A fixed-focus lens

Abstract

This invention discloses a fixed-focus lens, comprising a first lens with negative optical power, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, and a sixth lens with negative optical power, arranged sequentially along the optical axis from the object side to the image side; wherein the aperture stop of the fixed-focus lens is located between the second and third lenses. By employing the above technical solution, the optical power of each lens can be rationally allocated, making the propagation of light through the fixed-focus lens smoother and preventing excessive refraction of light on any single lens surface. This effectively corrects advanced aberrations, avoids introducing larger aberrations, and while ensuring a small aperture and low chromatic aberration, further corrects advanced aberrations, achieving higher image quality.

Description

Technical Field

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

[0002] With the development of the security monitoring field, the requirements for image quality, low-light performance, and reliability of security lenses are becoming increasingly stringent. However, existing security lenses cannot meet market demands. Therefore, how to further improve lens performance to meet market requirements has become an urgent technical problem to be solved. Summary of the Invention

[0003] This invention provides a fixed-focus lens to achieve a small aperture, small focal length, and high image quality.

[0004] According to one aspect of the present invention, a fixed-focus lens is provided, comprising: a first lens with negative optical power, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, and a sixth lens with negative optical power, arranged sequentially along the optical axis from the object side to the image side.

[0005] The aperture stop of the fixed-focus lens is located between the second lens and the third lens.

[0006] Optional,

[0007] The object-side surface of the first lens is convex, and the image-side surface of the first lens is concave.

[0008] The object-side surface of the second lens is convex, and the image-side surface of the second lens is concave.

[0009] The object-side surface of the third lens is convex, and the image-side surface of the third lens is convex.

[0010] The object-side surface of the fourth lens is concave, and the image-side surface of the fourth lens is also concave.

[0011] The object-side surface of the fifth lens is convex, and the image-side surface of the fifth lens is convex.

[0012] The object-side surface of the sixth lens is convex, and the image-side surface of the sixth lens is concave.

[0013] Optionally, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all plastic aspherical lenses.

[0014] Optional,

[0015] -1.696≤F1 / F≤-1.261;

[0016] 2.710≤F² / F≤3.019;

[0017] 2.555≤F3 / F≤3.028;

[0018] -3.016≤F4 / F≤-2.618;

[0019] 1.171≤F5 / F≤1.018;

[0020] -5.542≤F6 / F≤-4.460;

[0021] Wherein, F1 is the optical power of the first lens; F2 is the optical power of the second lens; F3 is the optical power of the third lens; F4 is the optical power of the fourth lens; F5 is the optical power of the fifth lens; F6 is the optical power of the sixth lens; and F is the total optical power of the fixed-focus lens.

[0022] Optionally, 1.51≤Nd1≤1.57; 30.00≤Vd1≤95.00;

[0023] Wherein, Nd1 is the refractive index of the first lens; Vd1 is the Abbe number of the first lens.

[0024] Optionally, 1.44≤Nd6≤1.95; 20.00≤Vd6≤95.00;

[0025] Wherein, Nd6 is the refractive index of the sixth lens; Vd6 is the Abbe number of the sixth lens.

[0026] Optionally, 3.744 ≤ TTL / F ≤ 5.028;

[0027] Wherein, TTL is the total optical length of the fixed-focus lens; F is the total optical power of the fixed-focus lens.

[0028] Optionally, 0.219 ≤ BFL / TTL ≤ 0.356;

[0029] Wherein, TTL is the total optical length of the fixed-focus lens; BFL is the optical back focal length of the fixed-focus lens.

[0030] Optionally, 0.000≤CT1 / (R11+R12)≤0.017; 0.002≤R12 / R11≤0.040;

[0031] Wherein, R11 is the radius of curvature of the first lens near the object side; R12 is the radius of curvature of the first lens near the image side; and CT1 is the center thickness of the first lens on the optical axis.

[0032] Optionally, 1.464 ≤ (CT1 + CT2) / CT2 ≤ 1.740;

[0033] Wherein, CT1 is the center thickness of the first lens on the optical axis; CT2 is the center thickness of the second lens on the optical axis.

