Prime lens and monitoring equipment

Abstract

The utility model discloses a prime lens and monitoring equipment. The prime lens comprises a convex-concave first lens with positive focal power, a field diaphragm, a second lens with negative focal power, a third lens with positive focal power, a convex-convex fourth lens with positive focal power, a concave-concave fifth lens with negative focal power and a sixth lens with positive focal power which are sequentially arranged from an object space to an image space along an optical axis, the vignetting diaphragm comprises a convex seventh lens with positive focal power and a concave eighth lens with negative focal power; the image side surface of the second lens is a concave surface, the object side surface of the third lens is a convex surface, the image side surface of the sixth lens is a convex surface, the second lens and the third lens are cemented into a first cemented lens, and the fourth lens and the fifth lens are cemented into a second cemented lens. And high resolution performance is achieved in visible light and near-infrared bands.

Description

Technical Field

[0001] This utility model relates to the field of optical technology, and in particular to a fixed-focus lens and a monitoring device. Background Technology

[0002] With the development of technology, surveillance cameras face increasingly harsh working environments. Increasing the focal length of a lens typically leads to a larger aperture, increasing its weight and the cost of manufacturing materials. To control the aperture, a common solution is to reduce the aperture, which sacrifices the lens's ability to operate in low-light conditions and reduces its resolution. Utility Model Content

[0003] This invention provides a fixed-focus lens and a monitoring device that can achieve infrared confocal focusing in the near-infrared band (830-940nm) while having high resolution performance in both visible and near-infrared bands. Furthermore, the lens has a relative illumination greater than 50%, low cost, large aperture, long focal length, and low distortion.

[0004] To achieve the above objectives, this utility model provides a fixed-focus lens, comprising: a first convex-concave lens with positive optical power, a field stop, a second lens with negative optical power, a third lens with positive optical power, a fourth convex-convex lens with positive optical power, a fifth concave-concave lens with negative optical power, a sixth lens with positive optical power, a vignetting stop, a seventh convex-convex lens with positive optical power, and an eighth concave-concave lens with negative optical power, arranged sequentially from the object side to the image side along the optical axis;

[0005] The second lens has a concave image side, the third lens has a convex object side, and the sixth lens has a convex image side. The second lens and the third lens are cemented together to form a first cemented lens, and the fourth lens and the fifth lens are cemented together to form a second cemented lens.

[0006] Optionally, the object-side surface of the second lens is concave or convex, and the image-side surface of the third lens is concave or convex.

[0007] Optionally, the optical power of the first lens Optical power of the fixed-focus lens The following relationship is satisfied between them:

[0008] The refractive index ND1 of the first lens satisfies the following relationship: 1.8 <ND1<2.1。

[0009] Optionally, the optical power of the second lens The optical power of the third lens Optical power of the first cemented lens satisfy the relational expression:

[0010] the optical power of the second lens the optical power of the third lens the Abbe number vd2 of the second lens and the Abbe number vd3 of the third lens satisfy the relational expression:

[0011]

[0012] Optionally, the optical power of the fourth lens the optical power of the fifth lens and the optical power of the second cemented lens satisfy the relational expression:

[0013] the optical power of the fourth lens the optical power of the fifth lens the Abbe number vd4 of the fourth lens and the Abbe number vd5 of the fifth lens satisfy the relational expression:

[0014]

[0015] Optionally, the Abbe number vd3 of the third lens satisfies the relational expression: 60 < vd3 < 96; the Abbe number vd4 of the fourth lens satisfies the relational expression: 60 < vd4 < 96. <00​​​​​​​​​​​​​​​​​​​​​​​​According to the embodiments of the present invention, the fixed-focus lens and monitoring device include: a first convex-concave lens with positive optical power, a field stop, a second lens with negative optical power, a third lens with positive optical power, a fourth convex-convex lens with positive optical power, a fifth concave-concave lens with negative optical power, a sixth lens with positive optical power, a vignetting stop, a seventh convex-convex lens with positive optical power, and an eighth concave-concave lens with negative optical power; the image-side surface of the second lens is concave, the object-side surface of the third lens is convex, the image-side surface of the sixth lens is convex, the second lens and the third lens are cemented together to form a first cemented lens, the fourth lens and the fifth lens are cemented together to form a second cemented lens, and the first to eighth lenses are all glass spherical lenses. By rationally setting the optical power and surface shape of the eight lenses and combining them with glass materials, a lens with a focal length of around 40mm, optical distortion of less than 1.5%, image square F#=2.0, and a maximum image height of 9.12mm was achieved at a relatively low cost. Furthermore, infrared confocal technology was achieved in the near-infrared band of 830nm to 940nm, while also exhibiting high resolution performance in both the visible and near-infrared bands.

