Large target surface infrared long-focus lens and imaging device

Abstract

The application belongs to the field of optical imaging and security and intelligent transportation imaging equipment, and specifically discloses a large-target infrared long-focus lens, which comprises, from the object side to the image side, a first lens L1 with positive refractive power, a second lens L2 with positive refractive power, a third lens L3 with negative refractive power, a fourth lens L4 with negative refractive power, a fifth lens L5 with positive refractive power, a sixth lens L6 with positive refractive power, a seventh lens L7 with positive refractive power, an eighth lens L8 with negative refractive power, and a ninth lens L9 with positive refractive power; the second lens L2 and the third lens L3 form a first cemented lens group G1, and the fourth lens L4 and the fifth lens L5 form a second cemented lens group G2; the focal length of the first cemented lens group G1 is f1, and the focal length of the second cemented lens group G2 is f2. The large-target infrared long-focus lens meets the requirements of large aperture, large target and short total length, effectively guarantees the low cost of the lens, and ensures the imaging quality.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging and security camera and intelligent transportation imaging equipment, specifically a large-area infrared telephoto lens and imaging device. Background Technology

[0002] With the development of security monitoring technology, the application scenarios for fixed-focus lenses are increasing. All-weather monitoring is an essential requirement for security lenses, demanding consistent image clarity under both visible and infrared illumination conditions. Therefore, there is a widespread demand for confocal lenses that support both visible and infrared light. In intelligent transportation systems, as the industry evolves, the resolution requirements for optical imaging lenses are becoming increasingly demanding, and the sensor surface size is also growing. Currently, the sensor surface sizes of lenses on the market are mainly concentrated in 1 / 1.8 inches and 1 / 1.2 inches, which cannot meet current usage requirements.

[0003] Conventional security monitoring and traffic surveillance cameras have the following drawbacks:

[0004] 1. The lens has a short focal length, which cannot meet the needs of telephoto viewing.

[0005] 2. The camera's target area is too small to meet the requirements for higher resolution.

[0006] 3. The lens resolution is not high, and the infrared confocal effect is mediocre.

[0007] Chinese utility model patent CN209117961U discloses an optical imaging system, a camera module, and an electronic device. The optical imaging system includes, along the optical axis from the object plane to the image plane, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens. The embodiments in this application improve the imaging quality of the optical imaging system through the rational design of the refractive power and surface shape of the first to ninth lenses, achieving high resolution and a large aperture imaging effect. However, the optical imaging lens provided in this patent is paired with a chip target surface of only 1 / 2.7 inches, making it difficult to match with chips with large target surfaces, and the short focal length cannot meet the requirements for telephoto lenses.

[0008] The following technical problems still exist in the existing technology:

[0009] 1. The lens design has a small target area, which is matched with a sensor with a small image area;

[0010] 2. The lens focal length is too short to meet the needs of viewing distant objects;

[0011] 3. The lens structure is large in size, the lens processing characteristics are poor, and the cost is high;

[0012] 4. The near-infrared band imaging requirements were not considered, resulting in blurry images and poor image quality in low-light conditions at night.

[0013] Therefore, there is an urgent need in the market for a large-area infrared telephoto lens and imaging equipment. Summary of the Invention

[0014] To address the aforementioned technical problems in the prior art, this invention provides a large-area infrared telephoto lens, comprising, from the object side to the image side: a first lens L1 with positive optical power, a second lens L2 with positive optical power, a third lens L3 with negative optical power, a fourth lens L4 with negative optical power, a fifth lens L5 with positive optical power, a sixth lens L6 with positive optical power, a seventh lens L7 with positive optical power, an eighth lens L8 with negative optical power, and a ninth lens L9 with positive optical power; the second lens L2 and the third lens L3 form a first cemented lens group G1, and the fourth lens L4 and the fifth lens L5 form a second cemented lens group G2; the focal length of the first cemented lens group G1 is f. G1 The focal length of the second cemented lens group G2 is f. G2 The lens has a system focal length of f and a field of view of FOV; it satisfies the following relationship:

[0015]

[0016] Furthermore, the first lens L1 is a meniscus lens; the second lens L2 is a meniscus lens; the third lens L3 is a meniscus lens; the fourth lens L4 is a meniscus lens; the fifth lens L5 is a meniscus lens; the sixth lens L6 is a meniscus lens; the seventh lens L7 is a meniscus lens; the eighth lens L8 is a biconcave lens; and the ninth lens L9 is a biconvex lens.

