Prime lens

Abstract

The prime lens comprises a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens which are sequentially arranged from an object space to an image space along an optical axis, the first lens is a glass spherical lens with negative focal power, the second lens is a plastic aspheric lens, the third lens is a plastic aspheric lens with positive focal power, the fourth lens is a plastic aspheric lens with positive focal power, the fifth lens is a plastic aspheric lens with negative focal power, and the sixth lens is a plastic aspheric lens with negative focal power. The sixth lens is a plastic aspheric lens with positive focal power, the seventh lens is a plastic aspheric lens with negative focal power, the eighth lens is a plastic aspheric lens with positive focal power, and the ninth lens is a plastic aspheric lens. According to the invention, a 1G8P lens combination is adopted, the low-cost and large-view-field-range lens design which gives consideration to the imaging requirement and the compact structure is realized, and the security and protection monitoring universality requirement can be met.

Description

Technical Field

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

[0002] As a mainstream product in the security industry, fixed-focus lenses are popular in the market demand. The 1 / 2.7″ chip is more and more widely used, and the requirements for the volume, field of view range and usage environment of the lenses matched with it are becoming more and more strict. At present, it is difficult for the mainstream optical lenses in the market to balance small volume, large field of view range and good resolution from the center to the edge, which is not conducive to the use and promotion of products. Summary of the Invention

[0003] The present invention provides a fixed-focus lens, which is designed to complete a fixed-focus lens with low cost, large field of view range that兼顾成像要求和结构紧凑 by combining one glass spherical lens and eight plastic aspherical lenses.

[0004] The embodiments of the present invention provide a fixed-focus lens, including a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged in sequence from the object side to the image side along the optical axis;

[0005] The first lens is a glass spherical lens with negative optical power, the second lens is a plastic aspherical lens, the third lens is a plastic aspherical lens with positive optical power, the fourth lens is a plastic aspherical lens with positive optical power, the fifth lens is a plastic aspherical lens with negative optical power, the sixth lens is a plastic aspherical lens with positive optical power, the seventh lens is a plastic aspherical lens with negative optical power, the eighth lens is a plastic aspherical lens with positive optical power, and the ninth lens is a plastic aspherical lens.

[0006] Optionally, the first lens satisfies the following conditions: 1.77 < Nd1 < 2.06, 26.9 < Vd1 < 49.7; where, Nd1 is the refractive index of the first lens, and Vd1 is the Abbe number of the first lens.

[0007] Optionally, the first lens and the second lens satisfy the following conditions: -0.35 < Φ1 + Φ2 < -0.22; where, Φ1 is the optical power of the first lens, and Φ2 is the optical power of the second lens.

[0008] Optionally, the third lens satisfies the following conditions: 0.11 < Φ3 < 0.13; where, Φ3 is the optical power of the third lens.

[0009] Optionally, the fourth lens and the fifth lens satisfy the following condition: 0.13 < Φ4 + Φ5 < 0.17; where Φ4 is the optical power of the fourth lens and Φ5 is the optical power of the fifth lens.

[0010] Optionally, the sixth lens satisfies the following condition: 0.04 < Φ6 + Φ7 < 0.07; where Φ6 is the optical power of the sixth lens and Φ7 is the optical power of the seventh lens.

[0011] Optionally, the eighth lens and the ninth lens satisfy the following condition: 0.07 < Φ8 + Φ9 < 0.35; where Φ8 is the optical power of the eighth lens and Φ9 is the optical power of the ninth lens.

[0012] Optionally, the fixed-focus lens satisfies the following condition: 2.04 < F / # < 2.156; where F represents the f-number of the fixed-focus lens.

[0013] Optionally, the fixed-focus lens satisfies the following condition: 1.520 < H / f < 1.524; where f is the focal length of the fixed-focus lens; H is the vertical height of the intersection point of the chief ray of the maximum field of view of the fixed-focus lens and the image plane.

[0014] Optionally, the fixed-focus lens satisfies the following condition: 0.08 < BFL / TTL < 0.10; where BFL is the distance from the vertex of the image side of the ninth lens to the image plane, and TTL is the total optical system length of the fixed-focus lens.

