Prime lens
By rationally setting the lens power and surface shape of the fixed-focus lens, the problems of large size, small aperture, and large distortion of telephoto lenses were solved, achieving miniaturization, large aperture, and clear imaging.
Patent Information
- Application Number
- CN202520138209.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-21
- Publication Date
- 2025-12-09
- Estimated Expiration
- 2035-01-21
AI Technical Summary
Existing telephoto lenses suffer from problems such as large size, small aperture, and large distortion, resulting in poor image quality.
Design a fixed-focus lens that, by rationally setting the optical power combination and surface shape of seven lenses, including a negative-positive-positive-positive-negative-positive-negative optical power combination, and setting an aperture stop at the aperture stop position, combined with the concave and convex surface shape of the lenses, reduces stray light interference and achieves small size, large aperture and clear imaging.
It achieves a miniaturized, large-aperture, and high-image-quality fixed-focus lens, reducing optical system distortion and stray light interference, and improving image clarity.
Smart Images
Figure CN223650814U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of optical device technology, and in particular to a fixed-focus lens. Background Technology
[0002] As security cameras are used in more and more fields and the requirements for long-distance shooting become higher, the advantages of telephoto lenses are becoming more and more obvious.
[0003] Currently, telephoto lenses on the market generally suffer from the following drawbacks: large size, small aperture, and large distortion leading to poor image quality. Utility Model Content
[0004] This invention provides a fixed-focus lens that, by reasonably setting the number of lenses, the optical power matching method, and the concave-convex surface method, can achieve a fixed-focus lens with small size, large aperture, and clear image.
[0005] This utility model embodiment provides a fixed-focus lens, including a first lens, a second lens, an aperture stop, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the object plane to the image plane;
[0006] The first lens is a negative power lens, the second lens is a positive power lens, the third lens is a positive power lens, the fourth lens is a positive power lens, the fifth lens is a negative power lens, the sixth lens is a positive power lens, and the seventh lens is a negative power lens; furthermore, the object-side surface of the second lens is concave, and the image-side surface is convex; the object-side surface of the third lens is convex, and the image-side surface is concave.
[0007] Optionally, the object-side surface of the first lens is convex, and the image-side surface is concave.
[0008] The object-side surface of the fourth lens is convex, and the image-side surface is also convex.
[0009] The object-side surface of the fifth lens is convex, and the image-side surface is concave.
[0010] The object-side surface of the sixth lens is convex, and the image-side surface is also convex.
[0011] The object-side surface of the seventh lens is convex, and the image-side surface is concave.
[0012] Optionally, the optical power of the first lens is The optical power of the second lens is The optical power of the third lens is The optical power of the fourth lens is: The optical power of the fifth lens is The optical power of the sixth lens is: The optical power of the seventh lens is The optical power of the fixed-focus lens is:
[0013] in,
[0014] Optionally, the refractive index of the second lens is Nd2, and the Abbe number of the second lens is Vd2; the refractive index of the fourth lens is Nd4; and the refractive index of the fifth lens is Nd5, and the Abbe number of the fifth lens is Vd5.
[0015] Wherein, 1.65≤Nd2≤1.68, 18≤Vd2≤25;
[0016] 1.44≤Nd4≤1.78;
[0017] 1.63≤Nd5≤1.68、18.7≤Vd5≤25。
[0018] Optionally, the back focal length of the fixed-focus lens is BFL, and the total optical length is TTL;
[0019] Among them, BFL / TTL≥0.228.
[0020] Optionally, the focal length of the fixed-focus lens is EFL, and the total optical length is TTL;
[0021] Wherein, 0.321≤EFL / TTL≤0.357.
[0022] Optionally, the aperture number of the fixed-focus lens is F#;
[0023] Where F#≤1.31.
[0024] Optionally, the optical assembly of the fixed-focus lens is TTL;
[0025] Among them, TTL≤21.764mm.
[0026] Optionally, the first lens, the second lens, the third lens, the fifth lens, the sixth lens, and the seventh lens are all plastic aspherical lenses;
[0027] The fourth lens is a glass spherical lens.
[0028] Optionally, the fixed-focus lens may also include a filter;
[0029] The filter is disposed in the optical path between the seventh lens and the image plane.
[0030] The fixed-focus lens provided in this embodiment includes seven lenses with optical power, and these seven lenses are arranged in a negative-positive-positive-positive-negative-positive-negative optical power configuration, which is beneficial for achieving miniaturization and a large aperture fixed-focus lens. Furthermore, the third lens uses a convex-concave shape to adjust the light passing through the aperture stop, allowing the light to smoothly enter the subsequent optical system. The interaction between the convex-concave shape of the third lens and the concave-convex shape of the second lens at the aperture stop reduces stray light reflected at the aperture stop, minimizing interference from stray light on imaging and improving image sharpness.
