Wide-angle monitoring lens

Abstract

The utility model relates to a wide-angle monitoring lens which is composed of a first lens, a diaphragm, a second lens, a third lens and a fourth lens which are sequentially arranged along the incident direction of light, the first lens has negative focal power, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; the second lens has positive focal power, and the object side surface and the image side surface of the second lens are convex surfaces; the third lens has positive focal power, and the object side surface and the image side surface of the third lens are convex surfaces; and the fourth lens has negative focal power, the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface. The lens has good imaging performance, large aperture and small defocusing amount of short-wave infrared light, so that the lens has clear imaging pictures at night, and the day and night confocal performance is realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to a wide-angle monitoring lens. BACKGROUND

[0002] With the rapid development of security monitoring system in the world, the market scale of security lens is expanding, wherein the wide-angle monitoring lens occupies an important position in the security lens market due to its unique advantages, and the market competition is increasingly fierce. The price of the current wide-angle lens product is continuously reduced, but the quality requirement of the lens is continuously improved. Therefore, developing the lens with high imaging quality and lower cost is the development trend of the future security monitoring market. SUMMARY

[0003] In view of the deficiencies of the prior art, the utility model provides a wide-angle monitoring lens, which has the advantages of low cost, large aperture, large field of view, high resolution, day and night confocal and athermalization function.

[0004] The utility model solves the technical problem by adopting the following scheme: a wide-angle monitoring lens: the lens is composed of a first lens, a diaphragm, a second lens, a third lens and a fourth lens arranged in sequence along the light incident direction, the first lens has negative focal power, the object side surface is a convex surface, and the image side surface is a concave surface; the second lens has positive focal power, and the object side surface and the image side surface are both convex surfaces; the third lens has positive focal power, and the object side surface and the image side surface are both convex surfaces; the fourth lens has negative focal power, the object side surface is a concave surface, and the image side surface is a convex surface.

[0005] Further, the second lens is a glass spherical lens, the first lens, the third lens and the fourth lens are plastic aspherical lenses, and the aspherical curve equation expression of the first lens, the third lens and the fourth lens is as follows:

[0006]

[0007] Wherein, Z is the sagittal height of the aspherical surface from the aspherical surface vertex when the aspherical surface is in the position with the height of h along the optical axis direction; c is the paraxial curvature of the aspherical surface; k is the conic constant; 、 、 、 、 、 、 、 All are high-order coefficients.

[0008] Further, the lens satisfies the relationship: 7.5 ≤ (G1+G2) / T4, 0.7 ≤ (T1+T4) / T2, 1.6 ≤ (G1+G2) / T2; where G1 is the distance on the optical axis between the image side surface of the first lens and the object side surface of the second lens, G2 is the distance on the optical axis between the image side surface of the second lens and the object side surface of the first lens counted sequentially from the image side of the second lens, T1 is the thickness on the optical axis of the first lens, T2 is the thickness on the optical axis of the second lens, and T4 is the thickness on the optical axis of the fourth lens.

[0009] Further, the lens satisfies the relationship: TTL / (G1+G2) ≤ 3.2, 4.2 ≤ TTL / (T2+T4), 3.2 ≤ TTL / (G1+T4); where TTL is the thickness on the optical axis from the object side surface of the first lens to the imaging surface of the lens, G1 is the distance on the optical axis between the image side surface of the first lens and the object side surface of the second lens, G2 is the distance on the optical axis between the image side surface of the second lens and the object side surface of the first lens counted sequentially from the image side of the second lens, T2 is the thickness on the optical axis of the second lens, and T4 is the thickness on the optical axis of the fourth lens.

[0010] Further, the lens satisfies the relationship: 7.6 ≤ AAG / T4, 1.0 ≤ AAG / (T1+T2), 2.1 ≤ AAG / (T1+G2); where AAG is the sum of the air gaps on the optical axis between the first lens and the fourth lens, T1 is the thickness on the optical axis of the first lens, T2 is the thickness on the optical axis of the second lens, T4 is the thickness on the optical axis of the fourth lens, and G2 is the distance on the optical axis between the image side surface of the second lens and the object side surface of the first lens counted sequentially from the image side of the second lens.

