Telephoto lens

Abstract

The telephoto lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from an object plane to an image plane along an optical axis, the first lens has positive focal power; the second lens has positive focal power; the third lens has negative focal power; the fourth lens has negative focal power; the fifth lens has negative focal power; the sixth lens has positive focal power; the second lens, the third lens and the sixth lens are glass spherical lenses; the first lens, the fourth lens and the fifth lens are plastic aspheric lenses. According to the telephoto lens provided by the embodiment of the invention, the total optical length TTL is less than or equal to 14.5 mm, the focal length EFL is about 11.5 mm, the maximum image height reaches 7mm, and the telephoto lens with the total length, small size, low cost and large target surface is realized.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a telephoto lens. Background Art

[0002] Competition in the security market is becoming increasingly fierce, and the performance requirements for lenses are becoming increasingly demanding. Currently, most lenses used in security systems have short focal lengths, making them difficult to achieve long-distance monitoring. They are also bulky, costly, and susceptible to installation space constraints. Summary of the Invention

[0003] The present invention provides a telephoto lens, which can realize a telephoto lens having a short total length, a small volume, a low cost and a large target surface.

[0004] The present invention provides a telephoto lens, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in sequence along an optical axis from an object plane to an image plane;

[0005] The first lens has positive optical power;

[0006] The second lens has positive optical power;

[0007] The third lens has negative optical power;

[0008] The fourth lens has negative optical power;

[0009] The fifth lens has negative optical power;

[0010] The sixth lens has positive optical power;

[0011] The second lens, the third lens, and the sixth lens are glass spherical lenses; the first lens, the fourth lens, and the fifth lens are plastic aspherical lenses.

[0012] Optionally, the optical power of the telephoto lens is The optical power of the first lens is The optical power of the second lens is The optical power of the third lens is The optical power of the fifth lens is The optical power of the sixth lens is

[0013]

[0014] Optionally, the object-side surface of the first lens is convex, and the image-side surface is concave;

[0015] The object-side surface of the second lens is convex, and the image-side surface is convex;

[0016] The object side surface of the third lens is concave, and the image side surface is concave;

[0017] The object-side surface of the fourth lens is convex, and the image-side surface is concave;

[0018] The object-side surface of the fifth lens is concave, and the image-side surface is convex;

[0019] The object-side surface of the sixth lens is convex, and the image-side surface is convex.

[0020] Optionally, the Abbe number of the first lens is Vd1, 20.48≤Vd1≤59.84.

[0021] Optionally, the Abbe number of the second lens is Vd2;

[0022] The Abbe number of the third lens is Vd3, and the refractive index is Nd3;

[0023] 41.00≤Vd2-Vd3≤68.00;

[0024] 1.48≤Nd3≤1.74.

[0025] Optionally, the second lens and the third lens form a cemented lens group;

[0026] or,

[0027] A distance between the second lens and the third lens on the optical axis is greater than 0.

[0028] Optionally, the refractive index of the fourth lens is Nd4, and the refractive index of the fifth lens is Nd5;

[0029] -0.04≤Nd5-Nd4≤0.15.

[0030] Optionally, the total optical length of the telephoto lens is TTL, the optical back focus of the telephoto lens is BFL, the focal length of the telephoto lens is EFL, and the clear aperture of the sixth lens is DT6;

[0031] 0.38≤DT6 / BFL≤0.55; 0.75≤(TTL-BFL) / EFL≤0.9.

[0032] Optionally, the refractive index of the sixth lens is Nd6, 1.74≤Nd6≤2.05.

[0033] Optionally, the telephoto lens further includes an aperture;

[0034] The aperture is located in the optical path between the fourth lens and the fifth lens;

[0035] or,

[0036] The aperture is located on the object-side surface of the first lens.

[0037] The telephoto lens provided in an embodiment of the present invention utilizes six lenses in a 3G3P (3 glass lenses and 3 plastic lenses) structure, a hybrid of glass spherical lenses and plastic aspherical lenses. By rationally allocating the optical power, surface shape, and material of each lens, the lens achieves excellent imaging performance. Its total optical length satisfies a TTL of ≤ 14.5mm, its EFL is approximately 11.5mm, and its maximum image height reaches 7mm. This achieves a telephoto lens that balances overall length, compact size, low cost, and a large target surface. This telephoto lens meets miniaturization requirements while ensuring a sufficient target surface size to accommodate different sensor specifications, satisfying the requirements for long-distance monitoring in a variety of security surveillance scenarios.

