A small surveillance lens with low distortion, large transmittance, large target area and high resolution

Abstract

The present invention discloses a small surveillance lens with low distortion, large light transmission, large target surface and high resolution, which comprises, in order from the object side to the image side along the optical axis: a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, an aperture C, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a ninth lens L9, wherein the second lens L2 and the third lens L3 are closely connected to form a first cemented lens group; the seventh lens L7 and the eighth lens L8 are closely connected to form a second cemented lens group; the first lens L1 to the fifth lens L5 form a front lens group; the sixth lens L6 to the ninth lens L9 form a rear lens group; the surveillance lens satisfies the following condition: 2.2≤FOV / CRA≤4.171, wherein FOV is the maximum field angle of the surveillance lens, and CRA is the chief ray angle of the optical system. The surveillance lens of the present invention has the performance of low distortion, large light transmission, large target surface, high resolution and miniaturization.

Description

Technical Field

[0001] The invention belongs to the technical field of optical lenses, and in particular relates to a small monitoring lens with low distortion, large light flux, large target surface and high resolution. Background Art

[0002] Surveillance cameras are important components for intelligent transportation equipment to obtain surrounding data. They play the role of "eyes" in the intelligent transportation system and determine the accuracy of the information obtained.

[0003] Due to the particularity of the application environment, the performance of surveillance lenses needs to be different from that of ordinary lenses, such as lower imaging distortion, larger imaging target area and higher resolution.

[0004] The existing surveillance lenses have certain deficiencies in meeting the above requirements. The market needs a surveillance lens with small size, low distortion, large light transmission, large target area and high resolution.

[0005] Therefore, inventing a surveillance camera that meets the above requirements has become a more urgent need. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a small surveillance lens with low distortion, large light transmission, large target surface and high resolution, so that it has the performance of miniaturization, low distortion, large light transmission, large target surface and high resolution.

[0007] To achieve the above object, the present invention provides the following technical solution: a small surveillance lens with low distortion, large light flux, large target surface and high resolution, which comprises, in order from the object side to the image side along the optical axis: a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, an aperture C, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a ninth lens L9,

[0008] The first lens L1 is a negative meniscus lens with its convex surface facing the object;

[0009] The second lens L2 is a double concave negative lens;

[0010] The third lens L3 is a biconvex positive lens;

[0011] The fourth lens L4 is a meniscus positive lens or a biconvex positive lens with a convex surface facing the image side;

[0012] The fifth lens L5 is a double concave negative lens;

[0013] The sixth lens L6 is a biconvex positive lens;

[0014] The seventh lens L7 is a biconvex positive lens;

[0015] The eighth lens L8 is a double concave negative lens;

[0016] The ninth lens L9 is a biconvex positive lens or a meniscus positive lens with the convex surface facing the object;

[0017] The second lens L2 and the third lens L3 are closely connected to form a first cemented lens group; the seventh lens L7 and the eighth lens L8 are closely connected to form a second cemented lens group;

[0018] The first lens L1 to the fifth lens L5 constitute a front lens group; the sixth lens L6 to the ninth lens L9 constitute a rear lens group;

[0019] The monitoring lens satisfies the following condition: 2.2≤FOV / CRA≤4.171, where FOV is the maximum field of view of the monitoring lens and CRA is the chief ray angle of the optical system.

[0020] As a specific implementation, the monitoring lens satisfies the following condition: (FOV×f) / IH≤109, where FOV is the maximum field of view of the monitoring lens, f is the effective focal length of the monitoring lens, and IH is the maximum image plane height of the monitoring lens.

[0021] As a specific implementation method, the monitoring camera satisfies the following condition: u1 / f|≤1.3,|f u2 / f|≥0.8, where f u1 is the effective focal length of the front lens group, f u2 is the effective focal length of the rear lens group, and f is the effective focal length of the monitoring lens. Preferably, 1.2≤|f u1 / f|≤1.3,0.8≤|f u2 / f|≤0.95.

