A medium telephoto lens

Abstract

The utility model discloses a middle long focus lens, is arranged in order along the lens optical axis from object to image side: first lens, the aspheric plastic lens of positive focal power, its object side is the convex surface, and the image side is the concave surface, second lens, the aspheric plastic lens of negative focal power, its object side is the convex surface, and the image side is the concave surface, aperture diaphragm, third lens, the spherical glass lens of positive focal power, its object side is the convex surface, and the image side is the convex surface, fourth lens, the spherical glass lens of negative focal power, its object side is the concave surface, and the image side is the convex surface, fifth lens, the aspheric plastic lens of negative focal power, its object side is the concave surface, and the image side is the convex surface, sixth lens, the aspheric plastic lens of positive focal power, its object side is the convex surface, and the image side is the concave surface. The lens has higher imaging quality and smaller total length of lens, and has higher relative luminance, guarantees the clear of imaging quality.

Description

Technical Field

[0001] This utility model relates to the field of optical lens technology, and in particular to a medium-telephoto lens. Background Technology

[0002] Due to their unique focal length characteristics, medium-telephoto lenses are increasingly in demand in fields such as security monitoring, vehicle radar, and autonomous driving. As imaging technology advances, the quality requirements for medium-telephoto lenses are also rising. However, existing medium-telephoto lenses used in security applications suffer from drawbacks such as large size, high cost, low illumination, resulting in dark images or images only visible light, and poor night vision. Utility Model Content

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a medium-telephoto lens that, while maintaining a total focal length of 12mm, achieves high image quality and a relatively short total lens length, as well as high relative illumination, thus ensuring clear image quality.

[0004] The objective of this utility model is achieved through the following technical solution:

[0005] A medium-telephoto lens, characterized in that: along the lens optical axis, arranged sequentially from the object side to the image side:

[0006] The first lens is an aspherical plastic lens with positive optical power, wherein the object side is convex and the image side is concave.

[0007] The second lens is an aspherical plastic lens with negative optical power, whose object side is convex and image side is concave.

[0008] Aperture stop;

[0009] The third lens is a spherical glass lens with positive optical power, and its object side and image side are both convex.

[0010] The fourth lens is a spherical glass lens with negative optical power, wherein the object side is concave and the image side is convex.

[0011] The fifth lens is an aspherical plastic lens with negative optical power, wherein the object side is concave and the image side is convex.

[0012] The sixth lens is an aspherical plastic lens with positive optical power, wherein the object side is convex and the image side is concave.

[0013] A filter, wherein the filter is disposed on the image-side surface of the sixth lens;

[0014] A protective glass integrated on the image sensor, the protective glass being disposed on the image side of the filter;

[0015] An image acquisition element is disposed on the image side of the protective glass.

[0016] Furthermore, in this invention, considering the aberrations and temperature drift issues of the optical system, the focal lengths, refractive indices, and radii of curvature of the first, second, third, fourth, fifth, and sixth lenses respectively satisfy the following conditions:

[0017] f2 -14.31～-14.07 ND2 1.60～1.68 R21 +4.18～+4.21 R22 +2.32～+2.35 f3 +6.78～+6.85 ND3 1.71～1.78 R31 +8.87～+8.95 R32 -8.95～-8.87 f4 -15.78～-15.57 ND4 1.75～1.83 R41 -7.44～-7.39 R42 -20.77～-20.4 f5 -15.20～-14.75 ND5 1.60～1.68 R51 -2.18～-2.15 R52 -3.30～-3.27 f6 +7.87～+8.12 ND6 1.52～1.56 R61 +3.15～+3.21 R62 +9.87～+9.91

[0018] Where f1 is the focal length of the first lens, ND1 is the refractive index of the first lens, R11 is the radius of curvature of the object side surface of the first lens, and R12 is the radius of curvature of the image side surface of the first lens.

