Fixed focus optical system

Abstract

This invention discloses a fixed-focus optical system, relating to the field of fixed-focus optical technology. The fixed-focus optical system has an object side and an image side arranged opposite each other along the optical axis. The system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and an image plane arranged sequentially from the object side towards the image side. The first and third lenses are glass spherical lenses, while the second, fourth, fifth, and sixth lenses are plastic aspherical lenses. This arrangement, through the rational arrangement of the six lenses, improves the imaging quality of the fixed-focus optical system. Furthermore, the combination of different lenses ensures that the fixed-focus optical system exhibits low distortion and good temperature adaptability, guaranteeing stable operation over a wide temperature range.

Description

Technical Field

[0001] This invention relates to the field of fixed-focus optics technology, and in particular to a fixed-focus optical system. Background Technology

[0002] With the rapid development of intelligent driving assistance systems, electronic rearview mirrors are gradually replacing traditional rearview mirrors to achieve the function of monitoring the rear and side views.

[0003] However, due to limitations in current technology, mainstream automotive side-view lenses on the market cannot simultaneously meet the requirements of miniaturization, high resolution, and a wide field of view. They also suffer from poor image quality when used under high and low temperature conditions. Summary of the Invention

[0004] The main objective of this invention is to propose a fixed-focus optical system that aims to improve the existing vehicle-mounted test lenses, which cannot simultaneously meet the requirements of miniaturization, high resolution, and a wide field of view, while also suffering from poor image quality when used under high and low temperature conditions.

[0005] To achieve the above objectives, the fixed-focus optical system proposed in this invention has an object side and an image side arranged opposite to each other along the optical axis. The fixed-focus optical system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and an image plane arranged sequentially from the object side toward the image side. The first lens and the third lens are glass spherical lenses, while the second lens, the fourth lens, the fifth lens, and the sixth lens are plastic aspherical lenses. The fixed-focus optical system satisfies the following conditions: -4.5≤f1 / f≤-0.3, and 4≤f2 / f≤11, and 0≤f3 / f≤5.0, and -4.0≤f4 / f≤0.0, and 0.0≤f5 / f≤4.0, and -7.5≤f6 / f≤-2.0 or 2.8≤f6 / f≤19.8; Wherein, the focal length of the fixed-focus optical system is f, 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, and the focal length of the sixth lens is f6.

[0006] In one embodiment, the first lens is configured as a negative lens, with its object-side surface being convex and its image-side surface being concave. The second lens is configured as a positive lens, with its object-side surface being concave and its image-side surface being convex. The third lens is configured as a positive lens, with its object side and image side being convex. The fourth lens is configured as a negative lens, with its object side being convex and its image side being concave. The fifth lens is configured as a positive lens, with its object side and image side being convex. The sixth lens is configured as a negative lens, with its object side being convex and its image side being concave.

[0007] In one embodiment, the first lens is configured as a negative lens, with its object-side surface being convex and its image-side surface being concave. The second lens is configured as a positive lens, with its object-side surface being concave and its image-side surface being convex. The third lens is configured as a positive lens, with its object side and image side being convex. The fourth lens is configured as a negative lens, with its object side and image side being concave. The fifth lens is configured as a positive lens, with its object side and image side being convex. The sixth lens is configured as a negative lens, with its object side being convex and its image side being concave. The fourth lens and the fifth lens are bonded together.

[0008] In one embodiment, the first lens is configured as a negative lens, with its object-side surface being convex and its image-side surface being concave. The second lens is configured as a positive lens, with its object-side surface being concave and its image-side surface being convex. The third lens is configured as a positive lens, with its object side and image side being convex. The fourth lens is configured as a negative lens, with its object side being convex and its image side being concave. The fifth lens is configured as a positive lens, with its object side and image side being convex. The sixth lens is configured as a positive lens, with its object side being convex and its image side being concave. The fourth lens and the fifth lens are bonded together.

[0009] In one embodiment, the fourth lens and the fifth lens form a cemented lens assembly.

