A fixed-focus lens

Abstract

This invention discloses a fixed-focus lens. The fixed-focus lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged sequentially along the optical axis from the object plane to the image plane; the first lens is a convex-concave lens with negative optical power, the second lens is a concave-convex lens with negative optical power, the third lens is a biconvex lens with positive optical power, the fourth lens is a concave-convex lens with negative optical power, the fifth lens is a concave-convex lens with positive optical power, the sixth lens is a convex-concave lens with negative optical power, the seventh lens is a biconvex lens with positive optical power, the eighth lens is a concave-convex lens with negative optical power, and the ninth lens is a lens with positive optical power and a convex object side. The fixed-focus lens provided by this invention ensures that the lens remains focused even at high and low temperatures while maintaining a small size and low cost, thereby improving image quality and making it suitable for a wider range of applications.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and more particularly to a fixed-focus lens. Background Technology

[0002] Fixed-focus lenses are a mainstream product in the security industry and are highly sought after by the market. As the application of 1 / 1.8” sensors becomes increasingly widespread, the requirements for the size, aperture, and operating environment of lenses paired with them are becoming more stringent. Currently, mainstream optical lenses paired with 1 / 1.8” sensors have relatively small apertures and are too large, hindering product adoption and promotion. Therefore, there is an urgent need to design a low-cost fixed-focus lens that can balance small size, large aperture, and high / low temperature confocal focusing. Summary of the Invention

[0003] This invention provides a fixed-focus lens that ensures no blurring at high or low temperatures while maintaining a small size and low cost, thereby improving image quality and making it suitable for a wider range of applications.

[0004] According to one aspect of the present invention, a fixed-focus lens is provided, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged sequentially along the optical axis from the object plane to the image plane;

[0005] 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.

[0006] The first lens, the second lens, the fourth lens, the sixth lens, and the eighth lens are all negative power lenses, while the third lens, the fifth lens, the seventh lens, and the ninth lens are all positive power lenses.

[0007] The first lens has an object-side surface that convexes towards the object surface and an image-side surface that convexes towards the object surface; the second lens has an object-side surface that is concave towards the object surface and an image-side surface that is concave towards the object surface; the third lens has an object-side surface that convex towards the object surface and an image-side surface that is concave towards the object surface; the fourth lens has an object-side surface that is concave towards the object surface and an image-side surface that is concave towards the object surface; the fifth lens has an object-side surface that is concave towards the object surface and an image-side surface that is concave towards the object surface; the sixth lens has an object-side surface that convex towards the object surface and an image-side surface that convex towards the object surface; the seventh lens has an object-side surface that convex towards the object surface and an image-side surface that is concave towards the object surface; the eighth lens has an object-side surface that is concave towards the object surface and an image-side surface that is concave towards the object surface; and the ninth lens has an object-side surface that convex towards the object surface.

[0008] Optionally, the refractive index of the fifth lens is N5, and the Abbe number is V5; wherein:

[0009] 1.43 <N5<1.90,40<V5<94。

[0010] Optionally, the focal length of the first lens is f1, the focal length of the second lens is f2, and the focal length of the optical system is f, wherein:

[0011] -5.20<(f1+f2) / f<-4.70.

[0012] Optionally, 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, the focal length of the eighth lens is f8, the focal length of the ninth lens is f9, and the focal length of the optical system is f, wherein:

[0013] 2.65 <f3 / f<3.14;-44.58<f4 / f<-8.55;2.19≤f5 / f≤4.04;-4.55<f6 / f<-2.99;1.52<f7 / f<1.73;-2.03<f8 / f<-1.78;1.46<f9 / f<1.56。

[0014] Optionally, the distance from the center of the optical axis on the object side of the first lens to the image plane is TTL, and the lens diameter of the first lens is ΦL1, wherein:

[0015] 0.43 < ΦL1 / TTL < 0.45.

[0016] Optionally, the first lens, the second lens, the third lens, the fourth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses, and the fifth lens is a glass spherical lens.

[0017] Optionally, the aspherical surfaces in the first lens, second lens, third lens, fourth lens, sixth lens, seventh lens, eighth lens, and ninth lens satisfy a first formula, which is:

[0018]

[0019] Where Z is the axial distance from the vertex of the surface at a position perpendicular to the optical axis at a height r; k is the conic coefficient; c represents the curvature at the vertex of the aspherical surface; a4, a6, a8, a 10 a 12 a 14 a 16For the higher-order aspheric coefficients corresponding to the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders of aspheric surfaces, a4r 16 These can be combined to form higher-order terms for the corresponding aspherical surfaces.

