Long-focus low-distortion imaging optical system and camera module applied by same

Abstract

The utility model provides a long-focus low-distortion imaging optical system and a camera module applying the same, the long-focus low-distortion imaging optical system is composed of eight lenses, the first lens has focal power, the object side surface is a convex surface, the image side surface is a concave surface, the second lens has positive focal power, the object side surface is a convex surface, and the image side surface is a concave surface. The third lens has negative focal power, the object side surface is a convex surface, the image side surface is a concave surface, the fourth lens has negative focal power, the fifth lens has focal power, the sixth lens has positive focal power, the seventh lens has focal power, and the eighth lens has negative focal power. Therefore, the optical lens has the advantages of being compact in structure, light in weight, low in distortion and large in aperture, meanwhile, detail information of an object can be well captured, the detail capturing capacity of the optical lens for shooting the object is improved, the picture texture of the optical lens is improved, and the resolution ratio and the imaging definition of the optical lens are improved, so that the requirements of various aerial photography applications are met.

Description

Technical Field

[0001] This application relates to the field of optical imaging, and more particularly to a long-focal-length low-distortion imaging optical system and its application in camera modules. Background Technology

[0002] With the rapid development of drone technology and the increasing popularity of aerial photography applications, people have higher and higher requirements for the performance of aerial photography optical imaging systems. Aerial lenses not only need to meet the design requirements of lightweight and miniaturization, but also must have the characteristics of high resolution and low distortion to adapt to the special needs of high-altitude shooting. However, existing aerial lenses often suffer from problems such as degraded edge image quality and increased distortion when shooting, resulting in difficulties in stitching aerial images and loss of detail.

[0003] To achieve better image quality, traditional solutions typically require increasing the number of lenses to correct aberrations, but this leads to increased lens weight and size, which contradicts the strict payload requirements of drones.

[0004] In addition, external factors such as temperature changes and mechanical vibrations in the aerial photography environment can also significantly affect image quality. Especially when shooting with a telephoto lens, even a slight lens shift can cause noticeable image blur, severely impacting the aerial photography results.

[0005] Therefore, how to achieve high resolution, low distortion, and good environmental adaptability while ensuring lightweight lenses has become a key technical challenge in the development of aerial photography optical systems. Utility Model Content

[0006] This application aims to provide a long-focal-length low-distortion imaging optical system, which features long focal length, low distortion, low cost, and large aperture. It has a compact structure, is easy to manufacture and install, and the large aperture configuration can increase the amount of light entering the optical system and achieve higher image quality.

[0007] To achieve its purpose, this utility model adopts the following technical solution:

[0008] A long-focal-length low-distortion imaging optical system comprises, along the optical axis from the object plane to the image plane, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens.

[0009] The first lens has optical power, and its object side is convex and its image side is concave.

[0010] The second lens has positive optical power, with its object side being convex and its image side being concave.

[0011] The third lens has negative optical power, and its object side is convex while its image side is concave.

[0012] The fourth lens has negative optical power;

[0013] The fifth lens has optical power;

[0014] The sixth lens has positive optical power;

[0015] The seventh lens has optical power;

[0016] The eighth lens has negative optical power;

[0017] The second and third lenses form an adhesive lens, and the fourth and fifth lenses form an adhesive lens.

[0018] The imaging optical system satisfies the following relationship:

[0019] 1.2 < |f3+f4| / |f3-f4| < 3.4;

[0020] -3.5 <f4 / |(f4+f5)|<0;

[0021] 0 < (f5 + f6) / f6 < 2.1;

[0022] Where f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, and f6 is the effective focal length of the sixth lens.

[0023] The long-focal-length low-distortion imaging optical system described above satisfies the following relationship:

[0024] 0.2 < |f345 / f| < 0.7;

[0025] Where f345 is the effective combined focal length of the third, fourth, and fifth lenses, and f is the effective focal length of the imaging optical system.