[0022] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the fixed-focus lens provided in Embodiment 1 of this utility model;

[0025] Figure 2 This is a schematic diagram of the MTF (Multi-Frequency Transcript) of the fixed-focus lens in the mixed-light band provided in Embodiment 1 of this utility model;

[0026] Figure 3 This is a schematic diagram of the full-frequency MTF of the fixed-focus lens in the infrared 850nm band provided in Embodiment 1 of this utility model;

[0027] Figure 4 This is a schematic diagram of the center field of view defocused MTF after the superposition of mixed light and 850nm light of the fixed-focus lens provided in Embodiment 1 of this utility model;

[0028] Figure 5This is a schematic diagram of field curvature and distortion of a fixed-focus lens provided in Embodiment 1 of this utility model;

[0029] Figure 6 This is a schematic diagram of the fixed-focus lens provided in Embodiment 2 of this utility model;

[0030] Figure 7 This is a schematic diagram of the MTF (Multi-Frequency Transcript) of the fixed-focus lens in the mixed-light band provided in Embodiment 2 of this utility model;

[0031] Figure 8 This is a schematic diagram of the full-frequency MTF of the fixed-focus lens in the infrared 850nm band provided in Embodiment 2 of this utility model;

[0032] Figure 9 This is a schematic diagram of the center field of view defocused MTF after the superposition of mixed light and 850nm light of the fixed-focus lens provided in Embodiment 2 of this utility model;

[0033] Figure 10 This is a schematic diagram of field curvature and distortion of a fixed-focus lens provided in Embodiment 2 of this utility model;

[0034] Figure 11 This is a schematic diagram of the fixed-focus lens provided in Embodiment 3 of this utility model;

[0035] Figure 12 This is a schematic diagram of the MTF (Multi-Frequency Transcript) of the fixed-focus lens in the mixed-light band provided in Embodiment 3 of this utility model;

[0036] Figure 13 This is a schematic diagram of the full-frequency MTF of the fixed-focus lens in the infrared 850nm band provided in Embodiment 3 of this utility model;

[0037] Figure 14 This is a schematic diagram of the center field of view defocused MTF after the superposition of mixed light and 850nm light of the fixed-focus lens provided in Embodiment 3 of this utility model;

[0038] Figure 15 This is a schematic diagram of field curvature and distortion of a fixed-focus lens provided in Embodiment 3 of this utility model. Detailed Implementation

[0039] 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. 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 protection scope of the present invention.

[0040] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model 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 this utility model 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 non-exclusive inclusion.

[0041] Figure 1 This is a schematic diagram of the fixed-focus lens provided in Embodiment 1 of this utility model. Figure 6 This is a schematic diagram of the fixed-focus lens provided in Embodiment 2 of this utility model. Figure 11 This is a schematic diagram of the fixed-focus lens provided in Embodiment 3 of this utility model, as shown below. Figures 1 to 11 As shown, the fixed-focus lens includes: a first convex-concave lens L1 with positive optical power, a field stop, a second lens L2 with negative optical power, a third lens L3 with positive optical power, a fourth convex-convex lens L4 with positive optical power, a fifth concave-concave lens L5 with negative optical power, a sixth lens L6 with positive optical power, a vignetting stop, a seventh convex-convex lens L7 with positive optical power, and an eighth concave-concave lens L8 with negative optical power; wherein, the image-side surface of the second lens L2 is concave, the object-side surface of the third lens L3 is convex, the image-side surface of the sixth lens L6 is convex, the second lens L2 and the third lens L3 are cemented together to form a first cemented lens, the fourth lens L4 and the fifth lens L5 are cemented together to form a second cemented lens, and the first lens L1 to the eighth lens L8 are all glass spherical lenses.

[0042] Specifically, 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 the bending ability of light; the smaller the absolute value, the weaker the bending ability. 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 formed by multiple lenses (i.e., a lens group). In the fixed-focus lens provided in this embodiment, all lenses can be fixed within a single lens barrel (…). Figure 1 (Not shown in the text)

[0043] In this paper, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of this 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 this 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 object side is called the object-side surface of the lens, and the surface of each lens closest to the image side is called the image-side surface of the lens. The surface shape in the paraxial region can be determined according to the judgment method commonly used by those knowledgeable in the field, using the R value (R refers to the radius of curvature of the paraxial region, usually the R value in the lens database of optical software) to determine concavity and convexity. When the R value is positive, the lens surface is convex towards the object side; when the R value is negative, the lens surface is convex towards the image side.

