A fixed focus lens

Abstract

The application discloses a fixed focus lens, which comprises eight lenses with optical power, and is sequentially arranged from an object side to an image side along an optical axis with a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a diaphragm, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with negative optical power and an eighth lens with positive optical power; wherein the fourth lens and the fifth lens form a cemented lens group; the first lens, the third lens, the fourth lens, the fifth lens and the sixth lens are all glass spherical lenses, and the second lens, the seventh lens and the eighth lens are all plastic aspherical lenses. The application realizes the optical lens design with a large aperture, a large field of view, a large target surface and a small CRA by arranging five glass spherical lenses and three plastic aspherical lenses into a 5G3P structure and by matching the materials of the eight lenses and distributing the optical power.

Description

Technical Field

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

[0002] In recent years, fixed-focus lenses have been widely used in security, smart home and other fields, and the requirements for large aperture, wide field of view and large target surface of fixed-focus lenses are increasing.

[0003] Large-aperture prime lenses allow for more light intake, making them suitable for a wider range of low-light conditions; a wide field of view ensures a broader shooting range; and lenses adapted to large sensor surfaces produce sharper images, preserving more detail in the subject. However, currently available large-aperture, wide-field-of-view prime lenses are often used with small sensor surfaces, or with large sensor surfaces, wide field of view, and large apertures, which fails to meet the requirements for a small chief ray angle (CRA). Summary of the Invention

[0004] This invention provides a fixed-focus lens that simultaneously meets the requirements of large aperture, wide field of view, large target surface, and small CRA, adapting to the needs of fields such as security and smart furniture.

[0005] This invention provides a fixed-focus lens, comprising eight lenses with optical power, arranged sequentially along the optical axis from object side to image side: a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, an aperture stop, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with negative optical power, and an eighth lens with positive optical power; wherein the fourth lens and the fifth lens form a cemented lens group; The first lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses, while the second lens, the seventh lens, and the eighth lens are all plastic aspherical lenses.

[0006] Optionally, the object-side surface of the first lens is convex, and the image-side surface is concave. The object-side surface of the second lens is concave, and the image-side surface is convex. The object-side surface of the third lens is convex, and the image-side surface is also convex. The object-side surface of the fourth lens is convex, and the image-side surface is also convex. The object-side surface of the fifth lens is concave, and the image-side surface is also concave. The object-side surface of the sixth lens is convex, and the image-side surface is also convex. The object-side surface of the seventh lens is concave, and the image-side surface is convex. The object-side surface of the eighth lens is convex, and the image-side surface is concave. (Spherical lens) Optionally, the fixed-focus lens satisfies the following condition: 1.63≤Nd1≤1.77, 38.8≤Vd1≤50.0; 1.62≤Nd2≤1.89, 20≤Vd2≤29.9; 2.00≤Nd3≤2.09, 21.3≤Vd3≤29.6; 1.56≤Nd4≤1.61, 68.1≤Vd4≤85.3; 1.82≤Nd5≤1.86, 20.1≤Vd5≤23.8; 1.54≤Nd7≤1.72, 28.8≤Vd7≤56.0; 1.62≤Nd8≤1.88, 20.3≤Vd8≤23.0; Wherein Nd1, Nd2, Nd3, Nd5, and Nd7 are the refractive indices of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the seventh lens, and the eighth lens, respectively; and Vd1, Vd2, Vd3, Vd5, and Vd7 are the Abbe numbers of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the seventh lens, and the eighth lens, respectively.

[0007] Optionally, the fixed-focus lens satisfies the following condition: -1.98 <f1 / f<-1.948; -6.081 < f2 / f < -5.441; 2.633 < f3 / f < 2.823; -76.743 <f45 / f<-16.356; 2.394 <f6 / f<2.502; 23.003 <f7 / f<109.092; 12.416 <f8 / f<73.734; Wherein, f1, f2, f3, f6, f7, and f8 are the focal lengths of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, and the eighth lens, respectively, and f45 is the focal length of the cemented lens group composed of the fourth lens and the fifth lens.