[0026] The long-focal-length low-distortion imaging optical system described above satisfies the following relationship:

[0027] 1.6 <f / R3<2.4;

[0028] Where R6 is the radius of curvature of the image side of the third lens, f is the effective focal length of the imaging optical system, and R3 is the radius of curvature of the object side of the second lens.

[0029] The long-focal-length low-distortion imaging optical system described above satisfies the following relationship:

[0030] 1.3 < (R1 + R2) / R2 < 2.2;

[0031] -2.0 < (R5 - R6) / R5 < -0.9;

[0032] 1.5 <f / R3<2.4;

[0033] Wherein, R1 is the radius of curvature of the object side of the first lens, R2 is the radius of curvature of the image side of the first lens, R5 is the radius of curvature of the object side of the third lens, R6 is the radius of curvature of the image side of the third lens, f is the effective focal length of the imaging optical system, and R3 is the radius of curvature of the object side of the second lens.

[0034] The long-focal-length low-distortion imaging optical system described above satisfies the following relationship:

[0035] 1.0 < (CT6 + CT7) / BFL < 2.6;

[0036] Wherein, BFL is the shortest distance (also known as optical back focal length) from the image side of the eighth lens to the imaging surface of the optical system along the optical axis, CT6 is the center thickness of the sixth lens along the optical axis, and CT7 is the center thickness of the seventh lens along the optical axis.

[0037] The long-focal-length low-distortion imaging optical system described above satisfies the following relationship:

[0038] 1.3 <TTL / f<1.7;

[0039] Where f is the effective focal length of the imaging optical system, and TTL is the on-axis distance from the object side of the first lens to the imaging plane.

[0040] The long-focal-length low-distortion imaging optical system described above satisfies the following relationship:

[0041] 1.6 ≤ f / EPD ≤ 2.0;

[0042] Where f is the effective focal length of the imaging optical system, and EPD is the entrance pupil diameter of the optical imaging lens.

[0043] The long-focal-length low-distortion imaging optical system described above satisfies the following relationship:

[0044] 8.4 < (FNO * f * ImgH) / TTL < 11.2;

[0045] Where FNO is the F-number of the optical imaging lens, f is the effective focal length of the imaging optical system, ImgH is half the diagonal length of the effective pixel area on the imaging surface, and TTL is the on-axis distance from the object side of the first lens to the imaging surface.

[0046] In the long-focal-length low-distortion imaging optical system described above, the system aperture is located between the third lens and the fourth lens.

[0047] The long-focal-length low-distortion imaging optical system described above has an F-number ≤ 2.0 and an overall length ≤ 62.0 mm.

[0048] On the other hand, this application embodiment also provides a camera module, which includes at least an optical lens, and the above-mentioned telephoto low distortion imaging optical system is installed in the optical lens.

[0049] Compared with the prior art, the beneficial effects of this application are as follows:

[0050] This invention provides a long-focal-length low-distortion imaging optical system and its application in a camera module. By selecting eight glass lenses and rationally configuring the refractive power and surface shape of each lens, the optical lens can have the characteristics of compact structure, lightweight, low distortion and large aperture. At the same time, it can also capture object detail information better, improve the optical lens's ability to capture the details of the photographed object, improve the image quality of the optical lens, and improve the resolution and imaging clarity of the optical lens to meet the needs of various aerial photography applications. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0052] Figure 1 This is a schematic diagram of the structure of the optical system or camera module in Embodiment 1 of this application;

[0053] Figure 2 These are the on-axis chromatic aberration, astigmatism, and distortion curves of the optical system or camera module in Embodiment 1 of this application;

[0054] Figure 3 This is a schematic diagram of the structure of the optical system or camera module in Embodiment 2 of this application;

[0055] Figure 4 These are the on-axis chromatic aberration, astigmatism, and distortion curves of the optical system or camera module in Embodiment 2 of this application;

[0056] Figure 5 This is a schematic diagram of the structure of the optical system or camera module in Embodiment 3 of this application;

[0057] Figure 6 These are the on-axis chromatic aberration, astigmatism, and distortion curves of the optical system or camera module in Embodiment 3 of this application;

