A fixed focus lens

Abstract

The application discloses a fixed focus lens, which comprises a first lens with negative optical power, a second lens with negative optical power, a diaphragm, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with negative optical power, a seventh lens with positive optical power, an eighth lens with negative optical power and a ninth lens with positive optical power arranged in sequence along an optical axis from an object side to an image side, wherein the sixth lens and the seventh lens form a cemented lens. The fixed focus lens is designed by optimizing the shape, optical power of each lens element and the relative position of each lens element, and has the comprehensive performance of meeting the imaging requirements, compact structure, large aperture and super large field of view. The maximum aperture of the fixed focus lens is 1.0, the total optical length is not more than 22.5 mm, the maximum matching 1 / 2.7" chip can reach 170 DEG, and the comprehensive performance meets the use requirements of general chips for security monitoring.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, in particular to a fixed focus lens. BACKGROUND

[0002] With the gradual maturity of the security lens industry, the market demand gradually tends to be super large field of view (for example, 160° FOV) or large aperture (for example, F1.0). However, the lenses on the market cannot simultaneously meet the requirements of super large field of view and large aperture. SUMMARY

[0003] The present application provides a fixed focus lens which can be matched with a 1 / 2.7" chip and can simultaneously meet the requirements of F1.0 and 170° field of view.

[0004] To achieve the above purpose, the present application provides a fixed focus lens, comprising: a first lens with negative refractive power, a second lens with negative refractive power, a diaphragm, a third lens with positive refractive power, a fourth lens with negative refractive power, a fifth lens with positive refractive power, a sixth lens with negative refractive power, a seventh lens with positive refractive power, an eighth lens with negative refractive power and a ninth lens with positive refractive power, which are sequentially arranged along the optical axis from the object side to the image side, wherein the sixth lens and the seventh lens form a cemented lens.

[0005] Optionally, the refractive index Nd1 of the first lens satisfies: 1.7<Nd1<2.1, and the refractive power Φ1 of the first lens and the refractive power Φ of the fixed focus lens satisfy: -0.57<Φ1 / Φ<-0.37.

[0006] Optionally, the refractive power Φ2 of the second lens and the refractive power Φ of the fixed focus lens satisfy: -0.35<Φ2 / Φ<-0.20.

[0007] Optionally, the overall refractive power Φ34 of the third lens and the fourth lens and the refractive power Φ of the fixed focus lens satisfy: 0.1<Φ34 / Φ<0.25.

[0008] Optionally, the refractive power Φ5 of the fifth lens and the refractive power Φ of the fixed focus lens satisfy: 0.13≤Φ5 / Φ≤0.33, and the Abbe number Vd5 of the fifth lens satisfies: 55<Vd5<95.

[0009] Optionally, the overall refractive power Φ67 of the sixth lens and the seventh lens and the refractive power Φ of the fixed focus lens satisfy: 0.1<Φ67 / Φ<0.43.

[0010] Optionally, the refractive power Φ8 of the eighth lens and the refractive power Φ of the fixed focus lens satisfy: -0.28<Φ8 / Φ<-0.15.

[0011] Optionally, an overall optical power Φ9 of the ninth lens and an optical power Φ of the fixed focus lens satisfy: 0.3 < Φ9 / Φ < 0.44.

[0012] Optionally, the second lens, the third lens, the fourth lens, the eighth lens and the ninth lens are plastic aspheric lenses, and the first lens, the fifth lens, the sixth lens and the seventh lens are glass spherical lenses.

[0013] Optionally, an object side surface of the first lens is convex, an image side surface of the first lens is concave, an object side surface of the second lens is concave, an image side surface of the second lens is convex, an object side surface of the third lens is convex, an image side surface of the third lens is convex, an object side surface of the fourth lens is concave, an image side surface of the fourth lens is convex, an object side surface of the fifth lens is convex, an image side surface of the fifth lens is convex, an object side surface of the sixth lens is convex, an image side surface of the sixth lens is concave, an object side surface of the seventh lens is convex, an image side surface of the seventh lens is convex, an object side surface of the eighth lens is concave, an image side surface of the eighth lens is concave, an object side surface of the ninth lens is convex, and an image side surface of the ninth lens is convex.

