Large-target-surface ultra-wide-angle security monitoring optical system

Abstract

The utility model discloses a security monitoring optical system with a large target surface and an ultra-wide angle. The security monitoring optical system sequentially comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a diaphragm, a sixth lens, a seventh lens, an eighth lens, an optical filter, protective glass and an image surface from an object surface to an image surface along an optical axis, the object plane side of the first lens is a convex surface, and the image plane side is a concave surface. The object surface side of the second lens is a convex surface, and the image surface side is a concave surface; the object plane side of the third lens is a concave surface, and the image plane side is a concave surface; the object plane side of the fourth lens is a plane, and the image plane side is a convex surface; the object plane side of the fifth lens is a convex surface, and the image plane side is a convex surface; the object plane side of the sixth lens is a concave surface, and the image plane side is a concave surface; the object plane side of the seventh lens is a convex surface, and the image plane side is a convex surface; the object plane side of the eighth lens is a convex surface, and the image plane side is a convex surface; wherein the sixth lens and the seventh lens form a group of glued lenses. The utility model has the characteristics of ultra wide angle, large target surface, high definition pixel, high edge illumination and stable thermal drift.

Description

Technical Field

[0001] The utility model relates to the technical field of optical imaging, in particular to a large target surface ultra-wide angle security monitoring optical system. Background Technique

[0002] In the field of security, network cameras are undoubtedly the core cornerstone for building an efficient and secure protection system. They not only achieve seamless connection of remote monitoring and real-time management by virtue of advanced network transmission technology, but also greatly broaden the flexibility and coverage of monitoring, becoming an indispensable part of modern security.

[0003] The lens, as the "eye" of the network camera, is of self-evident importance. The lens is not only a capturer of light, but also a decisive factor in imaging quality. It is responsible for accurately converting the external optical signal into an electrical signal, and then forming the video image we see. However, with the development of science and technology, the image sensor chips in the imaging system are constantly updated and iterated, and the imaging requirements for the lens are also getting higher and higher. Most of the current security lenses have a small field of view, poor resolution, unclear night shooting, are greatly affected by temperature when working outdoors, and cannot achieve stable imaging. Therefore, how to provide a lens with ultra-wide angle, high definition, high relative illumination, and stable thermal drift is a problem that needs to be solved by those skilled in the art. Content of the Utility Model

[0004] The utility model provides a large target surface ultra-wide angle security monitoring optical system, which has the characteristics of ultra-wide angle, high definition, large target surface, high edge illumination, and basically unchanged resolution under high and low temperature environments.

[0005] The above technical purpose of the utility model is achieved through the following technical solutions: a large target surface ultra-wide angle security monitoring optical system, which sequentially includes, along the optical axis from the object surface to the image surface: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a diaphragm, a sixth lens, a seventh lens, an eighth lens, a filter, a protective glass, and an image surface;

[0006] The object surface side of the first lens is convex, and the image surface side is concave;

[0007] The object surface side of the second lens is convex, and the image surface side is concave;

[0008] The object surface side of the third lens is concave, and the image surface side is concave;

[0009] The object surface side of the fourth lens is flat, and the image surface side is convex;

[0010] The object surface side of the fifth lens is convex, and the image surface side is convex;

[0011] The object surface side of the sixth lens is concave, and the image surface side is concave;

[0012] The object side of the seventh lens is convex, and the image side is convex;

[0013] The object side of the eighth lens is convex, and the image side is convex;

[0014] The sixth lens and the seventh lens form a cemented lens group;

[0015] And satisfy the following relational expressions:

[0016] 1.68 < Nd1 < 1.75; 1.74 < Nd2 < 1.82; 1.43 < Nd3 < 1.51; 1.9 < Nd4 < 1.98; 1.6 < Nd5 < 1.68; 1.80 < Nd6 < 1.88; 1.53 < Nd7 < 1.6; 1.73 < Nd8 < 1.8;

[0017] Wherein, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, Nd3 is the refractive index of the third lens, Nd4 is the refractive index of the fourth lens, Nd5 is the refractive index of the fifth lens, Nd6 is the refractive index of the sixth lens, Nd7 is the refractive index of the seventh lens, and Nd8 is the refractive index of the eighth lens.

[0018] A further solution is that the Abbe number Vd1 of the first lens and the Abbe number Vd2 of the second lens are both greater than 48 and less than 57; the Abbe number Vd3 of the third lens and the Abbe number Vd7 of the seventh lens are both greater than 67 and less than 75.

[0019] A further solution is that the field of view FOV of the optical system satisfies the following conditions:

[0020] 198° ≤ FOV ≤ 201°.

