A fixed focus optical system
By designing a fixed-focus optical system with a combination of six lenses, the problem of focus shift when the lens switches between different spectra was solved, resulting in a fixed-focus lens with high resolution and low distortion, suitable for 24-hour high-definition monitoring.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- JIANGXI GAORUI OPTOELECTRONICS CO LTD
- Filing Date
- 2025-08-12
- Publication Date
- 2026-07-21
Smart Images
Figure CN224536264U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of optical system technology, and in particular to a fixed-focus optical system. Background Technology
[0002] As prime lenses become increasingly prevalent in high-definition day and night imaging, traditional prime lenses with day and night confocal characteristics are facing challenges. When switching between visible light and infrared light (usually 850nm or 940nm), chromatic aberration causes focus shift, requiring refocusing. This makes them unsuitable for continuous 24-hour high-definition monitoring, resulting in low resolution. Furthermore, their optical systems typically contain 8-9 lenses, which is excessive.
[0003] Therefore, how to design and implement a high-resolution fixed-focus optical system with fewer lenses has become a technical problem that needs to be solved. Utility Model Content
[0004] The purpose of this invention is to overcome the defects of the existing technology and provide a fixed-focus optical system.
[0005] The objective of this utility model can be achieved through the following technical solutions:
[0006] A fixed-focus optical system includes a first biconvex lens, a second biconvex lens, a third biconcave lens, a fourth concave-convex lens, a fifth convex-concave lens, and a sixth convex-concave lens arranged sequentially from the object side to the image side; the second biconvex lens and the third biconcave lens are cemented together to form a cemented lens group; and an aperture is provided between the first biconvex lens and the second biconvex lens.
[0007] Furthermore, the first biconvex lens is a lens with a refractive index of 1.35≤n1≤1.80; the second biconvex lens is a lens with a refractive index of 1.30≤n2≤1.70; the third biconcave lens is a lens with a refractive index of 1.45≤n3≤1.85; the fourth concave-convex lens is a lens with a refractive index of 1.5≤n4≤2.00; the fifth convex-concave lens is a lens with a refractive index of 1.50≤n5≤1.90; and the sixth convex-concave lens is a lens with a refractive index of 11.45≤n6≤1.95.
[0008] Furthermore, the first biconvex lens is a lens with a focal length of 45mm ≤ f1 ≤ 50mm; the second biconvex lens is a lens with a focal length of 98mm ≤ f2 ≤ 103mm; the third biconcave lens is a lens with a focal length of -116mm ≤ f3 ≤ -111mm; the fourth concave-convex lens is a lens with a focal length of -31mm ≤ f4 ≤ -26mm; the fifth convex-concave lens is a lens with a focal length of 30mm ≤ f5 ≤ 35mm; and the sixth convex-concave lens is a lens with a focal length of 74mm ≤ f6 ≤ 79mm.
[0009] Furthermore, the optical system satisfies the following conditions: 0.8≤f1 / Fw≤1.5, 1.6≤f2 / Fw≤2.2, -0.7≤f3 / Fw≤-1.4, 2.5≤f4 / Fw≤3.0, -0.3≤f5 / Fw≤-0.9, 0.8≤f6 / Fw≤1.5, where Fw is the focal length of the optical system.
[0010] Furthermore, the optical system is an optical system with a focal length of 50mm, an image size of 8.9mm, and a total optical length of 59.5mm.
[0011] Compared with the prior art, the present invention has the following advantages:
[0012] This invention provides a fixed-focus optical system with a focal length of 50mm, featuring high resolution, large aperture, low distortion, and a small number of lenses. This optical system exhibits day and night confocality, maintaining clear imaging under different lighting conditions throughout the day and night. With an f / 1.74 aperture and only 0.97% optical distortion, this system can resolve all fields of view at 250 Lp / mm. Its working distance is infinity, image size is 8.9mm, and total optical length is 59.5mm. At 350 Lp / mm, all fields of view achieve a resolution greater than 0.2. Compared to other fixed-focus lenses on the market, this invention offers higher resolution and image quality. While similar optical systems on the market typically have 8-9 lenses, this system has only 6, resulting in a smaller lens size compared to other lenses on the market. Attached Figure Description
[0013] Figure 1 A schematic diagram of the optical system structure provided by this utility model;
[0014] Figure 2 The MTF curve provided by this utility model at a resolution of 250 Lp / mm;
[0015] Figure 3 The MTF curve provided by this utility model at a resolution of 350 Lp / mm;
[0016] Figure 4 The distortion curve diagram provided for this utility model;
[0017] Figure 5 Illuminance curve provided for this utility model. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0020] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0021] In the description of this utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the utility model product is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.
[0022] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0023] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.