[0019] f2 is the focal length of the second lens, ND2 is the refractive index of the second lens, R21 is the radius of curvature of the object side surface of the second lens, and R22 is the radius of curvature of the image side surface of the second lens.

[0020] f3 is the focal length of the third lens, ND3 is the refractive index of the third lens, R31 is the radius of curvature of the object side of the third lens, and R32 is the radius of curvature of the image side of the third lens.

[0021] f4 is the focal length of the fourth lens, ND4 is the refractive index of the fourth lens, R41 is the radius of curvature of the object side of the fourth lens, and R42 is the radius of curvature of the image side of the fourth lens.

[0022] f5 is the focal length of the fifth lens, ND5 is the refractive index of the fifth lens, R51 is the radius of curvature of the object side of the fifth lens, and R52 is the radius of curvature of the image side of the fifth lens.

[0023] f6 is the focal length of the sixth lens, ND6 is the refractive index of the sixth lens, R61 is the radius of curvature of the object side surface of the sixth lens, and R62 is the radius of curvature of the object side surface of the sixth lens.

[0024] Focal length: "+" indicates that the lens has positive power, and "-" indicates that the lens has negative power. The unit is mm.

[0025] Radius of curvature: "+" indicates that the surface bends toward the image plane, and "-" indicates that the surface bends toward the object plane. The unit is mm.

[0026] Furthermore, in this invention, to achieve better performance of the optical system, we need to rationally select lens materials, rationally allocate the focal lengths of each lens, and rationally optimize the optical system during the design process to correct system aberrations and ultimately optimize the performance of the optical system. The ratio of the focal length of each lens to the total focal length of the lens also satisfies the following conditions:

[0027] 2.1≤|f1 / f|≤2.2,

[0028] 0.4 ≤ |f² / f| ≤ 1.3

[0029] 0.4≤|f³ / f|≤0.7,

[0030] 1.3 ≤ |f⁴ / f| ≤ 2.3

[0031] 0.9 ≤ |f⁵ / f| ≤ 1.4

[0032] 0.5≤|f6 / f|≤0.7,

[0033] In the formula, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, and f6 is the focal length of the sixth lens.

[0034] Furthermore, in this utility model,

[0035] The aperture of the lens is F#, which satisfies F#≤1.6;

[0036] The total focal length of the lens is f, which satisfies f≤12mm;

[0037] The total optical length of the lens is TTL, which satisfies TTL≤22.5mm;

[0038] Furthermore, in this utility model, the lens satisfies the following relationship:

[0039] IH / TTL≥0.15,

[0040] TTL / f≤2.0,

[0041] OBFL / TTL ≥ 0.22;

[0042] In the formula, f is the total focal length of the lens, TTL is the total optical length of the lens, OBFL is the optical back focal length of the lens, the optical back focal length is the distance from the point on the image side of the sixth lens closest to the image plane to the image plane, and IH is the full image height of the 1 / 2.7” chip paired with the lens.

[0043] Furthermore, in this invention, the center thickness of the first lens is T1, which satisfies 2.87≤T1≤2.88;

[0044] The center thickness of the second lens is T2, which satisfies 1.96≤T2≤2.03;

[0045] The center thickness of the third lens is T3, which satisfies 4.5≤T3≤4.6;

[0046] The center thickness of the fourth lens is T4, which satisfies 2.47≤T4≤2.77;

[0047] The center thickness of the fifth lens is T5, which satisfies 0.97≤T5≤0.98;

[0048] The center thickness of the sixth lens is T6, which satisfies 1.77≤T6≤1.8.

[0049] Furthermore, in this invention, the center air thickness of the first lens and the second lens is D1, which satisfies 0.06≤D1≤0.07;

[0050] The central air thickness of the second lens and the third lens is D2, which satisfies 1.09≤D2≤1.1;

[0051] The central air thickness of the third lens and the fourth lens is D3, which satisfies 0.09≤D3≤0.15;

[0052] The central air thickness of the fourth lens and the fifth lens is D4, which satisfies 1.02≤D4≤1.41;

[0053] The central air thickness of the fifth lens and the sixth lens is D5, which satisfies 0.05≤D5≤0.06.