[0021] A further solution is that the effective focal length f of the optical system satisfies the following conditions:

[0022] 2.0mm ≤ f ≤ 2.25mm.

[0023] A further solution is that: the relative illumination of the optical system satisfies the following conditions:

[0024] RI ≥ 70%.

[0025] A further solution is that the first lens is meniscus-shaped and its optical power is negative;

[0026] The second lens is meniscus-shaped and its optical power is negative;

[0027] The third lens is biconcave, and the curvature radius of the object side is greater than that of the image side, and its optical power is negative;

[0028] The fourth lens is plano-convex, with a flat surface on the object side and a convex surface on the image side, and its optical power is positive;

[0029] The fifth lens is biconvex, with a convex surface on the object side and a convex surface with a flat platform on the image side, and its optical power is positive;

[0030] The sixth lens is biconcave, with the radius of curvature on the object side smaller than that on the image side, and its optical power is negative;

[0031] The seventh lens is biconvex, with a convex surface with a flat platform on the object side and the radius of curvature on the object side larger than that on the image side, and its optical power is negative;

[0032] The eighth lens is biconvex, with a convex surface with a flat platform on the object side and a convex surface on the image side, and its optical power is positive.

[0033] Furthermore, the aperture stop is disposed between the fifth lens and the sixth lens.

[0034] In summary, the present utility model has the following beneficial effects:

[0035] Ultra-wide-angle field of view 198° ≤ FOV ≤ 201°: The field of view covers almost the entire surrounding environment of the camera, reducing blind spots and providing a more comprehensive range for the security system.

[0036] Ultra-high marginal illuminance: The maximum relative illuminance of the marginal field of view of this optical system is greater than 70%, with high marginal illuminance, and clear imaging can still be achieved under low-brightness conditions such as cloudy days and nights.

[0037] High-definition shooting: It meets the high-quality shooting of 8 million pixels and can present high-resolution and high-brightness picture effects.

[0038] Maintaining the resolution basically unchanged in high and low temperature environments: In an environment with large temperature changes, such as direct sunlight or cold weather, the optical system can still maintain stable imaging performance and will not cause a decline in imaging quality due to temperature changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the optical system provided by the embodiment of the present utility model;

[0040] Figure 2 It is an MTF analysis diagram provided by the embodiment of the present utility model;

[0041] Figure 3 It is a defocus curve diagram of the optical system provided by the embodiment of the present utility model at 20°C;

[0042] Figure 4 It is a defocus curve diagram of the optical system provided by the embodiment of the present utility model at -40°C;

[0043] Figure 5 The defocus curve graph of the optical system provided by the embodiment of the present utility model at 85°C;

[0044] Figure 6 The field curvature curve graph of the optical system provided by the embodiment of the present utility model;

[0045] Figure 7 The relative illumination graph of the optical system provided by the embodiment of the present utility model. Detailed implementation manners

[0046] The embodiments of the present utility model will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present utility model, and should not be construed as a limitation of the present utility model.

[0047] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present utility model.

[0048] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present utility model, "a plurality of" means two or more unless otherwise specifically defined.

[0049] In the present utility model, unless otherwise clearly defined and limited, the terms "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0050] Such as Figure 1As shown in the figure, this embodiment provides a large target surface ultra-wide angle security monitoring optical system, which sequentially includes, along the optical axis from the object surface to the image surface: a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a diaphragm STO, a sixth lens E6, a seventh lens E7, an eighth lens E8, a filter IR, a protective glass CG, and an image surface IMA;

[0051] The object surface side S1 of the first lens E1 is convex, and the image surface side S2 is concave;

[0052] The object surface side S3 of the second lens E2 is convex, and the image surface side S4 is concave;

[0053] The object surface side S5 of the third lens E3 is concave, and the image surface side S6 is concave;

[0054] The object surface side S7 of the fourth lens E4 is flat, and the image surface side S8 is convex;

[0055] The object surface side S9 of the fifth lens E5 is convex, and the image surface side S10 is convex;

[0056] The object surface side S11 of the sixth lens E6 is concave, and the image surface side S12 is concave;

[0057] The object surface side S13 of the seventh lens E7 is convex, and the image surface side S14 is convex;

[0058] The object surface side S15 of the eighth lens E8 is convex, and the image surface side S16 is convex;

[0059] The sixth lens E6 and the seventh lens E7 form a set of cemented lenses;

[0060] And the following relational expressions are satisfied:

[0061] 1.68 < Nd1 < 1.75; 1.74 < Nd2 < 1.82; 1.43 < Nd3 < 1.51; 1.9 < Nd4 < 1.98; 1.6 < Nd5 < 1.68; 1.80 < Nd6 < 1.88; 1.53 < Nd7 < 1.6; 1.73 < Nd8 < 1.8;

[0062] Wherein, Nd1 is the refractive index of the first lens E1, Nd2 is the refractive index of the second lens E2, Nd3 is the refractive index of the third lens E3, Nd4 is the refractive index of the fourth lens E4, Nd5 is the refractive index of the fifth lens E5, Nd6 is the refractive index of the sixth lens E6, Nd7 is the refractive index of the seventh lens E7, and Nd8 is the refractive index of the eighth lens E8.

