A fixed-focus lens

Abstract

An embodiment of the present invention discloses a fixed-focus lens, comprising: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence from an object plane to an image plane along an optical axis; the first lens has a negative optical power, the second lens has a positive optical power, the third lens has a negative optical power, the fourth lens has a positive optical power, the fifth lens has a positive optical power, the sixth lens has a negative optical power, and the seventh lens has a positive optical power; the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the optical system is f; wherein, -1.91 < f1 / f < -1.10, f2 / f > 1.8, f3 / f > -3.40, 1.70 < f4 / f < 2.63, 1.78 < f5 / f < 3.20, -1.88 < f6 / f < -1.01, 1.16 < f7 / f < 2.33. On the premise of ensuring a large light transmittance and low cost of the fixed-focus lens, the imaging quality is improved to meet the monitoring requirements under low illumination conditions.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of optical devices, and in particular to a fixed-focus lens. Background Art

[0002] The current solution for nighttime shooting of security cameras is dual-band confocal technology, that is, when there is sufficient light during the day, the camera adopts the visible light receiving mode; when in a dim light environment at night, the camera adopts the mode of receiving both visible light and infrared (850nm) for monitoring to ensure a greater amount of light entering; in order to achieve this function, the lens is required to have the characteristics of the visible light band and the infrared band being confocal, that is, the offset of the focus of visible light and infrared light is within the focal depth range of infrared light. At night and dusk, greater light transmission means better shooting effects. The current mainstream lens aperture is F2.0, and the first lens is mostly made of plastic, which cannot fully meet customers' requirements for lens appearance. At the same time, many security cameras will have purple fringing during use, that is, the image quality at short wavelengths is poor, resulting in poor shooting effects.

[0003] Therefore, it is necessary to develop a lens that is confocal day and night, has a large light throughput, a wide angle, and has good purple fringing. Summary of the invention

[0004] The embodiment of the present invention provides a fixed-focus lens, which ensures ultra-large light throughput, improves imaging quality, and meets monitoring requirements under low-illuminance conditions.

[0005] An embodiment of the present invention provides a fixed-focus lens, which includes: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence from an object plane to an image plane along an optical axis;

[0006] The first lens has negative optical power, the second lens has positive optical power, the third lens has negative optical power, the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power and the seventh lens has positive optical power;

[0007] The focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the optical system is f;

[0008] Among them, -1.91 <f1 / f<-1.10,f2 / f>1.8,f3 / f>-3.40,1.70<f4 / f<2.63,1.78<f5 / f<3.20,-1.88<f6 / f<-1.01,1.16<f7 / f<2.33。

[0009] Optionally, the first lens and the fourth lens are both glass spherical lenses, and the second lens, the third lens, the fifth lens, the sixth lens and the seventh lens are all plastic aspherical lenses.

[0010] Optionally, a surface of the lens adjacent to the object plane is an object-side surface, and a surface of the lens adjacent to the image plane is an image-side surface;

[0011] The object side surface of the first lens is convex toward the object plane, and the image side surface of the first lens is convex toward the object plane; the object side surface of the second lens is convex toward the image plane, and the image side surface of the second lens is convex toward the image plane; the object side surface of the fourth lens is convex toward the object plane, and the image side surface of the fourth lens is convex toward the image plane; the object side surface of the fifth lens is convex toward the object plane, and the image side surface of the fifth lens is convex toward the image plane; the object side surface of the sixth lens is convex toward the image plane, and the image side surface of the sixth lens is convex toward the object plane; the object side surface of the seventh lens is convex toward the object plane, and the image side surface of the seventh lens is convex toward the image plane.

[0012] Optionally, the refractive index of the second lens is n2; the refractive index of the third lens is n3; the refractive index of the fourth lens is n4; the refractive index of the fifth lens is n5; the refractive index of the sixth lens is n6; and the refractive index of the seventh lens is n7;

[0013] Among them, 1.57 <n2<1.68,1.50<n3<1.55,1.40<n4<1.64,1.50<n5<1.55,1.57<n6<1.68,1.50<n7<1.55。

[0014] Optionally, the Abbe number of the second lens is v2; the Abbe number of the third lens is v3; the Abbe number of the fourth lens is v4; the Abbe number of the fifth lens is v5; the Abbe number of the sixth lens is v6; and the Abbe number of the seventh lens is v7;

[0015] Among them, 19.1 <v2<30.4,55.0<v3<57.1,67.1<v4<97.0,55.0<v5<57.1,19.1<v6<30.4,55.0<v7<57.1。

[0016] Optionally, the fixed-focus lens further includes an aperture stop, and the aperture stop is arranged in the light path between the fourth lens and the fifth lens.

[0017] Optionally, the distance from the center of the optical axis of the image-side surface of the seventh lens to the image plane is BFL, and the distance from the object-side surface of the first lens to the image plane is TTL, wherein BFL / TTL≥0.17.

[0018] Optionally, the aperture number F of the fixed-focus lens satisfies 1.4≤F≤1.6.

[0019] Optionally, the field of view angle of the fixed-focus lens is FOV, where FOV≥144°.