[0054] Furthermore, the aspherical surfaces of the first lens, second lens, fifth lens, and sixth lens satisfy the following formula:

[0055]

[0056] In the formula, Z is the sag of the lens along the optical axis, k is the conic coefficient of the quadratic surface, γ is the lens height, c is the lens curvature, and A, B, C, D, E, F, and G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspherical polynomial.

[0057] The beneficial effects of this utility model are:

[0058] This invention achieves a 2G4P optical architecture through a reasonable arrangement of glass and plastic lens combinations, which has high resolution and a small overall lens length while meeting the requirement of a total lens focal length of 12mm.

[0059] By rationally combining glass and plastic lenses to adjust the overall proportions and light flow, the structure between the lenses is kept compact, the processing cost is low, and it features small size, light weight, and high cost performance.

[0060] The lens has high relative illumination, eliminating vignetting in the captured images. At the same time, the system phase difference is well corrected, resulting in excellent optical performance. The images are clear in real-world shooting at high temperatures of +70℃ and low temperatures of -30℃. It also has a small infrared defocus, which makes the night vision images better. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the optical structure of Embodiment 1 of the present invention;

[0062] Figure 2 This is a magnification color difference diagram of visible light 435-656nm in Embodiment 1 of this utility model;

[0063] Figure 3 This is a relative illuminance diagram of visible light at 546nm for Embodiment 1 of this utility model;

[0064] Figure 4 This is a visible light 435-656nm FFT MTF curve of Embodiment 1 of this utility model;

[0065] Figure 5 This is a defocusing curve at room temperature +20℃ for visible light 435-656nm (125lp / mm) in Embodiment 1 of this utility model;

[0066] Figure 6 This is a defocusing curve of visible light 435-656nm (125lp / mm) at room temperature -30℃ for Embodiment 1 of this utility model;

[0067] Figure 7 This is a defocusing curve at room temperature +70℃ for visible light 435-656nm (125lp / mm) in Embodiment 1 of this utility model;

[0068] Figure 8 This is a defocusing curve at room temperature +20℃ for 1850nm (125lp / mm) in an embodiment of this utility model.

[0069] Figure 9 This is a schematic diagram of the optical structure of Embodiment 2 of the present invention;

[0070] Figure 10 This is the relative illuminance diagram of visible light at 546nm in Embodiment 2 of this utility model;

[0071] Figure 11 This is a magnification color difference diagram of visible light 435-656nm in Embodiment 2 of this utility model;

[0072] Figure 12 This is a defocusing curve at room temperature +20℃ for visible light 435-656nm (125lp / mm) in Embodiment 2 of this utility model;

[0073] Figure 13 This is a visible light FFF MTF vs. Field curve diagram of Embodiment 2 of this utility model;

[0074] Figure 14 This is a visible light 435-656nm FFT MTF curve of Embodiment 2 of this utility model;

[0075] Reference numerals: 1-First lens; 2-Second lens; 3-Third lens; 4-Fourth lens; 5-Fifth lens; 6-Sixth lens; 7-Filter; 8-Protective glass; 9-Image acquisition element; 10-Aperture stop. Detailed Implementation

[0076] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. In this specification, the expressions "first," "second," "third," etc., are only used to distinguish one feature from another, and do not indicate any limitation on the features. The shape of the spherical or aspherical surface is not limited to the spherical or aspherical shapes shown in the drawings. The drawings are for illustrative purposes only and are not strictly drawn to scale.

[0077] In this invention, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region; if the lens surface is not defined as convex, concave, or flat, it means that the lens surface can be convex, concave, or flat. The surface of each lens closest to the object being photographed is called the object-side surface of the lens, and the surface of each lens closest to the imaging plane is called the image-side surface of the lens.

