A wide-angle lens
By employing a hybrid design of glass spherical and plastic aspherical lenses in a wide-angle lens, the problems of high cost, heavy weight, and large distortion have been solved, achieving low cost, miniaturization, wide angle of view, low distortion, and temperature adaptability, thereby improving the lens's performance and resolution.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING JINGWEI HIRAIN TECH CO INC
- Filing Date
- 2022-11-24
- Publication Date
- 2026-06-23
AI Technical Summary
Existing wide-angle lenses suffer from high cost, heavy weight, difficulty in miniaturization, and significant distortion. Furthermore, the large coefficient of thermal expansion of plastic lenses leads to severe temperature drift.
The design employs a hybrid approach combining a first lens group and a second lens group, including glass spherical and plastic aspherical lenses. By defining the optical power and aspherical surface shape, and combining the characteristics of glass spherical and plastic aspherical lenses, it achieves rapid light convergence and distortion control.
It achieves low cost, miniaturization, wide viewing angle, low distortion, day and night confocality, and temperature adaptability, reduces distortion, improves peripheral image resolution, and maintains good performance in high and low temperature environments.
Smart Images
Figure CN115755350B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optical imaging technology, specifically to a wide-angle lens. Background Technology
[0002] With the rapid development and widespread application of intelligent safety-assisted driving monitoring systems, the requirements for wide-angle monitoring lenses are constantly increasing. Today's wide-angle lenses are constantly developing towards low cost, miniaturization, wide angle, low distortion, day and night confocality, and temperature adaptability. Accordingly, the research and development of new architecture wide-angle lenses is urgently needed. Existing technology uses a spherical glass lens structure to achieve the above effects.
[0003] While glass lenses offer superior temperature characteristics, their use as a sole component results in relatively high cost and weight. Spherical lenses also hinder external field-of-view aberration correction for miniaturization, and their distortion correction is less effective than aspherical lenses, leading to relatively larger distortions. Plastic aspherical lenses, on the other hand, are cheaper and lighter, offering significant advantages in distortion correction and overcoming the aforementioned drawbacks. However, their higher coefficient of thermal expansion causes severe temperature drift, complicating lens temperature control design. Summary of the Invention
[0004] To solve the above-mentioned technical problems, the present invention proposes a wide-angle lens, including a first lens group and a second lens group arranged from the object side to the image side. The first lens group includes a first lens L1, a second lens L2 and a third lens L3, and the second lens group includes a fourth lens L4, a fifth lens L5 and a sixth lens L6. Both the first lens group and the second lens group have positive optical power.
[0005] The first lens L1 and the third lens L3 are spherical glass surfaces, while the second lens L2, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are all aspherical plastic lenses. The fourth lens L4 and the fifth lens L5 are a cemented doublet lens, and satisfy the following conditions:
[0006] 2 < F11 / F < 17.4;
[0007] 2.07 < F22 / F < 2.526;
[0008] Wherein, F11 is the focal length of the first lens group, F22 is the focal length of the second lens group, and F is the focal length of the wide-angle lens.
[0009] Optionally, the aspherical surface shapes of the second lens L2, the fourth lens L4, the fifth lens L5, and the sixth lens L6 all satisfy formula (1):
[0010] / + + + (1);
[0011] In formula (1), 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 k is less than -1, the surface curve of the lens is a hyperbola; when k is equal to -1, the surface curve of the lens is a parabola; when k is between -1 and 0, the surface curve of the lens is an ellipse; when k is equal to 0, the surface curve of the lens is a circle; when 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; and Z is the height of the incident ray on the aspherical surface.
[0012] Optionally, the first lens L1 is a meniscus negative lens bent toward the image plane, the second lens L2 is a meniscus negative lens bent toward the image side, the third lens L3 is a biconvex positive lens, the fourth lens L4 is a biconvex positive lens, the fifth lens L5 is a meniscus negative lens bent toward the object side, and the sixth lens L6 is a biconvex positive lens.
