Prime lens

Abstract

The prime lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens which are sequentially arranged from an object plane to an image plane along an optical axis, the first lens is a negative-focal-power lens, the second lens is a negative-focal-power lens, the third lens is a positive-focal-power lens, the fourth lens is a positive-focal-power lens or a negative-focal-power lens, the fifth lens is a positive-focal-power lens, the sixth lens is a negative-focal-power lens, and the seventh lens is a positive-focal-power lens. The focal power of the second lens is phi 2, the focal power of the third lens is phi 3, the focal power of the fourth lens is phi 4, the focal power of the fifth lens is phi 5, the focal power of the sixth lens is phi 6, the focal power of the prime lens is phi, and phi 2 / phi is larger than or equal to-0.76 and smaller than or equal to-0.48. 0.32 < = phi 3 / phi < = 0.98; -0.56 < = phi 4 / phi < = 0.90; 0.32 < = phi 5 / phi < = 1.21; phi 6 / phi is not less than-0.35 and not less than-1.18; 0.16 < = phi 7 / phi < = 0.74. According to the technical scheme of the embodiment of the utility model, the design of the wide-angle prime lens with total length and good imaging quality can be realized.

Description

Technical Field

[0001] This utility model relates to the field of optical device technology, and in particular to a fixed-focus lens. Background Technology

[0002] In contemporary society, with the increasing awareness of safety among the public, people have higher and higher requirements for doorbell lenses. Traditional doorbell lenses have a small field of view and a small monitoring range, which can no longer meet residents' needs for wide-area monitoring; in addition, as doors become thinner, the long overall length of traditional doorbell lenses makes them inconvenient to install. Therefore, it is essential to develop a wide-angle lens with a short overall length and good image quality. Utility Model Content

[0003] This invention provides a fixed-focus lens to achieve a wide-angle fixed-focus lens design with short total length and good image quality.

[0004] The fixed-focus lens provided in this embodiment of the utility model includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the object plane to the image plane;

[0005] The first lens is a negative power lens, the second lens is a negative power lens, the third lens is a positive power lens, the fourth lens is either a positive power lens or a negative power lens, the fifth lens is a positive power lens, the sixth lens is a negative power lens, and the seventh lens is a positive power lens.

[0006] The optical power of the second lens is Φ2, the optical power of the third lens is Φ3, the optical power of the fourth lens is Φ4, the optical power of the fifth lens is Φ5, the optical power of the sixth lens is Φ6, and the optical power of the fixed-focus lens is Φ. Where:

[0007] -0.76≤Φ2 / Φ≤-0.48;0.32≤Φ3 / Φ≤0.98;-0.56≤Φ4 / Φ≤0.90;

[0008] 0.32≤Φ5 / Φ≤1.21; -1.18≤Φ6 / Φ≤-0.35; 0.16≤Φ7 / Φ≤0.74.

[0009] Optionally, the fixed-focus lens includes two glass spherical lenses and five plastic aspherical lenses; wherein:

[0010] The first lens is a glass spherical lens;

[0011] The second, fifth, sixth, and seventh lenses are all plastic aspherical lenses;

[0012] The third lens is a glass spherical lens or a plastic aspherical lens;

[0013] The fourth lens is either a glass spherical lens with positive optical power or a plastic aspherical lens with negative optical power.

[0014] 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;

[0015] The object-side surface of the first lens convexes towards the object plane, and the image-side surface of the first lens is concave towards the image plane.

[0016] The object-side surface of the second lens is concave towards the object plane, and the image-side surface of the second lens is concave towards the image plane; or, the object-side surface of the second lens is concave towards the object plane, and the image-side surface of the second lens is convex towards the image plane.

[0017] The object-side surface of the third lens bulges towards the object plane, and the image-side surface of the third lens bulges towards the image plane.

[0018] The object-side surface of the fourth lens convexes towards the object plane, and the image-side surface of the fourth lens convexes towards the image plane; or, the object-side surface of the fourth lens is concave towards the object plane, and the image-side surface of the fourth lens convexes towards the image plane.

[0019] The object-side surface of the fifth lens convexes towards the object plane, and the image-side surface of the fifth lens convexes towards the image plane.

[0020] The object-side surface of the sixth lens is concave towards the object plane, and the image-side surface of the sixth lens is concave towards the image plane; or, the object-side surface of the sixth lens is concave towards the object plane, and the image-side surface of the sixth lens is convex towards the image plane.