[0038] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 A schematic structural diagram of a telephoto lens provided by an embodiment of the present invention;

[0041] Figure 2 A schematic structural diagram of another telephoto lens provided by an embodiment of the present invention;

[0042] Figure 3 A schematic structural diagram of another telephoto lens provided by an embodiment of the present invention;

[0043] Figure 4 A schematic structural diagram of another telephoto lens provided by an embodiment of the present invention;

[0044] Figure 5 A spherical aberration curve diagram of the telephoto lens provided in Example 1 of the present invention;

[0045] Figure 6 A spherical aberration curve diagram of the telephoto lens provided in Example 2 of the present invention;

[0046] Figure 7 This is a spherical aberration curve diagram of the telephoto lens provided in Example 3 of the present invention;

[0047] Figure 8 This is a spherical aberration curve diagram of the telephoto lens provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0049] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0050] Figure 1 A schematic structural diagram of a telephoto lens provided by an embodiment of the present invention is shown. Figure 2 A schematic structural diagram of another telephoto lens provided by an embodiment of the present invention, Figure 3 A schematic structural diagram of another telephoto lens provided by an embodiment of the present invention is shown. Figure 4 A structural diagram of another telephoto lens provided by an embodiment of the present invention is shown in FIG. Figure 1-Figure 4 As shown, the telephoto lens provided by the embodiment of the present invention includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a sixth lens L6, which are arranged in sequence from the object plane to the image plane along the optical axis.

[0051] The first lens L1 has positive refractive power, the second lens L2 has positive refractive power, the third lens L3 has negative refractive power, the fourth lens L4 has negative refractive power, the fifth lens L5 has negative refractive power, and the sixth lens L6 has positive refractive power.

[0052] The second lens L2, the third lens L3 and the sixth lens L6 are glass spherical lenses; the first lens L1, the fourth lens L4 and the fifth lens L5 are plastic aspherical lenses.

[0053] Specifically, the focal length is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam, and it characterizes the ability of an optical system to deflect light. The larger the absolute value of the focal length, the stronger the ability to bend light, and the smaller the absolute value of the focal length, the weaker the ability to bend light. When the focal length is a positive number, the refraction of light is convergent; when the focal length is a negative number, the refraction of light is divergent. The focal length can be used to characterize a refractive surface of a lens (i.e., a surface of a lens), a single lens, or a system formed by multiple lenses (i.e., a lens group).

[0054] In the lens provided in this embodiment, each lens can be fixed to a lens barrel ( Figure 1-Figure 4 (not shown), but is not limited thereto.

[0055] Among them, the first lens L1 has positive optical power, and the first lens L1 adopts a plastic aspherical lens, which can control the incident angle of the lens and achieve the characteristic of long focal length.

[0056] The second lens L2 has positive focal power, and the third lens L3 has negative focal power. Both the second lens L2 and the third lens L3 are glass spherical lenses, which can effectively shrink light, reduce assembly tolerances, and improve production yield.

[0057] The fourth lens L4 has negative optical power, the fifth lens L5 has negative optical power, and both the fourth lens L4 and the fifth lens L5 are plastic aspherical lenses, which can make the structures of the fourth lens L4 and the fifth lens L5 more symmetrical, help correct off-axis aberrations, and improve imaging quality.

[0058] The sixth lens element L6 has positive refractive power and is a glass spherical lens. When combined with the fifth lens element L5, the sixth lens element L6 can optimize field curvature and performance such as the main ray angle.

[0059] It should be noted that glass has a lower thermal expansion coefficient than plastic. The second lens L2, the third lens L3, and the sixth lens L6 are made of glass spherical lenses, which can make the shapes of the above lenses more stable when facing changes in ambient temperature. This can reduce the impact of high and low temperatures on the imaging quality of the telephoto lens, avoid the occurrence of defocus in different environments, and achieve the characteristic of no defocus from -40°C to 80°C.

[0060] At the same time, glass has a higher refractive index than plastic, and can effectively adjust light through the second lens L2, the third lens L3 and the sixth lens L6 to enhance image clarity.