[0015] The technical solution provided by the embodiment of the present invention adopts a hybrid combination of 1 glass spherical lens and 8 plastic aspherical lenses. By optimizing the optical power matching and relative positions of each lens element, it can well correct aberrations, ensure good enough image quality, and has a low cost. Thus, a low-cost fixed-focus lens design that兼顾成像要求和结构紧凑的大视场范围 is obtained. This fixed-focus lens can be paired with a 5MP / 4K, 1 / 2.7-inch type chip, meeting the requirements of small volume, large field of view range, and good resolution from the center to the edge. The comprehensive performance can meet the usage requirements of general-purpose chips for security monitoring, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0017] Figures 2A to 2F is [[ID=2)]] Figure 1 the light fan diagram of the light rays of the shown fixed-focus lens at different field positions;

[0018] Figure 3 is Figure 1 the axial chromatic aberration curve diagram of the shown fixed-focus lens;

[0019] Figure 4 for Figure 1 The chromatic aberration diagram of the fixed-focus lens shown;

[0020] Figure 5 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0021] Figures 6A to 6F for Figure 5 The image shows the ray fan diagrams of a fixed-focus lens at different field-of-view positions;

[0022] Figure 7 for Figure 5 The axial chromatic aberration curve of the fixed-focus lens is shown.

[0023] Figure 8 for Figure 5 The chromatic aberration diagram of the fixed-focus lens shown;

[0024] Figure 9 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0025] Figures 10A to 10F for Figure 9 The image shows the ray fan diagrams of a fixed-focus lens at different field-of-view positions;

[0026] Figure 11 for Figure 9 The axial chromatic aberration curve of the fixed-focus lens is shown.

[0027] Figure 12 for Figure 9 The diagram shows the chromatic aberration along the vertical axis of the fixed-focus lens. Detailed Implementation

[0028] 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.

[0029] 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.

[0030] 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".

[0031] 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.

[0032] 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".

[0033] 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 a first lens, a second lens, a third lens, an aperture stop, 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 side to the image side.

[0034] The first lens is a glass spherical lens with negative optical power; the second lens is a plastic aspherical lens; the third lens is a plastic aspherical lens with positive optical power; the fourth lens is a plastic aspherical lens with positive optical power; the fifth lens is a plastic aspherical lens with negative optical power; the sixth lens is a plastic aspherical lens with positive optical power; the seventh lens is a plastic aspherical lens with negative optical power; the eighth lens is a plastic aspherical lens with positive optical power; and the ninth lens is a plastic aspherical lens.

[0035] 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).

[0036] 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 1 As shown, in this embodiment of the invention, an optical lens is constructed using a 1G8P structure consisting of a glass spherical lens and eight plastic aspherical lenses. Through the material combination and power distribution of these eight lenses, a small-volume, large-field-of-view, and center-to-edge resolution optical lens design is achieved. Specifically, the first lens has a negative power and can be paired with the second lens to increase the incident light angle and achieve a large field of view. The third lens is set to positive power to adjust the incident light angle, facilitating smooth entry of light into the aperture. The fourth and fifth lenses, as well as the sixth and seventh lenses, use a combination of positive and negative power, primarily responsible for balancing chromatic aberration and correcting field curvature and distortion, thus correcting various aberrations. The eighth lens, with positive power, is paired with the ninth lens to correct aberrations and ensure that the main ray is incident on the sensor at the most perpendicular angle possible, optimizing telecentricity. As can be seen from the above, the fixed-focus lens of the present invention, through the combination of the optical power of the above nine lenses, can effectively correct various aberrations, ensure image quality, improve the resolution from the center to the edge, and at the same time ensure a compact structure, achieving a large field of view and miniaturization.

[0037] It should also be emphasized that the fixed-focus lens provided in this embodiment of the invention, in addition to utilizing the optical power, mainly relies on the design of the lens material and surface shape. Of the nine lenses, only the first lens 1 is a glass spherical lens. This utilizes the high refractive index and low dispersion characteristics of glass to ensure that light rays at large angles can enter the optical system, guaranteeing clear imaging while achieving a large field of view and a large aperture. Simultaneously, the remaining eight lenses are made of plastic aspherical surfaces. Aspherical surfaces are used for aberration correction, improving image resolution and maximizing image quality. Furthermore, the relatively low difficulty in manufacturing aspherical surfaces using plastic materials significantly reduces the overall manufacturing cost of the lens. Thus, it achieves a balance of low cost, large field of view, and high image quality, meeting the design requirements of fixed-focus lenses in the security field.

