A long focal length and small volume surveillance lens

Abstract

The present invention discloses a long focal length and small volume monitoring lens, which comprises a convex-concave positive lens L1, a biconvex positive lens L2, a biconcave negative lens L3, a convex-concave positive lens L4, a convex-concave positive lens L5, a biconcave negative lens L6, a convex-concave negative lens L7, a biconvex positive lens L8 and a convex-concave negative lens L9 arranged in sequence along the light incident direction, wherein: the biconvex positive lens L2, the biconcave negative lens L3 and the convex-concave positive lens L4 form a first cemented group; the convex-concave positive lens L5 and the biconcave negative lens L6 form a second cemented group; the convex-concave negative lens L7, the biconvex positive lens L8 and the convex-concave negative lens L9 form a third cemented group; and the following conditions are also satisfied: 0.74 < TTL / EFL < 0.76, 3.5 < EFL / BFL < 4.5. This application can clearly image under visible light and near-infrared light, reduce the aperture and compress the total length while achieving a long focal length, has a small volume, is convenient for assembly, has a low cost, and is suitable for long-distance monitoring and extreme environments.

Description

Technical Field

[0001] The invention belongs to the field of optical lenses, and in particular relates to a long-focal-length and small-volume monitoring lens. Background Art

[0002] Most of the surveillance lenses on the market are wide-angle lenses. They have the advantages of large aperture, wide monitoring range, and day and night imaging, which meet the requirements of security monitoring. However, with the continuous development of the market, more requirements are put forward for security lenses, and short-distance monitoring can no longer meet the needs of society. Telephoto lenses have a small field of view, a long monitoring distance, and can clearly image distant objects. However, due to the long focal length, the corresponding volume of this type of lens is relatively large. Therefore, it is urgent to design a small-volume telephoto lens that can achieve day and night imaging. Summary of the invention

[0003] The purpose of the present invention is to address the above problems and propose a long-focal-length, small-volume surveillance lens that can correct spherical aberration and chromatic aberration, can produce clear images without focusing under visible light and near-infrared light, has high imaging quality and resolution, can achieve a long focal length while reducing the aperture and compressing the total length, and has an optical imaging lens that does not shift the focal plane within the temperature range of -40°C to 80°C. The lens has a small size, is easy to assemble, and has a low cost, and is suitable for long-distance monitoring, such as traffic roads and forestry.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] The present invention provides a long focal length and small volume surveillance lens, comprising a convex-concave positive lens L1, a biconvex positive lens L2, a biconcave negative lens L3, a convex-concave positive lens L4, a concave-convex positive lens L5, a biconcave negative lens L6, a convex-concave negative lens L7, a biconvex positive lens L8 and a concave-convex negative lens L9, which are sequentially arranged along the incident direction of light, wherein:

[0006] The biconvex positive lens L2, the biconcave negative lens L3 and the convex-concave positive lens L4 form a first cemented group;

[0007] The meniscus positive lens L5 and the biconcave negative lens L6 form a second cemented group;

[0008] The convex-concave negative lens L7, the biconvex positive lens L8 and the concave-convex negative lens L9 form a third cemented group;

[0009] The long focal length and small size surveillance lens also meets the following conditions:

[0010] TTL / EFL<0.76,3.5 <EFL / BFL<4.5

[0011] Among them, TTL is the total length of the lens, EFL is the effective focal length of the lens, and BFL is the optical back focal length.

[0012] Preferably, a stop is provided on the object surface side of the biconvex positive lens L2.

[0013] Preferably, the focal length of the second glued group is negative.

[0014] Preferably, a filter is also provided on the image plane side of the third cemented group.

[0015] Preferably, the operating wavelength band of the long focal length and small volume monitoring lens is visible light 435-656nm or near infrared light below 850nm.

[0016] Preferably, the biconvex positive lens L2 is a glass lens with an Abbe number greater than 90.

[0017] Preferably, the biconcave negative lens L6, the convex-concave negative lens L7 and the convex-concave negative lens L9 are heavy lanthanum glass lenses.

[0018] Preferably, each lens is a spherical lens.

