Athermal day and night confocal security lens

Abstract

The utility model discloses an athermal day and night confocal security lens. The lens is sequentially arranged from an object side to an image side along an optical axis of the lens: a first aspheric plastic lens with negative focal power; the second aspheric plastic lens has negative focal power; a spherical glass third lens with positive focal power; the fourth aspheric plastic lens has positive focal power; and the fifth aspheric plastic lens has negative focal power. One piece of spherical glass and four pieces of aspheric plastic are mixed and combined, reasonable lens material selection, focal power distribution and optical design optimization are adopted, a 5MP and 1 / 2.7 chip can be matched, 24-hour all-weather high-definition monitoring and day and night imaging confocal are achieved, and real shot pictures at the high temperature of 80 DEG C and the low temperature of-40 DEG C are clear.

Description

Technical Field

[0001] The invention relates to the technical field of optical lenses, and in particular to an athermal day-night confocal security lens. Background Art

[0002] The security monitoring system uses optical fiber, coaxial cable or microwave to transmit video signals in a closed loop, and constitutes an independent and complete system from camera to image display and recording. It can reflect the monitored object in real time, vividly and truthfully, and can replace manual long-term monitoring in harsh environments and record it through security lenses. With the increasing number of information security monitoring facilities, people have an increasing demand for monitoring equipment to work at night and achieve full-color images, which requires the lens to have a larger light transmittance and higher pixels.

[0003] Existing security lenses are generally composed of 4 to 8 plastic aspherical lenses, which have at least the following shortcomings:

[0004] 1. The lens pixel is not high, the resolution from the center to the edge is very different, and the uniformity is poor;

[0005] 2. The lens has large chromatic aberration, especially at the edges, which is not conducive to edge stitching;

[0006] 3. When the lens is used in high or low temperature environment, it is easy to cause defocus, resulting in reduced image quality and affecting use;

[0007] 4. The image quality of the lens is poor in bad weather, and it is difficult to achieve focus during the day and at night. The performance of the lens needs to be improved. Summary of the invention

[0008] Based on this, the purpose of the present invention is to provide a athermal day and night confocal security lens that can be used with a 5MP, 1 / 2.7 chip to achieve 24-hour all-weather high-definition monitoring, day and night imaging confocal, and clear real-time images at high temperatures of 80°C and low temperatures of -40°C.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] An athermal day and night confocal security lens is arranged in sequence from the object side to the image side along the lens optical axis:

[0011] A first lens, wherein the first lens is an aspheric plastic lens with negative optical power, the object side surface of the first lens is a convex surface, and the image side surface is a concave surface;

[0012] A second lens, wherein the second lens is an aspheric plastic lens with negative optical power, the object side surface of the second lens is a concave surface, and the image side surface is a convex surface;

[0013] Aperture diaphragm;

[0014] a third lens, wherein the third lens is a spherical glass lens with positive power, the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a convex surface;

[0015] a fourth lens, wherein the fourth lens is an aspheric plastic lens with positive refractive power, the object side surface of the fourth lens is a convex surface, and the image side surface is a convex surface;

[0016] A fifth lens, wherein the fifth lens is an aspheric plastic lens with negative optical power, wherein the object side surface of the fifth lens is a concave surface, and the image side surface of the fifth lens is a concave surface;

[0017] A filter, the filter is arranged on the image side of the fifth lens, and the filter is made of D263T glass;

[0018] A protective glass and an image acquisition element, wherein the protective glass is integrated on the image acquisition element, and the image acquisition element is arranged on the image side of the filter.

[0019] Furthermore, the lens satisfies the following relationship:

[0020] -2.93≤f1 / f≤-2.12,

[0021] -10.07≤f2 / f≤-6.23,

[0022] 1.51≤f3 / f≤1.66,

[0023] 0.88≤f4 / f≤1.07,

[0024] -1.24≤f5 / f≤-1.01;

[0025] In the relationship, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens.

[0026] Furthermore, the lens meets the following conditions:

[0027] IC / TTL ≥ 0.14,

[0028] 3.35≤TTL / f≤4.22,

[0029] 0.19≤OBFL / TTL≤0.25;

[0030] In the relationship, f is the total focal length of the lens, TTL is the total optical length of the lens, OBFL is the optical back focus of the lens, and IC is the full image height of the 1 / 2.7-inch chip used in the lens system.