[0022] As a specific implementation method, the monitoring lens satisfies the following condition: SD max / TTL≤0.3, where SD max is the clear aperture of the largest lens in the monitoring lens, and TTL is the total optical length of the monitoring lens, that is, the distance from the center of the object side of the first lens L1 to the imaging surface.

[0023] As a specific implementation, the monitoring lens satisfies the following condition: FOV / (D×TTL)≥0.02, where FOV is the maximum field of view of the monitoring lens, D is the aperture size of the monitoring lens head, and TTL is the total optical length of the monitoring lens.

[0024] As a specific implementation, the monitoring lens satisfies the following condition: IH / FNO≥5.3, where IH is the maximum image plane height of the monitoring lens, and FNO is the aperture value of the monitoring lens. Preferably, 5.3≤IH / FNO≤5.4.

[0025] As a specific implementation, the monitoring lens satisfies the following conditional formula: (FOV×TTL) / BFL≥260, wherein FOV is the maximum field angle of the monitoring lens, TTL is the total optical length of the monitoring lens, and BFL is the distance from the image side surface of the ninth lens L9 to the image plane IMG in the monitoring lens. Preferably, 260≤(FOV×TTL) / BFL≤317.

[0026] As a specific implementation, the eleventh lens L11 satisfies the following conditions: N d9 ≤1.8;V D9 ≥44, where N d9 is the refractive index of the ninth lens L9, V D9 is the Abbe number of the ninth lens L9.

[0027] Compared with the prior art, the present invention provides a small surveillance lens with low distortion, large light transmission, large target surface and high resolution, which has the following beneficial effects:

[0028] 1) The present invention continuously corrects the propagation light in the optical system by reasonably combining different lenses, thereby achieving the requirement of low distortion;

[0029] 2) The present invention realizes the high resolution requirement of the optical system by reasonably allocating the positions of lenses with different optical powers;

[0030] 3) The present invention realizes high-resolution imaging of the optical system by reasonably allocating the optical power of the front group and the rear group. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the optical path diagram of the small surveillance lens with low distortion, large light flux, large target surface and high resolution in Example 1;

[0032] Figure 2 This is the MTF curve of the small surveillance lens with low distortion, large light flux, large target surface and high resolution in the visible light band in Example 1;

[0033] Figure 3 This is a field curvature distortion diagram of the small surveillance lens with low distortion, large light flux, large target surface and high resolution in Example 1;

[0034] Figure 4 This is the optical path diagram of the small surveillance lens with low distortion, large light flux, large target surface and high resolution in Example 2;

[0035] Figure 5 This is the MTF curve of the visible light band of the small surveillance lens with low distortion, large light transmission, large target surface and high resolution in Example 2;

[0036] Figure 6This is a field curvature distortion diagram of the small surveillance lens with low distortion, large light flux, large target surface and high resolution in Example 2;

[0037] Figure 7 This is the optical path diagram of the small surveillance lens with low distortion, large light flux, large target surface and high resolution in Example 3;

[0038] Figure 8 This is the MTF curve of the visible light band of the small surveillance lens with low distortion, large light transmission, large target surface and high resolution in Example 3;

[0039] Fig. 9 This is a field curvature distortion diagram of the small surveillance lens with low distortion, large light flux, large target surface and high resolution in Example 3. DETAILED DESCRIPTION

[0040] 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. 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.

[0041] The present invention provides a small surveillance lens with low distortion, large light flux, large target surface and high resolution, which comprises, in order from the object side to the image side along the optical axis: a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, an aperture C, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a ninth lens L9.

[0042] Among them, the first lens L1 is a meniscus negative lens with the convex surface facing the object; the second lens L2 is a double concave negative lens; the third lens L3 is a double convex positive lens; the fourth lens L4 is a meniscus positive lens or a double convex positive lens with the convex surface facing the image side; the fifth lens L5 is a double concave negative lens; the sixth lens L6 is a double convex positive lens; the seventh lens L7 is a double convex positive lens; the eighth lens L8 is a double concave negative lens; and the ninth lens L9 is a double convex positive lens or a meniscus positive lens with the convex surface facing the object side.