[0058] Figure 7 This is a schematic diagram of the structure of the optical system or camera module in Embodiment 4 of this application;

[0059] Figure 8 These are the on-axis chromatic aberration, astigmatism, and distortion curves of the optical system or camera module in Embodiment 4 of this application. Detailed Implementation

[0060] This application provides a long-focal-length low-distortion imaging optical system, comprising a first lens E1, a second lens E2, a third lens E3, an aperture stop STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, and an infrared filter E9 arranged sequentially from the object side. The first lens has optical power, with its object side being convex and its image side being concave. The second lens has positive optical power, with its object side being convex and its image side being concave. The third lens has negative optical power, with its object side being convex and its image side being concave. The fourth lens has negative optical power. The fifth lens has optical power. The sixth lens has positive optical power. The seventh lens has optical power. The eighth lens has negative optical power. The second and third lenses form a bonded lens. The fourth and fifth lenses form a bonded lens. The imaging optical system has an F-number ≤ 2.0 and an overall length ≤ 62.0 mm.

[0061] This invention provides a long-focal-length, low-distortion imaging optical system. By selecting eight glass lenses and rationally configuring the refractive power and surface shape of each lens, the optical lens can have the characteristics of compact structure, lightweight, low distortion, and large aperture. At the same time, it can also capture object detail information better, improve the optical lens's ability to capture the details of the photographed object, improve the image quality of the optical lens, and improve the resolution and image clarity of the optical lens to meet the needs of various aerial photography applications.

[0062] In a preferred embodiment of this application, the imaging optical system satisfies the following relationship: 8.4 < (FNO * f * ImgH) / TTL < 11.2, where FNO is the F-number of the optical imaging lens, f is the effective focal length of the optical imaging system, ImgH is half the diagonal length of the effective pixel area on the imaging plane, and TTL is the on-axis distance from the side of the first lens to the imaging plane. By limiting the aperture, effective focal length, and the ratio of half the diagonal length of the effective pixel area on the imaging plane to the on-axis distance from the side of the first lens to the imaging plane, aberrations can be ensured to be within a correctable range, reducing design complexity. When the ratio is below the lower limit of the relationship, while ensuring a large aperture, the total optical length of the optical system increases, resulting in limited actual light flux, affecting relative illumination, and reducing optical imaging quality in low-light environments; when the ratio is above the upper limit of the relationship, it may cause excessively large incident angles of light rays in the edge field of view, increasing astigmatism or coma.

[0063] As a preferred embodiment of the present application, the imaging optical system satisfies the following relationship: 1.6 ≤ f / EPD ≤ 2.0, where f is the effective focal length of the optical imaging system and EPD is the entrance pupil diameter of the optical imaging lens. By limiting the above relationship within a reasonable range, it is possible to avoid excessive sacrifice of the performance of the optical imaging system while meeting the low distortion requirements of the optical imaging lens.

[0064] As a preferred embodiment of the present application, the imaging optical system satisfies the following relationship: 1.2 < |f3 + f4| / |f3 - f4| < 3.4, where f3 is the effective focal length of the third lens and f4 is the effective focal length of the fourth lens. By reasonably controlling the focal length ratio of the third lens and the fourth lens, the optical system can meet the large field angle range while obtaining high imaging resolution. Exceeding the upper limit of the relationship, the refractive power of the third lens and the fourth lens is insufficient, and it is difficult for large-angle light rays to enter the optical system, which is not conducive to expanding the field angle range of the optical system; below the lower limit of the relationship, the refractive power of the third lens and the fourth lens is too strong, and strong astigmatism and chromatic aberration are easily generated, which is not conducive to high-resolution imaging characteristics.

[0065] As a preferred embodiment of the present application, the imaging optical system satisfies the following relationship: -3.5 < f4 / |(f4 + f5)| < 0, where f4 is the effective focal length of the fourth lens and f5 is the effective focal length of the fifth lens. By reasonably distributing the proportion of the optical power of the fourth and fifth optical members near the image plane within a reasonable range, it is possible to balance the remaining spherical aberration after balancing to balance the spherical aberration generated by the first three lenses, thereby finely adjusting and controlling the spherical aberration of the system and strengthening the precise control of the axial field aberration.