[0034] The technical solution of this invention includes six lenses. The six lenses in the fixed-focus lens are arranged in a negative-positive-positive-negative-positive-negative configuration, which can reasonably allocate the optical power of each lens, making the propagation of light in the fixed-focus lens more stable and preventing excessive refraction of light on any lens surface. This effectively corrects advanced aberrations and avoids introducing larger aberrations. While ensuring a small aperture and low chromatic aberration, it further corrects advanced aberrations and achieves higher image quality.

[0035] 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

[0036] 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.

[0037] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in an embodiment of the present invention;

[0038] Figure 2 yes Figure 1 The field curvature distortion diagram of the fixed-focus lens is shown;

[0039] Figure 3 yes Figure 1 The image fan diagram of the fixed-focus lens is shown when the image plane is 0.0000mm;

[0040] Figure 4 yes Figure 1 The image fan diagram of the fixed-focus lens at an image plane of 0.5550mm is shown.

[0041] Figure 5 yes Figure 1 The image fan diagram of the fixed-focus lens is shown at an image plane of 0.9250mm;

[0042] Figure 6 yes Figure 1 The image fan diagram of the fixed-focus lens at an image plane of 1.2550mm is shown.

[0043] Figure 7 yes Figure 1 The image fan diagram of the fixed-focus lens at an image plane of 1.6650mm is shown.

[0044] Figure 8 yes Figure 1 The image fan diagram of the fixed-focus lens at an image plane of 1.8500mm is shown.

[0045] Figure 9 yes Figure 1 The diagram showing the chromatic aberration of a fixed-focus lens along its vertical axis;

[0046] Figure 10 yes Figure 1 The axial aberration diagram of the fixed-focus lens is shown.

[0047] Figure 11 This is a schematic diagram of another fixed-focus lens provided in an embodiment of the present invention;

[0048] Figure 12 yes Figure 11 The field curvature distortion diagram of the fixed-focus lens is shown;

[0049] Figure 13 yes Figure 11 The image fan diagram of the fixed-focus lens is shown when the image plane is 0.0000mm;

[0050] Figure 14 yes Figure 11 The image fan diagram of the fixed-focus lens at an image plane of 0.5550mm is shown.

[0051] Figure 15 yes Figure 11 The image fan diagram of the fixed-focus lens is shown at an image plane of 0.9250mm;

[0052] Figure 16 yes Figure 11 The image fan diagram of the fixed-focus lens at an image plane of 1.2550mm is shown.

[0053] Figure 17 yes Figure 11 The image fan diagram of the fixed-focus lens at an image plane of 1.6650mm is shown.

[0054] Figure 18 yes Figure 11 The image fan diagram of the fixed-focus lens at an image plane of 1.8500mm is shown.

[0055] Figure 19 yes Figure 11 The diagram showing the chromatic aberration of a fixed-focus lens along its vertical axis;

[0056] Figure 20 yes Figure 11The axial aberration diagram of the fixed-focus lens is shown.

[0057] Figure 21 This is a schematic diagram of the structure of another fixed-focus lens provided in an embodiment of the present invention;

[0058] Figure 22 yes Figure 21 The field curvature distortion diagram of the fixed-focus lens is shown;

[0059] Figure 23 yes Figure 21 The image fan diagram of the fixed-focus lens is shown when the image plane is 0.0000mm;

[0060] Figure 24 yes Figure 21 The image fan diagram of the fixed-focus lens at an image plane of 0.5550mm is shown.

[0061] Figure 25 yes Figure 21 The image fan diagram of the fixed-focus lens is shown at an image plane of 0.9250mm;

[0062] Figure 26 yes Figure 21 The image fan diagram of the fixed-focus lens at an image plane of 1.2550mm is shown.

[0063] Figure 27 yes Figure 21 The image fan diagram of the fixed-focus lens at an image plane of 1.6650mm is shown.

[0064] Figure 28 yes Figure 21 The image fan diagram of the fixed-focus lens at an image plane of 1.8500mm is shown.

[0065] Figure 29 yes Figure 21 The diagram showing the chromatic aberration of a fixed-focus lens along its vertical axis;

[0066] Figure 30 yes Figure 21 The diagram shows the axial aberration of a fixed-focus lens. Detailed Implementation

[0067] 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.

[0068] 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.