[0043] The second lens L2 and the third lens L3 are closely connected to form a first cemented lens group; the seventh lens L7 and the eighth lens L8 are closely connected to form a second cemented lens group; the first lens L1 to the fifth lens L5 form a front lens group; the sixth lens L6 to the ninth lens L9 form a rear lens group;

[0044] Here, the first lens L1 is a meniscus lens, which focuses the light entering the lens, which is beneficial for obtaining more light.

[0045] The second lens L2 and the third lens L3 are glued together as a glued part to eliminate or balance the distortion produced by the lens and reduce the tolerance sensitivity. In addition, the second lens L2 and the third lens L3 are both glass lenses, which can effectively improve the stability and durability of the lens group.

[0046] The fourth lens L4 can compress the light collected by the front cemented lens, so that the light can smoothly transition to the rear optical system.

[0047] The fifth lens L5 can correct the light collected by the fourth lens L4 to optimize the imaging performance of the lens group.

[0048] The aperture C is placed between the fifth lens L5 and the sixth lens L6 to control the imaging quality and the performance of the optical system by limiting the propagation range and direction of the light beam.

[0049] The sixth lens L6 can compress the light corrected by the fifth lens L5 and transition it to the rear optical system.

[0050] The seventh lens L7 and the eighth lens L8 are cemented parts, which perform secondary correction on the light collected by the sixth lens L6 to balance the distortion produced by the lens. The seventh lens L7 and the eighth lens L8 use glass lenses to further enhance the stability of the lens group.

[0051] The ninth lens L9 can focus the light corrected by the cemented lens and correct the aberration to optimize the imaging performance of the lens group.

[0052] The lenses in the following embodiments are all made of glass. Example 1

[0053] In the optical system of this example, the first lens L1 is a meniscus negative lens with the convex surface facing the object; the second lens L2 is a double concave negative lens; the third lens L3 is a double convex positive lens; the fourth lens L4 is a double convex positive lens; the fifth lens L5 is a double concave negative lens; the sixth lens L6 is a double convex positive lens; the seventh lens L7 is a double convex positive lens; the eighth lens L8 is a double concave negative lens; and the ninth lens L9 is a double convex positive lens. The second lens L2 and the third lens L3, the seventh lens L7 and the eighth lens L8 are glued together respectively. The optical path diagram of the monitoring lens is shown in FIG. Figure 1 shown.

[0054] See Table 1, which lists the relevant parameters of each lens in this example, including the radius of curvature, thickness, refractive index of the material, and Abbe number:

[0055] Table 1

[0056]

[0057] Infinity means infinity.

[0058] In this example, the air distance from the first lens L1 to the second lens L2 is 7.8839 mm; the air distance from the third lens L3 to the fourth lens L4 is 11.2436 mm; the air distance from the fourth lens L4 to the fifth lens L5 is 0.9860 mm; the air distance from the fifth lens L5 to the aperture C is 5.5700 mm; the air distance from the aperture C to the sixth lens L6 is -0.1929 mm; the air distance from the sixth lens L6 to the seventh lens L7 is 2.9500 mm; the air distance from the eighth lens L8 to the ninth lens L9 is 2.1589 mm; and the air distance from the ninth lens L9 to the image plane IMG is 19.9207 mm.

[0059] The technical indicators achieved by the optical system in this example are as follows:

[0060] 1) Maximum field of view of the surveillance camera: FOV = 55.5000°;

[0061] 2) Effective focal length of the front lens: f u1 =-27.2124mm;

[0062] 3) Effective focal length of the rear lens group: f u2 =20.3254mm;

[0063] 4) Effective focal length of surveillance lens: f=21.96mm;

[0064] 5) Chief ray angle of the optical system: CRA = 13.7175°;

[0065] 6) Maximum image height of the surveillance lens: IH = 11.2370 mm;

[0066] 7) Aperture value of monitoring lens: FNO = 2.0986;

[0067] 8) Monitoring lens head aperture size: D = 24.9363mm;

[0068] 9) The aperture of the largest lens in the surveillance lens: SD max =24.9363mm;

[0069] 10) The distance from the image side of the ninth lens L9 to the image plane IMG in the monitoring lens: BFL = 19.9207 mm;

[0070] 12) Total optical length of the monitoring lens: TTL = 93.9221mm.