[0011] Further, the lens satisfies the relationship: BFL / (T2+G1) ≤ 0.5, BFL / T1 ≤ 2.2, BFL / G2 ≤ 4.1, where BFL is the distance on the optical axis between the image side surface of the fourth lens and the imaging surface of the optical lens, T1 is the thickness on the optical axis of the first lens, T2 is the thickness on the optical axis of the second lens, G1 is the distance on the optical axis between the image side surface of the first lens and the object side surface of the second lens, and G2 is the distance on the optical axis between the image side surface of the second lens and the object side surface of the first lens counted sequentially from the image side of the second lens.

[0012] Further, the lens satisfies the relationship: ALT / G2≤8.9, ALT / (T1+G2)≤3.1, ALT / (T2+G2)≤2.0; wherein ALT is the sum of the central thicknesses of all lenses between the object side and the image side of the lens on the optical axis, T1 is the thickness of the first lens on the optical axis, T2 is the thickness of the second lens on the optical axis, and G2 is the distance on the optical axis between the image side of the second lens and the object side of the first lens sequentially calculated from the second lens towards the image side.

[0013] Further, the lens satisfies the relationship: TL / T1≤7.9, TL / G1≤2.9, TL / (T1+T4)≤5.7, TL / (T1+G1)≤2.2, TL / (T4+G1)≤2.6; wherein TL is the distance on the optical axis between the object side of the first lens and the image side of the fourth lens, T1 is the thickness of the first lens on the optical axis, T4 is the thickness of the fourth lens on the optical axis, and G1 is the distance on the optical axis between the image side of the first lens and the object side of the second lens.

[0014] Further, the lens satisfies the relationship: TTL / EFL≤5.1, IMH / EFL≥1.5; wherein EFL is the effective focal length of the lens, TTL is the distance on the optical axis between the object side of the first lens and the imaging surface of the lens, and IMH is the image height of the optical lens.

[0015] Further, the lens satisfies: focal length: 4.0≤EFFL≤4.5mm; aperture F≤1.65; field of view angle: 2w≥120°; relative luminance: RI≥43%.

[0016] Compared with the prior art, the utility model has the advantages that: the utility model is composed of one glass spherical lens and three plastic aspherical lenses, the shape of the three plastic aspherical lenses is adjusted, the image aberration in the optical system is corrected, the wide-angle lens has good imaging performance, has a large aperture and a small defocus amount of short-wave infrared light, has a clear imaging picture at night, realizes day and night focusing performance, four lenses are made of materials with a negative refractive index temperature coefficient, the defocus amount of the image surface caused by temperature change is minimum, has a non-thermal function, can ensure high-definition imaging in-30 DEG C to 80 DEG C environment, and the cost is lower than other similar lenses on the market. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the optical structure schematic diagram of the utility model embodiment;

[0018] Figure 2 is the axial chromatic aberration curve drawing of the utility model embodiment;

[0019] Figure 3 is a vertical axis chromatic aberration curve diagram of the embodiment of the utility model;

[0020] Figure 4 is a field curvature distortion curve diagram of the embodiment of the utility model;

[0021] Figure 5 is the off-focus MTF curve diagram of the embodiment of the utility model under the visible light band in normal temperature state;

[0022] Figure 6 is the off-focus MTF curve diagram of the embodiment of the utility model under the 850nm infrared wave band in normal temperature state;

[0023] Figure 7 is the off-focus MTF curve diagram of the embodiment of the utility model under the visible light band in low temperature-40 DEG C state;

[0024] Figure 8 is the off-focus MTF curve diagram of the embodiment of the utility model under the visible light band in high temperature 80 DEG C state;

[0025] In the drawing: STO - diaphragm;L1 - first lens;L2 - second lens;L3 - third lens;L4 - fourth lens;L5 - equivalent glass flat plate;IMA - imaging surface. DETAILED DESCRIPTION

[0026] The utility model is further explained below in combination with the drawings and specific embodiments.

[0027] As Figure 1 shown, a wide-angle monitoring lens: the lens is by first lens, diaphragm, second lens, third lens and fourth lens are set gradually in the light incident direction, the first lens has negative focal power, its object side is convex, and the image side is concave;Second lens has positive focal power, and its object side and image side are both convex;Third lens has positive focal power, and its object side is and the image side is both convex;Fourth lens has negative focal power, and its object side is concave, and the image side is convex.