[0069] Figure 1 This is a schematic diagram of a fixed-focus lens provided in an embodiment of the present invention, for reference. Figure 1 The fixed-focus lens includes a first lens L1 with negative optical power, a second lens L2 with positive optical power, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a fifth lens L5 with positive optical power, and a sixth lens L6 with negative optical power, arranged sequentially from the object side to the image side along the optical axis; wherein, the aperture stop of the fixed-focus lens is located between the second lens L2 and the third lens L3.

[0070] Optical power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light. The larger the absolute value of the optical power, the stronger its ability to bend light; the smaller the absolute value, the weaker its ability to bend light. 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 of multiple lenses (i.e., a lens group).

[0071] For example, each of the lenses from the first lens L1 to the sixth lens L6 can be fixed in a lens barrel. Figure 1 (Not shown in the image) The fixed-focus lens also includes a filter L0, which is located on the side of the sixth lens L6 away from the fifth lens L5.

[0072] The fixed-focus lens provided in this embodiment of the invention includes six lenses. The six lenses in the fixed-focus lens are arranged in a negative-positive-positive-negative-positive-negative configuration, which can reasonably allocate the optical power of each lens, making the propagation of light in the fixed-focus lens more stable and preventing excessive refraction of light on any lens surface. This effectively corrects advanced aberrations and avoids introducing larger aberrations. While ensuring a small aperture and low chromatic aberration, it further corrects advanced aberrations and achieves higher image quality.

[0073] Optionally, the object-side surface of the first lens L1 is convex, and the image-side surface is concave; the object-side surface of the second lens L2 is convex, and the image-side surface is concave; the object-side surface of the third lens L3 is convex, and the image-side surface is convex; the object-side surface of the fourth lens L4 is concave, and the image-side surface is concave; the object-side surface of the fifth lens L5 is convex, and the image-side surface is convex; the object-side surface of the sixth lens L6 is convex, and the image-side surface is concave. By optimizing the optical power distribution, position, and shape of each lens element, both imaging requirements and structural compactness can be considered, achieving a fixed-focus lens with a small aperture, small size, and high image quality.

[0074] Optionally, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are all plastic aspherical lenses. By rationally setting the materials of each lens in a fixed-focus lens, production costs can be reduced. Placing all plastic aspherical lenses inside a fixed-focus lens can withstand long-term outdoor ultraviolet radiation, reducing yellowing and performance degradation.

[0075] Optionally, -1.696≤F1 / F≤-1.261; 2.710≤F2 / F≤3.019; 2.555≤F3 / F≤3.028; -3.016≤F4 / F≤-2.618; 1.171≤F5 / F≤1.018; -5.542≤F6 / F≤-4.460; where F1 is the optical power of the first lens L1; F2 is the optical power of the second lens L2; ​​F3 is the optical power of the third lens L3; F4 is the optical power of the fourth lens L4; F5 is the optical power of the fifth lens L5; F6 is the optical power of the sixth lens L6; and F is the total optical power of the fixed-focus lens. By rationally allocating the optical power, the structure is compact, and chromatic aberration and spherical aberration can be corrected, which is beneficial to improving image quality, meeting the requirements of high-definition and nighttime monitoring.

[0076] Optionally, 1.51≤Nd1≤1.57; 30.00≤Vd1≤95.00; where Nd1 is the refractive index of the first lens L1; and Vd1 is the Abbe number of the first lens L1. The first lens L1 is located at the foremost position of the fixed-focus lens. By reasonably setting the refractive index and Abbe number, it is beneficial to ensure that the light has a larger aperture before the aperture stop, thus narrowing the lens aperture.

[0077] Optionally, 1.44≤Nd6≤1.95; 20.00≤Vd6≤95.00; where Nd6 is the refractive index of the sixth lens; and Vd6 is the Abbe number of the sixth lens. The sixth lens L6 is located at the very end of the fixed-focus lens. The sixth lens L6 is made of a high Abbe number material, which can more effectively bend light, thereby effectively controlling the angle of incidence of light entering the imaging chip. This avoids excessive divergence of incident light after passing through the sixth lens L6, which would otherwise result in an excessively large angle of incidence, and is beneficial for adapting to a wider range of chips.

[0078] Optionally, 3.744 ≤ TTL / F ≤ 5.028; where TTL is the total optical length of the fixed-focus lens; and F is the total optical power of the fixed-focus lens. This allows for the miniaturization of fixed-focus lenses and reduces production costs.