[0010] In one embodiment, the refractive index of the first lens is Nd1, and the Abbe constant is Vd1, where 1.40≤Nd1≤1.95 and 35≤Vd1≤78. The refractive index of the second lens is Nd2, and the Abbe constant is Vd2, where 1.50≤Nd2≤1.80 and 10≤Vd2≤40. The refractive index of the third lens is Nd3, and the Abbe constant is Vd3, where 1.6≤Nd3≤2.00 and 30≤Vd3≤60. The refractive index of the fourth lens is Nd4, and the Abbe constant is Vd4, where 1.45≤Nd4≤1.80 and 10≤Vd4≤40. The refractive index of the fifth lens is Nd5, and the Abbe constant is Vd5, where 1.4≤Nd5≤1.70 and 40≤Vd5≤75. The refractive index of the sixth lens is Nd6, and the Abbe constant is Vd6, where 1.35≤Nd6≤1.80 and 35≤Vd6≤80.

[0011] In one embodiment, the distance between the center of the image-side surface of the sixth lens and the image plane is BFL, and the distance between the center of the object-side surface of the first lens and the image plane is TTL, where BFL / TTL > 0.1.

[0012] In one embodiment, the maximum field of view of the fixed-focus optical system is FOV, and the image height corresponding to the maximum field of view of the fixed-focus optical system is h, where 50≤(FOV×f) / h≤70.

[0013] In one embodiment, the fixed-focus optical system further includes an aperture stop disposed between the second lens and the third lens, the aperture stop being used to adjust the aperture number of the fixed-focus optical system.

[0014] In one embodiment, the aperture number of the fixed-focus optical system is FNO, where FNO = 1.8.

[0015] In the technical solution of this invention, the fixed-focus optical system is composed of six lenses. Through the cooperation of the six lenses, the light beam is converged and corrected, thereby forming a clear image on the image plane. Furthermore, by limiting the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens to -4.5≤f1 / f≤-0.3, and 4≤f2 / f≤11, and 0≤f3 / f≤5.0, and -4.0≤f4 / f≤0.0, and 0.0≤f5 / f≤4.0, and -7.5≤f6 / f≤-2.0 or 2.8≤f6 / f≤19.8, the imaging quality of the fixed-focus optical system is improved through the reasonable arrangement of the six lenses. Moreover, through the combination of different lenses, the fixed-focus optical system has low distortion and good temperature adaptability, ensuring that the fixed-focus optical system can maintain stable operation over a wide temperature range. Attached Figure Description

[0016] 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.

[0017] Figure 1This is a schematic diagram of the structure of the first embodiment of the fixed-focus optical system provided by the present invention; Figure 2 for Figure 1 A schematic diagram of the dot array of a fixed-focus optical system; Figure 3 for Figure 1 Schematic diagram of light aberrations in a fixed-focus optical system; Figure 4 This is a schematic diagram of the structure of a second embodiment of the fixed-focus optical system provided by the present invention; Figure 5 for Figure 4 A schematic diagram of the dot array of a fixed-focus optical system; Figure 6 for Figure 4 Schematic diagram of light aberrations in a fixed-focus optical system; Figure 7 This is a schematic diagram of the structure of the third embodiment of the fixed-focus optical system provided by the present invention; Figure 8 for Figure 7 A schematic diagram of the dot array of a fixed-focus optical system; Figure 9 for Figure 7 A schematic diagram of light aberrations in a fixed-focus optical system.

[0018] 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. Aperture stop; 8. Image plane.

[0019] 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

[0020] 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.

[0021] 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.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] This invention proposes a fixed-focus optical system, which aims to improve the existing vehicle-mounted test lenses that cannot simultaneously meet the requirements of miniaturization, high resolution, and wide field of view, while also having poor image quality when used under high and low temperature conditions.

[0024] Please see Figure 1 , Figure 4 and Figure 7 In one embodiment of the present invention, the fixed-focus optical system 100 has an object side and an image side arranged opposite to each other along the optical axis. 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, and an image plane 8 arranged sequentially from the object side toward the image side. The first lens 1 and the third lens 3 are glass spherical lenses, and the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are plastic aspherical lenses. The fixed-focus optical system 100 satisfies the following condition: -4. 5≤f1 / f≤-0.3, and 4≤f2 / f≤11, and 0≤f3 / f≤5.0, and -4.0≤f4 / f≤0.0, and 0.0≤f5 / f≤4.0, and -7.5≤f6 / f≤-2.0 or 2.8≤f6 / f≤19.8, wherein the focal length of the fixed-focus optical system 100 is f, 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, and the focal length of the sixth lens 6 is f6.