[0071] Then we can get: FOV / CRA=4.0459; (FOV×f) / IH=108.4678;|f u1 / f|=1.2391;|fu2 / f|=0.9255; SD max / TTL=0.27; FOV / (D×TTL)=0.0237; IH / FNO=5.3545; (FOV×TTL) / BFL=261.6716.

[0072] Here, the requirement of low distortion is achieved by reasonably allocating the positions of each lens in the optical system, that is, 2.2≤FOV / CRA≤4.1.

[0073] By rationally combining different lenses, that is, requiring (FOV×f) / IH≤109, the propagation light in the optical system is continuously corrected to achieve the demand for low distortion.

[0074] By reasonably allocating the proportion of the front and rear group focal lengths to the focal length of the entire lens, that is, requiring |f u1 / f|≤1.3,|f u2 / f|≥0.8, to meet the high resolution requirement of the system.

[0075] By limited SD max / TTL≤0.3, FOV / (D×TTL)≥0.02, which realizes the miniaturization of the lens. By limiting IH / FNO≥5.3, (FOV×TTL) / BFL≥260, the demand for a large target surface is met.

[0076] By limiting the refractive index and Abbe number of the ninth lens L9 and using glass that is friendly to thermal drift, the stability of the lens group is effectively improved.

[0077] The final imaging effect of the lens in this example is achieved through Figure 2 The MTF graph of the lens shows that the MTF curves in each field of view all drop gently and have good consistency. It can be seen from the graph that the MTF value is greater than 0.5 at the spatial frequency of 60pl / mm in the edge field of view, which means that the lens has good imaging effect and resolution in the full field of view. Figure 3 This is the field curvature distortion diagram of the lens of this embodiment. It can be seen that the distortion of the lens does not exceed 3%. Example 2

[0078] In this example, in the optical system, the first lens L1 is a meniscus negative lens with the convex surface facing the object; the second lens L2 is a double concave negative lens; the third lens L3 is a double convex positive lens; the fourth lens L4 is a meniscus positive lens with the convex surface facing the object; the fifth lens L5 is a double concave negative lens; the sixth lens L6 is a double convex positive lens; the seventh lens L7 is a double convex positive lens; the eighth lens L8 is a double concave negative lens; and the ninth lens L9 is a double convex positive lens. The optical path diagram of the monitoring lens is shown in Figure 4 shown.

[0079] See Table 2, which lists the relevant parameters of each lens in this example, including the radius of curvature, thickness, refractive index of the material, and Abbe number:

[0080] Table 2

[0081]

[0082] Infinity means infinity.

[0083] In this example, the air distance from the first lens L1 to the second lens L2 is 7.8471 mm; the air distance from the third lens L3 to the fourth lens L4 is 10.3966 mm; the air distance from the fourth lens L4 to the fifth lens L5 is 0.9771 mm; the air distance from the fifth lens L5 to the aperture C is 5.4225 mm; the air distance from the aperture C to the sixth lens L6 is -0.2069 mm; the air distance from the sixth lens L6 to the seventh lens L7 is 4.6500 mm; the air distance from the eighth lens L8 to the ninth lens L9 is 2.1306 mm; and the air distance from the ninth lens L9 to the image plane IMG is 18.5925 mm.

[0084] The technical indicators achieved by the optical system in this example are as follows:

[0085] 1) Maximum field of view of the surveillance camera: FOV = 55.5000°;

[0086] 2) Effective focal length of the front lens: f u1 =-26.7089mm;

[0087] 3) Effective focal length of the rear lens group: f u2 =19.7998mm;

[0088] 4) Effective focal length of surveillance lens: f=21.97mm;

[0089] 5) Chief ray angle of the optical system: CRA = 13.7240°;

[0090] 6) Maximum image height of the surveillance lens: IH = 11.2370 mm;

[0091] 7) Aperture value of monitoring lens: FNO = 2.0996;

[0092] 8) Monitoring lens head aperture size: D = 25.0485mm;

[0093] 9) The aperture of the largest lens in the surveillance lens: SD max =25.0485mm;

[0094] 10) The distance from the image side of the ninth lens L9 to the image plane IMG in the monitoring lens: BFL = 18.5925 mm;

[0095] 12) Total optical length of the monitoring lens: TTL = 93.9008mm.