[0044] For example, if the first lens L1 is a convex-concave lens, then both the object-side and image-side surfaces of the first lens L1 are convex towards the object. If the image-side surface of the second lens L2 is concave, then the image-side surface of the second lens L2 is convex towards the object. If the object-side surface of the third lens L3 is convex, then the object-side surface of the third lens L3 is convex towards the object. If the fourth lens L4 is a convex-convex lens, then the object-side surface of the fourth lens L4 is convex towards the object, and the image-side surface is convex towards the image. If the fifth lens L5 is a concave-concave lens, then both the object-side and image-side surfaces of the fifth lens L5 are convex towards the image. If the sixth lens L6 has a convex image-side surface, then the image-side surface of the sixth lens L6 is convex towards the image. If the seventh lens L7 is a convex-convex lens, then both the object-side and image-side surfaces of the seventh lens L7 are convex towards the object. If the eighth lens L8 is a concave-concave lens, then both the object-side and image-side surfaces of the eighth lens L8 are convex towards the image.

[0045] The first lens L1 has a positive optical power, which facilitates light convergence and prevents excessive divergence of light on the object side. This also helps control the aperture of the rear lens and enables miniaturization. The first lens L1 is preferably made of a high-refractive-index material, which allows for a smaller front aperture. Its convex object side helps converge large-aperture light into the rear optical system, increasing light transmission. The second lens L2 has a negative optical power and a concave image side. Its object side can be either concave or convex. The negative optical power facilitates light diffusion, and the convex object side ensures that light rays exiting the first lens L1 are almost perpendicularly incident on the object side of the second lens L2. This results in a smoother light transition, reducing light loss, improving peripheral field illumination, and lowering lens sensitivity. The third lens L3 has a positive optical power and a convex object side, which matches the concave image side of the second lens L2. This allows for a smoother transition of light rays entering from the second lens L2, reducing light loss, improving resolution, and stabilizing the light path with the rear lens. The fourth lens, L4, has a positive optical power, which helps to converge the light rays emitted from the preceding lens, allowing for a smooth transition to the rear lens. The fifth lens, L5, has a negative optical power and diverges the light rays. By controlling the focal length of the fifth lens, L5 can effectively correct various aberrations caused by the preceding positive and negative lenses. The sixth lens, L6, has a positive optical power, which helps to converge the light rays. On the one hand, it allows diverging light rays to smoothly enter the rear optical system; on the other hand, it lowers the position of the light rays entering the subsequent optical system, reducing the rear aperture. Furthermore, with the same object-side aperture of the sixth lens, L6, the front aperture of the lens can be reduced, achieving the goal of lens miniaturization. The seventh lens, L7, has a positive optical power, ensuring a smooth lens shape. It further converges the light rays emitted from the sixth lens, L6, and allows them to smoothly enter the rear lens, which helps to reduce sensitivity and improve resolving power. The eighth lens, L8, has a negative optical power, causing the light rays to diverge upwards after passing through the image-side surface of the eighth lens. This allows the light rays to accumulate rapidly at the image plane, which helps to expand the imaging range.

[0046] Furthermore, by using a second lens L2 and a third lens L3 to form a first cemented lens, and a fourth lens L4 and a fifth lens L5 to form a second cemented lens, the air gap between the second lens L2 and the third lens L3, and the air gap between the fourth lens L4 and the fifth lens L5, can be effectively reduced, thus helping to reduce the overall length of the lens. In addition, cemented lenses can minimize or eliminate chromatic aberration, allowing various aberrations in a fixed-focus lens to be fully corrected. With a compact structure, this improves resolution, optimizes optical performance such as distortion, and reduces light loss caused by reflections between lens elements, increasing illumination and thus improving image quality and the sharpness of the lens image. Moreover, the use of cemented lenses reduces the number of assembly components between the two lens elements, simplifying the assembly process in lens manufacturing, reducing costs, and reducing tolerance sensitivity issues such as tilting / eccentricity of lens units during assembly.

[0047] The field stop is located between the first lens L1 and the second lens L2. The aperture of the field stop determines the aperture size, which helps to effectively gather the light entering the lens, reduce the lens aperture at the front of the lens, and reduce the sensitivity of the system. The vignetting stop is located between the sixth lens L6 and the seventh lens L7, and is used to block light and improve the performance of the outer field of view.