[0078] Unless otherwise specified, all terms used in this invention (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the same meaning as they have in the context of the relevant art and shall not be interpreted in an idealized or overly formal sense, unless expressly so defined in this invention.

[0079] It should be noted that, where there is no conflict, the embodiments and features in the embodiments of this utility model can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model.

[0080] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0081] This utility model embodiment provides a medium-to-long telephoto lens, defining the surface of the lens adjacent to the object plane as the object-side surface and the surface of the lens adjacent to the image plane as the image-side surface, arranged sequentially from left to right along the lens optical axis:

[0082] The first lens 1 is an aspherical plastic lens with positive optical power, wherein the object side is convex and the image side is concave.

[0083] The second lens 2 is an aspherical plastic lens with negative optical power, whose object side is convex and image side is concave.

[0084] Aperture stop 10;

[0085] The third lens 3 is a spherical glass lens with positive optical power, and its object side and image side are both convex.

[0086] The fourth lens 4 is a spherical glass lens with negative optical power, whose object side is concave and image side is convex.

[0087] The fifth lens 5 is an aspherical plastic lens with negative optical power, whose object side is concave and image side is convex.

[0088] The sixth lens 6 is an aspherical plastic lens with positive optical power, wherein the object side is convex and the image side is concave.

[0089] Filter 7, which is made of H-K9L glass;

[0090] The protective glass 8 and the image acquisition element 9 are integrated on the image acquisition element 9.

[0091] The optical lens used in this drone lens can be made of either glass or plastic. Using plastic effectively reduces production costs. Using glass effectively improves the lens's thermal stability. This lens employs a hybrid combination of two spherical glass elements and four aspherical plastic elements, resulting in a compact structure that is lightweight, high-performance, and low-cost, offering excellent value for money.

[0092] In this invention, considering the aberrations and temperature drift of the optical system, the focal lengths, refractive indices, and radii of curvature of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 respectively satisfy the following conditions:

[0093]

[0094]

[0095] Where f1 is the focal length of the first lens 1, ND1 is the refractive index of the first lens 1, R11 is the radius of curvature of the object side surface of the first lens 1, and R12 is the radius of curvature of the image side surface of the first lens 1.

[0096] f2 is the focal length of the first lens 2, ND2 is the refractive index of the first lens 2, R21 is the radius of curvature of the object side surface of the second lens 2, and R22 is the radius of curvature of the image side surface of the second lens 2.

[0097] f3 is the focal length of the first lens 3, ND3 is the refractive index of the first lens 3, R31 is the radius of curvature of the object side surface of the third lens 3, and R32 is the radius of curvature of the image side surface of the first lens 3.

[0098] f4 is the focal length of the first lens 4, ND4 is the refractive index of the first lens 4, R41 is the radius of curvature of the object side surface of the fourth lens 4, and R42 is the radius of curvature of the image side surface of the fourth lens 4.

[0099] f5 is the focal length of the first lens 5, ND5 is the refractive index of the first lens 5, R51 is the radius of curvature of the object side surface of the fifth lens 5, and R52 is the radius of curvature of the image side surface of the fifth lens 5.

[0100] f6 is the focal length of the first lens 6, ND6 is the refractive index of the first lens 6, R61 is the radius of curvature of the object side surface of the sixth lens 6, and R62 is the radius of curvature of the image side surface of the sixth lens 6.

[0101] Focal length: "+" indicates that the lens has positive power, and "-" indicates that the lens has negative power. The unit is mm.

[0102] Radius of curvature: "+" indicates that the surface bends toward the image plane, and "-" indicates that the surface bends toward the object plane. The unit is mm.