[0096] Then we can get: FOV / CRA=4.0440; (FOV×f) / IH=108.5023;|f u1 / f|=1.2158;|f u2 / f|=0.9013; SD max / TTL=0.27; FOV / (D×TTL)=0.0236; IH / FNO=5.3519; (FOV×TTL) / BFL=280.3005.

[0097] The final imaging effect of the lens in this example is achieved through Figure 5 The MTF graph of the lens shows that the MTF curves in each field of view all drop gently and have good consistency. As can be seen from the graph, the MTF value of the edge field of view at a spatial frequency of 60pl / mm is greater than 0.52, which means that the lens has good imaging effect and resolution in the entire field of view. Figure 6 This is the field curvature distortion diagram of the lens of this embodiment. It can be seen that the distortion of the lens does not exceed 3%. Example 3

[0098] In this example, in the optical system, the first lens L1 is a meniscus negative lens with the convex surface facing the object; the second lens L2 is a double concave negative lens; the third lens L3 is a double convex positive lens; the fourth lens L4 is a double convex positive lens; the fifth lens L5 is a double concave negative lens; the sixth lens L6 is a double convex positive lens; the seventh lens L7 is a double convex positive lens; the eighth lens L8 is a double concave negative lens; and the ninth lens L9 is a meniscus positive lens with the convex surface facing the object. The optical path diagram of the monitoring lens is shown in Figure 7 shown.

[0099] See Table 3, which lists the relevant parameters of each lens in this example, including the radius of curvature, thickness, refractive index of the material, and Abbe number:

[0100] Table 3

[0101]

[0102] Infinity means infinity.

[0103] In this example, the air distance from the first lens L1 to the second lens L2 is 10.8198 mm; the air distance from the third lens L3 to the fourth lens L4 is 10.3074 mm; the air distance from the fourth lens L4 to the fifth lens L5 is 0.7113 mm; the air distance from the fifth lens L5 to the aperture C is 6.1896 mm; the air distance from the aperture C to the sixth lens L6 is -0.4385 mm; the air distance from the sixth lens L6 to the seventh lens L7 is 2.6385 mm; the air distance from the eighth lens L8 to the ninth lens L9 is 1.7534 mm; and the air distance from the ninth lens L9 to the image plane IMG is 16.4884 mm.

[0104] The technical indicators achieved by the optical system in this example are as follows:

[0105] 1) Maximum field of view of the surveillance camera: FOV = 55.5000°;

[0106] 2) Effective focal length of the front lens: f u1 =-27.9713mm;

[0107] 3) Effective focal length of the rear lens group: f u2 =18.3801mm;

[0108] 4) Effective focal length of surveillance lens: f=21.97mm;

[0109] 5) Chief ray angle of the optical system: CRA = 16.0141°;

[0110] 6) Maximum image height of the surveillance lens: IH = 11.2370 mm;

[0111] 7) Aperture value of monitoring lens: FNO = 2.1010;

[0112] 8) Monitoring lens head aperture size: D = 26.5764mm;

[0113] 9) The aperture of the largest lens in the surveillance lens: SD max =26.5764mm;

[0114] 10) The distance from the image side of the ninth lens L9 to the image plane IMG in the monitoring lens: BFL = 16.4884 mm;

[0115] 12) Total optical length of the monitoring lens: TTL = 93.9445mm.

[0116] Then we can get: FOV / CRA=3.4657; (FOV×f) / IH=108.5127; |f u1 / f|=1.2731;|f u2 / f|=0.8366; SD max / TTL=0.28; FOV / (D×TTL)=0.0222; IH / FNO=5.3485; (FOV×TTL) / BFL=316.2179.