[0020] The present invention provides a fixed-focus lens, and reasonably sets the number of lenses in the fixed-focus lens, the focal power of each lens, and the relative relationship between the focal lengths of each lens. Under the premise of low cost, the invention ensures the balance of the incident angles of the front and rear lens groups of the fixed-focus lens, reduces the sensitivity of the lens, improves the possibility of production, ensures that the fixed-focus lens has high resolution, can be used normally at -40°C to 80°C, has no purple fringes in the captured image, achieves ultra-large light throughput, improves the imaging quality, and meets the requirements of high-definition image quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, although the drawings described below are some specific embodiments of the present invention, for those skilled in the art, the basic concepts of the device structure, driving method and manufacturing method disclosed and suggested by the various embodiments of the present invention can be expanded and extended to other structures and drawings, and there is no doubt that these should be within the scope of the claims of the present invention.

[0022] Figure 1 A schematic structural diagram of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0023] Figure 2 A spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0024] Figure 3 A chromatic aberration curve diagram of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0025] Figure 4 A field curvature distortion curve diagram of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0026] Figure 5 A schematic structural diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0027] Figure 6 A spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0028] Figure 7 A chromatic aberration curve diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0029] Figure 8 A field curvature distortion curve diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0030] Fig. 9 A schematic structural diagram of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0031] Fig.10 A spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0032] Fig.11 A chromatic aberration curve diagram of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0033] Fig.12 A field curvature distortion curve diagram of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0034] Fig.13 A schematic structural diagram of a fixed-focus lens provided in Embodiment 4 of the present invention;

[0035] Fig.14 A spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 4 of the present invention;

[0036] Fig.15 A chromatic aberration curve diagram of a fixed-focus lens provided in Embodiment 4 of the present invention;

[0037] Fig.16 This is a field curvature distortion curve diagram of a fixed-focus lens provided in Embodiment 4 of the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described through implementation methods with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the basic concepts disclosed and suggested by the embodiments of the present invention, all other embodiments obtained by those skilled in the art are within the scope of protection of the present invention.

[0039] Embodiment 1

[0040] Figure 1 This is a structural schematic diagram of a fixed-focus lens provided in Embodiment 1 of the present invention, such as Figure 1 As shown, the embodiment of the present invention includes: 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 arranged in sequence from the object plane to the image plane along the optical axis;

[0041] The first lens 101 has negative power, the second lens 102 has positive power, the third lens 103 has negative power, the fourth lens 104 has positive power, the fifth lens 105 has positive power, the sixth lens 106 has negative power and the seventh lens 107 has positive power;

[0042] The focal length of the first lens 101 is f1, the focal length of the second lens 102 is f2, the focal length of the third lens 103 is f3, the focal length of the fourth lens 104 is f4, the focal length of the fifth lens 105 is f5, the focal length of the sixth lens 106 is f6, the focal length of the seventh lens 107 is f7, and the focal length of the optical system is f;

[0043] Among them, -1.91 <f1 / f<-1.10,f2 / f>1.8,f3 / f>-3.40,1.70<f4 / f<2.63,1.78<f5 / f<3.20,-1.88<f6 / f<-1.01,1.16<f7 / f<2.33。

[0044] Exemplarily, the focal length is equal to the difference between the convergence of the image-side light beam and the convergence of the object-side light beam, and it characterizes the ability of the optical system to deflect light. The larger the absolute value of the focal length, the stronger the ability to bend light, and the smaller the absolute value of the focal length, the weaker the ability to bend light. When the focal length is a positive number, the refraction of light is convergent; when the focal length is a negative number, the refraction of light is divergent. The focal length can be used to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can be used to characterize a certain lens, and can also be used to characterize a system formed by multiple lenses (i.e., a lens group). In the fixed-focus lens provided in this embodiment, each lens can be fixed to a lens barrel ( Figure 1 In the optical system (not shown), the first lens 101 is set as a negative focal lens for controlling the incident angle of light in the optical system; the second lens 102 is a positive focal length lens, and the third lens 103 is a negative focal length lens. The second lens 102 and the third lens 103 adopt a positive and negative focal length combination, which is conducive to sharing the focal length of the entire system, thereby facilitating the tolerance of the entire structure and reducing the sensitivity of assembly; the fourth lens 104 is a positive focal length lens for focusing the light beam; the third lens 103 and the sixth lens 106 are negative focal length lenses, and the second lens 102, the fifth lens 105 and the seventh lens 107 are all positive focal length lenses for correcting high-order aberrations, including field curvature, coma, astigmatism and other aberrations. The focal length of the entire fixed-focus lens is distributed according to a certain proportion to ensure the balance of the incident angles of the front and rear lens groups, so as to reduce the sensitivity of the lens and improve the possibility of production. At the same time, the focal lengths of the lenses are reasonably distributed to minimize the spherical aberration and field curvature of the imaging system, ensuring image quality on and off-axis. In addition, clear images of infrared light can be obtained without focusing when visible light is clearly focused.

[0045] Optionally, the first lens 101 and the fourth lens 104 are both glass spherical lenses, and 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.

[0046] Among them, the aspherical lens plays a role in correcting aberrations such as field curvature, astigmatism, spherical aberration, and coma. Since the cost of plastic lenses is much lower than that of glass lenses, the fixed-focus lens provided by the embodiment of the present invention has good image quality and low cost by setting 5 plastic aspherical lenses. And because the two types of materials have a mutual compensation effect, it can ensure that the fixed-focus lens can still be used normally in high and low temperature environments.