[0103] In this invention, to achieve better performance of the optical system, the design process involves rationally selecting lens materials, rationally allocating the focal lengths of each lens, and rationally optimizing the optical system to correct aberrations and ultimately optimize its performance. In this invention, the focal length of the first lens 1 is f1, the second lens 2 is f2, the third lens 3 is f3, the fourth lens 4 is f4, the fifth lens 5 is f5, and the sixth lens 6 is f6. The total focal length of the lens is f, and the ratio of the focal length of each lens to the total focal length of the system satisfies the following condition:

[0104] 2.1≤|f1 / f|≤2.2,

[0105] 0.4 ≤ |f² / f| ≤ 1.3

[0106] 0.4≤|f³ / f|≤0.7,

[0107] 1.3 ≤ |f⁴ / f| ≤ 2.3

[0108] 0.9 ≤ |f⁵ / f| ≤ 1.4

[0109] 0.5≤|f6 / f|≤0.7.

[0110] In this invention, F# is the aperture of the lens, f is the total focal length of the lens, TTL is the total optical length of the lens, OBFL is the optical back focal length of the lens, and the optical back focal length of the lens is the distance from the point on the image side of the sixth lens 6 closest to the image plane to the image plane; IH is the full image height of the 1 / 2.7” chip paired with the lens; they satisfy the following relationship:

[0111] F#≤1.6;

[0112] f≤12mm;

[0113] TTL≤22.5mm;

[0114] IH / TTL ≥ 0.15;

[0115] TTL / f≤2.0;

[0116] OBFL / TTL≥0.22.

[0117] In this invention, the center thickness of the first lens 1 is T1, which satisfies 2.87≤T1≤2.88;

[0118] The center thickness of the second lens 2 is T2, which satisfies 1.96≤T2≤2.03;

[0119] The center thickness of the third lens 3 is T3, which satisfies 4.5≤T3≤4.6;

[0120] The center thickness of the fourth lens 4 is T4, which satisfies 2.47≤T4≤2.77;

[0121] The center thickness of the fifth lens 5 is T5, which satisfies 0.97≤T5≤0.98;

[0122] The center thickness of the sixth lens 6 is T6, which satisfies 1.77≤T6≤1.8.

[0123] In this invention, the central air thickness of the first lens 1 and the second lens 2 is D1, which satisfies 0.06≤D1≤0.07;

[0124] The central air thickness of the second lens 2 and the third lens 3 is D2, which satisfies 1.09≤D2≤1.1;

[0125] The central air thickness of the third lens 3 and the fourth lens 4 is D3, which satisfies 0.09≤D3≤0.15;

[0126] The central air thickness of the fourth lens 4 and the fifth lens 5 is D4, which satisfies 1.02≤D4≤1.41;

[0127] The central air thickness of the fifth lens 5 and the sixth lens 6 is D5, which satisfies 0.05≤D5≤0.06.

[0128] In this invention, the aspherical surfaces of the first lens 1, the second lens 2, the fifth lens 5, and the sixth lens 6 can all be defined by the following equation for even-order aspherical surfaces:

[0129]

[0130] In the formula, Z is the sag of the lens along the optical axis, k is the conic coefficient of the quadratic surface, γ is the lens height, c is the lens curvature, and A, B, C, D, E, F, and G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspherical polynomial.

[0131] The following provides specific embodiments based on the above-described configuration of this utility model, thereby specifically illustrating the medium-telephoto lens of this utility model. To better understand and implement this utility model, it will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0132] The main element symbols in the specific embodiments of this utility model are explained in Table 1.

[0133] Table 1

[0134] S2 The image side of the first lens S11 The image side of the fifth lens S3 Second lens object side S12 The sixth lens object side S4 The image side of the second lens S13 The image side of the sixth lens S5 Aperture S14 Filter side S6 The third lens object side S15 Filter image from the side S7 The image of the third lens is on the side. S16 Protective glass like the side S8 Fourth lens object side S17 Protective glass like the side S9 The image side of the fourth lens

[0135] The data summary of specific embodiments of this utility model is shown in Table 2 below:

[0136] Table 2

[0137]

[0138]

[0139] Example 1

[0140] Reference Figure 1 The diagram shown is a schematic representation of the optical structure of Embodiment 1. In this embodiment, the lens aperture value F# = 1.6, the total focal length f = 12mm, the total optical length TTL = 22.5mm, and the lens is fitted with a 1 / 2.7” inch chip.

