Prime lens

Abstract

The prime lens comprises a front lens group, a diaphragm and a rear lens group which are sequentially arranged from an object side to an image side, the front lens group is sequentially provided with a first lens, a second lens and a third lens with negative focal power, negative focal power and positive focal power from the object side to the image side; the rear lens group is sequentially provided with a fourth lens, a fifth lens, a sixth lens and a seventh lens with positive focal power, negative focal power, positive focal power and positive focal power from the object side to the image side; wherein the fourth lens and the fifth lens are glued to form a doublet lens. The prime lens is composed of seven lens elements, the number of the lenses is reasonable, the structure is simple and compact, the focal power and the position of each lens element are reasonable, the environment adaptability is high, and the resolving power is high; due to the design of the large field angle and the large image height, the lens system has higher competitiveness in the market. The aperture number FNO of the prime lens is 2.50, the field angle is 138 degrees, the imaging height can be matched with a 1 / 1.8 inch chip, the total optical length is not larger than 24.0 mm, the optical distortion absolute value is smaller than 40%, and the requirement for ultra-high-definition imaging is met.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a fixed-focus lens. Background Art

[0002] With the continuous progress of the security monitoring industry, society has put forward higher and higher requirements for security. Ultra-high-definition lens systems with large field of view, large image height and good environmental adaptability are increasingly favored by the security market. However, the problem is that lenses with large field of view and large image height often contain many lenses, are large in size, and are expensive. In addition, a small number of lenses sacrifice some resolution in order to reduce costs. Summary of the invention

[0003] The present invention provides a fixed-focus lens, which adopts 7 glass-plastic lens elements, has a field of view of 138°, a total length of less than 24.0 mm, an absolute value of optical distortion of less than 40%, and an image height that can match an ultra-high-definition lens system of a 1 / 1.8″ chip.

[0004] To achieve the above object, an embodiment of the present invention provides a fixed-focus lens, comprising: a front lens group, an aperture, and a rear lens group arranged in sequence from the object side to the image side;

[0005] The front lens group is provided with a first lens with negative optical power, a second lens with negative optical power, and a third lens with positive optical power in sequence from the object side to the image side;

[0006] The rear lens group is provided with a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power and a seventh lens with positive optical power in sequence from the object side to the image side;

[0007] Wherein, the fourth lens and the fifth lens are glued together to form a double glued lens.

[0008] Optionally, the first lens is a glass spherical lens, the second lens is a plastic aspherical lens, the third lens is a glass spherical lens, the fourth lens is a glass spherical lens, the fifth lens is a glass spherical lens, the sixth lens is a plastic aspherical lens, and the seventh lens is a plastic aspherical lens.

[0009] Optionally, the first lens has a convex surface facing the object side, and a concave surface facing the image side, the second lens has a convex surface facing the object side, and a concave surface facing the image side, the third lens has a convex surface facing the object side, and a concave surface facing the image side, the fourth lens has a convex surface facing the object side, and a convex surface facing the image side, the fifth lens has a concave surface facing the object side, and a convex surface facing the image side, the sixth lens has a concave surface facing the object side in the paraxial region, and a convex surface facing the image side, and the seventh lens has a convex surface facing the object side in the paraxial region, and a concave surface facing the image side.

[0010] Optionally, the front lens group satisfies the following relationship:

[0011] The rear lens group satisfies the following relationship:

[0012] in, is the combined optical power of the front lens group, is the combined optical power of the rear lens group, is the optical power of the fixed-focus lens.

[0013] Optionally, the optical power of the first lens is and the focal length of the fixed-focus lens Satisfies the following relationship: The optical power of the second lens and the focal length of the fixed-focus lens Satisfies the following relationship: The focal power of the third lens and the focal length of the fixed-focus lens Satisfies the following relationship:

[0014] Optionally, the refractive index ND3 and the Abbe number VD3 of the third lens satisfy the following relationship: 1.75≤ND3≤1.88, 20.5≤VD3≤28.50.

[0015] Optionally, the optical power of the doublet lens is positive, and the optical power of the doublet lens is The focal length of the fixed focal length lens Satisfies the following relationship:

[0016] Optionally, the refractive index ND4 and the Abbe number VD4 of the fourth lens satisfy the following relationship: 1.55≤ND4≤1.65, 65.0≤VD4≤75.5; the refractive index ND5 and the Abbe number VD5 of the fifth lens satisfy the following relationship: 1.755≤ND5≤2.1, 20.5≤VD5≤32.5.

[0017] Optionally, the optical power of the sixth lens is The focal length of the fixed focal length lens Satisfies the following relationship:

[0018] The optical power of the seventh lens The focal length of the fixed focal length lens Satisfies the following relationship:

[0019] Optionally, the total optical length TTL of the fixed-focus lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: 8.15≤TTL / f≤8.955.

