A fixed focus lens

Abstract

The present invention relates to a fixed-focus lens, comprising a first lens group (11) and a second lens group (12) arranged in sequence from the object side to the image side; along the direction from the object side to the image side, the first lens group (11) comprises: a first lens (111) with negative optical focal length, a second lens (112) with negative optical focal length, a third lens (113) with positive optical focal length and a fourth lens (114) with positive optical focal length; along the direction from the object side to the image side, the second lens group (12) comprises: a fifth lens (121) with negative optical focal length, a sixth lens (122) with positive optical focal length, a seventh lens (123) with negative optical focal length, an eighth lens (124) with positive optical focal length and a ninth lens (125) with positive optical focal length. The lenses of the present invention meet the above optical focal length matching, thereby enabling the fixed-focus lens to have the ability to simultaneously image visible and near-infrared spectra and have an ultra-long back focal ratio.

Description

Technical Field

[0001] The present invention relates to the field of optics, and in particular to a fixed-focus lens. Background Art

[0002] At present, infrared and visible light confocal lenses generally have the following disadvantages: low lens pixels, high and low temperature defocus, and many noise points in low light environments. In addition, in order to overcome the above disadvantages, existing infrared and visible light confocal lenses mostly need to use some expensive abnormal dispersion and high refractive index lenses to achieve clear imaging on the confocal plane. This kind of lens is not only difficult to design and has high development costs, but also difficult to image infrared and visible light at the best resolution at the same time. Summary of the invention

[0003] The purpose of the present invention is to provide a fixed-focus lens to solve the problem of poor imaging quality.

[0004] To achieve the above-mentioned object of the invention, the present invention provides a fixed-focus lens, comprising a first lens group and a second lens group arranged in sequence from the object side to the image side;

[0005] Along the direction from the object side to the image side, the first lens group includes: a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power and a fourth lens with positive optical power;

[0006] Along the direction from the object side to the image side, the second lens group includes: a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with negative optical power, an eighth lens with positive optical power and a ninth lens with positive optical power.

[0007] According to one aspect of the present invention, it also includes: a spectrometer:

[0008] Along the direction from the object side to the image side, the first lens group, the second lens group and the beam splitter are arranged in sequence;

[0009] The beam splitter is a prism beam splitter.

[0010] According to one aspect of the present invention, the interval distance between the first lens group and the second lens group is Lg, and the total length of the fixed-focus lens is Lt, then: 3<Lg / Lt<5 is satisfied.

[0011] According to one aspect of the present invention, the radius of curvature of the object side surface of the second lens is R2a, and the radius of curvature of the image side surface of the first lens is R1b, then: -2<R2a / R1b<-1.

[0012] According to one aspect of the present invention, the focal length of the first lens group is fI, and the focal length of the second lens group is fII, then: 3<fI / fII<11 is satisfied.

[0013] According to one aspect of the present invention, the focal length of the first lens group is fI, and the focal length of the fourth lens is f4, then: 3<fI / f4<10 is satisfied.

[0014] According to one aspect of the present invention, the focal length of the second lens group is fII, and the focal length of the ninth lens is f9, then: 1<f9 / fII<1.5 is satisfied.

[0015] According to one aspect of the present invention, the refractive index of the material of the fifth lens for the d-line spectrum is Nd5, and the refractive index of the material of the sixth lens for the d-line spectrum is Nd6, which satisfies: 1.1<(Nd5-1) / (Nd6-1)<1.8.

[0016] According to one aspect of the present invention, the refractive index of the material of the seventh lens for the d-line spectrum is Nd7, and the refractive index of the material of the eighth lens for the d-line spectrum is Nd8, which satisfies 1.2<(Nd7-1) / (Nd8-1)<1.9.

[0017] According to one aspect of the present invention, the third lens is a biconvex lens; and / or,

[0018] The fifth lens is a biconcave lens; and / or,

[0019] The seventh lens is a convex-concave lens.

[0020] According to one aspect of the present invention, it also includes: an aperture: along the direction from the object side to the image side, the first lens group, the aperture, and the second lens group are arranged in sequence.

[0021] According to a solution of the present invention, each lens satisfies the above-mentioned combination of optical focal lengths, thereby enabling the fixed-focus lens to have the ability to simultaneously image the visible and near-infrared spectra, and to have an ultra-long back focal ratio. At the same time, through the above-mentioned setting, the fixed-focus lens of the present invention can realize the temperature compensation function under different ambient temperatures, and still have good resolution under large aperture conditions, achieving a clear imaging effect.

[0022] According to one solution of the present invention, the ratio of the spacing distance between the first lens group and the second lens group to the total length of the fixed-focus lens is set within the above-mentioned range, which is further conducive to achieving an ultra-long back focal ratio of the fixed-focus lens of the present invention and can provide sufficient space for the rear end structure design of the fixed-focus lens of the present invention.