[0141] In this embodiment, in order to make the optical system perform better, the design process should include the reasonable selection of lens materials, the reasonable allocation of the focal length of each lens, and the reasonable optimization of the optical system to correct the aberrations of the system and ultimately optimize the performance of the optical system.

[0142] In this embodiment, the radius of curvature (unit: mm), center thickness d (unit: mm), refractive index (ND), Abbe constant (VD), and aspherical K-value (Conic) of the first lens 1, second lens 2, third lens 3, fourth lens 4, fifth lens 5, and sixth lens 6 are shown in Table 3.

[0143] Table 3

[0144]

[0145]

[0146] In Table 3, the radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "Infinity" indicates that the surface is flat. The thickness represents the central axial distance from the current surface to the next surface. The refractive index represents the ability of the current lens material to deflect light. The Abbe number represents the dispersion characteristics of the current lens material. The k-value represents the value of the best-fit conic coefficient of the aspherical surface.

[0147] In this embodiment, the aspherical surfaces of the first lens 1, the second lens 2, the fifth lens 5, and the sixth lens 6 can all be defined using the equations for even-order aspherical surfaces described above. Table 4 provides the coefficients for each optical surface.

[0148] Table 4

[0149]

[0150]

[0151] Please see Figure 2The diagram shown is a magnification chromatic aberration diagram of the lens in this embodiment. The horizontal axis represents the intersection position of the light ray and the image plane (unit: mm), and the vertical axis represents different field-of-view angles of the lens. From Figure 2 As can be seen, the on-axis color difference is less than 3μm.

[0152] refer to Figure 3 The image shows the relative illuminance of the lens at 546nm in this embodiment. The image shows that the relative illuminance of the lens at the maximum field of view is greater than 60%, which means that the amount of light entering the lens is sufficient and ensures that there will be no vignetting in the actual shooting image even when the lens is used in a relatively dark environment.

[0153] Reference Figure 4 The figure shows the MTF vs Frequency curves of the lens in the visible light range of 435-656nm in this embodiment. The horizontal axis represents frequency (unit: lp / mm), with a wide range from 0 lp / mm to 200 lp / mm. The vertical axis represents the MTF value. Figure 4 As can be seen, the MTF value of the lens is above 0.3 at a spatial frequency of 200 lp / mm, indicating that the lens has high resolution and good MTF performance in the visible light 435-656nm field of view.

[0154] Reference Figure 5 , 6 As shown in Figures 7 and 8, the lens in this embodiment exhibits defocus curves at room temperature, -30°C, and +70°C in the visible light range of 435-656nm. The defocus amount is less than 6μm in all cases. This small defocus amount ensures that the lens can capture high-definition images at both -30°C and +70°C.

[0155] Reference Figure 8 As shown, this is the MTF defocus curve of the lens at room temperature with a wavelength of 850nm in this embodiment. The defocus amount is less than 9μm and it has a high MTF peak value. The small defocus amount and high MTF peak value ensure that the lens can capture high-definition images in night vision.

[0156] Example 2

[0157] Reference Figure 9 The diagram shown is a schematic representation of the optical structure of Embodiment 2. In this embodiment, the lens aperture value F# = 1.6, the total focal length f = 11.6 mm, and the total optical length TTL = 22.5 mm.

[0158] In this embodiment, the radius of curvature (unit: mm), center thickness d (unit: mm), refractive index (ND), Abbe constant (VD), and aspherical K-value (Conic) of the first lens 1, second lens 2, third lens 3, fourth lens 4, fifth lens 5, and sixth lens 6 are shown in Table 5.