[0038] In summary, the technical solution of the above embodiments adopts a hybrid combination of 1 glass spherical lens and 8 plastic aspherical lenses. By optimizing the power distribution and relative positions of each lens element, it can well correct aberrations, ensure good enough image quality, and has a relatively low cost. Thus, a fixed-focus lens design with a large field of view that takes into account imaging requirements and structural compactness and low cost is obtained. This fixed-focus lens can be paired with a 5MP / 4K, 1 / 2.7-inch type of chip, meeting the requirements of small volume, large field of view, and good resolution from the center to the edge. The comprehensive performance can meet the usage requirements of general-purpose chips for security monitoring, and has a wide range of applications.

[0039] Specifically, in the embodiments of the present invention, the first lens is a convex-concave lens, the second lens is a convex-concave lens, the third lens is a concave-convex lens, the fourth lens is a lens with a convex surface on the image side, the fifth lens is a convex-concave lens, the sixth lens is a double convex lens, the seventh lens is a lens with a concave surface on the object side, the eighth lens is a concave-convex lens, and the ninth lens is a convex-concave lens.

[0040] In a specific embodiment, optionally, the first lens satisfies the following conditions: 1.77 < Nd1 < 2.06, 26.9 < Vd1 < 49.7; where Nd1 is the refractive index of the first lens and Vd1 is the Abbe number of the first lens.

[0041] It can be understood that using a high-refractive-index material for the first lens in this embodiment can significantly reduce the size and weight of the optical system. In other words, on the premise of providing the same optical power, lens surfaces with smaller curvatures can be used. In addition, using a high-refractive-index material for the first lens can effectively control the extreme aberrations brought by a large field angle, which helps to achieve a more compact and higher imaging quality lens design.

[0042] In a specific embodiment, optionally, the first lens and the second lens satisfy the following conditions: -0.35 < Φ1 + Φ2 < -0.22; where Φ1 is the optical power of the first lens and Φ2 is the optical power of the second lens.

[0043] It can be understood that in this specific embodiment, by restricting the optical powers of the first lens and the second lens to meet the above matching requirements, it can maximize the acceptance of large-angle light rays and refract them into the interior of the lens, which helps to achieve a large field angle.

[0044] In a specific embodiment, optionally, the third lens satisfies the following conditions: 0.11 < Φ3 < 0.13; where Φ3 is the optical power of the third lens.

[0045] It can be understood that in this specific embodiment, by limiting the optical power of the third lens in the front-middle position, that is, restricting its light refraction ability, the third lens can play a connecting role, ensuring that light can pass through the aperture smoothly and symmetrically, which plays an important role in controlling aberrations.

[0046] In a specific embodiment, optionally, the fourth lens and the fifth lens satisfy the following condition: 0.13 < Φ4 + Φ5 < 0.17; where Φ4 is the optical power of the fourth lens and Φ5 is the optical power of the fifth lens.

[0047] It can be understood that in this specific embodiment, by restricting the fourth lens and the fifth lens to meet the above matching requirements, when light passes through the aperture and enters the fourth lens and the fifth lens, the light deflection is relatively gentle, which can effectively reduce the sensitivity of the system, play a role in improving the yield, and at the same time help make the production and assembly of this fixed-focus lens easier and more stable and reliable in use. In addition, the fourth lens and the fifth lens that meet the above matching requirements can initially correct the beam shape, smoothly guide off-axis light at large angles, and avoid off-axis light from generating severe and difficult-to-correct aberrations due to suddenly encountering a strong lens, achieving the purpose of initially balancing chromatic aberration.

[0048] In a specific embodiment, optionally, the sixth lens satisfies the following condition: 0.04 < Φ6 + Φ7 < 0.07; where Φ6 is the optical power of the sixth lens and Φ7 is the optical power of the seventh lens.

[0049] It can be understood that in this specific embodiment, by restricting the optical powers of the sixth lens and the seventh lens to meet the above matching requirements, the combination of these two lenses with positive and negative optical powers can make light maintain the necessary converging ability of the system while well correcting the influence of chromatic aberrations such as field curvature and distortion when passing through the sixth lens and the seventh lens.

[0050] In a specific embodiment, optionally, the eighth lens and the ninth lens satisfy the following condition: 0.07 < Φ8 + Φ9 < 0.35; where Φ8 is the optical power of the eighth lens and Φ9 is the optical power of the ninth lens.