[0025] In the technical solution of this invention, the fixed-focus optical system 100 is composed of six lenses. Through the cooperation of the six lenses, the light beam is converged and corrected, thereby forming a clear image on the image plane 8. Furthermore, by limiting the focal lengths 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 to -4.5≤f1 / f≤-0.3, and 4≤f2 / f≤11, and 0≤f3 / f≤5.0, and -4.0≤f4 / f≤0.0, and 0.0≤f5 / f≤4.0, and -7.5≤f6 / f≤-2.0 or 2.8≤f6 / f≤19.8, the imaging quality of the fixed-focus optical system 100 is improved through the reasonable arrangement of the six lenses. And through the combination of different lenses, the fixed-focus optical system 100 has small distortion and good temperature adaptability, ensuring that the fixed-focus optical system 100 can maintain stable operation over a wide temperature range.

[0026] 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, and the sixth lens 6. In the present invention, 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, and the sixth lens 6 correspond to their respective focal length ranges.

[0027] For example, in one embodiment of the present invention, the first lens 1 is configured as a negative lens with a convex object-side surface and a concave image-side surface; the second lens 2 is configured as a positive lens with a concave object-side surface and a convex image-side surface; the third lens 3 is configured as a positive lens with a convex object-side surface and a convex image-side surface; the fourth lens 4 is configured as a negative lens with a convex object-side surface and a concave image-side surface; the fifth lens 5 is configured as a positive lens with a convex object-side surface and a convex image-side surface; and the sixth lens 6 is configured as a negative lens with a convex object-side surface and a concave image-side surface. With this configuration, through the specific combination of the lens surface types, various aberrations such as chromatic aberration, astigmatism, and field curvature of the fixed-focus optical system 100 can be effectively corrected, further improving the sharpness and uniformity of the image.

[0028] Moreover, due to its excellent temperature adaptability, it can maintain good imaging performance in both high and low temperature environments, reducing the impact of environmental temperature changes on image quality and greatly expanding its application scenarios and scope.

[0029] Of course, the positive and negative settings and specific surface shapes 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 can also be set in other forms. In another embodiment of the present invention, the first lens 1 is set as a negative lens with a convex object side and a concave image side; the second lens 2 is set as a positive lens with a concave object side and a convex image side; the third lens 3 is set as a positive lens with a convex object side and a convex image side; the fourth lens 4 is set as a negative lens with a concave object side and a concave image side; the fifth lens 5 is set as a positive lens with a convex object side and a convex image side; and the sixth lens 6 is set as a negative lens with a convex object side and a concave image side. The fourth lens 4 and the fifth lens 5 are cemented together. In this embodiment, the specific combination of lens surfaces effectively corrects various aberrations such as chromatic aberration, astigmatism, and field curvature in the fixed-focus optical system 100, further improving image sharpness and uniformity. Furthermore, by cementing the fourth lens 4 and the fifth lens 5 together, the air gap between the two lenses is effectively reduced, lowering the system's assembly precision requirements and better correcting chromatic aberration, thus improving image quality. This cemented connection also simplifies the structural complexity of the fixed-focus optical system 100, making it more compact and reducing its size and weight, facilitating integration and application in various devices.

[0030] It is understood that in this embodiment, the sixth lens 6 is set as a negative lens, therefore, the focal length f6 of the sixth lens 6 should be set to -7.5≤f6 / f≤-2.0.

[0031] Similarly, in this embodiment, since the fourth lens 4 and the fifth lens 5 are cemented together, they form a cemented lens group. Thus, by reasonably limiting the focal length of the cemented lens group, the imaging performance of the fixed-focus optical system 100 can be further optimized, ensuring clear and accurate images at different object distances. At the same time, this arrangement also helps to reduce aberrations in the fixed-focus optical system 100, improving image uniformity and contrast.