[0019] Preferably, the convex-concave positive lens L1, the biconvex positive lens L2, the biconcave negative lens L3, the convex-concave positive lens L4, the concave-convex positive lens L5, the biconcave negative lens L6, the convex-concave negative lens L7, the biconvex positive lens L8 and the concave-convex negative lens L9, respectively, have corresponding focal length value ranges of 39 (1±5%), 18.2 (1±5%), -8.2 (1±5%), 9 (1±5%), 9.8 (1±5%), -6.5 (1±5%), -5 (1±5%), 7 (1±5%) and -4.5 (1±5%); the corresponding refractive index value ranges are 1.59 (1±5%), 1.46 (1±5%), 1.6 (1±5%), 1.65 (1±5%), 1.92 (1±5%), 1.8 (1±5%), 1.85 (1 ±5%), 1.69 (1±5%) and 1.98 (1±5%); the corresponding object side curvature radius ranges are 20 (1±5%), 8.8 (1±5%), -96 (1±5%), 5.6 (1±5%), -120 (1±5%), -8.5 (1±5%), 82 (1±5%), 3.9 (1±5%) and -3.9 (1±5%); the corresponding image side curvature radius ranges are 145 (1±5%), -96 (1±5%), 5.6 (1±5%), 350 (1±5%), -8.5 (1±5%), 14 (1±5%), 3.9 (1±5%), -3.9 (1±5%) and -30 (1±5%), where “-” indicates that the mirror direction is bent toward the image side.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) Reasonable selection of focal length and aperture position can achieve long focal length while reducing the aperture and compressing the total length, which is suitable for long-distance monitoring, such as traffic roads and forestry;

[0022] 2) The heavy lanthanide and large Abbe number materials are selected to correct the prominent spherical aberration and chromatic aberration of the telephoto lens, and can produce clear images without focusing under visible light and near-infrared light, with high image quality and resolution;

[0023] 3) Use multiple sets of glued lenses to reduce chromatic aberration while lowering assembly and tolerance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present invention;

[0025] Figure 2 This is an MTF curve diagram of the first embodiment of the present invention at a normal temperature of 20°C;

[0026] Figure 3 This is a defocus curve diagram of Example 1 of the present invention at a room temperature of 20°C;

[0027] Figure 4 This is a defocus curve diagram of Example 1 of the present invention in a low temperature environment of -40°C;

[0028] Figure 5 This is a defocus curve diagram of Example 1 of the present invention under a high temperature environment of 80°C;

[0029] Figure 6 is an MTF curve diagram of the first embodiment of the present invention in near-infrared light;

[0030] Figure 7 This is the MTF curve of the second embodiment of the present invention at a room temperature of 20°C;

[0031] Figure 8 This is a defocus curve diagram of Example 2 of the present invention at a room temperature of 20°C;

[0032] Fig. 9 This is a defocus curve diagram of Example 2 of the present invention in a low temperature environment of -40°C;

[0033] Fig.10 This is a defocus curve diagram of Example 2 of the present invention under a high temperature environment of 80°C;

[0034] Fig.11 It is the MTF curve diagram of the second embodiment of the present invention in near infrared light. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0036] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0037] Embodiment 1:

[0038] like Figure 1-6 As shown, a long focal length small volume surveillance lens comprises a convex-concave positive lens L1, a double convex positive lens L2, a double concave negative lens L3, a convex-concave positive lens L4, a concave-convex positive lens L5, a double concave negative lens L6, a convex-concave negative lens L7, a double convex positive lens L8 and a concave-convex negative lens L9 which are sequentially arranged along the incident direction of light, wherein:

[0039] The biconvex positive lens L2, the biconcave negative lens L3 and the convex-concave positive lens L4 form a first cemented group;

[0040] The meniscus positive lens L5 and the biconcave negative lens L6 form a second cemented group;

[0041] The convex-concave negative lens L7, the biconvex positive lens L8 and the concave-convex negative lens L9 form a third cemented group;

[0042] The long focal length and small size surveillance lens also meets the following conditions:

[0043] TTL / EFL<0.76,3.5 <EFL / BFL<4.5

[0044] Among them, TTL is the total length of the lens, EFL is the effective focal length of the lens, and BFL is the optical back focal length.

[0045] Among them, the monitoring lens is composed of nine lenses distributed in sequence along the light incident direction. By reasonably allocating the optical power of each lens, under the conditions of TTL / EFL < 0.76 and 3.5 < EFL / BFL < 4.5, the total length of the lens is compressed to a small value relative to the effective focal length of the lens, so that the aperture can be reduced and the total length can be compressed in the case of long focal length. While satisfying clear imaging, it helps the lens to be miniaturized and lightweight, and there is a large space left for the back focal length to facilitate the structural design, such as the design of the lens barrel. At the same time, multiple cemented groups are adopted, and each cemented group is bonded with photosensitive glue, such as UV glue, to correct the chromatic aberration of light with different wavelengths. The dispersion of each type of lens can be compensated, so that the comprehensive chromatic aberration is reduced to the lowest level, and the assembly and tolerance requirements are reduced. The focus drift of the lens in the visible light and near-infrared light bands is greatly reduced, realizing day and night confocal, improving imaging clarity and color authenticity, reducing costs, and no longer requiring re-focusing for near-infrared imaging at night. And various aberrations mainly spherical aberration generated along with focusing are corrected, so as to achieve good optical performance. At the same time, the positive and negative focal length values of each lens are reasonably allocated to realize athermal design, solve the optimization balance problem between the focus drift at high and low temperatures and the resolution at normal temperature, without defocusing at high and low temperatures, adapt to the circuit heating of the external camera and the low temperature environment, be applicable to the temperature environment of -40° to 80°, with high imaging quality and resolution, and be applicable to long-distance monitoring, such as traffic roads and forestry.

