Fixed focus optical system

Abstract

The invention discloses a fixed-focus optical system, which relates to the technical field of optical systems and is provided with an object side and an image side which are correspondingly arranged along the direction of an optical axis. The fixed-focus optical system comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and an image plane which are sequentially arranged from the object side to the image side, so that the distance between the vertex of the object side surface of the first lens of the fixed-focus optical system and the image plane is controlled within 16 mm; the field angle can reach 110 degrees, and the fixed focus optical system meets the following conditions:-9 lt; f1lt; -4; the yield is-55lt; f2lt; f2lt; -35; and 4lt; f3lt; f3t; 8; 8 lt; f4lt; f4t; 12; the thickness is-40 lt; f5lt; f5t; -20; and 4lt; f61t; f61t; 8; the yield is-15 lt; f7lt; f7lt; -8; the volume is 40 lt; f81t; f81t; 60). Through the arrangement, the fixed-focus optical system has the good performances of large visual angle, high pixel, very good athermalization and the like, the visual field is wider, the obtained data information is more sufficient, meanwhile, the fixed-focus optical system can stably work in the environment with the large temperature difference of 0 DEG C to 65 DEG C, and the application range is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of optical systems, and particularly to a fixed-focus optical system. Background Art

[0002] With the increasingly widespread application of video communication, the requirement for the viewing angle is also increasing. Wide-angle lenses have received more and more attention due to their advantages of large viewing angle and wide shooting frame. However, existing wide-angle lenses generally have problems such as large distortion, small target surface, large volume, and unclear imaging, making it difficult to meet the usage requirements in various scenarios. In particular, the demand for high-resolution, large-target-surface, and compact wide-angle lenses in the high-end market is still increasing. Summary of the Invention The main object of the present invention is to propose a fixed-focus optical system, aiming to improve the problems of large distortion, small target surface, large volume, and unclear imaging of existing lenses.

[0003] To achieve the above object, the fixed-focus optical system proposed by the present invention has an object side and an image side arranged correspondingly along the optical axis direction. The fixed-focus optical system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and an image plane arranged in sequence from the object side to the image side, such that the distance between the vertex of the object side surface of the first lens of the fixed-focus optical system and the image plane is controlled within 16 mm, and the viewing angle can reach 110°. The fixed-focus optical system satisfies the following conditions: -9 < f1 < -4; and -55 < f2 < -35; and 4 < f3 < 8; and 8 < f4 < 12; and -40 < f5 < -20; and 4 < f6 < 8; and -15 < f7 < -8; and 40 < f8 < 60; Wherein, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the eighth lens is f8.

[0004] In one embodiment, the optical power of the first lens is negative, the object side surface of the first lens is convex, and the image side surface is concave; The optical power of the second lens is negative, the object side surface of the second lens is convex, and the image side surface is concave; The optical power of the third lens is positive, the object side surface of the third lens is convex, and the image side surface is flat; The optical power of the fourth lens is positive, the object side surface of the fourth lens is convex, and the image side surface is convex; The optical power of the fifth lens is negative, the object side surface of the fifth lens is concave, and the image side surface is convex; The sixth lens has a positive optical power, and the object side of the sixth lens is concave, while the image side is convex. The seventh lens has a negative optical power, and the object side of the seventh lens is concave while the image side is convex. The eighth lens has a positive optical power, and its object-side surface is convex while its image-side surface is concave.

[0005] In one embodiment, the first lens, the second lens, the fourth lens, the fifth lens, the seventh lens, and the eighth lens are configured as plastic aspherical lenses; The third lens and the sixth lens are configured as glass aspherical lenses.

[0006] In one embodiment, the refractive index of the first lens is n1, where 1.50 ≤ n1 ≤ 1.60; The refractive index of the second lens is n2, where 1.60 ≤ n2 ≤ 1.70; The refractive index of the third lens is n3, where 1.75 ≤ n3 ≤ 1.90; The refractive index of the fourth lens is n4, where 1.50 ≤ n4 ≤ 1.60; The refractive index of the fifth lens is n5, where 1.60 ≤ n5 ≤ 1.70; The refractive index of the sixth lens is n6, where 1.40 ≤ n6 ≤ 1.55; The refractive index of the seventh lens is n7, where 1.60 ≤ n7 ≤ 1.70; The refractive index of the eighth lens is n8, where 1.50 ≤ n8 ≤ 1.60.