[0031] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description
[0032] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0033] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 1 of this utility model;
[0034] Figure 2 This is a schematic diagram of field curvature distortion of a fixed-focus lens provided in Embodiment 1 of this utility model;
[0035] Figure 3 This is a schematic diagram of a fixed-focus lens Ray Fan provided in Embodiment 1 of this utility model;
[0036] Figure 4 This is a schematic diagram of the vertical chromatic aberration of a fixed-focus lens provided in Embodiment 1 of this utility model;
[0037] Figure 5 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of this utility model;
[0038] Figure 6 This is a schematic diagram of field curvature distortion of a fixed-focus lens provided in Embodiment 2 of this utility model;
[0039] Figure 7 This is a schematic diagram of a fixed-focus lens Ray Fan provided in Embodiment 2 of this utility model;
[0040] Figure 8This is a schematic diagram of the vertical chromatic aberration of a fixed-focus lens provided in Embodiment 2 of this utility model;
[0041] Figure 9 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 3 of this utility model;
[0042] Figure 10 This is a schematic diagram of field curvature distortion of a fixed-focus lens provided in Embodiment 3 of this utility model;
[0043] Figure 11 This is a schematic diagram of a fixed-focus lens Ray Fan provided in Embodiment 3 of this utility model;
[0044] Figure 12 This is a schematic diagram of the vertical chromatic aberration of a fixed-focus lens provided in Embodiment 3 of this utility model. Detailed Implementation
[0045] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.
[0046] Example 1
[0047] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 1 of this utility model, as shown below. Figure 1 As shown, the fixed-focus lens provided in Embodiment 1 of this utility model includes a first lens 101, a second lens 102, an aperture stop 100, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, and a seventh lens 107 arranged sequentially along the optical axis from the object plane to the image plane; the first lens 101 is a negative power lens, the second lens 102 is a positive power lens, the third lens 103 is a positive power lens, the fourth lens 104 is a positive power lens, the fifth lens 105 is a negative power lens, the sixth lens 106 is a positive power lens, and the seventh lens 107 is a negative power lens; furthermore, the object-side surface of the second lens 102 is concave, and the image-side surface is convex; the object-side surface of the third lens 103 is convex, and the image-side surface is concave.
[0048] Specifically, the fixed-focus lens provided in this embodiment includes seven lenses with optical power: a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, and a seventh lens 107. The arrangement of the seven lenses ensures that the number of lenses in the optical system is reasonable. Too many lenses will result in a large lens size, and too few lenses will result in a large aberration due to a single lens bearing a large optical power. This ensures that the optical system is miniaturized while maintaining small imaging aberrations and high imaging quality.
[0049] Furthermore, optical power is equal to the difference between the convergence of the beam at the image plane and the convergence of the beam at the object plane; it characterizes the ability of an optical system to deflect light rays. The larger the absolute value of the optical power, the stronger its ability to bend light rays; the smaller the absolute value, the weaker its ability to bend light rays. When the optical power is positive, the refraction of light rays is converging; when the optical power is negative, the refraction of light rays is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a system formed by multiple lenses (i.e., a lens group).
[0050] In this embodiment of the invention, the first lens 101 is a negative power lens. As the first lens in a fixed-focus lens to adjust the incident light, its negative power setting ensures that the light has a larger aperture before entering the aperture stop, increasing the aperture of the fixed-focus lens and enabling the lens to still produce clear images under dim or dark conditions. The second lens 102 and the third lens 103 are both positive power lenses, working together to ensure that the light passes smoothly through the aperture stop, avoiding reflections and other stray light at the aperture stop position, reducing the impact of stray light on imaging, and improving the imaging effect. The fourth lens 104 is a positive power lens, the fifth lens 105 is a negative power lens, and the sixth lens 106 is a positive power lens. The positive-negative-positive power combination of the fourth lens 104, the fifth lens 105, and the sixth lens 106 is beneficial for adjusting the aberrations of the fixed-focus lens. The seventh lens 107, as the lens closest to the image plane and possessing power, has a negative power design that can expand the target area size of the fixed-focus lens and ensure that the fixed-focus lens has sufficiently clear imaging. Furthermore, the fourth lens 104 to the seventh lens 107 adopt a positive-negative-positive-negative combination, and the optical power of each subsequent lens in the optical path is different from that of the previous lens, which is beneficial for aberration correction.