[0023] According to a solution of the present invention, the ratio of the curvature radii of the two opposite surfaces of the first lens and the second lens is within the above range, which is beneficial to improving the efficiency of the fixed-focus lens of the present invention in converging light, and can effectively reduce the volume of the front end of the lens, which can not only effectively reduce the injection of external stray light and ensure the imaging quality, but also effectively reduce the manufacturing cost of the present invention.

[0024] According to a solution of the present invention, the focal power distribution between the first lens group and the second lens group satisfies the above conditions, so that the number and volume distribution of lenses between the groups of the fixed-focus lens of the present invention are more reasonable, ensuring that the center of gravity of the fixed-focus lens is located at a reasonable position. At the same time, the above arrangement is also conducive to reducing the assembly tolerance of the group components, which is beneficial to improving the assemblability of the present invention.

[0025] According to one solution of the present invention, an optimized distribution of the optical focal length of the lenses in the first lens group is achieved, so that the fixed-focus lens of the present invention reduces the overall length of the first lens group while ensuring a larger field of view, which not only effectively improves the efficiency of the fixed-focus lens of the present invention in transmitting light, but also effectively reduces the production cost of the present invention.

[0026] According to a solution of the present invention, the optimal distribution of the optical power of the lenses in the second lens group is achieved, so that the fixed-focus lens of the present invention has a sufficient back focus length, thereby improving the back focus ratio of the fixed-focus lens of the present invention.

[0027] According to one solution of the present invention, by setting the fifth lens as a biconcave lens, the efficiency of light transmission of the second lens group of the lens can be further improved, which is beneficial to the correction of aberrations by the second lens group. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The structure of a fixed-focus lens according to an embodiment of the present invention is schematically shown;

[0029] Figure 2 A schematic diagram showing the structure of the fixed-focus lens in the first embodiment;

[0030] Figure 3 The visible spectrum MTF curve of the fixed-focus lens in Example 1 is schematically shown;

[0031] Figure 4 The infrared spectrum MTF curve of the fixed-focus lens in Example 1 is schematically shown;

[0032] Figure 5 A schematic diagram showing the structure of a fixed-focus lens in Embodiment 2;

[0033] Figure 6 The visible spectrum MTF curve of the fixed-focus lens in Example 2 is schematically shown;

[0034] Figure 7 The infrared spectrum MTF curve of the fixed-focus lens in Example 2 is schematically shown;

[0035] Figure 8 The structure of the fixed-focus lens in the third embodiment is schematically shown;

[0036] Fig. 9 The visible spectrum MTF curve of the fixed-focus lens in Example 3 is schematically shown;

[0037] Fig.10 The infrared spectrum MTF curve of the fixed-focus lens in Example 3 is schematically shown;

[0038] Fig.11 A schematic diagram showing the structure of a fixed-focus lens in Embodiment 4;

[0039] Fig.12 The visible spectrum MTF curve of the fixed-focus lens in Example 4 is schematically shown;

[0040] Fig.13 The infrared spectrum MTF curve of the fixed-focus lens in Example 4 is schematically shown;

[0041] Fig.14 The structure of the fixed-focus lens in the fifth embodiment is schematically shown;

[0042] Fig.15 The visible spectrum MTF curve of the fixed-focus lens in Example 5 is schematically shown;

[0043] Fig.16 The infrared spectrum MTF curve of the fixed-focus lens in Example 5 is schematically shown. DETAILED DESCRIPTION

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0046] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not therefore limited to the following embodiments.

[0047] like Figure 1 As shown, according to an embodiment of the present invention, a fixed-focus lens of the present invention comprises a first lens group 11 and a second lens group 12 which are sequentially arranged from the object side to the image side. In this embodiment, along the direction from the object side to the image side, the first lens group 11 comprises: a first lens 111 with negative optical power, a second lens 112 with negative optical power, a third lens 113 with positive optical power and a fourth lens 114 with positive optical power; in this embodiment, along the direction from the object side to the image side, the second lens group 12 comprises: a fifth lens 121 with negative optical power, a sixth lens 122 with positive optical power, a seventh lens 123 with negative optical power, an eighth lens 124 with positive optical power and a ninth lens 125 with positive optical power. Through the fixed-focus lens arranged as above, each lens thereof satisfies the above optical power matching, thereby enabling the fixed-focus lens to have the ability to simultaneously image the visible and near-infrared spectra, and to have an ultra-long back focal ratio. At the same time, the above-mentioned setting enables the fixed-focus lens of the present invention to realize the temperature compensation function at different ambient temperatures, and still has good resolution under a large aperture state, thereby achieving a clear imaging effect.