[0024] Example
[0025] like Figure 1As shown, a fixed-focus optical system includes a first biconvex lens L1, a second biconvex lens L2, a third biconcave lens L3, a fourth concave-convex lens L4, a fifth convex-concave lens L5, and a sixth convex-concave lens L6 arranged sequentially from the object side to the image side; the second biconvex lens L2 and the third biconcave lens L3 are cemented together to form a cemented lens group; an aperture stop STO is provided between the first biconvex lens L1 and the second biconvex lens L2; the optical system of this invention has a focal length of 50mm, an infinity working distance, an image plane size of 8.9mm, and a total optical length of 59.5mm. The first biconvex lens L1 has a refractive index of 1.35 ≤ n1 ≤ 1.80; the second biconvex lens L2 has a refractive index of 1.30 ≤ n2 ≤ 1.70; the third biconcave lens L3 has a refractive index of 1.45 ≤ n3 ≤ 1.85; the fourth biconvex-concave lens L4 has a refractive index of 1.5 ≤ n4 ≤ 2.00; the fifth biconvex-concave lens L5 has a refractive index of 1.50 ≤ n5 ≤ 1.90; the sixth biconvex-concave lens L6 has a refractive index of 11.45 ≤ n6 ≤ 1.95; the first biconvex lens L1 has a focal length of 45mm ≤ f1 ≤ 50mm; the second biconvex lens L2 has a focal length of 98mm ≤ f2 ≤ 103mm. The optical system comprises the following lenses: the third biconcave lens L3 has a focal length of -116mm ≤ f3 ≤ -111mm; the fourth concave-convex lens L4 has a focal length of -31mm ≤ f4 ≤ -26mm; the fifth convex-concave lens L5 has a focal length of 30mm ≤ f5 ≤ 35mm; and the sixth convex-concave lens L6 has a focal length of 74mm ≤ f6 ≤ 79mm. The optical system satisfies the following conditions: 0.8 ≤ f1 / Fw ≤ 1.5, 1.6 ≤ f2 / Fw ≤ 2.2, -0.7 ≤ f3 / Fw ≤ -1.4, 2.5 ≤ f4 / Fw ≤ 3.0, -0.3 ≤ f5 / Fw ≤ -0.9, and 0.8 ≤ f6 / Fw ≤ 1.5, where Fw is the focal length of the optical system.
[0026] The table below shows the optical parameters of the front and back of the six lenses.
[0027] Table 1 Optical parameters of the front and back surfaces of the six lenses
[0028] 1 46.638 5.159 1.57 71.3 28.934 59.002 2 -116.454 0.498 28.238 3 25.857 8.390 1.44 95.1 25.908 97.447 4 -27.411 1.563 1.64 42.4 24.604 -52.870 5 56.160 3.504 22.278 6 -30.673 3.330 2.00 20.7 22.142 144.476 7 -26.744 5.935 22.668 8 24.064 7.009 1.85 23.8 16.502 -36.572 9 11.773 8.553 12.302 10 23.167 7.021 1.88 40.8 12.396 54.169 11 38.314 8.548 10.77 Image infinity 0 8.914 Total length: 59.5088
[0029] like Figure 2 The figure shown is the MTF curve of this invention at a resolution of 250 Lp / mm. Figure 3 This is the MTF curve of this invention at a resolution of 350 Lp / mm. Figure 4 This is a distortion curve diagram of this utility model. Figure 5This is the illumination curve of this utility model. As can be seen from the figure, this utility model has higher resolution and lower distortion. The optical system of this utility model has F=1.74 and optical distortion of only 0.97%. All fields of view can be resolved at 250Lp / mm, and all fields of view can reach above 0.2 at 350Lp / mm. It has the characteristic of day and night confocality, maintaining clear imaging under different lighting conditions during the day and night, and realizing 24-hour continuous high-definition monitoring.
[0030] The preferred embodiments of this utility model have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of this utility model without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of this utility model through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.
Claims
1. A fixed-focus optical system, characterized in that, The optical system includes a first biconvex lens (L1), a second biconvex lens (L2), a third biconcave lens (L3), a fourth concave-convex lens (L4), a fifth convex-concave lens (L5), and a sixth convex-concave lens (L6) arranged sequentially from the object side to the image side; the second biconvex lens (L2) and the third biconcave lens (L3) are cemented together to form a cemented lens group; an aperture stop (STO) is provided between the first biconvex lens (L1) and the second biconvex lens (L2).
2. The fixed-focus optical system according to claim 1, characterized in that, The first biconvex lens (L1) has a refractive index of 1.35 ≤ n1 ≤ 1.80; the second biconvex lens (L2) has a refractive index of 1.30 ≤ n2 ≤ 1.70; the third biconcave lens (L3) has a refractive index of 1.45 ≤ n3 ≤ 1.85; the fourth biconvex-concave lens (L4) has a refractive index of 1.5 ≤ n4 ≤ 2.00; the fifth biconvex-concave lens (L5) has a refractive index of 1.50 ≤ n5 ≤ 1.90; and the sixth biconvex-concave lens (L6) has a refractive index of 11.45 ≤ n6 ≤ 1.
95.
3. A fixed-focus optical system according to claim 1, characterized in that, The first biconvex lens (L1) has a focal length of 45mm ≤ f1 ≤ 50mm; the second biconvex lens (L2) has a focal length of 98mm ≤ f2 ≤ 103mm; the third biconcave lens (L3) has a focal length of -116mm ≤ f3 ≤ -111mm; the fourth concave-convex lens (L4) has a focal length of -31mm ≤ f4 ≤ -26mm; the fifth convex-concave lens (L5) has a focal length of 30mm ≤ f5 ≤ 35mm; and the sixth convex-concave lens (L6) has a focal length of 74mm ≤ f6 ≤ 79mm.
4. A fixed-focus optical system according to claim 3, characterized in that, The optical system satisfies the following conditions: 0.8≤f1 / Fw≤1.5, 1.6≤f2 / Fw≤2.2, -0.7≤f3 / Fw≤-1.4, 2.5≤f4 / Fw≤3.0, -0.3≤f5 / Fw≤-0.9, 0.8≤f6 / Fw≤1.5, where Fw is the focal length of the optical system.
5. A fixed-focus optical system according to claim 1, characterized in that, The optical system is an optical system with a focal length of 50mm, an image size of 8.9mm, and a total optical length of 59.5mm.