[0008] Optionally, the fixed-focus lens satisfies the following condition: 124.888≤(R 11 -R 12 ) / d1≤655.191; 1.144≤(R 21 -R 22 ) / d2≤1.249; 20.149≤(R 31 -R 32 ) / d3≤41.656; 8.596≤(R) 61 -R 62 ) / d6≤11.778; -1.887≤(R 71 -R 72 ) / d7≤-0.503; -0.447≤(R 81 -R 82 ) / d8≤0.299; Among them, R 11 R is the radius of curvature of the object-side surface of the first lens. 12 R is the radius of curvature of the image-side surface of the first lens. 21 R is the radius of curvature of the object-side surface of the second lens. 22 R is the radius of curvature of the image-side surface of the second lens. 31 R is the radius of curvature of the object-side surface of the third lens. 32 R is the radius of curvature of the image-side surface of the third lens. 61 R is the radius of curvature of the object-side surface of the sixth lens. 62 R is the radius of curvature of the image-side surface of the sixth lens. 71 R is the radius of curvature of the object-side surface of the seventh lens. 72 R is the radius of curvature of the image-side surface of the seventh lens. 81 R is the radius of curvature of the object-side surface of the eighth lens. 82 d1, d2, d3, d6, d7, and d8 are the center thicknesses of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, and the eighth lens, respectively.

[0009] Optionally, the fixed-focus lens satisfies the following condition: 3.676≤TTL / IH≤3.926; Wherein, TTL is the total optical length of the fixed-focus lens, and IH is the full-image height of the fixed-focus lens.

[0010] Optionally, the fixed-focus lens satisfies the following condition: 0.07≤BFL / TTL≤0.107; Wherein, TTL is the total optical length of the fixed-focus lens, and BFL is the back focal length of the fixed-focus lens.

[0011] Optionally, the fixed-focus lens satisfies the following condition: 0.371≤Φ1 / TTL≤0.395; 0.276≤Φ1 / Φ8≤0.300; Where Φ1 is the lens diameter of the first lens and Φ8 is the lens diameter of the eighth lens.

[0012] Optionally, the fixed-focus lens satisfies the following condition: 115.791≤FOV / FNO≤126.621; Wherein FOV is the field of view of the fixed-focus lens, and FNO is the aperture number of the fixed-focus lens.

[0013] Optionally, the fixed-focus lens satisfies the following condition: 1.850≤IH / f≤1.888; Where IH is the holographic height of the fixed-focus lens, and f is the total focal length of the fixed-focus lens.

[0014] The fixed-focus lens provided in this invention comprises an optical lens with a 5G3P structure consisting of five glass spherical lenses and three plastic aspherical lenses. Through the material combination and power distribution of these eight lenses, a large aperture, wide field of view, large lens surface, and small chromatic aberration (CRA) are achieved. Specifically, the first, second, and third lenses at the aperture stop are arranged in a negative-negative-positive power combination, which allows light entering the optical system at large angles to smoothly transition to the aperture stop, reducing higher-order chromatic aberrations caused by light from a wide field of view. This combination also achieves a large aperture effect, allowing more light to enter the optical system. Simultaneously, the cemented lens group formed by the fourth and fifth lenses can adjust the large-angle light passing through the aperture stop, reducing higher-order chromatic aberrations introduced by the front lenses. The sixth, seventh, and eighth lenses, arranged in a positive-negative-positive combination, can effectively correct aberrations in the optical system while ensuring sufficient image height. Furthermore, the embodiments of the present invention employ a glass-plastic hybrid lens combination, which can increase the stability of the lens, enabling the lens to maintain sufficiently high resolution at high and low temperatures. At the same time, it can effectively correct lens aberrations, effectively improve the imaging quality of the lens, correct aberrations, and reduce the impact of aberrations on the imaging quality of the lens. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 1 of the present invention; Figure 2 for Figure 1 The image shows the ray fan diagrams of a fixed-focus lens at different field-of-view positions; Figure 3 for Figure 1 The chromatic aberration diagram of the fixed-focus lens shown; Figure 4 for Figure 1 The field curvature distortion diagram of the fixed-focus lens shown; Figure 5 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of the present invention; Figure 6 for Figure 5 The image shows the ray fan diagrams of a fixed-focus lens at different field-of-view positions; Figure 7 for Figure 5 The chromatic aberration diagram of the fixed-focus lens shown; Figure 8 for Figure 5 The field curvature distortion diagram of the fixed-focus lens shown; Figure 9 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 3 of the present invention; Figure 10 for Figure 9 The image shows the ray fan diagram of a fixed-focus lens at different field-of-view positions. Figure 11 for Figure 9 The chromatic aberration diagram of the fixed-focus lens shown; Figure 12 for Figure 9 The field curvature distortion diagram of the fixed-focus lens is shown. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0017] The terminology used in the embodiments of this invention is for the purpose of describing specific embodiments only and is not intended to limit the invention. It should be noted that directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this invention. Furthermore, in the context, it should be understood that when referring to an element being formed "on" or "below" another element, it can be formed not only directly on or below the other element, but also indirectly on or below it through intermediate elements. The terms "first," "second," etc., are used for descriptive purposes only and do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0018] The term "comprising" and its variations as used in this invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment".

