A wide-angle, large-aperture, fixed-focus lens

Abstract

The present invention relates to a wide-angle, large-aperture, fixed-focus lens, which is provided with a lens group, wherein the lens group includes a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with negative focal power, a fifth lens with positive focal power, a sixth lens with positive focal power, a seventh lens with positive focal power, an eighth lens with negative focal power, and a ninth lens with positive focal power, which are sequentially arranged along the optical axis from the object side to the image side. The invention overcomes the disadvantage of the existing wide-angle, large-aperture, fixed-focus lens matching a 1 / 1.8" image plane chip, that the volume is large (the total optical length is long). By adopting the combination of nine lenses with optimal optical conditions, the total optical length is short, and the day and night confocality and high and low temperature drift compensation functions are realized.

Description

Technical Field

[0001] The invention relates to a wide-angle, large-aperture, fixed-focus lens, and is particularly applicable to the field of security high-definition monitoring. Background Art

[0002] Currently, most of the fixed-focus security monitoring lenses on the market have two or three million pixels, and their aperture values ​​are generally greater than F2.0, matching imaging chips with 1 / 2.7” image planes. Although they can meet the monitoring needs of general occasions, they are not competent for low-light and ultra-high-definition usage scenarios. In recent years, high-resolution imaging chips with 1 / 1.8” image planes have gradually become popular, and their prices have gradually been accepted by the market. Although there are wide-angle, large-aperture CS-interface products or M12-interface lenses matching such chips on the market, the total optical length of such lenses is generally more than 30mm, and it is still difficult to find wide-angle, large-aperture, high-definition lenses that match such chips and have a short total optical length. Therefore, it has become an urgent task to provide a wide-angle, large-aperture fixed-focus lens that matches a 1 / 1.8” image plane chip and is compact (short total optical length). Summary of the invention

[0003] In order to overcome the disadvantage of large size (long optical length) of the existing wide-angle, large aperture, fixed-focus lens matched with a 1 / 1.8" image plane chip, the present invention provides a wide-angle, large aperture, fixed-focus lens, which has the advantages of wide-angle, large aperture and small size (short optical length) by adopting a matching design of nine lenses with optimal optical conditions.

[0004] The technical solution of the present invention is as follows:

[0005] A wide-angle, large-aperture, fixed-focus lens having a lens group therein, the lens group comprising a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with negative focal power, a fifth lens with positive focal power, a sixth lens with positive focal power, a seventh lens with positive focal power, an eighth lens with negative focal power, and a ninth lens with positive focal power, which are sequentially arranged along the optical axis from the object side to the image side; wherein the fourth lens and the fifth lens, and the seventh lens and the eighth lens are respectively cemented lenses;

[0006] The first lens is a meniscus lens with one convex and one concave, the second lens is an aspheric lens with one concave and one convex or a biconcave shape, the third lens is a biconvex lens, the fourth lens is a biconcave lens, the fifth lens is a biconvex lens, the sixth lens is a biconvex lens, the seventh lens is a biconvex lens, the eighth lens is a biconcave lens, and the ninth lens is a biconvex aspheric lens;

[0007] And each lens satisfies the following optical conditions:

[0008] 1.72 <n1<1.98,28.1<v1<46.8;

[0009] 1.47 <n2<1.66,50.6<v2<60.5;

[0010] 1.71 <n3<1.92,28.3<v3<49.7;

[0011] 1.48 <n4<1.63,48.5<v4<70.7;

[0012] 1.80 <n5<2.05,25.3<v5<48.0;

[0013] 1.49 <n6<1.84,52.2<v6<81.8;

[0014] 1.49 <n7<1.71,63.3<v7<81.8;

[0015] 1.75 <n8<2.00,17.5<v8<35.9;

[0016] 1.48 <n9<1.68,50.6<v9<60.5;

[0017] Wherein n1-n9 are the refractive indices of the first lens to the ninth lens, and v1-v9 are the Abbe coefficients of the first lens to the ninth lens.

[0018] The wide-angle large aperture fixed focus lens of the present application combines the above nine lenses and optimizes the parameters such as the positive and negative optical power distribution, the cementing state, the refractive index, the Abbe coefficient and the lens shape. On the basis of having wide-angle and large aperture characteristics, it can match the image plane chip of 1 / 1.8” chip. At the same time, it has a compact structure, controls the total optical length within 25mm, and can match the M12 interface in structure. It is used for miniaturized cameras, effectively reducing the overall volume of the lens. The main optical indicators of the lens are as follows: aperture value F=1.6, diagonal field of view 2ω=154°, the ratio of total optical length to focal length TTL / f is less than 6.9, the working spectrum is in the visible light and near-infrared band of 420nm-850nm, and the resolution reaches 5MP pixel high definition.