[0048] like Figure 1 As shown, according to an embodiment of the present invention, the spacing distance between the first lens group 11 and the second lens group 12 is Lg, and the total length of the fixed-focus lens is Lt, then: 3<Lg / Lt<5. In this embodiment, the spacing distance Lg between the first lens group 11 and the second lens group 12 refers to the distance between the image side vertex of the fourth lens 114 and the object side vertex of the fifth lens 121. The total length Lt of the fixed-focus lens refers to the distance between the object side vertex of the first lens 111 and the imaging surface vertex of the first imaging sensor A. Through the above arrangement, the proportional relationship between the spacing distance between the first lens group 11 and the second lens group 12 and the total length of the fixed-focus lens is set within the above range, which is further conducive to achieving the ultra-long back focal ratio of the fixed-focus lens of the present invention, and can provide sufficient space for the rear end structure design of the fixed-focus lens of the present invention.

[0049] like Figure 1As shown, according to an embodiment of the present invention, the radius of curvature of the object side of the second lens 112 is R2a, and the radius of curvature of the image side of the first lens 111 is R1b, then: -2<R2a / R1b<-1. Through the above arrangement, the ratio of the radius of curvature of the two opposite surfaces between the first lens and the second lens is within the above range, which is beneficial to improving the efficiency of the fixed-focus lens of the present invention in converging light, and can effectively reduce the volume of the front end of the lens, which can not only effectively reduce the injection of external stray light and ensure the imaging quality, but also effectively reduce the manufacturing cost of the present invention.

[0050] like Figure 1 As shown, according to an embodiment of the present invention, the focal length of the first lens group 11 is fI, and the focal length of the second lens group 12 is fII, then: 3<fI / fII<11. Through the above arrangement, the focal power distribution between the first lens group and the second lens group meets the above conditions, so that the number and volume distribution of lenses between the groups of the fixed-focus lens of the present invention are more reasonable, ensuring that the center of gravity of the fixed-focus lens is located at a reasonable position. At the same time, the above arrangement is also conducive to reducing the assembly tolerance of the group components, which is beneficial to improving the assemblability of the present invention.

[0051] like Figure 1 As shown, according to an embodiment of the present invention, the focal length of the first lens group 11 is fI, and the focal length of the fourth lens 114 is f4, which satisfies: 3<fI / f4<10. Through the above arrangement, the optimal distribution of the lens power in the first lens group is achieved, so that the fixed-focus lens of the present invention reduces the overall length of the first lens group while ensuring a larger field of view, which not only effectively improves the efficiency of the fixed-focus lens of the present invention in transmitting light, but also effectively reduces the production cost of the present invention.

[0052] like Figure 1 As shown, according to an embodiment of the present invention, the focal length of the second lens group 12 is fII, and the focal length of the ninth lens 125 is f9, then: 1<f9 / fII<1.5. Through the above arrangement, the optimal distribution of the lens power in the second lens group is achieved, so that the fixed-focus lens of the present invention has a sufficient back focal length, and the back focal ratio of the fixed-focus lens of the present invention is improved.

[0053] like Figure 1As shown, according to one embodiment of the present invention, the refractive index of the material of the fifth lens 121 for the spectral d-line is Nd5, and the refractive index of the material of the sixth lens 122 for the spectral d-line is Nd6, which satisfies: 1.1<(Nd5-1) / (Nd6-1)<1.8. It should be pointed out that the spectral d-line refers to the green light in the spectrum. Through the above settings, the materials of the fifth lens and the sixth lens are optimized, thereby effectively correcting the chromatic aberration of the fixed-focus lens in the present invention, and facilitating the temperature compensation function of the lens, which is beneficial to improving the imaging quality of the present invention.

[0054] like Figure 1 As shown, according to an embodiment of the present invention, the refractive index of the material of the seventh lens 123 for the spectral d-line is Nd7, and the refractive index of the material of the eighth lens 124 for the spectral d-line is Nd8, which satisfies 1.2<(Nd7-1) / (Nd8-1)<1.9. Through the above configuration, the materials of the seventh lens and the eighth lens are optimized and matched, which can further correct the chromatic aberration of the present invention, so that the present invention can clearly image both the visible and near-infrared spectra, thereby improving the imaging quality of the present invention.

[0055] like Figure 1 As shown, according to one embodiment of the present invention, the third lens 113 is a biconvex lens. Through the above arrangement, sufficient positive focal power can be provided to the first lens group, and the chromatic aberration of the first lens group can be effectively corrected in combination with the second lens, which is beneficial to improving the imaging quality.