[0021] The object-side surface of the seventh lens convexes towards the object plane, and the image-side surface of the seventh lens convexes towards the image plane.

[0022] Optionally, the refractive index of the first lens is Nd1, and the Abbe number of the first lens is Vd1; where:

[0023] 1.48<Nd1<1.93, 17.95<Vd1<70.87.

[0024] Optionally, the center thickness of the third lens is CT3, the center thickness of the fourth lens is CT4, and the distance from the center of the optical axis on the object side of the first lens to the image plane is TTL; where:

[0025] 0.05≤CT3 / TTL≤0.14, 0.02≤CT4 / TTL≤0.19.

[0026] Optionally, a prime lens may also include an aperture stop;

[0027] The aperture stop is located in the optical path between the third lens and the fourth lens.

[0028] Optionally, the fifth and sixth lenses are cemented together; or, the fifth and sixth lenses are supported by spacer gaskets.

[0029] Optionally, the distance from the center of the optical axis on the object side of the first lens to the image plane is TTL; where TTL ≤ 12.2 mm.

[0030] Optionally, the field of view of the fixed-focus lens is FOV; where: FOV≥170°.

[0031] The fixed-focus lens provided in this embodiment of the utility model, by using seven lenses and reasonably configuring the optical power of each lens, has the advantages of good image quality, large field of view, and short total length. It can be used as a doorbell lens to improve the user experience.

[0032] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 1 of this utility model;

[0035] Figure 2 This is a spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 1 of this utility model;

[0036] Figure 3 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of this utility model;

[0037] Figure 4 This is a spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 2 of this utility model;

[0038] Figure 5 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 3 of this utility model;

[0039] Figure 6 This is a spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 3 of this utility model. Detailed Implementation

[0040] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0041] Example 1

[0042] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 1 of this utility model, as shown below. Figure 1 As shown, the fixed-focus lens provided in Embodiment 1 of this utility model includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170 arranged sequentially along the optical axis from the object plane to the image plane; the first lens 110 is a negative power lens, the second lens 120 is a negative power lens, the third lens 130 is a positive power lens, the fourth lens 140 is either a positive or negative power lens, the fifth lens 150 is a positive power lens, the sixth lens 160 is a negative power lens, and the seventh lens 170 is a positive power lens; the optical power of the second lens 120 is Φ2, the optical power of the third lens 130 is Φ3, the optical power of the fourth lens 140 is Φ4, the optical power of the fifth lens 150 is Φ5, the optical power of the sixth lens 160 is Φ6, and the optical power of the fixed-focus lens is Φ, wherein:

[0043] -0.76≤Φ2 / Φ≤-0.48;0.32≤Φ3 / Φ≤0.98;-0.56≤Φ4 / Φ≤0.90;

[0044] 0.32≤Φ5 / Φ≤1.21; -1.18≤Φ6 / Φ≤-0.35; 0.16≤Φ7 / Φ≤0.74.

[0045] Specifically, optical power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light. The larger the absolute value of the optical power, the stronger the bending ability of light; the smaller the absolute value, the weaker the bending ability. When the optical power is positive, the refraction of light is converging; when the optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a system formed by multiple lenses (i.e., a lens group). In the fixed-focus lens provided in this embodiment, all lenses can be fixed within a single lens barrel (…). Figure 1 (Not shown in the text)

[0046] In this embodiment, by setting the first lens 110 as a negative optical power lens, it facilitates the smooth entry of object-side light into the imaging system, allowing light to enter the second lens 120 at a smaller incident angle, reducing the proportion of higher-order aberrations, and giving the lens a larger field of view. By setting the optical power Φ2 of the second lens 120, the optical power Φ3 of the third lens 130, and the optical power Φ4 of the fourth lens 140 to meet the above range, not only can light be effectively constricted, but it also facilitates the correction of system aberrations, thereby promoting image quality improvement. By setting the optical power Φ5 of the fifth lens 150, the optical power Φ6 of the sixth lens 160, and the optical power Φ7 of the seventh lens 170 to meet the above range, light can smoothly transition to the image plane, reducing aberrations and improving image quality while also reducing assembly tolerances and increasing production yield. Furthermore, by rationally configuring the optical power of each lens, it is also beneficial to reduce the overall length of the lens, facilitating miniaturization design.