[0007] In one embodiment, the dispersion coefficient of the first lens is v1, where 50.0 ≤ v1 ≤ 70.0; The dispersion coefficient of the second lens is v2, 18.0≤v2≤26.0; The dispersion coefficient of the third lens is v3, 35.0≤v3≤60.0; The dispersion coefficient of the fourth lens is v4, 50.0≤v4≤70.0; The dispersion coefficient of the fifth lens is v5, 18.0≤v5≤26.0; The dispersion coefficient of the sixth lens is v6, 75.0≤v6≤100.0; The dispersion coefficient of the seventh lens is v7, 18.0≤v7≤26.0; The dispersion coefficient of the eighth lens is v8, where 50.0 ≤ v8 ≤ 70.0.

[0008] In one embodiment, the aperture value of the fixed-focus optical system is F, where 2.0 ≤ F ≤ 2.4.

[0009] In one embodiment, the diameter of the first lens is D1, where D1 < 14 mm.

[0010] In one embodiment, the diameter of the image plane is IC, where 9.0 mm ≤ IC ≤ 11.2 mm.

[0011] In one embodiment, the effective focal length of the fixed-focus optical system is EFL, and TTL / EFL ≤ 4.

[0012] In one embodiment, the fixed-focus optical system further includes an aperture stop disposed between the third lens and the fourth lens; and / or, The fixed-focus optical system further includes a filter disposed between the eighth lens and the image plane; and / or, The fixed-focus optical system also includes a photosensitive chip, which is disposed on the image-side of the eighth lens, and the end face of the photosensitive chip facing the object side forms the image plane.

[0013] In the technical solution of this invention, the fixed-focus optical system is composed of eight lenses. By setting the focal length of the first lens to a negative value, the fixed-focus optical system can collect light, thereby effectively increasing the field of view and correcting astigmatism and field curvature. Furthermore, by setting the focal length of the third lens to a positive value, the third lens can bear a larger optical power of the fixed-focus optical system, thereby changing the propagation direction of the light beam and making it more conducive to the beam forming on the image plane. This configuration, through the comprehensive arrangement of the focal lengths of the eight lenses, achieves a compact and lightweight design. The rational arrangement of the eight lenses improves image quality. Furthermore, by combining different lenses and rationally allocating optical power, the fixed-focus optical system possesses excellent performance characteristics such as a wide viewing angle, high pixel count, and very good thermal distortion reduction. It offers a wider field of view, obtains more comprehensive data information, and can operate stably in environments with large temperature differences from 0℃ to 65℃, making it widely applicable. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0015] Figure 1This is a schematic diagram of the structure of an embodiment of the fixed-focus optical system provided by the present invention; Figure 2 This is a schematic diagram of the spherical aberration curve of the fixed-focus optical system provided by the present invention; Figure 3 A schematic diagram of the light aberration curve of the fixed-focus optical system provided by the present invention; Figure 4 This is a schematic diagram of the field curvature distortion of the fixed-focus optical system provided by the present invention; Figure 5 A schematic diagram of the fixed-focus optical system at 20°C provided by the present invention; Figure 6 A schematic diagram of the 0℃ MTF of the optical system provided by the present invention; Figure 7 This is a schematic diagram of the 65°C MTF of the fixed-focus optical system provided by the present invention.

[0016] Explanation of icon numbers: 100. Fixed-focus optical system; 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Eighth lens; 9. Aperture stop; 10. Filter; 11. Photosensitive chip.

[0017] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0020] In addition, if the embodiments of the present invention involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are for descriptive purposes only, and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, if "and / or" or "and / or" appears throughout the text, its meaning includes three parallel scenarios. Taking "A and / or B" as an example, it includes scenario A, or scenario B, or the scenario where A and B are satisfied simultaneously. In addition, the technical solutions between the embodiments can be combined with each other, but it must be based on the fact that those skilled in the art can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0021] The present invention provides a fixed-focus optical system, aiming to improve the problems of large lens distortion, small target surface, large volume, and unclear imaging in the existing ones.