[0013] Optionally, the cemented doublet lens satisfies: -85.8 < F45 / F < -3.79, where F45 is the focal length of the cemented doublet lens.
[0014] Optionally, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 respectively satisfy: Nd1≥1.72, 1.5≤Nd2≤1.6, 1.65≤Nd3≤1.85, 1.5≤Nd4≤1.6, 1.6≤Nd5≤1.7, and 1.5≤Nd6≤1.6; where Nd1 is the D-index of the first lens L1, Nd2 is the D-index of the second lens L2, Nd3 is the D-index of the third lens L3, Nd4 is the D-index of the fourth lens L4, Nd5 is the D-index of the fifth lens L5, and Nd6 is the D-index of the sixth lens L6.
[0015] Optionally, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 respectively satisfy: 45≤Vd1≤60, 45≤Vd2≤60, 25≤Vd3≤45, 45≤Vd4≤60, 25≤Vd5≤45, and 45≤Vd6≤60; where Vd1 is the Abbe number of the first lens L1, Nd2 is the Abbe number of the second lens L2, Nd3 is the Abbe number of the third lens L3, Nd4 is the Abbe number of the fourth lens L4, Nd5 is the Abbe number of the fifth lens L5, and Nd6 is the Abbe number of the sixth lens L6.
[0016] Optionally, the first lens L1 satisfies: 1.1 < 2r2 / D2, where D2 is the aperture of the first lens on the side closer to the image plane, and r2 is the radius of curvature of the first lens on the side closer to the image plane.
[0017] Optionally, the focal lengths of the first lens L6, the second lens L2, and the sixth lens L6 respectively satisfy: -3.99 < F1 / F < -3.66, -1.838 < F2 / F < -1.524, and 1.528 < F6 / F < 2, where F1 is the focal length of the first lens L1, F2 is the focal length of the second lens L2, and F6 is the focal length of the sixth lens L6.
[0018] Optionally, the focal length of the third lens L3 and the cemented doublet combined lens satisfy: -0.429 < F3 / F45 < -0.304, where F3 is the focal length of the third lens L3 and F45 is the focal length of the cemented doublet combined lens.
[0019] Optionally, the wide-angle lens further includes: an aperture stop, an IR filter, and a protective glass arranged sequentially from the object side to the image side; the aperture stop is disposed between the first lens group and the second lens group, the IR filter is disposed on the image plane side of the second lens group, and the protective glass is disposed on the image plane side of the IR filter.
[0020] The technical effects of this invention include, but are not limited to, the following:
[0021] 1. This invention employs four plastic aspherical lenses, cementing the fourth and fifth lenses together. Both the first and second lens groups have positive optical power, which is beneficial for the rapid convergence of light and also provides good control over distortion.
[0022] 2. By defining the second, fourth, fifth, and sixth lenses as plastic aspherical surfaces and specifying the shape of these aspherical surfaces, further control over distortion is achieved. Defining the first lens as a glass spherical surface improves the reliability of the optical lens and its adaptability to complex environments; defining the third lens as a glass spherical surface improves the temperature adaptability of the optical lens.
[0023] 3. This invention employs a structure of two glass lenses and four aspherical plastic lenses. The use of plastic aspherical lenses significantly reduces product costs, resulting in a clear competitive advantage in the market. The application of plastic aspherical lenses greatly reduces distortion, which in turn significantly improves the resolution of peripheral images during product application. The structure of two glass spherical lenses and four plastic aspherical lenses, utilizing the combination of convex and concave shapes of the plastic lenses, adjusts for back focus changes caused by high-temperature expansion, achieving optimal temperature drift.