[0031] Furthermore, the lens also satisfies the following relationship:

[0032] F#≤1.65,

[0033] 4.21mm≤f≤6.55mm,

[0034] TTL≤22.5mm;

[0035] In the relationship, F# is the aperture of the lens, f is the total focal length of the lens, and TTL is the total optical length of the lens.

[0036] Furthermore, the focal length, refractive index and curvature radius of the first lens, the second lens, the third lens, the fourth lens and the fifth lens respectively satisfy the following conditions:

[0037] f1 -18.27～-12.46 ND1 1.50～1.55 R11 +3.82～+5.17 R12 +1.97～+2.43 f2 -55.61～-37.34 ND2 1.60～1.66 R21 -7.78～-6.01 R22 -11.21～-10.03 f3 +8.51～+9.97 ND3 1.49～1.60 R31 +9.22～+11.18 R32 -8.62～-7.59 f4 +5.23～+6.86 ND4 1.50～1.55 R41 +5.12～+5.88 R42 -6.99～-5.80 f5 -6.99～-5.81 ND5 1.60～1.66 R51 -6.56～-5.98 R52 +11.67～+15.54

[0038] Wherein, f1 is the focal length of the first lens, ND1 is the refractive index of the first lens, R11 is the radius of curvature of the object side surface of the first lens, and R12 is the radius of curvature of the image side surface of the first lens;

[0039] f2 is the focal length of the second lens, ND2 is the refractive index of the second lens, R21 is the radius of curvature of the object side surface of the second lens, and R22 is the radius of curvature of the image side surface of the second lens;

[0040] f3 is the focal length of the third lens, ND3 is the refractive index of the third lens, R31 is the radius of curvature of the object side surface of the third lens, and R32 is the radius of curvature of the image side surface of the third lens;

[0041] f4 is the focal length of the fourth lens, ND4 is the refractive index of the fourth lens, R41 is the radius of curvature of the object side surface of the fourth lens, and R42 is the radius of curvature of the image side surface of the fourth lens;

[0042] f5 is the focal length of the fifth lens, ND5 is the refractive index of the fifth lens, R51 is the radius of curvature of the object side surface of the fifth lens, and R52 is the radius of curvature of the image side surface of the fifth lens;

[0043] Focal length: The "+" sign indicates that the lens has positive focal power, and the "-" sign indicates that the lens has negative focal power. The unit of focal length is mm;

[0044] Radius of curvature: The "+" sign indicates that the surface is bent toward the image plane, and the "-" sign indicates that the surface is bent toward the object plane. The unit is mm.

[0045] Furthermore, the aspheric surfaces of the first lens, the second lens, the fourth lens and the fifth lens satisfy the following formula:

[0046]

[0047] Wherein, Z is the vector height of the lens along the optical axis, k is the quadratic cone coefficient, γ is the lens height, c is the lens curvature, A, B, C, D, E, F, G are the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order coefficients of the aspheric polynomial.

[0048] The beneficial effects of the present invention are:

[0049] Through reasonable lens material selection, optical power distribution and optical design optimization, the present invention can be matched with a 5MP, 1 / 2.7 chip to achieve 24-hour all-weather high-definition monitoring, day and night imaging confocal, and clear real-time pictures at high temperatures of 80°C and low temperatures of -40°C.

[0050] The present invention adopts a mixed combination of one spherical glass and four aspherical plastics, the system aberration is well corrected, the optical performance is good, and in terms of manufacturability, each lens is insensitive, the lens surface is simple and easy to manufacture, and its processing cost is relatively low compared to that on the market. It has a high cost-effectiveness and can achieve the characteristics of small size, light weight, good performance and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Schematic diagram of the optical structure of embodiment 1 of the present invention;

[0052] Figure 2 This is a schematic diagram of the optical path structure of Example 1 of the present invention;

[0053] Figure 3 This is a field curvature diagram of visible light at 0.546 μm in Example 1 of the present invention;

[0054] Figure 4 This is a distortion curve diagram of visible light 0.546 μm F-Tan (Theta) in Example 1 of the present invention;