[0048] Therefore, this embodiment of the utility model uses eight lenses. By reasonably setting the optical power of each lens, it is beneficial to realize a fixed-focus lens with a large target area, a large aperture, and a long focal length. The fixed-focus lens provided in this embodiment has a focal length of about 40mm, |optical distortion| < 1.5%, image square F# = 2.0, and a maximum image height of 9.12mm. Furthermore, it achieves infrared confocalization in the near-infrared band of 830nm to 940nm, while also having high resolution performance in the visible light and near-infrared bands.

[0049] Optionally, the object-side surface of the second lens L2 is concave or convex, and the image-side surface of the third lens L3 is concave or convex. When the object-side surface of the second lens L2 is concave, it can collect light rays after passing through the field stop and then diverge them before transmitting them to the third lens L3. When the object-side surface of the second lens L2 is convex, it can collect light rays after passing through the field stop and then converge them before transmitting them to the third lens L3. When the image-side surface of the third lens L3 is concave, it can diffuse light rays. When the image-side surface of the third lens L3 is convex, it can converge light rays.

[0050] Optionally, the optical power of the first lens L1 Optical focal length of a prime lens The following relationship is satisfied between them:

[0051] The refractive index ND1 of the first lens L1 satisfies the relation: 1.8 < ND1 < 2.1. Meeting this condition is beneficial to reducing the incident angle of light entering the optical system, shrinking the aperture of the optical system, thereby reducing the volume and weight of the optical system.

[0052] Optionally, the optical power of the second lens L2 The optical power of the third lens L3 And the optical power of the first cemented lens Satisfy the relation:

[0053] The optical power of the second lens L2 The optical power of the third lens L3 The Abbe number vd2 of the second lens L2 and the Abbe number vd3 of the third lens L3 satisfy the relation: Meeting this condition is beneficial for the doublet lens to exert its ability to correct chromatic aberration of the optical system, thereby improving the resolution of the optical system.

[0054] Optionally, the optical power of the fourth lens L4 The optical power of the fifth lens L5 And the optical power of the second cemented lens Satisfy the relation:

[0055] The optical power of the fourth lens L4 The optical power of the fifth lens L5 The Abbe number vd4 of the fourth lens L4 and the Abbe number vd5 of the fifth lens L5 satisfy the relation: Meeting this condition is beneficial for the doublet lens to exert its ability to correct chromatic aberration of the optical system, thereby improving the resolution of the optical system.

[0056] Optionally, the Abbe number vd3 of the third lens L3 satisfies the relation: 60 < vd3 < 96; the Abbe number vd4 of the fourth lens L4 satisfies the relation: 60 < vd4 < 96. Meeting this condition is beneficial for the correction of axial chromatic aberration of the system to achieve infrared confocal.

[0057] Optionally, the optical power of the sixth lens L6 The optical power of the seventh lens L7 The optical power of the eighth lens L8 The optical power of the fixed-focus lens <00001​​​​Optionally, the semi-aperture SDmax of the first lens L1 and the maximum image height H of the fixed-focus lens satisfy the relationship: 1 < SDmax / H < 1.2. This is beneficial for reducing the volume and weight of the overall optical system, adapting to more usage environments, and reducing the material cost of the lenses.

[0059] Optionally, the distance TTL from the center of the object side of the first lens L1 to the center of the imaging surface and the focal length f of the fixed-focus lens satisfy the relationship: 1.1 < TTL / f < 1.3. This is beneficial for reducing the volume and weight of the overall optical system, adapting to more usage environments, and reducing the material cost of the lenses.

[0060] The following uses specific embodiments to introduce the fixed-focus lens proposed in the embodiments of the present invention.

[0061] Table 1 Parameter table of each relationship in Embodiments 1 to 3

[0062]

[0063]

[0064] Embodiment 1

[0065] Figure 1 is a schematic structural diagram of the fixed-focus lens provided in Embodiment 1 of the present invention. As Figure 1 shown, the fixed-focus lens includes: a convex-concave first lens L1 with positive optical power, a field stop STO, a concave-concave second lens L2 with negative optical power, a convex-convex third lens L3 with positive optical power, a convex-convex fourth lens L4 with positive optical power, a concave-concave fifth lens L5 with negative optical power, a convex-convex sixth lens L6 with positive optical power, a vignetting stop 10, a convex-convex seventh lens L7 with positive optical power, and a concave-concave eighth lens L8 with negative optical power; and a filter 20 and an image plane 30. The second lens L2 and the third lens L3 are cemented into a first cemented lens, the fourth lens L4 and the fifth lens L5 are cemented into a second cemented lens, and the first lens L1 to the eighth lens L8 are all glass spherical lenses. Among them, the maximum image height H in the fixed-focus lens of Embodiment 1 is 9.12 mm, the image-side F# is 2, the TTL is 48.6 mm, and the lens focal length f is 42 mm. The parameters of each lens in the fixed-focus lens of Embodiment 1 are shown in Table 2.