[0056] like Figure 1 As shown, according to an embodiment of the present invention, the fifth lens 121 is a biconcave lens. By setting the fifth lens as a biconcave lens, the efficiency of light transmission of the second lens group of the lens can be further improved, which is beneficial to the correction of aberrations by the second lens group.

[0057] like Figure 1 As shown, according to one embodiment of the present invention, the seventh lens 123 is a convex-concave lens. Through the above configuration, the seventh lens of this shape is small in size and does not occupy too much lens space. While reducing the lens volume, it can effectively correct the chromatic aberration of the second lens group when combined with the eighth lens, which is beneficial to improving the imaging quality.

[0058] like Figure 1 As shown, according to an embodiment of the present invention, the fixed focus lens of the present invention further includes: an aperture 13. In this embodiment, along the direction from the object side to the image side, the first lens group 11, the aperture 13, and the second lens group 12 are arranged in sequence, that is, the aperture 13 is located between the first lens group 11 and the second lens group 12.

[0059] like Figure 2As shown, according to an embodiment of the present invention, the fixed-focus lens of the present invention further includes: a beam splitter 14. In this embodiment, along the direction from the object side to the image side, the first lens group 11, the second lens group 12 and the beam splitter 14 are arranged in sequence, that is, the beam splitter 14 is located on the object side of the second lens group 12. In this embodiment, the beam splitter 14 is a prism beam splitter. In this embodiment, since the beam splitter 14 is used, when the fixed-focus lens of the present invention is used to capture an image, two imaging sensors, namely the first imaging sensor A and the second imaging sensor B, can be correspondingly arranged. The images of sensors A and B are then synthesized and processed to synchronously obtain images in a wide spectral range. When used for visible and near-infrared spectral imaging, the above-mentioned imaging sensors can be adjusted accordingly.

[0060] In order to explain the present invention in more detail, examples of the present invention are given.

[0061] According to the above content of the present invention, the numerical values ​​of the embodiments of the fixed focus lens of the present invention that meet the above formula are summarized as shown in Table 1 below:

[0062]

[0063] Embodiment 1:

[0064] based on Figure 2 The structure of the fixed focus lens shown in FIG. Figure 2 As shown, for the convenience of explaining the embodiments of the present invention, the mirror surfaces of the fixed-focus lens of the present invention are numbered from the object side to the image side. Therefore. S1 is the object side surface of the first lens 111 close to the object side, S2 is the image side surface of the first lens 111 close to the image side; S3 is the object side surface of the second lens 112 close to the object side, S4 is the bonding surface of the second lens 112 and the third lens 113, S5 is the image side surface of the third lens 113 close to the image side; S6 is the object side surface of the fourth lens 114 close to the object side, S7 is the image side surface of the fourth lens 114 close to the image side; S8 is the aperture; S9 is the object side surface of the fifth lens 121 close to the object side, S10 is the bonding surface of the fifth lens 121 and the sixth lens 122, S11 is The image side surface of the sixth lens 122 is close to the image side; S12 is the object side surface of the seventh lens 123 close to the object side, S13 is the bonding surface of the seventh lens 123 and the eighth lens 124, and S14 is the image side surface of the eighth lens 124 close to the image side; S15 is the object side surface of the ninth lens 125 close to the object side, and S16 is the image side surface of the ninth lens 125 close to the image side; S17 is the side surface of the beam splitter 14 adjacent to the ninth lens 125, S18 is the side surface of the beam splitter 14 adjacent to the first imaging sensor A, and S19 is the side surface of the beam splitter 14 adjacent to the second imaging sensor B.

[0065] It should be noted that the combined focal length of the first lens group 11 is fI, the combined focal length of the second lens group 12 is fII, the focal length of the first lens 111 is f1, the focal length of the second lens 112 is f2, the focal length of the third lens 113 is f3, the focal length of the fourth lens 114 is f4, the combined focal length of the fifth lens 121 and the sixth lens 122 is f56, the combined focal length of the seventh lens 123 and the eighth lens 124 is f78, and the focal length of the ninth lens 125 is f9. The parameters of the fixed-focus lens of the present invention are as follows:

[0066] fI=121.159, fII=33.155;

[0067] f1=-32.638, f2=-13.455, f3=26.737, f4=35.589, f56=-81.431, f78=84.019, f9=38.904;

[0068] Lg = 27.67, Lt = 110.00;

[0069] The system parameters are: focal length 16.5mm, field of view 54.8°, and total length 110.0mm.