[0020] Optionally, the aperture number of the fixed-focus lens is F, where: 1.0≤F≤1.2.

[0021] Optionally, the fixed-focus lens may also include an aperture stop;

[0022] The aperture stop is located in the optical path between the second lens and the third lens.

[0023] Optionally, the fixed-focus lens is further provided with a flat glass; the flat glass is located on the image-side side of the ninth lens.

[0024] The technical solution of this invention provides a fixed-focus lens comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged sequentially along the optical axis from the object plane to the image plane. By rationally setting the number of lenses, the surface shape of the lenses, and the relative optical power of each lens in the fixed-focus lens, the invention ensures the balance of the incident angles of the front and rear lens groups of the fixed-focus lens under low cost, reduces lens sensitivity, improves production feasibility, realizes a large-aperture fixed-focus lens, and has a large target surface, which can be matched with a 1 / 1.8″ ultra-large target surface sensor chip. At the same time, it ensures that the fixed-focus lens has high resolution in an environment of -40 to 80°C, improves image quality, meets the requirements of high-definition image quality, and effectively expands the application range of the lens.

[0025] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in an embodiment of the present invention;

[0028] Figure 2 An axial aberration curve diagram of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0029] Figure 3This is a ray fan diagram of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0030] Figure 4 This is a chromatic aberration curve of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0031] Figure 5 This is a schematic diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0032] Figure 6 This is an axial aberration curve diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0033] Figure 7 This is a ray fan diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0034] Figure 8 This is a chromatic aberration curve of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0035] Figure 9 This is a schematic diagram of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0036] Figure 10 This is an axial aberration curve diagram of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0037] Figure 11 This is a ray fan diagram of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0038] Figure 12 This is a chromatic aberration curve of a fixed-focus lens provided in Embodiment 3 of the present invention. Detailed Implementation

[0039] 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 of the present invention. 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 scope of protection of the present invention.

[0040] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0041] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the fixed-focus lens 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, a seventh lens 107, an eighth lens 108, and a ninth lens 109 arranged sequentially along the optical axis from the object plane to the image plane. 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 first lens 101, second lens 102, fourth lens 104, sixth lens 106, and eighth lens 108 are all negative power lenses, while the third lens 103, fifth lens 105, seventh lens 107, and ninth lens 109 are all positive power lenses. The object-side surface of the first lens 101 convexes towards the object plane, and the image-side surface of the first lens 101 convexes towards the object plane. The object-side surface of the second lens 102... The image-side surface of the second lens 102 is concave towards the object plane; the image-side surface of the third lens 103 is convex towards the object plane, and the image-side surface of the third lens 103 is concave towards the object plane; the image-side surface of the fourth lens 104 is concave towards the object plane, and the image-side surface of the fourth lens 104 is concave towards the object plane; the image-side surface of the fifth lens 105 is concave towards the object plane, and the image-side surface of the fifth lens 105 is concave towards the object plane; the image-side surface of the sixth lens 106 is convex towards the object plane, and the image-side surface of the sixth lens 106 is convex towards the object plane; the image-side surface of the seventh lens 107 is convex towards the object plane, and the image-side surface of the seventh lens 107 is concave towards the object plane; the image-side surface of the eighth lens 108 is concave towards the object plane, and the image-side surface of the eighth lens 108 is concave towards the object plane; the image-side surface of the ninth lens 109 is convex towards the object plane.