[0063] Furthermore, the Abbe number Vd1 of the first lens E1 and the Abbe number Vd2 of the second lens E2 are both greater than 48 and less than 57; the Abbe number Vd3 of the third lens E3 and the Abbe number Vd7 of the seventh lens E7 are both greater than 67 and less than 75.

[0064] Furthermore, the field of view angle FOV of the optical system satisfies the following conditions:

[0065] 198° ≤ FOV ≤ 201°.

[0066] Furthermore, the effective focal length f of the optical system satisfies the following conditions:

[0067] 2.0 mm ≤ f ≤ 2.25 mm.

[0068] Furthermore, the relative illumination of the optical system satisfies the following conditions:

[0069] RI ≥ 70%.

[0070] Furthermore, the first lens E1 is meniscus-shaped and has a negative optical power;

[0071] The second lens E2 is meniscus-shaped and has a negative optical power;

[0072] The third lens E3 is biconcave, and the object side S5 is a large concave surface and the image side S6 is a small concave surface, that is, the radius of curvature of the object side S5 is greater than the radius of curvature of the image side S6, and its optical power is negative;

[0073] The fourth lens E4 is plano-convex, and the object side S7 is a plane and the image side S8 is a convex surface, and its optical power is positive;

[0074] The fifth lens E5 is biconvex, and the object side S9 is a convex surface and the image side S10 is a convex surface with a flat platform, and its optical power is positive;

[0075] The sixth lens E6 is biconcave, and the object side S11 is a small concave surface and the image side S12 is a large concave surface, that is, the radius of curvature of the object side S11 is less than the radius of curvature of the image side S12, and its optical power is negative;

[0076] The seventh lens E7 is biconvex, and the object side S13 is a large convex surface with a flat platform and the image side S14 is a small convex surface, that is, the radius of curvature of the object side S13 is greater than the radius of curvature of the image side S14, and its optical power is negative;

[0077] The eighth lens E8 is biconvex, and the object side S15 is a convex surface with a flat platform and the image side S16 is a convex surface, and its optical power is positive.

[0078] In this embodiment, when the working distance is infinity, the total focal length f of the optical system (lens) is 2.18 mm, FNO = 2.0, the field of view FOV = 200°, and the maximum image circle is 7.6 mm.

[0079] This specific embodiment is only an explanation of the present utility model and is not a limitation thereof. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present utility model, it is protected by the patent law.

[0080] Among them, the parameters of each lens in this embodiment are listed in Table 1 below, and the aspheric coefficients of the lens are shown in Table 2 below.

[0081] Table 1 Physical parameters of each lens

[0082]

[0083] The aspheric coefficient satisfies the following equation:

[0084]

[0085] Among them, z is the aspheric sag, c is the aspheric paraxial curvature, the curvature is the reciprocal of the radius of curvature, y is the lens aperture, k is the conic coefficient, a4 is the 4th-order aspheric coefficient, a6 is the 6th-order aspheric coefficient, a8 is the 8th-order aspheric coefficient, and a10 is the 10th-order aspheric coefficient.

[0086] Table 2 Aspheric coefficients of the lens

[0087]

[0088] Specifically, in this embodiment, the surface number (surface), R value (Radius radius of curvature), thickness (Thickness), refractive index (Index), Abbe number (ABB), and effective focal length of the lens (EFL-E) of each lens surface are shown in Table 1. INFINITY in Table 1 represents infinity, and the aspheric parameters are shown in Table 2. In Table 2, R1 represents the radius of curvature of the side of the corresponding lens facing the object side, and R2 represents the radius of curvature of the side of the corresponding lens facing the image side.