[0051] Furthermore, the fixed-focus lens also includes an aperture stop STO. Setting the aperture stop STO allows adjustment of the beam propagation direction, which helps improve image quality. In this fixed-focus lens, the aperture stop STO is located in the optical path between the second lens 102 and the third lens 103, meaning the aperture stop STO is integrated into the optical system. This allows for a smaller aperture value, achieving a large aperture. In this embodiment, the system's aperture number is F#; where F# ≤ 1.31, satisfying the imaging requirements of a large aperture.
[0052] Furthermore, as the two lenses before and after the STO aperture, the second lens 102 has a concave object-side surface and a convex image-side surface; the third lens 103 has a convex object-side surface and a concave image-side surface. The object-side surface of a lens can be understood as the surface of the lens closest to the object plane, and the image-side surface can be understood as the surface of the lens closest to the image plane. The second lens 102's concave object-side surface and convex image-side surface can be understood as the object-side surface of the second lens 102 being concave towards the object plane near the optical axis, and the image-side surface being convex towards the image plane near the optical axis; that is, the second lens 102 is a lens with a concave-convex structure. The design of the second lens 102 as a concave-convex negative lens can effectively control the direction of light, reduce field curvature and spherical aberration of the optical system, and improve the image quality of the optical system. Similarly, the third lens 103's convex object-side surface and concave image-side surface can be understood as the object-side surface of the third lens 103 being convex towards the object plane near the optical axis, and the image-side surface being concave towards the image plane near the optical axis; that is, the third lens 103 is a lens with a convex-concave structure. The third lens 103 uses a convex-concave lens to adjust the light passing through the aperture STO, so that the light can smoothly enter the subsequent optical system. Furthermore, the interaction between the convex-concave surface of the third lens 103 and the concave-convex surface of the second lens 102 at the front end of the aperture STO can reduce stray light generated by reflection at the aperture STO position, reduce the interference of stray light on imaging, and improve the imaging effect.
[0053] In summary, the fixed-focus lens provided by this utility model embodiment, by reasonably setting the number of lenses, the optical power matching method of the lenses, and the concave and convex surface shape of some lenses, can achieve the design of a fixed-focus lens with a large aperture, small size, and clear imaging.
[0054] Based on the above embodiments, continue to refer to Figure 1 As shown, the fixed-focus lens provided in this embodiment of the present invention may further include a filter 108; the filter 108 is disposed in the optical path between the seventh lens 107 and the image plane.
[0055] Furthermore, the filter 108 is disposed in the optical path between the seventh lens 107 and the image plane to filter out stray light and improve the imaging effect.
[0056] Furthermore, the fixed-focus lens provided in this embodiment may also include a protective glass and an image acquisition element. The protective glass may be disposed on the image-side of the filter, and the image acquisition element may be disposed on the image-side of the protective glass. The optical system is protected by the protective glass, and the image acquisition element acquires images, thus enabling the optical system to perform its normal imaging function.
[0057] Based on the above embodiments, continue to refer to Figure 1 As shown, the object-side surface of the first lens 101 is convex, and the image-side surface is concave; the object-side surface of the fourth lens 104 is convex, and the image-side surface is convex; the object-side surface of the fifth lens 105 is convex, and the image-side surface is concave; the object-side surface of the sixth lens 106 is convex, and the image-side surface is convex; and the object-side surface of the seventh lens 107 is convex, and the image-side surface is concave.
[0058] Specifically, the object-side surface of the first lens 101 is convex, and the image-side surface is concave. This can be understood as the object-side surface of the first lens 101 bulging towards the object plane near the optical axis, and the image-side surface concave towards the image plane near the optical axis; in other words, the first lens 101 is a lens with a convex-concave structure. Furthermore, the first lens 101 can be a meniscus negative lens. The surface shape of the first lens 101, combined with its optical power parameters, can converge light rays from a large field of view into the system as much as possible, which is beneficial for improving the field of view of the optical system.
[0059] The fourth lens 104 has a convex object-side surface and a convex image-side surface. This can be understood as the object-side surface of the fourth lens 104 bulging towards the object plane near the optical axis, and the image-side surface bulging towards the image plane near the optical axis. Therefore, the fourth lens 140 is a biconvex lens. The fifth lens 105 has a convex object-side surface and a concave image-side surface. This can be understood as the object-side surface of the fifth lens 105 bulging towards the object plane near the optical axis, and the image-side surface concave towards the image plane near the optical axis. Therefore, the fifth lens 105 is a convex-concave lens. The sixth lens 106 has a convex object-side surface and a convex image-side surface. This can be understood as the object-side surface of the sixth lens 106 bulging towards the object plane near the optical axis, and the image-side surface bulging towards the image plane near the optical axis. Therefore, the sixth lens 106 is a biconvex lens. The object-side surface of the seventh lens 107 is convex, and the image-side surface is concave. This can be understood as the object-side surface of the seventh lens 107 bulging towards the object plane near the optical axis, and the image-side surface concave towards the image plane near the optical axis; in other words, the seventh lens 107 is a lens with a convex-concave structure. The surface design of the fifth to eighth lenses 108, combined with their power settings, is beneficial for correcting off-axis aberrations and improving image quality.