[0047] In summary, the fixed-focus lens provided by this utility model embodiment, by using seven lenses and reasonably configuring the optical power of each lens, gives the fixed-focus lens advantages such as good image quality, large field of view, and short overall length, and can be used as a doorbell lens to improve the user experience.

[0048] Based on the above embodiments, optionally, the fixed-focus lens includes two glass spherical lenses and five plastic aspherical lenses.

[0049] Specifically, aspherical lenses are characterized by a continuous change in curvature from the center to the periphery. Unlike spherical lenses, which have a constant curvature from the center to the periphery, aspherical lenses have superior curvature radius characteristics, offering advantages in improving distortion and astigmatism. Using aspherical lenses can minimize aberrations that occur during image formation, thereby enhancing the lens's image quality. Spherical lenses, on the other hand, have a constant curvature from the center to the periphery, ensuring a simpler lens configuration.

[0050] Furthermore, the plastic aspherical lens can be made of various plastics known to those skilled in the art, and the glass spherical lens can be made of various types of glass known to those skilled in the art. This embodiment of the present invention will not elaborate on or limit these materials. Glass lenses have a lower coefficient of thermal expansion and better stability. When the ambient temperature of a fixed-focus lens varies significantly, it helps maintain the focal length of the fixed-focus lens. Plastic lenses are significantly cheaper than glass lenses, thus reducing the overall cost of a fixed-focus lens.

[0051] The fixed-focus lens provided in this embodiment adopts a structure that combines two glass spherical lenses and five plastic aspherical lenses. On the one hand, it can effectively control the cost of the fixed-focus lens and reduce the processing technology of the aspherical lenses. On the other hand, since the materials of each lens have a mutual compensation effect, it can ensure that the fixed-focus lens can still be used normally in high and low temperature environments.

[0052] As a possible implementation, the first lens 110 may be a glass spherical lens; the second lens 120, the fifth lens 150, the sixth lens 160 and the seventh lens 170 may all be plastic aspherical lenses; the third lens 130 may be a glass spherical lens or a plastic aspherical lens; and the fourth lens 140 may be a glass spherical lens with positive optical power or a plastic aspherical lens with negative optical power.

[0053] The surface of a lens adjacent to the object plane is defined as the object-side surface, and the surface of the lens adjacent to the image plane is defined as the image-side surface; for example... Figure 1 As shown, optionally, the object-side surface of the first lens 110 convexes towards the object plane, and the image-side surface of the first lens 110 is concave towards the image plane; the object-side surface of the second lens 120 is concave towards the object plane, and the image-side surface of the second lens 120 convexes towards the image plane; the object-side surface of the third lens 130 convexes towards the object plane, and the image-side surface of the third lens 130 convexes towards the image plane; the object-side surface of the fourth lens 140 convexes towards the object plane, and the image-side surface of the fourth lens 140 convexes towards the image plane; the object-side surface of the fifth lens 150 convexes towards the object plane, and the image-side surface of the fifth lens 150 convexes towards the image plane; the object-side surface of the sixth lens 160 is concave towards the object plane, and the image-side surface of the sixth lens 160 is concave towards the image plane; the object-side surface of the seventh lens 170 convexes towards the object plane, and the image-side surface of the seventh lens 170 convexes towards the image plane. Furthermore, in other embodiments, optionally, the object-side surface of the second lens 120 is concave towards the object plane, and the image-side surface of the second lens 120 is concave towards the image plane; the object-side surface of the fourth lens 140 is concave towards the object plane, and the image-side surface of the fourth lens 140 is convex towards the image plane; the object-side surface of the sixth lens 160 is concave towards the object plane, and the image-side surface of the sixth lens 160 is convex towards the image plane. This will be illustrated exemplarily later. By reasonably setting the surface shape of each lens, while ensuring that the optical power of each lens meets the optical power requirements of the above embodiments, it also ensures that the entire fixed-focus lens structure is compact and has high integration, which is beneficial for reducing the overall length of the lens.

[0054] Optionally, the refractive index of the first lens 110 is Nd1, and the Abbe number of the first lens 110 is Vd1; where: 1.48 < Nd1 < 1.93, 17.95 < Vd1 < 70.87.