[0079] Optionally, 0.219 ≤ BFL / TTL ≤ 0.356; where TTL is the total optical length of the prime lens; and BFL is the optical back focal length of the prime lens. This allows for a compact lens structure while maintaining the miniaturization of the prime lens, reducing the lens's sensitivity to MTF, and improving production yield.

[0080] Optionally, 0.000≤CT1 / (R11+R12)≤0.017; 0.002≤R12 / R11≤0.040; where R11 is the radius of curvature of the object-side side of the first lens; R12 is the radius of curvature of the image-side side of the first lens L1; and CT1 is the center thickness of the first lens L1 on the optical axis. By controlling the ratio of the sum of the radius of curvature of the object-side side and the radius of curvature of the image-side side of the first lens L1 to the center thickness of the first lens L1 on the optical axis within this range, it is beneficial to constrain the lens shape of the first lens L1, avoid the lens shape of the first lens L1 being too curved, and facilitate the processing and shaping of the first lens L1.

[0081] Optionally, 1.464 ≤ (CT1 + CT2) / CT2 ≤ 1.740; where CT1 is the center thickness of the first lens on the optical axis; and CT2 is the center thickness of the second lens on the optical axis. By controlling the center thicknesses of the first lens L1 and the second lens L2 within a certain range, it is beneficial to the processing and shaping of the lenses, thereby reducing the difficulty of processing and manufacturing; at the same time, it is also beneficial to control the direction of light, making the light travel more smoothly, reducing the sensitivity of the system, and improving the imaging quality of the system.

[0082] This invention, through the allocation of parameters such as lens surface type, radius of curvature, thickness, and material of each lens in a fixed-focus lens, can ultimately achieve a fixed-focus lens that is suitable for both day and night use, with an imaging range between 100° and 140°, a small aperture, small size, low cost, and clear imaging under a 1 / 5″ target surface.

[0083] In one exemplary embodiment, Table 1 details a feasible implementation. Figure 1 The specific parameters of the fixed-focus lens are shown.

[0084] Table 1. Parameter Design of a Fixed-Focus Lens

[0085]

[0086] Table 2 shows the design parameters of a fixed-focus lens, including lens surface type, radius of curvature, thickness, and materials, which correspond to those in Table 1.

[0087] Table 2. Design of optical physical parameters for a fixed-focus lens.

[0088]

[0089] like Figure 1 As shown, the fixed-focus lens provided in this embodiment consists of six lenses, namely, the fixed-focus lens includes a first lens L1 with negative optical power, a second lens L2 with positive optical power, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a fifth lens L5 with positive optical power, and a sixth lens L6 with negative optical power, arranged sequentially along the optical axis from the object side to the image side; wherein, the aperture stop STO of the fixed-focus lens is located between the second lens L2 and the third lens L3.

[0090] In Table 2, the surface numbers are assigned according to the surface sequence of each lens. For example, surface number 1 represents the object side of the first lens L1, surface number 2 represents the image side of the first lens L1, and so on. "STO" represents the aperture of a fixed-focus lens. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates 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, in mm. 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 ability of the material between the current surface and the next surface to disperse light.

[0091] Table 3 shows the aspheric coefficient values ​​used in the current embodiment.

[0092] Table 3 Aspherical coefficients of a fixed-focus lens

[0093]

[0094] Where 1.059514E-01 indicates that the coefficient A of face number 1 is 1.059514 × 10 -1 And so on.

[0095] The K values ​​in Table 3 represent the numerical values ​​of the best-fit conic coefficients for the aspheric surface. The conic coefficients of the aspheric surface can be defined using the following aspheric formula, but are not limited to the following representations:

[0096]

[0097] 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; A, B, C, D, E, F, G, H, and I are the 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th order coefficients of the aspherical polynomial, respectively.

[0098] Based on the above parameter design, Table 4 shows the lens parameters of the fixed-focus lens implemented in this embodiment.