[0070] Table 2 below lists the relevant parameters of each lens in this embodiment, including surface type, radius of curvature, thickness, refractive index of the material, and Abbe number Vd of the lens, where Infinity represents infinity:

[0071]

[0072]

[0073] Table 2

[0074] according to Figure 3 and Figure 4 As shown, the fixed-focus lens of the present invention has a low-frequency MTF value of not less than 80% in the visible band, a mid-frequency MTF value of not less than 60%, and a high-frequency MTF value of not less than 40%; a low-frequency MTF value of not less than 70% in the infrared band, a mid-frequency MTF value of not less than 50%, and a high-frequency MTF value of not less than 40%, with high-resolution performance. It can be further known that the fixed-focus lens in this embodiment can be well corrected for various aberrations, has good temperature performance and low distortion characteristics, and therefore, the fixed-focus lens of the present invention has good optical performance.

[0075] Embodiment 2:

[0076] based on Figure 5 The structure of the fixed focus lens shown in FIG. Figure 5As shown, for the convenience of explaining the embodiments of the present invention, the mirror surfaces of the fixed-focus lens of the present invention are numbered from the object side to the image side. Therefore. S1 is the object side surface of the first lens 111 close to the object side, S2 is the image side surface of the first lens 111 close to the image side; S3 is the object side surface of the second lens 112 close to the object side, S4 is the image side surface of the second lens 112 close to the image side; S5 is the object side surface of the third lens 113 close to the object side, S6 is the image side surface of the third lens 113 close to the image side; S7 is the object side surface of the fourth lens 114 close to the object side, S8 is the image side surface of the fourth lens 114 close to the image side; S9 is the aperture; S10 is the object side surface of the fifth lens 121 close to the object side, S11 is the image side surface of the fifth lens 121 close to the image side; S12 is the sixth lens S13 is the image side surface of the sixth lens 122 close to the image side; S14 is the object side surface of the seventh lens 123 close to the object side, and S15 is the bonding surface of the seventh lens 123 and the eighth lens 124; S16 is the image side surface of the eighth lens 124 close to the image side; S17 is the object side surface of the ninth lens 125 close to the object side, and S18 is the image side surface of the ninth lens 125 close to the image side; S19 is the side surface of the beam splitter 14 adjacent to the ninth lens 125, S20 is the side surface of the beam splitter 14 adjacent to the first imaging sensor A, and S21 is the side surface of the beam splitter 14 adjacent to the second imaging sensor B.

[0077] It should be noted that the combined focal length of the first lens group 11 is fI, the combined focal length of the second lens group 12 is fII, the focal length of the first lens 111 is f1, the focal length of the second lens 112 is f2, the focal length of the third lens 113 is f3, the focal length of the fourth lens 114 is f4, the combined focal length of the fifth lens 121 and the sixth lens 122 is f56, the combined focal length of the seventh lens 123 and the eighth lens 124 is f78, and the focal length of the ninth lens 125 is f9. The parameters of the fixed-focus lens of the present invention are as follows:

[0078] fI=191.288, fII=31.353;

[0079] f1=-35.384, f2=-14.681, f3=31.116, f4=37.997, f56=-310.714, f78=857.469, f9=33.412;

[0080] Lg = 25.65, Lt = 107.50;

[0081] The system parameters are: focal length 15.6mm, field of view 50.4°, and total length 107.5mm.

[0082] Table 3 below lists the relevant parameters of each lens in this embodiment, including surface type, radius of curvature, thickness, refractive index of the material, and Abbe number Vd of the lens, where Infinity represents infinity:

[0083]

[0084]

[0085] Table 3

[0086] according to Figure 6 and Figure 7 As shown, the fixed-focus lens of the present invention has a low-frequency MTF value of not less than 80% in the visible band, a mid-frequency MTF value of not less than 60%, and a high-frequency MTF value of not less than 40%; and a high-resolution performance of not less than 70% in the infrared band, a mid-frequency MTF value of not less than 60%, and a high-frequency MTF value of not less than 40%. It can be further known that the fixed-focus lens of this embodiment can correct various aberrations well, has good temperature performance and low distortion characteristics, and therefore, the fixed-focus lens of the present invention has good optical performance.

[0087] Embodiment three:

[0088] based on Figure 8 The structure of the fixed focus lens shown in FIG. Figure 8 As shown, for the convenience of explaining the embodiments of the present invention, the mirror surfaces of the fixed-focus lens of the present invention are numbered from the object side to the image side. Therefore. S1 is the object side surface of the first lens 111 close to the object side, S2 is the image side surface of the first lens 111 close to the image side; S3 is the object side surface of the second lens 112 close to the object side, S4 is the bonding surface of the second lens 112 and the third lens 113, S5 is the image side surface of the third lens 113 close to the image side; S6 is the object side surface of the fourth lens 114 close to the object side, S7 is the image side surface of the fourth lens 114 close to the image side; S8 is the aperture; S9 is the object side surface of the fifth lens 121 close to the object side, S10 is the image side surface of the fifth lens 121 close to the image side; S11 is the object side surface of the sixth lens 122 close to the object side; S12 is The image side surface of the sixth lens 122 is close to the image side; S13 is the object side surface of the seventh lens 123 close to the object side, and S14 is the image side surface of the seventh lens 123 close to the image side; S15 is the object side surface of the eighth lens 124 close to the object side; S16 is the image side surface of the eighth lens 124 close to the image side; S17 is the object side surface of the ninth lens 125 close to the object side, and S18 is the image side surface of the ninth lens 125 close to the image side; S19 is the side surface of the beam splitter 14 adjacent to the ninth lens 125, S20 is the side surface of the beam splitter 14 adjacent to the first imaging sensor A, and S21 is the side surface of the beam splitter 14 adjacent to the second imaging sensor B.