[0046] In one embodiment, a diaphragm is provided on the object side of the biconvex positive lens L2.

[0047] Among them, a diaphragm is provided on the object side of the biconvex positive lens L2. Placing the diaphragm in front helps to reduce the lens aperture and achieve miniaturization and lightweight. The diaphragm can be set between the convex-concave positive lens L1 and the biconvex positive lens L2 or on the object side of the convex-concave positive lens L1.

[0048] In one embodiment, the focal length of the second cemented group is negative.

[0049] Among them, the second cemented group has a negative focal length, which is beneficial to balancing aberrations and improving imaging quality.

[0050] In one embodiment, a filter is further provided on the image side of the third cemented group.

[0051] Among them, the filter is placed on the image side of the convex-concave positive lens L9. During the day, it participates in the light path imaging and filters out near-infrared light to reduce photoelectric noise. At night, it allows near-infrared light to participate in imaging, enhances the photosensitive brightness, improves imaging quality, and can achieve day and night confocal.

[0052] In one embodiment, the working band of the long focal length and small volume monitoring lens is visible light 435~656nm or near-infrared light below 850nm.

[0053] Among them, the monitoring lens can take into account the clear imaging of visible light wavelengths of 435nm to 656nm or near-infrared light wavelengths below 850nm.

[0054] In one embodiment, the biconvex positive lens L2 is a glass lens with an Abbe number greater than 90.

[0055] Among them, the double convex positive lens L2 uses a glass lens with an Abbe number greater than 90, which reduces the chromatic aberration of the lens, improves the image quality, and is conducive to the athermal design of the lens.

[0056] In one embodiment, the biconcave negative lens L6, the convex-concave negative lens L7 and the convex-concave negative lens L9 are heavy lanthanum glass lenses.

[0057] Among them, the double concave negative lens L6, the convex-concave negative lens L7 and the concave-convex negative lens L9 are equipped with heavy lanthanum glass with high refractive index and relatively large Abbe number, which can correct the spherical aberration and infrared chromatic aberration of the telephoto lens, and is beneficial to improving the image quality of visible light and infrared. According to actual needs, other lenses can also be selected as heavy lanthanum glass or other materials with high refractive index and relatively large Abbe number as replacements.

[0058] In one embodiment, each lens is a spherical lens.

[0059] Among them, each lens adopts a spherical lens, which has low processing and assembly costs, is wear-resistant, and is suitable for mass production.

[0060] In one embodiment, the focal length ranges of the convex-concave positive lens L1, the biconvex positive lens L2, the biconcave negative lens L3, the convex-concave positive lens L4, the concave-convex positive lens L5, the biconcave negative lens L6, the convex-concave negative lens L7, the biconvex positive lens L8 and the concave-convex negative lens L9 are 39 (1±5%), 18.2 (1±5%), -8.2 (1±5%), 9 (1±5%), 9.8 (1±5%), -6.5 (1±5%), -5 (1±5%), 7 (1±5%) and -4.5 (1±5%); the refractive index ranges of the convex-concave positive lens L1, the biconvex positive lens L2, the biconcave negative lens L3, the convex-concave positive lens L4, the concave-convex positive lens L5, the biconcave negative lens L6, the convex-concave negative lens L7, the biconvex positive lens L8 and the concave-convex negative lens L9 are 39 (1±5%), 18.2 (1±5%), -8.2 (1±5%), 9 (1±5%), 9.8 (1±5%), -6.5 (1±5%), -5 (1±5%), 7 (1±5%) and -4.5 (1±5%); the refractive index ranges of the convex-concave positive lens L1, the biconvex positive lens L2, the biconcave negative lens L3 1±5%), 1.69(1±5%) and 1.98(1±5%); the corresponding object side curvature radius ranges are 20(1±5%), 8.8(1±5%), -96(1±5%), 5.6(1±5%), -120(1±5%), -8.5(1±5%), 82(1±5%), 3.9(1±5%) and -3.9(1±5%); the corresponding image side curvature radius ranges are 145(1±5%), -96(1±5%), 5.6(1±5%), 350(1±5%), -8.5(1±5%), 14(1±5%), 3.9(1±5%), -3.9(1±5%) and -30(1±5%), where “-” indicates that the mirror direction is bent toward the image side.