[0066] Table 2 Parameters of each lens in the fixed-focus lens of Embodiment 1

[0067]

[0068]

[0069] The surface numbers S1 to S19 in Table 2 are assigned according to the surface sequence of each lens. "S1" represents the front surface of the first lens, "S2" represents the rear surface of the first lens, and so on. "STO" represents the aperture stop of the lens. The radius of curvature represents the degree of curvature of the lens surface. A positive value means that the surface bends towards the image plane, and a negative value means that the surface bends towards the object plane. 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 represents the current position as air, with a refractive index of 1.

[0070] In this embodiment, the optical power of the first cemented lens The optical power of the second cemented lens is -0.0268. It is -0.0163.

[0071] Figure 2 This is a schematic diagram of the MTF (Mean Transmission Frequency) of the fixed-focus lens across the mixed optical bands provided in Embodiment 1 of this utility model. Figure 2 As shown, this hybrid optical band includes the 436nm to 940nm band. The horizontal axis represents the number of line pairs, and the vertical axis represents the modulation value. The center field of view reaches 50% at 150 lp / mm, and the edge field of view reaches 37% at 150 lp / mm.

[0072] Figure 3 This is a schematic diagram of the full-frequency MTF of the fixed-focus lens in the infrared 850nm band provided in Embodiment 1 of this utility model. The horizontal axis represents the number of line pairs, and the vertical axis represents the modulation value. The center field of view reaches 45% at 150 lp / mm, and the edge field of view reaches 40% at 150 lp / mm.

[0073] Figure 4 This is a schematic diagram of the center field-of-view defocus MTF of the fixed-focus lens provided in Embodiment 1 of this utility model, after the superposition of the mixed light and 850nm light. The horizontal axis represents the defocus amount, and the vertical axis represents the modulation value. The two lines in the diagram, blue for the mixed light center field-of-view defocus MTF and green for the 850nm band center field-of-view defocus MTF, show the difference between the peak values ​​of these two curves on the horizontal axis, reflecting the infrared confocal capability; the smaller the difference, the smaller the defocus amount at the infrared 850nm band. Figure 4 The difference between the two can be seen to be between -3μm and 3μm. Figures 2 to 4 This indicates that the fixed-focus lens has good resolution in both the mixed light band and the infrared band.

[0074] Figure 5 This is a schematic diagram of field curvature and distortion of a fixed-focus lens provided in Embodiment 1 of this utility model. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, in μm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 5As can be seen, the fixed-focus lens provided in this embodiment effectively controls the field curvature of light with a wavelength of 546nm, meaning that during imaging, the difference in image quality between the center and the periphery is relatively small (wherein, in the field curvature diagram on the left, the maximum field of view is 6.111 degrees, the sagittal field curvature is 0.0180mm, and the meridional field curvature is 0.0223mm). In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, in %; the vertical axis represents the normalized image height, which has no unit; from Figure 5 It can be seen that the lens provided in this embodiment has distortion (in the distortion diagram on the right, the maximum distortion = 1.48%).

[0075] Example 2

[0076] Figure 6 This is a schematic diagram of the fixed-focus lens provided in Embodiment 2 of this utility model, as shown below. Figure 6 As shown, the fixed-focus lens includes: a first convex-concave lens L1 with positive optical power, a field stop STO, a second convex-concave lens L2 with negative optical power, a third convex-concave lens L3 with positive optical power, a fourth convex-convex lens L4 with positive optical power, a fifth concave-concave lens L5 with negative optical power, a sixth concave-convex lens L6 with positive optical power, a vignetting stop 10, a seventh convex-convex lens L7 with positive optical power, and an eighth concave-concave lens L8 with negative optical power; a filter 20 and an image plane 30. The second lens L2 and the third lens L3 are cemented together to form a first cemented lens, and the fourth lens L4 and the fifth lens L5 are cemented together to form a second cemented lens. The first lens L1 to the eighth lens L8 are all glass spherical lenses. In the fixed-focus lens of Example 2, the maximum image height H is 9.12mm, the image square F# is 2, the TTL is 48.98mm, and the lens focal length f is 38mm.