[0060] Based on the above embodiments, the optical power of the first lens 101 is: The optical power of the second lens 102 is The optical power of the third lens 103 is: The optical power of the fourth lens 104 is
[0061] The optical power of the fifth lens 105 is The optical power of the sixth lens 106 is The optical power of the seventh lens 107 is The optical power of a fixed-focus lens is in,
[0062] By controlling the optical power of the entire fixed-focus lens to be distributed in a certain proportion, the balance of the incident angle of the front and rear lens elements is ensured, thereby reducing the sensitivity of the lens elements, which helps to reduce distortion and improve the stability of the fixed-focus lens.
[0063] Based on the above embodiments, the refractive index of the second lens 102 is Nd2, and the Abbe number of the second lens 102 is Vd2; the refractive index of the fourth lens 104 is Nd4; the refractive index of the fifth lens 105 is Nd5, and the Abbe number of the fifth lens 102 is Vd5; wherein, 1.65≤Nd2≤1.68, 18≤Vd2≤25; 1.44≤Nd4≤1.78; 1.63≤Nd5≤1.68, 18.7≤Vd5≤25.
[0064] Specifically, refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium, mainly used to describe a material's ability to refract light; different materials have different refractive indices. The Abbe number is an index used to represent the dispersion ability of a transparent medium; the more severe the dispersion, the smaller the Abbe constant; conversely, the less severe the dispersion, the larger the Abbe constant. In this embodiment, the second lens 102 and the fifth lens 105 use high-refractive-index plastic lenses. Controlling the refractive index and Abbe number of the second lens 102 can control the increase in the aperture number of the fixed-focus lens and avoid difficult-to-solve advanced aberrations at the front of the lens. Controlling the refractive index of the fourth lens 104 can reasonably balance the refractive index distribution of the entire fixed-focus lens, ensuring smooth light transmission. Reasonably controlling the refractive index and Abbe number of the fifth lens 105 can avoid the effects of advanced aberrations.
[0065] Based on the above embodiments, the back focal length of the fixed-focus lens is BFL, and the total optical length is TTL; wherein, BFL / TTL≥0.228. The reasonable selection of the back focal length and total length ensures that the lens meets telephoto requirements while guaranteeing sufficient mounting space for the imaging sensor and flat panel filter. This also ensures that the lens will not interfere with the base and housing during installation, and maintains a simple manufacturing process for the fixed-focus lens.
[0066] Based on the above embodiments, the focal length of the fixed-focus lens is EFL, and the total optical length is TTL; wherein, 0.321≤EFL / TTL≤0.357. By controlling the ratio of focal length to total length, the total length can be shortened while keeping the focal length constant, which is beneficial for reducing the size of the telephoto lens while ensuring optical performance.
[0067] Specifically, in this embodiment of the present invention, the total optical length of the fixed-focus lens is TTL; wherein, TTL≤21.764mm, so as to realize a fixed-focus lens with a smaller total optical length and achieve miniaturization design of the fixed-focus lens.
[0068] Based on the above embodiments, the first lens 101, the second lens 102, the third lens 103, the fifth lens 105, the sixth lens 106 and the seventh lens 107 are all plastic aspherical lenses; the fourth lens 104 is a glass spherical lens.
[0069] Specifically, aspherical lenses are characterized by a continuous change in curvature from the center to the periphery, unlike spherical lenses which have a constant curvature from the center to the periphery. Aspherical lenses possess superior curvature radius characteristics, offering advantages in improving distortion and astigmatism. Furthermore, the use of plastic aspherical lenses simplifies manufacturing processes and reduces their cost, thus lowering the overall cost of the optical system. Therefore, by using plastic aspherical lenses for the first lens 101, second lens 102, third lens 103, fifth lens 105, sixth lens 106, and seventh lens 107, the cost of fixed-focus lenses can be reduced while simultaneously improving distortion and astigmatism.
