prime lens

Abstract

This invention relates to a fixed-focus lens, which, along the optical axis from the object side to the image side, sequentially includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens, wherein the optical power of the first lens and the fifth lens is negative, and the optical power of the second lens and the fourth lens is positive.

Description

Technical Field

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

[0002] With the continuous upgrading and development of Internet technology, prime lenses are widely used in video conferencing, online teaching, and online video shooting, and have received increasing attention from the public. As a result, the requirements for their image quality are also getting higher and higher.

[0003] However, current prime lenses still have the following shortcomings: 1. Existing lens configurations make it difficult to effectively correct system aberrations, resulting in poor image quality; 2. Existing lenses suffer from excessive overall length and large size, leading to high overall cost and weight; 3. Existing lenses have relatively small apertures, resulting in poor light transmission and low relative illumination at the edges; 4. Existing lenses often suffer from poor distortion control when achieving a large field of view, causing significant distortion in the captured image and affecting post-processing.

[0004] For example, Chinese patent 202210262099.7 discloses a lens that can be used for video conferencing, with a TTL ≤ 24mm, an aperture FNO ≥ 2.6, and optical distortion ≤ |-5%|. However, it cannot simultaneously achieve low distortion, large aperture, small size, and high resolution.

[0005] Therefore, there is an urgent need for a fixed-focus lens with low distortion, large aperture, miniaturization, low cost, and high resolution. Summary of the Invention

[0006] In view of this, the present invention aims to propose a fixed-focus lens to solve the problem that current fixed-focus lenses cannot simultaneously achieve low distortion, large aperture, miniaturization, low cost and high resolution.

[0007] This invention provides a fixed-focus lens, which, along the optical axis from the object side to the image side, sequentially includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens. The first lens and the fifth lens have negative optical power, while the second lens and the fourth lens have positive optical power.

[0008] In a preferred embodiment of the present invention, the first lens and the eighth lens are convex-concave lenses, the image-side surfaces of the second lens and the fourth lens are convex, the object-side surfaces of the third lens and the sixth lens are convex, and the seventh lens is a concave-convex lens.

[0009] In a preferred embodiment of the present invention, the fifth lens is a convex-concave lens or a concave-convex lens.

[0010] In a preferred embodiment of the present invention, the effective focal length F1 of the first lens and the total effective focal length F of the fixed-focus lens satisfy:

[0011] -2.60≤F1 / F≤-1.30.

[0012] In a preferred embodiment of the present invention, the object-side radius of curvature R11 of the first lens and the image-side radius of curvature R12 of the first lens satisfy the following:

[0013] 1.42≤(R11+R12) / (R11-R12)≤3.00.

[0014] In a preferred embodiment of the present invention, the object-side radius of curvature R11 of the first lens, the image-side radius of curvature R12 of the first lens, and the effective focal length F1 of the first lens satisfy the following:

[0015] 0.55≤|(R11+R12) / F1|≤5.89

[0016] In a preferred embodiment of the present invention, the combined effective focal length F345 of the third lens to the fifth lens and the total effective focal length F of the fixed-focus lens satisfy the following:

[0017] 0.87≤F345 / F≤3.50.

[0018] In a preferred embodiment of the present invention, the effective focal length F4 of the fourth lens and the total effective focal length F of the fixed-focus lens satisfy the following:

[0019] 0.30≤F4 / F≤4.45.

[0020] In a preferred embodiment of the present invention, the effective focal length F4 of the fourth lens and the effective focal length F5 of the fifth lens satisfy the following:

[0021] -3.68≤F4 / F5≤-0.15.

[0022] In a preferred embodiment of the present invention, the effective focal length F5 of the fifth lens and the total effective focal length F of the fixed-focus lens satisfy the following:

[0023] -1.28≤F5 / F≤-1.10.

[0024] In a preferred embodiment of the present invention, the effective focal length F6 of the sixth lens and the total effective focal length F of the fixed-focus lens satisfy the following:

[0025] |F6 / F|≤15.57.

[0026] In a preferred embodiment of the present invention, the combined effective focal length F78 of the seventh lens to the eighth lens and the total effective focal length F of the fixed-focus lens satisfy the following:

[0027] -14.50≤F78 / F≤4.00.

[0028] In a preferred embodiment of the present invention, the object-side radius of curvature R61 of the sixth lens and the image-side radius of curvature R62 of the sixth lens satisfy:

[0029] 0.55≤|R61 / R62|≤6.30.

[0030] In a preferred embodiment of the present invention, the object-side radius of curvature R61 of the sixth lens, the image-side radius of curvature R62 of the sixth lens, and the total effective focal length F of the fixed-focus lens satisfy the following:

[0031] -0.65≤(R61+R62) / F≤5.96.