[0032] In another embodiment of the present invention, the first lens 1 is configured as a negative lens with a convex object-side surface and a concave image-side surface; the second lens 2 is configured as a positive lens with a concave object-side surface and a convex image-side surface; the third lens 3 is configured as a positive lens with a convex object-side surface and a convex image-side surface; the fourth lens 4 is configured as a negative lens with a convex object-side surface and a concave image-side surface; the fifth lens 5 is configured as a positive lens with a convex object-side surface and a convex image-side surface; and the sixth lens 6 is configured as a positive lens with a convex object-side surface and a concave image-side surface. The fourth lens 4 and the fifth lens 5 are cemented together. It is understood that in this embodiment, by configuring the sixth lens 6 as a negative lens and cementing the fourth lens 4 and the fifth lens 5 together, this lens combination and surface design can effectively correct various aberrations of the fixed-focus optical system 100, including chromatic aberration, astigmatism, and field curvature, thereby significantly improving the sharpness and uniformity of the image. Specifically, setting the sixth lens 6 as a positive lens and employing specific convex-concave surface shapes on its object-side and image-side surfaces helps to further optimize the imaging performance of the system. Meanwhile, the cemented connection between the fourth lens 4 and the fifth lens 5 not only reduces the air gap between the lenses and lowers the assembly precision requirements, but also better corrects chromatic aberration, improves overall image quality, and makes the fixed-focus optical system 100 more compact, effectively controlling its size and weight.

[0033] It is also understood that in this embodiment, the sixth lens 6 is set as a positive lens, therefore, the focal length f6 of the sixth lens 6 should be set to 2.8≤f6 / f≤19.8.

[0034] Of course, in this embodiment, since the fourth lens 4 and the fifth lens 5 are cemented together, they form a cemented lens group. Thus, by reasonably limiting the focal length of the cemented lens group, the imaging performance of the fixed-focus optical system 100 can be further optimized, ensuring clear and accurate images at different object distances. At the same time, this arrangement also helps to reduce aberrations in the fixed-focus optical system 100, improving image uniformity and contrast.

[0035] It should be noted that the present invention does not limit the specific materials and types of the multiple lenses. In the embodiments of the present invention, the first lens 1 and the third lens 3 are set as glass spherical lenses. With this setting, the glass material has high thermal stability and low coefficient of thermal expansion. When the temperature changes, the shape and size of the glass lens change very little, which can effectively resist the problem of thermal deformation of the fixed-focus optical system 100. This allows the fixed-focus optical system 100 to maintain stable optical performance under different temperature environments, reduce aberrations caused by temperature changes, and ensure consistent image quality. The spherical lens has a relatively simple curved shape, is easy to process and manufacture, and can reduce production costs. Furthermore, the optical performance of the glass spherical lens is stable, and it can maintain good imaging effect under various lighting conditions.

[0036] In another embodiment of the present invention, the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 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. Furthermore, the plastic material possesses a certain degree of flexibility, making it less susceptible to damage from minor external impacts compared to glass lenses, thus improving the durability of the fixed-focus optical system 100. Additionally, the lightweight nature of the plastic material significantly reduces the overall weight of the fixed-focus optical system 100, facilitating its application in various devices with stringent weight requirements. Moreover, aspherical lenses offer superior curvature radius characteristics, improving distortion and astigmatism. Using aspherical lenses can minimize aberrations occurring during imaging, thereby enhancing the lens's image quality and further improving the overall performance of the fixed-focus optical system 100.

[0037] Furthermore, this invention does not limit the specific values ​​of the refractive indices 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. In this invention, the refractive index of the first lens 1 is Nd1, 1.40≤Nd1≤1.95; the refractive index of the second lens 2 is Nd2, 1.50≤Nd2≤1.80; the refractive index of the third lens 3 is Nd3, 1.6≤Nd3≤2.00; the refractive index of the fourth lens 4 is Nd4, 1.45≤Nd4≤1.80; the refractive index of the fifth lens 5 is Nd5, 1.4≤Nd5≤1.70; and the refractive index of the sixth lens 6 is Nd6, 1.35≤Nd6≤1.80. The specific values ​​of the refractive indices 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 can be selected according to actual conditions, as long as the specific values ​​of the refractive indices of each lens are within the corresponding range.

[0038] Similarly, in this invention, the Abbe constant is Vd1, 35≤Vd1≤78, the Abbe constant is Vd2, 10≤Vd2≤40, the Abbe constant is Vd3, 30≤Vd3≤60, the Abbe constant is Vd4, 10≤Vd4≤40, the Abbe constant is Vd5, 40≤Vd5≤75, and the Abbe constant is Vd6, 35≤Vd6≤80.