[0019] Among them, the first lens and the second lens are both negative optical power lenses, whose function is to reduce the incident angle of light to achieve a wide-angle effect. At the same time, the second lens is an aspherical lens to reduce the optical distortion of the system; the third lens is made of high refractive index material and reasonably distributes the optical power so that the optical power shared by the sixth lens is not too large. The fourth lens and the fifth lens are cemented components, which are paired by crown and flint glass to reduce the chromatic aberration of the system. The seventh lens uses ultra-low dispersion glass and is bonded with the eighth lens to reduce the axial chromatic aberration of the system and realize the day and night confocal function of visible light and infrared light. The ninth lens is an aspherical lens, which is used to correct field curvature to make the clarity of the center and edge areas of the image plane more consistent. And the use of two aspherical lenses reduces the total optical length of the overall system.

[0020] The focal length of each lens satisfies the following optical conditions:

[0021] 1.0<|f1 / f|<2.25;

[0022] 1.65<|f6 / f|<3.8;

[0023] 1.6<|f9 / f|<4.5;

[0024] Among them, f1 is the focal length of the first lens, f6 is the focal length of the sixth lens, f9 is the focal length of the ninth lens, and f is the total focal length of the wide-angle large aperture fixed-focus lens.

[0025] The optimal focal length condition makes the imaging effect of the wide-angle, large-aperture fixed-focus lens better.

[0026] The second lens and the ninth lens are both plastic lenses. The mixed use of glass lenses and plastic aspherical lenses can make the overall system small in size, light in weight and low in cost. At the same time, the compensation design is based on the different temperature characteristics of plastic lenses and glass lenses, which can achieve focus temperature drift correction at -30℃-70℃.

[0027] The first lens and the second lens, the third lens and the fourth lens are directly mounted close to each other, and the second lens and the third lens, the fifth lens and the sixth lens, the sixth lens and the seventh lens, and the eighth lens and the ninth lens are all mounted close to each other through a spacer.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1) The wide-angle, large-aperture, fixed-focus lens of the present application has a large aperture of F1.6, which is better than most F2.0 products on the market, and can have better imaging performance in low-light environments; the field of view is large, and the diagonal field of view angle reaches 154°, which can monitor a wider area;

[0030] 2) On the basis of having wide-angle and large aperture characteristics, it can match the image plane chip of 1 / 1.8” chip, and at the same time, it has a compact structure, controlling the total optical length within 25mm. The structure can match the M12 interface and be used in miniaturized cameras;

[0031] 3) The compensation design uses the different temperature characteristics of plastic lenses and glass lenses to achieve focus temperature drift correction at -30℃-70℃, so that the lens can adapt to complex temperature environments and can be used under different environmental conditions, which has broad market value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The optical system structure of the wide-angle, large-aperture, fixed-focus lens of the present invention is shown in FIG. Figure 1 ;

[0033] Figure 2 The optical system structure of the wide-angle, large-aperture, fixed-focus lens of the present invention is shown in FIG. Figure 2 ;

[0034] Figure 3 It is the MTF transfer function curve diagram of the wide-angle, large-aperture, fixed-focus lens of the present invention;

[0035] Figure 4 It is a field curvature distortion diagram of the wide-angle, large-aperture, fixed-focus lens of the present invention;

[0036] Figure 5 It is a light fan diagram of the wide-angle, large-aperture, fixed-focus lens of the present invention;

[0037] Figure 6 It is an infrared light MTF transfer function curve diagram of the wide-angle, large-aperture, fixed-focus lens of the present invention;

[0038] Figure 7 It is the MTF transfer function curve diagram of the wide-angle, large-aperture, fixed-focus lens of the present invention at -30°C;

[0039] Figure 8 It is an MTF transfer function curve diagram of the wide-angle, large-aperture, fixed-focus lens of the present invention at 70°C.

[0040] Description of labels:

[0041] A first lens 1 , a second lens 2 , a third lens 3 , a fourth lens 4 , a fifth lens 5 , a sixth lens 6 , a seventh lens 7 , an eighth lens 8 , a ninth lens 9 , and a flat protective glass 10 . DETAILED DESCRIPTION

[0042] The following is attached to the instruction manual Figure 1-8 The technical solution of the present invention is described in detail.