[0055] The refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium, primarily used to describe a material's ability to refract light; different materials have different refractive indices. The Abbe number is an index used to represent the dispersion ability of a transparent medium; the more severe the dispersion, the smaller the Abbe number; conversely, the less severe the dispersion, the larger the Abbe number. By setting the refractive index and Abbe number of the first lens 110 to meet the above ranges, more light can enter the optical system, ensuring the lens has a wider field of view.

[0056] In this embodiment, the field of view of the fixed-focus lens is FOV; wherein: FOV≥170°.

[0057] Optionally, the center thickness of the third lens 130 is CT3, the center thickness of the fourth lens 140 is CT4, and the distance from the center of the optical axis on the object side of the first lens 110 to the image plane is TTL; wherein: 0.05≤CT3 / TTL≤0.14, 0.02≤CT4 / TTL≤0.19.

[0058] In this embodiment, the center thickness of the third lens 130 can be understood as its thickness along the optical axis, the center thickness of the fourth lens 140 can be understood as its thickness along the optical axis, and the distance from the center of the optical axis of the object-side surface of the first lens 110 to the image plane can be understood as the total optical length of the fixed-focus lens. By setting the center thicknesses of the third lens 130 and the fourth lens 140 to satisfy the aforementioned ranges with respect to the total optical length of the lens, the total length of the lens can be reduced, resulting in a lens with a short total length and small size. In this embodiment, TTL ≤ 12.2 mm.

[0059] like Figure 1 As shown, optionally, the fixed-focus lens also includes an aperture stop 180; the aperture stop 180 is located in the optical path between the third lens 130 and the fourth lens 140. By setting the aperture stop 180, the propagation direction of the light beam can be adjusted, which is beneficial to further improve the image quality.

[0060] like Figure 1 As shown, optionally, the fixed-focus lens may also include a filter 190, which is located in the optical path between the seventh lens 170 and the image plane, and can filter out infrared light during the day to improve the imaging effect.

[0061] Optionally, the fifth lens 150 and the sixth lens 160 are cemented together. This further reduces the size of the fixed-focus lens and improves integration. Additionally, in other embodiments, the fifth lens 150 and the sixth lens 160 can also be supported by spacer gaskets. Figure 1 The illustration only takes the bonding of the fifth lens 150 and the sixth lens 160 (by adhesive) as an example.

[0062] Based on the above embodiments, the aspherical surface of the aspherical lens satisfies the following:

[0063]

[0064] Where z represents the axial sagitta in the Z direction of the aspherical surface; r represents the distance from a point on the aspherical surface to the optical axis; c represents the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k represents the fitted conic coefficients; and A, B, C, D, E, F, and G represent the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order coefficients of the aspherical polynomial, respectively.

[0065] As a feasible implementation method, the optical physical parameters of each lens in a fixed-focus lens, such as surface type, radius of curvature, thickness, refractive index, Abbe number, and semi-diameter, are described below.

[0066] In Table 1 below, the surface numbers are assigned according to the order of the lenses. For example, surface number "S1" represents the object-side surface of the first lens, surface number "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture of a fixed-focus lens; "IMA" represents the image plane of the lens; the radius of curvature represents the curvature of the lens surface. A positive value indicates that the surface bends towards the object plane with the center closer to the image plane, while a negative value indicates that the surface bends towards the image plane with the center closer to the object plane; "Infinity" represents a plane with an infinite radius of curvature; the thickness represents the axial distance between the current surface and the next surface; the refractive index (Nd) represents the ability of the material between the current surface and the next surface to deflect light, with a blank space indicating that the current position is air and the refractive index is 1; the Abbe number (Vd) represents the dispersion characteristics of the material between the current surface and the next surface, with a blank space indicating that the current position is air; the half-aperture (half-diameter) represents the effective diameter of the lens; and the k-value represents the magnitude of the conic coefficient of the aspherical surface.

[0067] Table 1 Design values ​​for fixed-focus lenses

[0068]

[0069] The following describes a feasible implementation method, referring to Table 2, for data on the aspherical surface of the aspherical lens. The data for the fitted conic coefficient k are detailed in Table 1.

[0070] In Table 2, 8.560344E-03 indicates that the coefficient A of surface number S3 is 8.560344 * 10. -3 And so on.