[0039] 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, and the sixth lens 6. 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, and the sixth lens 6 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.

[0040] It should also be noted that, in one embodiment of the present invention, the distance between the center of the image-side surface of the sixth lens 6 and the image plane 8 is BFL, and the distance between the center of the object-side surface of the first lens 1 and the image plane 8 is TTL, where BFL / TTL > 0.1. This configuration, by reasonably controlling the ratio of the back focal length BFL to the total system length TTL, effectively balances the compactness and imaging stability of the fixed-focus optical system 100, thereby ensuring that the fixed-focus optical system 100, while maintaining a small size, still provides sufficient back working distance, facilitating integration with image sensors or other optical components.

[0041] Furthermore, in a further embodiment of the present invention, the maximum field of view of the fixed-focus optical system 100 is FOV, and the image height corresponding to the maximum field of view of the fixed-focus optical system 100 is h, where 50 ≤ (FOV × f) / h ≤ 70. This setting, by reasonably limiting the ratio between the maximum field of view and the focal length and image height, ensures that the fixed-focus optical system 100 can acquire a large field of view while effectively controlling aberrations and guaranteeing the imaging quality of the edge fields of view. This results in a high degree of clarity and uniformity in the overall image, enabling the fixed-focus optical system 100 to meet the requirements for monitoring or shooting large scenes without significantly degrading the imaging quality due to an excessively large field of view. This provides reliable imaging assurance for the application of the fixed-focus optical system 100 in various fields.

[0042] Furthermore, in this invention, in order to adjust the aperture number of the fixed-focus optical system 100 so that the fixed-focus optical system 100 can be adapted to a variety of different shooting environments, in one embodiment of this invention, the fixed-focus optical system 100 further includes an aperture stop 7, which is disposed between the second lens 2 and the third lens 3, and the aperture stop 7 is used to adjust the aperture number of the fixed-focus optical system 100.

[0043] Of course, the present invention does not limit the specific value of the aperture number of the fixed-focus optical system 100. In actual settings, the light transmission of the aperture 7 can be adjusted according to the needs.

[0044] In one specific embodiment of the present invention, the aperture number of the fixed-focus optical system 100 is FNO, where FNO = 1.8.

[0045] Specifically, please refer to Figure 1 In the first embodiment of the present invention, the first lens 1 is configured as a negative lens with a convex object side and a concave image side; the second lens 2 is configured as a positive lens with a concave object side and a convex image side; the third lens 3 is configured as a positive lens with a convex object side and a convex image side; the fourth lens 4 is configured as a negative lens with a convex object side and a concave image side; the fifth lens 5 is configured as a positive lens with a convex object side and a convex image side; the sixth lens 6 is configured as a negative lens with a convex object side and a concave image side; and the aperture number FNO of the fixed-focus optical system 100 is 1.8.

[0046] In this embodiment, the surface type, radius of curvature (mm), thickness (mm), and material properties of the multiple lenses are shown in Table 1 below: Table 1

[0047] Furthermore, in this embodiment, since the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all aspherical lenses, the aspherical surface shape of the aspherical lens satisfies the following condition: +

[0048] Wherein, parameter c is the curvature corresponding to the radius, y is the radial coordinate, and its unit is the same as the lens length unit, k is the conic quadratic coefficient; when the coefficient k is less than -1, the surface curve of the lens is a hyperbola, when the coefficient k is equal to -1, the surface curve of the lens is a parabola; when the coefficient k is between -1 and 0, the surface curve of the lens is an ellipse, when the coefficient k is equal to 0, the surface curve of the lens is a circle, and when the coefficient k is greater than 0, the surface curve of the lens is an oval; α1 to α8 represent the coefficients corresponding to each radial coordinate.

[0049] One design value for the aspheric coefficient in this embodiment is shown in Table 2 below: Table 2

[0050] 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.

[0051] Please see Figure 2 , Figure 2 This is a point array diagram of the fixed-focus optical system 100 described in this embodiment.

[0052] Please see Figure 3 , Figure 3 This is a schematic diagram of the light aberrations of the fixed-focus optical system 100 described in this embodiment.