[0019] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish the corresponding contents and are not used to limit the order or interdependence.

[0020] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0021] Figure 1 This is a schematic diagram of a fixed-focus lens provided in Embodiment 1 of the present invention, for reference. Figure 1 The fixed-focus lens includes eight lenses with optical power, arranged sequentially from the object side to the image side along the optical axis: a first lens 1 with negative optical power, a second lens 2 with negative optical power, a third lens 3 with positive optical power, an aperture stop STO, a fourth lens 4 with positive optical power, a fifth lens 5 with negative optical power, a sixth lens 6 with positive optical power, a seventh lens 7 with negative optical power, and an eighth lens 8 with positive optical power; wherein, the fourth lens 4 and the fifth lens 5 form a cemented lens group.

[0022] Lens 1, 3, 4, 5, and 6 are all glass spherical lenses, while lens 2, 7, and 8 are all plastic aspherical lenses.

[0023] First, for optical lenses, optical power equals the difference between the image-side beam convergence and the object-side beam convergence; it characterizes the optical system's ability to deflect light. The larger the absolute value of optical power, the stronger the bending ability of light; the smaller the absolute value, the weaker the bending ability. When optical power is positive, the refraction of light is converging; when 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).

[0024] In the fixed-focus lens provided in this embodiment, all lenses can be housed in a single lens barrel. Figure 1 (not shown in the image) such as Figure 1As shown, in this embodiment of the invention, an optical lens is constructed using a 5G3P structure consisting of five glass spherical lenses and three plastic aspherical lenses. Through the material combination and power distribution of these eight lenses, an optical lens design with a large aperture, wide field of view, large target surface, and small chromatic aberration (CRA) is achieved. Specifically, in this embodiment, the first lens 1, the second lens 2, and the third lens 3 at the front of the STO (Side Stop) are arranged in a negative-negative-positive power combination. This allows light entering the optical system at large angles to smoothly transition to the STO, reducing higher-order chromatic aberrations caused by light with a wide field of view. This combination also achieves a large aperture effect, allowing more light to enter the optical system. Simultaneously, the cemented lens group formed by the fourth lens 4 and the fifth lens 5 can adjust the large-angle light passing through the STO, reducing higher-order chromatic aberrations introduced by the front lenses. The sixth lens 6, the seventh lens 7, and the eighth lens 8 are arranged in a positive-negative-positive combination, effectively correcting aberrations in the optical system while ensuring sufficient image height.

[0025] Furthermore, this embodiment of the invention employs a glass-plastic hybrid lens combination. The first lens 1 uses a glass lens, which increases lens stability. The use of glass lenses for the first lens 1, third lens 3, and sixth lens 6 enables the lens to maintain sufficiently high resolution at both high and low temperatures, thus coping with harsher environments. The remaining lenses use aspherical lenses, which effectively correct lens aberrations, improve image quality, and reduce the impact of aberrations on image quality.

[0026] In summary, the technical solution of the above embodiment, which consists of 8 lenses and a flat glass of a certain thickness, can achieve an aperture of F1.1 and a CRA of less than 11° for a fixed-focus lens when paired with a 1 / 1.2″ chip and meeting the processing conditions, thus fulfilling the requirements of large target area, large field of view, large aperture and high resolution.

[0027] In one optional embodiment, the object-side surface of the first lens 1 is convex and the image-side surface is concave; the object-side surface of the second lens 2 is concave and the image-side surface is convex; the object-side surface of the third lens 3 is convex and the image-side surface is convex; the object-side surface of the fourth lens 4 is convex and the image-side surface is convex; the object-side surface of the fifth lens 5 is concave and the image-side surface is concave; the object-side surface of the sixth lens 6 is convex and the image-side surface is convex; the object-side surface of the seventh lens 7 is concave and the image-side surface is convex; and the object-side surface of the eighth lens 8 is convex and the image-side surface is concave.