[0024] 4. Set 2 < F 11 / F < 17.4, 2.07 < F 22 With an aperture of F < 2.526, the power distribution between the two groups is beneficial for aberration correction and tolerance allocation, achieving high resolution requirements. This setting ensures a smaller optical length for the lens, giving it an advantage over other structures or power distributions of the same length, or in other words, a smaller size while maintaining the same resolution requirements. Furthermore, this power distribution allows light, especially off-axis light, to have a smaller angle of incidence at the aperture stop, resulting in better tolerance performance and superior resolution in the actual product. Finally, this power distribution is more favorable for on-axis light convergence, and when combined with aspherical lenses, it ensures that the outer field of view has the same resolution as on-axis light, achieving equal resolution for both on-axis and off-axis lenses.
[0025] 5. The distribution of optical power among the lenses is beneficial for the correction and balance of aberrations and the convergence of on-axis and off-axis light rays, thereby achieving lens miniaturization and high resolution requirements.
[0026] 6. Four plastic aspherical lenses can effectively control distortion and control the shape of each lens to reduce stray light and ghosting, meeting the shooting requirements of wide-angle lenses; at the same time, they can correct the seidel coefficient of visible light and infrared light to reduce the sensitivity of each lens; in addition, the lens has a regular shape, simple structure, and is easy to process and assemble. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the lens structure in Example 1;
[0028] Figure 2 This is the MTF curve of the visible light band in Example 1;
[0029] Figure 3 This is the MTF curve of the infrared (940nm) band in Example 1;
[0030] Figure 4 This is the defocus curve of the center field of view at 20°C in the visible light band of Example 1 at 60 lp / mm.
[0031] Figure 5 This is the defocus curve of the center field of view at -40℃ in the visible light band of Example 1 at 60lp / mm.
[0032] Figure 6 This is the defocus curve of the center field of view at 60 lp / mm in the visible light band at 85°C, as shown in Example 1.
[0033] Figure 7 This is the field distortion diagram of Example 1.
[0034] Wherein: L1 is the first lens, L2 is the second lens, L3 is the third lens, S is the aperture stop, L4 is the fourth lens, L5 is the fifth lens, L6 is the sixth lens, IR is the color filter, and IMA is the image plane. Detailed Implementation
[0035] 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 them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0036] It should be noted that the terms "comprising" and "having," and any variations thereof, in the embodiments and drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.
[0037] like Figure 1As shown, this invention provides a wide-angle lens that meets the requirements of low cost, miniaturization, wide angle of view, low distortion, day and night confocal focus, and temperature adaptability. The wide-angle lens includes a first lens group and a second lens group arranged from the object side to the image side. The first lens group includes a first lens L1, a second lens L2, and a third lens L3, and has positive optical power, which is beneficial for the rapid convergence of light. The second lens group includes a fourth lens L4, a fifth lens L5, and a sixth lens L6, and also has positive optical power. The first lens L1 and the third lens L3 are spherical glass lenses, while the rest are plastic aspherical lenses (i.e., the second lens L2, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are all plastic aspherical lenses). The fourth lens L4 and the fifth lens L5 are a set of cemented lenses.
[0038] The first lens group and the second lens group satisfy the following relationship:
[0039] 2 < F11 / F < 17.4;
[0040] 2.07 < F22 / F < 2.526;
[0041] Where F11 is the focal length of the first lens group, F22 is the focal length of the second lens group, and F is the focal length of the wide-angle lens.
[0042] In one implementation, the solution further includes, sequentially arranged from the object side to the image side: an aperture stop, an IR filter, and a protective glass. The aperture stop is positioned between the first lens group and the second lens group, the IR filter is positioned on the image plane side of the second lens group, and the protective glass is positioned on the image plane side of the IR filter.
[0043] In one implementation, the first lens L1 is a meniscus negative lens bent toward the image plane; the second lens L2 is a meniscus negative lens bent toward the image side; the third lens L3 is a biconvex positive lens; the fourth lens L4 is a biconvex positive lens; the fifth lens L5 is a meniscus negative lens bent toward the object side; the sixth lens L6 is a biconvex positive lens; and the fourth lens and the fifth lens are combined to form a cemented doublet lens.