[0028] In the embodiment, the second lens is a glass spherical lens, and the first lens, the third lens and the fourth lens are plastic aspheric lenses, and the aspheric curve equation expression of the first lens, the third lens and the fourth lens is as follows:

[0029]

[0030] Wherein, Z is the off-axis height of aspheric surface at the height h along the optical axis direction, and c is the near-axis curvature of aspheric surface;K is the conic constant; 、 、 , are coefficients of high order terms.

[0031] The aspherical coefficients of the aspherical lenses of the optical system of this embodiment are as follows:

[0032]

[0033] In this embodiment, the lens satisfies the following relationships: 7.5 ≤ (G1+G2) / T4, 0.7 ≤ (T1+T4) / T2, 1.6 ≤ (G1+G2) / T2; where G1 is the distance on the optical axis between the image side surface of the first lens and the object side surface of the second lens, G2 is the distance on the optical axis between the image side surface of the second lens and the object side surface of the first lens counted sequentially from the image side of the second lens, T1 is the thickness on the optical axis of the first lens, T2 is the thickness on the optical axis of the second lens, and T4 is the thickness on the optical axis of the fourth lens.

[0034] In this embodiment, the lens satisfies the following relationships: TTL / (G1+G2) ≤ 3.2, 4.2 ≤ TTL / (T2+T4), 3.2 ≤ TTL / (G1+T4); where TTL is the thickness on the optical axis from the object side surface of the first lens to the imaging surface of the lens, G1 is the distance on the optical axis between the image side surface of the first lens and the object side surface of the second lens, G2 is the distance on the optical axis between the image side surface of the second lens and the object side surface of the first lens counted sequentially from the image side of the second lens, T2 is the thickness on the optical axis of the second lens, and T4 is the thickness on the optical axis of the fourth lens.

[0035] In this embodiment, the lens satisfies the following relationships: 7.6 ≤ AAG / T4, 1.0 ≤ AAG / (T1+T2), 2.1 ≤ AAG / (T1+G2); where AAG is the sum of the air gaps on the optical axis between the first lens and the fourth lens, T1 is the thickness on the optical axis of the first lens, T2 is the thickness on the optical axis of the second lens, T4 is the thickness on the optical axis of the fourth lens, and G2 is the distance on the optical axis between the image side surface of the second lens and the object side surface of the first lens counted sequentially from the image side of the second lens.

[0036] ​​​​In the embodiment, the lens satisfies the relationship: BFL / (T2+G1)≤0.5, BFL / T1≤2.2, BFL / G2≤4.1, wherein BFL is the distance between the image side surface of the fourth lens and the imaging surface of the optical lens on the optical axis, T1 is the thickness of the first lens on the optical axis, T2 is the thickness of the second lens on the optical axis, G1 is the distance between the image side surface of the first lens and the object side surface of the second lens on the optical axis, and G2 is the distance between the image side surface of the second lens and the object side surface of the first lens sequentially calculated from the image side of the second lens on the optical axis.

[0037] In the embodiment, the lens satisfies the relationship: ALT / G2≤8.9, ALT / (T1+G2)≤3.1, ALT / (T2+G2)≤2.0; wherein ALT is the sum of the central thicknesses of all lenses between the object side and the image side of the lens on the optical axis, T1 is the thickness of the first lens on the optical axis, T2 is the thickness of the second lens on the optical axis, and G2 is the distance between the image side surface of the second lens and the object side surface of the first lens sequentially calculated from the image side of the second lens on the optical axis.

[0038] In the embodiment, the lens satisfies the relationship: TL / T1≤7.9, TL / G1≤2.9, TL / (T1+T4)≤5.7, TL / (T1+G1)≤2.2, TL / (T4+G1)≤2.6; wherein TL is the distance between the object side surface of the first lens and the image side surface of the fourth lens on the optical axis, T1 is the thickness of the first lens on the optical axis, T4 is the thickness of the fourth lens on the optical axis, and G1 is the distance between the image side surface of the first lens and the object side surface of the second lens on the optical axis.

[0039] In the embodiment, the lens satisfies the relationship: TTL / EFL≤5.1, IMH / EFL≥1.5; wherein EFL is the effective focal length of the lens, TTL is the distance between the object side surface of the first lens and the imaging surface of the lens on the optical axis, and IMH is the image height of the optical lens.