[0070] Spherical lenses are characterized by a constant curvature from the center to the periphery, ensuring a simple lens setup. Furthermore, due to the low coefficient of thermal expansion and good stability of glass lenses, the fourth lens 104 is a glass spherical lens. The thermal properties of glass spherical lenses are more stable, ensuring good resolving power over a wide temperature range for fixed-focus lenses when handling higher focal lengths. In addition, compared to plastic aspherical lenses, glass offers a wider range of material choices, with more freedom in selecting the refractive index and Abbe number. This allows for better control over higher aberrations and chromatic aberrations, meeting the needs of use under complex conditions.
[0071] Therefore, the fixed-focus lens provided in this embodiment of the utility model can adopt a combination of plastic aspherical lenses and glass spherical lenses, which can effectively control the cost of the fixed-focus lens while ensuring its optical performance; at the same time, the materials of each lens have a mutual compensating effect, which can ensure that it can still be used normally in high and low temperature environments.
[0072] As a feasible implementation method, the specific parameters of the fixed-focus lens will be explained below.
[0073] Table 1. Optical design values for a fixed-focus lens in Example 1.
[0074]
[0075] Table 2 Design values of optical physical parameters for a fixed-focus lens
[0076] Face number Surface type radius of curvature thickness Materials (nd) Materials (vd) 1 aspherical 4.235 1.134 1.54 55 2 aspherical 2.566 1.691 3 Standard surface INF 0.863 4 aspherical -5.005 1.419 1.68 19 5 aspherical -4.838 -1.000 6 STO INF 1.030 7 aspherical 4.525 0.734 1.56 53 8 aspherical 4.733 0.083 9 Standard surface 7.495 1.999 1.44 70 10 Standard surface -11.437 0.048 11 aspherical 12.435 1.990 1.68 18.7 12 aspherical 3.318 0.511 13 aspherical 6.384 4 1.54 52 14 aspherical -2.594 -0.194 15 Standard surface INF 0.2 16 aspherical 4.210 0.658 1.62 57 17 aspherical 2.115 4.795 18 Standard surface INF 0.6 1.52 64.2 19 Standard surface INF 0.015 20 IMX INF
[0077] The surface numbers in Table 2 are assigned according to the surface sequence of each lens. "STO" represents the aperture stop of the lens. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "INF" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. nd represents the refractive index of the material, specifically the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air and the refractive index is 1. Vd represents the Abbe number, specifically the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air.
[0078] Table 3 Aspherical coefficients of a fixed-focus lens
[0079]
[0080] The K values in Table 3 represent the numerical values of the best-fit conic coefficients for the aspheric surface. The conic coefficients of the aspheric surface can be defined using the following aspheric formula, but are not limited to the following representations:
[0081]
[0082] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th and 16th order terms of the aspherical polynomial.
[0083] Wherein, "-2.995676E-003" represents -2.995676 * 10 -3 All other coefficients are represented in this way.
[0084] Based on the above parameter limitations, the optical parameters that the fixed-focus lens in Embodiment 1 of this utility model can achieve are as follows:
[0085] Table 4 Specific parameters for this embodiment
[0086] Image plane size (mm) Φ6.6 Focal length (mm) 7.439 F / # 1.31 Total lens length (mm) 20.584 band 436nm-656nm
[0087] Figure 2 This is a schematic diagram of field curvature distortion of a fixed-focus lens according to Embodiment 1 of this utility model. In the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents meridion and S represents arc distortion. Figure 2 As can be seen, the field curvature of the lens provided in this embodiment is effectively controlled at different wavelengths (436nm, 486nm, 546nm, 587nm, and 656nm, respectively), meaning that the difference in image quality between the center and the periphery is small during imaging. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit. Figure 2 As can be seen, the lens distortion provided in this embodiment is less than 5%, which results in low distortion and good imaging effect.
[0088] Figure 3 This is a Ray Fan diagram of a fixed-focus lens provided in Embodiment 1 of this utility model. The Ray Fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all light rays converge at the same point on the image plane. The interval corresponding to the vertical axis of the curve is the maximum dispersion range of the beam on the ideal image plane. The Ray Fan diagram can reflect not only monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 3 It can be seen that the system closely approximates the horizontal axis at each wavelength (436nm, 486nm, 546nm, 587nm and 656nm) under each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.
[0089] Figure 4 This is a schematic diagram of the transverse chromatic aberration of a fixed-focus lens according to Embodiment 1 of this utility model. The vertical direction represents the normalization of the field of view, and 0 indicates that it is on the optical axis. The dominant wavelength is 546nm, and the horizontal direction represents the offset relative to the dominant wavelength, with the unit being micrometers (μm). Figure 4 It can be seen that the chromatic aberration along the vertical axis is well controlled at different wavelengths, indicating that the chromatic aberration along the vertical axis of this fixed-focus lens is well controlled and can meet the requirements of wide-spectrum applications.