[0066] As a preferred embodiment of the present application, the imaging optical system satisfies the following relationship: 0 < (f5 + f6) / f6 < 2.1, where f5 is the effective focal length of the fifth lens and f6 is the effective focal length of the sixth lens. By reasonably controlling the range of the above formula, it is possible to contribute reasonable positive third-order spherical aberration and negative fifth-order spherical aberration, balance the negative third-order spherical aberration and positive fifth-order spherical aberration generated by the fifth lens and the sixth lens, make the system have smaller spherical aberration, and ensure good imaging quality of the axial field.

[0067] As a preferred embodiment of the present application, the imaging optical system satisfies the following relationship: 0.2 < |f345 / f| < 0.7, where f345 is the effective combined focal length of the third lens, the fourth lens, and the fifth lens, and f is the effective focal length of the optical imaging system. By constraining the ratio of the combined focal length of the third lens, the fourth lens, and the fifth lens to the effective focal length of the optical lens, the optical power distribution of the third lens, the fourth lens, and the fifth lens can be made appropriate, enabling the fourth lens to have diverse cooperation, thereby achieving the balance of internal aberrations of the optical lens, and further contributing to adjusting the field curvature and astigmatism of the imaging edge of the optical lens to meet the imaging quality of the optical lens for the surrounding environment.

[0068] As a preferred embodiment of the present application, the imaging optical system satisfies the following relationship: 1.3 < (R1 + R2) / R2 < 2.2, where R1 is the curvature radius of the object side surface of the first lens, and R2 is the curvature radius of the image side surface of the first lens. By controlling the curvature radii of the object side surface and the image side surface of the first lens, the total deflection angles of the object side surface and the image side surface of the first lens at the edge field can be reasonably controlled within a reasonable range, effectively reducing the sensitivity of the system.

[0069] As a preferred embodiment of the present application, the imaging optical system satisfies the following relationship: -2.0 < (R5 - R6) / R5 < -0.9, where R5 is the curvature radius of the object side surface of the third lens, and R6 is the curvature radius of the image side surface of the third lens. By limiting the ratio range of the curvature radii of the object side surface and the image side surface of the third lens, the shape of the third lens can be effectively constrained, and further the aberration contribution rates of the object side and the image side surfaces of the third lens can be effectively controlled to effectively balance the aberrations related to the aperture band of the system, and further effectively improve the imaging quality of the system.

[0070] As a preferred embodiment of the present application, the imaging optical system satisfies the following relationship: 1.5 < f / R3 < 2.4, where f is the effective focal length of the optical imaging system, and R3 is the curvature radius of the object side surface of the second lens. By limiting the range of the above relationship, it is beneficial to constrain the bending degree of the object side surface of the second lens, allowing more light to enter the optical system. At the same time, it is also beneficial to reasonably distribute the refractive power of the optical system and correct the off-axis aberrations of the optical system. Exceeding the upper limit of the relationship, the focal length of the optical system is too large, which is not conducive to achieving the miniaturization characteristics and further affects the thinness and lightness of the entire optical system; below the lower limit of the relationship, the curvature radius of the object side surface of the second lens is too small, and the image side surface of the second lens is too curved, further increasing the risk of ghost images.

[0071] In a preferred embodiment of this application, the imaging optical system satisfies the following relationship: 1.0 < (CT6 + CT7) / BFL < 2.6, where BFL is the shortest distance (also known as the optical back focal length) along the optical axis from the image side of the eighth lens to the imaging surface of the optical system, CT6 is the center thickness of the sixth lens along the optical axis, and CT7 is the center thickness of the seventh lens along the optical axis. When the above condition is satisfied, by controlling the optical back focal length within a reasonable range, the matching degree between the camera image and the image sensor is effectively ensured, guaranteeing the matching performance between the optical system and the image sensor; at the same time, the thicknesses of the sixth and seventh lenses are controlled, reducing the thickness tolerance sensitivity of the optical system, which is beneficial for controlling the assembly thickness tolerance of the entire optical system, thereby reducing production costs.