[0032] In a preferred embodiment of the present invention, the thickness d3 of the third lens on the optical axis, the thickness d4 of the fourth lens on the optical axis, the thickness d5 of the fifth lens on the optical axis, and the total optical length TTL of the fixed-focus lens satisfy the following:

[0033] 0.25≤(d3+d4+d5) / TTL≤0.34.

[0034] In a preferred embodiment of the present invention, the total optical length TTL of the fixed-focus lens and the half-image height H of the fixed-focus lens satisfy:

[0035] 3.85≤TTL / H≤4.75.

[0036] In a preferred embodiment of the present invention, along the optical axis from the object side to the image side, the fixed-focus lens further includes an image plane located behind the eighth lens, wherein the distance BFL from the center of the image side surface of the eighth lens to the center of the image plane and the total optical length TTL of the fixed-focus lens satisfy the following:

[0037] 0.15≤BFL / TTL≤0.18.

[0038] In a preferred embodiment of the present invention, the effective focal length F of the fixed-focus lens and the entrance pupil diameter EPD of the fixed-focus lens satisfy the following:

[0039] F / EPD≤1.80.

[0040] The fixed-focus lens of this invention employs eight lenses. By matching the positive and negative optical powers and shapes of each lens, and by setting appropriate parameters such as dispersion coefficient and thickness, the optical lens simultaneously achieves the beneficial effects of low distortion, large aperture, small size, and high resolution. The fixed-focus lens of this invention can achieve a large aperture FNO ≤ 1.80, full-field optical distortion ≤ |-3.1%|, and a total lens length TTL ≤ 15mm. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the 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.

[0042] Figure 1 This is a schematic diagram of the fixed-focus lens according to the first embodiment of the present invention;

[0043] Figure 2 This is a schematic diagram of the F-Theta distortion of a fixed-focus lens according to the first embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of the fixed-focus lens according to the second embodiment of the present invention;

[0045] Figure 4 This is a schematic diagram of the F-Theta distortion of a fixed-focus lens according to the second embodiment of the present invention;

[0046] Figure 5 This is a schematic diagram of the fixed-focus lens according to the third embodiment of the present invention;

[0047] Figure 6 This is a schematic diagram of the F-Theta distortion of a fixed-focus lens according to the third embodiment of the present invention;

[0048] Figure 7 This is a schematic diagram of the fixed-focus lens according to the fourth embodiment of the present invention;

[0049] Figure 8 This is a schematic diagram of F-Theta distortion of a fixed-focus lens according to the fourth embodiment of the present invention. Detailed Implementation

[0050] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0051] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the subject is called the object-side surface of the lens, and the surface of each lens closest to the imaging side is called the image-side surface of the lens.

[0052] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0053] like Figure 1 , Figure 3 , Figure 5 and Figure 7 As shown, the fixed-focus lens of this embodiment of the invention, along the optical axis from the object side to the image side, sequentially includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, a flat plate CG, and an image plane IMA.

[0054] The first lens L1 is a convex-concave lens with negative optical power, which can converge incident light rays with a large field of view into the optical system as much as possible, effectively expanding the field of view.

[0055] The second lens L2 is a lens with positive optical power and a convex image side, which can effectively control the trajectory of incident light in the optical system, reduce system aberrations, and improve image quality.

[0056] The third lens L3 is a lens with a convex object side, which can effectively control the light to enter the rear of the optical system smoothly, thus improving the image quality.

[0057] The fourth lens, L4, is a lens with positive optical power and a convex image side. This helps to control the direction of light rays, make the light path smooth, reduce tolerance sensitivity, and improve image quality.

[0058] The fifth lens L5 is a lens with negative optical power. Preferably, the fifth lens L5 is a concave-convex lens or a convex-concave lens. However, the fifth lens L5 is not limited to concave-convex or convex-concave lenses; it can also be other shapes. This helps to balance various aberrations, improve image quality, and simultaneously elevate the light path, meeting image size requirements while increasing illumination.

[0059] The sixth lens L6 is a convex lens, the seventh lens L7 is a concave-convex lens, and the eighth lens L8 is a convex-concave lens. This can effectively control the direction of light, elevate the light, balance astigmatism, meet the requirements for image size while improving the optical imaging quality, and effectively correct distortion, so that the absolute value of optical distortion is less than or equal to 3.1%.

[0060] In different embodiments of the present invention, the aperture stop STO may be located between the second lens L2 and the third lens L3, or between the third lens L3 and the fourth lens L4. Positioning the aperture stop STO in either of these locations effectively concentrates the light entering the optical system, shortens the overall length of the optical system, and effectively reduces the maximum aperture of the optical system.