[0159] Table 5

[0160] S1 44.14 2.87 1.53 55.7 51.50 S2 -17.29 0.07 -84.26 S3 4.21 1.96 1.64 24.0 -1.30 S4 2.35 1.31 -2.23 S5 Infinity -0.22 S6 8.95 4.50 1.73 54.7 S7 -8.95 0.15 S8 -7.44 2.77 1.80 25.5 S9 -20.77 1.02 S10 -2.18 0.97 1.64 24.0 -4.32 S11 -3.30 0.06 -4.31 S12 3.21 1.80 1.53 55.7 -5.67 S13 9.91 3.92 -51.05 S14 Infinity 0.61 1.52 64.2 S15 Infinity 0.69

[0161] In Table 5, the radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "Infinity" indicates that the surface is flat. The thickness represents the central axial distance from the current surface to the next surface. The refractive index represents the ability of the current lens material to deflect light. The Abbe number represents the dispersion characteristics of the current lens material. The k-value represents the value of the best-fit conic coefficient of the aspherical surface.

[0162] In this embodiment, the aspherical surfaces of the first lens 1, the second lens 2, the fifth lens 5, and the sixth lens 6 can all be defined using the equations for even-order aspherical surfaces described above. Table 6 provides the coefficients for each optical surface.

[0163] Table 6

[0164]

[0165]

[0166] refer to Figure 10 The image shows the relative illuminance of the lens at 546nm in this embodiment. The image shows that the relative illuminance of the lens at the maximum field of view is greater than 65%, which means that the amount of light entering the lens is sufficient and ensures that there will be no vignetting in the actual shooting image even when the lens is used in a relatively dark environment.

[0167] Please see Figure 11 The diagram shown is a magnification chromatic aberration diagram of the lens in this embodiment. The horizontal axis represents the intersection position of the light ray and the image plane (unit: mm), and the vertical axis represents different field-of-view angles of the lens. From Figure 11 As can be seen, the on-axis color difference is less than 2μm.

[0168] Reference Figure 12 The figure shows the defocus curve of the lens in this embodiment at room temperature under visible light 435-656nm. The horizontal axis represents the focus shift in millimeters, and the vertical axis represents the modulus of the OTF. The peak value in the center field of view exceeds 0.6.

[0169] Reference Figure 13The figure shows the FFF MTF vs. Field plot of the lens in this embodiment at room temperature under visible light (435-656nm). The horizontal axis represents the image-side half-image height, and the vertical axis represents the Modulus of the OTF. The figure shows plots at three different frequencies. At 30 cyc / mm, the OTF values ​​are all greater than 0.8, and at 180 cyc / mm, the OTF values ​​are generally above 0.4.

[0170] Reference Figure 14 The figure shows the MTF vs Frequency curves of the lens in the visible light range of 435-656nm in this embodiment. The horizontal axis represents frequency (unit: lp / mm), with a wide range from 0 lp / mm to 200 lp / mm. The vertical axis represents the MTF value. Figure 14 As can be seen, the MTF value of the lens is above 0.3 at a spatial frequency of 200 lp / mm, indicating that the lens has high resolution and good MTF performance in the visible light 435-656nm field of view.

[0171] In summary, this medium-telephoto lens is composed of a hybrid structure of two spherical glass elements and four aspherical plastic elements, resulting in a compact design. The optical focal length is 12mm, and the aperture can be F#≤1.6, providing high relative illumination and ensuring no vignetting during shooting. Simultaneously, system aberrations are well corrected, resulting in excellent optical performance. In terms of manufacturability, the lenses are insensitive, with simple and easy-to-manufacture lens surfaces and a compact inter-lens structure, leading to relatively low processing costs compared to other lenses on the market and offering high cost-effectiveness. Furthermore, through reasonable lens material selection, optical power distribution, and optical design optimization, this invention enables 24 / 7 all-weather high-definition monitoring, producing clear images at temperatures ranging from +70℃ to -30℃. It also features minimal infrared defocus, resulting in good night vision images.