[0061] In addition, the manufacturing process of spherical lenses is mature and relatively low-cost, making them suitable for use in critical positions that require high stability. The spherical design of the second lens L2, the third lens L3, and the sixth lens L6 helps reduce lens costs. At the same time, when combined with other aspherical lenses, the overall aberration correction effect can be further optimized.

[0062] Furthermore, the first lens L1, the fourth lens L4 and the fifth lens L5 are plastic aspheric lenses. Compared with glass, the processing cost of plastic materials is lower and the weight of plastic lenses is lighter, which helps to achieve miniaturization and lightweight design of the lenses.

[0063] At the same time, aspheric lenses can effectively correct high-level aberrations such as spherical aberration and coma, significantly improving imaging quality. Therefore, aspheric lenses can achieve complex optical functions with a smaller number of lenses, thereby reducing the overall length and volume of the lens.

[0064] In addition, plastic lenses can be easily manufactured into complex aspheric shapes through injection molding, simplifying the manufacturing process and further reducing costs.

[0065] It should be noted that the material of the glass lens is various types of glass known to those skilled in the art, and the material of the plastic lens is various types of plastic known to those skilled in the art, which will not be elaborated or limited in the embodiments of the present invention.

[0066] In summary, the telephoto lens provided in the embodiments of the present invention utilizes six lenses in a 3G3P (3 glass lenses and 3 plastic lenses) structure, a hybrid of glass spherical lenses and plastic aspherical lenses. By rationally allocating the optical power, surface shape, and material of each lens, the lens achieves excellent imaging performance, with a total optical length meeting TTL ≤ 14.5mm, an EFL focal length of approximately 11.5mm, and a maximum image height of 7mm. This achieves a telephoto lens that balances short overall length, compact size, low cost, and a large target surface. This telephoto lens meets miniaturization requirements while ensuring a sufficient target surface size to accommodate different sensor specifications, satisfying the requirements for long-distance monitoring in a variety of security monitoring scenarios.

[0067] As a feasible implementation method, the optical power of the telephoto lens is The optical power of the first lens L1 is The optical power of the second lens L2 is The optical power of the third lens L3 is The optical power of the fifth lens L5 is The optical power of the sixth lens L6 is

[0068]

[0069] When the optical power of the first lens L1 satisfies the above range, the incident angle of the lens can be controlled and the characteristic of long focal length can be achieved.

[0070] When the optical powers of the second lens L2 and the third lens L3 meet the above ranges, they can effectively shrink light, reduce assembly tolerances, and improve production yields.

[0071] When the optical powers of the fourth lens L4, the fifth lens L5 and the sixth lens L6 meet the above ranges, off-axis aberrations can be corrected, field curvature can be optimized, and performance such as the main ray angle and distortion can be optimized.

[0072] At the same time, by controlling the optical focal length of each lens in the entire telephoto lens and distributing it in a certain proportion, while ensuring the functions of the above-mentioned lenses and achieving the required optical performance indicators (such as short total length, small size, low cost, large target area, etc.), the balance of the incident angles of the front and rear lenses can also be ensured to reduce the sensitivity of the lenses, which is beneficial to improving the stability of the telephoto lens, and is beneficial to correcting system aberrations and improving imaging quality.

[0073] As a feasible implementation method, Figure 1-Figure 4 As shown, the object-side surface of the first lens L1 is convex, and the image-side surface is concave; the object-side surface of the second lens L2 is convex, and the image-side surface is convex; the object-side surface of the third lens L3 is concave, and the image-side surface is concave; the object-side surface of the fourth lens L4 is convex, and the image-side surface is concave; the object-side surface of the fifth lens L5 is concave, and the image-side surface is convex; the object-side surface of the sixth lens L6 is convex, and the image-side surface is convex.

[0074] When the surface shape of the first lens L1 meets the above requirements, the incident angle of the lens can be controlled and the characteristic of long focal length can be achieved.

[0075] When the surface shapes of the second lens L2 and the third lens L3 meet the above requirements, they can effectively shrink light, reduce assembly tolerances, and improve production yields.

[0076] When the surface shapes of the fourth lens L4 and the fifth lens L5 meet the above requirements, the structures of the fourth lens L4 and the fifth lens L5 can be made symmetrical, which is beneficial to correcting off-axis aberrations and improving imaging quality.