[0042] For example, optical power is equal to the difference between the image-side beam convergence and the object-side beam convergence, characterizing 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, each lens can be fixed to a single lens barrel (…). Figure 1 (Not shown in the image) Inside the lens, the first lens 101 and the second lens 102 are both negative power lenses, ensuring that the light has a larger aperture before entering the aperture stop 10, thus increasing the lens aperture. The third lens 103, the fourth lens 104, and the fifth lens 105 work together to ensure that the light passes smoothly through the aperture stop 10. The aperture stop 10 is located between the second lens 102 and the third lens 103, avoiding stray light such as reflections at the aperture stop 10 position. At the same time, it can adjust the lens aberrations to a certain extent, ensuring the lens aberration balance and stable high and low temperature performance. Furthermore, the sixth lens 106 and the seventh lens 107, made of materials with different Abbe numbers, can effectively correct chromatic aberration of light passing through the aperture 10, ensuring a clear image at a 1 / 1.8″ aperture. The fourth lens 104, sixth lens 106, and eighth lens 108 are all negative power lenses, which, together with the positive power third lens 103, fifth lens 105, seventh lens 107, and ninth lens 109, form a positive-negative lens combination, effectively eliminating spherical aberration and higher-order aberrations. Simultaneously, in conjunction with the eighth lens 108 and ninth lens 109, residual higher-order aberrations and spherical aberrations can be minimized, increasing the lens aperture while improving image quality to meet the requirements of various applications. For example, as... Figure 1 As shown, by rationally setting the surface shape of each lens, the entire fixed-focus lens structure can be kept compact and the integration of the fixed-focus lens can be ensured.

[0043] In summary, by rationally setting the number of lenses, the surface shape of the lenses, and the relative optical power of each lens in a prime lens, the balance of the incident angles of the front and rear lens groups can be ensured under low cost, reducing lens sensitivity, increasing production feasibility, ensuring high resolution of the prime lens in environments ranging from -40 to 80°C, improving image quality, meeting the requirements of high-definition image quality, and expanding the lens's applicability.

[0044] Optionally, the fifth lens 105 has a refractive index of N5 and an Abbe number of V5; where: 1.43 <N5<1.90,40<V5<94。

[0045] Refractive index is the ratio of the speed of light in a vacuum to the speed of light in a medium, primarily used to describe a material's ability to refract light; different materials have different refractive indices. 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. The fifth lens 105 uses glass, which balances the lens's resolving power under high and low temperatures, and the use of a glass material with a high Abbe number also helps to avert chromatic aberration, preventing excessive chromatic aberration at the rear of the lens from being difficult to correct. Thus, by rationally setting the refractive index and Abbe number of each lens in a fixed-focus lens, it is beneficial to achieve miniaturization of the fixed-focus lens design; at the same time, it is beneficial to achieve higher pixel resolution and a larger aperture.

[0046] Optionally, the first lens 101, the second lens 102, the third lens 103, the fourth lens 104, the sixth lens 106, the seventh lens 107, the eighth lens 108, and the ninth lens 109 are all plastic aspherical lenses, and the fifth lens 105 is a glass spherical lens. 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 invention does not elaborate on or limit the specific materials used. Since the cost of plastic lenses is much lower than that of glass lenses, in the fixed-focus lens provided by this embodiment of the invention, glass and plastic materials can compensate for each other. Using a combination of glass and plastic lenses in the lens can better balance the lens's resolution under high and low temperature conditions. At the same time, using a suitable combination of glass lenses also has a good corrective effect on lens aberrations. Using the above materials can ensure good lens resolution within the range of -40 to 80°C. In addition, the use of glass lenses can correct chromatic aberration of the lens to a great extent. The use of the above-mentioned glass lenses can ensure good resolution under the stated temperature conditions, thus expanding the range of applications of the lens.

[0047] Optionally, the focal length of the first lens 101 is f1, the focal length of the second lens 102 is f2, and the focal length of the optical system is f, where -5.20 < (f1 + f2) / f < -4.70. By appropriately setting the ratio of the focal lengths of the first lens 101 and the second lens 102 to the focal length of the fixed-focus lens, the overall length of the lens can be reduced. This also facilitates aberration correction at very large apertures, ensuring high resolution for the fixed-focus lens. Furthermore, both the first lens 101 and the second lens 102 use plastic aspherical lenses. The combination of the optical power of the first lens 101 and the second lens 102 ensures that the aperture is maximized before light enters the aperture 10, increasing the amount of light entering the optical system at the aperture 10. This allows the optical system to form a clear image even in low-light conditions, expanding the lens's applicable environment.