[0053] Please see Figure 4 In the second embodiment of the present invention, the first lens 1 is configured as a negative lens with a convex object side and a concave image side; the second lens 2 is configured as a positive lens with a concave object side and a convex image side; the third lens 3 is configured as a positive lens with a convex object side and a convex image side; the fourth lens 4 is configured as a negative lens with a concave object side and a concave image side; the fifth lens 5 is configured as a positive lens with a convex object side and a convex image side; and the sixth lens 6 is configured as a negative lens with a convex object side and a concave image side. The fourth lens 4 and the fifth lens 5 are cemented together, and the aperture number FNO of the fixed-focus optical system 100 is 1.8.

[0054] In this embodiment, the surface type, radius of curvature (mm), thickness (mm), and material properties of the multiple lenses are shown in Table 3 below: Table 3

[0055] Similarly, in this embodiment, since the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all aspherical lenses, the aspherical surface shape of the aspherical lens satisfies the following condition: +

[0056] Wherein, parameter c is the curvature corresponding to the radius, y is the radial coordinate, and its unit is the same as the lens length unit, k is the conic quadratic coefficient; when the coefficient k is less than -1, the surface curve of the lens is a hyperbola, when the coefficient k is equal to -1, the surface curve of the lens is a parabola; when the coefficient k is between -1 and 0, the surface curve of the lens is an ellipse, when the coefficient k is equal to 0, the surface curve of the lens is a circle, and when the coefficient k is greater than 0, the surface curve of the lens is an oval; α1 to α8 represent the coefficients corresponding to each radial coordinate.

[0057] One design value for the aspheric coefficient in this embodiment is shown in Table 4 below: Table 4

[0058] It should be noted that Table 4 shows one design value for 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 product requirements, and this invention does not limit it.

[0059] Please see Figure 5 , Figure 5 This is a point array diagram of the fixed-focus optical system 100 described in this embodiment.

[0060] Please see Figure 6 , Figure 6 This is a schematic diagram of the light aberrations of the fixed-focus optical system 100 described in this embodiment.

[0061] Please see Figure 7 In the third embodiment of the present invention, the first lens 1 is configured as a negative lens with a convex object side and a concave image side; the second lens 2 is configured as a positive lens with a concave object side and a convex image side; the third lens 3 is configured as a positive lens with a convex object side and a convex image side; the fourth lens 4 is configured as a negative lens with a convex object side and a concave image side; the fifth lens 5 is configured as a positive lens with a convex object side and a convex image side; and the sixth lens 6 is configured as a positive lens with a convex object side and a concave image side. The fourth lens 4 and the fifth lens 5 are cemented together, and the aperture number FNO of the fixed-focus optical system 100 is 1.8.

[0062] In this embodiment, the surface type, radius of curvature (mm), thickness (mm), and material properties of the multiple lenses are shown in Table 5 below: Table 5

[0063] Similarly, in this embodiment, since the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all aspherical lenses, the aspherical surface shape of the aspherical lens satisfies the following condition: +

[0064] Wherein, parameter c is the curvature corresponding to the radius, y is the radial coordinate, and its unit is the same as the lens length unit, k is the conic quadratic coefficient; when the coefficient k is less than -1, the surface curve of the lens is a hyperbola, when the coefficient k is equal to -1, the surface curve of the lens is a parabola; when the coefficient k is between -1 and 0, the surface curve of the lens is an ellipse, when the coefficient k is equal to 0, the surface curve of the lens is a circle, and when the coefficient k is greater than 0, the surface curve of the lens is an oval; α1 to α8 represent the coefficients corresponding to each radial coordinate.

[0065] One design value for the aspheric coefficient in this embodiment is shown in Table 6 below: Table 6

[0066] It should also be noted that Table 6 shows one design value for 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 this invention does not limit it.

[0067] Please see Figure 8 , Figure 8 This is a point array diagram of the fixed-focus optical system 100 described in this embodiment.

[0068] Please see Figure 9 , Figure 9 This is a schematic diagram of the light aberrations of the fixed-focus optical system 100 described in this embodiment.