[0077] When the surface shape of the sixth lens L6 meets the above requirements, it can be used in conjunction with the fifth lens L5 to optimize field curvature, and optimize performance such as the main ray angle and distortion.

[0078] At the same time, the surface shape of the lens affects the direction of light propagation and determines how the light bends when passing through the lens, which in turn affects the amount of light transmitted by the lens and the quality and characteristics of the imaging.

[0079] In this embodiment, by rationally matching the surface shapes of the various lenses, while satisfying the optical power requirements of each lens and achieving the desired optical performance indicators (such as small size and large target surface), it is beneficial to further reduce the total optical length of the entire telephoto lens, thereby realizing a miniaturized lens design. In addition, it can also make the path of light smoother when passing through the entire telephoto lens, reduce unnecessary reflection and absorption, and help improve imaging quality.

[0080] As a feasible implementation manner, the Abbe number of the first lens L1 is Vd1, 20.48≤Vd1≤59.84.

[0081] Among them, the Abbe number is an index used to represent the dispersion ability of a transparent medium. The more severe the dispersion of the medium, the smaller the Abbe number; conversely, the milder the dispersion of the medium, the larger the Abbe number.

[0082] In this embodiment, by setting the Abbe number Vd1 of the first lens L1 within the above range, the angle at which light enters the lens can be effectively controlled, so that it can better match the receiving characteristics of the image sensor, which helps to achieve the characteristic of a long focal length.

[0083] As a feasible implementation manner, the Abbe number of the second lens L2 is Vd2; the Abbe number of the third lens L3 is Vd3, and the refractive index is Nd3.

[0084] 41.00≤Vd2-Vd3≤68.00;1.48≤Nd3≤1.74.

[0085] The refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium. It is primarily used to describe a material's ability to refract light. Different materials have different refractive indices. The higher the refractive index, the greater the material's ability to bend light.

[0086] In this embodiment, the second lens L2 and the third lens L3 are made of a combination of materials with different chromatic aberration coefficients, and the refractive index of the third lens L3 is within the above-mentioned range, so that the dispersion can compensate for each other to achieve the purpose of achromatism, which is beneficial to improving the imaging performance of the lens.

[0087] As a feasible implementation method, Figure 1-Figure 3 As shown, the second lens L2 and the third lens L3 form a cemented lens group G1.

[0088] Among them, such as Figure 1-Figure 3 As shown, the second lens L2 and the third lens L3 can be bonded together by glue to form a cemented lens group G1.

[0089] In this embodiment, gluing the second lens L2 and the third lens L3 together can effectively correct the chromatic aberration of the lens, reduce the decentering sensitivity of the lens, balance the aberrations of the lens, and improve the imaging quality of the lens. At the same time, it can also reduce the assembly sensitivity of the lens, thereby reducing the difficulty of the lens processing technology and improving the assembly yield of the lens.

[0090] As a feasible implementation method, Figure 4 As shown, the distance between the second lens L2 and the third lens L3 on the optical axis is greater than 0.

[0091] The second lens L2 and the third lens L3 can be supported by a spacer. In this case, the second lens L2 and the third lens L3 are independent lenses. This reduces production costs and makes it easier to adjust and optimize the second lens L2 and the third lens L3, thereby helping to adapt to different optical design requirements and improve imaging quality.

[0092] As a feasible implementation manner, the refractive index of the fourth lens L4 is Nd4, the refractive index of the fifth lens L5 is Nd5; -0.04≤Nd5-Nd4≤0.15.

[0093] In this embodiment, the fourth lens L4 and the fifth lens L5 are made of a combination of materials with different refractive indices, and the refractive index difference between the fourth lens L4 and the fifth lens L5 satisfies the above range, which can correct off-axis aberrations and improve imaging quality.

[0094] As a feasible implementation manner, the total optical length of the telephoto lens is TTL, the optical back focus of the telephoto lens is BFL, the focal length of the telephoto lens is EFL, and the clear aperture of the sixth lens L6 is DT6.

[0095] 0.38≤DT6 / BFL≤0.55; 0.75≤(TTL-BFL) / EFL≤0.9.

[0096] The total optical length TTL of the telephoto lens refers to the distance from the optical axis center of the object-side surface of the first lens L1 to the image plane.