[0048] Optionally, 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, the focal length of the eighth lens 108 is f8, and the focal length of the ninth lens 109 is f9. The focal length of the optical system is f, where: 2.65 <f3 / f<3.14;-44.58<f4 / f<-8.55;2.19≤f5 / f≤4.04;-4.55<f6 / f<-2.99;1.52<f7 / f<1.73;-2.03<f8 / f<-1.78;1.46<f9 / f<1.56。

[0049] Among them, the third lens 103, the seventh lens 107, and the ninth lens 109 all use plastic aspherical lenses. When light passes through the aperture stop 10 and enters the third lens 103, the seventh lens 107, and the ninth lens 109, the focal lengths of each lens are within this range, which allows the light to converge. This avoids excessive pressure on the other lenses during the correction of chromatic aberration, aberrations, and CRA, preventing them from developing shapes that are difficult to process. In addition, the use of aspherical lenses makes it easier to correct the aforementioned aberrations. The fourth lens 104, the sixth lens 106, and the eighth lens 108 all use plastic aspherical lenses. The reasonable setting of the focal lengths of each lens plays a role in eliminating spherical aberration and higher aberrations. The focal length setting of the fifth lens 105 allows light to pass through the lens more smoothly, greatly correcting the impact of higher aberrations of the lens on image quality. The eighth lens 108 can eliminate higher aberrations and residual spherical aberration that were not eliminated at the front end. Meanwhile, the ninth lens 109 can keep the angle of the principal ray within a suitable range, and can also adjust the height of the intersection point between the principal ray of the maximum field of view and the image plane at the end of the optical system, adapting to a variety of chips, and saving lens costs on the other hand.

[0050] Optionally, the distance from the center of the optical axis on the object side of the first lens 101 to the image plane is TTL, and the lens diameter of the first lens 101 is ΦL1, where: 0.43 < ΦL1 / TTL < 0.45. These conditions effectively control the lens size, allowing for a more compact lens while maximizing the field of view and light intake, thus meeting the demands of more demanding applications.

[0051] Optionally, the aperture number of the fixed-focus lens is F, where 1.0 ≤ F ≤ 1.2. The fixed-focus lens provided in this embodiment of the invention is a large-aperture fixed-focus lens, which meets the requirements of ultra-high data transmission and is suitable for use in more situations.

[0052] Continue to refer to Figure 1 Optionally, the fixed-focus lens also includes an aperture stop 10; the aperture stop 10 is located in the optical path between the second lens 102 and the third lens 103.

[0053] By placing the aperture stop 10 in the optical path between the second lens 102 and the third lens 103, the propagation direction of the light beam can be adjusted, and the incident angle of the light can be adjusted, which is beneficial to improving the imaging quality.

[0054] Furthermore, the fixed-focus lens is also provided with a flat glass 110; the flat glass 110 is located on the image side of the ninth lens 109, and serves to protect the lens and the photosensitive chip in the imaging sensor. The imaging chip is used to convert the light signals collected by the fixed-focus lens into electrical signals, thereby ensuring the imaging effect of the fixed-focus lens.

[0055] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of a fixed-focus lens applicable to the above-described embodiments.

[0056] Example 1

[0057] Continue to refer to Figure 1 The fixed-focus lens provided in Embodiment 1 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, a seventh lens 107, an eighth lens 108, a ninth lens 109, and a flat glass plate 110 arranged sequentially along the optical axis from the object plane to the image plane. The aperture stop 10 is located in the optical path between the second lens 102 and the third lens 103. Table 1 shows the surface shape, radius of curvature, thickness, refractive index, and Abbe number of each lens in the fixed-focus lens provided in Embodiment 1, wherein the units for radius of curvature and thickness are millimeters (mm).

[0058] Table 1 Design values ​​for a fixed-focus lens

[0059]

[0060]

[0061] The surface numbers in Table 1 are assigned according to the surface sequence of each lens. "S1" represents the object side of the first lens 101, "S2" represents the image side of the first lens 101, and so on. "STO" represents the aperture stop 10 of the lens. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image side, and a negative value indicates that the surface bends towards the object side. "INF" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. 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. The Abbe number represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air.

[0062] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations:

[0063]

[0064] Where Z is the axial distance from the vertex of the surface at a position perpendicular to the optical axis at a height r; k is the conic coefficient; c represents the curvature at the vertex of the aspherical surface; a4, a6, a8, a 10 a 12 a 14 a 16 For the higher-order aspheric coefficients corresponding to the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders of aspheric surfaces, a4r 16 These can be combined to form higher-order terms for the corresponding aspherical surfaces.