[0061] In a preferred embodiment of the present invention, the first lens L1 is a glass spherical lens, the second lens L2, the sixth lens L6, the seventh lens L7, and the eighth lens L8 are all plastic aspherical lenses, and the third lens L3, the fourth lens L4, and the fifth lens L5 can be either glass spherical lenses or plastic aspherical lenses. Using a glass-plastic hybrid design helps reduce the cost of the optical system and also helps balance the high and low temperature performance of the optical lens, achieving high imaging quality within the range of -20℃ to 60℃. Using aspherical lenses helps correct distortion, ensuring that the absolute value of optical distortion is less than or equal to 3.1%.

[0062] In a preferred embodiment of the present invention, the third lens L3 and the fourth lens L4 can be cemented doublet lenses, or the fourth lens L4 and the fifth lens L5 can be cemented doublet lenses. This can effectively reduce the tolerance sensitivity of the lens unit during assembly, improve the assembly yield, and also help to reduce the air gap between the lenses, thereby achieving lens miniaturization.

[0063] In a preferred embodiment of the present invention, the object-side radius of curvature R11, the image-side radius of curvature R12, and the effective focal length F1 of the first lens L1 satisfy: 0.55 ≤ |(R11+R12) / F1| ≤ 5.89. This effectively corrects various aberrations formed by incident light rays and improves image quality.

[0064] In a preferred embodiment of the present invention, the effective focal length F1 of the first lens L1 and the total effective focal length F of the fixed-focus lens satisfy: -2.60 ≤ F1 / F ≤ -1.30. This facilitates the convergence of large-angle light rays into the optical system, effectively expanding the field of view of the optical system.

[0065] In a preferred embodiment of the present invention, the radius of curvature R11 of the object side of the first lens L1 and the radius of curvature R12 of the image side of the first lens L1 are: 1.42≤(R11+R12) / (R11-R12)≤3.00. This helps to converge light from different fields of view and improve image brightness.

[0066] In a preferred embodiment of the present invention, the combined effective focal length F345 of the third lens L3 to the fifth lens L5 and the total effective focal length F of the fixed-focus lens satisfy: 0.87≤F345 / F≤3.50. This facilitates the smooth entry of more light into the optical system, controls the light path of the optical system, improves illumination, and also helps to balance spherical aberration and astigmatism, thereby improving the resolving power of the lens.

[0067] In a preferred embodiment of the present invention, the effective focal length F4 of the fourth lens L4 and the total effective focal length F of the fixed-focus lens satisfy: 0.30 ≤ F4 / F ≤ 4.45. More preferably, it satisfies: 0.3 ≤ F4 / F ≤ 1.55. This facilitates control of light trajectory, reduces light deflection angle, lowers system sensitivity, and helps improve production yield.

[0068] In a preferred embodiment of the present invention, the effective focal length F4 of the fourth lens L4 and the effective focal length F5 of the fifth lens L5 satisfy: -3.68 ≤ F4 / F5 ≤ -0.15. More preferably, it satisfies: -0.65 ≤ F4 / F5 ≤ -0.15. This helps to balance various aberrations, improve image quality, and also correct distortions, reducing image deformation.

[0069] In a preferred embodiment of the present invention, the effective focal length F5 of the fifth lens L5 and the total effective focal length F of the fixed-focus lens satisfy: -1.28 ≤ F5 / F ≤ -1.10. This helps to balance the spherical aberration and astigmatism produced by the first to fourth lenses in the optical system, thereby improving image quality.

[0070] In a preferred embodiment of the present invention, the effective focal length F6 of the sixth lens L6 and the total effective focal length F of the fixed-focus lens satisfy: |F6 / F|≤15.57. This introduces positive distortion, which helps to balance the negative distortion value generated by the fifth lens and reduces the degree of image distortion.

[0071] In a preferred embodiment of the present invention, the combined effective focal length F78 of the seventh lens L7 and the eighth lens L8, and the total effective focal length F of the fixed-focus lens satisfy: -14.50 ≤ F78 / F ≤ 4.00. This effectively corrects optical distortion, ensuring that the absolute value of optical distortion is ≤ 3.1%, while simultaneously improving optical imaging performance.

[0072] In a preferred embodiment of the present invention, the object-side radius of curvature R61 and the image-side radius of curvature R62 of the sixth lens L6 satisfy: 0.55 ≤ |R61 / R62| ≤ 6.30. This helps to balance the various aberrations produced by the lenses in the object-side direction of the sixth lens L6, thereby improving the optical imaging quality.