[0055] Figure 5 This is a ray fan diagram of Embodiment 1 of the present invention;

[0056] Figure 6 This is a defocus curve diagram of visible light 0.435-0.656 μm at room temperature +20°C in Example 1 of the present invention;

[0057] Figure 7 This is a defocus curve diagram of infrared light 0.850 μm at room temperature and 20° C. in Example 1 of the present invention;

[0058] Figure 8 This is a low-temperature -40°C defocus curve diagram of visible light 0.435-0.656 μm in Example 1 of the present invention;

[0059] Fig. 9 This is a high temperature +80°C defocus curve diagram of visible light 0.435-0.656 μm in Example 1 of the present invention;

[0060] Figure numerals: 1, first lens; 2, second lens; 3, third lens; 4, fourth lens; 5, fifth lens; 6, filter; 7, protective glass; 8, image acquisition element; 9, aperture stop. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. In this specification, the expressions first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. The shape of the spherical or aspherical surface is not limited to the shape of the spherical or aspherical surface shown in the drawings. The drawings are only examples and are not drawn strictly to scale.

[0062] In the present invention, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface 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 position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region; if the lens surface is not limited to convex, concave or flat, it means that the lens surface can be convex, concave or flat. The surface of each lens closest to the subject is called the object side of the lens, and the surface of each lens closest to the imaging surface is called the image side of the lens.

[0063] Unless otherwise defined, all terms (including technical terms and scientific terms) used in the present invention have the same meaning as commonly understood by those of ordinary skill in the art to which the present application belongs. It should also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having the same meaning as they have in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense, unless explicitly defined in the present invention.

[0064] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In order to better understand and implement, the present invention is described in detail below with reference to the accompanying drawings.

[0065] The present invention provides an athermal day and night confocal security lens, wherein the surface of the lens adjacent to the object plane is the object side surface, and the surface of the lens adjacent to the image plane is the image side surface. The following components are arranged in sequence from the object side to the image side along the optical axis of the lens: a first lens 1, a second lens 2, a third lens 3, an aperture stop 9, a fourth lens 4, a fifth lens 5, a filter 6, a protective glass 7, and an image acquisition element 8. The aperture stop 9 is arranged between the second lens 2 and the third lens 3; the filter 7 is arranged on the image side surface of the fifth lens 5, and the filter 6 is made of D263T glass. The protective glass 7 is integrated on the image acquisition element 8, and the image acquisition element 8 is arranged on the image side surface of the filter 6.

[0066] In the present invention, in order to make the optical system present better performance, we need to reasonably select lens materials, reasonably allocate the focal length of each lens and reasonably optimize the optical system during the design process, so as to finally optimize the performance of the optical system. Usually, the existence of aberrations in the optical system will affect the imaging quality of the optical system. Correcting aberrations is the key to optimizing the optical system. There are many ways to correct aberrations. For example, selecting lenses with different refractive indices and large differences in Abbe numbers for use can eliminate chromatic aberration and spherical aberration to a certain extent. Reasonable allocation and optimization of the focal length and shape of each lens can also correct the aberrations of the system.

[0067] In the present invention, f is the total focal length of the lens, f1 is the focal length of the first lens 1, f2 is the focal length of the second lens 2, f3 is the focal length of the third lens 3, f4 is the focal length of the fourth lens 4, f5 is the focal length of the fifth lens 5, f6 is the focal length of the sixth lens 6, the total focal length of the entire lens is f, and the ratio of the focal length of each lens to the total focal length of the lens satisfies the following conditions:

[0068] -2.93≤f1 / f≤-2.12,

[0069] -10.07≤f2 / f≤-6.23,

[0070] 1.51≤f3 / f≤1.66,

[0071] 0.88≤f4 / f≤1.07,

[0072] -1.24≤f5 / f≤-1.01.

[0073] In the present invention, F# is the aperture of the lens, f is the total focal length of the lens; TTL is the total optical length of the lens; OBFL is the optical back focus of the lens, which is the distance from the point on the image side of the fifth lens 5 closest to the image plane to the image plane; IC is the total image height of the 1 / 2.7 inch chip matched with the lens system; they meet the following conditions:

[0074] F#≤1.65,

[0075] 4.21mm≤f≤6.55mm,

[0076] TTL≤22.5mm,

[0077] IC / TTL ≥ 0.14,

[0078] 3.35≤TTL / f≤4.22,

[0079] 0.19≤OBFL / TTL≤0.25.