[0022] Please refer to Figure 1 , in an embodiment of the present invention, The fixed-focus optical system 100 has an object side and an image side arranged corresponding to each other along the optical axis direction. The fixed-focus optical system 100 includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, and an image plane arranged in sequence from the object side to the image side, such that the distance between the vertex of the object side surface of the first lens 1 of the fixed-focus optical system 100 and the image plane is controlled within 16 mm, and the field angle can reach 110°. The fixed-focus optical system 100 satisfies the following conditions: -9 < f1 < -4; and -55 < f2 < -35; and 4 < f3 < 8; and 8 < f4 < 12; and -40 < f5 < -20; and 4 < f6 < 8; and -15 < f7 < -8; and 40 < f8 < 60. The focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, the focal length of the fourth lens 4 is f4, the focal length of the fifth lens 5 is f5, the focal length of the sixth lens 6 is f6, the focal length of the seventh lens 7 is f7, and the focal length of the eighth lens 8 is f8.

[0023] In the technical solution of this invention, the fixed-focus optical system 100 is composed of eight lenses. By setting the focal length of the first lens 1 to a negative value, the fixed-focus optical system 100 can collect light, thereby effectively increasing the field of view and correcting astigmatism and field curvature. Furthermore, by setting the focal length of the third lens 3 to a positive value, the third lens 3 can bear a larger optical power of the fixed-focus optical system 100, thereby changing the propagation direction of the light beam and making it more conducive to the beam forming on the image plane. This configuration, through the comprehensive arrangement of the focal lengths of the eight lenses, achieves a compact and lightweight design. The rational arrangement of the eight lenses improves image quality. Furthermore, by combining different lenses and rationally allocating optical power, the fixed-focus optical system 100 possesses excellent performance characteristics such as a wide viewing angle, high pixel count, and very good thermal distortion reduction. It offers a wider field of view, obtains more comprehensive data information, and can operate stably in environments with large temperature differences from 0℃ to 65℃, making it widely applicable.

[0024] Of course, the present invention does not limit the specific surface shapes of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8. It is only necessary to ensure that the surface shapes of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 correspond to their respective focal length ranges.

[0025] In one embodiment of the present invention, the first lens 1 has a negative optical power, its object-side surface is convex, and its image-side surface is concave; the second lens 2 has a negative optical power, its object-side surface is convex, and its image-side surface is concave; the third lens 3 has a positive optical power, its object-side surface is convex, and its image-side surface is flat; the fourth lens 4 has a positive optical power, its object-side surface is convex, and its image-side surface is convex; the fifth lens 5 has a negative optical power, its object-side surface is concave, and its image-side surface is convex; the sixth lens 6 has a positive optical power, its object-side surface is concave, and its image-side surface is convex; the seventh lens 7 has a negative optical power, its object-side surface is concave, and its image-side surface is convex; and the eighth lens 8 has a positive optical power, its object-side surface is convex, and its image-side surface is concave.

[0026] It is understood that the present invention does not limit the specific values ​​of the focal lengths of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8. In the present invention, the focal lengths of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 can all be selected according to the actual situation, as long as the specific values ​​of the focal lengths of each lens are within the corresponding value range.

[0027] For example, in one embodiment of the present invention, the focal length of the first lens 1 can be set to -5.309mm; the focal length of the second lens 2 can be set to -40.923mm; the focal length of the third lens 3 can be set to 4.957mm; the focal length of the fourth lens 4 can be set to 9.5527mm; the focal length of the fifth lens 5 can be set to -28.714mm; the focal length of the sixth lens 6 can be set to 4.951mm; the focal length of the seventh lens 7 can be set to -9.946mm; and the focal length of the eighth lens 8 can be set to 48.968mm. With this configuration, the focal lengths of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 are all within their respective ranges, thereby ensuring that the fixed-focus optical system 100 has good imaging quality.

[0028] It should be noted that, in this invention, to further reduce the volume and cost of the fixed-focus optical system 100, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 are all configured as aspherical lenses. Using aspherical lenses not only reduces the manufacturing cost and volume of the projection optical system 100, but also, aspherical lenses have better radius of curvature characteristics, which has the advantages of improving distortion aberration and astigmatism. By using aspherical lenses, aberrations that occur during imaging can be eliminated as much as possible, thereby improving the image quality of the lens.