[0073] In a preferred embodiment of the present invention, the object-side radius of curvature R61 of the sixth lens L6, the image-side radius of curvature R62 of the sixth lens L6, and the total effective focal length F of the fixed-focus lens satisfy: -0.65 ≤ (R61 + R62) / F ≤ 5.96. This effectively controls the direction of light, elevates the light path, and improves illumination while meeting the image size requirements.

[0074] In a preferred embodiment of the present invention, the center thickness d3 of the third lens L3 on the optical axis, the center thickness d4 of the fourth lens L4 on the optical axis, the center thickness d5 of the fifth lens L5 on the optical axis, and the total optical length TTL of the fixed-focus lens satisfy: 0.25≤(d3+d4+d5) / TTL≤0.34. This allows each lens to have better manufacturability, which is beneficial for reducing the sensitivity of the optical lens; at the same time, it helps to reduce the air gap between the lenses, thereby reducing the total length of the optical system, making the total optical system length TTL≤15mm, which is beneficial for lens miniaturization.

[0075] In a preferred embodiment of the present invention, the total optical length (TTL) and half-image height (H) of the fixed-focus lens satisfy the following condition: 3.85 ≤ TTL / H ≤ 4.75. With a fixed image height, reasonably setting the total optical length of the lens facilitates lens miniaturization.

[0076] In a preferred embodiment of the present invention, the optical back focal length (BFL) of the fixed-focus lens (i.e., the distance from the center of the image-side surface of the eighth lens L8 to the center of the image plane IMA) and the total optical length (TTL) of the fixed-focus lens satisfy the following condition: 0.15 ≤ BFL / TTL ≤ 0.18. This improves the assembly yield of the optical lens and also helps to reserve space for the installation of optical components, facilitating lens assembly.

[0077] In a preferred embodiment of the present invention, the effective focal length F and the entrance pupil diameter EPD of the fixed-focus lens satisfy the condition: F / EPD≤1.80. This allows for the achievement of a large aperture FNO≤1.80 for the optical lens by reasonably controlling the entrance pupil diameter.

[0078] The fixed-focus lens of this invention employs eight lenses. By matching the positive and negative optical powers and shapes of each lens, and by setting appropriate parameters such as dispersion coefficient and thickness, the optical lens simultaneously achieves the beneficial effects of low distortion, large aperture, small size, and high resolution. The fixed-focus lens of this invention can achieve a large aperture FNO ≤ 1.80, full-field optical distortion ≤ |-3.1%|, and a total lens length TTL ≤ 15mm.

[0079] The fixed-focus lens of this invention can be applied to all fixed-focus lens application scenarios, such as video conferencing lenses.

[0080] The fixed-focus lens of the present invention will be specifically described below with reference to four embodiments, accompanying drawings, and tables. In the following embodiments, the aperture stop STO is referred to as one side, and the image plane IMA is referred to as another side.

[0081] The parameters for each embodiment that meets the above conditions are shown in Table 1:

[0082] Conditional expression Example 1 Example 2 Example 3 Example 4 -2.60≤F1 / F≤-1.30 -1.604 -2.863 -2.577 -1.993 1.42≤(R11+R12) / (R11-R12)≤3.00 1.785 2.812 1.655 2.272 0.55≤|(R11+R12) / F1|≤5.89 1.586 0.773 1.874 1.025 0.87≤F345 / F≤3.50 3.100 1.367 1.241 2.001 0.30≤F4 / F≤4.45 0.619 0.605 0.594 3.810 -3.68≤F4 / F5≤-0.15 -0.531 -0.510 -0.473 -3.149 -1.28≤F5 / F≤-1.10 -1.166 -1.187 -1.256 -1.210 |F6 / F|≤15.57 1.415 13.210 8.330 1.781 -14.50≤F78 / F≤4.00 -14.434 2.331 2.668 -9.949 0.55≤|R61 / R62|≤6.30 0.706 1.353 1.536 5.348 -0.65≤(R61+R62) / F≤5.96 -0.520 4.794 4.466 4.882 0.25≤(d3+d4+d5) / TTL≤0.34 0.248 0.247 0.247 0.321 3.85≤TTL / H≤4.75 3.942 4.618 4.546 4.045 0.15≤BFL / TTL≤0.18 0.155 0.173 0.173 0.158 F / EPD≤1.80 1.80 1.80 1.80 1.80

[0083] Table 1

[0084] In an embodiment of the present invention, the aspherical lens of the fixed-focus lens satisfies the following formula:

[0085] In the above formula, z is the axial distance from the vertex to the surface at a position perpendicular to the optical axis at a height y; c represents the curvature at the vertex of the aspherical surface; k is the conic coefficient; A4, A6, A8, A 10 A 12 A 14 A 16 ...represent aspheric coefficients of the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders, respectively.