[0097] The optical back focus BFL of the telephoto lens refers to the distance from the optical axis center of the image-side surface of the sixth lens L6 to the image plane.

[0098] In this embodiment, by reasonably limiting the relationship between the total optical length TTL, the optical back focus BFL, the focal length EFL, and the clear aperture DT6 of the sixth lens L6, the entire lens structure can be ensured to be compact, highly integrated, and have a short total length and a small volume, while also ensuring sufficient installation space for the imaging sensor and the filter.

[0099] As a feasible implementation manner, the refractive index of the sixth lens L6 is Nd6, and 1.74≤Nd6≤2.05.

[0100] Among them, by setting the refractive index Nd6 of the sixth lens L6 to meet the above range, it is beneficial to optimize the main light angle, ensure that the entire lens structure is compact, highly integrated, and achieves a short total length and a small volume, while also ensuring that there is sufficient installation space for the imaging sensor and the filter.

[0101] As a feasible implementation method, Figure 1 、 Figure 2 and Figure 4 As shown, the telephoto lens further includes an aperture STO, which is located in the optical path between the fourth lens L4 and the fifth lens L5.

[0102] Among them, placing the aperture STO near the middle part of the telephoto lens is conducive to optimizing the path of light and ensuring that the light can be evenly distributed to the subsequent lens groups after passing through the aperture STO, thereby improving the imaging quality.

[0103] As a feasible implementation method, Figure 3 As shown, the telephoto lens further includes an aperture STO, which is located on the object-side surface of the first lens L1.

[0104] Among them, placing the aperture STO at the front end of the telephoto lens can better control the incident angle of the lens and help reduce the overall size of the lens.

[0105] As a feasible implementation method, Figure 1-Figure 4 As shown, the telephoto lens provided in this embodiment also includes a filter CG, which is located on the image side of the sixth lens L6. The filter CG can protect the image sensor from dust and pollution, thereby ensuring the imaging effect of the lens.

[0106] In some cases, the filter CG may also be used to correct specific aberrations or filter out unnecessary light, which is not specifically limited in this embodiment of the present invention.

[0107] The embodiments of the present invention can achieve the characteristics of a telephoto lens with a short overall length, a small size, and a large target area by reasonably allocating parameters such as the material, optical power, and center thickness of each lens.

[0108] Specific embodiments of the telephoto lens applicable to the above-mentioned embodiments will be further described below with reference to the accompanying drawings.

[0109] Example 1

[0110] Continue to refer Figure 1The telephoto lens provided in the first embodiment of the present invention includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a sixth lens L6, which are arranged in sequence from the object plane to the image plane along the optical axis.

[0111] The first lens L1 has positive refractive power, the second lens L2 has positive refractive power, the third lens L3 has negative refractive power, the fourth lens L4 has negative refractive power, the fifth lens L5 has negative refractive power, and the sixth lens L6 has positive refractive power.

[0112] The second lens L2 and the third lens L3 constitute a cemented lens group G1.

[0113] The aperture STO is located in the optical path between the fourth lens L4 and the fifth lens L5, and the filter CG is located on the image-side surface of the sixth lens L6.

[0114] Table 1 details the specific optical and physical parameters of each lens in the telephoto lens provided in Example 1 of the present invention in a feasible implementation manner. The telephoto lens in Table 1 corresponds to Figure 1 Telephoto lens shown.

[0115] Table 1 Design values ​​of optical physical parameters of telephoto lens

[0116]

[0117] The surface numbers in Table 1 are numbered according to the order of the surfaces of each lens, where "S1" represents the front surface of the first lens, "S2" represents the back surface of the first lens, and so on; "STO" represents the aperture of the lens; "IMA" represents the image plane of the lens; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface is bent toward the image plane, and a negative value represents that the surface is bent toward the object plane, where "Infinity" represents that the surface is a plane, the radius of curvature is infinite, and the distance is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index Nd represents the light deflection ability of the material between the current surface and the next surface, and a blank space represents that the current position is air with a refractive index of 1; the Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface, and a blank space represents that the current position is air; the semi-diameter represents the effective diameter of the light of the lens; the k value represents the numerical value of the conic coefficient of the aspheric surface.

[0118] In this embodiment, the aspheric cone coefficient of the aspheric lens in the telephoto lens can be defined by the following aspheric formula, but is not limited to the following expression method:

[0119]

[0120] Among them, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the curvature radius; k is the fitting cone coefficient; AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial, respectively.