[0014] The fixed focus lens according to the embodiment of the present application comprises, sequentially arranged along an optical axis from an object side to an image side, a first lens with negative optical power, a second lens with negative optical power, a diaphragm, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with negative optical power, a seventh lens with positive optical power, an eighth lens with negative optical power and a ninth lens with positive optical power, wherein the sixth lens and the seventh lens form a cemented lens. The present application realizes the design of a fixed focus lens with comprehensive performance of meeting imaging requirements, compact structure, large aperture and super large field of view by optimizing the shape, optical power of each lens element and the relative position of each lens element. The fixed focus lens has a maximum aperture of 1.0, an optical total length of not more than 22.5 mm, can match a 1 / 2.7" chip, has a FOV of 170°, and its comprehensive performance meets the use requirements of general chips for security monitoring.

[0015] It should be understood that the description in this section is not intended to identify key or critical features of embodiments of the present application or to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings needed in the embodiment description. Obviously, the drawings in the following description only show some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

[0017] Figure 1 is a structural schematic diagram of a fixed focus lens according to an embodiment of the present application;

[0018] Figure 2 is a structural schematic diagram of a fixed focus lens according to an embodiment of the present application;

[0019] Figure 3 is an axial aberration diagram of the fixed focus lens according to the first embodiment of the present application;

[0020] Figure 4 is a structural schematic diagram of a fixed focus lens according to a second embodiment of the present application;

[0021] Figure 5 is an axial aberration diagram of the fixed focus lens according to the second embodiment of the present application;

[0022] Figure 6 is a structural schematic diagram of a fixed focus lens according to a third embodiment of the present application;

[0023] Figure 7 is an axial aberration diagram of the fixed focus lens according to the third embodiment of the present application;

[0024] Figure 8 is a structural schematic diagram of a fixed focus lens according to a fourth embodiment of the present application;

[0025] Figure 9 is an axial aberration diagram of the fixed focus lens according to the fourth embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the personnel in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0027] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to the process, method, product or device.

[0028] Figure 1 is a structural schematic diagram of a fixed focus lens according to an embodiment of the present application. As shown in the figure, the fixed focus lens comprises, in order along the optical axis from the object side to the image side, a first lens 1 with negative optical power, a second lens 2 with negative optical power, a stop STO, a third lens 3 with positive optical power, a fourth lens 4 with negative optical power, a fifth lens 5 with positive optical power, a sixth lens 6 with negative optical power, a seventh lens 7 with positive optical power, an eighth lens 8 with negative optical power, and a ninth lens 9 with positive optical power, wherein the sixth lens 6 and the seventh lens 7 form a cemented lens. Figure 1

[0029] The optical power of the first lens 1 is negative, which can make the object side light rays gently enter the imaging system, so that the light rays enter the second lens 2 at a small incident angle, reducing the proportion of high-order aberrations, while reducing the lens aperture and shortening the total length of the lens. The optical power of the second lens 2 is negative, which can further make the object side light rays gently enter the imaging system, reducing the proportion of high-order aberrations, while also correcting the field curvature of the system. Therefore, by setting the optical power of the first lens 1 and the second lens 2 to be negative, the light rays with a large angle can be collected into the lens and gently enter the imaging system. This makes it easy to form a large field angle lens for the fixed focus lens. The stop STO is located between the second lens 2 and the third lens 3, and the optical power of the fifth lens 5 is set to be positive, which is conducive to the realization of a large aperture. Reasonably configuring the optical power of the remaining lenses can improve the image quality of the lens. Among them, the optical power of the third lens 3 is set to be positive and the optical power of the fourth lens 4 is set to be negative, which is conducive to reducing the spherical aberration and field curvature of the lens. The optical power of the sixth lens 6 is set to be negative and the optical power of the seventh lens 7 is set to be positive, which is conducive to reducing the spherical aberration and chromatic aberration of the lens. The optical power of the eighth lens 8 is set to be negative, which can effectively reduce the astigmatism and coma of the system, and the optical power of the ninth lens 9 is set to be positive, which can effectively reduce the astigmatism of the system.

[0030] Therefore, by reasonably configuring the first lens 1 to the ninth lens 9, a lens with a large aperture, a large field angle, and high image quality can be realized at the same time.

[0031] ​Optionally, the refractive index Nd1 of the first lens 1 satisfies: 1.7 < Nd1 < 2.1, and the focal power Φ1 of the first lens 1 and the focal power Φ of the fixed focus lens satisfy: -0.57 < Φ1 / Φ < -0.37. The high refractive index material of the lens can better make the light at a large angle enter the second lens 2, which is conducive to the realization of the super large field of view, and at the same time, is conducive to reducing the aperture and the total length of the lens and reducing the tolerance sensitivity of the system. The focal power of the lens in this range can make the object side light gently enter the imaging system, so that the light enters the second lens 2 at a smaller incident angle, reduces the proportion of high-order aberrations, and at the same time, reduces the lens aperture and is conducive to shortening the total length of the lens.