[0099] Table 4 Lens parameters of a fixed-focus lens

[0100]

[0101] Figure 2 yes Figure 1 The field curvature distortion diagram of the fixed-focus lens shown is as follows: Figure 2 As shown, in the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; from Figure 2 As can be seen, the fixed-focus lens provided in this embodiment effectively controls field curvature, meaning that during imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit; from Figure 2 As can be seen, the distortion of the fixed-focus lens provided in this embodiment is well corrected, and the imaging distortion is small. Among other things, Figure 2 The field curvature distortion diagram is for light with a wavelength of 546nm, with a maximum field of view of 55.285 degrees, a sagittal field curvature of 0.0184mm, and a meridional field curvature of 0.1016mm.

[0102] Figures 3 to 8 yes Figure 1 The aperture fan diagram of the fixed-focus lens shown is as follows: Figures 3 to 8 As shown, the horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The fan diagram is one of the most commonly used evaluation methods in modern optical design. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all rays converge at the same point on the image plane. The interval on the vertical axis of the curve represents the maximum dispersion range of the beam on the ideal image plane. The fan diagram can reflect not only monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figures 3 to 8It can be seen that the system closely approximates the horizontal axis at all wavelengths under various fields of view, indicating that the transverse aberrations of each wavelength are well corrected. Simultaneously, there is no significant dispersion among the wavelengths, indicating that chromatic aberration is also well corrected, thus ensuring that the optical system can achieve high-resolution imaging requirements. Among these, Figure 3 yes Figure 1 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 0.0000mm. Figure 4 yes Figure 1 The image shows the aperture fan pattern of a fixed-focus lens at an image plane of 0.5550mm. Figure 5 yes Figure 1 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 0.9250mm. Figure 6 yes Figure 1 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 1.2550mm. Figure 7 yes Figure 1 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 1.6650mm. Figure 8 yes Figure 1 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 1.8500mm. Figures 3 to 8 Curves for light with wavelengths of 436 nm, 487 nm, 546 nm, 587 nm, and 656 nm are shown, with a maximum scaling of ±80.000 μm.

[0103] Figure 9 yes Figure 1 The diagram showing the chromatic aberration of a fixed-focus lens along its vertical axis is shown. Figure 9 The transverse chromatic aberration curves for wavelengths of 436, 487, 546, 587, and 656 are shown. The vertical direction represents the normalized field of view (maximum field of view is 1.8500 mm), with 0 indicating on the optical axis. The dominant wavelength is 546 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (μm). Figure 9 It can be seen that the chromatic aberration along the vertical axis is well controlled at different wavelengths, indicating that the chromatic aberration along the vertical axis of this fixed-focus lens is well controlled and can meet the requirements of wide-spectrum applications.

[0104] Figure 10 yes Figure 1 The axial aberration diagram of the fixed-focus lens is shown. Figure 10 Axial aberration curves for wavelengths of 436, 487, 546, 587, and 656 nm are shown. The vertical direction represents the normalized aperture, with 0 indicating the optical axis. The vertex in the perpendicular direction represents the maximum pupil radius, which is 0.3030 mm. The dominant wavelength is 546 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in millimeters (mm). Figure 10It can be seen that the axial aberrations of the normalized apertures of different wavelengths (0-1.0) are all controlled within a reasonable range, indicating that the transverse chromatic aberration of this fixed-focus lens is well controlled.

[0105] In another exemplary embodiment, Figure 11 This is a schematic diagram of another fixed-focus lens provided in an embodiment of the present invention. Table 5 describes in detail another feasible implementation. Figure 11 The specific parameters of the fixed-focus lens are shown.

[0106] Table 5. Another parameter design for fixed-focus lenses.

[0107]

[0108] Table 6 shows the design parameters of a fixed-focus lens, including lens surface type, radius of curvature, thickness, and materials, corresponding to Table 5.

[0109] Table 6. Another optical physical parameter design for fixed-focus lenses

[0110]

[0111] like Figure 11 As shown, the fixed-focus lens provided in this embodiment consists of six lenses, namely, the fixed-focus lens includes a first lens L1 with negative optical power, a second lens L2 with positive optical power, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a fifth lens L5 with positive optical power, and a sixth lens L6 with negative optical power, arranged sequentially along the optical axis from the object side to the image side; wherein, the aperture stop STO of the fixed-focus lens is located between the second lens and the third lens.

[0112] In Table 6, the surface numbers are assigned according to the surface sequence of each lens. For example, surface number 1 represents the object side of the first lens L1, surface number 2 represents the image side of the first lens L1, and so on. "STO" represents the aperture of a fixed-focus lens. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates 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 Abbe number represents the ability of the material between the current surface and the next surface to disperse light.