[0086] Example 1

[0087] like Figure 1 The image shown is a schematic diagram of the optical structure of a fixed-focus lens according to Embodiment 1 of the present invention. In this embodiment:

[0088] The first lens L1 is a convex-concave lens with negative optical power.

[0089] The second lens L2 is a convex-convex lens with positive optical power.

[0090] The third lens, L3, is a convex-concave lens with negative optical power.

[0091] The fourth lens, L4, is a convex-convex lens with positive optical power.

[0092] The fifth lens, L5, is a convex-concave lens with negative optical power.

[0093] The sixth lens, L6, is a convex-convex lens with positive optical power.

[0094] The seventh lens, L7, is a concave-convex lens with negative optical power.

[0095] The eighth lens, L8, is a convex-concave lens with negative optical power.

[0096] The first lens L1, the third lens L3, and the fourth lens L4 are glass spherical lenses, while the second lens L2, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8 are plastic aspherical lenses.

[0097] The aperture stop STO is located between the second lens L2 and the third lens L3. The third lens L3 and the fourth lens L4 are cemented together.

[0098] In this embodiment, the surface type, radius of curvature R, thickness d, refractive index Nd, and Abbe number Vd of each facet of the fixed-focus lens are shown in Table 2:

[0099]

[0100]

[0101] Table 2

[0102] In this embodiment, the K-value and aspherical coefficient of the fixed-focus lens are shown in Table 3:

[0103] Face number K value A4 A6 A8 A10 A12 A14 A16 3 11.67 -3.23E-03 7.30E-04 -4.17E-04 1.26E-04 -1.53E-05 0.00E+00 0.00E+00 4 10.75 9.14E-04 -2.14E-04 4.94E-04 -1.47E-04 2.27E-05 0.00E+00 0.00E+00 9 -3.16 -2.80E-02 9.41E-03 -2.55E-03 4.51E-04 -3.68E-05 0.00E+00 0.00E+00 10 -1.14 -3.55E-02 1.29E-02 -3.41E-03 5.81E-04 -3.76E-05 0.00E+00 0.00E+00 11 -9.62 -6.77E-03 -1.46E-03 2.71E-04 -1.69E-04 2.74E-05 0.00E+00 0.00E+00 12 -0.84 -1.09E-02 5.27E-03 -3.00E-03 5.57E-04 -3.75E-05 0.00E+00 0.00E+00 13 -6.21 7.53E-03 1.24E-03 -6.52E-04 9.33E-05 -4.02E-06 0.00E+00 0.00E+00 14 -1.07 3.45E-02 -9.28E-03 2.87E-03 -4.78E-04 3.03E-05 0.00E+00 0.00E+00 15 -1.54 -5.30E-02 8.52E-03 -1.41E-03 1.29E-04 -6.25E-06 0.00E+00 0.00E+00 16 -4.51 -2.05E-02 2.80E-03 -4.59E-04 3.82E-05 -1.36E-06 0.00E+00 0.00E+00

[0104] Table 3

[0105] Combination Figure 1-2 As shown in Tables 1-3 above, this embodiment achieves an absolute optical distortion of 3.08% and a large aperture FNO of 1.80 by reasonably allocating the lens power, shape, and optical parameters. It can simultaneously achieve low distortion, large aperture, miniaturization, low cost, and high resolution.

[0106] Example 2

[0107] like Figure 3 The image shown is a schematic diagram of the optical structure of a fixed-focus lens according to Embodiment 2 of the present invention. In this embodiment:

[0108] The first lens L1 is a convex-concave lens with negative optical power.

[0109] The second lens L2 is a concave-convex lens with positive optical power.

[0110] The third lens L3 is a convex-concave lens with positive optical power.

[0111] The fourth lens, L4, is a convex-convex lens with positive optical power.

[0112] The fifth lens, L5, is a concave-convex lens with negative optical power.

[0113] The sixth lens, L6, is a convex-concave lens with negative optical power.

[0114] The seventh lens, L7, is a concave-convex lens with positive optical power.

[0115] The eighth lens, L8, is a convex-concave lens with negative optical power.

[0116] The first lens L1, the fourth lens L4, and the fifth lens L5 are glass spherical lenses, while the second lens L2, the third lens L3, the sixth lens L6, the seventh lens L7, and the eighth lens L8 are plastic aspherical lenses.

[0117] The aperture stop STO is located between the third lens L3 and the fourth lens L4. The fourth lens L4 and the fifth lens L5 are cemented together.