[0044] In one implementation, the cemented doublet lens satisfies: -85.8 < F45 / F < -3.79, where F45 is the focal length of the cemented doublet lens;
[0045] By limiting -85.8 < F45 / F < -3.79, the seidel coefficient of a wide-angle lens and its adaptability to high and low temperatures can be controlled.
[0046] In one implementation, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 satisfy the following: Nd1 ≥ 1.72, 1.5 ≤ Nd2 ≤ 1.6, 1.65 ≤ Nd3 ≤ 1.85, 1.5 ≤ Nd4 ≤ 1.6, 1.6 ≤ Nd5 ≤ 1.7, and 1.5 ≤ Nd6 ≤ 1.6; where Nd1 is the D-index of the first lens L1, Nd2 is the D-index of the second lens L2, Nd3 is the D-index of the third lens L3, Nd4 is the D-index of the fourth lens L4, Nd5 is the D-index of the fifth lens L5, and Nd6 is the D-index of the sixth lens L6.
[0047] By limiting the first lens L1 to satisfy Nd1≥1.72, light from a wider field of view can be effectively converged, reducing the aperture of the first lens L1 and facilitating the miniaturization of optical lenses.
[0048] In one implementation, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 satisfy the following: 45≤Vd1≤60, 45≤Vd2≤60, 25≤Vd3≤45, 45≤Vd4≤60, 25≤Vd5≤45, and 45≤Vd6≤60; where Vd1 is the Abbe number of the first lens L1, Vd2 is the Abbe number of the second lens L2, Vd3 is the Abbe number of the third lens L3, Vd4 is the Abbe number of the fourth lens L4, Vd5 is the Abbe number of the fifth lens L5, and Vd6 is the Abbe number of the sixth lens L6.
[0049] By limiting the D-index and Abbe number of each lens, it is beneficial to achieve aberration correction. In particular, the combination of the D-index and Abbe number of the third, fourth and fifth lenses, and the use of two cemented lenses for the fourth and fifth lenses, are beneficial to achieving the requirements of high resolution and infrared confocality, ensuring that both visible and infrared light have high resolution.
[0050] In one implementation, the first lens satisfies: 1.1 < 2r² / D², where D² is the aperture of the first lens on the side closest to the image plane, and r² is the radius of curvature of the first lens on the side closest to the image plane.
[0051] By limiting 1.1 < 2r² / D², the risk of the first lens L1 being hemispherical can be effectively controlled, which is beneficial to the processing of the first lens L1; at the same time, the first lens L1 has a certain curvature, which can correct the aberration of the optical system to a certain extent, which is one of the inventive points of this invention.
[0052] In one implementation, the focal lengths of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 satisfy the following: -3.99 < F1 / F < -3.66, -1.838 < F2 / F < -1.524, -0.429 < F3 / F45 < -0.304, 1.528 < F6 / F < 2, where 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, F45 is the focal length of the fourth and fifth lenses (cement), and F6 is the focal length of the sixth lens.
[0053] By limiting -0.429 < F3 / F45 < -0.304, temperature adaptability can be effectively controlled, which is beneficial for the lens to have better performance at high or low temperatures.
[0054] In one implementation, the second lens L2, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are all plastic aspherical surfaces, and their aspherical surface shapes all satisfy formula (1):
[0055] / + + + (1);
[0056] In formula (1), parameter c is the curvature corresponding to the radius, y is the radial coordinate, and its unit is the same as the unit of the lens length. 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. 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, and Z is the height of the incident ray on the aspherical surface.
[0057] The following embodiment illustrates how the present invention, through the combined use of glass spherical lenses and plastic aspherical lenses, can improve upon the shortcomings of the prior art while still maintaining good optical performance.
[0058] Example 1
[0059] The optical parameters in Embodiment 1 of this invention are shown in Table 1.