[0020] Optionally, an optical back focal length BFL of the fixed-focus lens and an effective focal length f of the fixed-focus lens satisfy the following relationship: 1.252≤BFL / f≤1.554.

[0021] The technical solution of the embodiment of the present invention is that the front lens group, the aperture and the rear lens group are sequentially arranged from the object side to the image side; the front lens group is sequentially arranged from the object side to the image side with a first lens with negative focal power, a second lens with negative focal power, and a third lens with positive focal power; the rear lens group is sequentially arranged from the object side to the image side with a fourth lens with positive focal power, a fifth lens with negative focal power, a sixth lens with positive focal power, and a seventh lens with positive focal power; wherein the fourth lens and the fifth lens are glued together to form a double glued lens. Furthermore, the fixed-focus lens is composed of 7 lens elements, the number of lenses is reasonable, the structure is simple and compact, the focal power and position of each lens element are reasonable, the environmental adaptability is strong, and the resolution is high; at the same time, the design of large field angle and large image height makes the lens system more competitive in the market. The fixed-focus lens has an FNO of 2.50, a field of view of 138°, an image height that can match a 1 / 1.8-inch chip, a total optical length of no more than 24.0mm, and an absolute value of optical distortion of less than 40%, meeting ultra-high-definition imaging requirements.

[0022] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 is a schematic structural diagram of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0025] Figure 2 is a schematic diagram of an axial aberration curve of the fixed-focus lens provided in Embodiment 1 of the present invention;

[0026] Figure 3 is a transverse light fan diagram of the fixed-focus lens provided in the first embodiment of the present invention;

[0027] Figure 4 is a field curvature distortion curve diagram of the fixed-focus lens proposed in Embodiment 1 of the present invention;

[0028] Figure 5 is a schematic structural diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0029] Figure 6 is a schematic diagram of an axial aberration curve of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0030] Figure 7 is a transverse light fan diagram of the fixed-focus lens provided in the second embodiment of the present invention;

[0031] Figure 8 is a field curvature distortion curve diagram of the fixed-focus lens proposed in Embodiment 2 of the present invention;

[0032] Fig. 9 is a schematic structural diagram of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0033] Fig.10 is a schematic diagram of an axial aberration curve of a fixed-focus lens proposed in Embodiment 3 of the present invention;

[0034] Fig.11 is a transverse light fan diagram of the fixed-focus lens provided in Embodiment 3 of the present invention;

[0035] Fig.12 4 is a field curvature distortion curve diagram of the fixed-focus lens proposed in Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0037] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0038] An embodiment of the present invention provides a fixed-focus lens, comprising: a front lens group, an aperture, and a rear lens group, which are arranged in sequence from the object side to the image side; the front lens group comprises a first lens with negative optical focal power, a second lens with negative optical focal power, and a third lens with positive optical focal power, which are arranged in sequence from the object side to the image side; the rear lens group comprises a fourth lens with positive optical focal power, a fifth lens with negative optical focal power, a sixth lens with positive optical focal power, and a seventh lens with positive optical focal power, which are arranged in sequence from the object side to the image side; wherein the fourth lens and the fifth lens are cemented to form a double cemented lens.

[0039] It should be noted that the fixed-focus lens also includes a flat glass and an image plane. The diaphragm of the fixed-focus lens is located between the third lens and the fourth lens; the flat glass is located on the side of the seventh lens image. The diaphragm is located between the third lens and the fourth lens. On the one hand, it can effectively reduce the aperture size of the front lens group and reduce the weight of the lens; on the other hand, reducing the aperture at the diaphragm position can increase the system FNO value and reduce the introduction of the system diaphragm aberration; the FNO value of the system in this embodiment is 2.5.

[0040] Among them, the front lens group uses three lens elements with a negative-negative-positive power. Reasonable adjustment of the power ratio of each element to the fixed-focus lens can better control the overall aberration of the front lens group. The rear lens group uses four lens elements with a positive-negative-positive-positive power. Reasonable adjustment of the power ratio of each element to the fixed-focus lens can better control the overall aberration of the rear lens group. The reasonable combination of the power of each lens is conducive to the mutual compensation of the power of each lens in the optical system and the realization of the design purpose of ultra-clear imaging.

[0041] In addition, the double-cemented lens is located after the system aperture, which is beneficial to correcting chromatic aberration and improving the imaging quality of the optical system; at the same time, it can also smoothly transmit light, reduce the tolerance sensitivity of the optical system, and improve the assembly yield of the optical system.