[0047] Optionally, the fixed-focus lens further includes an aperture, which is arranged in the light path between the fourth lens 104 and the fifth lens 105.

[0048] By arranging the aperture in the light path between the fourth lens 104 and the fifth lens 105 , the propagation direction of the light beam can be adjusted, and the incident angle of the light beam can be adjusted, which is beneficial to further improve the imaging quality.

[0049] Optionally, the surface of the lens adjacent to the object plane is the object-side surface, and the surface of the lens adjacent to the image plane is the image-side surface;

[0050] The object side surface of the first lens is convex toward the object plane, and the image side surface of the first lens is convex toward the object plane; the object side surface of the second lens is convex toward the image plane, and the image side surface of the second lens is convex toward the image plane; the object side surface of the fourth lens is convex toward the object plane, and the image side surface of the fourth lens is convex toward the image plane; the object side surface of the fifth lens is convex toward the object plane, and the image side surface of the fifth lens is convex toward the image plane; the object side surface of the sixth lens is convex toward the image plane, and the image side surface of the sixth lens is convex toward the object plane; the object side surface of the seventh lens is convex toward the object plane, and the image side surface of the seventh lens is convex toward the image plane.

[0051] Furthermore, by reasonably setting the surface shape of each lens, it is ensured that the focal power and focal length of each lens meet the requirements of the focal power and focal length in the above embodiment, and the structure of the entire fixed-focus lens can be kept compact.

[0052] Optionally, the refractive index of the second lens 102 is n2; the refractive index of the third lens 103 is n3; the refractive index of the fourth lens 104 is n4; the refractive index of the fifth lens 105 is n5; the refractive index of the sixth lens 106 is n6; and the refractive index of the seventh lens 107 is n7;

[0053] Among them, 1.57 <n2<1.68,1.50<n3<1.55,1.40<n4<1.64,1.50<n5<1.55,1.57<n6<1.68,1.50<n7<1.55。

[0054] Optionally, the Abbe number of the second lens 102 is v2; the Abbe number of the third lens 103 is v3; the Abbe number of the fourth lens 104 is v4; the Abbe number of the fifth lens 105 is v5; the Abbe number of the sixth lens 106 is v6; and the Abbe number of the seventh lens 107 is v7;

[0055] Among them, 19.1 <v2<30.4,55.0<v3<57.1,67.1<v4<97.0,55.0<v5<57.1,19.1<v6<30.4,55.0<v7<57.1。

[0056] Specifically, the refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium. It is mainly used to describe the 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 of the medium, the smaller the Abbe number; conversely, the milder the dispersion of the medium, the larger the Abbe number. In this way, by matching the refractive index and Abbe number of each lens in a fixed-focus lens, it is beneficial to achieve a miniaturized design of the fixed-focus lens; at the same time, it is beneficial to achieve higher pixel resolution and larger aperture.

[0057] Optionally, the distance from the center of the optical axis of the image-side surface of the seventh lens to the image plane is BFL, and the distance from the object-side surface of the first lens to the image plane is TTL, wherein BFL / TTL≥0.17.

[0058] The distance from the center of the optical axis of the image side surface of the seventh lens 107 to the image plane can be understood as the back focus of the fixed-focus lens. By reasonably setting the back focus distance of the fixed-focus lens, the entire fixed-focus lens can be kept compact.

[0059] Optionally, the aperture number F of the fixed-focus lens satisfies 1.4≤F≤1.6. The fixed-focus lens provided in the embodiment of the present invention is a large-aperture fixed-focus lens that meets ultra-large throughput and is suitable for monitoring requirements under low-light conditions.

[0060] Optionally, the field of view of the fixed-focus lens is FOV, where FOV ≥ 144°.

[0061] The fixed-focus lens provided in the embodiment of the present invention is a fixed-focus lens with an ultra-large field of view angle, which meets the requirement of a large field of view.

[0062] For example, Table 1 describes in detail the specific setting parameters of each lens in the fixed-focus lens provided in Example 1 of the present invention in a feasible implementation manner. The fixed-focus lens in Table 1 corresponds to Figure 1 The fixed focus lens.

[0063] Table 1 Design values ​​of optical parameters of fixed focus lens

[0064]

[0065] Continue to refer Figure 1 , the fixed-focus lens provided in the embodiment of the present invention comprises 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 arranged in sequence from the object plane to the image plane along the optical axis. Table 1 shows the optical physical parameters such as the radius of curvature, thickness and material of each lens in the fixed-focus lens provided in the embodiment. Among them, the surface number is numbered according to the surface order of each lens, for example, "1" represents the object surface of the first lens 101, "2" represents the image surface of the first lens 101, "STO / 9" represents the object surface of the fifth lens 105, "10" represents the image surface of the fifth lens 105, and so on; the radius of curvature represents the curvature of the 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; the thickness represents the central axial distance from the current surface to the next surface, and the units of the radius of curvature and thickness are both millimeters (mm).