[0017] Furthermore, the eighth lens L8 has a concave surface on both the object side and the image side.

[0018] Furthermore, the ninth lens L9 has a convex surface on both the object side and the image side.

[0019] Furthermore, the central radius of curvature R8 of the image side of the fifth lens L5 and the central radius of curvature R10 of the object side of the seventh lens L7 satisfy the following:

[0020]

[0021] Furthermore, the system focal length f of the large-target infrared telephoto lens satisfies the following relationship with the total optical length TTL:

[0022] TTL / f≤1.2 (3).

[0023] Furthermore, the focal lengths f1 of the first lens L1, f6 of the sixth lens L6, and f9 of the ninth lens L9 of the large-target infrared telephoto lens satisfy the following formula:

[0024] f1≤80 (4)

[0025] f6≥50 (5)

[0026] f9≥20 (6).

[0027] Furthermore, the Abbe number Vd7 of the seventh lens L7 and the Abbe number Vd9 of the ninth lens L9 of the large-target infrared telephoto lens satisfy the following formula:

[0028] Vd7≤40.9 (7)

[0029] Vd9≤25.5 (8).

[0030] Furthermore, the refractive index Nd3 of the third lens L3 and the refractive index Nd7 of the seventh lens L7 of the large target surface infrared telephoto lens satisfy the following relationship:

[0031] Nd3≤1.72 (9)

[0032] Nd7≤1.92 (10).

[0033] An imaging device, the imaging device comprising the large-area infrared telephoto lens described above.

[0034] Beneficial effects

[0035] The large-area infrared telephoto lens of this invention satisfies the requirements of a large aperture, a large target area, and a short overall length, effectively ensuring low lens cost while maintaining image quality. It has the following characteristics:

[0036] 1. The lens aperture is no greater than 1.8, while meeting the market demand for short overall length, large target area, and high resolution;

[0037] 2. Under the condition of MTF@100lp / mm, the MTF value of visible light full field of view reaches 0.5 or above, and the MTF value of infrared light full field of view reaches 0.3 or above;

[0038] 3. The lens adopts an all-glass design, which has good processability and lower cost control. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of an optical lens in the prior art;

[0040] Figure 2 This is a schematic diagram of the structure of the optical lens of this application;

[0041] Figure 3 This is an optical transfer function (MTF) curve of Embodiment 1 of the optical lens provided in this application at room temperature in the visible light band;

[0042] Figure 4 This is an optical transfer function (MTF) curve of Embodiment 1 of the optical lens provided in this application at room temperature in the infrared light band;

[0043] Figure 5a and Figure 5b This is a field curvature and distortion diagram of Embodiment 1 of the optical lens provided in this application in the visible light band;

[0044] Figure 6 This is a lateral fan pattern in the visible light band of Embodiment 1 of the optical lens provided in this application;

[0045] Figure 7 This is a dot plot of Embodiment 1 of the optical lens provided in this application in the visible light band;

[0046] Figure 8 This is an optical transfer function (MTF) curve of Embodiment 2 of the optical lens provided in this application at room temperature in the visible light band;

[0047] Figure 9 This is an optical transfer function (MTF) curve of Embodiment 1 of the optical lens provided in this application at room temperature in the infrared light band;

[0048] Figure 10a and Figure 10b This is a field curvature and distortion diagram in the visible light band of Embodiment 2 of the optical lens provided in this application;

[0049] Figure 11 This is a lateral fan pattern in the visible light band of Embodiment 2 of the optical lens provided in this application;

[0050] Figure 12 This is a dot plot of Embodiment 2 of the optical lens provided in this application in the visible light band;

[0051] Figure 13 This is a schematic diagram of a specific embodiment of the imaging device provided in this application. Detailed Implementation

[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0053] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0054] like Figure 2 As shown, the large-target infrared telephoto lens of the present invention comprises, from the object side to the image side, the following elements in sequence: a first lens L1 with positive optical power, a second lens L2 with positive optical power, a third lens L3 with negative optical power, a fourth lens L4 with negative optical power, a fifth lens L5 with positive optical power, a sixth lens L6 with positive optical power, a seventh lens L7 with positive optical power, an eighth lens L8 with negative optical power, and a ninth lens L9 with positive optical power.