[0042] Optionally, the first lens is a glass spherical lens, the second lens is a plastic aspherical lens, the third lens is a glass spherical lens, the fourth lens is a glass spherical lens, the fifth lens is a glass spherical lens, the sixth lens is a plastic aspherical lens, and the seventh lens is a plastic aspherical lens.

[0043] Among them, by arranging glass elements in the first lens, the third lens, the fourth lens and the fifth lens, the fixed-focus lens can be ensured to have good adaptability to high and low temperature environments; there are many types of glass materials, and choosing materials with suitable dispersion parameters can reduce chromatic aberration. At the same time, the second lens, the sixth lens and the seventh lens are arranged as plastic aspherical lenses, which can effectively achieve the design effect of large image height and low distortion. Reasonable matching of lens materials, optical power, shape and position layout can realize the design of high-definition imaging lens system with large field of view and large image height.

[0044] Optionally, the first lens has a convex surface facing the object side, and a concave surface facing the image side, the second lens has a convex surface facing the object side, and a concave surface facing the image side, the third lens has a convex surface facing the object side, and a concave surface facing the image side, the fourth lens has a convex surface facing the object side, and a convex surface facing the image side, the fifth lens has a concave surface facing the object side, and a convex surface facing the image side, the sixth lens has a concave surface facing the object side in the paraxial region, and a convex surface facing the image side, and the seventh lens has a convex surface facing the object side in the paraxial region, and a concave surface facing the image side.

[0045] Among them, the object side of the first lens can be convex, and the image side can be concave. The first lens is designed as a meniscus-shaped negative lens with the convex surface facing the object side, which can allow as much field of view light as possible to enter the system, which is beneficial to improving the field of view angle of the optical system. The field of view angle of the fixed-focus lens is 138°. The object side of the second lens is convex, and the image side is concave. By setting the first lens and the second lens as similar convex-concave lenses, the optical distortion of the fixed-focus lens system can be effectively reduced. The object side of the third lens can be convex, and the image side can be concave. The third lens is designed as a convex-concave positive lens, which can effectively control the light to enter the rear of the optical system smoothly, reduce the spherical aberration of the optical system, and improve the imaging quality of the optical system. Setting the cemented lens material and reasonably setting its focal length is beneficial to balancing the chromatic aberration of the fixed-focus lens. In the paraxial region, the sixth lens has a concave surface facing the object side and a convex surface facing the image side. The use of this plastic aspherical lens can effectively control the trend of light, converge light, shorten the total optical length of the system, and make the system structure more compact. The seventh lens has a convex surface facing the object side and a concave surface facing the image side in the paraxial region. The plastic aspherical lens can effectively control the direction of light, so that the light enters the flat glass at a smaller deflection angle, which can effectively reduce the system tolerance sensitivity and reduce the risk of stray light at the flat glass.

[0046] Optionally, the front lens group satisfies the following relationship: The rear lens group satisfies the following relationship: in, is the combined optical power of the front lens group, is the combined optical power of the rear lens group, is the optical power of a fixed-focus lens.

[0047] Among them, the optical power of the front lens group and the rear lens group of the lens has a reasonable distribution ratio, which is beneficial to controlling the height of the incident light of the front lens group, reducing the front aperture, and thus reducing the weight; in addition, the reasonable optical power distribution of the front and rear groups can increase the image surface as much as possible while ensuring the illumination of the image surface, thereby achieving the design goal of large image height.

[0048] Optionally, the optical power of the first lens and the focal length of a fixed-focus lens Satisfies the following relationship: The focal length of the second lens and the focal length of a fixed-focus lens Satisfies the following relationship: The focal length of the third lens and the focal length of a fixed-focus lens Satisfies the following relationship: Therefore, the first lens is arranged in this way, so that light with a large field of view and a large aperture can enter the second lens with a smaller deflection angle. The second lens is arranged in this way, which can effectively control the trend of light, reduce the field curvature and spherical aberration of the optical system, and improve the image quality of the optical system. The third lens is arranged in this way, which is conducive to balancing the aberration of light in front of the aperture.

[0049] Optionally, the refractive index ND3 and the Abbe number VD3 of the third lens satisfy the following relationship: 1.75≤ND3≤1.88, 20.5≤VD3≤28.50. The third lens is arranged in this way, which is conducive to balancing aberrations, controlling light height, and miniaturizing the fixed-focus lens.

[0050] Optionally, the optical power of the doublet lens is positive, and the optical power of the doublet lens is Optical power of fixed focal length lens Satisfies the following relationship: Therefore, by setting the cemented lens material and reasonably setting its optical power, it is beneficial to balance the chromatic aberration of the lens system.