[0040] In the embodiment, the optical imaging lens further satisfies: dn / dt<0 of the first lens, the second lens, the third lens and the fourth lens, wherein dn / dt represents the coefficient of change of refractive index with temperature.

[0041] In the embodiment of the utility model, the technical index realized by the optical system is as follows:

[0042] (1) focal length: 4.0≤EFFL≤4.5mm;

[0043] (2) aperture F≤1.65;

[0044] (3) Field of view: 2w>=120°;

[0045] (4) Relative luminance: RI>=43%;

[0046] (5) Working waveband: visible light waveband and short wave infrared light waveband;

[0047] (6) Working temperature: -30℃~80℃.

[0048] To realize the above design parameters, the specific design of the optical system of the embodiment is shown in the following table:

[0049]

[0050] In the embodiment, the rear side of the fourth lens of the lens is provided with a filter.

[0051] A working method of the wide-angle monitoring lens: when light is incident, the light path sequentially enters the first lens, the diaphragm, the second lens, the third lens, the fourth lens, and finally forms an image on the image plane.

[0052] In summary, the wide-angle monitoring optical system with a large aperture and non-thermalization provided by the utility model has a large aperture, a large field of view, day and night focusing functions, high resolving power, a large light aperture, high relative luminance, and a bright and clear imaging picture; meanwhile, the glass-plastic hybrid structure is adopted, the cost is low, the temperature drift is low, high-definition imaging can be ensured under the environment of -30℃ to 80℃, and the imaging effect is shown in Figures 2-8 .

[0053] Unless otherwise stated, if the numerical range is disclosed in the above-mentioned any technical solution of the utility model, the disclosed numerical range is a preferred numerical range, and any person skilled in the art should understand that the preferred numerical range is only one of the many implementable values with more obvious technical effects or representative values. Since there are too many values, it is impossible to enumerate them, therefore, the utility model only discloses part of the values to illustrate the technical solutions of the utility model, and the above-mentioned enumerated values should not constitute a limitation on the protection scope of the utility model.

[0054] If the words "first", "second", etc. are used to limit the parts in this paper, the person skilled in the art should know that: the use of "first", "second" is only for the convenience of describing the parts to be distinguished, and the above-mentioned words have no special meaning unless otherwise stated.

[0055] If the utility model discloses or involves mutually fixed connecting parts or structural members, then, except for another declaration, fixed connection can be understood as: detachable fixed connection (for example, using bolt or screw connection), and also can be understood as: non-detachable fixed connection (for example, riveting, welding), of course, the mutually fixed connection can also be replaced by integral structure (for example, integrally formed by using casting process) (except for obviously unable to adopt integral forming process).

[0056] In addition, the position relationship represented by the above-mentioned any technical solution of the utility model disclosed herein, such as "vertical", "horizontal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like, is the position or position relationship shown in the drawings, which is only for the convenience of describing the patent and does not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the patent, and the shape represented by the above-mentioned any technical solution of the utility model disclosed herein includes shapes similar, similar or close to the shape, except for another declaration.

[0057] Any component provided by the utility model can be assembled from a plurality of separate components, or can be a separate component manufactured by integral forming process.

[0058] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the utility model and not to limit them; although the utility model has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the specific embodiments of the utility model can still be modified or some technical features can be replaced by equivalents; without departing from the spirit of the technical solutions of the utility model, they should all be covered in the technical solution range of the utility model claimed.

Claims

1. A wide-angle surveillance lens characterized by: The lens is composed of a first lens, an aperture, a second lens, a third lens and a fourth lens arranged in sequence along the light incident direction, the first lens has negative focal length, the object side is convex, and the image side is concave; the second lens has positive focal length, the object side and the image side are both convex; the third lens has positive focal length, the object side and the image side are both convex; and the fourth lens has negative focal length, the object side is concave, and the image side is convex. The lens satisfies the relationship: 7.5≤(G1+G2) / T4, 0.7≤(T1+T4) / T2, 1.6≤(G1+G2) / T2; wherein G1 is the distance between the image side of the first lens and the object side of the second lens on the optical axis, G2 is the distance between the image side of the second lens and the object side of the first lens sequentially calculated from the second lens towards the image side on the optical axis, T1 is the thickness of the first lens on the optical axis, T2 is the thickness of the second lens on the optical axis, and T4 is the thickness of the fourth lens on the optical axis.