[0090] In summary, the fixed-focus lens provided in Embodiment 1 of this utility model includes seven lenses with optical power. By reasonably setting the optical power distribution method, optical power parameters, material surface type, concavity and convexity, as well as parameters such as refractive index and Abbe number, a fixed-focus lens with a large aperture, small size and clear imaging is designed.
[0091] Example 2
[0092] Figure 5 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of this utility model, as shown below. Figure 5 As shown, the fixed-focus lens provided in Embodiment 2 of this utility model includes a first lens 101, a second lens 102, an aperture stop STO, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, and a seventh lens 107 arranged sequentially along the optical axis from the object plane to the image plane; the first lens 101 is a negative power lens, the second lens 102 is a positive power lens, the third lens 103 is a positive power lens, the fourth lens 104 is a positive power lens, the fifth lens 105 is a negative power lens, the sixth lens 106 is a positive power lens, and the seventh lens 107 is a negative power lens; furthermore, the object-side surface of the second lens 102 is concave, and the image-side surface is convex; the object-side surface of the third lens 103 is convex, and the image-side surface is concave.
[0093] The lens setup is the same as in Embodiment 1, and will not be repeated here.
[0094] As another feasible implementation method, the specific parameters of the fixed-focus lens are explained below.
[0095] Table 5. Optical design values for a fixed-focus lens in Example 2.
[0096]
[0097] Table 6 Design values of optical physical parameters for a fixed-focus lens
[0098] Face number Surface type radius of curvature thickness Materials (nd) Materials (vd) 1 aspherical 4.023 0.975 1.51 50 2 aspherical 2.504 2.008 3 Standard surface INF 0.863 4 aspherical -5.175 1.496 1.65 25 5 aspherical -5.094 0.019 6 STO INF 0.138 7 aspherical 4.423 0.720 1.58 65.0 8 aspherical 4.711 0.460 9 Standard surface 7.062 3.697 1.46 70 10 Standard surface -13.202 0.029 11 aspherical 22.962 1.737 1.63 25 12 aspherical 3..550 0.628 13 aspherical 6.452 2.817 1.53 55.1 14 aspherical -4.071 -0.194 15 Standard surface INF 0.300 16 aspherical 5.366 0.884 1.66 22.5 17 aspherical 3.935 4.576 18 Standard surface INF 0.600 1.52 64.2 19 Standard surface INF 0.015 20 IMX INF
[0099] The surface numbers in Table 6 are assigned according to the surface sequence of each lens. "STO" represents the aperture stop of the lens. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "INF" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. nd represents the refractive index of the material, specifically the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air and the refractive index is 1. Vd represents the Abbe number, specifically the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air.
[0100] Table 7 Aspherical coefficients of a fixed-focus lens
[0101]
[0102] The K values in Table 7 represent the numerical values of the best-fit conic coefficients for the aspheric surface. The conic coefficients of the aspheric surface can be defined using the following aspheric formula, but are not limited to the following representations:
[0103]
[0104] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th and 16th order terms of the aspherical polynomial.
[0105] Wherein, "-2.729106E-003" represents -2.729106 * 10 -3 All other coefficients are represented in this way.
[0106] Based on the above parameter limitations, the optical parameters that the fixed-focus lens in Embodiment 2 of this utility model can achieve are as follows:
[0107] Table 8 Specific parameters for this embodiment
[0108] Image plane size (mm) Φ7.0 Focal length (mm) 7.001 F / # 1.29 Total lens length (mm) 21.768 band 436nm-656nm
[0109] Figure 6 This is a schematic diagram of field curvature distortion of a fixed-focus lens according to Embodiment 2 of this utility model. In the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents meridion and S represents arc distortion. Figure 6 As can be seen, the field curvature of the lens provided in this embodiment is effectively controlled at different wavelengths (436nm, 486nm, 546nm, 587nm, and 656nm, respectively), meaning that the difference in image quality between the center and the periphery is small during imaging. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit. Figure 6 As can be seen, the lens distortion provided in this embodiment is less than 5%, which results in low distortion and good imaging effect.
[0110] Figure 7 This is a Ray Fan diagram of a fixed-focus lens provided in Embodiment 2 of this utility model. The Ray Fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all light rays converge at the same point on the image plane. The interval corresponding to the vertical axis of the curve is the maximum dispersion range of the beam on the ideal image plane. The Ray Fan diagram can reflect not only monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 7It can be seen that the system closely approximates the horizontal axis at each wavelength (436nm, 486nm, 546nm, 587nm and 656nm) under each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.