[0072] Example 1:

[0073] The following is for reference Figures 1 to 2 Describes an optical imaging lens according to Embodiment 1 of this application. Figure 1 A schematic diagram of the structure of an optical imaging lens according to Embodiment 1 of this application is shown.

[0074] like Figure 1 As shown, the optical imaging lens according to an exemplary embodiment of this application includes, in sequence along the optical axis from the object side to the image side: a first lens E1, a second lens E2, a third lens E3, a STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, an infrared filter E9, and an imaging surface S17.

[0075] The first lens E1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has positive optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S4 being convex and its image-side surface S5 being concave. The fourth lens E4 has negative optical power, with its object-side surface S6 being concave and its image-side surface S7 being convex. The fifth lens E5 has positive optical power, with its object-side surface S7 being concave and its image-side surface S8 being convex. The sixth lens E6 has positive optical power, with its object-side surface S9 being convex and its image-side surface S10 being flat. The seventh lens E7 has negative optical power, with its object-side surface S11 being convex and its image-side surface S12 being concave. The eighth lens E8 has negative optical power, with its object-side surface S13 being convex and its image-side surface S14 being concave. The filter E9 has an object-side surface S15 and an image-side surface S16. Light from the object passes through surfaces S1 to S16 in sequence and is finally imaged on the imaging surface S17.

[0076] Table 1 shows the surface type, radius of curvature, thickness, and material of each lens in the optical imaging lens of Example 1, wherein the units for radius of curvature and thickness are millimeters (mm).

[0077] Table 1

[0078]

[0079] In Table 1, the object-side and image-side surfaces of the eighth lens E8 are both Q-type aspherical surfaces. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formulas:

[0080]

[0081] Where Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspherical surface, c is the curvature of the vertex of the aspherical surface, K is the conic coefficient, Am is the aspherical coefficient, and r max The maximum value of the radial radius coordinate is u = r / r max Table 2 provides the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 for each aspherical surface that can be used in the first embodiment.

[0082] Table 2

[0083]

[0084] Example 2:

[0085] The following is for reference Figures 3 to 4 Describes an optical imaging lens according to Embodiment 2 of this application. Figure 3 A schematic diagram of the structure of an optical imaging lens according to Embodiment 2 of this application is shown.

[0086] like Figure 3 As shown, the optical imaging lens according to an exemplary embodiment of this application includes, in sequence along the optical axis from the object side to the image side: a first lens E1, a second lens E2, a third lens E3, a STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, an infrared filter E9, and an imaging surface S17.

[0087] The first lens E1 has negative optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has positive optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S4 being convex and its image-side surface S5 being concave. The fourth lens E4 has negative optical power, with its object-side surface S6 being concave and its image-side surface S7 being convex. The fifth lens E5 has positive optical power, with its object-side surface S7 being concave and its image-side surface S8 being convex. The sixth lens E6 has positive optical power, with its object-side surface S9 being convex and its image-side surface S10 being flat. The seventh lens E7 has negative optical power, with its object-side surface S11 being concave and its image-side surface S12 being convex. The eighth lens E8 has negative optical power, with its object-side surface S13 being concave and its image-side surface S14 being concave. The filter E9 has an object-side surface S15 and an image-side surface S16. Light from the object passes through surfaces S1 to S16 in sequence and is finally imaged on the imaging surface S17.

[0088] Table 3 shows the surface type, radius of curvature, thickness, and material of each lens in the optical imaging lens of Example 2, wherein the units for radius of curvature and thickness are millimeters (mm).

[0089] Table 3

[0090]

[0091] In Table 3, the object-side and image-side surfaces of the eighth lens E8 are both Q-type aspherical surfaces. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formulas:

[0092]

[0093] Where Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspherical surface, c is the curvature of the vertex of the aspherical surface, K is the conic coefficient, Am is the aspherical coefficient, and r max The maximum value of the radial radius coordinate is u = r / r max Table 4 provides the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 for each aspherical surface that can be used in the second embodiment.