[0113] Table 7 shows the aspheric coefficient values ​​used in the current embodiment.

[0114] Table 7 Aspherical coefficients of another type of fixed-focus lens

[0115]

[0116] Where 1.066066E-01 indicates that the coefficient A of surface number 1 is 1.066066 × 10 -1 And so on.

[0117] The K values ​​in Table 7 represent the numerical values ​​of the best-fit conic coefficients for the aspheric surface. The conic coefficients of the aspheric surface can be defined using the following aspheric formula, but are not limited to the following representations:

[0118]

[0119] 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; A, B, C, D, E, F, G, H, and I are the 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th order coefficients of the aspherical polynomial, respectively.

[0120] Based on the above parameter design, Table 8 shows the lens parameters of the fixed-focus lens implemented in this embodiment.

[0121] Table 8 Lens parameters for another type of fixed-focus lens

[0122]

[0123] Figure 12 yes Figure 11 The diagram shows the field curvature distortion of a fixed-focus lens. Figure 12 In the left-hand coordinate system, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 12 As can be seen, the fixed-focus lens provided in this embodiment effectively controls field curvature, meaning that during imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit; from Figure 12 As can be seen, the distortion of the fixed-focus lens provided in this embodiment is well corrected, and the imaging distortion is small. Among other things, Figure 12 The field curvature distortion diagram is for light with a wavelength of 546nm, with a maximum field of view of 61.900 degrees, a sagittal field curvature of 0.0167mm, and a meridional field curvature of 0.1126mm.

[0124] Figures 13 to 18 yes Figure 11 The aperture fan diagram of the fixed-focus lens shown is as follows: Figures 13 to 18As shown, the horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The fan diagram is one of the most commonly used evaluation methods in modern optical design. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all rays converge at the same point on the image plane. The interval on the vertical axis of the curve represents the maximum dispersion range of the beam on the ideal image plane. The fan diagram can reflect not only monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figures 13 to 18 It can be seen that the system closely approximates the horizontal axis at all wavelengths under various fields of view, indicating that the transverse aberrations of each wavelength are well corrected. Simultaneously, there is no significant dispersion among the wavelengths, indicating that chromatic aberration is also well corrected, thus ensuring that the optical system can achieve high-resolution imaging requirements. Among these, Figure 13 yes Figure 11 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 0.0000mm. Figure 14 yes Figure 11 The image shows the aperture fan pattern of a fixed-focus lens at an image plane of 0.5550mm. Figure 15 yes Figure 11 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 0.9250mm. Figure 16 yes Figure 11 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 1.2550mm. Figure 17 yes Figure 11 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 1.6650mm. Figure 18 yes Figure 11 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 1.8500mm. Figures 13 to 18 Curves for light with wavelengths of 436 nm, 487 nm, 546 nm, 587 nm, and 656 nm are shown, with a maximum scaling of ±80.000 μm.

[0125] Figure 19 yes Figure 11 The diagram showing the chromatic aberration of a fixed-focus lens along its vertical axis is shown. Figure 19 The transverse chromatic aberration curves for wavelengths of 436, 487, 546, 587, and 656 are shown. The vertical direction represents the normalized field of view (maximum field of view is 1.8500 mm), with 0 indicating on the optical axis. The dominant wavelength is 546 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (μm). Figure 19 It can be seen that the chromatic aberration along the vertical axis is well controlled at different wavelengths, indicating that the chromatic aberration along the vertical axis of this fixed-focus lens is well controlled and can meet the requirements of wide-spectrum applications.

[0126] Figure 20 yes Figure 11 The axial aberration diagram of the fixed-focus lens is shown. Figure 20 Axial aberration curves for wavelengths of 436, 487, 546, 587, and 656 nm are shown. The vertical direction represents the normalized aperture, with 0 indicating the optical axis. The vertex in the vertical direction represents the maximum pupil radius, which is 0.2765 mm. The dominant wavelength is 546 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in millimeters (mm). Figure 20 It can be seen that the axial aberrations of the normalized apertures of different wavelengths (0-1.0) are all controlled within a reasonable range, indicating that the transverse chromatic aberration of this fixed-focus lens is well controlled.