[0032] Optionally, the focal power Φ2 of the second lens 2 and the focal power Φ of the fixed focus lens satisfy: -0.35 < Φ2 / Φ < -0.20. The focal power of the lens in this range can further make the object side light gently enter the imaging system, reduce the proportion of high-order aberrations, and at the same time, correct the field curvature of the system.

[0033] Optionally, the overall focal power Φ34 of the third lens 3 and the fourth lens 4 and the focal power Φ of the fixed focus lens satisfy: 0.1 < Φ34 / Φ < 0.25. The focal power of the two lenses in this range can effectively reduce the spherical aberration and the field curvature of the system, thereby obtaining higher image quality.

[0034] Optionally, the focal power Φ5 of the fifth lens 5 and the focal power Φ of the fixed focus lens satisfy: 0.13 ≤ Φ5 / Φ ≤ 0.33, and the Abbe number Vd5 of the fifth lens 5 satisfies: 55 < Vd5 < 95. The lens satisfies the above focal power ratio range, which is conducive to the realization of the large aperture of the system. When the Abbe number of the fifth lens 5 is in the range, the chromatic aberration of the system can be effectively reduced, thereby obtaining high image quality.

[0035] Optionally, the overall focal power Φ67 of the sixth lens 6 and the seventh lens 7 and the focal power Φ of the fixed focus lens satisfy: 0.1 < Φ67 / Φ < 0.43. The sixth lens 6 and the seventh lens 7 satisfy the above focal power ratio range, which can effectively reduce the spherical aberration and the chromatic aberration of the system, thereby obtaining higher image quality.

[0036] In one embodiment, the Abbe number of the sixth lens 6 is lower than the Abbe number of the seventh lens. For example, the sixth lens 6 is a negative focal power low Abbe number glass lens, the seventh lens 7 is a positive focal power high Abbe number glass lens, and the sixth lens 6 and the seventh lens 7 are cemented, which can effectively reduce the chromatic aberration and the spherical aberration in the system, and is conducive to realizing high image quality.

[0037] Optionally, the focal power Φ8 of the eighth lens 8 and the focal power Φ of the fixed focus lens satisfy: -0.28 < Φ8 / Φ < -0.15. The focal power of the lens in this range can effectively reduce the astigmatism and the coma of the system, thereby obtaining higher image quality.

[0038] Optionally, the overall optical power Φ9 of the ninth lens 9 and the optical power Φ of the fixed focus lens satisfy: 0.3 < Φ9 / Φ < 0.44. The lens optical power in this range can effectively reduce the astigmatism of the system, thereby obtaining higher image quality.

[0039] Optionally, the second lens 2, the third lens 3, the fourth lens 4, the eighth lens 8 and the ninth lens 9 are plastic aspheric lenses, and the first lens 1, the fifth lens 5, the sixth lens 6 and the seventh lens 7 are glass spherical lenses. The lens adopts a combination of 4 pieces of spherical glass and 5 pieces of aspheric plastic, which can well correct aberration and ensure good enough image quality, and can simultaneously satisfy large aperture and large field of view.

[0040] Optionally, the object side of the first lens 1 is convex, and the image side is concave; the object side of the second lens 2 is concave, and the image side is convex; the object side of the third lens 3 is convex, and the image side is convex; the object side of the fourth lens 4 is concave, and the image side is convex; the object side of the fifth lens 5 is convex, and the image side is convex; the object side of the sixth lens 6 is convex, and the image side is concave; the object side of the seventh lens 7 is convex, and the image side is convex; the object side of the eighth lens 8 is concave, and the image side is concave; the object side of the ninth lens 9 is convex, and the image side is convex.

[0041] Wherein, when the object side is convex, the lens surface close to the object side protrudes towards the object side; when the object side is concave, the lens surface close to the object side protrudes towards the image side; when the image side is convex, the lens surface close to the image side protrudes towards the image side; when the image side is concave, the lens surface close to the image side protrudes towards the object side.