[0055] An aperture stop (STOP) is provided between the fifth lens L5 and the sixth lens L6; the image side of the eighth lens L8 is also provided with a color filter and an imaging surface.

[0056] Optionally, the first lens L1 is a meniscus lens; the second lens L2 is a meniscus lens; the third lens L3 is a meniscus lens; the fourth lens L4 is a meniscus lens; the fifth lens L5 is a meniscus lens; the sixth lens L6 is a meniscus lens; the seventh lens L7 is a meniscus lens; the eighth lens L8 is a biconcave lens; and the ninth lens L9 is a biconvex lens.

[0057] The first lens L1 to the ninth lens L9 are all made of glass.

[0058] The second lens L2 and the third lens L3 form the first cemented lens group G1, and the fourth lens L4 and the fifth lens L5 form the second cemented lens group G2.

[0059] The focal length of the first cemented lens group G1 is f. G1 The focal length of the second cemented lens group G2 is f. G2 The lens has a system focal length of f and a field of view of FOV; it satisfies the following relationship:

[0060]

[0061] The eighth lens L8 has a concave surface on both the object side and the image side.

[0062] The ninth lens L9 has a convex surface on both the object side and the image side.

[0063] The central radius of curvature R8 of the image side of the fifth lens L5 and the central radius of curvature R10 of the object side of the seventh lens L7 satisfy the following:

[0064]

[0065] The system focal length f of the large-target infrared telephoto lens satisfies the following relationship with the total optical length TTL:

[0066] TTL / f≤1.2 (3).

[0067] The focal lengths f1 of the first lens L1, f6 of the sixth lens L6, and f9 of the ninth lens L9 of the large-target infrared telephoto lens satisfy the following formula:

[0068] f1≤80 (4)

[0069] f6≥50 (5)

[0070] f9≥20 (6).

[0071] The Abbe number Vd7 of the seventh lens L7 and the Abbe number Vd9 of the ninth lens L9 of the large target infrared telephoto lens satisfy the following formula:

[0072] Vd7≤40.9 (7)

[0073] Vd9≤25.5 (8).

[0074] The refractive indices Nd3 of the third lens L3 and Nd7 of the seventh lens L7 of the large-target infrared telephoto lens satisfy the following relationship:

[0075] Nd3≤1.72 (9)

[0076] Nd7≤1.92 (10).

[0077] Example 1

[0078] The radius of curvature R, center thickness Tc, refractive index Nd, Abbe constant Vd, and conic coefficient k of each lens in the large-target infrared telephoto lens of this embodiment 1 satisfy the conditions listed in Table 1:

[0079]

[0080] Table 1 Lens Parameter Table

[0081] It should be noted that the mirror serial numbers in Table 1 are Figure 2The diagram shows the lens face numbers from left to right in the large target infrared telephoto lens structure diagram.

[0082] The large-area infrared telephoto lens provided in Embodiment 1 has the following optical specifications:

[0083] Total optical length (TTL) ≤ 79.3 mm;

[0084] Lens focal length f: 70mm;

[0085] Lens field of view: 14°;

[0086] Lens optical distortion: 1.6%;

[0087] The aperture of the lens system is Fn. 1.76;

[0088] Lens image size: 1.1".