[0080] In the present invention, considering the aberration of the optical system and the problem of balanced temperature drift, the focal length, refractive index and curvature radius of each lens respectively meet the following conditions:

[0081] f1 -18.27～-12.46 ND1 1.50～1.55 R11 +3.82～+5.17 R12 +1.97～+2.43 f2 -55.61～-37.34 ND2 1.60～1.66 R21 -7.78～-6.01 R22 -11.21～-10.03 f3 +8.51～+9.97 ND3 1.49～1.60 R31 +9.22～+11.18 R32 -8.62～-7.59 f4 +5.23～+6.86 ND4 1.50～1.55 R41 +5.12～+5.88 R42 -6.99～-5.80 f5 -6.99～-5.81 ND5 1.60～1.66 R51 -6.56～-5.98 R52 +11.67～+15.54

[0082] Wherein, f1 is the focal length of the first lens 1, ND1 is the refractive index of the first lens 1, R11 is the curvature radius of the object side surface of the first lens 1, and R12 is the curvature radius of the image side surface of the first lens 1;

[0083] f2 is the focal length of the second lens 2, ND2 is the refractive index of the second lens 2, R21 is the curvature radius of the object side surface of the second lens 2, and R22 is the curvature radius of the image side surface of the second lens 2;

[0084] f3 is the focal length of the third lens 3, ND3 is the refractive index of the third lens 3, R31 is the curvature radius of the object side surface of the third lens 3, and R32 is the curvature radius of the image side surface of the third lens 3;

[0085] f4 is the focal length of the fourth lens 4, ND4 is the refractive index of the fourth lens 4, R41 is the curvature radius of the object side surface of the fourth lens 4, and R42 is the curvature radius of the image side surface of the fourth lens 4;

[0086] f5 is the focal length of the fifth lens 5, ND5 is the refractive index of the fifth lens 5, R51 is the radius of curvature of the object side surface of the fifth lens 5, and R52 is the radius of curvature of the image side surface of the fifth lens 5;

[0087] Focal length: The "+" sign indicates that the lens has positive focal power, and the "-" sign indicates that the lens has negative focal power. The unit of focal length is mm;

[0088] Radius of curvature: The "+" sign indicates that the surface is bent toward the image plane, and the "-" sign indicates that the surface is bent toward the object plane. The unit is mm.

[0089] In the present invention, the aspheric surfaces of the first lens 1, the second lens 2, the fourth lens 4 and the fifth lens 5 can be defined by the following equation of even-order aspheric surfaces:

[0090]

[0091] Where Z is the vector height of the lens along the optical axis, k is the quadratic cone coefficient, γ is the lens height, c is the lens curvature, and AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0092] The following is a specific implementation according to the above-mentioned configuration of the present invention and specifically describes the glass-plastic hybrid scanning lens according to the present invention. The specific implementation data are summarized in the following Table 1:

[0093] Table 1

[0094] Specific embodiments -2.93≤f1 / f≤-2.12 -2.88 -10.07≤f2 / f≤-6.23 -9.01 1.51≤f3 / f≤1.66 -1.55 0.88≤f4 / f≤1.07 0.99 -1.24≤f5 / f≤-1.01 -1.03 IC / TTL≥0.14 0.14 3.35≤TTL / f≤4.22 3.75 0.19≤OBFL / TTL≤0.25 0.22 F#≤1.65 1.6 4.21mm≤f≤6.55mm 6.0 TTL≤22.5mm 22.5 OBFL 5.0

[0095] refer to Figure 1 , Figure 2 As shown, they are respectively a schematic diagram of the optical structure and a schematic diagram of the optical path structure of an embodiment of the present invention.