[0061] Among them, when the focal length, refractive index and curvature radius of each lens are within the above range, it helps to achieve miniaturization, lightweight and clear imaging of the lens.

[0062] Furthermore, if Figure 2-6 As shown, the optical parameters of each lens in this embodiment, including the radius of curvature, thickness, refractive index and Abbe number of the material, and focal length are as follows:

[0063]

[0064] Among them, the mirror surfaces of each lens are numbered in order from the incident direction of the light, that is, from the object plane to the imaging plane. R1 is the object side surface of the convex-concave positive lens L1, R2 is the image side surface of the convex-concave positive lens L1, R3 is the object side surface of the biconvex positive lens L2, R4 is the image side surface of the biconvex positive lens L2 and the object side surface of the biconcave negative lens L3, R5 is the image side surface of the biconcave negative lens L3 and the object side surface of the convex-concave positive lens L4, R6 is the image side surface of the convex-concave positive lens L4, and R7 is the concave-convex positive lens L8. The object side surface of lens L5, R8 is the image side surface of the meniscus positive lens L5 and the object side surface of the biconcave negative lens L6, R9 is the image side surface of the biconcave negative lens L6, R10 is the object side surface of the meniscus negative lens L7, R11 is the image side surface of the meniscus negative lens L7 and the object side surface of the biconvex positive lens L8, R12 is the image side surface of the biconvex positive lens L8 and the object side surface of the meniscus negative lens L9, R13 is the image side surface of the meniscus negative lens L9, and “-” indicates that the mirror direction is bent toward the image side.

[0065] In this embodiment, the effective focal length of the lens is 40.8 mm, the total length of the lens is 30.38 mm, and the maximum image plane φ=8.82 mm. Figure 2 As shown in the figure, the MTF curves in each field of view all drop gently, and the MTF value of the center field of view reaches 0.48 at 200lp / mm, and the MTF value of the edge field of view is greater than 0.25. The imaging effect and resolution of this lens are good. Figure 3 The defocus curves shown in the figure show that the curves under each field of view are very concentrated, the defocus is small, and the maximum field of view defocus is 0.01. Figure 4 , 5 As shown in the figure, the MTF curves at high and low temperatures indicate that the surveillance lens can maintain focus within a temperature range of -40°C to 80°C. Figure 6 As shown, this is a near-infrared MTF curve, which is close to the diffraction limit and can be used for near-infrared imaging to achieve day and night confocality. It can be used for night monitoring, with clear imaging and high imaging quality, meeting the requirements of long focal length and small volume.

[0066] Embodiment 2:

[0067] like Figure 1 and Figure 7-11 As shown, based on the solution described in Example 1, the optical parameters of each lens in this embodiment, including the radius of curvature, thickness, refractive index and Abbe number of the material, and focal length are as follows:

[0068]

[0069] Among them, the mirror surfaces of each lens are numbered in order from the incident direction of the light, that is, from the object plane to the imaging plane. R1 is the object side surface of the convex-concave positive lens L1, R2 is the image side surface of the convex-concave positive lens L1, R3 is the object side surface of the biconvex positive lens L2, R4 is the image side surface of the biconvex positive lens L2 and the object side surface of the biconcave negative lens L3, R5 is the image side surface of the biconcave negative lens L3 and the object side surface of the convex-concave positive lens L4, R6 is the image side surface of the convex-concave positive lens L4, and R7 is the concave-convex positive lens L8. The object side surface of lens L5, R8 is the image side surface of the meniscus positive lens L5 and the object side surface of the biconcave negative lens L6, R9 is the image side surface of the biconcave negative lens L6, R10 is the object side surface of the meniscus negative lens L7, R11 is the image side surface of the meniscus negative lens L7 and the object side surface of the biconvex positive lens L8, R12 is the image side surface of the biconvex positive lens L8 and the object side surface of the meniscus negative lens L9, R13 is the image side surface of the meniscus negative lens L9, and “-” indicates that the mirror direction is bent toward the image side.