[0077] The parameters of each lens in the fixed-focus lens of Example 2 are shown in Table 3.

[0078] Table 3. Parameters of each lens in the fixed-focus lens of Example 2

[0079] Face number Surface type radius of curvature thickness Refractive index Abbe number Dispersion dPgF Half-caliber 0 surface Infinity Infinity S1 Standard surface 23.1514 2.468 1.9200 23.30 0.000 9.580 S2 Standard surface 50.0334 7.082 9.376 STO Standard surface Infinity 0.579 7.771 S4 Standard surface 33.0445 1.182 1.6500 33.90 0.000 7.455 S5 Standard surface 7.2619 4.400 1.5900 68.60 0.019 6.484 S6 Standard surface 29.3885 0.368 6.285 S7 Standard surface 15.4406 3.084 1.5900 76.46 0.0199 6.130 S8 Standard surface -21.6487 4.944 1.8500 23.80 0.000 5.871 S9 Standard surface 15.2194 1.263 4.699 S10 Standard surface -26.3435 4.601 1.8700 20.10 0.000 4.692 S11 Standard surface -21.1069 0.099 5.036 S12 Standard surface Infinity 0.099 4.950 S13 Standard surface 20.7357 4.960 1.8500 24.50 0.000 5.098 S14 Standard surface -18.0705 1.745 4.904 S15 Standard surface -13.9430 0.997 1.910 35.30 0.000 4.189 S16 Standard surface 41.6622 0.308 4.138 S17 Standard surface Infinity 1.5000 1.520 64.20 0.000 4.142 S18 Standard surface Infinity 9.3000 4.182 S19 Image Infinity -

[0080] The surface numbers S1 to S19 in Table 3 are assigned according to the surface sequence of each lens. "S1" represents the front surface of the first lens, "S2" represents the rear surface of the first lens, and so on. "STO" represents the aperture stop of the lens. The radius of curvature represents the degree of curvature of the lens surface. A positive value means that the surface bends towards the image plane, and a negative value means that the surface bends towards the object plane. 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 represents the current position as air, with a refractive index of 1.

[0081] In this embodiment, the optical power of the first cemented lens The optical power of the second cemented lens is -0.0791. It is -0.0212.

[0082] Figure 7 This is a schematic diagram of the MTF (Mean Transmission Format) of the fixed-focus lens across the entire frequency band, according to Embodiment 2 of this utility model. Figure 7 As shown, this hybrid optical band includes the 436nm to 940nm band. The horizontal axis represents the number of line pairs, and the vertical axis represents the modulation value. The center field of view reaches 50% at 150 lp / mm, and the edge field of view reaches 42% at 150 lp / mm.

[0083] Figure 8 This is a schematic diagram of the full-frequency MTF of the fixed-focus lens in the infrared 850nm band provided in Embodiment 2 of this utility model. The horizontal axis represents the number of line pairs, and the vertical axis represents the modulation value. The center field of view reaches 50% at 150 lp / mm, and the edge field of view reaches 46% at 150 lp / mm.

[0084] Figure 9 This is a schematic diagram of the center field-of-view defocus MTF of the fixed-focus lens provided in Embodiment 2 of this utility model after superimposing the mixed light and 850nm light. The horizontal axis represents the defocus amount, and the vertical axis represents the modulation value. The two lines in the diagram, blue for the mixed light center field-of-view defocus MTF and green for the 850nm band center field-of-view defocus MTF, show the difference between the peak values ​​of these two curves on the horizontal axis, reflecting the infrared confocal capability; the smaller the difference, the smaller the defocus amount at the infrared 850nm band. Figure 9 The difference between the two can be seen to be between -3μm and 3μm. Figures 7 to 9 This indicates that the fixed-focus lens has good resolution in both the mixed light band and the infrared band.

[0085] Figure 10 This is a schematic diagram of field curvature and distortion of a fixed-focus lens provided in Embodiment 2 of this utility model. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, in μm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 10 As can be seen, the fixed-focus lens provided in this embodiment effectively controls the field curvature of light with a wavelength of 546nm, meaning that during imaging, the difference in image quality between the center and the periphery is relatively small (wherein, in the field curvature diagram on the left, the maximum field of view is 6.776 degrees, the sagittal field curvature = 0.0259mm, and the meridional field curvature = 0.0227mm). In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, in %; the vertical axis represents the normalized image height, which has no unit; from Figure 10 As can be seen, the lens provided in this embodiment has distortion (in the distortion diagram on the right, the maximum distortion = 1.0%).