[0029] To further reduce the cost of the fixed-focus optical system 100, in a further embodiment of the present invention, the first lens 1, the second lens 2, the fourth lens 4, the fifth lens 5, the seventh lens 7, and the eighth lens 8 are configured as plastic aspherical lenses. This configuration results in lower material costs for the plastic aspherical lenses, effectively reducing the overall manufacturing cost of the fixed-focus optical system 100 while maintaining image quality. Simultaneously, the plastic material possesses a certain degree of flexibility, making it less prone to damage than glass lenses when subjected to minor external impacts, thus improving the durability of the fixed-focus optical system 100.

[0030] To combat the thermal deformation of the fixed-focus optical system 100, reduce the impact of temperature on its optical performance, and maintain its high precision over a longer period, in a further embodiment of the present invention, the third lens 3 and the sixth lens 6 are configured as glass aspherical lenses. This configuration leverages the high thermal stability and low coefficient of thermal expansion of glass, resulting in minimal changes in the shape and size of the aspherical lenses during temperature variations. This effectively combats thermal deformation of the fixed-focus optical system 100, ensuring stable optical performance under different temperature conditions, reducing aberrations caused by temperature changes, and guaranteeing consistent image quality.

[0031] Furthermore, the excellent optical performance of glass aspherical lenses can better meet the high-precision imaging requirements of 100 pairs of fixed-focus optical systems, further improving the overall performance of the system.

[0032] In this invention, the refractive index of the first lens 1 is n1, 1.50≤n1≤1.60; the refractive index of the second lens 2 is n2, 1.60≤n2≤1.70; the refractive index of the third lens 3 is n3, 1.75≤n3≤1.90; the refractive index of the fourth lens 4 is n4, 1.50≤n4≤1.60; the refractive index of the fifth lens 5 is n5, 1.60≤n5≤1.70; the refractive index of the sixth lens 6 is n6, 1.40≤n6≤1.55; the refractive index of the seventh lens 7 is n7, 1.60≤n7≤1.70; and the refractive index of the eighth lens 8 is n8, 1.50≤n8≤1.60.

[0033] This invention does not limit the specific values ​​of the refractive index of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8. In actual setup, the refractive indices of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 can all be selected according to the actual situation, as long as the specific value of the refractive index of each lens is within the corresponding value range.

[0034] For example, in one embodiment of the present invention, the refractive index of the first lens 1 can be set to 1.54, the refractive index of the second lens 2 can be set to 1.66, the refractive index of the third lens 3 can be set to 1.85, the refractive index of the fourth lens 4 can be set to 1.54, the refractive index of the fifth lens 5 can be set to 1.66, the refractive index of the sixth lens 6 can be set to 1.50, the refractive index of the seventh lens 7 can be set to 1.64, and the refractive index of the eighth lens 8 can be set to 1.54.

[0035] Similarly, in this invention, the dispersion coefficient of the first lens 1 is v1, 50.0≤v1≤70.0; the dispersion coefficient of the second lens 2 is v2, 18.0≤v2≤26.0; the dispersion coefficient of the third lens 3 is v3, 35.0≤v3≤60.0; the dispersion coefficient of the fourth lens 4 is v4, 50.0≤v4≤70.0; the dispersion coefficient of the fifth lens 5 is v5, 18.0≤v5≤26.0; the dispersion coefficient of the sixth lens 6 is v6, 75.0≤v6≤100.0; the dispersion coefficient of the seventh lens 7 is v7, 18.0≤v7≤26.0; and the dispersion coefficient of the eighth lens 8 is v8, 50.0≤v8≤70.0.

[0036] Of course, the present invention does not limit the specific values ​​of the dispersion coefficients of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8. In actual settings, the dispersion coefficients of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 can all be selected according to the actual situation, as long as the specific values ​​of the dispersion coefficients of each lens are within the corresponding value range.

[0037] For example, in one embodiment of the present invention, the dispersion coefficient of the first lens 1 is set to 55.6, the dispersion coefficient of the second lens 2 is set to 20.4, the dispersion coefficient of the third lens 3 is set to 40.1, the dispersion coefficient of the fourth lens 4 is set to 55.6, the dispersion coefficient of the fifth lens 5 is set to 20.4, the dispersion coefficient of the sixth lens 6 is set to 81.6, the dispersion coefficient of the seventh lens 7 is set to 23.9, and the dispersion coefficient of the eighth lens 8 is set to 55.6.

[0038] In this embodiment, the sixth lens 6 has a high Abbe number. This configuration further corrects the aberrations of the fixed-focus optical system 100, resulting in a clearer image and more accurate color reproduction. The high Abbe number of the sixth lens 6 effectively reduces chromatic aberration, preventing color stripes from appearing at the image edges, thereby improving the overall image quality of the fixed-focus optical system 100.