[0028] In an optional embodiment, the fixed-focus lens satisfies the following conditions: 1.63≤Nd1≤1.77, 38.8≤Vd1≤50.0; 1.62≤Nd2≤1.89, 20≤Vd2≤29.9; 2.00≤Nd3≤2.09, 21.3≤Vd3≤29.6; 1.56≤Nd4≤1.61, 68.1≤Vd4≤85.3; 1.82≤Nd5≤1.86, 20.1≤Vd5≤23.8; 1.54≤Nd7≤1.72, 28.8≤Vd7≤56.0; 1.62≤Nd8≤1.88, 20.3≤Vd8≤23.0; wherein Nd1, Nd2, Nd3, Nd5, Nd7 are respectively the refractive indices of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the seventh lens 7, and the eighth lens 8; Vd1, Vd2, Vd3, Vd5, Vd7 are respectively the Abbe numbers of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the seventh lens 7, and the eighth lens 8.

[0029] Wherein, the refractive index is the ratio of the propagation speed of light in vacuum to the propagation speed of light in the medium, which is mainly used to describe the light refraction capability of a material, and different materials have different refractive indices. The Abbe constant is an index used to represent the dispersion capability of a transparent medium. The more severe the dispersion of the medium, the smaller the Abbe constant; conversely, the milder the dispersion of the medium, the larger the Abbe constant. In the embodiment of the present invention, the fourth lens 4 is made of a glass material with a high Abbe number, which can effectively reduce chromatic aberration in the optical system and improve imaging quality, while the second lens 2, the third lens 3, the fifth lens 5, and the eighth lens 8 are made of plastic materials with high refractive indices, which can effectively compress the total length and volume of the lens, and prevent the total length from being excessively large while meeting high image quality requirements.

[0030] In an optional embodiment, the fixed-focus lens satisfies the following conditions: -1.98<f1 / f<-1.948; -6.081< f2 / f<-5.441; 2.633<f3 / f<2.823; -76.743<f45 / f<-16.356; 2.394<f6 / f<2.502; 23.003<f7 / f<109.092; 12.416<f8 / f<73.734; wherein f1, f2, f3, f6, f7, f8 are respectively the focal lengths of the first lens 1, the second lens 2, the third lens 3, the sixth lens 6, the seventh lens 7, and the eighth lens 8, and f45 is the focal length of the cemented lens group composed of the fourth lens 4 and the fifth lens 5.

[0031] Focal length characterizes the ability of an optical system to deflect light. A larger absolute value of the focal length indicates a weaker ability to bend light, while a smaller absolute value indicates a stronger ability to bend light. When the focal length is positive, the refraction of light is converging; when the focal length is negative, the refraction of light is diverging. In this embodiment, by limiting the focal lengths of different lenses in the optical system, the focal lengths of the optical system can be rationally allocated, reducing the tolerance sensitivity of the optical system, effectively improving the imaging quality of the optical system, and also improving production yield to a certain extent.

[0032] In an alternative embodiment, the fixed-focus lens satisfies the following condition: 124.888 ≤ (R 11 -R 12 ) / d1≤655.191; 1.144≤(R 21 -R 22 ) / d2≤1.249; 20.149≤(R 31 -R 32 ) / d3≤41.656; 8.596≤(R 61 -R 62 ) / d6≤11.778; -1.887≤(R 71 -R 72 ) / d7≤-0.503; -0.447≤(R 81 -R 82 ) / d8≤0.299; where, R 11 R is the radius of curvature of the object-side surface of the first lens 1. 12 R is the radius of curvature of the image-side surface of the first lens 1. 21 R is the radius of curvature of the object-side surface of the second lens 2. 22 R is the radius of curvature of the image-side surface of the second lens 2. 31 R is the radius of curvature of the object-side surface of the third lens 3. 32 R is the radius of curvature of the image-side surface of the third lens 3. 61 R is the radius of curvature of the object-side surface of the sixth lens 6. 62 R is the radius of curvature of the image-side surface of the sixth lens 6. 71 R is the radius of curvature of the object-side surface of the seventh lens 7. 72 R is the radius of curvature of the image-side surface of the seventh lens 7. 81 R is the radius of curvature of the object-side surface of the eighth lens 8. 82 d1, d2, d3, d6, d7, and d8 are the center thicknesses of the first lens 1, the second lens 2, the third lens 3, the sixth lens 6, the seventh lens 7, and the eighth lens 8, respectively.