[0065] For example, Table 2 details the aspherical coefficients of each lens in this embodiment one of feasible implementations.

[0066] Table 2 Aspherical coefficients of a fixed-focus lens

[0067]

[0068]

[0069] Where 1.2340957852E-03 indicates that the coefficient a4 of face number 1 is 1.2340957852 * 10 -3 .

[0070] The fixed-focus lens in this embodiment achieves the following technical specifications: the focal length f is 3.99996mm and the aperture F is 1.08001.

[0071] Figure 2 This is an axial aberration curve diagram of a fixed-focus lens provided in Embodiment 1 of the present invention, as shown below. Figure 2 As shown, the vertical direction represents the normalized aperture, with 0 indicating 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). Different linear curves in the figure represent different wavelengths of system imaging, determined by... Figure 2 It can be seen that the axial aberrations of the normalized apertures of different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm and 0.656μm) from 0 to 1.0 are all controlled within the range of (-0.02mm, +0.02mm), indicating that the spherical aberration of the optical system is well controlled at each wavelength; it can meet the requirements of broadband applications.

[0072] Figure 3 The ray fan pattern of a fixed-focus lens provided in Embodiment 1 of the present invention is as follows: Figure 3As shown, in a single image, the horizontal axis represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should perfectly coincide with the horizontal axis, in which case all rays in that field of view focus at the same point on the image plane; the vertical axis in a single image can also represent the maximum dispersion range of the beam on the ideal image plane. The fan plot can not only reflect monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 3 It can be seen that this optical system closely approximates the horizontal axis at all wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm, and 0.656μm) across all fields of view, indicating that the transverse aberrations at each wavelength are well corrected. Furthermore, the curves for each color do not show significant dispersion, indicating that this optical system also effectively corrects chromatic aberration, ensuring the imaging requirement of sharp images across the entire wavelength range.

[0073] Figure 4 This is a chromatic aberration curve of a fixed-focus lens provided in Embodiment 1 of the present invention, as shown in the figure. Figure 4 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the perpendicular direction represents the maximum pupil radius; the dominant wavelength is 546.074 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (µm). Figure 4 It can be seen that the transverse chromatic aberration of different wavelengths is controlled within a reasonable range, indicating that the transverse chromatic aberration of this fixed-focus lens is well controlled and can meet the requirements of wide-spectrum applications across the entire wavelength range.

[0074] Example 2

[0075] Figure 5 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of the present invention, as shown below. Figure 5 As shown, the fixed-focus lens 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, a seventh lens 207, an eighth lens 208, a ninth lens 209, and a flat glass plate 110 arranged sequentially along the optical axis from the object plane to the image plane. The aperture stop 10 is located in the optical path between the second lens 202 and the third lens 203. Table 3 shows the surface shape, radius of curvature, thickness, refractive index, and Abbe number of each lens in the fixed-focus lens provided in Embodiment 2. The units for radius of curvature and thickness are millimeters (mm).

[0076] Table 3 Design values ​​for a fixed-focus lens

[0077]

[0078]

[0079] The surface numbers in Table 3 are assigned according to the surface sequence of each lens. "S1" represents the object side of the first lens 201, "S2" represents the image side of the first lens 201, and so on. "STO" represents the aperture stop 10 of the lens. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image side, and a negative value indicates that the surface bends towards the object side. "INF" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. 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. The Abbe number represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air.

[0080] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations:

[0081]

[0082] Where Z is the axial distance from the vertex of the surface at a position perpendicular to the optical axis at a height r; k is the conic coefficient; c represents the curvature at the vertex of the aspherical surface; a4, a6, a8, a 10 a 12 a 14 a 16 For the higher-order aspheric coefficients corresponding to the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders of aspheric surfaces, a4r 16 These can be combined to form higher-order terms for the corresponding aspherical surfaces.

[0083] For example, Table 4 details the aspherical coefficients of each lens in this embodiment two according to a feasible implementation.

[0084] Table 4 Aspherical coefficients of a fixed-focus lens

[0085]

[0086]

[0087] Where 1.1539107541E-03 indicates that the coefficient a4 of face number 1 is 1.1539107541 * 10 -3 .

[0088] The fixed-focus lens in this second embodiment achieves the following technical specifications: the focal length f is 3.99996mm and the aperture F is 1.08001.