[0096] The lenses in this embodiment are arranged in order from the object side to the image side along the lens optical axis:

[0097] The first lens 1 is an aspheric plastic lens with negative optical power, whose object side surface is convex and image side surface is concave;

[0098] The second lens 2 is an aspherical plastic lens with negative optical power, whose object side surface is concave and image side surface is convex;

[0099] Aperture stop 9;

[0100] The third lens 3 is a spherical glass lens with positive power, whose object side surface is convex and image side surface is convex;

[0101] The fourth lens 4 is an aspherical plastic lens with positive refractive power, the object side surface of which is convex, and the image side surface of which is convex;

[0102] The fifth lens 5 is an aspherical plastic lens 5 with negative optical power, whose object side surface is concave and image side surface is concave;

[0103] Filter 6;

[0104] Protective glass 7;

[0105] The image acquisition element 8 and the protective glass 7 are integrated on the image acquisition element 8 , and the image acquisition element 8 is arranged on the image side of the filter 6 .

[0106] In this embodiment, the lens matches a 1 / 2.7-inch chip, the field of view angle FOV of the lens system is > 68°, the total focal length f of the lens system is f=6.0 mm, the aperture value F# is 1.6, the total length TTL of the lens is TTL=22.5 mm, and the optical back focus OBFL of the lens is 5.0 mm.

[0107] In this embodiment, the first lens 1 is a meniscus-shaped lens with negative focal power, the convex surface of which faces the object side and the concave surface of which faces the image side, and its function is to quickly converge light; the Abbe numbers of the first lens 1 and the fourth lens 4 are greater than 55, and the Abbe numbers of the second lens 2 and the fifth lens 5 are less than 24. Such a combination can reduce the chromatic aberration of the system.

[0108] Taking into account the aberration of the optical system, balanced temperature drift, day and night confocality and other issues, the curvature radius, center thickness, refractive index, Abbe constant and aspheric K value of each lens are designed as shown in Table 2.

[0109] Table 2 gives the radius of curvature R (unit: mm) of each lens, the center thickness d (unit: mm) of each lens, the refractive index (ND) of each lens, the Abbe constant (VD) and the aspheric K value (Conic) of each lens.

[0110] Table 2

[0111] Surface number Curvature radius R Center thickness D Refractive index ND Abbe constant VD K Object INFINITY INFINITY Conic 11 4.09E+00 2.02E+00 1.54 55.71 -4.56E-01 12 2.17E+00 2.35E+00 -7.04E-01 21 -6.46E+00 3.24E+00 1.64 23.92 3.92E+00 22 -1.02E+01 -2.69E-02 -3.25E+00 Stop INFINITY 9.79E-02 0 31 9.75E+00 4.80E+00 1.81 25.48 0 32 -7.73E+00 1.00E-01 0 41 5.29E+00 2.35E+00 1.54 55.71 6.55E-01 42 -5.94E+00 5.00E-02 -1.12E+00 51 -6.32E+00 1.85E+00 1.64 23.92 -2.40E+00 52 1.43E+01 1.70E+00 2.30E+01 61 INFINITY 0.210 1.52 64.21 0 62 INFINITY 2.879 0 71 INFINITY 0.400 1.52 64.21 0 72 INFINITY 0.050 0 81 INFINITY 0

[0112] In Table 2, the radius of curvature R represents the degree of curvature of the lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side, wherein "INFINITY" represents that the surface is a plane; the center thickness D represents the center axial distance from the current surface to the next surface, the refractive index ND represents the light deflection ability of the current lens material, and the Abbe number VD represents the dispersion characteristics of the current lens material to the light; the k value represents the numerical value of the best fitting cone coefficient of the aspheric surface, 11 represents the object side surface of the first lens 1, 12 represents the image side surface of the first lens 1, and so on.

[0113] The aspheric surfaces of the first lens 1, the second lens 2, the fourth lens 4 and the fifth lens 5 of the embodiment of the present invention can all be defined by the above-mentioned equation of the even-order aspheric surface.

[0114] Table 3 gives various coefficients of the aspherical surfaces of the first lens 1 , the second lens 2 , the fourth lens 4 , and the fifth lens 5 .