[0039] Furthermore, the present invention does not limit the aperture value of the fixed-focus optical system 100. In one embodiment of the present invention, the aperture value of the fixed-focus optical system 100 is F, where 2.0 ≤ F ≤ 2.4. This setting enables the fixed-focus optical system 100 to have a large light transmission and high image brightness, enabling clear imaging even in low light conditions, and also allows the fixed-focus optical system 100 to support an image plane of 1 / 1.43 inch.

[0040] To enable adjustment of the aperture value of the fixed-focus optical system 100, in an embodiment of the present invention, the fixed-focus optical system 100 further includes an aperture stop 9, which is disposed between the third lens 3 and the fourth lens 4. Thus, the fixed-focus optical system 100 can adjust the light throughput according to actual conditions, thereby improving image quality.

[0041] In a further embodiment of the present invention, the diameter of the first lens 1 is D1, where D1 < 14 mm. Thus, in this embodiment, by limiting the diameter of the first lens 1, the aperture of the fixed-focus optical system 100 can be avoided from being too large, thereby meeting the installation space requirements of the final lens product.

[0042] In a further embodiment of the present invention, the diameter of the image plane is IC, where 9.0 mm ≤ IC ≤ 11.2 mm. This configuration allows for further control over the volume of the fixed-focus optical system 100, satisfying its installation space requirements.

[0043] Furthermore, in this embodiment, the effective focal length of the fixed-focus optical system 100 is EFL, and TTL / EFL≤4.

[0044] To further improve the imaging quality of the fixed-focus optical system 100, in one embodiment of the present invention, the fixed-focus optical system 100 further includes a filter 10, which is disposed between the eighth lens 8 and the image plane. The filter 10 can effectively filter out stray light in non-working wavelength bands to reduce optical noise and further improve imaging quality.

[0045] In addition, the fixed-focus optical system 100 also includes a photosensitive chip 11, which is disposed on the image side of the eighth lens 8, and the end face of the photosensitive chip 11 facing the object side forms the image plane.

[0046] In a specific embodiment of the present invention, the fixed-focus optical system 100 has a focal length f=3.96mm, an aperture value F=2.4, an image plane diameter IC=11.2mm, and a diagonal field of view of 110°.

[0047] In this embodiment, the surface type, radius of curvature, thickness, material refractive index, Abbe number, and semi-diameter of the multiple lenses are shown in Table 1 below: Table 1

[0048] Furthermore, in this embodiment, since the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 are all aspherical lenses, the aspherical surface shape of the aspherical lens satisfies the following condition:

[0049] Where z represents the axial sagitta in the Z direction of the aspherical surface; y represents the height of the aspherical surface; c represents the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k represents the conic coefficient; and the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms represent higher-order aspherical coefficients, respectively.

[0050] One design value for the aspheric coefficient in this embodiment is shown in Table 2 below: Table 2

[0051] It should be noted that Table 2 is a design value of the aspherical coefficient of the lens in the fixed-focus optical system 100 described in this embodiment. The specific value of the aspherical coefficient design can be adjusted according to the needs of the product, and the present invention does not limit it.

[0052] Please see Figure 2 , Figure 2 This is a schematic diagram of the spherical aberration curve of the fixed-focus optical system 100 in this embodiment.

[0053] Please see Figure 3 , Figure 3 This is a schematic diagram of the light aberration curve of the fixed-focus optical system 100 in this embodiment.

[0054] Please see Figure 4 , Figure 4 This is a schematic diagram of the field curvature distortion of the fixed-focus optical system 100 in this embodiment.

[0055] Please see Figure 5 , Figure 5 This is a schematic diagram of the 20°C MTF of the fixed-focus optical system 100 in this embodiment.

[0056] Please see Figure 6 , Figure 6 This is a schematic diagram of the 0°C MTF of the fixed-focus optical system 100 in this embodiment.

[0057] Please see Figure 7 , Figure 7 This is a schematic diagram of the 65°C MTF of the fixed-focus optical system 100 in this embodiment.