[0089] In this embodiment 1, the focal length of the first cemented lens group G1 of the optical lens is f. G1 The focal length of the second cemented lens group G2 is f. G2 The system focal length of the lens is f, and the field of view is FOV, satisfying the following: The central radius of curvature R8 of the image side of the fifth lens L5 and the central radius of curvature R10 of the object side of the sixth lens L6 satisfy the following: The system focal length f of the optical lens and the total optical length TTL of the optical lens satisfy the following relationship: The focal length of the first lens L1 of the optical lens is f1 = 70.24, the focal length of the sixth lens L6 is f6 = 78.39, and the focal length of the ninth lens L9 is f9 = 21.45; the Abbe number of the seventh lens L7 of the optical lens is Vd7 = 40.9, and the Abbe number of the ninth lens L9 is Vd9 = 25.5; the refractive index of the third lens L3 of the optical lens is Nd3 = 1.67, and the refractive index of the seventh lens L7 is Nd7 = 1.58.

[0090] Example 2

[0091] The radius of curvature R, center thickness Tc, refractive index Nd, Abbe constant Vd, and conic coefficient k of each lens in the large-area infrared telephoto lens of this embodiment 2 satisfy the conditions listed in Table 2:

[0092]

[0093]

[0094] Table 2 Lens Parameter Table.

[0095] It should be noted that the mirror serial numbers in Table 2 are... Figure 2The diagram of the optical lens structure shown has the lens face numbers from left to right.

[0096] The large-area infrared telephoto lens provided in this embodiment 2 has the following optical technical specifications:

[0097] Total optical length (TTL) ≤ 80.0 mm;

[0098] Lens focal length f: 70mm;

[0099] Lens field of view: 14°;

[0100] Lens optical distortion: -1.26%;

[0101] The aperture of the lens system is Fn. 1.76;

[0102] Lens image size: 1".

[0103] In this embodiment 2, the focal length of the first cemented lens group G1 of the optical lens is f. G1 The focal length of the second cemented lens group G2 is f. G2 The system focal length of the lens is f, and the field of view is FOV, satisfying the following: The central radius of curvature R8 of the image side of the fifth lens L5 and the central radius of curvature R10 of the object side of the sixth lens L6 satisfy the following: The system focal length f of the optical lens and the total optical length TTL of the optical lens satisfy the following relationship: The focal length of the first lens L1 of the optical lens is f1 = 56.1, the focal length of the sixth lens L6 is f6 = 59.88, and the focal length of the ninth lens L9 is f9 = 28.3; the Abbe number of the first lens L7 of the optical lens is Vd7 = 35.3, and the Abbe number of the ninth lens L9 is Vd9 = 20.9; the refractive index of the third lens L3 of the optical lens is Nd3 = 1.72, and the refractive index of the seventh lens L7 is Nd7 = 1.92.

[0104] In summary, Examples 1 to 2 satisfy the relationships shown in Table 3 below.

[0105]

[0106] Table 3. Comprehensive table of parameter relationships.

[0107] The optical transfer function is a relatively accurate, intuitive, and common way to evaluate the imaging quality of an imaging system. The higher and smoother the curve, the better the imaging quality of the system and the better it corrects various aberrations (such as spherical aberration, coma, astigmatism, field curvature, axial chromatic aberration, and transverse chromatic aberration).

[0108] from Figure 3 , Figure 8As can be seen from the diagram, the optical transfer function (MTF) curve of this imaging system under visible light is relatively smooth and concentrated, and the average MTF value of the entire field of view (half-image height Y' = 8.8 mm) reaches more than 0.5; it can be seen that the imaging system provided in this embodiment can meet high imaging requirements.

[0109] from Figure 4 , Figure 9 As can be seen from the image, the optical transfer function (MTF) curve of the imaging system at infrared 850° is relatively smooth and concentrated, and the average MTF value of the entire field of view (half-image height Y' = 8.8 mm) reaches more than 0.3; it can be seen that the imaging system provided in this embodiment can meet high imaging requirements.

[0110] from Figure 5a , Figure 5b and Figure 10a , Figure 10b As can be seen, the field curvature of this imaging system is controlled within ±0.06mm, and the distortion control of this imaging system is good, within 1.5%.

[0111] from Figure 6 and Figure 11 As can be seen from the image, the curves in the optical sector diagram are relatively concentrated, indicating that the spherical aberration and dispersion of this imaging system are well controlled.