[0111] Figure 8 This is a schematic diagram of the transverse chromatic aberration of a fixed-focus lens according to Embodiment 2 of this utility model. The vertical direction represents the normalization of the field of view, and 0 indicates that it is on the optical axis. The dominant wavelength is 546nm, and the horizontal direction represents the offset relative to the dominant wavelength, with the unit being micrometers (μm). Figure 8 It can be seen that the chromatic aberration along the vertical axis is well controlled at different wavelengths, indicating that the chromatic aberration along the vertical axis of this fixed-focus lens is well controlled and can meet the requirements of wide-spectrum applications.
[0112] In summary, the fixed-focus lens provided in Embodiment 2 of this utility model includes seven lenses with optical power. By reasonably setting the optical power distribution method, optical power parameters, material surface type, concavity and convexity, as well as parameters such as refractive index and Abbe number, a fixed-focus lens with a large aperture, small size and clear imaging is designed.
[0113] Example 3
[0114] Figure 9 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 3 of this utility model, as shown below. Figure 9 As shown, the fixed-focus lens provided in Embodiment 3 of this utility model includes a first lens 101, a second lens 102, an aperture stop 100, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, and a seventh lens 107 arranged sequentially along the optical axis from the object plane to the image plane; the first lens 101 is a negative power lens, the second lens 102 is a positive power lens, the third lens 103 is a positive power lens, the fourth lens 104 is a positive power lens, the fifth lens 105 is a negative power lens, the sixth lens 106 is a positive power lens, and the seventh lens 107 is a negative power lens; furthermore, the object-side surface of the second lens 102 is concave, and the image-side surface is convex; the object-side surface of the third lens 103 is convex, and the image-side surface is concave.
[0115] The lens setup is the same as in Embodiment 1, and will not be repeated here.
[0116] As another feasible implementation method, the specific parameters of the fixed-focus lens are explained below.
[0117] Table 9. Optical design values for a fixed-focus lens in Example 3.
[0118]
[0119] Table 10 Design values of optical physical parameters for a fixed-focus lens
[0120] Face number Surface type radius of curvature thickness Materials (nd) Materials (vd) 1 aspherical 4.016 0.932 1.60 25 2 aspherical 2.549 1.917 3 Standard surface INF 0.863 4 aspherical -5.422 1.078 1.67 18 5 aspherical -4.771 0 6 STO INF 1.000 7 aspherical 4.482 1.464 1.44 40 8 aspherical 4.602 0.911 9 Standard surface 9.884 3.500 1.78 70 10 Standard surface -10.927 0.030 11 aspherical 17.896 0.857 1.66 23 12 aspherical 3.311 0.424 13 aspherical 7.640 2.245 1.52 43.6 14 aspherical -5.702 -0.194 15 Standard surface INF 1.000 16 aspherical 6.077 0.600 1.58 50.2 17 aspherical 4.882 4.294 18 Standard surface INF 0.6 1.52 64.2 19 Standard surface INF 0.015 20 IMX INF
[0121] The surface numbers in Table 10 are assigned according to the surface sequence of each lens. "STO" represents the aperture stop of the lens. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "INF" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. nd represents the refractive index of the material, specifically the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air and the refractive index is 1. Vd represents the Abbe number, specifically the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air.
[0122] Table 11 Aspherical coefficients of a fixed-focus lens
[0123]
[0124] The K values in Table 11 represent the numerical values of the best-fit conic coefficients for the aspheric surface. The conic coefficients of the aspheric surface can be defined using the following aspheric formula, but are not limited to the following representations:
[0125]
[0126] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th and 16th order terms of the aspherical polynomial.
[0127] Wherein, "-2.960893E-003" represents -2.960893 * 10 -3 All other coefficients are represented in this way.
[0128] Based on the above parameter limitations, the optical parameters that the fixed-focus lens in Embodiment 3 of this utility model can achieve are as follows:
[0129] Table 12 Specific parameters for this embodiment
[0130] Image plane size (mm) Φ7.0 Focal length (mm) 7.482 F / # 1.301 Total lens length (mm) 21.535 band 436nm-656nm
[0131] Figure 10This is a schematic diagram of field curvature distortion of a fixed-focus lens according to Embodiment 3 of this utility model. In the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents meridion and S represents arc distortion. Figure 10 As can be seen, the field curvature of the lens provided in this embodiment is effectively controlled at different wavelengths (436nm, 486nm, 546nm, 587nm, and 656nm, respectively), meaning that the difference in image quality between the center and the periphery is small during imaging. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit. Figure 10 As can be seen, the lens distortion provided in this embodiment is less than 5%, which results in low distortion and good imaging effect.