[0094] Table 4

[0095]

[0096] Example 3:

[0097] The following is for reference Figures 5 to 6 Describes an optical imaging lens according to Embodiment 3 of this application. Figure 5 A schematic diagram of the structure of an optical imaging lens according to Embodiment 3 of this application is shown.

[0098] like Figure 5 As shown, the optical imaging lens according to an exemplary embodiment of this application includes, in sequence along the optical axis from the object side to the image side: a first lens E1, a second lens E2, a third lens E3, a STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, an infrared filter E9, and an imaging surface S17.

[0099] The first lens E1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has positive optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S4 being convex and its image-side surface S5 being concave. The fourth lens E4 has negative optical power, with its object-side surface S6 being concave and its image-side surface S7 being convex. The fifth lens E5 has negative optical power, with its object-side surface S7 being concave and its image-side surface S8 being concave. The sixth lens E6 has positive optical power, with its object-side surface S9 being convex and its image-side surface S10 being convex. The seventh lens E7 has positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being concave. The eighth lens E8 has negative optical power, with its object-side surface S13 being concave and its image-side surface S14 being convex. The filter E9 has an object-side surface S15 and an image-side surface S16. Light from the object passes through surfaces S1 to S16 in sequence and is finally imaged on the imaging surface S17.

[0100] Table 5 shows the surface type, radius of curvature, thickness, and material of each lens in the optical imaging lens of Example 3, wherein the units for radius of curvature and thickness are millimeters (mm).

[0101] Table 5

[0102]

[0103] Example 4:

[0104] The following is for reference Figures 7 to 8 Describes an optical imaging lens according to Embodiment 4 of this application. Figure 7 A schematic diagram of the structure of an optical imaging lens according to Embodiment 4 of this application is shown.

[0105] like Figure 7 As shown, the optical imaging lens according to an exemplary embodiment of this application includes, in sequence along the optical axis from the object side to the image side: a first lens E1, a second lens E2, a third lens E3, a STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, an infrared filter E9, and an imaging surface S17.

[0106] The first lens E1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has positive optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S4 being convex and its image-side surface S5 being concave. The fourth lens E4 has negative optical power, with its object-side surface S6 being concave and its image-side surface S7 being concave. The fifth lens E5 has negative optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The sixth lens E6 has positive optical power, with its object-side surface S9 being convex and its image-side surface S10 being convex. The seventh lens E7 has positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being concave. The eighth lens E8 has negative optical power, with its object-side surface S13 being concave and its image-side surface S14 being concave. The filter E9 has an object-side surface S15 and an image-side surface S16. Light from the object passes through surfaces S1 to S16 in sequence and is finally imaged on the imaging surface S17.

[0107] Table 7 shows the surface type, radius of curvature, thickness, and material of each lens in the optical imaging lens of Example 4, wherein the units for radius of curvature and thickness are millimeters (mm).

[0108] Table 6

[0109]

[0110] In Table 7, the object-side and image-side surfaces of the eighth lens E8 are both Q-type aspherical surfaces. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formulas:

[0111]

[0112] Where Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspherical surface, c is the curvature of the vertex of the aspherical surface, K is the conic coefficient, Am is the aspherical coefficient, and r max The maximum value of the radial radius coordinate is u = r / r max Table 4 provides the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 for each aspherical surface that can be used in the fourth embodiment.

[0113] Table 7

[0114]

[0115] In Examples 1-4, the basic data is as follows:

[0116] Table 8

[0117]

[0118] In Examples 1-4, each conditional expression satisfies the conditions in the table below:

[0119] Table 9

[0120]

[0121] A camera module includes at least an optical lens, in which the aforementioned telephoto low-distortion imaging optical system is installed. The camera module configured in this invention features telephoto capability, low distortion, low cost, and a large aperture. It has a compact structure, is easy to manufacture and install, and the large aperture configuration can increase the amount of light entering the optical system and achieve higher image quality.