[0066] On the basis of the above implementation, optionally, the first lens 101 and the fourth lens 104 are both glass spherical lenses, and 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 fixed-focus lens provided in the embodiment of the present invention also includes an aperture (STO), and the propagation direction of the light beam can be adjusted by adding an aperture, which is beneficial to improving the imaging quality. The aperture can be located in the optical path between the fourth lens 104 and the fifth lens 105, but the embodiment of the present invention does not limit the specific setting position of the aperture. By setting the aperture at a suitable position, it is helpful to improve the relative illumination.

[0067] The aspherical surface shape equation Z of the second lens 102, the third lens 103, the fifth lens 105, the sixth lens 106 and the seventh lens 107 satisfies:

[0068]

[0069] Wherein, Z is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of y along the optical axis; c = 1 / R, R represents the paraxial curvature radius of the mirror surface; K is the cone coefficient; A, B, C, D, E, and F are high-order aspheric coefficients, where the units of Z, R, and y are all mm.

[0070] Exemplarily, Table 2 describes in detail the aspheric surface parameters in the first embodiment in a feasible implementation manner.

[0071] Table 2 A design value of aspheric coefficient in fixed focus lens

[0072]

[0073] Among them, -2.1642E-03 means that the coefficient A of face number 3 is -2.1642E*10 -3 , and so on.

[0074] The fixed-focus lens of the first embodiment achieves the following technical indicators:

[0075] Focal length: f=3.3mm;

[0076] Aperture number: F=1.6;

[0077] Field of view: 2w ≥ 144.5° (image side 2η ≥ Φ7mm);

[0078] Resolution: Compatible with CCD or CMOS cameras with a resolution of up to 8 megapixels.

[0079] Figure 2 This is a spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 1 of the present invention, such as Figure 2 As shown, the spherical aberration of the fixed-focus lens at different wavelengths (0.486 μm, 0.588 μm, 0.656 μm, 0.850 μm and 0.436 μm) is within 0.05 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of the fixed-focus lens is very small. Therefore, it can be seen that the fixed-focus lens provided in the embodiment of the present invention can correct the aberration well.

[0080] Figure 3 This is a chromatic aberration curve diagram of a fixed-focus lens provided in Embodiment 1 of the present invention, such as Figure 3 As shown in the figure, the vertical direction represents the field of view, 0 represents the optical axis, and the vertical vertex represents the maximum field of view radius; the horizontal direction is the distance from the intersection of the shortest wavelength principal ray to the intersection of the longest wavelength principal ray on the image plane, in μm. Figure 3 It can be seen that vertical chromatic aberration is well corrected.

[0081] Figure 4 This is a field curvature distortion curve diagram of a fixed-focus lens provided in Embodiment 1 of the present invention, such as Figure 4 As shown, in the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, without unit; T represents the meridian, S represents the sagittal; Figure 4It can be seen that the fixed-focus lens provided in this embodiment is effectively controlled in field curvature from light with a wavelength of 436nm to light with a wavelength of 850nm, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the coordinate system on the right, the horizontal coordinate represents the size of the distortion, in units of %; the vertical coordinate represents the normalized image height, without units; Figure 4 It can be seen that the field curvature of the fixed-focus lens provided in this embodiment is well corrected, effectively improving the imaging quality.

[0082] In summary, the fixed-focus lens provided in this embodiment has the advantages of an ultra-large field of view, high-definition image quality and a small size under low-light conditions. It is designed with a 7-piece structure. At a low cost, it can achieve 8MP image quality requirements with the combination of different optical focal lengths. The glass-plastic hybrid structure can meet the usage requirements in an environment of -40℃-80℃.

[0083] Embodiment 2

[0084] Figure 5 A structural schematic diagram of a fixed-focus lens provided in Embodiment 2 of the present invention is as follows: Figure 5 As shown, the fixed-focus lens provided in the second embodiment of the present invention comprises: a first lens 201, a second lens 202, a third lens 203, a fourth lens 204, a fifth lens 205, a sixth lens 206 and a seventh lens 207 which are arranged in sequence from the object plane to the image plane along the optical axis;

[0085] The first lens 201 has negative optical power, the second lens 202 has positive optical power, the third lens 203 has negative optical power, the fourth lens 204 has positive optical power, the fifth lens 205 has positive optical power, the sixth lens 206 has negative optical power and the seventh lens 207 has positive optical power;

[0086] The focal length of the first lens 201 is f1, the focal length of the second lens 202 is f2, the focal length of the third lens 203 is f3, the focal length of the fourth lens 204 is f4, the focal length of the fifth lens 205 is f5, the focal length of the sixth lens 206 is f6, the focal length of the seventh lens 207 is f7, and the focal length of the optical system is f;

[0087] Among them, -1.91 <f1 / f<-1.10,f2 / f>1.8,f3 / f>-3.40,1.70<f4 / f<2.63,1.78<f5 / f<3.20,-1.88<f6 / f<-1.01,1.16<f7 / f<2.33。

[0088] The focal power, refractive index, Abbe number, surface shape, material of each lens and the setting of the aperture position of the fixed-focus lens are the same as those in the first embodiment and will not be described in detail here.

[0089] Table 3 describes in detail the specific setting parameters of each lens in the fixed-focus lens provided in Example 2 of the present invention in another feasible implementation manner. The black light lens in Table 3 corresponds to Figure 5 The fixed focus lens.