[0121] For example, Table 2 describes in detail the aspheric coefficients of each lens in the first embodiment in a feasible implementation manner.

[0122] Table 2 Design values ​​of aspheric coefficients of each lens in telephoto lens

[0123]

[0124] The telephoto lens provided in Example 1 has a total optical length TTL of 14.5 mm, and an image height of 7 mm corresponds to an angle of 33.14°.

[0125] Figure 5 This is a graph of the spherical aberration of the telephoto lens provided in Example 1 of the present invention. The vertical axis represents the normalized aperture, with 0 indicating the optical axis and the vertical vertex representing the maximum pupil radius. The horizontal axis represents the offset from the ideal focus, measured in millimeters (mm). The different linear curves in the graph represent different wavelengths imaged by the telephoto lens. As can be seen from the graph, the axial aberration at different wavelengths is controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this telephoto lens is well controlled at all wavelengths, meeting the requirements of wide-spectrum applications.

[0126] Example 2

[0127] Continue to refer Figure 2 The telephoto lens provided in the second embodiment of the present invention includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a sixth lens L6, which are arranged in sequence from the object plane to the image plane along the optical axis.

[0128] The first lens L1 has positive refractive power, the second lens L2 has positive refractive power, the third lens L3 has negative refractive power, the fourth lens L4 has negative refractive power, the fifth lens L5 has negative refractive power, and the sixth lens L6 has positive refractive power.

[0129] The second lens L2 and the third lens L3 constitute a cemented lens group G1.

[0130] The aperture STO is located in the optical path between the fourth lens L4 and the fifth lens L5, and the filter CG is located on the image-side surface of the sixth lens L6.

[0131] Table 3 details the specific optical and physical parameters of each lens in the telephoto lens provided in Example 2 of the present invention in a feasible implementation manner. The telephoto lens in Table 3 corresponds to Figure 2 Telephoto lens shown.

[0132] Table 3 Design values ​​of optical physical parameters of telephoto lens

[0133]

[0134]

[0135] The surface numbers in Table 3 are numbered according to the order of the surfaces of each lens, where "S1" represents the front surface of the first lens, "S2" represents the back surface of the first lens, and so on; "STO" represents the aperture of the lens; "IMA" represents the image plane of the lens; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface is curved toward the image plane, and a negative value represents that the surface is curved toward the object plane, where "Infinity" represents that the surface is flat, the radius of curvature is infinite, and the distance is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index Nd represents the light deflection ability of the material between the current surface and the next surface, and a blank space represents that the current position is air with a refractive index of 1; the Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface, and a blank space represents that the current position is air; the semi-diameter represents the effective diameter of the light of the lens; the k value represents the numerical value of the conic coefficient of the aspheric surface.

[0136] In this embodiment, the aspheric cone coefficient of the aspheric lens in the telephoto lens can be defined by the following aspheric formula, but is not limited to the following expression method:

[0137]

[0138] Among them, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the curvature radius; k is the fitting cone coefficient; AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial, respectively.

[0139] For example, Table 4 details the aspheric coefficients of each lens in the second embodiment in a feasible implementation manner.

[0140] Table 4 Design values ​​of aspheric coefficients of each lens in telephoto lens

[0141]

[0142]

[0143] The telephoto lens provided in Example 2 has a total optical length TTL of 13.94 mm, and an image height of 7 mm corresponds to an angle of 33.22°.

[0144] Figure 6 This is a graph of the spherical aberration of the telephoto lens provided in Example 2 of the present invention. The vertical axis represents the normalized aperture, with 0 indicating the optical axis and the vertical vertex representing the maximum pupil radius. The horizontal axis represents the offset from the ideal focus, measured in millimeters (mm). The different linear curves in the graph represent different wavelengths imaged by the telephoto lens. As can be seen from the graph, the axial aberration at different wavelengths is controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this telephoto lens is well controlled at all wavelengths, meeting the requirements of wide-spectrum applications.

[0145] Example 3

[0146] Continue to refer Figure 3 The telephoto lens provided in the third embodiment of the present invention includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a sixth lens L6, which are arranged in sequence from the object plane to the image plane along the optical axis.