[0122] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A long-focal-length low-distortion imaging optical system, comprising, in sequence along the optical axis from the object plane to the image plane, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens, characterized in that: The first lens has optical power, and its object side is convex and its image side is concave. The second lens has positive optical power, with its object side being convex and its image side being concave. The third lens has negative optical power, and its object side is convex while its image side is concave. The fourth lens has negative optical power; The fifth lens has optical power; The sixth lens has positive optical power; The seventh lens has optical power; The eighth lens has negative optical power; The second and third lenses form an adhesive lens, and the fourth and fifth lenses form an adhesive lens.

2. The long-focal-length low-distortion imaging optical system according to claim 1, characterized in that: The imaging optical system satisfies the following relationship: 1.2 < |f3+f4| / |f3-f4| < 3.4; and / or -3.5 < f4 / |(f4+f5)| < 0; and / or 0 < (f5+f6) / f6 < 2.1; and / or 0.2 < |f345 / f| < 0.7; Where f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, f345 is the effective combined focal length of the third, fourth and fifth lenses, and f is the effective focal length of the imaging optical system.

3. The long-focal-length low-distortion imaging optical system according to claim 1, characterized in that: The imaging optical system satisfies the following relationship: 1.5 < f / R3 < 2.4; Where R6 is the radius of curvature of the image side of the third lens, f is the effective focal length of the imaging optical system, and R3 is the radius of curvature of the object side of the second lens.

4. The long-focal-length low-distortion imaging optical system according to any one of claims 1-3, characterized in that: The imaging optical system satisfies the following relationship: 1.3 < (R1+R2) / R2 < 2.2; and / or -2.0 < (R5-R6) / R5 < -0.9; and / or 1.6 < f / R3 < 2.4; Wherein, R1 is the radius of curvature of the object side of the first lens, R2 is the radius of curvature of the image side of the first lens, R5 is the radius of curvature of the object side of the third lens, R6 is the radius of curvature of the image side of the third lens, f is the effective focal length of the imaging optical system, and R3 is the radius of curvature of the object side of the second lens.

5. The long-focal-length low-distortion imaging optical system according to any one of claims 1-3, characterized in that: The imaging optical system satisfies the following relationship: 1.0 < (CT6+CT7) / BFL < 2.6; Wherein, BFL is the shortest distance (also known as optical back focal length) from the image side of the eighth lens to the imaging surface of the optical system along the optical axis, CT6 is the center thickness of the sixth lens along the optical axis, and CT7 is the center thickness of the seventh lens along the optical axis.

6. The long-focal-length low-distortion imaging optical system according to any one of claims 1-3, characterized in that: The imaging optical system satisfies the following relationship: 1.3 < TTL / f < 1.7; Where f is the effective focal length of the imaging optical system, and TTL is the on-axis distance from the object side of the first lens to the imaging plane.

7. The long-focal-length low-distortion imaging optical system according to any one of claims 1-3, characterized in that: The imaging optical system satisfies the following relationship: 1.6 ≤ f / EPD ≤ 2.0; Where f is the effective focal length of the imaging optical system, and EPD is the entrance pupil diameter of the optical imaging lens.

8. The long-focal-length low-distortion imaging optical system according to any one of claims 1-3, characterized in that: The imaging optical system satisfies the following relationship: 8.4< (FNO*f*ImgH) / TTL < 11.2; Where FNO is the F-number of the optical imaging lens, f is the effective focal length of the imaging optical system, ImgH is half the diagonal length of the effective pixel area on the imaging surface, and TTL is the on-axis distance from the object side of the first lens to the imaging surface.

9. The long-focal-length low-distortion imaging optical system according to any one of claims 1-3, characterized in that: The system aperture is positioned between the third and fourth lenses; and / or The imaging optical system has an F-number ≤ 2.0 and an overall length ≤ 62.0 mm.

10. A camera module, comprising at least an optical lens, characterized in that: The optical lens is equipped with the telephoto low-distortion imaging optical system according to any one of claims 1-9.

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