[0090] Table 3 Design values ​​of optical parameters of fixed focus lens

[0091]

[0092] Continue to refer Figure 5 The fixed-focus lens provided in the embodiment of the present invention includes a first lens 201, a second lens 202, a third lens 203, a fourth lens 204, a fifth lens 205, a sixth lens 206 and a seventh lens 207 arranged in sequence from the object plane to the image plane along the optical axis. Table 3 shows the optical physical parameters such as the curvature radius, thickness and material of each lens in the fixed-focus lens provided in the embodiment. Among them, the surface number is numbered according to the surface order of each lens, for example, "1" represents the object surface of the first lens 201, "2" represents the image surface of the first lens 201, "STO / 9" represents the object surface of the fifth lens 205, "10" represents the image surface of the fifth lens 205, and so on; the curvature radius represents the curvature degree of the 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; the thickness represents the central axial distance from the current surface to the next surface, and the units of the curvature radius and thickness are both millimeters (mm).

[0093] On the basis of the above implementation, optionally, the first lens 201 and the fourth lens 204 are both glass spherical lenses, and the second lens 202, the third lens 203, the fifth lens 205, the sixth lens 206 and the seventh lens 207 are all plastic aspherical lenses. The fixed-focus lens provided in the embodiment of the present invention also includes an aperture (STO), and the propagation direction of the light beam can be adjusted by adding an aperture, which is beneficial to improving the imaging quality. The aperture can be located in the light path between the fourth lens 204 and the fifth lens 205, but the embodiment of the present invention does not limit the specific setting position of the aperture. By setting the aperture at a suitable position, it is helpful to improve the relative illumination.

[0094] The aspherical surface shape equation Z of the second lens 202, the third lens 203, the fifth lens 205, the sixth lens 206 and the seventh lens 207 satisfies:

[0095]

[0096] Wherein, Z is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of y along the optical axis; c = 1 / R, R represents the paraxial curvature radius of the mirror surface; K is the cone coefficient; A, B, C, D, E, and F are high-order aspheric coefficients, where the units of Z, R, and y are all mm.

[0097] Exemplarily, Table 4 describes in detail the aspheric surface parameters in the second embodiment in a feasible implementation manner.

[0098] Table 4 A design value of aspheric coefficient in fixed focus lens

[0099]

[0100] Among them, -6.3366E-03 means that the coefficient A of face number 3 is -6.3366E*10 -3 , and so on.

[0101] The fixed-focus lens of the second embodiment achieves the following technical indicators:

[0102] Focal length: f=3.3mm;

[0103] Aperture number: F=1.6;

[0104] Field of view: 2w ≥ 144.3° (image side 2η ≥ Φ7mm);

[0105] Resolution: Compatible with CCD or CMOS cameras with a resolution of up to 8 megapixels.

[0106] Figure 6 This is a spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 2 of the present invention, such as Figure 6 As shown, the spherical aberration of the fixed-focus lens at different wavelengths (0.486 μm, 0.588 μm, 0.656 μm, 0.850 μm and 0.436 μm) is within 0.05 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of the fixed-focus lens is very small. Therefore, it can be seen that the fixed-focus lens provided in the embodiment of the present invention can correct the aberration well.

[0107] Figure 7 This is a chromatic aberration curve diagram of a fixed-focus lens provided in Embodiment 2 of the present invention, such as Figure 7 As shown in the figure, the vertical direction represents the field of view, 0 represents the optical axis, and the vertical vertex represents the maximum field of view radius; the horizontal direction is the distance from the intersection of the shortest wavelength principal ray to the intersection of the longest wavelength principal ray on the image plane, in μm. Figure 7 It can be seen that vertical chromatic aberration is well corrected.

[0108] Figure 8 This is a field curvature distortion curve diagram of a fixed-focus lens provided in Embodiment 2 of the present invention, such as Figure 8 As shown, in the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, without unit; T represents the meridian, S represents the sagittal; Figure 8It can be seen that the fixed-focus lens provided in this embodiment is effectively controlled in field curvature from light with a wavelength of 436nm to light with a wavelength of 850nm, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the coordinate system on the right, the horizontal coordinate represents the size of the distortion, in units of %; the vertical coordinate represents the normalized image height, without units; Figure 8 It can be seen that the field curvature of the fixed-focus lens provided in this embodiment is well corrected, effectively improving the imaging quality.

[0109] In summary, the fixed-focus lens provided in this embodiment has the advantages of an ultra-large field of view, high-definition image quality and a small size under low-light conditions. It is designed with a 7-piece structure. At a low cost, it can achieve 8MP image quality requirements with the combination of different optical focal lengths. The glass-plastic hybrid structure can meet the usage requirements in an environment of -40℃-80℃.