[0033] In this embodiment, by limiting the ratio of the curvature radius of each lens to the center thickness of the lens, the processing capability of the lens can be ensured, the processing difficulty of the lens can be reduced, and the mass production capability of the lens can be increased. At the same time, this ratio of the curvature radius to the center thickness of the front and rear lenses of the lens can ensure that the light entering the optical system and the light exiting the image plane can be smooth, thereby enhancing the imaging capability of the lens.

[0034] In an optional embodiment, the fixed-focus lens satisfies the following condition: 3.676≤TTL / IH≤3.926; where TTL is the total optical length of the fixed-focus lens and IH is the full-image height of the fixed-focus lens.

[0035] By limiting the ratio of the total lens length to the image height, it can be ensured that the lens can achieve a larger image area for the same total length while meeting the requirements, thus ensuring a balance between lens volume and image area.

[0036] In an optional embodiment, the fixed-focus lens satisfies the following condition: 0.07≤BFL / TTL≤0.107; where TTL is the total optical length of the fixed-focus lens and BFL is the back focal length of the fixed-focus lens.

[0037] By limiting the ratio of total optical length to back focal length, the lens can meet the focal length requirements while ensuring sufficient installation space between the imaging sensor and the flat filter 9. This ensures that the lens will not interfere with the base and housing during installation, thus simplifying the manufacturing process of the industrial lens.

[0038] In an optional embodiment, the fixed-focus lens satisfies the following conditions: 0.371≤Φ1 / TTL≤0.395; 0.276≤Φ1 / Φ8≤0.300; where Φ1 is the lens diameter of the first lens 1 and Φ8 is the lens diameter of the eighth lens 8.

[0039] By limiting the ratio of the front and rear port diameters of the lens to the total length of the lens, the requirements for a small lens size and short total length can be met. At the same time, limiting the front and rear port diameters of the lens can allow for the adjustment of light entering the optical system at a large field of view, thereby further satisfying the requirements for a small lens size and short total length on the basis of a large field of view.

[0040] In an optional embodiment, the fixed-focus lens satisfies the following condition: 115.791≤FOV / FNO≤126.621; where FOV is the field of view of the fixed-focus lens and FNO is the aperture number of the fixed-focus lens.

[0041] By limiting the ratio of the lens's field of view to its aperture, sufficient light can be passed through the lens, enabling it to capture light across a large field of view and ensure good image quality.

[0042] In an optional embodiment, the fixed-focus lens satisfies the following condition: 1.850≤IH / f≤1.888; where IH is the full-image height of the fixed-focus lens and f is the total focal length of the fixed-focus lens.

[0043] By limiting the ratio of the lens's holographic height to its focal length, it is possible to ensure that the lens's holographic height and focal length have a reasonable range, which is beneficial for the lens to have a larger image plane and better image quality.

[0044] Based on the same inventive concept, this invention provides three different specific embodiments, the optical power relationship and related physical and optical parameter design ranges of which are shown in Table 1: Table 1. Optical power relationship of each lens and design values ​​of related physical and optical parameters in the three embodiments. In Embodiment 1 of the present invention, reference is made to Figure 1 The structure, shape, and location of each component in the system are known, which is crucial for the system. As shown in the figure, the optical lens consists of five glass spherical lenses and three plastic aspherical lenses, with the aperture stop STO located between the third lens 3 and the fourth lens 4. A filter 9 is also positioned along the object plane to the image plane; filter 9 is located on the image-side surface of the eighth lens 8, and it protects the photosensitive chip in the imaging sensor. (As shown...) Figure 1 The parameter design values ​​of each lens in the fixed-focus lens of Embodiment 1 are shown in Table 2: Table 2. Design values ​​for each lens in the fixed-focus lens in Example 1 The surface numbers in Table 2 are assigned according to the surface sequence of each lens. "STOP" represents the aperture stop of the optical system; 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. "INF" indicates that the surface is flat and has an infinite radius of curvature; 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 even-order coefficients of each aspherical surface in the above embodiment 1 are shown in Table 3: Table 3. Even-order term coefficients for each aspherical surface in Example 1 Where -2.38E-04 indicates that the coefficient A of surface number S3 is -2.38 × 10⁻⁴. -4 And so on.

[0045] The value of k represents the magnitude of the conicity coefficient of the aspherical surface. The conicity coefficient of an aspherical surface can be defined using the following aspherical formula, but is not limited to the following representations: ; 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.