[0051] Optionally, the refractive index ND4 and the Abbe number VD4 of the fourth lens satisfy the following relationship: 1.55≤ND4≤1.65, 65.0≤VD4≤75.5; the refractive index ND5 and the Abbe number VD5 of the fifth lens satisfy the following relationship: 1.755≤ND5≤2.1, 20.5≤VD5≤32.5. The double cemented lens is located after the system aperture, which is conducive to correcting chromatic aberration and improving the imaging quality of the optical system; at the same time, it can also smoothly transmit light, reduce the tolerance sensitivity of the optical system, and improve the assembly yield of the optical system.

[0052] Optionally, the optical power of the sixth lens is Optical power of fixed focal length lens Satisfies the following relationship: The optical power of the seventh lens Optical power of fixed focal length lens Satisfies the following relationship: This is beneficial for controlling aberrations, reducing tolerance sensitivity, and improving image quality.

[0053] Optionally, the total optical length TTL of the fixed-focus lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: 8.15≤TTL / f≤8.955, which is conducive to achieving a small volume of the fixed-focus lens.

[0054] Optionally, the optical back focal length BFL of the fixed-focus lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: 1.252≤BFL / f≤1.554. The optical back focal length BFL is the distance from the image side of the last lens to the image plane. This is conducive to achieving a small size of the fixed-focus lens.

[0055] The technical solution of the embodiment of the present invention is that the front lens group, the aperture and the rear lens group are sequentially arranged from the object side to the image side; the front lens group is sequentially arranged from the object side to the image side with a first lens with negative focal power, a second lens with negative focal power, and a third lens with positive focal power; the rear lens group is sequentially arranged from the object side to the image side with a fourth lens with positive focal power, a fifth lens with negative focal power, a sixth lens with positive focal power, and a seventh lens with positive focal power; wherein the fourth lens and the fifth lens are glued together to form a double glued lens. Furthermore, the fixed-focus lens is composed of 7 lens elements, the number of lenses is reasonable, the structure is simple and compact, the focal power and position of each lens element are reasonable, the environmental adaptability is strong, and the resolution is high; at the same time, the design of large field angle and large image height makes the lens system more competitive in the market. The fixed-focus lens has an FNO of 2.50, a field of view of 138°, an image height that can match a 1 / 1.8-inch chip, a total optical length of no more than 24.0mm, and an absolute value of optical distortion of less than 40%, meeting ultra-high-definition imaging requirements.

[0056] The fixed-focus lens provided by the present invention is described below with reference to three specific embodiments.

[0057] The specific parameters in Example 1, Example 2 and Example 3 are shown in Table 1.

[0058] Table 1 Specific parameters of different embodiments

[0059]

[0060]

[0061] Embodiment 1

[0062] Figure 1 Schematic diagram of the structure of the fixed focus lens proposed in the first embodiment of the present invention. Figure 1As shown, the fixed-focus lens is provided with: a front lens group, an aperture STO, a rear lens group, a flat glass PL and an image plane IMA in sequence from the object side to the image side; the front lens group includes: a first lens L1 which is a glass spherical lens, the optical focal length of the first lens L1 is negative, the first lens L1 has a convex surface facing the object side, and a concave surface facing the image side; the second lens L2 is a plastic aspherical lens, the optical focal length of the second lens L2 is negative, the second lens L2 has a convex surface facing the object side, and a concave surface facing the image side; the third lens L3 is a glass spherical lens, the optical focal length of the third lens L3 is positive, the third lens L3 has a convex surface facing the object side, and a concave surface facing the image side; the rear lens group includes: a fourth lens L4 which is a glass spherical lens, the optical focal length of the fourth lens L4 is The fourth lens L4 is positive, and both surfaces of the fourth lens L4 are convex; the fifth lens L5 is a glass spherical lens, the optical focal length of the fifth lens L5 is negative, the side of the fifth lens L5 facing the object side is concave, and the side facing the image side is convex; wherein the fourth lens L4 and the fifth lens L5 are cemented into a cemented lens group; the sixth lens L6 is a plastic aspherical lens, the optical focal length of the sixth lens L6 is positive, and in the paraxial region, the side of the sixth lens L6 facing the object side is concave, and the side facing the image side is convex; the seventh lens L7 is a plastic aspherical lens, the optical focal length of the seventh lens L7 is positive, and in the paraxial region, the side of the seventh lens L7 facing the object side is convex, and the side facing the image side is concave; the aperture of the fixed-focus lens is located between the third lens L3 and the fourth lens L4; the flat glass is located on the image side of the seventh lens L7. From Figure 1 It can be seen that the structural composition of each element of the fixed-focus lens and the shape and position of each element are crucial for the fixed-focus lens. As can be seen from the figure, the optical system is composed of 7 optical lenses, and the flat glass is located on the side of the seventh lens L7 facing the image plane.