[0042] Wherein, the first lens 1 is a convex-concave crescent glass spherical negative lens, the second lens 2 is a concave-convex crescent plastic aspheric negative lens, the third lens 3 is a double-convex plastic aspheric positive lens, the fourth lens 4 is a concave-convex plastic aspheric negative lens, the fifth lens 5 is a double-convex glass spherical positive lens, the sixth lens 6 is a convex-concave crescent glass spherical negative lens, the seventh lens 7 is a double-convex glass spherical positive lens, the eighth lens 8 is a double-concave plastic aspheric negative lens, and the ninth lens 9 is a double-convex plastic aspheric positive lens.

[0043] Further, by reasonably matching the optical power, surface type, material and the like between the first lens 1 and the ninth lens 9, the field of view of the lens can reach more than 170°, and the aperture is close to F1.0. Therefore, in actual application, images can be better captured, such as products like a punch card can better capture portraits.

[0044] The fixed focus lens according to the present application is described below with specific embodiments.

[0045] Embodiment one

[0046] Figure 2 This is a schematic diagram of the fixed-focus lens proposed in Embodiment 1 of the present invention. Figure 2 As shown, the fixed-focus lens includes nine lens elements, from lens 1 to lens 9, and a filter P. Lens 1 is a convex-concave meniscus glass spherical negative lens; lens 2 is a convex-concave meniscus plastic aspherical negative lens; lens 3 is a biconvex plastic aspherical positive lens; lens 4 is a biconvex plastic aspherical negative lens; lens 5 is a biconvex glass spherical positive lens; lens 6 is a convex-concave meniscus glass spherical negative lens; lens 7 is a biconvex glass spherical positive lens; lens 8 is a biconcave plastic aspherical negative lens; and lens 9 is a biconvex plastic aspherical positive lens. Lens 6 and lens 7 are cemented together.

[0047] Among them, Φ1 / Φ=-0.52; Φ2 / Φ=-0.27; Φ34 / Φ=0.23; Φ5 / Φ=0.23; Φ67 / Φ=0.22; Φ8 / Φ=-0.25; Φ9 / Φ=0.33; Nd1=1.90; Vd5=61.

[0048] In Example 1, the focal length of the fixed-focus lens is f = 2.57 mm, F = 1.08, and the total length is 22.432 mm. The design values ​​of each lens are shown in Table 1.

[0049] Table 1. Design values ​​for each lens in the fixed-focus lens of the embodiment.

[0050]

[0051]

[0052] In Table 1, the surface numbers S1-S20 are assigned according to the surface sequence of each lens. "STO" represents the aperture stop of the lens; "IMA" represents the image plane of the lens; the radius of curvature represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the image plane and a negative value indicating that the surface bends towards the object plane. "Infinity" indicates that the surface is flat and the radius of curvature is infinite; the thickness represents the central axial distance between the current surface and the next surface; the refractive index represents the ability of the material between the current surface and the next surface to deflect light; a blank space indicates that the current position is air and the refractive index is 1; and the k value represents the magnitude of the conicity coefficient of the aspherical surface.

[0053] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations:

[0054]

[0055] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th and 16th order terms of the aspherical polynomial.

[0056] Table 2 Aspherical coefficients of a fixed-focus lens in the embodiments

[0057]

[0058]

[0059] Figure 3 This is the axial aberration diagram of the fixed-focus lens proposed in Embodiment 1 of the present invention. The vertical direction represents the normalized aperture, 0 indicates on the optical axis, and the vertical vertex represents the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). Different linear curves in the diagram represent different wavelengths of system imaging (436nm, 486nm, 546nm, 588nm, and 656nm, where blue lines represent 436nm, green lines represent 486nm, red lines represent 546nm, yellow lines represent 588nm, and purple lines represent 656nm). Figure 3 It can be seen that the axial aberrations of different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens is well controlled at each wavelength, which can meet the requirements of wide-spectrum applications.

[0060] Example 2

[0061] Figure 4 This is a schematic diagram of the fixed-focus lens proposed in Embodiment 2 of the present invention. Figure 4 As shown, the fixed-focus lens includes nine lens elements, from lens 1 to lens 9, and a filter P. Lens 1 is a convex-concave meniscus glass spherical negative lens; lens 2 is a convex-concave meniscus plastic aspherical negative lens; lens 3 is a biconvex plastic aspherical positive lens; lens 4 is a biconvex plastic aspherical negative lens; lens 5 is a biconvex glass spherical positive lens; lens 6 is a convex-concave meniscus glass spherical negative lens; lens 7 is a biconvex glass spherical positive lens; lens 8 is a biconcave plastic aspherical negative lens; and lens 9 is a biconvex plastic aspherical positive lens. Lens 6 and lens 7 are cemented together.