[0110] Embodiment 3

[0111] Fig. 9 A structural schematic diagram of a fixed-focus lens provided in Embodiment 3 of the present invention is as follows: Fig. 9 As shown, the fixed-focus lens provided in Embodiment 3 of the present invention comprises: a first lens 301, a second lens 302, a third lens 303, a fourth lens 304, a fifth lens 305, a sixth lens 306 and a seventh lens 307 arranged in sequence from the object plane to the image plane along the optical axis;

[0112] The first lens 301 has negative optical power, the second lens 302 has positive optical power, the third lens 303 has negative optical power, the fourth lens 304 has positive optical power, the fifth lens 305 has positive optical power, the sixth lens 306 has negative optical power and the seventh lens 307 has positive optical power;

[0113] The focal length of the first lens 301 is f1, the focal length of the second lens 302 is f2, the focal length of the third lens 303 is f3, the focal length of the fourth lens 304 is f4, the focal length of the fifth lens 305 is f5, the focal length of the sixth lens 306 is f6, the focal length of the seventh lens 307 is f7, and the focal length of the optical system is f;

[0114] Among them, -1.91 <f1 / f<-1.10,f2 / f>1.8,f3 / f>-3.40,1.70<f4 / f<2.63,1.78<f5 / f<3.20,-1.88<f6 / f<-1.01,1.16<f7 / f<2.33。

[0115] The focal power, refractive index, Abbe number, surface shape, material of each lens and the setting of the aperture position of the fixed-focus lens are the same as those in the first embodiment and will not be described in detail here.

[0116] Table 5 describes in detail the specific setting parameters of each lens in the fixed-focus lens provided in Example 3 of the present invention in another feasible implementation manner. The black light lens in Table 5 corresponds to Fig. 9 The fixed focus lens.

[0117] Table 5 Design values ​​of optical parameters of fixed focus lens

[0118]

[0119]

[0120] Continue to refer Fig. 9 , the fixed-focus lens provided in the embodiment of the present invention comprises a first lens 301, a second lens 302, a third lens 303, a fourth lens 304, a fifth lens 305, a sixth lens 306 and a seventh lens 307 arranged in sequence from the object plane to the image plane along the optical axis. Table 5 shows the optical physical parameters such as the radius of curvature, thickness and material of each lens in the fixed-focus lens provided in the embodiment. Among them, the surface number is numbered according to the surface order of each lens, for example, "1" represents the object surface of the first lens 301, "2" represents the image surface of the first lens 301, "STO / 9" represents the object surface of the fifth lens 305, "10" represents the image surface of the fifth lens 305, and so on; the radius of curvature represents the curvature of the 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; the thickness represents the central axial distance from the current surface to the next surface, and the units of the radius of curvature and thickness are both millimeters (mm).

[0121] On the basis of the above implementation, optionally, the first lens 301 and the fourth lens 304 are both glass spherical lenses, and the second lens 302, the third lens 303, the fifth lens 305, the sixth lens 306 and the seventh lens 307 are all plastic aspherical lenses. The fixed-focus lens provided in the embodiment of the present invention also includes an aperture (STO), and the propagation direction of the light beam can be adjusted by adding an aperture, which is beneficial to improving the imaging quality. The aperture can be located in the light path between the fourth lens 304 and the fifth lens 305, but the embodiment of the present invention does not limit the specific setting position of the aperture. By setting the aperture at a suitable position, it is helpful to improve the relative illumination.

[0122] The aspherical surface shape equation Z of the second lens 302, the third lens 303, the fifth lens 305, the sixth lens 306 and the seventh lens 307 satisfies:

[0123]

[0124] Wherein, Z is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of y along the optical axis; c = 1 / R, R represents the paraxial curvature radius of the mirror surface; K is the cone coefficient; A, B, C, D, E, and F are high-order aspheric coefficients, where the units of Z, R, and y are all mm.

[0125] Exemplarily, Table 6 describes in detail the aspheric surface parameters in the third embodiment in a feasible implementation manner.

[0126] Table 6 A design value of aspheric coefficient in fixed focus lens

[0127]

[0128] Among them, -2.4159E-03 means that the coefficient A of face number 3 is -2.4159E*10 -3 , and so on.

[0129] The fixed-focus lens of the third embodiment achieves the following technical indicators:

[0130] Focal length: f=3.3mm;

[0131] Aperture number: F=1.6;

[0132] Field of view: 2w ≥ 144.3° (image side 2η ≥ Φ7mm);

[0133] Resolution: Compatible with CCD or CMOS cameras with a resolution of up to 8 megapixels.

[0134] Fig.10 This is a spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 3 of the present invention, such as Fig.10 As shown, the spherical aberration of the fixed-focus lens at different wavelengths (0.486 μm, 0.588 μm, 0.656 μm, 0.850 μm and 0.436 μm) is within 0.05 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of the fixed-focus lens is very small. Therefore, it can be seen that the fixed-focus lens provided in the embodiment of the present invention can correct the aberration well.

[0135] Fig.11 This is a chromatic aberration curve diagram of a fixed-focus lens provided in Embodiment 3 of the present invention, such as Fig.11 As shown in the figure, the vertical direction represents the field of view, 0 represents the optical axis, and the vertical vertex represents the maximum field of view radius; the horizontal direction is the distance from the intersection of the shortest wavelength principal ray to the intersection of the longest wavelength principal ray on the image plane, in μm. Fig.11 It can be seen that vertical chromatic aberration is well corrected.