[0118] In this embodiment, the surface type, radius of curvature R, thickness d, refractive index Nd, and Abbe number Vd of each facet of the fixed-focus lens are shown in Table 4:

[0119] Face number Surface type radius of curvature R Thickness d Refractive index Nd Abbe number Vd 1 spherical 6.575 0.50 1.50 81.61 2 spherical 3.125 1.88 3 aspherical -6.172 1.02 1.54 55.71 4 aspherical -6.362 0.05 5 aspherical 2.908 1.25 1.64 23.53 6 aspherical 2.545 0.55 7(STO) spherical Infinity 0.38 8 spherical 8.418 1.96 1.80 46.57 9 spherical -2.576 0.50 1.85 23.79 10 spherical -6.67 0.05 11 aspherical 12.084 0.68 1.64 23.53 12 aspherical 8.932 1.40 13 aspherical -3.486 1.03 1.54 55.71 14 aspherical -2.119 0.05 15 aspherical 3.337 1.11 1.64 23.53 16 aspherical 2.338 1.79 17 spherical Infinity 0.60 1.52 64.21 18 spherical Infinity 0.20 19(IMA) spherical Infinity 0.00

[0120] Table 4

[0121] In this embodiment, the K-value and aspherical coefficient of the fixed-focus lens are shown in Table 5:

[0122]

[0123]

[0124] Table 5

[0125] Combination Figure 3-4 As shown in Tables 1, 4, and 5 above, this embodiment achieves an absolute optical distortion of 0.75% and a large aperture FNO of 1.80 by reasonably allocating the lens power, shape, and optical parameters. It can simultaneously achieve low distortion, large aperture, miniaturization, low cost, and high resolution.

[0126] Example 3

[0127] like Figure 5 The image shown is a schematic diagram of the optical structure of a fixed-focus lens according to Embodiment 3 of the present invention. In this embodiment:

[0128] The first lens L1 is a convex-concave lens with negative optical power.

[0129] The second lens L2 is a concave-convex lens with positive optical power.

[0130] The third lens L3 is a convex-concave lens with positive optical power.

[0131] The fourth lens, L4, is a convex-convex lens with positive optical power.

[0132] The fifth lens, L5, is a concave-convex lens with negative optical power.

[0133] The sixth lens, L6, is a convex-concave lens with negative optical power.

[0134] The seventh lens, L7, is a concave-convex lens with positive optical power.

[0135] The eighth lens, L8, is a convex-concave lens with negative optical power.

[0136] The first lens L1, the fourth lens L4, and the fifth lens L5 are glass spherical lenses, while the second lens L2, the third lens L3, the sixth lens L6, the seventh lens L7, and the eighth lens L8 are plastic aspherical lenses.

[0137] The aperture stop STO is located between the third lens L3 and the fourth lens L4. The fourth lens L4 and the fifth lens L5 are cemented together.

[0138] In this embodiment, the surface type, radius of curvature R, thickness d, refractive index Nd, and Abbe number Vd of each facet of the fixed-focus lens are shown in Table 6:

[0139]

[0140]

[0141] Table 6

[0142] In this embodiment, the K-value and aspherical coefficient of the fixed-focus lens are shown in Table 7:

[0143] Face number K value A4 A6 A8 A10 A12 A14 A16 3 -22.32 9.35E-03 -7.73E-04 -1.57E-06 2.61E-06 -3.44E-07 0.00E+00 0.00E+00 4 -33.46 9.28E-03 2.31E-04 -1.88E-04 4.81E-06 1.38E-07 0.00E+00 0.00E+00 5 -1.50 5.15E-03 -2.30E-04 3.11E-04 -1.06E-05 -5.18E-06 0.00E+00 0.00E+00 6 0.96 -2.62E-02 4.87E-03 -1.42E-03 5.47E-04 -1.86E-04 0.00E+00 0.00E+00 11 26.93 -1.21E-02 -1.15E-04 2.41E-04 3.34E-05 -5.86E-06 0.00E+00 0.00E+00 12 3.62 -1.19E-02 1.79E-05 2.76E-04 -1.43E-05 5.10E-06 0.00E+00 0.00E+00 13 -3.55 2.00E-02 -6.55E-03 1.92E-03 -2.70E-04 1.44E-05 0.00E+00 0.00E+00 14 -0.97 2.95E-02 -5.47E-03 1.27E-03 -1.25E-04 3.32E-06 0.00E+00 0.00E+00 15 -0.39 -2.65E-02 2.61E-03 -2.86E-04 1.10E-05 3.98E-08 0.00E+00 0.00E+00 16 -9.86 -1.30E-02 1.35E-03 -1.56E-04 8.81E-06 -1.75E-07 0.00E+00 0.00E+00

[0144] Table 7

[0145] Combination Figure 5-6 As shown in Tables 1, 6, and 7 above, this embodiment achieves an absolute optical distortion of 1.95% and a large aperture FNO of 1.80 by reasonably allocating the lens power, shape, and optical parameters. It can simultaneously achieve low distortion, large aperture, miniaturization, low cost, and high resolution.