[0063] In this embodiment, the focal length f is 2.687 mm, the F# is 2.50, the field of view angle is DFOV=138°, and the total optical length TTL=23.82 mm; the optical physical parameters of the first lens L1 to the seventh lens L7 are shown in Table 2:

[0064] Table 2 Design values ​​of a fixed focus lens in the embodiment

[0065] Surface number Surface type Curvature radius (mm) Thickness(mm) (nd) / (vd) Semi-diameter (mm) k value S1 Standard surface 11.272 1.207 1.755 / 52.33 8.18 S2 Standard surface 6.217 3.236 5.72 S3 even aspherical surface 13.143 0.868 1.535 / 55.71 5.42 2.534 S4 even aspherical surface 2.178 3.863 3.28 -0.759 S5 Standard surface 4.843 2.994 1.847 / 23.79 2.50 S6 Standard surface 15.669 0.551 1.32 S7 STO INF 0.110 1.10 S8 Standard surface 10.444 2.088 1.569 / 71.30 1.21 S9 Standard surface -2.060 0.805 1.847 / 23.79 1.57 S10 Standard surface -8.388 0.611 2.07 S11 even aspherical surface -14.337 1.594 1.545 / 56.00 2.67 -56.674 S12 even aspherical surface -3.444 0.027 2.86 -1.352 S13 even aspherical surface 5.959 2.210 1.545 / 56.00 4.12 -10.524 S14 even aspherical surface 7.993 2.723 4.20 -10.306 S15 Standard surface INF 0.700 1.517 / 64.21 4.40 S16 Standard surface INF 0.230 4.45 IMA Standard surface INF 4.50

[0066] The surface numbers S1-S16 in Table 2 are numbered according to the surface order of each lens, "STO" represents the aperture of the lens; the radius of curvature represents the curvature of the corresponding lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side, wherein "INF" indicates that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the material between the current surface and the next surface to deflect light, and a space represents that the current position is air and the refractive index is 1; Table 3 shows the aspheric coefficient values ​​used in the current embodiment.

[0067] Table 3 Aspheric coefficients of a fixed focus lens in the embodiment

[0068] Surface number A B C D E F G S3 -6.224324E-04 -2.077141E-05 1.156034E-06 -1.247189E-08 -3.380465E-11 -1.358838E-11 2.876792E-13 S4 -2.007909E-04 -1.021393E-04 -1.137823E-05 -9.161778E-07 1.772079E-07 8.018972E-09 -1.161599E-09 S11 2.910614E-04 3.219524E-04 1.127582E-04 -1.798642E-05 7.428775E-07 9.309057E-08 -7.905998E-09 S12 -7.032426E-04 2.937878E-04 1.000302E-04 -1.078097E-05 7.728304E-07 -2.987933E-08 1.860063E-09 S13 1.698379E-03 -2.191510E-06 2.569641E-06 -4.832158E-07 1.491300E-08 1.242029E-09 -6.241724E-11 S14 -3.281613E-03 2.053940E-04 -3.815619E-06 -5.943216E-08 8.898509E-09 1.655852E-11 -2.190213E-11

[0069] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following representation method:

[0070]

[0071] Among them, z is the axial vector height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0072] Figure 2 Schematic diagram of the axial aberration curve of the fixed-focus lens proposed in Example 1 of the present invention. The vertical direction represents the normalization of the aperture, 0 represents the optical axis, and the vertical vertex represents the maximum pupil radius (the pupil radius is 0.5373mm); the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). Different linear curves in the figure represent different wavelengths of system imaging (wherein blue represents 436nm, green represents 486nm, red represents 546nm, yellow represents 587nm, and purple represents 656nm), as shown in FIG. Figure 2 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide spectrum applications.

[0073] Figure 3This is the lateral light fan diagram of the fixed-focus lens proposed in Example 1 of the present invention. The light fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the light beam aperture, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum dispersion range of the light beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberrations of different wavelengths (where blue represents 436nm, green represents 486nm, red represents 546nm, yellow represents 587nm, and purple represents 656nm), but also indicate the size of the vertical axis chromatic aberration. By Figure 3 It can be seen that each wavelength of the system in each field of view is well close to the horizontal axis, indicating that the vertical axis aberration of each wavelength of the system 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, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0074] Figure 4 : is a field curvature distortion curve diagram of the fixed focus lens proposed in the first embodiment of the present invention. In the left coordinate system of the figure, the horizontal coordinate represents the magnitude of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, and there is no unit; T represents the meridian, and S represents the sagittal; Figure 4 It can be seen that the fixed-focus lens provided in this embodiment is effectively controlled in terms of field curvature from light with a wavelength of 436nm to light with a wavelength of 656nm (wherein blue represents 436nm, green represents 486nm, red represents 546nm, yellow represents 587nm, and purple represents 656nm, the solid line in the figure represents the meridian, and the dotted line represents the sagittal), that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small (wherein, in the field curvature diagram on the left, the maximum field of view is 69.000 degrees, the sagittal field curvature = 0.0392mm, and the meridian field curvature = 0.1001mm). In the coordinate system on the right, the horizontal coordinate represents the size of the distortion, in %; the vertical coordinate represents the normalized image height, without units; Figure 4 It can be seen that the distortion of the lens provided in this embodiment (in the distortion diagram on the right, the maximum field of view is 69.000 degrees, and the maximum distortion = 36.0283%).