[0132] Figure 11 This is a Ray Fan diagram of a fixed-focus lens provided in Embodiment 3 of this utility model. The Ray Fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all light rays converge at the same point on the image plane. The interval corresponding to the vertical axis of the curve is the maximum dispersion range of the beam on the ideal image plane. The Ray Fan diagram can reflect not only monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 11 It can be seen that the system closely approximates the horizontal axis at each wavelength (436nm, 486nm, 546nm, 587nm and 656nm) under each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.
[0133] Figure 12 This is a schematic diagram of the transverse chromatic aberration of a fixed-focus lens provided in Embodiment 3 of this utility model. The vertical direction represents the normalization of the field of view, and 0 indicates that it is on the optical axis. The dominant wavelength is 546nm, and the horizontal direction represents the offset relative to the dominant wavelength, with the unit being micrometers (μm). Figure 12 It can be seen that the chromatic aberration along the vertical axis is well controlled at different wavelengths, indicating that the chromatic aberration along the vertical axis of this fixed-focus lens is well controlled and can meet the requirements of wide-spectrum applications.
[0134] In summary, the fixed-focus lens provided in Embodiment 3 of this utility model includes seven lenses with optical power. By reasonably setting the optical power distribution method, optical power parameters, material surface type, concavity and convexity, as well as parameters such as refractive index and Abbe number, a fixed-focus lens with a large aperture, small size and clear imaging is designed.
[0135] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.
Claims
1. A fixed-focus lens, characterized in that, It includes a first lens, a second lens, an aperture stop, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the object plane to the image plane; The first lens is a negative power lens, the second lens is a positive power lens, the third lens is a positive power lens, the fourth lens is a positive power lens, the fifth lens is a negative power lens, the sixth lens is a positive power lens, and the seventh lens is a negative power lens. Furthermore, the object-side surface of the second lens is concave, and the image-side surface is convex; the object-side surface of the third lens is convex, and the image-side surface is concave.
2. The fixed-focus lens according to claim 1, characterized in that, The object-side surface of the first lens is convex, and the image-side surface is concave. The object-side surface of the fourth lens is convex, and the image-side surface is also convex. The object-side surface of the fifth lens is convex, and the image-side surface is concave. The object-side surface of the sixth lens is convex, and the image-side surface is also convex. The object-side surface of the seventh lens is convex, and the image-side surface is concave.
3. The fixed-focus lens according to claim 1, characterized in that, The optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the fourth lens is φ4, the optical power of the fifth lens is φ5, the optical power of the sixth lens is φ6, the optical power of the seventh lens is φ7, and the optical power of the fixed-focus lens is φ. Among them, -2.372≤φ1 / φ≤-2.026; 4.685≤φ2 / φ≤8.568; 9.239≤φ3 / φ≤10.917; 0.957≤φ4 / φ≤1.508;-0.982≤φ5 / φ≤-0.833;0.546≤φ6 / φ≤0.884;-6.981≤φ7 / φ≤-1.044; 4. The fixed-focus lens according to claim 1, characterized in that, The refractive index of the second lens is Nd2, and the Abbe number of the second lens is Vd2; the refractive index of the fourth lens is Nd4; the refractive index of the fifth lens is Nd5, and the Abbe number of the fifth lens is Vd5; Wherein, 1.65≤Nd2≤1.68, 18≤Vd2≤25; 1.44≤Nd4≤1.78; 1.63≤Nd5≤1.68、18.7≤Vd5≤25。 5. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens has a back focal length of BFL and an optical length of TTL. Among them, BFL / TTL≥0.
228.
6. The fixed-focus lens according to claim 1, characterized in that, The focal length of the fixed-focus lens is EFL, and the total optical length is TTL; Wherein, 0.321≤EFL / TTL≤0.
357.
7. The fixed-focus lens according to claim 1, characterized in that, The aperture number of the fixed-focus lens is F#; Where F#≤1.
31.
8. The fixed-focus lens according to claim 1, characterized in that, The optical assembly of the fixed-focus lens is TTL; Among them, TTL≤21.764mm.
9. The fixed-focus lens according to claim 1, characterized in that, The first lens, the second lens, the third lens, the fifth lens, the sixth lens, and the seventh lens are all plastic aspherical lenses; The fourth lens is a glass spherical lens.
10. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens also includes a filter; The filter is disposed in the optical path between the seventh lens and the image plane.