[0146] Example 4

[0147] like Figure 7 The image shown is a schematic diagram of the optical structure of a fixed-focus lens according to Embodiment 4 of the present invention. In this embodiment:

[0148] The first lens L1 is a convex-concave lens with negative optical power.

[0149] The second lens L2 is a concave-convex lens with positive optical power.

[0150] The third lens, L3, is a convex-convex lens with positive optical power.

[0151] The fourth lens, L4, is a concave-convex lens with positive optical power.

[0152] The fifth lens, L5, is a convex-concave lens with negative optical power.

[0153] The sixth lens, L6, is a convex-convex lens with positive optical power.

[0154] The seventh lens, L7, is a concave-convex lens with negative optical power.

[0155] The eighth lens, L8, is a convex-concave lens with positive optical power.

[0156] The first lens L1 and the third lens L3 are glass spherical lenses, while the second lens L2, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7 and the eighth lens L8 are plastic aspherical lenses.

[0157] The aperture stop STO is located between the second lens L2 and the third lens L3. It is a non-cemented lens.

[0158] In this embodiment, the surface type, radius of curvature R, thickness d, refractive index Nd, and Abbe number Vd of each facet of the fixed-focus lens are shown in Table 8:

[0159]

[0160]

[0161] Table 8

[0162] In this embodiment, the K-value and aspherical coefficient of the fixed-focus lens are shown in Table 9:

[0163] Face number K value A4 A6 A8 A10 A12 A14 A16 3 0.25 -3.79E-03 5.59E-04 -2.16E-04 8.63E-05 -2.06E-05 1.96E-06 0.00E+00 4 -8.69 -2.84E-02 9.22E-03 -2.84E-03 6.34E-04 -8.69E-05 5.40E-06 0.00E+00 8 -45.52 1.01E-02 -2.93E-03 2.38E-04 -4.60E-05 0.00E+00 0.00E+00 0.00E+00 9 -18.17 -1.62E-03 -3.45E-03 4.55E-04 -3.32E-05 0.00E+00 0.00E+00 0.00E+00 10 -20.29 -4.13E-02 5.21E-03 1.69E-04 -6.38E-05 1.91E-06 1.73E-07 0.00E+00 11 -4.79 -1.48E-02 5.57E-03 -1.05E-03 1.53E-04 1.97E-06 -2.03E-06 0.00E+00 12 41.40 1.12E-02 -9.49E-04 1.57E-04 1.06E-05 -2.07E-07 -3.16E-07 0.00E+00 13 -0.36 -1.38E-02 1.51E-02 -3.00E-03 2.54E-04 7.18E-06 -2.93E-06 0.00E+00 14 0.08 4.31E-02 3.93E-03 -1.54E-03 1.46E-04 8.50E-06 -9.94E-07 0.00E+00 15 -0.51 2.42E-02 1.20E-03 -8.66E-04 1.50E-04 -1.18E-05 3.50E-07 0.00E+00 16 -0.58 -4.77E-02 4.17E-03 -1.28E-04 -3.06E-06 0.00E+00 0.00E+00 0.00E+00 17 -2.62 -2.60E-02 2.57E-03 -1.18E-04 6.97E-07 0.00E+00 0.00E+00 0.00E+00

[0164] Table 9

[0165] Combination Figure 7-8 As shown in Tables 1, 8, and 9 above, this embodiment achieves an absolute optical distortion of 2.90% and a large aperture FNO of 1.80 by reasonably allocating the lens power, shape, and optical parameters. It can simultaneously achieve low distortion, large aperture, miniaturization, low cost, and high resolution.

[0166] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fixed-focus lens, comprising, in sequence along the optical axis from the object side to the image side, a first lens (L1), a second lens (L2), a third lens (L3), a fourth lens (L4), a fifth lens (L5), a sixth lens (L6), a seventh lens (L7), and an eighth lens (L8), characterized in that, The optical power of the first lens (L1) and the fifth lens (L5) is negative; The optical power of the second lens (L2) and the fourth lens (L4) is positive; The optical power of the third lens (L3), the seventh lens (L7), and the eighth lens (L8) is negative, while the optical power of the sixth lens (L6) is positive. Alternatively, the optical power of the third lens (L3) and the seventh lens (L7) are both positive, and the optical power of the sixth lens (L6) and the eighth lens (L8) are both negative; Alternatively, the optical power of the third lens (L3), the sixth lens (L6), and the eighth lens (L8) can all be positive, while the optical power of the seventh lens (L7) can be negative.