[0086] Example 3

[0087] Figure 11 This is a schematic diagram of the fixed-focus lens provided in Embodiment 3 of this utility model, as shown below. Figure 11 As shown, the fixed-focus lens includes: a first convex-concave lens L1 with positive optical power, a field stop STO, a second convex-concave lens L2 with negative optical power, a third convex-concave lens L3 with positive optical power, a fourth convex-convex lens L4 with positive optical power, a fifth concave-concave lens L5 with negative optical power, a sixth convex-convex lens L6 with positive optical power, a vignetting stop 10, a seventh convex-convex lens L7 with positive optical power, and an eighth concave-concave lens L8 with negative optical power; a filter 20 and an image plane 30. The second lens L2 and the third lens L3 are cemented together to form a first cemented lens, and the fourth lens L4 and the fifth lens L5 are cemented together to form a second cemented lens. The first lens L1 to the eighth lens L8 are all glass spherical lenses. In the fixed-focus lens of Example 3, the maximum image height H is 9.12mm, the image square F# is 2, the TTL is 49.80mm, and the lens focal length f is 40mm.

[0088] The parameters of each lens in the fixed-focus lens of Example 3 are shown in Table 4.

[0089] Table 4. Parameters of each lens in the fixed-focus lens of Example 3

[0090] Face number Surface type radius of curvature thickness Refractive index Abbe number Dispersion dPgF Half-caliber 0 surface Infinity Infinity S1 Standard surface 22.9410 2.755 1.9200 20.70 0.000 10.100 S2 Standard surface 66.5869 6.310 9.940 STO Standard surface Infinity -0.003 8.034 S4 Standard surface 100.0000 0.999 1.6900 29.40 0.000 7.945 S5 Standard surface 11.2762 3.332 1.5000 81.60 0.0375 7.278 S6 Standard surface 89.6774 0.098 7.152 S7 Standard surface 15.1893 3.497 1.5000 74.30 0.009 6.920 S8 Standard surface -26.2111 4.948 1.9200 18.90 0.000 6.659 S9 Standard surface 16.0480 5.852 5.636 S10 Standard surface 62.2544 2.000 1.9200 19.70 0.000 6.034 S11 Standard surface -25.0596 1.289 6.029 S12 Standard surface Infinity 0.289 5.398 S13 Standard surface 13.3458 4.993 1.6400 36.10 0.000 5.412 S14 Standard surface -27.5446 0.807 4.694 S15 Standard surface -24.5078 1.030 1.910 35.30 0.000 4.250 S16 Standard surface 11.2631 0.803 3.937 S17 Standard surface Infinity 1.5000 1.520 64.20 0.000 3.943 S18 Standard surface Infinity 9.3000 4.001 S19 Image Infinity -

[0091] The surface numbers S1 to S19 in Table 4 are assigned according to the surface sequence of each lens. "S1" represents the front surface of the first lens, "S2" represents the rear surface of the first lens, and so on. "STO" represents the aperture stop of the lens. The radius of curvature (mm) represents the curvature of the lens surface. A positive value means that the surface bends towards the image plane, and a negative value means that the surface bends towards the object plane. The thickness (mm) 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 represents the current position as air, with a refractive index of 1.

[0092] In this embodiment, the optical power of the first cemented lens The optical power of the second cemented lens is -0.0159. It is -0.033.

[0093] Figure 12 This is a schematic diagram of the MTF (Mean Transmission Format) of the fixed-focus lens across the entire frequency band, according to Embodiment 3 of this utility model. Figure 12As shown, this hybrid optical band includes the 436nm to 940nm band. The horizontal axis represents the number of line pairs, and the vertical axis represents the modulation value. The center field of view reaches 50% at 150 lp / mm, and the edge field of view also reaches 50% at 150 lp / mm.

[0094] Figure 13 This is a schematic diagram of the full-frequency MTF of the fixed-focus lens in the infrared 850nm band provided in Embodiment 3 of this utility model. The horizontal axis represents the number of line pairs, and the vertical axis represents the modulation value. The center field of view reaches 50% at 150 lp / mm, and the edge field of view also reaches 50% at 150 lp / mm.

[0095] Figure 14 This is a schematic diagram of the center field-of-view defocus MTF of the fixed-focus lens provided in Embodiment 3 of this utility model after superimposing the mixed light and 850nm light. The horizontal axis represents the defocus amount, and the vertical axis represents the modulation value. The two lines in the diagram, blue for the mixed light center field-of-view defocus MTF and green for the 850nm band center field-of-view defocus MTF, show the difference between the peak values ​​of these two curves on the horizontal axis, reflecting the infrared confocal capability; the smaller the difference, the smaller the defocus amount at the infrared 850nm band. Figure 14 The difference between the two can be seen to be between -3μm and 3μm. Figures 12 to 14 This indicates that the fixed-focus lens has good resolution in both the mixed light band and the infrared band.