[0089] Figure 6 This is an axial aberration curve diagram of a fixed-focus lens provided in Embodiment 2 of the present invention, as shown below. Figure 6 As shown, the vertical direction represents the normalized aperture, with 0 indicating 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). Different linear curves in the figure represent different wavelengths of system imaging, determined by... Figure 6 It can be seen that the axial aberrations of the normalized apertures of different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm and 0.656μm) from 0 to 1.0 are all controlled within the range of (-0.02mm, +0.02mm), indicating that the spherical aberration of the optical system is well controlled at each wavelength; it can meet the requirements of broadband applications.

[0090] Figure 7 This is a ray fan pattern of a fixed-focus lens provided in Embodiment 2 of the present invention, such as... Figure 7 As shown, in a single image, the horizontal axis represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should perfectly coincide with the horizontal axis, in which case all rays in that field of view focus at the same point on the image plane; the vertical axis in a single image can also represent the maximum dispersion range of the beam on the ideal image plane. The fan plot can not only reflect monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 7 It can be seen that this optical system closely approximates the horizontal axis at all wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm, and 0.656μm) across all fields of view, indicating that the transverse aberrations at each wavelength are well corrected. Furthermore, the curves for each color do not show significant dispersion, indicating that this optical system also effectively corrects chromatic aberration, ensuring the imaging requirement of sharp images across the entire wavelength range.

[0091] Figure 8 This is a chromatic aberration curve of a fixed-focus lens provided in Embodiment 2 of the present invention, as shown in the figure. Figure 8 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the perpendicular direction represents the maximum pupil radius; the dominant wavelength is 546.074 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (µm). Figure 8 It can be seen that the transverse chromatic aberration of different wavelengths is controlled within a reasonable range, indicating that the transverse chromatic aberration of this fixed-focus lens is well controlled and can meet the requirements of wide-spectrum applications across the entire wavelength range.

[0092] Example 3

[0093] Figure 9 This is a schematic diagram of a fixed-focus lens provided in Embodiment 3 of the present invention, as shown below. Figure 9As shown, the fixed-focus lens includes a first lens 301, a second lens 302, a third lens 303, a fourth lens 304, a fifth lens 305, a sixth lens 306, a seventh lens 307, an eighth lens 308, a ninth lens 309, and a flat glass plate 110 arranged sequentially along the optical axis from the object plane to the image plane. The aperture stop 10 is located in the optical path between the second lens 302 and the third lens 303. Table 5 shows the surface shape, radius of curvature, thickness, refractive index, and Abbe number of each lens in the fixed-focus lens provided in Embodiment 3. The units for radius of curvature and thickness are millimeters (mm).

[0094] Table 5 Design values ​​for a fixed-focus lens

[0095]

[0096]

[0097] The surface numbers in Table 5 are assigned according to the surface sequence of each lens. "S1" represents the object side of the first lens 301, "S2" represents the image side of the first lens 301, and so on. "STO" represents the aperture stop 10 of the lens. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image side, and a negative value indicates that the surface bends towards the object side. "INF" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. 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. The Abbe number represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air.

[0098] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations:

[0099]

[0100] Where Z is the axial distance from the vertex of the surface at a position perpendicular to the optical axis at a height r; k is the conic coefficient; c represents the curvature at the vertex of the aspherical surface; a4, a6, a8, a 10 a 12 a 14 a 16 For the higher-order aspheric coefficients corresponding to the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders of aspheric surfaces, a4r 16 These can be combined to form higher-order terms for the corresponding aspherical surfaces.

[0101] For example, Table 6 details the aspherical coefficients of each lens in this embodiment three according to a feasible implementation.

[0102] Table 6 Aspherical coefficients of a fixed-focus lens

[0103]

[0104]

[0105] Where 1.3729225807E-03 indicates that the coefficient a4 of face number 1 is 1.3729225807 * 10 -3 .

[0106] The fixed-focus lens in this embodiment three achieves the following technical specifications: the focal length f is 3.99996mm and the aperture F is 1.08002.