[0062] Among them, Φ1 / Φ=-0.44; Φ2 / Φ=-0.29; Φ34 / Φ=0.22; Φ5 / Φ=0.24; Φ67 / Φ=0.12; Φ8 / Φ=-0.17; Φ9 / Φ=0.40; Nd1=1.82; Vd5=90.

[0063] The focal length of the fixed focus lens in Example Two is f = 2.50 mm, F = 1.08; the total length is 22.330 mm; the design values of each lens are shown in Table 3.

[0064] Table 3 Design values of each lens of the fixed focus lens in Example Two

[0065]

[0066] The surface serial numbers S1-S20 in Table 3 are numbered according to the surface order of each lens, "STO" represents the stop of the lens; "IMA" represents the image surface of the lens; the radius of curvature represents the bending degree of the lens surface, a positive value represents that the surface is bent towards the image side, and a negative value represents that the surface is bent towards the object side, wherein "Infinity" represents that the surface is a plane, and the radius of curvature is infinite; the thickness represents the center axis distance from the current surface to the next surface; the refractive index represents the deflection ability of the material between the current surface and the next surface; the space represents that the current position is air, and the refractive index is 1; the k value represents the numerical size of the conic coefficient of the aspheric surface.

[0067] The conic coefficient of the aspheric surface can be defined by the following aspheric surface formula, but is not limited to the following representation method:

[0068]

[0069] Wherein, z is the axial height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitting sphere, which is the reciprocal of the radius of curvature in numerical value; k is the fitting conic coefficient; A-G are the 4th, 6th, 8th, 10th, 12th, 14th and 16th order term coefficients of the aspheric polynomial.

[0070] Table 4 Conic coefficients of the fixed focus lens in Example Two

[0071]

[0072]

[0073] Figure 5 The axial aberration diagram of the fixed focus lens proposed in Example Two of the present application is shown in the figure. Wherein, the vertical direction represents the normalization of the aperture, 0 represents on the optical axis, and the vertical direction vertex represents the maximum pupil radius; the horizontal direction represents the offset amount relative to the ideal focus point, with the unit of millimeter (mm). Different line curves in the figure represent different wavelengths (436 nm, 486 nm, 546 nm, 588 nm and 656 nm) of system imaging, wherein the blue line represents 436 nm, the green line represents 486 nm, the red line represents 546 nm, the yellow line represents 588 nm, and the purple line represents 656 nm, and the figure is obtained by Figure 5It can be seen that the axial aberrations of different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens is well controlled at each wavelength, which can meet the requirements of wide-spectrum applications.

[0074] Example 3

[0075] Figure 6 This is a schematic diagram of the fixed-focus lens proposed in Embodiment 3 of the present invention. Figure 6 As shown, the fixed-focus lens includes nine lens elements, from lens 1 to lens 9, and a filter P. Lens 1 is a convex-concave meniscus glass spherical negative lens; lens 2 is a convex-concave meniscus plastic aspherical negative lens; lens 3 is a biconvex plastic aspherical positive lens; lens 4 is a biconvex plastic aspherical negative lens; lens 5 is a biconvex glass spherical positive lens; lens 6 is a convex-concave meniscus glass spherical negative lens; lens 7 is a biconvex glass spherical positive lens; lens 8 is a biconcave plastic aspherical negative lens; and lens 9 is a biconvex plastic aspherical positive lens. Lens 6 and lens 7 are cemented together.

[0076] Among them, Φ1 / Φ=-0.44; Φ2 / Φ=-0.23; Φ34 / Φ=0.11; Φ5 / Φ=0.16; Φ67 / Φ=0.39; Φ8 / Φ=-0.25; Φ9 / Φ=0.35; Nd1=1.80; Vd5=90.

[0077] In Example 3, the focal length of the fixed-focus lens is f = 2.60 mm, F = 1.08, and the total length is 20.076 mm. The design values ​​of each lens are shown in Table 5.

[0078] Table 5. Design values ​​of each lens in Example 3's fixed-focus lens.