[0058] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A fixed-focus optical system, characterized in that, The fixed-focus optical system has an object side and an image side arranged corresponding to each other along the optical axis direction. The fixed-focus optical system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and an image plane arranged in sequence from the object side to the image side, such that the distance between the vertex of the object side surface of the first lens of the fixed-focus optical system and the image plane is controlled within 16 mm, and the field angle can reach 110°. The fixed-focus optical system satisfies the following conditions: -9 < f1 < -4; and -55 < f2 < -35; and 4 < f3 < 8; and 8 < f4 < 12; and -40 < f5 < -20; and 4 < f6 < 8; and -15 < f7 < -8; and 40 < f8 < 60; Wherein, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the eighth lens is f8.

2. The fixed-focus optical system as described in claim 1, characterized in that, The first lens has a negative optical power. The object side surface of the first lens is convex, and the image side surface is concave. The second lens has a negative optical power. The object side surface of the second lens is convex, and the image side surface is concave. The third lens has a positive optical power. The object side surface of the third lens is convex, and the image side surface is flat. The fourth lens has a positive optical power. The object side surface of the fourth lens is convex, and the image side surface is convex. The fifth lens has a negative optical power. The object side surface of the fifth lens is concave, and the image side surface is convex. The sixth lens has a positive optical power. The object side surface of the sixth lens is concave, and the image side surface is convex. The seventh lens has a negative optical power. The object side surface of the seventh lens is concave, and the image side surface is convex. The eighth lens has a positive optical power. The object side surface of the eighth lens is convex, and the image side surface is concave.

3. The fixed-focus optical system as described in claim 1, characterized in that, The first lens, the second lens, the fourth lens, the fifth lens, the seventh lens, and the eighth lens are arranged as plastic aspherical lenses. The third lens and the sixth lens are arranged as glass aspherical lenses.

4. The fixed-focus optical system as described in claim 1, characterized in that, The refractive index of the first lens is n1, 1.50 ≤ n1 ≤ 1.60; The refractive index of the second lens is n2, 1.60 ≤ n2 ≤ 1.70; The refractive index of the third lens is n3, 1.75 ≤ n3 ≤ 1.90; The refractive index of the fourth lens is n4, 1.50 ≤ n4 ≤ 1.60; The refractive index of the fifth lens is n5, 1.60 ≤ n5 ≤ 1.70; The refractive index of the sixth lens is n6, 1.40 ≤ n6 ≤ 1.55; The refractive index of the seventh lens is n7, 1.60 ≤ n7 ≤ 1.70; The refractive index of the eighth lens is n8, 1.50 ≤ n8 ≤ 1.

60.

5. The fixed-focus optical system as described in claim 1, characterized in that, The dispersion coefficient of the first lens is v1, 50.0 ≤ v1 ≤ 70.0; The dispersion coefficient of the second lens is v2, 18.0 ≤ v2 ≤ 26.0; The dispersion coefficient of the third lens is v3, 35.0 ≤ v3 ≤ 60.0; The dispersion coefficient of the fourth lens is v4, 50.0≤v4≤70.0; The dispersion coefficient of the fifth lens is v5, 18.0≤v5≤26.0; The dispersion coefficient of the sixth lens is v6, 75.0≤v6≤100.0; The dispersion coefficient of the seventh lens is v7, 18.0≤v7≤26.0; The dispersion coefficient of the eighth lens is v8, where 50.0 ≤ v8 ≤ 70.

0.

6. The fixed-focus optical system as described in claim 1, characterized in that, The aperture value of the fixed-focus optical system is F, where 2.0 ≤ F ≤ 2.

4.

7. The fixed-focus optical system as described in claim 1, characterized in that, The diameter of the first lens is D1, where D1 < 14 mm.

8. The fixed-focus optical system as described in claim 1, characterized in that, The diameter of the image plane is IC, where 9.0 mm ≤ IC ≤ 11.2 mm.

9. The fixed-focus optical system as described in claim 1, characterized in that, The effective focal length of the fixed-focus optical system is EFL, and TTL / EFL≤4.

10. The fixed-focus optical system as described in claim 1, characterized in that, The fixed-focus optical system further includes an aperture stop, which is disposed between the third lens and the fourth lens; and / or, The fixed-focus optical system further includes a filter disposed between the eighth lens and the image plane; and / or, The fixed-focus optical system also includes a photosensitive chip, which is disposed on the image-side of the eighth lens, and the end face of the photosensitive chip facing the object side forms the image plane.

Images