[0096] Figure 15 This is a schematic diagram of field curvature and distortion of a fixed-focus lens provided in Embodiment 3 of this utility model. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, with the unit being μm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 15 As can be seen, the fixed-focus lens provided in this embodiment effectively controls the field curvature of light with a wavelength of 546nm, meaning that during imaging, the difference in image quality between the center and the periphery is relatively small (wherein, in the field curvature diagram on the left, the maximum field of view is 6.404 degrees, the sagittal field curvature = 0.0064mm, and the meridional field curvature = 0.0045mm). In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, in %; the vertical axis represents the normalized image height, which has no unit; from Figure 15 As can be seen, the lens provided in this embodiment has distortion (in the distortion diagram on the right, the maximum distortion = 1.49%).

[0097] This utility model embodiment also proposes a monitoring device, including a fixed-focus lens proposed in any embodiment of this utility model.

[0098] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A fixed-focus lens, characterized in that, Comprising: A positive meniscus first lens with positive optical power, a field stop, a second lens with negative optical power, a third lens with positive optical power, a positive biconvex fourth lens, a negative biconcave fifth lens, a sixth lens with positive optical power, a vignetting stop, a positive biconvex seventh lens and a negative biconcave eighth lens arranged in sequence from the object side to the image side along the optical axis; Wherein, the image side surface of the second lens is concave, the object side surface of the third lens is convex, the image side surface of the sixth lens is convex, the second lens and the third lens are cemented into a first cemented lens, and the fourth lens and the fifth lens are cemented into a second cemented lens.

2. The fixed-focus lens according to claim 1, characterized in that, The object side surface of the second lens is concave or convex, and the image side surface of the third lens is concave or convex.

3. The fixed-focus lens according to claim 1, characterized in that, The optical power φ1 of the first lens and the optical power φ of the fixed-focus lens satisfy the relationship: 0.8 < φ1 / φ < 1.5; The refractive index ND1 of the first lens satisfies the relationship: 1.8 < ND1 < 2.

1.

4. The fixed-focus lens according to claim 1, characterized in that, The optical power φ2 of the second lens, the optical power φ3 of the third lens and the optical power φ23 of the first cemented lens satisfy the relationship: |φ2 + φ3 - φ23| < 0.1; The optical power φ2 of the second lens, the optical power φ3 of the third lens, the Abbe number vd2 of the second lens, and the Abbe number vd3 of the third lens satisfy the relationship: |100*(φ2 / vd2 + φ3 / vd3)| < 0.

5.

5. The fixed-focus lens according to claim 1, characterized in that, The optical power φ4 of the fourth lens, the optical power φ5 of the fifth lens and the optical power φ45 of the second cemented lens satisfy the relationship: |φ4 + φ5 - φ45| < 0.1; The optical power φ4 of the fourth lens, the optical power φ5 of the fifth lens, the Abbe number vd4 of the fourth lens, and the Abbe number vd5 of the fifth lens satisfy the relationship: |100*(φ4 / vd4 + φ5 / vd5)| < 0.

5.

6. The fixed-focus lens according to claim 1, characterized in that, The Abbe number vd3 of the third lens satisfies the relationship: 60 < vd3 < 96; the Abbe number vd4 of the fourth lens satisfies the relationship: 60 < vd4 < 96.

7. The fixed-focus lens according to claim 1, characterized in that, The optical power φ6 of the sixth lens, the optical power φ7 of the seventh lens, the optical power φ8 of the eighth lens and the optical power φ of the fixed-focus lens satisfy the relationship: -0.5 < φ6 / φ + φ7 / φ + φ8 / φ < 0.

35.

8. The fixed-focus lens according to claim 1, characterized in that, The semi-aperture SDmax of the first lens and the maximum image height H of the fixed-focus lens satisfy the relationship: 1 < SDmax / H < 1.

2.

9. The fixed-focus lens according to claim 1, characterized in that, The distance TTL from the center of the object side surface of the first lens to the center of the imaging surface and the focal length f of the fixed-focus lens satisfy the relationship: 1.1 < TTL / f < 1.

3.

10. A monitoring device, characterized in that, Including the fixed-focus lens according to any one of claims 1-9.

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