2. The wide-coverage surveillance lens according to claim 1, characterized in that: The second lens is a glass spherical lens, the first lens, the third lens and the fourth lens are plastic aspherical lenses, and the aspherical curve equation expression of the first lens, the third lens and the fourth lens is: Wherein, Z is the sagitta height of the aspherical surface at a height of h from the vertex of the aspherical surface along the optical axis direction; c is the paraxial curvature of the aspherical surface; k is the conic constant; α1, α2, α3, α4, α5, α6, α7, α8 are high-order coefficients.

3. The wide- monitoring lens according to claim 1, characterized in that: The lens satisfies the relationship: TTL / (G1+G2)≤3.2, 4.2≤TTL / (T2+T4), 3.2≤TTL / (G1+T4); Wherein TTL is the thickness of the object side of the first lens to the imaging surface of the lens on the optical axis, G1 is the distance between the image side of the first lens and the object side of the second lens on the optical axis, G2 is the distance between the image side of the second lens and the object side of the first lens sequentially calculated from the second lens towards the image side on the optical axis, T2 is the thickness of the second lens on the optical axis, and T4 is the thickness of the fourth lens on the optical axis.

4. The wide- monitoring lens according to claim 1, characterized in that: The lens satisfies the relationship: 7.6≤AAG / T4, 1.0≤AAG / (T1+T2), 2.1≤AAG / (T1+G2); wherein AAG is the sum of the air gaps between the first lens and the fourth lens on the optical axis, T1 is the thickness of the first lens on the optical axis, T2 is the thickness of the second lens on the optical axis, T4 is the thickness of the fourth lens on the optical axis, and G2 is the distance between the image side of the second lens and the object side of the first lens sequentially calculated from the second lens towards the image side on the optical axis.

5. The wide- monitoring lens according to claim 1, characterized in that: The lens satisfies the relationship: BFL / (T2+G1)≤0.5, BFL / T1≤2.2, BFL / G2≤4.1, wherein BFL is the distance between the image side surface of the fourth lens and the imaging surface of the lens on the optical axis, T1 is the thickness of the first lens on the optical axis, T2 is the thickness of the second lens on the optical axis, G1 is the distance between the image side surface of the first lens and the object side surface of the second lens on the optical axis, and G2 is the distance between the image side surface of the second lens and the object side surface of the first lens counted sequentially from the image side of the second lens on the optical axis.

6. The wide- monitoring lens according to claim 1, characterized in that: The lens satisfies the relationship: ALT / G2≤8.9, ALT / (T1+G2)≤3.1, ALT / (T2+G2)≤2.0; wherein ALT is the sum of the central thicknesses of all lenses between the object side and the image side of the lens on the optical axis, T1 is the thickness of the first lens on the optical axis, T2 is the thickness of the second lens on the optical axis, and G2 is the distance between the image side surface of the second lens and the object side surface of the first lens counted sequentially from the image side of the second lens on the optical axis.

7. The wide- monitoring lens according to claim 1, characterized in that: The lens satisfies the relationship: TL / T1≤7.9, TL / G1≤2.9, TL / (T1+T4)≤5.7, TL / (T1+G1)≤2.2, TL / (T4+G1)≤2.6; wherein TL is the distance between the object side surface of the first lens and the image side surface of the fourth lens on the optical axis, T1 is the thickness of the first lens on the optical axis, T4 is the thickness of the fourth lens on the optical axis, and G1 is the distance between the image side surface of the first lens and the object side surface of the second lens on the optical axis.

8. The wide- monitoring lens according to claim 1, characterized in that: The lens satisfies the relationship: TTL / EFL≤5.1, IMH / EFL≥1.5; wherein EFL is the effective focal length of the lens, TTL is the distance between the object side surface of the first lens and the imaging surface of the lens on the optical axis, and IMH is the image height of the lens.

9. The wide- monitoring lens according to claim 1, characterized in that: The lens satisfies: focal length: 4.0≤EFFL≤4.5mm; aperture F≤1.65; field of view angle: 2w≥120°; relative luminance: RI≥43%.

Images