[0089] It should be noted that the combined focal length of the first lens group 11 is fI, the combined focal length of the second lens group 12 is fII, the focal length of the first lens 111 is f1, the focal length of the second lens 112 is f2, the focal length of the third lens 113 is f3, the focal length of the fourth lens 114 is f4, the combined focal length of the fifth lens 121 and the sixth lens 122 is f56, the combined focal length of the seventh lens 123 and the eighth lens 124 is f78, and the focal length of the ninth lens 125 is f9. The parameters of the fixed-focus lens of the present invention are as follows:

[0090] fI=328.835,fII=31.138

[0091] f1=-30.538, f2=-12.440, f3=25.019, f4=34.752, f56=-134.365, f78=112.510, f9=38.401;

[0092] Lg = 25.26, Lt = 108.00;

[0093] The system parameters are: focal length 15.0mm, field of view 58.3°, and total length 108.0mm.

[0094] Table 4 below lists the relevant parameters of each lens in this embodiment, including surface type, radius of curvature, thickness, refractive index of the material, and Abbe number Vd of the lens, where Infinity represents infinity:

[0095] Face number Surface type Radius of curvature thickness Refractive Index Abbe number S1 Spherical 256.719 1.30 1.54 72.5 S2 Spherical 15.572 6.36 S3 Spherical -18.962 6.80 1.91 33.0 S4 Spherical 33.879 7.64 1.63 55.6 S5 Spherical -27.200 0.34 S6 Spherical 53.434 4.10 1.85 23.8 S7 Spherical -64.566 21.14 S8 Spherical Infinity 4.12 S9 Spherical -44.110 1.00 1.89 28.6 S10 Spherical 42.828 0.30 S11 Spherical 40.167 4.82 1.65 61.6 S12 Spherical -41.464 0.15 S13 Spherical 66.753 1.00 1.89 38.3 S14 Spherical 27.382 0.24 S15 Spherical 28.731 5.45 1.50 81.6 S16 Spherical -46.628 0.15 S17 Spherical 34.561 4.08 1.76 53.5 S18 Spherical -186.632 17.20 S19 Spherical Infinity 20.80 1.52 64.2 S20 Spherical Infinity 1.00 S21 Spherical Infinity 1.10

[0096] Table 4

[0097] according to Fig. 9 and Fig.10 As shown, the fixed-focus lens of the present invention has a low-frequency MTF value of not less than 80% in the visible band, a mid-frequency MTF value of not less than 60%, and a high-frequency MTF value of not less than 40%; and a high-resolution performance of not less than 70% in the infrared band, a mid-frequency MTF value of not less than 50%, and a high-frequency MTF value of not less than 40%. It can be further known that the fixed-focus lens of this embodiment can correct various aberrations well, has good temperature performance and low distortion characteristics, and therefore, the fixed-focus lens of the present invention has good optical performance.

[0098] Embodiment 4:

[0099] based on Fig.11 The structure of the fixed focus lens shown in FIG. Fig.11As shown, for the convenience of explaining the embodiments of the present invention, the mirror surfaces of the fixed-focus lens of the present invention are numbered from the object side to the image side. Therefore. S1 is the object side surface of the first lens 111 close to the object side, S2 is the image side surface of the first lens 111 close to the image side; S3 is the object side surface of the second lens 112 close to the object side; S4 is the image side surface of the second lens 112 close to the image side; S5 is the object side surface of the third lens 113 close to the object side; S6 is the image side surface of the third lens 113 close to the image side; S7 is the object side surface of the fourth lens 114 close to the object side, S8 is the image side surface of the fourth lens 114 close to the image side; S9 is the aperture; S10 is the object side surface of the fifth lens 121 close to the object side, S11 is the bonding surface of the fifth lens 121 and the sixth lens 122; S12 is the object side surface of the third lens 113 close to the object side; S13 is the bonding surface of the fifth lens 121 and the sixth lens 122; S14 is the bonding surface of the fifth lens 121 and the sixth lens 122; S15 is the bonding surface of the fifth lens 121 and the sixth lens 122; S16 is the bonding surface of the fifth lens 121 and the sixth lens 122; S17 is the bonding surface of the fifth lens 121 and the sixth lens 122; S18 is the bonding surface of the fifth lens 121 and the sixth lens 122. The sixth lens 122 is close to the image side; S13 is the object side surface of the seventh lens 123 close to the object side; S14 is the image side surface of the seventh lens 123 close to the image side; S15 is the object side surface of the eighth lens 124 close to the object side; S16 is the image side surface of the eighth lens 124 close to the image side; S17 is the object side surface of the ninth lens 125 close to the object side, and S18 is the image side surface of the ninth lens 125 close to the image side; S19 is the side surface of the beam splitter 14 adjacent to the ninth lens 125, S20 is the side surface of the beam splitter 14 adjacent to the first imaging sensor A, and S21 is the side surface of the beam splitter 14 adjacent to the second imaging sensor B.