[0136] Fig.12This is a field curvature distortion curve diagram of a fixed-focus lens provided in Embodiment 3 of the present invention, such as Fig.12 As shown, in the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, without unit; T represents the meridian, S represents the sagittal; Fig.12 It can be seen that the fixed-focus lens provided in this embodiment is effectively controlled in field curvature from light with a wavelength of 436nm to light with a wavelength of 850nm, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the coordinate system on the right, the horizontal coordinate represents the size of the distortion, in units of %; the vertical coordinate represents the normalized image height, without units; Fig.12 It can be seen that the field curvature of the fixed-focus lens provided in this embodiment is well corrected, effectively improving the imaging quality.

[0137] In summary, the fixed-focus lens provided in this embodiment has the advantages of an ultra-large field of view, high-definition image quality and a small size under low-light conditions. It is designed with a 7-piece structure. At a low cost, it can achieve 8MP image quality requirements with the combination of different optical focal lengths. The glass-plastic hybrid structure can meet the usage requirements in an environment of -40℃-80℃.

[0138] Embodiment 4

[0139] Fig.13 A structural schematic diagram of a fixed-focus lens provided in a fourth embodiment of the present invention is shown in FIG. Fig.13 As shown, the fixed-focus lens provided in the fourth embodiment of the present invention comprises: a first lens 401, a second lens 402, a third lens 403, a fourth lens 404, a fifth lens 405, a sixth lens 406 and a seventh lens 407 arranged in sequence from the object plane to the image plane along the optical axis;

[0140] The first lens 401 has negative optical power, the second lens 402 has positive optical power, the third lens 403 has negative optical power, the fourth lens 404 has positive optical power, the fifth lens 405 has positive optical power, the sixth lens 406 has negative optical power and the seventh lens 407 has positive optical power;

[0141] The focal length of the first lens 401 is f1, the focal length of the second lens 402 is f2, the focal length of the third lens 403 is f3, the focal length of the fourth lens 404 is f4, the focal length of the fifth lens 405 is f5, the focal length of the sixth lens 406 is f6, the focal length of the seventh lens 407 is f7, and the focal length of the optical system is f;

[0142] Among them, -1.91 <f1 / f<-1.10,f2 / f>1.8,f3 / f>-3.40,1.70<f4 / f<2.63,1.78<f5 / f<3.20,-1.88<f6 / f<-1.01,1.16<f7 / f<2.33。

[0143] The focal power, refractive index, Abbe number, surface shape, material of each lens and the setting of the aperture position of the fixed-focus lens are the same as those in the first embodiment and will not be described in detail here.

[0144] Table 7 describes in detail the specific setting parameters of each lens in the fixed-focus lens provided in Example 4 of the present invention in another feasible implementation manner. The black light lens in Table 7 corresponds to Fig.13 The fixed focus lens.

[0145] Table 7 Design values ​​of optical parameters of fixed-focus lenses

[0146]

[0147] Continue to refer Fig.13 , the fixed-focus lens provided in the embodiment of the present invention includes a first lens 401, a second lens 402, a third lens 403, a fourth lens 404, a fifth lens 405, a sixth lens 406 and a seventh lens 407 arranged in sequence from the object plane to the image plane along the optical axis. Table 7 shows the optical physical parameters such as the radius of curvature, thickness and material of each lens in the fixed-focus lens provided in the embodiment. Among them, the surface number is numbered according to the surface order of each lens, for example, "1" represents the object surface of the first lens 401, "2" represents the image surface of the first lens 401, "STO / 9" represents the object surface of the fifth lens 405, "10" represents the image surface of the fifth lens 405, and so on; the radius of curvature represents the curvature of the 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; the thickness represents the central axial distance from the current surface to the next surface, and the units of the radius of curvature and thickness are both millimeters (mm).

[0148] On the basis of the above implementation, optionally, the first lens 401 and the fourth lens 404 are both glass spherical lenses, and the second lens 402, the third lens 403, the fifth lens 405, the sixth lens 406 and the seventh lens 407 are all plastic aspherical lenses. The fixed-focus lens provided in the embodiment of the present invention also includes an aperture (STO), and the propagation direction of the light beam can be adjusted by adding an aperture, which is beneficial to improving the imaging quality. The aperture can be located in the light path between the fourth lens 404 and the fifth lens 405, but the embodiment of the present invention does not limit the specific setting position of the aperture. By setting the aperture at a suitable position, it is helpful to improve the relative illumination.

[0149] The aspherical surface shape equation Z of the second lens 402, the third lens 403, the fifth lens 405, the sixth lens 406 and the seventh lens 407 satisfies:

[0150]

[0151] Wherein, Z is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of y along the optical axis; c = 1 / R, R represents the paraxial curvature radius of the mirror surface; K is the cone coefficient; A, B, C, D, E, and F are high-order aspheric coefficients, where the units of Z, R, and y are all mm.

[0152] Exemplarily, Table 8 describes in detail the aspheric surface parameters in the fourth embodiment in a feasible implementation manner.

[0153] Table 8 A design value of aspheric coefficient in fixed focus lens

[0154]

[0155]

[0156] Among them, -4.48E-03 means that the coefficient A of face number 3 is -4.48E*10 -3 , and so on.

[0157] The fixed-focus lens of the fourth embodiment achieves the following technical indicators:

[0158] Focal length: f=3.3mm;

[0159] Aperture number: F=1.4;

[0160] Field of view: 2w ≥ 144.7° (image side 2η ≥ Φ7mm);

[0161] Resolution: Compatible with CCD or CMOS cameras with a resolution of up to 8 megapixels.