[0115] Table 3

[0116] Surface number A B C D E F G 11 -2.00E-03 -1.18E-04 2.75E-06 1.66E-08 9.85E-09 3.26E-10 -3.51E-11 12 -3.11E-03 -1.02E-04 -1.92E-04 4.89E-05 5.31E-06 -3.17E-06 3.52E-07 21 5.59E-04 -1.28E-04 3.64E-05 1.37E-05 -2.02E-08 -1.00E-06 1.61E-07 22 -1.03E-03 -1.29E-05 4.49E-06 -2.42E-07 1.12E-07 -1.52E-08 5.79E-10 41 -1.274E-03 -7.749E-05 -1.372E-05 -6.491E-07 3.178E-08 -2.215E-09 -1.893E-09 42 7.316E-04 1.932E-05 -9.908E-06 -2.678E-06 7.721E-08 8.242E-09 -2.727E-10 51 1.305E-03 1.276E-04 -3.194E-06 -7.877E-07 -1.098E-07 7.323E-10 2.365E-09 52 2.266E-03 -4.103E-05 9.006E-06 4.359E-06 -5.078E-07 -1.228E-07 1.391E-08

[0117] refer to Figure 3 As shown, it is a distortion curve of visible light 0.546μm of this lens in this embodiment, the horizontal axis represents F-tan (Theta) distortion (unit: %), and the vertical axis represents the half field of view angle value (unit: °). It can be seen from the figure that the distortion within the full field of view of the lens is within -20%, indicating that the distortion is well corrected.

[0118] refer to Figure 4, which is a field curvature curve of the lens in the visible light range of 0.435-0.656 μm in this embodiment, wherein the vertical axis represents the half field angle value (unit: °), and the horizontal axis represents the field curvature amount (mm); Figure 4 It can be seen that the field curvature offset in the meridian and sagittal directions on the image plane is controlled within ±0.1mm, indicating that the field curvature of the lens is well corrected.

[0119] refer to Figure 5 As shown, the light aberration of the pupil coordinate function of this lens at different field angles in this embodiment is within a maximum scale of 50 μm, which indicates that the aberration control of each wavelength is well corrected.

[0120] refer to Figure 6 As shown in the figure, it is the through focus MTF curve of the lens in this embodiment under visible light of 125lp / mm. The horizontal axis represents the back focus variation range, and the horizontal axis is wider from -0.05mm to +0.05mm. The vertical axis represents the MTF value. Figure 6 It can be seen that the MTF performance of this lens is good.

[0121] refer to Figure 7 As shown in the figure, this is the through focus MTF curve of the lens in this embodiment when it switches to infrared light 0.850μm and 125lp / mm. Figure 6 It can be seen that the defocus of this lens is small, which means that the lens can meet the characteristics of day and night confocality, that is, it has higher clarity in night vision environments.

[0122] refer to Figure 8 and Fig. 9 As shown in the figure, the through focus MTF curves of the lens in this embodiment at a low temperature of -40°C and a high temperature of +80°C for visible light 125lp / mm, the horizontal axis represents the focal change range, the horizontal axis represents the focal width from -0.05mm to +0.05mm, and the vertical axis represents the MTF value. Figure 8 and Fig. 9 It can be seen that the lens can shoot high-definition images at high temperatures of +80°C and low temperatures of -40°C, and the lens has achieved a heat-free design.

[0123] To sum up, the athermal day and night confocal security lens adopts a mixed combination of 1 spherical glass and 4 aspherical plastics. While achieving the same quality in the industry, each lens is insensitive, the lens surface is simple and easy to manufacture, and its processing cost is relatively low compared to the market. It has a very high cost performance ratio and can achieve the characteristics of small size, light weight, good performance and low cost. In addition, the present invention comprehensively considers the aberration of the optical system, balanced temperature drift, day and night confocality and other issues. After reasonable lens material selection, optical power distribution and optical design optimization, it can be matched with a 5MP, 1 / 2.7-inch chip to achieve 24-hour all-weather high-definition monitoring, day and night imaging confocality, and clear real-life pictures at high temperatures of +80°C and low temperatures of -40°C.