2. The fixed-focus lens according to claim 1, characterized in that, The first lens (L1) and the eighth lens (L8) are convex-concave lenses, the image side of the second lens (L2) and the fourth lens (L4) is convex, the object side of the third lens (L3) and the sixth lens (L6) is convex, and the seventh lens (L7) is a concave-convex lens.

3. The fixed-focus lens according to claim 1, characterized in that, The fifth lens (L5) is a convex-concave lens or a concave-convex lens.

4. The fixed-focus lens according to any one of claims 1-3, characterized in that, The effective focal length F1 of the first lens (L1) and the total effective focal length F of the fixed-focus lens satisfy the following: -2.60≤F1 / F≤-1.

30.

5. The fixed-focus lens according to any one of claims 1-3, characterized in that, The object-side surface curvature radius R11 and the image-side surface curvature radius R12 of the first lens (L1) satisfy the following: 1.42≤(R11+R12) / (R11-R12)≤3.

00.

6. The fixed-focus lens according to any one of claims 1-3, characterized in that, The object-side radius of curvature R11, the image-side radius of curvature R12, and the effective focal length F1 of the first lens (L1) satisfy the following: 0.55≤|(R11+R12) / F1|≤5.

89.

7. The fixed-focus lens according to any one of claims 1-3, characterized in that, The combined effective focal length F345 of the third lens (L3) to the fifth lens (L5) and the total effective focal length F of the fixed-focus lens satisfy the following: 0.87≤F345 / F≤3.

50.

8. The fixed-focus lens according to any one of claims 1-3, characterized in that, The effective focal length F4 of the fourth lens (L4) and the total effective focal length F of the fixed-focus lens satisfy the following: 0.30≤F4 / F≤4.

45.

9. The fixed-focus lens according to any one of claims 1-3, characterized in that, The effective focal length F4 of the fourth lens (L4) and the effective focal length F5 of the fifth lens (L5) satisfy the following: -3.68≤F4 / F5≤-0.

15.

10. The fixed-focus lens according to any one of claims 1-3, characterized in that, The effective focal length F5 of the fifth lens (L5) and the total effective focal length F of the fixed-focus lens satisfy the following: -1.28≤F5 / F≤-1.

10.

11. The fixed-focus lens according to any one of claims 1-3, characterized in that, The effective focal length F6 of the sixth lens (L6) and the total effective focal length F of the fixed-focus lens satisfy the following: |F6 / F|≤15.

57.

12. The fixed-focus lens according to any one of claims 1-3, characterized in that, The combined effective focal length F78 of the seventh lens (L7) and the eighth lens (L8) and the total effective focal length F of the fixed-focus lens satisfy the following: -14.50≤F78 / F≤4.

00.

13. The fixed-focus lens according to any one of claims 1-3, characterized in that, The object-side surface curvature radius R61 and the image-side surface curvature radius R62 of the sixth lens (L6) satisfy the following: 0.55≤|R61 / R62|≤6.

30.

14. The fixed-focus lens according to any one of claims 1-3, characterized in that, The object-side surface curvature radius R61 of the sixth lens (L6), the image-side surface curvature radius R62 of the sixth lens (L6), and the total effective focal length F of the fixed-focus lens satisfy the following: -0.65≤(R61+R62) / F≤5.

96.

15. The fixed-focus lens according to any one of claims 1-3, characterized in that, The center thickness d3 of the third lens (L3), the center thickness d4 of the fourth lens (L4), the center thickness d5 of the fifth lens (L5), and the total optical length TTL of the fixed-focus lens satisfy the following: 0.25≤(d3+d4+d5) / TTL≤0.

34.

16. The fixed-focus lens according to any one of claims 1-3, characterized in that, The total optical length TTL of the fixed-focus lens and the half-image height H of the fixed-focus lens satisfy the following: 3.85≤TTL / H≤4.

75.

17. The fixed-focus lens according to any one of claims 1-3, characterized in that, The optical back focal length (BFL) and the total optical length (TTL) of the fixed-focus lens satisfy the following: 0.15≤BFL / TTL≤0.

18.

18. The fixed-focus lens according to any one of claims 1-3, characterized in that, The effective focal length F of the fixed-focus lens and the entrance pupil diameter EPD of the fixed-focus lens satisfy the following: F / EPD≤1.80.

Images