[0172] The above description merely illustrates several embodiments of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and this utility model also intends to include these modifications and variations.

Claims

1. A medium telephoto lens characterized by: Set sequentially from the object side to the image side along the lens optical axis: The first lens is an aspherical plastic lens with positive optical power, wherein the object side is convex and the image side is concave. The second lens is an aspherical plastic lens with negative optical power, whose object side is convex and image side is concave. Aperture stop; The third lens is a spherical glass lens with positive optical power, and its object side and image side are both convex. The fourth lens is a spherical glass lens with negative optical power, wherein the object side is concave and the image side is convex. The fifth lens is an aspherical plastic lens with negative optical power, wherein the object side is concave and the image side is convex. The sixth lens is an aspherical plastic lens with positive optical power, wherein the object side is convex and the image side is concave.

2. The medium telephoto lens of claim 1, wherein: The aperture of the lens is F#, which satisfies F#≤1.

6.

3. The medium telephoto lens of claim 1, wherein: The total focal length of the lens is f, which satisfies f≤12mm.

4. The medium telephoto lens of claim 1, wherein: The total optical length of the lens is TTL, which satisfies TTL≤22.5mm.

5. The medium telephoto lens of claim 1, wherein: The refractive index ranges of the first lens, second lens, third lens, fourth lens, fifth lens and sixth lens are 1.52~1.56, 1.60~1.68, 1.71~1.78, 1.75~1.83, 1.60~1.68 and 1.52~1.56 respectively.

6. The medium telephoto lens of claim 1, wherein: The focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens are respectively +23.48 to +25, -14.31 to -14.07, +6.78 to +6.85, -15.78 to -15.57, -15.20 to -14.75, and +7.87 to +8.

12. Here, "+" indicates that the lens has positive optical power, and "-" indicates that the lens has negative optical power.

7. The medium telephoto lens of claim 1, wherein: The ranges of the object surface radii of curvature for the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens are +44.14 to +45.23, +4.18 to +4.21, +8.87 to +8.95, -7.44 to -7.39, -2.18 to -2.15, and +3.15 to +3.21, respectively. The image-side surface curvature radii of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens, respectively, range from -18.72 to -17.29, +2.32 to +2.35, -8.95 to -8.87, -20.77 to -20.4, -3.30 to -3.27, and +9.87 to +9.

91. In this context, "+" indicates that the lens surface bends towards the image plane, and "-" indicates that the lens surface bends towards the object plane. The radius of curvature is measured in mm.

8. A medium telephoto lens according to claim 1, characterized in that: The central air thickness of the first lens and the second lens is D1, which satisfies 0.06≤D1≤0.07; The central air thickness of the second lens and the third lens is D2, which satisfies 1.09≤D2≤1.1; The central air thickness of the third lens and the fourth lens is D3, which satisfies 0.09≤D3≤0.15; The central air thickness of the fourth lens and the fifth lens is D4, which satisfies 1.02≤D4≤1.41; The central air thickness of the fifth lens and the sixth lens is D5, which satisfies 0.05≤D5≤0.

06.

9. The medium telephoto lens of claim 1, wherein: The lens also includes: A filter, wherein the filter is disposed on the image-side surface of the sixth lens; A protective glass integrated on the image sensor, the protective glass being disposed on the image side of the filter; An image acquisition element is disposed on the image side of the protective glass.

10. The medium telephoto lens of claim 1, wherein: The aspherical surfaces of the first lens, the second lens, the fifth lens, and the sixth lens satisfy the following formula: In the formula, Z is the sag of the lens along the optical axis, k is the conic coefficient of the quadratic surface, γ is the lens height, c is the lens curvature, and A, B, C, D, E, F, and G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspherical polynomial.

Images