[0162] Fig.14 This is a spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 4 of the present invention, such as Fig.14 As shown, the spherical aberration of the fixed-focus lens at different wavelengths (0.486 μm, 0.588 μm, 0.656 μm, 0.850 μm and 0.436 μm) is within 0.05 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of the fixed-focus lens is very small. Therefore, it can be seen that the fixed-focus lens provided in the embodiment of the present invention can correct the aberration well.

[0163] Fig.15 This is a chromatic aberration curve diagram of a fixed-focus lens provided in Embodiment 4 of the present invention, such as Fig.15 As shown in the figure, the vertical direction represents the field of view, 0 represents the optical axis, and the vertical vertex represents the maximum field of view radius; the horizontal direction is the distance from the intersection of the shortest wavelength principal ray to the intersection of the longest wavelength principal ray on the image plane, in μm. Fig.15 It can be seen that vertical chromatic aberration is well corrected.

[0164] Fig.16 This is a field curvature distortion curve diagram of a fixed-focus lens provided in Embodiment 4 of the present invention, such as Fig.16 As shown, in the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, without unit; T represents the meridian, S represents the sagittal; Fig.16 It can be seen that the fixed-focus lens provided in this embodiment is effectively controlled in field curvature from light with a wavelength of 436nm to light with a wavelength of 850nm, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the coordinate system on the right, the horizontal coordinate represents the size of the distortion, in units of %; the vertical coordinate represents the normalized image height, without units; Fig.16 It can be seen that the field curvature of the fixed-focus lens provided in this embodiment is well corrected, effectively improving the imaging quality.

[0165] In summary, the fixed-focus lens provided in this embodiment has the advantages of an ultra-large field of view, high-definition image quality and a small size under low-light conditions. It is designed with a 7-piece structure. At a low cost, it can achieve 8MP image quality requirements with the combination of different optical focal lengths. The glass-plastic hybrid structure can meet the usage requirements in an environment of -40℃-80℃.

[0166] Table 9 Summary of Example Parameters

[0167]

[0168] It can be seen from the embodiment parameters given in Table 9 that the first lens can be made of either a high refractive index material or a low refractive index material, so the refractive index and Abbe number of the first lens are not limited in range.

[0169] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A fixed-focus lens, characterized in that: include: A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens are arranged in sequence from the object plane to the image plane along the optical axis; The first lens has negative optical power, the second lens has positive optical power, the third lens has negative optical power, the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power and the seventh lens has positive optical power; The focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the optical system is f; Among them, -1.91 <f1 / f<-1.10,f2 / f>1.8,f3 / f>-3.40,1.70<f4 / f<2.63,1.78<f5 / f<3.20,-1.88<f6 / f<-1.01,1.16<f7 / f<2.33; The aperture number F of the fixed-focus lens satisfies 1.4≤F≤1.6; The field of view angle of the fixed-focus lens is FOV, wherein FOV≥144°.

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

3. The fixed-focus lens according to claim 1, characterized in that: The surface of the lens adjacent to the object plane is the object-side surface, and the surface of the lens adjacent to the image plane is the image-side surface; The object-side surface of the first lens is convex toward the object plane, and the image-side surface of the first lens is convex toward the object plane; The object-side surface of the second lens is convex toward the image plane, and the image-side surface of the second lens is convex toward the image plane; The object-side surface of the fourth lens is convex toward the object plane, and the image-side surface of the fourth lens is convex toward the image plane; The object-side surface of the fifth lens is convex toward the object plane, and the image-side surface of the fifth lens is convex toward the image plane; The object-side surface of the sixth lens is convex toward the image plane, and the image-side surface of the sixth lens is convex toward the object plane; The object-side surface of the seventh lens is convex toward the object plane, and the image-side surface of the seventh lens is convex toward the image plane.

4. The fixed-focus lens according to claim 1, characterized in that: The refractive index of the second lens is n2; the refractive index of the third lens is n3; the refractive index of the fourth lens is n4; the refractive index of the fifth lens is n5; the refractive index of the sixth lens is n6; and the refractive index of the seventh lens is n7; Among them, 1.57 <n2<1.68,1.50<n3<1.55,1.40<n4<1.64,1.50<n5<1.55,1.57<n6<1.68,1.50<n7<1.55。 5. The fixed-focus lens according to claim 1, wherein: The Abbe number of the second lens is v2; the Abbe number of the third lens is v3; the Abbe number of the fourth lens is v4; the Abbe number of the fifth lens is v5; the Abbe number of the sixth lens is v6; and the Abbe number of the seventh lens is v7; Among them, 19.1 <v2<30.4,55.0<v3<57.1,67.1<v4<97.0,55.0<v5<57.1,19.1<v6<30.4,55.0<v7<57.1。 6. The fixed-focus lens according to claim 1, wherein: The fixed-focus lens further includes a stop, which is disposed in an optical path between the fourth lens and the fifth lens.

7. The fixed-focus lens according to claim 1, wherein: The distance from the center of the optical axis of the image-side surface of the seventh lens to the image plane is BFL, and the distance from the object-side surface of the first lens to the image plane is TTL, wherein BFL / TTL≥0.17.

Images