[0071] Table 2. Design values ​​of parameters for various surfaces of aspherical lenses in fixed-focus lenses.

[0072]

[0073] The above scheme enables fixed-focus lenses to have the advantages of wide field of view, low cost, short total length, and good image quality, with a total optical length (TTL) of 11.92mm.

[0074] Furthermore, Figure 2 This is a spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 1 of this utility model. Figure 2 The vertical direction represents the normalized aperture, with 0 indicating it's on the optical axis, and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focal point, in millimeters (mm). For example... Figure 2 As shown, the spherical aberration of the fixed-focus lens provided in Embodiment 1 of this utility model is controlled within (-0.01mm, +0.01mm) at different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm, 0.656μm and 0.850μm). The curves of different wavelengths are relatively concentrated, indicating that the spherical aberration of the fixed-focus lens at each wavelength is well controlled, which can meet the requirements of wide spectrum applications.

[0075] Example 2

[0076] Figure 3 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of this utility model, as shown below. Figure 3 As shown, the fixed-focus lens provided in Embodiment 2 of this utility model includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170 arranged sequentially along the optical axis from the object plane to the image plane; the first lens 110 is a negative power lens, the second lens 120 is a negative power lens, the third lens 130 is a positive power lens, the fourth lens 140 is either a positive or negative power lens, the fifth lens 150 is a positive power lens, the sixth lens 160 is a negative power lens, and the seventh lens 170 is a positive power lens; the optical power of the second lens 120 is Φ2, the optical power of the third lens 130 is Φ3, the optical power of the fourth lens 140 is Φ4, the optical power of the fifth lens 150 is Φ5, the optical power of the sixth lens 160 is Φ6, and the optical power of the fixed-focus lens is Φ, wherein:

[0077] -0.76≤Φ2 / Φ≤-0.48;0.32≤Φ3 / Φ≤0.98;-0.56≤Φ4 / Φ≤0.90;

[0078] 0.32≤Φ5 / Φ≤1.21; -1.18≤Φ6 / Φ≤-0.35; 0.16≤Φ7 / Φ≤0.74.

[0079] The materials, surface shapes, and other optical physical parameters such as Abbe number of each lens are the same as in Embodiment 1, and will not be repeated here. Unlike Embodiment 1, in Embodiment 2, the fifth lens 150 and the sixth lens 160 are supported by spacer pads.

[0080] Table 3 details the specific settings parameters of each lens in the fixed-focus lens provided in Embodiment 2 of this utility model, using another feasible implementation method. The fixed-focus lens in Table 3 corresponds to... Figure 3 The fixed-focus lens shown.

[0081] In Table 3, the surface numbers are assigned according to the surface sequence of each lens. For example, surface number "S1" represents the object-side surface of the first lens, surface number "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture of a fixed-focus lens; "IMA" represents the image plane of the lens; the radius of curvature represents the curvature of the lens surface. A positive value indicates that the surface bends towards the object plane with the center closer to the image plane, while a negative value indicates that the surface bends towards the image plane with the center closer to the object plane; "Infinity" represents a plane with an infinite radius of curvature; the thickness represents the axial distance between the current surface and the next surface; the refractive index (Nd) represents the ability of the material between the current surface and the next surface to deflect light, with a blank space indicating that the current position is air and the refractive index is 1; the Abbe number (Vd) represents the dispersion characteristics of the material between the current surface and the next surface, with a blank space indicating that the current position is air; the half-aperture (half-diameter) represents the effective ray diameter of the lens; and the k-value represents the magnitude of the conic coefficient of the aspherical surface.

[0082] Table 3 Design Values ​​for Fixed-Focus Lenses

[0083]

[0084] The following describes a feasible implementation method, referring to Table 4, for data on the aspherical surface of the aspherical lens. The data for the fitted conic coefficient k are detailed in Table 3.

[0085] Table 4. Design values ​​of parameters for various surfaces of aspherical lenses in fixed-focus lenses.

[0086]

[0087] Where 1.070980E-02 indicates that the coefficient A of surface number S3 is 1.070980 * 10 -2 And so on.

[0088] The above scheme enables fixed-focus lenses to have the advantages of wide field of view, low cost, short total length, and good image quality, with a total optical length (TTL) of 12.18mm.