[0112] from Figure 7 and Figure 12 As can be seen from this, the imaging system has a small and relatively concentrated spot radius, and the corresponding aberrations and coma are well controlled.

[0113] In summary, embodiments 1 and 2 of this invention provide a high-resolution imaging system with long optical focal length, short total optical length, large aperture, large target surface, low cost, and infrared confocal imaging. By employing nine optical lenses with specific structural shapes, arranged sequentially from the object side to the image side, and through the specific allocation and combination of the optical power of each optical lens, the imaging system achieves infrared confocal imaging characteristics.

[0114] like Figure 13 As shown, the imaging device 10 of this application embodiment includes at least one large-area infrared telephoto lens 11. Specifically, the large-area infrared telephoto lens 11 can be the optical lens of the above embodiments 1 and 2, and its specific structure will not be described in detail here.

[0115] In this embodiment, the imaging device 10 can be applied to the security field, for example, it can be installed on smart buildings to provide high-definition environmental information for building security systems. In other embodiments, the imaging device 10 can also be applied to other devices, such as intelligent transportation equipment, drones, and robotic vacuum cleaners.

Claims

1. A large-area infrared telephoto lens, comprising, from the object side to the image side: The system comprises a first lens L1 with positive optical power, a second lens L2 with positive optical power, a third lens L3 with negative optical power, a fourth lens L4 with negative optical power, a fifth lens L5 with positive optical power, a sixth lens L6 with positive optical power, a seventh lens L7 with positive optical power, an eighth lens L8 with negative optical power, and a ninth lens L9 with positive optical power; the first lens L1 is a meniscus lens with its convex surface facing the object side; the second lens L2 is a meniscus lens with its convex surface facing the object side; and the third lens L3 is a meniscus lens with its convex surface facing the object side. The fourth lens L4 is a lens with a concave image side; the fifth lens L5 is a meniscus lens with a convex object side; the sixth lens L6 is a meniscus lens with a convex object side; the seventh lens L7 is a lens with a convex image side; the eighth lens L8 is a biconcave lens; and the ninth lens L9 is a biconvex lens. The second lens L2 and the third lens L3 form a first cemented lens group G1, and the fourth lens L4 and the fifth lens L5 form a second cemented lens group G2. The focal length of the first cemented lens group G1 is... The focal length of the second cemented lens group G2 is... The system focal length of the lens is The field of view is The following relationship must be satisfied: （1）。 2. The large-target infrared telephoto lens according to claim 1, characterized in that: The eighth lens L8 has a concave surface on both the object side and the image side.

3. The large-area infrared telephoto lens according to claim 1, characterized in that: The ninth lens L9 has a convex surface on both the object side and the image side.

4. The large-area infrared telephoto lens according to claim 1, characterized in that: The central radius of curvature R8 of the image side of the fifth lens L5 and the central radius of curvature R10 of the object side of the seventh lens L7 satisfy the following: （2）。 5. The large-area infrared telephoto lens according to claim 1, characterized in that: The system focal length of the large-target infrared telephoto lens is: The following conditions must be met with the total optical length TTL: （3）。 6. The large-target infrared telephoto lens according to claim 1, characterized in that: The focal lengths f1 of the first lens L1, f6 of the sixth lens L6, and f9 of the ninth lens L9 of the large-target infrared telephoto lens satisfy the following formula: f1≤80 （4） f6≥50 （5） f9≥20 （6）。 7. The large-area infrared telephoto lens according to claim 1, characterized in that: The Abbe number Vd7 of the seventh lens L7 and the Abbe number Vd9 of the ninth lens L9 of the large target infrared telephoto lens satisfy the following formula: Vd7≤40.9 (7) Vd9≤25.5 (8)。 8. The large-area infrared telephoto lens according to claim 1, characterized in that: The refractive indices Nd3 of the third lens L3 and Nd7 of the seventh lens L7 of the large-target infrared telephoto lens satisfy the following relationship: Nd3≤1.72 (9) Nd7≤1.92 (10).

9. An imaging device, characterized in that, The imaging device includes the large-area infrared telephoto lens as described in any one of claims 1 to 8.

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