[0127] In yet another exemplary embodiment, Figure 21 This is a schematic diagram of another fixed-focus lens provided in the embodiments of the present invention. Table 9 describes in detail another feasible implementation method. Figure 21 The specific parameters of the fixed-focus lens are shown.

[0128] Table 9. Another parameter design for fixed-focus lenses.

[0129]

[0130] Table 10 shows the design parameters of a fixed-focus lens, including lens surface type, radius of curvature, thickness, and material, which correspond to those in Table 9.

[0131] Table 10: Another optical physical parameter design for fixed-focus lenses

[0132]

[0133] like Figure 21 As shown, the fixed-focus lens provided in this embodiment consists of six lenses, namely, the fixed-focus lens includes a first lens L1 with negative optical power, a second lens L2 with positive optical power, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a fifth lens L5 with positive optical power, and a sixth lens L6 with negative optical power, arranged sequentially along the optical axis from the object side to the image side; wherein, the aperture stop STO of the fixed-focus lens is located between the second lens and the third lens.

[0134] In Table 10, the surface numbers are assigned according to the surface sequence of each lens. For example, surface number 1 represents the object side of the first lens L1, surface number 2 represents the image side of the first lens L1, and so on. "STO" represents the aperture of a fixed-focus lens. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates 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 Abbe number represents the ability of the material between the current surface and the next surface to disperse light.

[0135] Table 11 shows the aspheric coefficient values ​​used in the current embodiment.

[0136] Table 11 Aspherical coefficients of another type of fixed-focus lens

[0137]

[0138] Where 1.068248E-01 indicates that the coefficient A of surface number 1 is 1.068248 × 10 -1 .

[0139] The K values ​​in Table 11 represent the numerical values ​​of the best-fit conic coefficients for the aspheric surface. The conic coefficients of the aspheric surface can be defined using the following aspheric formula, but are not limited to the following representations:

[0140]

[0141] 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; A, B, C, D, E, F, G, H, and I are the 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th order coefficients of the aspherical polynomial, respectively.

[0142] Based on the above parameter design, Table 12 shows the lens parameters of the fixed-focus lens implemented in this embodiment.

[0143] Table 12 Lens parameters for another type of fixed-focus lens

[0144]

[0145] Figure 22 yes Figure 21 The diagram shows the field curvature distortion of a fixed-focus lens. Figure 22 In the left-hand coordinate system, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 22 As can be seen, the fixed-focus lens provided in this embodiment effectively controls field curvature, meaning that during imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit; from Figure 22 As can be seen, the distortion of the fixed-focus lens provided in this embodiment is well corrected, and the imaging distortion is small. Among other things, Figure 22 The field curvature distortion diagram is for light with a wavelength of 546nm, with a maximum field of view of 59.700 degrees, a sagittal field curvature of 0.0199mm, and a meridional field curvature of 0.0865mm.

[0146] Figures 23 to 28 yes Figure 21 The aperture fan diagram of the fixed-focus lens shown is as follows: Figures 23 to 28 As shown, the horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The fan diagram is one of the most commonly used evaluation methods in modern optical design. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all rays converge at the same point on the image plane. The interval on the vertical axis of the curve represents the maximum dispersion range of the beam on the ideal image plane. The fan diagram can reflect not only monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figures 23 to 28 It can be seen that the system closely approximates the horizontal axis at all wavelengths under various fields of view, indicating that the transverse aberrations of each wavelength are well corrected. Simultaneously, there is no significant dispersion among the wavelengths, indicating that chromatic aberration is also well corrected, thus ensuring that the optical system can achieve high-resolution imaging requirements. Among these, Figure 23 yes Figure 21 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 0.0000mm. Figure 24 yes Figure 21 The image shows the aperture fan pattern of a fixed-focus lens at an image plane of 0.5550mm. Figure 25 yes Figure 21 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 0.9250mm. Figure 26 yes Figure 21 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 1.2550mm. Figure 27 yes Figure 21 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 1.6650mm. Figure 28 yes Figure 21 The image shows the aperture fan diagram of a fixed-focus lens at an image plane of 1.8500mm. Figures 23 to 28 Curves for light with wavelengths of 436 nm, 487 nm, 546 nm, 587 nm, and 656 nm are shown, with a maximum scaling of ±80.000 μm.