[0051] It can be understood that in this specific embodiment, by restricting the combination of the optical powers of the eighth lens and the ninth lens to meet the above matching requirements, it can ensure that the chief ray enters the sensor at an angle as perpendicular as possible, achieve the purpose of optimizing the telecentricity, and at the same time make the final adjustment to the imaging quality.

[0052] In a specific embodiment, optionally, the fixed-focus lens satisfies the following condition: 2.04 < F / # < 2.156; where F represents the aperture number of the fixed-focus lens.

[0053] It can be understood that the smaller the F-number of the optical system, the stronger the light collection effect. Therefore, in this specific embodiment, by restricting the F-number of the fixed-focus lens to meet the above conditions, the lens can form a clear image in a darker environment and can be applied to special environments such as low-light monitoring.

[0054] In a specific embodiment, optionally, the fixed-focus lens satisfies the following conditions: 1.520 < H / f < 1.524; where f is the focal length of the fixed-focus lens; H is the vertical height of the intersection of the chief ray of the maximum field of view of the fixed-focus lens and the image plane.

[0055] It can be understood that in this specific embodiment, by restricting the focal length of the optical system and the vertical height of the intersection of the chief ray of the maximum field of view and the image plane, the field angle of the optical system can be controlled within a certain range to meet the usage requirements in the security monitoring scenario.

[0056] In a specific embodiment, optionally, the fixed-focus lens satisfies the following conditions: 0.08 < BFL / TTL < 0.10; where BFL is the distance from the image-side vertex of the ninth lens to the image plane, and TTL is the total optical length of the fixed-focus lens.

[0057] It can be understood that in this specific embodiment, by restricting BFL and TTL to meet the above requirements, it is beneficial to compress the total optical length of the entire fixed-focus lens, and at the same time, it can ensure that there is enough installation space for the imaging sensor and the filter.

[0058] Based on the same inventive concept as above, the present invention provides three different specific embodiments. The optical power relationship and the design ranges of relevant physical optical parameters are shown in Table 1:

[0059] Table 1 Design values of the optical power relationship and relevant physical optical parameters of each lens in three embodiments

[0060]

[0061] In Embodiment 1 of the present invention, referring to Figure 1 it can be known the structural composition of each element of the system, as well as the shape and position of each element, which is crucial for the system. It can be seen from the figure that the optical lens consists of 1 glass spherical lens and 8 plastic aspherical lenses. Among them, the aperture stop STO is located between the third lens and the fourth lens. A filter is also provided along the object plane to the image plane; the filter is located on the image-side surface of the ninth lens, and the filter can protect the photosensitive chip in the imaging sensor. The optical performance parameters of this fixed-focus lens are as follows: the focal length f is 2.210 mm, and the F / # is 2.092. As Figure 1 shown, the parameter design values of each lens in the fixed-focus lens of Embodiment 1 are shown in Table 2:

[0062] Table 2 A design value of each lens in the fixed-focus lens of Embodiment 1

[0063]

[0064] The surface numbers in Table 2 are assigned according to the surface sequence of each lens. "STO" 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 k value represents the magnitude of the conicity coefficient of the aspherical surface.

[0065] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations:

[0066] ;

[0067] 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, numerically the reciprocal of the radius of curvature; k is the fitted conic coefficient; AI are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th order terms of the aspherical polynomial. The even-order term coefficients of each aspherical surface in the above embodiment are shown in Table 3:

[0068] Table 3. Even-order term coefficients for each aspherical surface in Example 1

[0069]

[0070] Where 6.72863E-02 indicates that the coefficient A of surface number S3 is 6.72863 * 10. -2 And so on.

[0071] Figures 2A to 2F for Figure 1 The diagram shows the ray fan plots of a fixed-focus lens at different field-of-view positions. In each plot, 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, 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 not only reflects monochromatic aberrations at different wavelengths but also indicates the magnitude of transverse chromatic aberration. Figures 2A to 2F It can be seen that this optical system closely approximates the horizontal axis at all wavelengths under various fields of view, indicating that the transverse aberrations at each wavelength are well corrected. In addition, the curves of each color do not show obvious dispersion, indicating that this optical system also has good correction for chromatic aberration, ensuring the imaging requirement of clear images across the entire wavelength range.