[0075] Embodiment 2

[0076] Figure 5 Schematic diagram of the structure of the fixed focus lens proposed in the second embodiment of the present invention. Figure 5 As shown, the fixed focus lens is provided with: a front lens group, an aperture STO, a rear lens group, a flat glass and an image plane in sequence from the object side to the image side; the front lens group includes a first lens L1, a second lens L2, and a third lens L3, and the rear lens group includes a fourth lens L4, a fifth lens L5, a sixth lens L6 and a seventh lens L7. The fourth lens L4 and the fifth lens L5 are cemented to form a double cemented lens.

[0077] In this embodiment, the focal length f is 2.766 mm, the F# is 2.50, the field of view angle is DFOV=138°, and the total optical length TTL=23.74 mm; the optical physical parameters of the first lens L1 to the seventh lens L7 are shown in Table 4.

[0078] Table 4 Design values ​​of the fixed focus lens of Example 2

[0079]

[0080]

[0081] The surface numbers S1-S16 in Table 4 are numbered according to the surface order of each lens, "STO" represents the aperture of the lens; the radius of curvature represents the degree of curvature of the corresponding lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side, wherein "INF" indicates that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the material between the current surface and the next surface to deflect light, and a space represents that the current position is air and the refractive index is 1; Table 5 shows the aspheric coefficient values ​​used in the embodiment.

[0082] Table 5 Aspheric coefficients of the fixed focus lens of Example 2

[0083] Surface number A B C D E F G S3 -8.833809E-04 -4.412333E-06 1.152751E-06 -1.966412E-08 -2.446208E-10 -3.244532E-12 1.537720E-13 S4 -1.777238E-03 -2.210310E-04 -7.323004E-06 -3.797248E-07 1.182774E-07 1.478108E-09 -7.917610E-10 S11 9.818958E-04 1.490264E-04 1.061164E-04 -1.336553E-05 7.530762E-07 4.987956E-08 -6.352613E-09 S12 -4.403582E-04 2.141760E-04 7.462790E-05 -7.106536E-06 7.174557E-07 -1.829413E-08 1.760949E-09 S13 -7.930322E-04 -5.656581E-05 2.153137E-06 -2.733968E-07 2.989908E-08 1.477676E-09 -1.377818E-10 S14 -3.344818E-03 7.956412E-05 -6.919384E-06 2.334964E-07 1.144831E-08 -4.821004E-10 -1.826953E-11

[0084] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following representation method:

[0085]

[0086] Among them, z is the axial vector height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0087] Figure 6 Schematic diagram of the axial aberration curve of the fixed-focus lens proposed in Example 2 of the present invention. The vertical direction represents the normalization of the aperture, 0 represents the optical axis, and the vertical vertex represents the maximum pupil radius (the pupil radius is 0.5533mm); the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). Different linear curves in the figure represent different wavelengths of system imaging (where blue represents 436nm, green represents 486nm, red represents 546nm, yellow represents 587nm, and purple represents 656nm), as shown in FIG. Figure 6It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide spectrum applications.

[0088] Figure 7 This is the lateral light fan diagram of the fixed-focus lens proposed in Example 2 of the present invention. The light fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the light beam aperture, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum dispersion range of the light beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberrations of different wavelengths (where blue represents 436nm, green represents 486nm, red represents 546nm, yellow represents 587nm, and purple represents 656nm), but also indicate the size of the vertical axis chromatic aberration. By Figure 7 It can be seen that each wavelength of the system in each field of view is well close to the horizontal axis, indicating that the vertical axis aberration of each wavelength of the system 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, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0089] Figure 8 : is a field curvature distortion curve diagram of the fixed focus lens proposed in the second embodiment of the present invention. In the left coordinate system of the figure, the horizontal coordinate represents the magnitude of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, and there is no unit; T represents the meridian, and S represents the sagittal; Figure 8 It can be seen that the fixed-focus lens provided in this embodiment is effectively controlled in terms of field curvature from light with a wavelength of 436nm to light with a wavelength of 656nm (wherein blue represents 436nm, green represents 486nm, red represents 546nm, yellow represents 587nm, and purple represents 656nm, the solid line in the figure represents the meridian, and the dotted line represents the sagittal), that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small (wherein, in the field curvature diagram on the left, the maximum field of view is 69.000 degrees, the sagittal field curvature = 0.0563mm, and the meridian field curvature = 0.0749mm). In the coordinate system on the right, the horizontal coordinate represents the size of the distortion, in %; the vertical coordinate represents the normalized image height, without units; Figure 8 It can be seen that the distortion of the lens provided in this embodiment (in the distortion diagram on the right, the maximum field of view is 69.000 degrees, and the maximum distortion = 38.1940%).