[0079]

[0080]

[0081] In Table 5, the surface numbers S1-S20 are assigned according to the surface sequence of each lens. "STO" represents the aperture stop of the lens; "IMA" represents the image plane of the lens; the radius of curvature represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the image plane and a negative value indicating that the surface bends towards the object plane. "Infinity" indicates that the surface is flat and the radius of curvature is infinite; the thickness represents the central axial distance between the current surface and the next surface; the refractive index represents the ability of the material between the current surface and the next surface to deflect light; a blank space indicates that the current position is air and the refractive index is 1; and the k value represents the magnitude of the conicity coefficient of the aspherical surface.

[0082] The aspherical conic coefficients can be defined using the following aspherical formulas, but are not limited to the following representations:

[0083]

[0084] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AG are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th and 16th order terms of the aspherical polynomial.

[0085] Table 6 Aspherical coefficients of the fixed-focus lens in Example 3

[0086]

[0087] Figure 7 This is the axial aberration diagram of the fixed-focus lens proposed in Embodiment 3 of the present invention. The vertical direction represents the normalized aperture, 0 indicates on the optical axis, and the vertical vertex represents the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). Different linear curves in the diagram represent different wavelengths of system imaging (436nm, 486nm, 546nm, 588nm, and 656nm, where blue lines represent 436nm, green lines represent 486nm, red lines represent 546nm, yellow lines represent 588nm, and purple lines represent 656nm). Figure 7 It can be seen that the axial aberrations of different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens is well controlled at each wavelength, which can meet the requirements of wide-spectrum applications.

[0088] Example 4

[0089] Figure 8 This is a schematic diagram of the fixed-focus lens proposed in Embodiment 4 of the present invention. Figure 8 As shown, the fixed-focus lens includes nine lens elements, from lens 1 to lens 9, and a filter P. Lens 1 is a convex-concave meniscus glass spherical negative lens; lens 2 is a convex-concave meniscus plastic aspherical negative lens; lens 3 is a biconvex plastic aspherical positive lens; lens 4 is a biconvex plastic aspherical negative lens; lens 5 is a biconvex glass spherical positive lens; lens 6 is a convex-concave meniscus glass spherical negative lens; lens 7 is a biconvex glass spherical positive lens; lens 8 is a biconcave plastic aspherical negative lens; and lens 9 is a biconvex plastic aspherical positive lens. Lens 6 and lens 7 are cemented together.

[0090] Wherein, Φ1 / Φ = -0.41; Φ2 / Φ = -0.31; Φ34 / Φ = 0.15; Φ5 / Φ = 0.30; Φ67 / Φ = 0.22; Φ8 / Φ = -0.24; Φ9 / Φ = 0.34; Nd1 = 2.07; Vd5 = 60.

[0091] The focal length of the fixed focus lens in Example Four is f = 2.66 mm, F = 1.08; the total length is 21.477 mm; the design values of each lens are shown in Table 7.

[0092] Table 7 Design values of each lens of the fixed focus lens in Example Four

[0093]

[0094]

[0095] The surface serial numbers S1-S20 in Table 7 are numbered according to the surface order of each lens, "STO" represents the stop of the lens; "IMA" represents the image surface of the lens; the radius of curvature represents the bending degree of the lens surface, a positive value represents that the surface is bent towards the image side, and a negative value represents that the surface is bent towards the object side, wherein "Infinity" represents that the surface is a plane, and the radius of curvature is infinite; the thickness represents the center axis distance from the current surface to the next surface; the refractive index represents the deflection ability of the material between the current surface and the next surface; the space represents that the current position is air, and the refractive index is 1; the k value represents the numerical size of the conic coefficient of the aspheric surface.

[0096] The conic coefficient of the aspheric surface can be defined by the following aspheric surface formula, but is not limited to the following representation method:

[0097]

[0098] Wherein, z is the axial height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitting sphere, which is the reciprocal of the radius of curvature in numerical value; k is the fitting conic coefficient; A-G are the 4th order, 6th order, 8th order, 10th order, 12th order, 14th order and 16th order term coefficients of the aspheric polynomial.