[0107] Figure 10 This is an axial aberration curve diagram of a fixed-focus lens provided in Embodiment 3 of the present invention, as shown below. Figure 10 As shown, the vertical direction represents the normalized aperture, with 0 indicating 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). Different linear curves in the figure represent different wavelengths of system imaging, determined by... Figure 10 It can be seen that the axial aberrations of the normalized apertures of different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm and 0.656μm) from 0 to 1.0 are all controlled within the range of (-0.02mm, +0.02mm), indicating that the spherical aberration of the optical system is well controlled at each wavelength; it can meet the requirements of broadband applications.

[0108] Figure 11 This is a ray fan pattern of a fixed-focus lens provided in Embodiment 3 of the present invention, such as... Figure 11 As shown, in a single image, the horizontal axis represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should perfectly coincide with the horizontal axis, in which case all rays in that field of view focus at the same point on the image plane; the vertical axis in a single image can also represent the maximum dispersion range of the beam on the ideal image plane. The fan plot can not only reflect monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 11 It can be seen that this optical system closely approximates the horizontal axis at all wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm, and 0.656μm) across all fields of view, indicating that the transverse aberrations at each wavelength are well corrected. Furthermore, the curves for each color do not show significant dispersion, indicating that this optical system also effectively corrects chromatic aberration, ensuring the imaging requirement of sharp images across the entire wavelength range.

[0109] Figure 12This is a chromatic aberration curve of a fixed-focus lens provided in Embodiment 3 of the present invention, as shown in the figure. Figure 12 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the perpendicular direction represents the maximum pupil radius; the dominant wavelength is 546.074 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (µm). Figure 12 It can be seen that the transverse chromatic aberration of different wavelengths is controlled within a reasonable range, indicating that the transverse chromatic aberration of this fixed-focus lens is well controlled and can meet the requirements of wide-spectrum applications across the entire wavelength range.

[0110] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. 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 invention should be included within the scope of protection of this invention.

Claims

1. A fixed-focus lens, characterized in that, The fixed-focus lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged sequentially along the optical axis from the object plane to the image plane. The fixed-focus lens has nine lenses with optical power. 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 first lens, the second lens, the fourth lens, the sixth lens, and the eighth lens are all negative power lenses, while the third lens, the fifth lens, the seventh lens, and the ninth lens are all positive power lenses. The first lens has an object-side surface that convexes towards the object surface and an image-side surface that convexes towards the object surface; the second lens has an object-side surface that is concave towards the object surface and an image-side surface that is concave towards the object surface; the third lens has an object-side surface that convex towards the object surface and an image-side surface that is concave towards the object surface; the fourth lens has an object-side surface that is concave towards the object surface and an image-side surface that is concave towards the object surface; the fifth lens has an object-side surface that is concave towards the object surface and an image-side surface that is concave towards the object surface; the sixth lens has an object-side surface that convex towards the object surface and an image-side surface that convex towards the object surface; the seventh lens has an object-side surface that convex towards the object surface and an image-side surface that is concave towards the object surface; the eighth lens has an object-side surface that is concave towards the object surface and an image-side surface that is concave towards the object surface; and the ninth lens has an object-side surface that convex towards the object surface. 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, the focal length of the eighth lens is f8, the focal length of the ninth lens is f9, and the focal length of the optical system of the fixed-focus lens is f, wherein: 2.65 <f3 / f<3.14;-44.58<f4 / f<-8.55;2.19≤f5 / f≤4.04;-4.55<f6 / f<-2.99;1.52<f7 / f<1.73;-2.03<f8 / f<-1.78;1.46<f9 / f<1.56。 2. The fixed-focus lens according to claim 1, characterized in that, The refractive index of the fifth lens is N5, and the Abbe number is V5; wherein: 1.43 <N5<1.90,40<V5<94。 3. The fixed-focus lens according to claim 1, characterized in that, The focal length of the first lens is f1, and the focal length of the second lens is f2, wherein: -5.20<(f1+f2) / f<-4.

70.

4. 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, and the diameter of the first lens is ΦL1, wherein: 0.43 < ΦL1 / TTL < 0.

45.

5. The fixed-focus lens according to claim 1, characterized in that, The first lens, the second lens, the third lens, the fourth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses, and the fifth lens is a glass spherical lens.

6. The fixed-focus lens according to claim 1, characterized in that, The aperture number of the fixed-focus lens is F, where: 1.0≤F≤1.

2.

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

8. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens is also provided with a flat glass; the flat glass is located on the image side of the ninth lens.

Images