[0072] Figure 3 for Figure 1 The diagram shows the axial chromatic aberration curve of a fixed-focus lens. In the diagram, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the vertical direction represents the maximum pupil radius. The dominant wavelength is 546.07 nm, and the horizontal direction represents the offset relative to the image plane, in millimeters (mm). Figure 3 It can be seen that the axial aberrations of different wavelengths with normalized apertures of 0.3 to 1 are all controlled within a reasonable range, indicating that the axial aberrations of this fixed-focus optical system are well controlled and meet the usage requirements.

[0073] Figure 4 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 546.07 nm, and the horizontal direction represents the offset relative to the image plane, in micrometers (µm). Figure 4 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 optical system is well controlled and can meet the application requirements under normal conditions.

[0074] 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, the structural composition, shape, and position of each component of the system are crucial to the system. As shown in the figure, the optical lens also consists of one glass spherical lens and eight plastic aspherical lenses, with the aperture stop STO located between the fourth and fifth lenses. A filter is also provided along the object plane to the image plane; the filter is located on the image-side surface of the seventh lens and protects the photosensitive chip in the imaging sensor. The optical performance parameters of this fixed-focus lens are as follows: focal length f = 2.200, f / # = 2.041. Figure 5 The parameter design values ​​of each lens in the fixed-focus lens of Embodiment 2 are shown in Table 4:

[0075] Table 4. Design values ​​for each lens in the fixed-focus lens in Example 2.

[0076]

[0077] The surface numbers in Table 4 are assigned according to the surface sequence of each lens. "STO" 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 k value represents the magnitude of the conicity coefficient of the aspherical surface.

[0078] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations:

[0079] ;

[0080] 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, numerically the reciprocal of the radius of curvature; k is the fitted conic coefficient; AI are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th order terms of the aspherical polynomial. The even-order term coefficients of each aspherical surface in the above Example 2 are shown in Table 5:

[0081] Table 5. Even-order coefficients of each aspherical surface in the fixed-focus lens in Example 2

[0082]

[0083] Where 6.70949E-02 indicates that the coefficient A of surface number S3 is 6.70949 * 10. -2 And so on.

[0084] Figures 6A to 6F for Figure 5 The diagram shows the ray fan plots of a fixed-focus lens at different field-of-view positions. In each plot, 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, 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 not only reflects monochromatic aberrations at different wavelengths but also indicates the magnitude of transverse chromatic aberration. Figures 6A to 6F It can be seen that this optical system closely approximates the horizontal axis at all wavelengths under various fields of view, indicating that the transverse aberrations at each wavelength are well corrected. In addition, the curves of each color do not show obvious dispersion, indicating that this optical system also has good correction for chromatic aberration, ensuring the imaging requirement of clear images across the entire wavelength range.

[0085] Figure 7 for Figure 5The diagram shows the axial chromatic aberration curve of a fixed-focus lens. In the diagram, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the vertical direction represents the maximum pupil radius. The dominant wavelength is 546.07 nm, and the horizontal direction represents the offset relative to the image plane, in millimeters (mm). Figure 7 It can be seen that the axial aberrations of different wavelengths with normalized apertures of 0.3 to 1 are all controlled within a reasonable range, indicating that the axial aberrations of this fixed-focus optical system are well controlled and meet the usage requirements.

[0086] Figure 8 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 546.07 nm, and the horizontal direction represents the offset relative to the image plane, in micrometers (µm). Figure 8 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 optical system is well controlled and can meet the application requirements under normal conditions.

[0087] 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, the structural composition, shape, and position of each component of the system are crucial to the system. As shown in the figure, the optical lens also consists of one glass spherical lens and eight plastic aspherical lenses, with the aperture stop STO located between the fourth and fifth lenses. A filter is also provided along the object plane to the image plane; the filter is located on the image-side surface of the seventh lens and protects the photosensitive chip in the imaging sensor. The optical performance parameters of this fixed-focus lens are as follows: focal length f = 2.200, f / # = 2.156. Figure 9 The parameter design values ​​of each lens in the fixed-focus lens of Embodiment 3 are shown in Table 6:

[0088] Table 6. Design values ​​for each lens in the fixed-focus lens in Example 3

[0089]

[0090] The surface numbers in Table 6 are assigned according to the surface sequence of each lens. "STO" 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 k value represents the magnitude of the conicity coefficient of the aspherical surface.

