of a low-distortion wide-angle lens provided in Embodiment 3 of the present invention, as shown below. Figure 7As shown, the low-distortion wide-angle lens includes a front lens group and a rear lens group arranged sequentially from the object plane to the image plane along the optical axis. The front lens group includes a first lens 301, a second lens 302, and a third lens 303 arranged sequentially from the object plane to the image plane along the optical axis. The rear lens group includes a fourth lens 304, a fifth lens 305, a sixth lens 306, and a seventh lens 307 arranged sequentially from the object plane to the image plane along the optical axis. The fourth lens 304 and the fifth lens 305 constitute a cemented lens group. The first lens 301, the second lens 302, and the fifth lens 305 are all negative power lenses, while the third lens 303, the fourth lens 304, the sixth lens 306, and the seventh lens 307 are all negative power lenses. Positive power lens; the surface of the lens adjacent to the object plane is the object-side surface, and the surface of the lens adjacent to the image plane is the image-side surface; the object-side surface of the first lens 301 convexes towards the object plane, and the image-side surface of the first lens 301 convexes towards the object plane; the object-side surface of the second lens 302 convexes towards the object plane, and the image-side surface of the second lens 302 convexes towards the object plane; the object-side surface of the third lens 303 convexes towards the object plane, and the image-side surface of the third lens 303 convexes towards the image plane; the object-side surface of the fourth lens 304 convexes towards the object plane, and the image-side surface of the fourth lens 304 convexes towards the image plane; the object-side surface of the fifth lens 305 convexes towards the image plane, and the image-side surface of the fifth lens 305 convexes towards the image plane.

[0106] The optical power, focal length, refractive index, and Abbe number of each lens are the same as in Example 1, and will not be repeated here.

[0107] As another feasible implementation method, the curvature radius, thickness, material, half-aperture and K-factor of each lens surface in the low distortion wide-angle lens are described below.

[0108] Table 5. Design values ​​for low-distortion wide-angle lenses

[0109]

[0110] Continue to refer to Figure 7The low-distortion wide-angle lens provided in Embodiment 3 of the present invention includes a first lens 301, a second lens 302, a third lens 303, a fourth lens 304, a fifth lens 305, a sixth lens 306, and a seventh lens 307 arranged sequentially along the optical axis from the object plane to the image plane. Table 5 shows the optical physical parameters such as the radius of curvature, thickness, and material of each lens in the low-distortion wide-angle lens provided in Embodiment 3. The surface number is assigned according to the order of the lenses. For example, "STO" represents the aperture stop of a low-distortion wide-angle lens, "1" represents the object surface of the first lens 301, "2" represents the image surface of the first lens 301, "10" represents the object surface of the sixth lens 306, "11" represents the image surface of the sixth lens 306, and so on. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image surface, and a negative value indicates that the surface bends towards the object surface. "INF" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance from the current surface to the next surface. The units for both the radius of curvature and the thickness are millimeters (mm). A blank space indicates that the current position is air with a refractive index of 1. The k value represents the magnitude of the conic coefficient of the aspherical surface.

[0111] The aspherical surface shape equation Z of the first lens 301, the second lens 302, the third lens 303, the sixth lens 306, and the seventh lens 307 satisfies:

[0112]

[0113] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th and 16th order terms of the aspherical polynomial.

[0114] For example, Table 6 details the aspherical coefficients of each lens in this embodiment with a feasible implementation.

[0115] Table 6 Aspherical coefficients of various lenses in low-distortion wide-angle lenses

[0116]

[0117] Where 5.533464E-05 indicates that the coefficient A of face number 1 is 5.533464 * 10. -5 And so on.

[0118] The low-distortion wide-angle lens in this third embodiment achieves the following technical specifications:

[0119] Focal length: f=1.931mm;

[0120] F-number: F=2.15;

[0121] Field of view: 123°;

[0122] Total optical length (TTL): 14.53 mm;

[0123] BFL: 3.289mm;

[0124] Optical distortion: -7.5%;

[0125] ImgH: 3.3mm.

[0126] Furthermore, Figure 8 This is a spherical aberration curve of a low-distortion wide-angle lens provided in Embodiment 3 of the present invention, as shown in the figure. Figure 8 As shown, the vertical direction represents the normalized aperture, 0 indicates on the optical axis, and the vertical vertex represents the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focal point, in millimeters (mm). The spherical aberration of this low-distortion wide-angle lens is controlled within the range of (-0.02mm, +0.02mm) at different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm, and 0.656μm). The relatively concentrated curves at different wavelengths indicate that the axial aberration of this low-distortion wide-angle lens is very small. Therefore, it can be seen that the low-distortion wide-angle lens provided in Embodiment 3 of this invention can effectively correct aberrations and meet the requirements of wide-spectrum applications.