[0124] The above only expresses the preferred technical solution of the present invention, and its description is relatively specific and detailed, but it 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 the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. An athermal day and night confocal security lens, characterized by: Set along the lens optical axis from the object side to the image side in order: A first lens, wherein the first lens is an aspheric plastic lens with negative optical power, the object side surface of the first lens is a convex surface, and the image side surface is a concave surface; A second lens, wherein the second lens is an aspheric plastic lens with negative optical power, the object side surface of the second lens is a concave surface, and the image side surface is a convex surface; Aperture diaphragm; a third lens, wherein the third lens is a spherical glass lens with positive power, the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a convex surface; a fourth lens, wherein the fourth lens is an aspheric plastic lens with positive refractive power, the object side surface of the fourth lens is a convex surface, and the image side surface is a convex surface; A fifth lens, wherein the fifth lens is an aspheric plastic lens with negative optical power, wherein the object side surface of the fifth lens is a concave surface, and the image side surface of the fifth lens is a concave surface; Filters, Protective glass and image acquisition components.

2. The athermal day and night confocal security lens according to claim 1, characterized in that: The lens satisfies the following relationship: -2.93≤f1 / f≤-2.12, -10.07≤f2 / f≤-6.23, 1.51≤f3 / f≤1.66, 0.88≤f4 / f≤1.07, -1.24≤f5 / f≤-1.01; In the relationship, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens.

3. The athermal day and night confocal security lens according to claim 1, characterized in that: The lens meets the following conditions: IC / TTL ≥ 0.14, 3.35≤TTL / f≤4.22, 0.19≤OBFL / TTL≤0.25; In the relationship, f is the total focal length of the lens, TTL is the total optical length of the lens, OBFL is the optical back focus of the lens, and IC is the full image height of the 1 / 2.7-inch chip used in the lens system.

4. The athermal day and night confocal security lens according to claim 1, characterized in that: The lens also satisfies the following relationship: F#≤1.65， 4.21mm≤f≤6.55mm, TTL≤22.5mm; In the relationship, F# is the aperture of the lens, f is the total focal length of the lens, and TTL is the total optical length of the lens.

5. The athermal day and night confocal security lens according to claim 1, characterized in that: The focal length ranges corresponding to the first lens, the second lens, the third lens, the fourth lens and the fifth lens are respectively -18.27 to -12.46, -55.61 to -37.34, +8.51 to +9.97, +5.23 to +6.86, and -6.99 to -5.81; wherein the "+" sign indicates that the lens has a positive focal power, and the "-" sign indicates that the lens has a negative focal power, and the unit of the focal length is mm.

6. The athermal day and night confocal security lens according to claim 1, characterized in that: The refractive index ranges corresponding to the first lens, the second lens, the third lens, the fourth lens and the fifth lens are 1.50-1.55, 1.60-1.66, 1.49-1.60, 1.50-1.55 and 1.60-1.66 respectively.

7. The athermal day and night confocal security lens according to claim 1, characterized in that: The object side surface radii of curvature corresponding to the first lens, the second lens, the third lens, the fourth lens and the fifth lens are in the range of +3.82 to +5.17, -7.78 to -6.01, +9.22 to +11.18, +5.12 to +5.88, and -6.56 to -5.98, respectively; wherein the "+" sign indicates that the surface is bent toward the image plane, and the "-" sign indicates that the surface is bent toward the object plane, and the unit of the curvature radius is mm.

8. The athermal day and night confocal security lens according to claim 1, characterized in that: The image side surface curvature radii corresponding to the first lens, the second lens, the third lens, the fourth lens and the fifth lens are in the range of +1.97 to +2.43, -11.21 to -10.03, -8.62 to -7.59, -6.99 to -5.80, and +11.67 to +15.54, respectively; wherein the "+" sign indicates that the surface is bent toward the image side, and the "-" sign indicates that the surface is bent toward the object side, and the unit of the curvature radius is mm.

9. The athermal day and night confocal security lens according to claim 1, characterized in that: The aperture stop is disposed between the second lens and the third lens; The filter is arranged on the image side of the fifth lens, and the filter is made of D263T glass; The protective glass is integrated on the image acquisition element, and the image acquisition element is arranged on the image side of the filter.

10. The athermal day and night confocal security lens according to claim 1, characterized in that: The aspheric surfaces of the first lens, the second lens, the fourth lens and the fifth lens satisfy the following formula: Wherein, Z is the vector height of the lens along the optical axis, k is the quadratic cone coefficient, γ is the lens height, c is the lens curvature, A, B, C, D, E, F, G are the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order coefficients of the aspheric polynomial.

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