[0147] The first lens L1 has positive refractive power, the second lens L2 has positive refractive power, the third lens L3 has negative refractive power, the fourth lens L4 has negative refractive power, the fifth lens L5 has negative refractive power, and the sixth lens L6 has positive refractive power.

[0148] The second lens L2 and the third lens L3 constitute a cemented lens group G1.

[0149] The aperture STO is located on the object-side surface of the first lens L1, and the filter CG is located on the image-side surface of the sixth lens L6.

[0150] Table 5 details the specific optical and physical parameters of each lens in the telephoto lens provided in Example 3 of the present invention in a feasible implementation manner. The telephoto lens in Table 5 corresponds to Figure 3 Telephoto lens shown.

[0151] Table 5 Design values ​​of optical physical parameters of telephoto lens

[0152]

[0153] The surface numbers in Table 5 are numbered according to the order of the surfaces of each lens, where "S1" represents the front surface of the first lens, "S2" represents the back surface of the first lens, and so on; "STO" represents the aperture of the lens; "IMA" represents the image plane of the lens; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface is bent toward the image plane, and a negative value represents that the surface is bent toward the object plane, where "Infinity" represents that the surface is a plane, the radius of curvature is infinite, and the distance is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index Nd represents the light deflection ability of the material between the current surface and the next surface, and a blank space represents that the current position is air with a refractive index of 1; the Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface, and a blank space represents that the current position is air; the semi-diameter represents the effective diameter of the light of the lens; the k value represents the numerical value of the conic coefficient of the aspheric surface.

[0154] In this embodiment, the aspheric cone coefficient of the aspheric lens in the telephoto lens can be defined by the following aspheric formula, but is not limited to the following expression method:

[0155]

[0156] Among them, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the curvature radius; k is the fitting cone coefficient; AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial, respectively.

[0157] For example, Table 6 details the aspheric coefficients of each lens in Example 3 in a feasible implementation manner.

[0158] Table 6 Design values ​​of aspheric coefficients of each lens in telephoto lens

[0159]

[0160] The telephoto lens provided in Example 3 has a total optical length TTL of 14.37 mm, and an image height of 7 mm corresponds to an angle of 33.12°.

[0161] Figure 7This is a spherical aberration curve for the telephoto lens provided in Example 3 of the present invention. The vertical axis represents the normalized aperture, with 0 indicating the optical axis and the vertical vertex representing the maximum pupil radius. The horizontal axis represents the offset from the ideal focus, measured in millimeters (mm). The different linear curves in the figure represent different wavelengths imaged by the telephoto lens. As can be seen from the figure, the axial aberration at different wavelengths is controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this telephoto lens is well controlled at all wavelengths, meeting the requirements of wide-spectrum applications.

[0162] Example 4

[0163] Continue to refer Figure 4 The telephoto lens provided in the fourth embodiment of the present invention includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a sixth lens L6, which are arranged in sequence from the object plane to the image plane along the optical axis.

[0164] The first lens L1 has positive refractive power, the second lens L2 has positive refractive power, the third lens L3 has negative refractive power, the fourth lens L4 has negative refractive power, the fifth lens L5 has negative refractive power, and the sixth lens L6 has positive refractive power.

[0165] The distance between the second lens L2 and the third lens L3 on the optical axis is greater than 0.

[0166] The aperture STO is located in the optical path between the fourth lens L4 and the fifth lens L5, and the filter CG is located on the image-side surface of the sixth lens L6.

[0167] Table 7 details the specific optical and physical parameters of each lens in the telephoto lens provided in Example 4 of the present invention in a feasible implementation manner. The telephoto lens in Table 7 corresponds to Figure 4 Telephoto lens shown.

[0168] Table 7 Design values ​​of optical physical parameters of telephoto lens

[0169]

[0170] The surface numbers in Table 7 are numbered according to the order of the surfaces of each lens, where "S1" represents the front surface of the first lens, "S2" represents the back surface of the first lens, and so on; "STO" represents the aperture of the lens; "IMA" represents the image plane of the lens; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface is curved toward the image plane, and a negative value represents that the surface is curved toward the object plane, where "Infinity" represents that the surface is flat, the radius of curvature is infinite, and the distance is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index Nd represents the light deflection ability of the material between the current surface and the next surface, and a blank space represents that the current position is air with a refractive index of 1; the Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface, and a blank space represents that the current position is air; the semi-diameter represents the effective diameter of the light of the lens; the k value represents the numerical value of the conic coefficient of the aspheric surface.