[0127] Figure 9 This is a field curvature distortion diagram of a low-distortion wide-angle lens provided in Embodiment 3 of the present invention, as shown below. Figure 9 As shown, in the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the arc loss; from Figure 9 It can be seen that the low-distortion wide-angle lens provided in this embodiment effectively controls the field curvature from light with wavelengths from 426nm to 656nm, meaning that during imaging, the difference in image quality between the center and the periphery is small; in the coordinate system on the right, the horizontal axis represents the magnitude of distortion, in %; the vertical axis represents the normalized image height, which has no unit; from Figure 9 As can be seen, the distortion of the low-distortion wide-angle lens provided in this embodiment 3 has been well corrected, with imaging distortion of less than 10%, which meets the requirements for low distortion.

[0128] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A low-distortion wide-angle lens, characterized in that, The lens comprises a front lens group and a rear lens group arranged sequentially from the object plane to the image plane along the optical axis. The front lens group includes a first lens, a second lens, and a third lens arranged sequentially from the object plane to the image plane along the optical axis. The rear lens group includes a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially from the object plane to the image plane along the optical axis. The fourth lens and the fifth lens constitute a cemented lens group. The low-distortion wide-angle lens has seven lenses with optical power. The first lens, the second lens, and the fifth lens are all negative power lenses, while the third lens, the fourth lens, the sixth lens, and the seventh lens are all positive power lenses. The surface of the lens adjacent to the object plane is called the object-side surface, and the surface of the lens adjacent to the image plane is called the image-side surface; the object-side surface of the first lens convexes towards the object plane, and the image-side surface of the first lens convexes towards the object plane; the object-side surface of the second lens convexes towards the object plane, and the image-side surface of the second lens convexes towards the object plane; the object-side surface of the third lens convexes towards the object plane, and the image-side surface of the third lens convexes towards the image plane; the object-side surface of the fourth lens convexes towards the object plane, and the image-side surface of the fourth lens convexes towards the image plane; the object-side surface of the fifth lens convexes towards the image plane, and the image-side surface of the fifth lens convexes towards the image plane. The first lens has an optical power of Φ1, the second lens has an optical power of Φ2, the third lens has an optical power of Φ3, the fourth lens has an optical power of Φ4, the fifth lens has an optical power of Φ5, the sixth lens has an optical power of Φ6, the seventh lens has an optical power of Φ7, the front lens group has an optical power of ΦA, and the rear lens group has an optical power of ΦB. in: 2.45≤Φ1 / ΦA≤3.85;0.65≤Φ2 / ΦA≤0.98;-2.45≤Φ3 / ΦA≤-1.25;1.05≤Φ4 / ΦB≤1.35;-1.65≤Φ5 / ΦB≤-1.05;0.55≤Φ6 / ΦB≤0.95;0.35≤Φ7 / ΦB≤0.65。 2. The low-distortion wide-angle lens according to claim 1, characterized in that, The fourth and fifth lenses are both glass spherical lenses, while the first, second, third, sixth, and seventh lenses are all plastic aspherical lenses.

3. The low-distortion wide-angle lens according to claim 1, characterized in that, The fourth lens has a refractive index of Nd4 and an Abbe number of Vd4; the fifth lens has a refractive index of Nd5 and an Abbe number of Vd5; wherein: 1.45 <Nd4<1.65,55<Vd4<95;1.62<Nd5<2.10,18.55<Vd5<23.57。 4. The low-distortion wide-angle lens according to claim 1, characterized in that, The image height corresponding to the maximum field of view of the low-distortion wide-angle lens is half of ImgH, and the aperture number of the low-distortion wide-angle lens is FNO; where: 1.45mm < ImgH / FNO < 1.65mm.

5. The low-distortion wide-angle lens according to claim 1, characterized in that, The distance on the optical axis from the image-side surface of the second lens to the object-side surface of the third lens is AT23, the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens is AT34, and the thickness of the third lens on the optical axis is CT3; wherein: 0.15<(AT23+AT34) / CT3<0.

25.

6. The low-distortion wide-angle lens according to claim 1, characterized in that, The maximum effective aperture of the object-side surface of the first lens is SD11, and the maximum effective aperture of the image-side surface of the seventh lens is SD72; wherein: 1.20 < SD11 / SD72 < 1.

75.

7. The low-distortion wide-angle lens according to claim 1, characterized in that, The effective focal length of the first lens is f1, and the thickness of the first lens along the optical axis is CT1; wherein: -2.15 < f1 / CT1 < -1.

65.

8. The low-distortion wide-angle lens according to claim 1, characterized in that, The low-distortion wide-angle lens also includes an aperture stop; The aperture is located in the optical path between the third lens and the fourth lens.

9. The low-distortion wide-angle lens according to claim 8, characterized in that, The distance from the object-side surface of the first lens to the aperture stop on the optical axis is DOS1, the distance from the aperture stop to the image-side surface of the seventh lens on the optical axis is DOS2, and the distance from the object-side surface of the first lens to the image plane of the low-distortion wide-angle lens on the optical axis is TTL; wherein: 0.35<DOS1 / TTL<0.50; 0.25<DOS2 / TTL≤5.3708 / 14.5248.

Images