[0090] Embodiment 3

[0091] Fig. 9 Schematic diagram of the structure of the fixed focus lens proposed in the third embodiment of the present invention. Fig. 9As shown, the fixed focus lens is provided with: a front lens group, an aperture, a rear lens group, a flat glass and an image plane in order from the object side to the image side; the front lens group includes a first lens L1, a second lens L2, and a third lens L3, and the rear lens group includes a fourth lens L4, a fifth lens L5, a sixth lens L6 and a seventh lens L7. The fourth lens L4 and the fifth lens L5 are cemented to form a double cemented lens.

[0092] In this embodiment, the focal length f is 2.766 mm, the F# is 2.50, the field of view angle is DFOV=138°, and the total optical length TTL=23.74 mm; the optical physical parameters of the first lens L1 to the seventh lens L7 are shown in Table 6.

[0093] Table 6 Design values ​​of the fixed focus lens of Example 3

[0094]

[0095]

[0096] The surface numbers S1-S16 in Table 6 are numbered according to the surface order of each lens, "STO" represents the aperture of the lens; the radius of curvature represents the degree of curvature of the corresponding lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side, wherein "INF" indicates that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the material between the current surface and the next surface to deflect light, and a space represents that the current position is air and the refractive index is 1; Table 7 shows the aspheric coefficient values ​​used in the current embodiment.

[0097] Table 7 Aspheric coefficients of the fixed focus lens of Example 3

[0098] Surface number A B C D E F G S3 -8.833809E-04 -4.412333E-06 1.152751E-06 -1.966412E-08 -2.446208E-10 -3.244532E-12 1.537720E-13 S4 -1.777238E-03 -2.210310E-04 -7.323004E-06 -3.797248E-07 1.182774E-07 1.478108E-09 -7.917610E-10 S11 9.818958E-04 1.490264E-04 1.061164E-04 -1.336553E-05 7.530762E-07 4.987956E-08 -6.352613E-09 S12 -4.403582E-04 2.141760E-04 7.462790E-05 -7.106536E-06 7.174557E-07 -1.829413E-08 1.760949E-09 S13 -7.930322E-04 -5.656581E-05 2.153137E-06 -2.733968E-07 2.989908E-08 1.477676E-09 -1.377818E-10 S14 -3.344818E-03 7.956412E-05 -6.919384E-06 2.334964E-07 1.144831E-08 -4.821004E-10 -1.826953E-11

[0099] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following representation method:

[0100]

[0101] Among them, z is the axial vector height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0102] Fig.10Schematic diagram of the axial aberration curve of the fixed-focus lens proposed in the third embodiment of the present invention. The vertical direction represents the normalization of the aperture, 0 represents the optical axis, and the vertical vertex represents the maximum pupil radius (the pupil radius is 0.5533mm); the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). Different linear curves in the figure represent different wavelengths of system imaging (where blue represents 436nm, green represents 486nm, red represents 546nm, yellow represents 587nm, and purple represents 656nm), as shown in FIG. Fig.10 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide spectrum applications.