[0091] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations:

[0092] ;

[0093] 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, numerically the reciprocal of the radius of curvature; k is the fitted conic coefficient; AI are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th order terms of the aspherical polynomial. The even-order term coefficients of each aspherical surface in the above embodiment three are shown in Table 7:

[0094] Table 7. Even-order coefficients of each aspherical surface in the fixed-focus lens in Example 3

[0095]

[0096] Where 5.69123E-02 indicates that the coefficient A of surface number S3 is 5.69123 * 10. -2 And so on.

[0097] Figures 10A to 10F for Figure 9 The diagram shows the ray fan plots of a fixed-focus lens at different field-of-view positions. In each plot, 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, 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 not only reflects monochromatic aberrations at different wavelengths but also indicates the magnitude of transverse chromatic aberration. Figures 10A to 10F It can be seen that this optical system closely approximates the horizontal axis at all wavelengths under various fields of view, indicating that the transverse aberrations at each wavelength are well corrected. In addition, the curves of each color do not show obvious dispersion, indicating that this optical system also has good correction for chromatic aberration, ensuring the imaging requirement of clear images across the entire wavelength range.

[0098] Figure 11 for Figure 9 The diagram shows the axial chromatic aberration curve of a fixed-focus lens. In the diagram, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the vertical direction represents the maximum pupil radius. The dominant wavelength is 546.07 nm, and the horizontal direction represents the offset relative to the image plane, in millimeters (mm). Figure 11 It can be seen that the axial aberrations of different wavelengths with normalized apertures of 0.3 to 1 are all controlled within a reasonable range, indicating that the axial aberrations of this fixed-focus optical system are well controlled and meet the usage requirements.

[0099] Figure 12 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 546.07 nm, and the horizontal direction represents the offset relative to the image plane, in micrometers (µm). Figure 12 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 optical system is well controlled and can meet the application requirements under normal conditions.

[0100] 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 a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged in sequence from the object side to the image side along the optical axis; The first lens is a glass spherical lens with a negative focal power, the second lens is a plastic aspherical lens, the third lens is a plastic aspherical lens with a positive focal power, the fourth lens is a plastic aspherical lens with a positive focal power, the fifth lens is a plastic aspherical lens with a negative focal power, the sixth lens is a plastic aspherical lens with a positive focal power, the seventh lens is a plastic aspherical lens with a negative focal power, the eighth lens is a plastic aspherical lens with a positive focal power, and the ninth lens is a plastic aspherical lens.

2. The fixed-focus lens according to claim 1, characterized in that, The first lens satisfies the following conditions: 1.77 < Nd1 < 2.06, 26.9 < Vd1 < 49.7; where Nd1 is the refractive index of the first lens and Vd1 is the Abbe number of the first lens.

3. The fixed-focus lens according to claim 1, characterized in that, The first lens and the second lens satisfy the following conditions: -0.35 < Φ1 + Φ2 < -0.22; where Φ1 is the focal power of the first lens and Φ2 is the focal power of the second lens.

4. The fixed-focus lens according to claim 1, characterized in that, The third lens satisfies the following conditions: 0.11 < Φ3 < 0.13; where Φ3 is the focal power of the third lens.

5. The fixed-focus lens according to claim 1, characterized in that, The fourth lens and the fifth lens satisfy the following conditions: 0.13 < Φ4 + Φ5 < 0.17; where Φ4 is the focal power of the fourth lens and Φ5 is the focal power of the fifth lens.

6. The fixed-focus lens according to claim 1, characterized in that, The sixth lens satisfies the following conditions: 0.04 < Φ6 + Φ7 < 0.07; where Φ6 is the focal power of the sixth lens and Φ7 is the focal power of the seventh lens.

7. The fixed-focus lens according to claim 1, characterized in that, The eighth lens and the ninth lens satisfy the following conditions: 0.07 < Φ8 + Φ9 < 0.35; where Φ8 is the focal power of the eighth lens and Φ9 is the focal power of the ninth lens.

8. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens satisfies the following conditions: 2.04 < F / # < 2.156; where F represents the aperture number of the fixed-focus lens.

9. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens satisfies the following conditions: 1.520 < H / f < 1.524; where f is the focal length of the fixed-focus lens; H is the vertical height of the intersection of the chief ray of the maximum field of view of the fixed-focus lens and the image plane.

10. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens satisfies the following conditions: 0.08 < BFL / TTL <

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