[0089] Furthermore, Figure 4This is a spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 2 of this utility model. Figure 4 The vertical direction represents the normalized aperture, with 0 indicating it's on the optical axis, and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focal point, in millimeters (mm). For example... Figure 4 As shown, the spherical aberration of the fixed-focus lens provided in Embodiment 2 of this utility model is controlled within (-0.01mm, +0.01mm) at different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm, 0.656μm and 0.850μm). The curves of different wavelengths are relatively concentrated, indicating that the spherical aberration of the fixed-focus lens at each wavelength is well controlled, which can meet the requirements of wide spectrum applications.

[0090] Example 3

[0091] Figure 5 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 3 of this utility model, as shown below. Figure 5 As shown, the fixed-focus lens provided in Embodiment 3 of this utility model includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170 arranged sequentially along the optical axis from the object plane to the image plane; the first lens 110 is a negative power lens, the second lens 120 is a negative power lens, the third lens 130 is a positive power lens, the fourth lens 140 is either a positive or negative power lens, the fifth lens 150 is a positive power lens, the sixth lens 160 is a negative power lens, and the seventh lens 170 is a positive power lens; the optical power of the second lens 120 is Φ2, the optical power of the third lens 130 is Φ3, the optical power of the fourth lens 140 is Φ4, the optical power of the fifth lens 150 is Φ5, the optical power of the sixth lens 160 is Φ6, and the optical power of the fixed-focus lens is Φ, wherein:

[0092] -0.76≤Φ2 / Φ≤-0.48;0.32≤Φ3 / Φ≤0.98;-0.56≤Φ4 / Φ≤0.90;

[0093] 0.32≤Φ5 / Φ≤1.21; -1.18≤Φ6 / Φ≤-0.35; 0.16≤Φ7 / Φ≤0.74.

[0094] The materials and other optical physical parameters such as Abbe number of each lens are the same as in Embodiment 1, and will not be repeated here. Unlike Embodiment 1, in this embodiment, the object-side surface of the second lens 120 is concave towards the object plane, and the image-side surface of the second lens 120 is concave towards the image plane; the object-side surface of the fourth lens 140 is concave towards the object plane, and the image-side surface of the fourth lens 140 is convex towards the image plane; the object-side surface of the sixth lens 160 is concave towards the object plane, and the image-side surface of the sixth lens 160 is convex towards the image plane; the fifth lens 150 and the sixth lens 160 are supported by spacers. The third lens 130 is a glass spherical lens, and the fourth lens 140 is a plastic aspherical lens with negative optical power.

[0095] Table 5 details the specific settings parameters of each lens in the fixed-focus lens provided in Embodiment 3 of this utility model, according to another feasible implementation. The fixed-focus lens in Table 5 corresponds to... Figure 5 The fixed-focus lens shown.

[0096] Table 5 Design Values ​​for Fixed-Focus Lenses

[0097]

[0098] In Table 5, the surface numbers are assigned according to the surface sequence of each lens. For example, surface number "S1" represents the object-side surface of the first lens, surface number "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture of a fixed-focus lens; "IMA" represents the image plane of the lens; the radius of curvature represents the curvature of the lens surface. A positive value indicates that the surface bends towards the object plane with the center closer to the image plane, while a negative value indicates that the surface bends towards the image plane with the center closer to the object plane; "Infinity" represents a plane with an infinite radius of curvature; the thickness represents the axial distance between the current surface and the next surface; the refractive index (Nd) represents the ability of the material between the current surface and the next surface to deflect light, with a blank space indicating that the current position is air and the refractive index is 1; the Abbe number (Vd) represents the dispersion characteristics of the material between the current surface and the next surface, with a blank space indicating that the current position is air; the half-aperture (half-diameter) represents the effective ray diameter of the lens; and the k-value represents the magnitude of the conic coefficient of the aspherical surface.

[0099] The following describes a feasible implementation method, referring to Table 6, for data on the aspherical surface of the aspherical lens. The data for the fitted conic coefficient k are detailed in Table 5.

[0100] Table 6. Design values ​​of parameters for various surfaces of aspherical lenses in fixed-focus lenses.

[0101]

[0102] In Table 6, 2.934854E-02 indicates that the coefficient A of surface number S3 is 2.934854 * 10. -2 And so on.

[0103] The above scheme enables fixed-focus lenses to have the advantages of wide field of view, low cost, short total length, and good image quality, with a total optical length (TTL) of 11.93mm.