[0046] The parameter specifications of the fixed-focus lens in the above embodiment one are shown in Table 4: Table 4. Parameter specifications of the fixed-focus lens in Example 1 Figure 2 for Figure 1 The diagram shows the ray fan plots of a fixed-focus lens at different fields of view. The ray fan plot is one of the most commonly used evaluation methods in modern optical design. In the diagram, the horizontal axis of a single image represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should completely coincide with the horizontal axis, at which point all rays in that field of view should 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 ray fan plot can reflect not only monochromatic aberrations at different wavelengths but also the magnitude of transverse chromatic aberration. Figure 2 It can be seen that the optical system closely approximates the horizontal axis at each wavelength in each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.

[0047] Figure 3 for Figure 1 The diagram shows the transverse chromatic aberration of a fixed-focus lens. In the diagram, the vertical direction represents the field of view, 0 indicates being on the optical axis, and the vertex in the transverse direction represents the maximum field of view. The dominant wavelength is 546nm, and the horizontal direction represents the offset relative to the image plane, in micrometers (µm). Figure 3 It can be seen that the transverse chromatic aberration of different wavelengths is controlled within a small range, indicating that the transverse chromatic aberration of this fixed-focus lens is well controlled at the fixed-focus end, which can meet the requirements of wide-spectrum applications.

[0048] Figure 4 for Figure 1 The diagram shows the field curvature distortion of a fixed-focus lens. In the left-hand coordinate system, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height (unitless); where T represents meridion and S represents arc distortion. Figure 4 It can be seen that the lens provided in this embodiment is effectively controlled in terms of field curvature, that is, during imaging, the difference between the image quality in the center and the image quality in the periphery is small; in the coordinate system on the right, the horizontal coordinate represents the magnitude of distortion, in %; the vertical coordinate represents the normalized image height, which has no unit.

[0049] Figure 5 This is a schematic diagram of a fixed-focus lens provided in Embodiment 2 of the present invention, for reference. Figure 5 In Embodiment 2 of the present invention, reference is made to Figure 5 The structure, shape, and location of each component in the system are known, which is crucial for the system. As shown in the figure, the optical lens consists of five glass spherical lenses and three plastic aspherical lenses, with the aperture stop STO located between the third lens 3 and the fourth lens 4. A filter 9 is also positioned along the object plane to the image plane; filter 9 is located on the image-side surface of the eighth lens 8, and it protects the photosensitive chip in the imaging sensor. (As shown...) Figure 5 The parameter design values ​​of each lens in the fixed-focus lens of Embodiment 2 are shown in Table 5: Table 5. Design values ​​for each lens in the fixed-focus lens in Example 2 The surface numbers in Table 5 are assigned according to the surface sequence of each lens. "STOP" represents the aperture stop of the optical system; the radius of curvature represents the degree of curvature of the lens surface, with positive values ​​indicating the surface bends towards the image plane and negative values ​​indicating the surface bends towards the object plane. "INF" indicates that the surface is planar with an infinite radius of curvature; thickness represents the central axial distance between the current surface and the next surface; refractive index represents the ability of the material between the current and next surfaces to deflect light; a blank space indicates that the current position is air with a refractive index of 1. The even-order coefficients of each aspherical surface in the above embodiment two are shown in Table 6. Table 6. Even-order term coefficients for each aspherical surface in Example 2 Where -2.3719E-04 indicates that the coefficient A of surface number S3 is -2.3719 × 10 -4 And so on.

[0050] The value of k represents the magnitude of the conicity coefficient of the aspherical surface. The conicity coefficient of an aspherical surface can be defined using the following aspherical formula, but is not limited to the following representations: ; 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.

[0051] The parameter specifications of the fixed-focus lens in the above embodiment two are shown in Table 7: Table 7. Parameter specifications of the fixed-focus lens in Example 2 Figure 6 for Figure 5 The diagram shows the ray fan plots of a fixed-focus lens at different fields of view. The ray fan plot is one of the most commonly used evaluation methods in modern optical design. In the diagram, the horizontal axis of a single image represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should completely coincide with the horizontal axis, at which point all rays in that field of view should 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 ray fan plot can reflect not only monochromatic aberrations at different wavelengths but also the magnitude of transverse chromatic aberration. Figure 6 It can be seen that the optical system closely approximates the horizontal axis at each wavelength in each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.