[0103] Fig.11 This is the light fan diagram of the fixed-focus lens proposed in Example 3 of the present invention. The light fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the light beam aperture, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum dispersion range of the light beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberrations of different wavelengths (where blue represents 436nm, green represents 486nm, red represents 546nm, yellow represents 587nm, and purple represents 656nm), but also indicate the size of the vertical axis chromatic aberration. By Fig.11 It can be seen that each wavelength of the system in each field of view is well close to the horizontal axis, indicating that the vertical axis aberration of each wavelength of the system 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, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0104] Fig.12 : is a field curvature distortion curve diagram of the fixed focus lens proposed in the third embodiment of the present invention. In the left coordinate system of the figure, the horizontal coordinate represents the magnitude of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, and there is no unit; T represents the meridian, and S represents the sagittal; Fig.12 It can be seen that the fixed-focus lens provided in this embodiment is effectively controlled in terms of field curvature from light with a wavelength of 436nm to light with a wavelength of 656nm (wherein blue represents 436nm, green represents 486nm, red represents 546nm, yellow represents 587nm, and purple represents 656nm, the solid line in the figure represents the meridian, and the dotted line represents the sagittal), that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small (wherein, in the field curvature diagram on the left, the maximum field of view is 69.000 degrees, the sagittal field curvature = 0.0559mm, and the meridian field curvature = 0.0716mm). In the coordinate system on the right, the horizontal coordinate represents the size of the distortion, in %; the vertical coordinate represents the normalized image height, without units; Fig.12 It can be seen that the distortion of the lens provided in this embodiment (in the distortion diagram on the right, the maximum field of view is 69.000 degrees, and the maximum distortion = 38.1959%).

[0105] It should be noted that the structure and optical focal length of each lens in Embodiments 1 to 3 can refer to the contents before Embodiment 1 in the specific embodiment mode, and thus, will not be described again in each specific embodiment.

[0106] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fixed-focus lens, characterized in that: include: A front lens group, an aperture, and a rear lens group are arranged in sequence from the object side to the image side; The front lens group is provided with a first lens with negative optical power, a second lens with negative optical power, and a third lens with positive optical power in sequence from the object side to the image side; The rear lens group is provided with a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power and a seventh lens with positive optical power in sequence from the object side to the image side; Wherein, the fourth lens and the fifth lens are glued together to form a double glued lens.

2. The fixed-focus lens according to claim 1, characterized in that: The first lens is a glass spherical lens, the second lens is a plastic aspherical lens, the third lens is a glass spherical lens, the fourth lens is a glass spherical lens, the fifth lens is a glass spherical lens, the sixth lens is a plastic aspherical lens, and the seventh lens is a plastic aspherical lens.

3. The fixed-focus lens according to claim 1 or 2, characterized in that: The first lens has a convex surface facing the object side, and a concave surface facing the image side; the second lens has a convex surface facing the object side, and a concave surface facing the image side; the third lens has a convex surface facing the object side, and a concave surface facing the image side; the fourth lens has a convex surface facing the object side, and a convex surface facing the image side; the fifth lens has a concave surface facing the object side, and a convex surface facing the image side; the sixth lens has a concave surface facing the object side in the paraxial region, and a convex surface facing the image side; the seventh lens has a convex surface facing the object side in the paraxial region, and a concave surface facing the image side.

4. The fixed-focus lens according to claim 1, characterized in that: The front lens group satisfies the following relationship: -0.135≤φ 前 / φ≤-0.003; The rear lens group satisfies the following relationship: 0.485≤φ 后 / φ≤0.525; Among them, φ 前 is the combined optical power of the front lens group, φ 后 is the combined optical power of the rear lens group, and φ is the optical power of the fixed-focus lens.

5. The fixed-focus lens according to claim 1, wherein: The focal power φ1 of the first lens and the focal power φ of the fixed-focus lens satisfy the following relationship: -0.245≤φ1 / φ≤-0.115; the focal power φ1 of the second lens and the focal length of the fixed-focus lens Satisfies the following relationship: The focal power of the third lens and the focal length of the fixed-focus lens Satisfies the following relationship:

6. The fixed-focus lens according to claim 1, wherein: The refractive index ND3 and the Abbe number VD3 of the third lens satisfy the following relationship: 1.75≤ND3≤1.88, 20.5≤VD3≤28.

50.

7. The fixed-focus lens according to claim 1, wherein: The optical power of the doublet lens is positive, and the optical power of the doublet lens is positive. The optical power φ of the fixed-focus lens satisfies the following relationship:

8. The fixed-focus lens according to claim 1, wherein: The refractive index ND4 and the Abbe number VD4 of the fourth lens satisfy the following relationship: 1.55≤ND4≤1.65, 65.0≤VD4≤75.5; the refractive index ND5 and the Abbe number VD5 of the fifth lens satisfy the following relationship: 1.755≤ND5≤2.1, 20.5≤VD5≤32.

5.

9. The fixed-focus lens according to claim 1, wherein: The focal length φ6 of the sixth lens is equal to the focal length of the fixed focus lens. Satisfies the following relationship: The optical power of the seventh lens The focal length of the fixed focal length lens Satisfies the following relationship:

10. The fixed-focus lens according to claim 1, wherein: The total optical length TTL of the fixed-focus lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: 8.15≤TTL / f≤8.

955.

11. The fixed-focus lens according to claim 1, wherein: The optical back focal length BFL of the fixed-focus lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: 1.252≤BFL / f≤1.554.

Images