[0171] In this embodiment, the aspheric cone coefficient of the aspheric lens in the telephoto lens can be defined by the following aspheric formula, but is not limited to the following expression method:

[0172]

[0173] Among them, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the curvature radius; k is the fitting cone coefficient; AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial, respectively.

[0174] For example, Table 8 details the aspheric coefficients of each lens in Example 4 in a feasible implementation manner.

[0175] Table 8 Design values ​​of aspheric coefficients of each lens in telephoto lens

[0176]

[0177] The telephoto lens provided in the fourth embodiment has a total optical length TTL of 14.5 mm, and an image height of 7 mm corresponding to an angle of 33.22°.

[0178] Figure 8This is a graph of the spherical aberration of the telephoto lens provided in Example 4 of the present invention. The vertical axis represents the normalized aperture, with 0 indicating the optical axis and the vertical vertex representing the maximum pupil radius. The horizontal axis represents the offset from the ideal focus, measured in millimeters (mm). The different linear curves in the graph represent different wavelengths imaged by the telephoto lens. As can be seen from the graph, the axial aberration at different wavelengths is controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this telephoto lens is well controlled at all wavelengths, meeting the requirements of wide-spectrum applications.

[0179] In order to more clearly illustrate the above embodiments, Table 9 details the specific optical and physical parameters of each lens in the telephoto lens provided in Embodiments 1 to 4 of the present invention.

[0180] Table 9 Design values ​​of optical physical parameters of telephoto lens

[0181]

[0182] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A telephoto lens, characterized in that: comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens arranged in sequence along the optical axis from the object plane to the image plane; The first lens has positive optical power; The second lens has positive optical power; The third lens has negative optical power; The fourth lens has negative optical power; The fifth lens has negative optical power; The sixth lens has positive optical power; The second lens, the third lens, and the sixth lens are glass spherical lenses; the first lens, the fourth lens, and the fifth lens are plastic aspherical lenses.

2. The telephoto lens according to claim 1, wherein: The optical power of the telephoto lens is The optical power of the first lens is The optical power of the second lens is The optical power of the third lens is The optical power of the fifth lens is The optical power of the sixth lens is 3. The telephoto lens according to claim 1, wherein: The object side surface of the first lens is convex, and the image side surface is concave; The object-side surface of the second lens is convex, and the image-side surface is convex; The object side surface of the third lens is concave, and the image side surface is concave; The object-side surface of the fourth lens is convex, and the image-side surface is concave; The object-side surface of the fifth lens is concave, and the image-side surface is convex; The object-side surface of the sixth lens is convex, and the image-side surface is convex.

4. The telephoto lens according to claim 1, wherein: The Abbe number of the first lens is Vd1, 20.48≤Vd1≤59.

84.

5. The telephoto lens according to claim 1, wherein: The Abbe number of the second lens is Vd2; The Abbe number of the third lens is Vd3, and the refractive index is Nd3; 41.00≤Vd2-Vd3≤68.00; 1.48≤Nd3≤1.

74.

6. The telephoto lens according to claim 1, wherein: The second lens and the third lens form a cemented lens group; or, A distance between the second lens and the third lens on the optical axis is greater than 0.

7. The telephoto lens according to claim 1, wherein: The refractive index of the fourth lens is Nd4, and the refractive index of the fifth lens is Nd5; -0.04≤Nd5-Nd4≤0.

15.

8. The telephoto lens according to claim 1, wherein: The total optical length of the telephoto lens is TTL, the optical back focus of the telephoto lens is BFL, the focal length of the telephoto lens is EFL, and the clear aperture of the sixth lens is DT6; 0.38≤DT6 / BFL≤0.55; 0.75≤(TTL-BFL) / EFL≤0.

9.

9. The telephoto lens according to claim 1, wherein: The refractive index of the sixth lens is Nd6, 1.74≤Nd6≤2.

05.

10. The telephoto lens according to claim 1, wherein: The telephoto lens further includes an aperture; The aperture is located in the optical path between the fourth lens and the fifth lens; or, The aperture is located on the object-side surface of the first lens.

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