[0099] Table 8 Conic coefficients of the fixed focus lens in Example Four

[0100]

[0101]

[0102] Figure 9is an axial aberration diagram of the fixed focus lens according to the fourth embodiment of the present application. In the diagram, the vertical direction represents the normalized aperture, 0 represents the optical axis, and the top of the vertical direction represents the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focus point, with the unit being millimeters (mm). Different linear curves in the diagram represent different wavelengths (436 nm, 486 nm, 546 nm, 588 nm, and 656 nm) of system imaging, where the blue line represents 436 nm, the green line represents 486 nm, the red line represents 546 nm, the yellow line represents 588 nm, and the purple line represents 656 nm. The axial aberration of different wavelengths is controlled within the range of (-0.05 mm, +0.05 mm), which indicates that the spherical aberration of the fixed focus lens at different wavelengths is well controlled and can meet the wide-spectrum application requirements. Figure 9 It can be seen that the axial aberration of different wavelengths is controlled within the range of (-0.05 mm, +0.05 mm), which indicates that the spherical aberration of the fixed focus lens at different wavelengths is well controlled and can meet the wide-spectrum application requirements.

[0103] Therefore, the fixed focus lens according to the embodiments of the present application includes, along the optical axis from the object side to the image side, a first lens with negative optical power, a second lens with negative optical power, a stop, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with negative optical power, a seventh lens with positive optical power, an eighth lens with negative optical power, and a ninth lens with positive optical power, wherein the sixth lens and the seventh lens form a cemented lens. The present application optimizes the shape, optical power, and relative position of each lens element, realizes the design of a fixed focus lens with comprehensive performance of meeting imaging requirements, compact structure, large aperture, and ultra-large field of view; the maximum aperture of the fixed focus lens is 1.0, the total optical length is not greater than 22.5 mm, the maximum matching chip is 1 / 2.7", the FOV is up to 170°, and the comprehensive performance meets the use requirements of general chips for security monitoring.

[0104] It should be understood that the various forms of flow shown above can be reordered, added, or deleted steps. For example, each step described in the present application can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions of the present application can be achieved, which is not limited herein.

[0105] The above specific embodiments do not constitute a limitation on the protection scope of the present application. 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 replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A fixed focus lens characterized by, Comprise: sequentially arranged along the optical axis from the object side to the image side are a first lens with negative optical power, a second lens with negative optical power, a diaphragm, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with negative optical power, a seventh lens with positive optical power, an eighth lens with negative optical power, and a ninth lens with positive optical power, wherein the sixth lens and the seventh lens form a cemented lens; wherein the lenses with optical power in the fixed focus lens are nine pieces; the optical power Φ1 of the first lens and the optical power Φ of the fixed focus lens satisfy: -0.57<Φ1 / Φ<-0.37; the optical power Φ2 of the second lens and the optical power Φ of the fixed focus lens satisfy: -0.35<Φ2 / Φ<-0.20; the overall optical power Φ34 of the third lens and the fourth lens and the optical power Φ of the fixed focus lens satisfy: 0.1<Φ34 / Φ<0.25; the optical power Φ5 of the fifth lens and the optical power Φ of the fixed focus lens satisfy: 0.13≤Φ5 / Φ≤0.33; the overall optical power Φ67 of the sixth lens and the seventh lens and the optical power Φ of the fixed focus lens satisfy: 0.1<Φ67 / Φ<0.43; the optical power Φ8 of the eighth lens and the optical power Φ of the fixed focus lens satisfy: -0.28<Φ8 / Φ<-0.15; the overall optical power Φ9 of the ninth lens and the optical power Φ of the fixed focus lens satisfy: 0.3<Φ9 / Φ<0.

44.

2. The fixed focus lens of claim 1, wherein The refractive index Nd1 of the first lens satisfies: 1.7<Nd1<2.

1.

3. The fixed focus lens of claim 1, wherein, The Abbe number Vd5 of the fifth lens satisfies: 55<Vd5<95.

4. The fixed focus lens of claim 1, wherein, The second lens, the third lens, the fourth lens, the eighth lens and the ninth lens are plastic aspherical lenses, and the first lens, the fifth lens, the sixth lens and the seventh lens are glass spherical lenses.

5. The fixed focus lens of claim 1, wherein, The object side surface of the first lens is convex, the image side surface of the first lens is concave, the object side surface of the second lens is concave, the image side surface of the second lens is convex, the object side surface of the third lens is convex, the image side surface of the third lens is convex, the object side surface of the fourth lens is concave, the image side surface of the fourth lens is convex, the image side surface of the fifth lens is convex, the object side surface of the sixth lens is convex, the image side surface of the sixth lens is concave, the object side surface of the seventh lens is convex, the image side surface of the seventh lens is convex, the object side surface of the eighth lens is concave, the image side surface of the eighth lens is concave, the object side surface of the ninth lens is convex, and the image side surface of the ninth lens is convex.

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