[0043] like Figure 1-2As shown, a wide-angle and large-aperture fixed-focus lens according to the present invention is provided with a lens group therein, wherein the lens group comprises a first lens 1 with negative optical power, a second lens 2 with negative optical power, a third lens 3 with positive optical power, a fourth lens 4 with negative optical power, a fifth lens 5 with positive optical power, a sixth lens 6 with positive optical power, a seventh lens 7 with positive optical power, an eighth lens 8 with negative optical power, and a ninth lens 9 with positive optical power, which are sequentially arranged along the optical axis direction from the object side to the image side; wherein the fourth lens 4 and the fifth lens 5, and the seventh lens 7 and the eighth lens 8 are all cemented lenses;

[0044] The first lens is a meniscus lens with one convex and one concave, the second lens is an aspheric lens with one concave and one convex or a biconcave shape, the third lens is a biconvex lens, the fourth lens is a biconcave lens, the fifth lens is a biconvex lens, the sixth lens is a biconvex lens, the seventh lens is a biconvex lens, the eighth lens is a biconcave lens, and the ninth lens is a biconvex aspheric lens;

[0045] And each lens satisfies the following optical conditions:

[0046] 1.72 <n1<1.98,28.1<v1<46.8;

[0047] 1.47 <n2<1.66,50.6<v2<60.5;

[0048] 1.71 <n3<1.92,28.3<v3<49.7;

[0049] 1.48 <n4<1.63,48.5<v4<70.7;

[0050] 1.80 <n5<2.05,25.3<v5<48.0;

[0051] 1.49 <n6<1.84,52.2<v6<81.8;

[0052] 1.49 <n7<1.71,63.3<v7<81.8;

[0053] 1.75 <n8<2.00,17.5<v8<35.9;

[0054] 1.48 <n9<1.68,50.6<v9<60.5;

[0055] Wherein n1-n9 are the refractive indices of the first lens 1 to the ninth lens 9, and v1-v9 are the Abbe coefficients of the first lens 1 to the ninth lens 9.

[0056] The focal length of each lens satisfies the following optical conditions:

[0057] 1.0<|f1 / f|<2.25;

[0058] 1.65<|f6 / f|<3.8;

[0059] 1.6<|f9 / f|<4.5;

[0060] Wherein, f1 is the focal length of the first lens 1, f6 is the focal length of the sixth lens 6, f9 is the focal length of the ninth lens 9, and f is the total focal length of the wide-angle, large-aperture, fixed-focus lens.

[0061] The second lens 2 and the ninth lens 9 are both plastic lenses.

[0062] The first lens 1 and the second lens 2, the third lens 3 and the fourth lens 4 are directly mounted close to each other, the second lens 2 and the third lens 3, the fifth lens 5 and the sixth lens 6, the sixth lens 6 and the seventh lens 7, the eighth lens 8 and the ninth lens 9 are all mounted close to each other via spacers.

[0063] Here is a list of relevant information about the above lenses:

[0064] Face number S R d n 1 14.81 0.7 1.84 2 3.58 2.80 3 -6.09 1.3 1.54 4 -75.18 0.21 5 17.44 2.12 1.84 6 -9.78 0.29 7 -5.53 0.72 1.49 8 28.68 3.08 1.90 9 -13.90 0.1 10 11.0 1.91 1.59 11 -11.0 0.1 12 8.85 1.87 1.59 13 -5.65 0.72 1.85 14 7.01 1.41 15 8.17 2.38 1.54 16 -9.03 3.9 17 Infinity 0.75 1.52 18 Infinity

[0065] Table 1 Relevant optical data

[0066] Wherein, R represents the curvature radius of the corresponding mirror surface, d represents the center thickness or air space of the corresponding lens, and n represents the refractive index of the corresponding lens. The 17th and 18th surfaces are the flat protective glass 10 behind the lens.

[0067] Face number S k A B C D E 3 -8.7 -3.52E-003 3.4E-004 -2.64E-005 9.50E-007 5.33E-020 4 0 9.2E-004 2.74E-005 -1.01E-005 6.33E-007 -4.26E-019 15 3.17 -2.12E-003 1.04E-004 -1.85E-005 1.43E-006 -5.96E-008 16 -1.70 -2.62E-004 2.41E-005 -2.91E-006 3.09E-007 -1.29E-008

[0068] Table 2 Aspheric surface related parameters of the second lens L2 and the ninth lens L9

[0069] The second lens and the ninth lens are both aspherical lenses, and their surface shapes conform to the following formula:

[0070]

[0071] Among them, c = 1 / R, R represents the vertex curvature radius of the aspheric surface center, r represents the radial coordinate value of the lens based on the optical axis, z represents the vector height corresponding to the radial coordinate r of the lens, k represents the cone coefficient, and A, B, C, D, and E represent the aspheric coefficients of each order respectively.