[0100] It should be noted that the combined focal length of the first lens group 11 is fI, the combined focal length of the second lens group 12 is fII, the focal length of the first lens 111 is f1, the focal length of the second lens 112 is f2, the focal length of the third lens 113 is f3, the focal length of the fourth lens 114 is f4, the combined focal length of the fifth lens 121 and the sixth lens 122 is f56, the combined focal length of the seventh lens 123 and the eighth lens 124 is f78, and the focal length of the ninth lens 125 is f9. The parameters of the fixed-focus lens of the present invention are as follows:

[0101] fI=343.999, fII=32.446;

[0102] f1=-36.960, f2=-13.966, f3=32.710, f4=38.917, f56=-628.564, f78=147.230, f9=42.846;

[0103] Lg = 24.93, Lt = 109.00;

[0104] The system parameters are: focal length 14.8mm, field of view 48.0°, and total length 109.0mm.

[0105] Table 5 below lists the relevant parameters of each lens in this embodiment, including surface type, radius of curvature, thickness, refractive index of the material, and Abbe number Vd of the lens, where Infinity represents infinity:

[0106]

[0107]

[0108] Table 5

[0109] according to Fig.12 and Fig.13 As shown, the fixed-focus lens of the present invention has a low-frequency MTF value of not less than 85% in the visible band, a mid-frequency MTF value of not less than 65%, and a high-frequency MTF value of not less than 50%; and a high-resolution performance of not less than 75% in the infrared band, a mid-frequency MTF value of not less than 60%, and a high-frequency MTF value of not less than 50%. It can be further known that the fixed-focus lens of this embodiment can correct various aberrations well, has good temperature performance and low distortion characteristics, and therefore, the fixed-focus lens of the present invention has good optical performance.

[0110] Embodiment five:

[0111] based on Fig.14 The structure of the fixed focus lens shown in FIG. Fig.14 As shown, for the convenience of explaining the embodiments of the present invention, the mirror surfaces of the lens of the fixed-focus lens of the present invention are numbered from the object side to the image side. Therefore. S1 is the object side surface of the first lens 111 close to the object side, S2 is the image side surface of the first lens 111 close to the image side; S3 is the object side surface of the second lens 112 close to the object side; S4 is the image side surface of the second lens 112 close to the image side; S5 is the object side surface of the third lens 113 close to the object side; S6 is the image side surface of the third lens 113 close to the image side; S7 is the object side surface of the fourth lens 114 close to the object side, S8 is the image side surface of the fourth lens 114 close to the image side; S9 is the aperture; S10 is the object side surface of the fifth lens 121 close to the object side; S11 is the image side surface of the fifth lens 121 close to the image side; S12 is the object side surface of the sixth lens 122 close to the object side. side; S13 is the image side surface of the sixth lens 122 close to the image side; S14 is the object side surface of the seventh lens 123 close to the object side; S15 is the image side surface of the seventh lens 123 close to the image side; S16 is the object side surface of the eighth lens 124 close to the object side; S17 is the image side surface of the eighth lens 124 close to the image side; S18 is the object side surface of the ninth lens 125 close to the object side, and S19 is the image side surface of the ninth lens 125 close to the image side; S20 is the side surface of the beam splitter 14 adjacent to the ninth lens 125, S21 is the side surface of the beam splitter 14 adjacent to the first imaging sensor A, and S22 is the side surface of the beam splitter 14 adjacent to the second imaging sensor B.