[0052] Figure 7 for Figure 5 The diagram shows the transverse chromatic aberration of a fixed-focus lens. In the diagram, the vertical direction represents the field of view, 0 indicates being on the optical axis, and the vertex in the transverse direction represents the maximum field of view. The dominant wavelength is 546nm, and the horizontal direction represents the offset relative to the image plane, in micrometers (µm). Figure 7 It can be seen that the transverse chromatic aberration of different wavelengths is controlled within a small range, indicating that the transverse chromatic aberration of this fixed-focus lens is well controlled at the fixed-focus end, which can meet the requirements of wide-spectrum applications.

[0053] Figure 8 for Figure 5 The diagram shows the field curvature distortion of a fixed-focus lens. In the left-hand coordinate system, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height (unitless); where T represents meridion and S represents arc distortion. Figure 8 It can be seen that the lens provided in this embodiment is effectively controlled in terms of field curvature, that is, during imaging, the difference between the image quality in the center and the image quality in the periphery is small; in the coordinate system on the right, the horizontal coordinate represents the magnitude of distortion, in %; the vertical coordinate represents the normalized image height, which has no unit.

[0054] Figure 9 This is a schematic diagram of a fixed-focus lens provided in Embodiment 3 of the present invention, for reference. Figure 9 In Embodiment 3 of the present invention, reference is made to Figure 9The structure, shape, and location of each component in the system are known, which is crucial for the system. As shown in the figure, the optical lens consists of five glass spherical lenses and three plastic aspherical lenses, with the aperture stop STO located between the third lens 3 and the fourth lens 4. A filter 9 is also positioned along the object plane to the image plane; filter 9 is located on the image-side surface of the eighth lens 8, and it protects the photosensitive chip in the imaging sensor. (As shown...) Figure 9 The parameter design values ​​of each lens in the fixed-focus lens of Embodiment 3 are shown in Table 8: Table 8. Design values ​​for each lens in the fixed-focus lens in Example 3 The surface numbers in Table 8 are assigned according to the surface sequence of each lens. "STOP" represents the aperture stop of the optical system; 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. "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 even-order coefficients of each aspherical surface in the above embodiment three are shown in Table 9: Table 9. Even-order term coefficients for each aspherical surface in Example 3 Where -2.5713E-04 indicates that the coefficient A of surface number S3 is -2.5713 × 10⁻⁴. -4 And so on.

[0055] The value of k represents the magnitude of the conicity coefficient of the aspherical surface. The conicity coefficient of an aspherical surface can be defined using the following aspherical formula, but is not limited to the following representations: ; 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] The parameter specifications of the fixed-focus lens in Embodiment 3 above are shown in Table 10: Table 10 Parameter Specifications of the Fixed-Focus Lens in Example 3 Figure 10 for Figure 9The diagram shows the ray fan plots of a fixed-focus lens at different fields of view. The ray fan plot is one of the most commonly used evaluation methods in modern optical design. In the diagram, the horizontal axis of a single image represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should completely coincide with the horizontal axis, at which point all rays in that field of view should 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 ray fan plot can reflect not only monochromatic aberrations at different wavelengths but also the magnitude of transverse chromatic aberration. Figure 10 It can be seen that the optical system closely approximates the horizontal axis at each wavelength in each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.

[0057] Figure 11 for Figure 9 The diagram shows the transverse chromatic aberration of a fixed-focus lens. In the diagram, the vertical direction represents the field of view, 0 indicates being on the optical axis, and the vertex in the transverse direction represents the maximum field of view. The dominant wavelength is 546nm, and the horizontal direction represents the offset relative to the image plane, in micrometers (µm). Figure 11 It can be seen that the transverse chromatic aberration of different wavelengths is controlled within a small range, indicating that the transverse chromatic aberration of this fixed-focus lens is well controlled at the fixed-focus end, which can meet the requirements of wide-spectrum applications.

[0058] Figure 12 for Figure 9 The diagram shows the field curvature distortion of a fixed-focus lens. In the left-hand coordinate system, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height (unitless); where T represents meridion and S represents arc distortion. Figure 12 It can be seen that the lens provided in this embodiment is effectively controlled in terms of field curvature, that is, during imaging, the difference between the image quality in the center and the image quality in the periphery is small; in the coordinate system on the right, the horizontal coordinate represents the magnitude of distortion, in %; the vertical coordinate represents the normalized image height, which has no unit.

[0059] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A fixed-focus lens, characterized in that, It includes eight lenses with optical power, arranged sequentially 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 third lens with positive optical power, an aperture, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with negative optical power, and an eighth lens with positive optical power; wherein the fourth lens and the fifth lens form a cemented lens group; The first lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses, while the second lens, the seventh lens, and the eighth lens are all plastic aspherical lenses.