[0060] ;
[0061] In Table 1, such as Figure 1The first column shows the surface numbers of the 15 surfaces, which are in sequence the object and image surfaces of the first lens L1, the second lens L2, the third lens L3, the aperture S, the object and image surfaces of the fourth lens L4, the fifth lens L5, the sixth lens L6, the mirror surface of the IR filter L8, and the image surface IMA.
[0062] The parameters for each lens are shown in Table 2.
[0063] ;
[0064] Wherein, FOV represents the maximum field of view of the lens, and h represents the image height corresponding to the maximum FOV.
[0065] See Figure 2 , Figure 3 At a resolution frequency of 60 lp / mm, the MTF of the center (0,0) field of view in the visible light band can approach 0.9, with a concentrated curve and high resolution; the MTF of the center (0,0) field of view in the infrared band at 940nm can approach 0.8, with the decrease in the center (0,0) field of view relative to the visible light center (0,0) field of view being within 10%, and the curve being relatively concentrated. This indicates that the infrared confocality of the wide-angle lens is good.
[0066] See Figure 4 , Figure 5 , Figure 6 In the visible light band, at a center field of view of (0,0) and 60 lp / mm, the lens exhibits a significantly smaller defocus at -40℃ and 85℃ compared to a normal temperature of 20℃, generally within 4 micrometers. This demonstrates that the wide-angle lens possesses excellent temperature characteristics and... Figure 7 The result shows relatively small optical distortion.
[0067] Those skilled in the art will understand that the modules in the apparatus of the embodiments can be distributed in the apparatus of the embodiments as described in the embodiments, or they can be located in one or more devices different from this embodiment with corresponding changes. The modules of the above embodiments can be combined into one module, or they can be further divided into multiple sub-modules.
[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A wide-angle lens, comprising a first lens group and a second lens group arranged from the object side to the image side, the first lens group comprising a first lens L1, a second lens L2 and a third lens L3, the second lens group comprising a fourth lens L4, a fifth lens L5 and a sixth lens L6, both the first lens group and the second lens group having positive optical power; Its features are: The first lens L1 and the third lens L3 are glass spherical lenses, while the second lens L2, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are all plastic aspherical lenses. The fourth lens L4 and the fifth lens L5 are a cemented doublet lens, and the parameters of each lens satisfy the conditions shown in Table 1. ； The wide-angle lens has 6 lens elements with optical power.
2. The wide-angle lens according to claim 1, characterized in that, The aspherical surface shapes of the second lens L2, the fourth lens L4, the fifth lens L5, and the sixth lens L6 all satisfy formula (1): / + + + （1） In formula (1), 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 k is less than -1, the surface curve of the lens is a hyperbola; when k is equal to -1, the surface curve of the lens is a parabola; when k is between -1 and 0, the surface curve of the lens is an ellipse; when k is equal to 0, the surface curve of the lens is a circle; when 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; and Z is the height of the incident ray on the aspherical surface.
3. The wide-angle lens according to claim 1, characterized in that, The first lens L1 is a meniscus negative lens bent toward the image plane, the second lens L2 is a meniscus negative lens bent toward the image side, the third lens L3 is a biconvex positive lens, the fourth lens L4 is a biconvex positive lens, the fifth lens L5 is a meniscus negative lens bent toward the object side, and the sixth lens L6 is a biconvex positive lens.
4. The wide-angle lens according to claim 1, characterized in that, The first lens L1 satisfies: 1.1 < 2r2 / D2; where D2 is the aperture of the first lens on the side closer to the image plane, and r2 is the radius of curvature of the first lens on the side closer to the image plane.
5. The wide-angle lens according to claim 1, characterized in that, Also includes: An aperture stop, an IR filter, and a protective glass are arranged sequentially from the object side to the image side; the aperture stop is located between the first lens group and the second lens group, the IR filter is located on the image plane side of the second lens group, and the protective glass is located on the image plane side of the IR filter.