[0069] 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 opposite each other along the optical axis. It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and an image plane arranged sequentially from the object side toward the image side. The first lens and the third lens are glass spherical lenses, and the second lens, the fourth lens, the fifth lens, and the sixth lens are plastic aspherical lenses. The fixed-focus optical system satisfies the following conditions: -4.5≤f1 / f≤-0.3, and 4≤f2 / f≤11, and 0≤f3 / f≤5.0, and -4.0≤f4 / f≤0.0, and 0.0≤f5 / f≤4.0, and -7.5≤f6 / f≤-2.0 or 2.8≤f6 / f≤19.8; Wherein, the focal length of the fixed-focus optical system is f, 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, and the focal length of the sixth lens is f6.

2. The fixed-focus optical system as described in claim 1, characterized in that, The first lens is configured as a negative lens, with its object side being convex and its image side being concave. The second lens is configured as a positive lens, with its object-side surface being concave and its image-side surface being convex. The third lens is configured as a positive lens, with its object side and image side being convex. The fourth lens is configured as a negative lens, with its object side being convex and its image side being concave. The fifth lens is configured as a positive lens, with its object side and image side being convex. The sixth lens is configured as a negative lens, with its object side being convex and its image side being concave.

3. The fixed-focus optical system as described in claim 1, characterized in that, The first lens is configured as a negative lens, with its object side being convex and its image side being concave. The second lens is configured as a positive lens, with its object-side surface being concave and its image-side surface being convex. The third lens is configured as a positive lens, with its object side and image side being convex. The fourth lens is configured as a negative lens, with its object side and image side being concave. The fifth lens is configured as a positive lens, with its object side and image side being convex. The sixth lens is configured as a negative lens, with its object side being convex and its image side being concave. The fourth lens and the fifth lens are bonded together.

4. The fixed-focus optical system as described in claim 1, characterized in that, The first lens is configured as a negative lens, with its object side being convex and its image side being concave. The second lens is configured as a positive lens, with its object-side surface being concave and its image-side surface being convex. The third lens is configured as a positive lens, with its object side and image side being convex. The fourth lens is configured as a negative lens, with its object side being convex and its image side being concave. The fifth lens is configured as a positive lens, with its object side and image side being convex. The sixth lens is configured as a positive lens, with its object side being convex and its image side being concave. The fourth lens and the fifth lens are bonded together.

5. The fixed-focus optical system as described in any one of claims 3 or 4, characterized in that, The fourth lens and the fifth lens form a cemented lens group.

6. The fixed-focus optical system as described in claim 1, characterized in that, The refractive index of the first lens is Nd1, and the Abbe constant is Vd1, where 1.40≤Nd1≤1.95 and 35≤Vd1≤78. The refractive index of the second lens is Nd2, and the Abbe constant is Vd2, where 1.50≤Nd2≤1.80 and 10≤Vd2≤40. The refractive index of the third lens is Nd3, and the Abbe constant is Vd3, where 1.6≤Nd3≤2.00 and 30≤Vd3≤60. The refractive index of the fourth lens is Nd4, and the Abbe constant is Vd4, where 1.45≤Nd4≤1.80 and 10≤Vd4≤40. The refractive index of the fifth lens is Nd5, and the Abbe constant is Vd5, where 1.4≤Nd5≤1.70 and 40≤Vd5≤75. The refractive index of the sixth lens is Nd6, and the Abbe constant is Vd6, where 1.35≤Nd6≤1.80 and 35≤Vd6≤80.

7. The fixed-focus optical system as described in claim 1, characterized in that, The distance between the center of the image side surface of the sixth lens and the image plane is BFL, and the distance between the center of the object side surface of the first lens and the image plane is TTL, where BFL / TTL > 0.

1.

8. The fixed-focus optical system as described in claim 1, characterized in that, The maximum field of view of the fixed-focus optical system is FOV, and the image height corresponding to the maximum field of view of the fixed-focus optical system is h, where 50≤(FOV×f) / h≤70.

9. The fixed-focus optical system as described in claim 1, characterized in that, The fixed-focus optical system also includes an aperture stop, which is disposed between the second lens and the third lens, and is used to adjust the aperture number of the fixed-focus optical system.

10. The fixed-focus optical system as described in claim 9, characterized in that, The aperture number of the fixed-focus optical system is FNO, where FNO = 1.8.

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