[0104] Furthermore, Figure 6 This is a spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 3 of this utility model. Figure 6 The vertical direction represents the normalized aperture, with 0 indicating it's on the optical axis, and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focal point, in millimeters (mm). For example... Figure 6 As shown, the fixed-focus lens provided in Embodiment 3 of this utility model has spherical aberration controlled within (-0.01mm, +0.01mm) at different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm, 0.656μm and 0.850μm). The curves for different wavelengths are relatively concentrated, indicating that the fixed-focus lens has good control over spherical aberration at each wavelength, which can meet the requirements of wide-spectrum applications.

[0105] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A fixed-focus lens, characterized in that, It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the object plane to the image plane; The first lens is a negative power lens, the second lens is a negative power lens, the third lens is a positive power lens, the fourth lens is a positive power lens or a negative power lens, the fifth lens is a positive power lens, the sixth lens is a negative power lens, and the seventh lens is a positive power lens. The second lens has an optical power of Φ2, the third lens has an optical power of Φ3, the fourth lens has an optical power of Φ4, the fifth lens has an optical power of Φ5, the sixth lens has an optical power of Φ6, and the fixed-focus lens has an optical power of Φ, wherein: -0.76≤Φ2 / Φ≤-0.48;0.32≤Φ3 / Φ≤0.98;-0.56≤Φ4 / Φ≤0.90; 0.32≤Φ5 / Φ≤1.21; -1.18≤Φ6 / Φ≤-0.35; 0.16≤Φ7 / Φ≤0.

74.

2. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens comprises two glass spherical lenses and five plastic aspherical lenses; wherein: The first lens is the glass spherical lens; The second lens, the fifth lens, the sixth lens, and the seventh lens are all plastic aspherical lenses; The third lens is either the glass spherical lens or the plastic aspherical lens; The fourth lens is either a glass spherical lens with positive optical power or a plastic aspherical lens with negative optical power.

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 protrudes towards the object plane, and the image-side surface of the first lens is recessed towards the image plane; The object-side surface of the second lens is recessed toward the object plane, and the image-side surface of the second lens is recessed toward the image plane; Alternatively, the object-side surface of the second lens is recessed towards the object surface, and the image-side surface of the second lens is convex towards the image surface; The object-side surface of the third lens bulges towards the object plane, and the image-side surface of the third lens bulges towards the image plane; The object-side surface of the fourth lens bulges towards the object plane, and the image-side surface of the fourth lens bulges towards the image plane; Alternatively, the object-side surface of the fourth lens is recessed towards the object plane, and the image-side surface of the fourth lens is convex towards the image plane; The object-side surface of the fifth lens bulges towards the object plane, and the image-side surface of the fifth lens bulges towards the image plane; The object-side surface of the sixth lens is recessed towards the object plane, and the image-side surface of the sixth lens is recessed towards the image plane. Alternatively, the object-side surface of the sixth lens is recessed towards the object plane, and the image-side surface of the sixth lens is convex towards the image plane; The object-side surface of the seventh lens bulges towards the object plane, and the image-side surface of the seventh lens bulges towards the image plane.

4. The fixed-focus lens according to claim 1, characterized in that, The refractive index of the first lens is Nd1, and the Abbe number of the first lens is Vd1; where: 1.48<Nd1<1.93, 17.95<Vd1<70.

87.

5. The fixed-focus lens according to claim 1, characterized in that, The center thickness of the third lens is CT3, the center thickness of the fourth lens is CT4, and the distance from the center of the optical axis on the object side of the first lens to the image plane is TTL; wherein: 0.05≤CT3 / TTL≤0.14, 0.02≤CT4 / TTL≤0.

19.

6. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens also includes an aperture stop; The aperture is located in the optical path between the third lens and the fourth lens.

7. The fixed-focus lens according to claim 1, characterized in that, The fifth lens and the sixth lens are cemented together; or, the fifth lens and the sixth lens are supported by a spacer gasket.

8. The fixed-focus lens according to claim 1, characterized in that, The distance from the center of the optical axis on the object side of the first lens to the image plane is TTL; where TTL ≤ 12.2 mm.

9. The fixed-focus lens according to claim 1, characterized in that, The field of view of the fixed-focus lens is FOV; where: FOV≥170°.

Images