[0072] Attached Figure 3-8 Description:

[0073] Attached Figure 3This is the visible light MTF transfer function curve of the wide-angle, large-aperture, fixed-focus lens of the present application. At an ambient temperature of 20°C, at a spatial frequency of 200lp / mm, the central field of view is higher than 0.4, and the 0.7 field of view is higher than 0.3, corresponding to a chip with a 1 / 1.8” image plane, and a resolution of more than 5 million pixels;

[0074] Attached Figure 4 This is the field curvature distortion diagram of the wide-angle, large-aperture, fixed-focus lens of the present application. From the diagram, it can be seen that the field curvature is controlled within 0.05mm and the optical distortion is within 70%, which is an acceptable level for a wide-angle lens. Figure 5 The light fan diagram shows that the vertical chromatic aberration of the maximum field of view of the wide-angle, large-aperture, fixed-focus lens of the present application is controlled within 8μm, and no obvious color fringing will be produced;

[0075] Attached Figure 6 This is the 850nm infrared light MTF transfer function curve of the wide-angle, large-aperture fixed-focus lens of this application. At the spatial frequency of 120lp / mm, the central field of view is higher than 0.6, and the field of view of 0.7 is higher than 0.3. The full field of view resolution of the chip corresponding to the 1 / 1.8” image plane is higher than 2 million pixels, which meets the needs of nighttime confocal imaging.

[0076] Attached Figure 7 and attached Figure 8 They are the visible light MTF transfer function curves of the wide-angle and large-aperture fixed-focus lens of the present application at -30°C and 70°C, and are compared with the attached Figure 3 It can be seen that at a spatial frequency of 200lp / mm, the central field of view values ​​are still higher than 0.4, and the 0.7 field of view is only slightly lower than 0.3 at 70°C. The overall MTF curve does not show a significant decrease, that is, the resolution of this patent can still be maintained above 5 million pixels in high and low temperature environments.

[0077] The wide-angle, large-aperture, fixed-focus lens described in the present invention is not limited to the above-mentioned embodiments, and any improvement or replacement based on the principle of the present invention should be within the protection scope of the present invention.

Claims

1. A wide-angle, large-aperture, fixed-focus lens, characterized by: A lens group is provided therein, the lens group comprising a first lens (1) with negative focal power, a second lens (2) with negative focal power, a third lens (3) with positive focal power, a fourth lens (4) with negative focal power, a fifth lens (5) with positive focal power, a sixth lens (6) with positive focal power, a seventh lens (7) with positive focal power, an eighth lens (8) with negative focal power, and a ninth lens (9) with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis; wherein the fourth lens (4) and the fifth lens (5), and the seventh lens (7) and the eighth lens (8) are all cemented lenses; The first lens is a meniscus lens with one convex and one concave, the second lens is an aspheric lens with one concave and one convex or a biconcave shape, the third lens is a biconvex lens, the fourth lens is a biconcave lens, the fifth lens is a biconvex lens, the sixth lens is a biconvex lens, the seventh lens is a biconvex lens, the eighth lens is a biconcave lens, and the ninth lens is a biconvex aspheric lens; And each lens satisfies the following optical conditions: 1.72 <n1<1.98,28.1<v1<46.8; 1.47 <n2<1.66,50.6<v2<60.5; 1.71 <n3<1.92,28.3<v3<49.7; 1.48 <n4<1.63,48.5<v4<70.7; 1.80 <n5<2.05,25.3<v5<48.0; 1.49 <n6<1.84,52.2<v6<81.8; 1.49 <n7<1.71,63.3<v7<81.8; 1.75 <n8<2.00,17.5<v8<35.9; 1.48 <n9<1.68,50.6<v9<60.5; Wherein n1-n9 are the refractive indices of the first lens (1) to the ninth lens (9), and v1-v9 are the Abbe coefficients of the first lens (1) to the ninth lens (9).

2. The wide-angle, large-aperture, fixed-focus lens according to claim 1, characterized in that: The focal length of each lens satisfies the following optical conditions: 1.0<|f1 / f|<2.25; 1.65<|f6 / f|<3.8; 1.6<|f9 / f|<4.5; Wherein, f1 is the focal length of the first lens (1), f6 is the focal length of the sixth lens (6), f9 is the focal length of the ninth lens (9), and f is the total focal length of the wide-angle, large-aperture, fixed-focus lens.

3. The wide-angle, large-aperture, fixed-focus lens according to claim 1, characterized in that: The second lens (2) and the ninth lens (9) are both plastic lenses.

4. The wide-angle, large-aperture, fixed-focus lens according to claim 1, characterized in that: The first lens (1) and the second lens (2), the third lens (3) and the fourth lens (4) are directly mounted close to each other, and the second lens (2) and the third lens (3), the fifth lens (5) and the sixth lens (6), the sixth lens (6) and the seventh lens (7), and the eighth lens (8) and the ninth lens (9) are mounted close to each other via spacers.

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