[0117] The final imaging effect of the lens in this example is achieved through Figure 8-9 To evaluate, from Figure 8 It can be seen that the MTF value of the edge field of view is greater than 0.5 at the spatial frequency of 60pl / mm; Fig. 9 : is the field curvature distortion diagram of the lens of this embodiment, from which it can be seen that the distortion of the lens does not exceed 3%.

[0118] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A small surveillance lens with low distortion, large light transmission, large target surface and high resolution, characterized by: The monitoring lens has nine lenses in total, which include, in order from the object side to the image side along the optical axis: a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, an aperture C, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a ninth lens L9. The first lens L1 is a negative meniscus lens with its convex surface facing the object; The second lens L2 is a double concave negative lens; The third lens L3 is a biconvex positive lens; The fourth lens L4 is a meniscus positive lens or a biconvex positive lens with a convex surface facing the object; The fifth lens L5 is a double concave negative lens; The sixth lens L6 is a biconvex positive lens; The seventh lens L7 is a biconvex positive lens; The eighth lens L8 is a double concave negative lens; The ninth lens L9 is a biconvex positive lens or a meniscus positive lens with the convex surface facing the object; The second lens L2 and the third lens L3 are closely connected to form a first cemented lens group; the seventh lens L7 and the eighth lens L8 are closely connected to form a second cemented lens group; The first lens L1 to the fifth lens L5 constitute a front lens group; the sixth lens L6 to the ninth lens L9 constitute a rear lens group; The monitoring lens meets the following condition: 2.2≤FOV / CRA≤4.171, where FOV is the maximum field of view of the monitoring lens, and CRA is the main ray angle of the monitoring lens. The monitoring lens meets the following condition: |f u1 / f|≤1.3,0.8≤|f u2 / f|≤0.9255, where f u1 is the effective focal length of the front lens group, f u2 is the effective focal length of the rear lens group, and f is the effective focal length of the monitoring lens.

2. According to claim 1, a small surveillance lens with low distortion, large light flux, large target surface and high resolution, characterized in that: The monitoring lens satisfies the following condition: 108.4678≤(FOV×f) / IH≤109, where FOV is the maximum field of view of the monitoring lens, f is the effective focal length of the monitoring lens, and IH is the maximum image plane height of the monitoring lens.

3. The small surveillance lens with low distortion, large light flux, large target surface and high resolution according to claim 1, characterized in that: The surveillance camera meets the following conditions: SD max / TTL≤0.3, where SD max is the clear aperture of the largest lens in the monitoring lens, and TTL is the total optical length of the monitoring lens, that is, the distance from the center of the object side of the first lens L1 to the imaging surface.

4. The small surveillance lens with low distortion, large light flux, large target surface and high resolution according to claim 1, characterized in that: The monitoring lens satisfies the following condition: 0.02≤FOV / (D×TTL)≤0.0237, where FOV is the maximum field of view of the monitoring lens, D is the aperture size of the monitoring lens head, and TTL is the total optical length of the monitoring lens.

5. The small surveillance lens with low distortion, large light flux, large target surface and high resolution according to claim 1, characterized in that: The monitoring lens satisfies the following condition: 5.3≤IH / FNO≤5.3545, where IH is the maximum image plane height of the monitoring lens, and FNO is the aperture value of the monitoring lens.

6. The small surveillance lens with low distortion, large light flux, large target surface and high resolution according to claim 1, characterized in that: The monitoring lens satisfies the following condition: 260≤(FOV×TTL) / BFL≤316.2179, where FOV is the maximum field of view of the monitoring lens, TTL is the total optical length of the monitoring lens, and BFL is the distance from the image side surface of the ninth lens L9 in the monitoring lens to the image plane IMG.

7. The small surveillance lens with low distortion, large light flux, large target surface and high resolution according to claim 1, characterized in that: The eleventh lens L11 satisfies the following conditions: N d9 ≤1.8;V D9 ≥44, where N d9 is the refractive index of the ninth lens L9, V D9 is the Abbe number of the ninth lens L9.

Images