[0089] In this embodiment, Figure 2It is shown as the modulation transfer function (MTF) curve graph in the visible light band, which represents the comprehensive resolution ability of the optical system. In the graph, the horizontal axis represents the spatial frequency, unit: cycle / mm (100 lp / mm), and the vertical axis represents the value of the modulation transfer function (MTF). The value of MTF is used to evaluate the imaging quality of the lens, and the value range is 0 - 1. It should be specifically pointed out that the optical transfer function is a relatively accurate, intuitive, and common way to evaluate the imaging quality of an optical system. The higher and smoother its curve is, the better the imaging quality of the system is, and the stronger the ability to restore the real image. From Figure 2 it can be seen that in the visible light band, when the spatial frequency is 100 lp / mm, the MTF in the imaging area near the center is > 0.7, and the imaging quality is good. Figure 3 It is shown as the defocus curve graph at 20 °C in the visible light band. From Figure 3 it can be seen that the MTF concentration of this lens is good, which is convenient for focusing. From Figure 4 and Figure 5 it can be seen that the defocus curves at low temperature of -40 °C and high temperature of 85 °C both meet the high resolution, the change amount of the defocus curve focus is small, and the thermal drift effect is stable. Figure 6 It is shown as the field curvature graph. From Figure 6 it can be known that the field curvature value is controlled between -0.012 mm and 0.012 mm. The smaller the field curvature value is, the better the imaging quality of the lens is. Figure 7 It is shown as the relative illumination graph. From Figure 7 it can be known that the relative illumination of the maximum marginal field of view is greater than 70%. The marginal illumination is high, and it can still clearly image under the conditions of low brightness on cloudy days and at night, fully meeting the technical requirements of the market.

[0090] This specific embodiment is only an explanation of the present utility model, and it is not a limitation to the present utility model. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present utility model, it is protected by the patent law.

Claims

1. A large-target ultra-wide-angle security monitoring optical system, characterized in that: The optical axis includes, from the object plane to the image plane, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, an aperture, a sixth lens, a seventh lens, an eighth lens, a filter, a protective glass and an image plane; The object side of the first lens is convex, and the image side is concave; The object side of the second lens is convex, and the image side is concave; The object side of the third lens is concave, and the image side is concave; The object side of the fourth lens is a flat surface, and the image side is a convex surface; The fifth lens has a convex object surface side and a convex image surface side; The sixth lens has a concave object surface side and a concave image surface side; The seventh lens has a convex object surface and a convex image surface. The eighth lens has a convex object surface and a convex image surface. The sixth lens and the seventh lens form a cemented lens group; And the following relationship is satisfied: 1.68<Nd1<1.75; 1.74<Nd2<1.82; 1.43<Nd3<1.51; 1.9<Nd4<1.98 ;1.6<Nd5<1.68; 1.80<Nd6<1.88; 1.53<Nd7<1.6; 1.73<Nd8<1.8; Among them, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, Nd3 is the refractive index of the third lens, Nd4 is the refractive index of the fourth lens, Nd5 is the refractive index of the fifth lens, Nd6 is the refractive index of the sixth lens, Nd7 is the refractive index of the seventh lens, and Nd8 is the refractive index of the eighth lens.

2. The large-target-surface ultra-wide-angle security monitoring optical system according to claim 1, characterized in that: The Abbe constant Vd1 of the first lens and the Abbe constant Vd2 of the second lens are both greater than 48 and less than 57; the Abbe constant Vd3 of the third lens and the Abbe constant Vd7 of the seventh lens are both greater than 67 and less than 75.

3. The large-target-surface ultra-wide-angle security monitoring optical system according to claim 1, characterized in that: The field of view FOV of the optical system meets the following conditions: 198°≤FOV≤201°.

4. The large-target-surface ultra-wide-angle security monitoring optical system according to claim 1, characterized in that: The effective focal length f of the optical system satisfies the following conditions: 2.0mm≤f≤2.25mm.

5. The large-target-surface ultra-wide-angle security monitoring optical system according to claim 1, characterized in that: The relative illumination of the optical system meets the following conditions: RI≥70%.

6. The large-target-surface ultra-wide-angle security monitoring optical system according to claim 1, characterized in that: The first lens is meniscus-shaped and has negative focal power; The second lens is meniscus-shaped and has negative optical power; The third lens is biconcave, and the curvature radius of the object side is larger than the curvature radius of the image side, and its optical power is negative; The fourth lens is plano-convex, with a flat surface on the object side and a convex surface on the image side, and its optical power is positive; The fifth lens is biconvex, with a convex surface on the object side and a convex surface with a platform on the image side, and its optical power is positive; The sixth lens is biconcave, and the curvature radius of the object side is smaller than the curvature radius of the image side, and the optical power is negative; The seventh lens is biconvex, and the object side is a convex surface with a platform, and the curvature radius of the object side is greater than the curvature radius of the image side, and the optical power is negative; The eighth lens is biconvex, with a convex surface with a platform on the object side and a convex surface on the image side, and its optical power is positive.

7. The large-target-surface ultra-wide-angle security monitoring optical system according to claim 1, characterized in that: The aperture stop is disposed between the fifth lens and the sixth lens.

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