2. The fixed-focus lens according to claim 1, characterized in that, The object-side surface of the first lens is convex, and the image-side surface is concave. The object-side surface of the second lens is concave, and the image-side surface is convex. The object-side surface of the third lens is convex, and the image-side surface is also convex. The object-side surface of the fourth lens is convex, and the image-side surface is also convex. The object-side surface of the fifth lens is concave, and the image-side surface is also concave. The object-side surface of the sixth lens is convex, and the image-side surface is also convex. The object-side surface of the seventh lens is concave, and the image-side surface is convex. The object-side surface of the eighth lens is convex, and the image-side surface is concave.

3. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens meets the following conditions: 1.63≤Nd1≤1.77, 38.8≤Vd1≤50.0; 1.62≤Nd2≤1.89, 20≤Vd2≤29.9; 2.00≤Nd3≤2.09, 21.3≤Vd3≤29.6; 1.56≤Nd4≤1.61, 68.1≤Vd4≤85.3; 1.82≤Nd5≤1.86, 20.1≤Vd5≤23.8; 1.54≤Nd7≤1.72, 28.8≤Vd7≤56.0; 1.62≤Nd8≤1.88, 20.3≤Vd8≤23.0; Wherein Nd1, Nd2, Nd3, Nd5, and Nd7 are the refractive indices of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the seventh lens, and the eighth lens, respectively; and Vd1, Vd2, Vd3, Vd5, and Vd7 are the Abbe numbers of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the seventh lens, and the eighth lens, respectively.

4. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens meets the following conditions: -1.98 <f1 / f<-1.948; -6.081 < f2 / f < -5.441; 2.633 < f3 / f < 2.823; -76.743 <f45 / f<-16.356; 2.394 <f6 / f<2.502; 23.003 <f7 / f<109.092; 12.416 <f8 / f<73.734; Wherein, f1, f2, f3, f6, f7, and f8 are the focal lengths of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, and the eighth lens, respectively, and f45 is the focal length of the cemented lens group composed of the fourth lens and the fifth lens.

5. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens meets the following conditions: 124.888≤(R 11 -R 12 ) / d1≤655.191; 1.144≤(R 21 -R 22 ) / d2≤1.249; 20.149≤(R 31 -R 32 ) / d3≤41.656; 8.596≤(R 61 -R 62 ) / d6≤11.778; -1.887≤(R 71 -R 72 ) / d7≤-0.503; -0.447≤(R 81 -R 82 ) / d8≤0.299; Among them, R 11 R is the radius of curvature of the object-side surface of the first lens. 12 R is the radius of curvature of the image-side surface of the first lens. 21 R is the radius of curvature of the object-side surface of the second lens. 22 R is the radius of curvature of the image-side surface of the second lens. 31 R is the radius of curvature of the object-side surface of the third lens. 32 R is the radius of curvature of the image-side surface of the third lens. 61 R is the radius of curvature of the object-side surface of the sixth lens. 62 R is the radius of curvature of the image-side surface of the sixth lens. 71 R is the radius of curvature of the object-side surface of the seventh lens. 72 R is the radius of curvature of the image-side surface of the seventh lens. 81 R is the radius of curvature of the object-side surface of the eighth lens. 82 d1, d2, d3, d6, d7, and d8 are the center thicknesses of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, and the eighth lens, respectively.

6. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens meets the following conditions: 3.676≤TTL / IH≤3.926; Wherein, TTL is the total optical length of the fixed-focus lens, and IH is the holographic height of the fixed-focus lens.

7. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens meets the following conditions: 0.07≤BFL / TTL≤0.107; Wherein, TTL is the total optical length of the fixed-focus lens, and BFL is the back focal length of the fixed-focus lens.

8. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens meets the following conditions: 0.371≤Φ1 / TTL≤0.395; 0.276≤Φ1 / Φ8≤0.300; Where Φ1 is the lens diameter of the first lens and Φ8 is the lens diameter of the eighth lens.

9. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens meets the following conditions: 115.791≤FOV / FNO≤126.621; Wherein FOV is the field of view of the fixed-focus lens, and FNO is the aperture number of the fixed-focus lens.

10. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens meets the following conditions: 1.850≤IH / f≤1.888; Where IH is the holographic height of the fixed-focus lens, and f is the total focal length of the fixed-focus lens.

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