[0112] It should be noted that the combined focal length of the first lens group 11 is fI, the combined focal length of the second lens group 12 is fII, the focal length of the first lens 111 is f1, the focal length of the second lens 112 is f2, the focal length of the third lens 113 is f3, the focal length of the fourth lens 114 is f4, the combined focal length of the fifth lens 121 and the sixth lens 122 is f56, the combined focal length of the seventh lens 123 and the eighth lens 124 is f78, and the focal length of the ninth lens 125 is f9. The parameters of the fixed-focus lens of the present invention are as follows:

[0113] fI=240.189, fII=30.933;

[0114] f1=-38.385, f2=-13.375, f3=31.684, f4=37.826, f56=-244.283, f78=342.569, f9=34.007;

[0115] Lg = 22.61, Lt = 108.00;

[0116] The system parameters are: focal length 14.0mm, field of view 51.0°, and total length 108.0mm.

[0117] Table 6 below lists the relevant parameters of each lens in this embodiment, including surface type, radius of curvature, thickness, refractive index of the material, and Abbe number Vd of the lens, where Infinity represents infinity:

[0118]

[0119]

[0120] Table 6

[0121] according to Fig.12 and Fig.13 As shown, the fixed-focus lens of the present invention has a low-frequency MTF value of not less than 85% in the visible band, a mid-frequency MTF value of not less than 60%, and a high-frequency MTF value of not less than 45%; and a high-resolution performance of not less than 70% in the infrared band, a mid-frequency MTF value of not less than 60%, and a high-frequency MTF value of not less than 45%. It can be further known that the fixed-focus lens of this embodiment can correct various aberrations well, has good temperature performance and low distortion characteristics, and therefore, the fixed-focus lens of the present invention has good optical performance.

[0122] The above contents are merely examples of specific solutions of the present invention. For devices and structures not described in detail therein, it should be understood that they can be implemented by adopting general devices and general methods available in the art.

[0123] The above is only one solution of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fixed-focus lens, characterized in that: It comprises a first lens group (11) and a second lens group (12) which are arranged in sequence from the object side to the image side, a total of two lens groups; Along the direction from the object side to the image side, the first lens group (11) consists of a first lens (111) with negative optical power, a second lens (112) with negative optical power, a third lens (113) with positive optical power, and a fourth lens (114) with positive optical power; Along the direction from the object side to the image side, the second lens group (12) consists of a fifth lens (121) with negative optical power, a sixth lens (122) with positive optical power, a seventh lens (123) with negative optical power, an eighth lens (124) with positive optical power, and a ninth lens (125) with positive optical power; The third lens (113) is a biconvex lens; and / or, The fifth lens (121) is a biconcave lens; and / or, The seventh lens (123) is a convex-concave lens; The focal length of the first lens group (11) is fI, and the focal length of the second lens group (12) is fII, then the following condition is satisfied: 6.10≤fI / fII<11.

2. The fixed-focus lens according to claim 1, characterized in that: Also includes: Optical Splitter (14): Along the direction from the object side to the image side, the first lens group (11), the second lens group (12) and the beam splitter (14) are arranged in sequence; The beam splitter (14) is a prism beam splitter.

3. The fixed-focus lens according to claim 2, characterized in that: The spacing distance between the first lens group (11) and the second lens group (12) is Lg, and the total length of the fixed-focus lens is Lt, then the following condition is satisfied: 4.19≤Lt / Lg<5.

4. The fixed-focus lens according to claim 3, characterized in that: The curvature radius of the object side surface of the second lens (112) is R2a, and the curvature radius of the image side surface of the first lens (111) is R1b, and the following condition is satisfied: -2<R2a / R1b<-1.

5. The fixed-focus lens according to claim 4, characterized in that: The focal length of the first lens group (11) is fI, and the focal length of the fourth lens (114) is f4, then the following condition is satisfied: 5.03≤fI / f4<10.

6. The fixed-focus lens according to claim 4, characterized in that: The focal length of the second lens group (12) is fII, and the focal length of the ninth lens (125) is f9, then the following relationship is satisfied: 1<f9 / fII<1.

5.

7. The fixed-focus lens according to any one of claims 1 to 6, characterized in that: The refractive index of the material of the fifth lens (121) for the spectral d-line is Nd5, and the refractive index of the material of the sixth lens (122) for the spectral d-line is Nd6, which satisfies: 1.1<(Nd5-1) / (Nd6-1)≤1.

51.

8. The fixed-focus lens according to claim 7, characterized in that: The refractive index of the material of the seventh lens (123) for the d-line of the spectrum is Nd7, and the refractive index of the material of the eighth lens (124) for the d-line of the spectrum is Nd8, and 1.32≤(Nd7-1) / (Nd8-1)<1.9 is satisfied.

9. The fixed-focus lens according to claim 1, wherein: Also includes: Aperture (13): along the direction from the object side to the image side, the first lens group (11), the aperture (13), and the second lens group (12) are arranged in sequence.

Images