[0070] In this embodiment, the effective focal length of the lens is 40.6 mm, the total length of the lens is 30.35 mm, and the maximum image plane φ=8.82 mm. Figure 7 As shown in the figure, the MTF curves in each field of view all drop gently, and the MTF value of the center field of view reaches 0.47 at 200lp / mm, and the MTF value of the edge field of view is greater than 0.3. The imaging effect and resolution of this lens are good. Figure 8 The defocus curves shown in the figure show that the curves under each field of view are very concentrated, the defocus is small, and the maximum field of view defocus is 0.01. Fig. 9 , 10 As shown in the figure, the MTF curves at high and low temperatures indicate that the surveillance lens can maintain focus within a temperature range of -40°C to 80°C. Fig.11 As shown, this is a near-infrared MTF curve, which is close to the diffraction limit and can be used for near-infrared imaging to achieve day and night confocality. It can be used for night monitoring, with clear imaging and high imaging quality, meeting the requirements of long focal length and small volume.

[0071] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The above-described embodiments only express the more specific and detailed embodiments described in this application, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of this application, which all belong to the protection scope of this application. Therefore, the protection scope of the patent in this application shall be based on the attached claims.

Claims

1. A long focal length and small volume surveillance lens, characterized in that: The long focal length small volume monitoring lens is composed of a convex-concave positive lens L1, a double convex positive lens L2, a double concave negative lens L3, a convex-concave positive lens L4, a concave-convex positive lens L5, a double concave negative lens L6, a convex-concave negative lens L7, a double convex positive lens L8 and a concave-convex negative lens L9 arranged in sequence along the incident direction of light, wherein: The biconvex positive lens L2, the biconcave negative lens L3 and the convex-concave positive lens L4 form a first cemented group; The meniscus positive lens L5 and the biconcave negative lens L6 form a second cemented group, and the focal length of the second cemented group is negative; The convex-concave negative lens L7, the double convex positive lens L8 and the convex-concave negative lens L9 form a third cemented group; The long focal length and small volume surveillance lens also meets the following conditions: 0.74 <TTL / EFL<0.76,3.5<EFL / BFL<4.5 Among them, TTL is the total length of the lens, EFL is the effective focal length of the lens, and BFL is the optical back focal length; Each of the lenses is a spherical lens, and the convex-concave positive lens L1, biconvex positive lens L2, biconcave negative lens L3, convex-concave positive lens L4, concave-convex positive lens L5, biconcave negative lens L6, convex-concave negative lens L7, biconvex positive lens L8 and concave-convex negative lens L9, respectively, have corresponding focal length ranges of 39 (1±5%), 18.2 (1±5%), -8.2 (1±5%), 9 (1±5%), 9.8 (1±5%), -6.5 (1±5%), -5 (1±5%), 7 (1±5%) and -4.5 (1±5%), in mm.

2. The long focal length small volume surveillance lens as claimed in claim 1, characterized in that: The object surface side of the biconvex positive lens L2 is provided with an aperture.

3. The long focal length small volume surveillance lens as claimed in claim 1, characterized in that: The image plane side of the third cemented group is also provided with a filter.

4. The long focal length small volume surveillance lens as claimed in claim 1, characterized in that: The operating wavelength band of the long focal length and small volume monitoring lens is 435-656nm visible light or near infrared light below 850nm.

5. The long focal length small volume surveillance lens as claimed in claim 1, characterized in that: The biconvex positive lens L2 is a glass lens with an Abbe number equal to 95.

6. The long focal length small volume surveillance lens as claimed in claim 1, characterized in that: The biconcave negative lens L6, the convex-concave negative lens L7 and the convex-concave negative lens L9 are heavy lanthanum glass lenses.

7. The long focal length small volume surveillance lens according to any one of claims 1 to 6, characterized in that: The corresponding refractive index ranges of the convex-concave positive lens L1, the double convex positive lens L2, the double concave negative lens L3, the convex-concave positive lens L4, the concave-convex positive lens L5, the double concave negative lens L6, the convex-concave negative lens L7, the double convex positive lens L8 and the concave-convex negative lens L9 are 1.59 (1±5%), 1.46 (1±5%), 1.6 (1±5%), 1.65 (1±5%), 1.92 (1±5%), 1.8 (1±5%), 1.85 (1±5%), 1.69 (1±5%) and 1.98 (1±5%) respectively; the corresponding object side surface curvature radius ranges are 20 (1±5%), 8. 8 (1±5%), -96 (1±5%), 5.6 (1±5%), -120 (1±5%), -8.5 (1±5%), 82 (1±5%), 3.9 (1±5%) and -3.9 (1±5%), in mm; the corresponding image side curvature radius ranges are 145 (1±5%), -96 (1±5%), 5.6 (1±5%), 350 (1±5%), -8.5 (1±5%), 14 (1±5%), 3.9 (1±5%), -3.9 (1±5%) and -30 (1±5%), in mm, where "-" indicates that the mirror is bent toward the image side.

Images