[0147] Figure 29 yes Figure 21 The diagram showing the chromatic aberration of a fixed-focus lens along its vertical axis is shown. Figure 29 The transverse chromatic aberration curves for wavelengths of 436, 487, 546, 587, and 656 are shown. The vertical direction represents the normalized field of view (maximum field of view is 1.8500 mm), with 0 indicating on the optical axis. The dominant wavelength is 546 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (μm). Figure 29 It can be seen that the chromatic aberration along the vertical axis is well controlled at different wavelengths, indicating that the chromatic aberration along the vertical axis of this fixed-focus lens is well controlled and can meet the requirements of wide-spectrum applications.

[0148] Figure 30 yes Figure 21 The axial aberration diagram of the fixed-focus lens is shown. Figure 20 Axial aberration curves for wavelengths of 436, 487, 546, 587, and 656 nm are shown. The vertical direction represents the normalized aperture, with 0 indicating the optical axis. The vertex in the perpendicular direction represents the maximum pupil radius, which is 0.3001 mm. The dominant wavelength is 546 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in millimeters (mm). Figure 30 It can be seen that the axial aberrations of the normalized apertures of different wavelengths (0-1.0) are all controlled within a reasonable range, indicating that the transverse chromatic aberration of this fixed-focus lens is well controlled.

[0149] 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, 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, include: Along the optical axis from the object side to the image side, the following lenses are arranged in sequence: a first lens with negative optical power, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, and a sixth lens with negative optical power. The aperture stop of the fixed-focus lens is located between the second lens and the third lens; the fixed-focus lens has six lens elements with optical power. -1.696≤F1 / F≤-1.261; 2.710≤F² / F≤3.019; 2.555≤F3 / F≤3.028; -3.016≤F4 / F≤-2.618; 1.171≤F5 / F≤1.018; -5.542≤F6 / F≤-4.460; Wherein, F1 is the optical power of the first lens; F2 is the optical power of the second lens; F3 is the optical power of the third lens; F4 is the optical power of the fourth lens; F5 is the optical power of the fifth lens; F6 is the optical power of the sixth lens; and F is the total optical power of the fixed-focus lens.

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 of the first lens is concave. The object-side surface of the second lens is convex, and the image-side surface of the second lens is concave. The object-side surface of the third lens is convex, and the image-side surface of the third lens is convex. The object-side surface of the fourth lens is concave, and the image-side surface of the fourth lens is also concave. The object-side surface of the fifth lens is convex, and the image-side surface of the fifth lens is convex. The object-side surface of the sixth lens is convex, and the image-side surface of the sixth lens is concave.

3. The fixed-focus lens according to claim 1, characterized in that, The first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all plastic aspherical lenses.

4. The fixed-focus lens according to claim 1, characterized in that, 1.51≤Nd1≤1.57; 30.00≤Vd1≤95.00; Wherein, Nd1 is the refractive index of the first lens; Vd1 is the Abbe number of the first lens.

5. The fixed-focus lens according to claim 1, characterized in that, 1.44≤Nd6≤1.95; 20.00≤Vd6≤95.00; Wherein, Nd6 is the refractive index of the sixth lens; Vd6 is the Abbe number of the sixth lens.

6. The fixed-focus lens according to claim 1, characterized in that, 3.744≤TTL / F≤5.028; Wherein, TTL is the total optical length of the fixed-focus lens; F is the total optical power of the fixed-focus lens.

7. The fixed-focus lens according to claim 1, characterized in that, 0.219≤BFL / TTL≤0.356; Wherein, TTL is the total optical length of the fixed-focus lens; BFL is the optical back focal length of the fixed-focus lens.

8. The fixed-focus lens according to claim 1, characterized in that, 0.000≤CT1 / (R11+R12)≤0.017; 0.002≤R12 / R11≤0.040; Wherein, R11 is the radius of curvature of the first lens near the object side; R12 is the radius of curvature of the first lens near the image side; and CT1 is the center thickness of the first lens on the optical axis.

9. The fixed-focus lens according to claim 1, characterized in that, 1.464≤(CT1+CT2) / CT2≤1.740; Wherein, CT1 is the center thickness of the first lens on the optical axis; CT2 is the center thickness of the second lens on the optical axis.

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