A six-piece security three-fold zoom lens and its imaging method

Abstract

The present invention relates to a six-piece security triple zoom lens and an imaging method thereof: the lens comprises a compensation group and a zoom group which are sequentially arranged along a light incident direction; the compensation group comprises a first lens, a second lens, and a third lens which are sequentially arranged along the light incident direction; the zoom group comprises a fourth lens, a fifth lens, and a sixth lens which are sequentially arranged along the light incident direction; and an aperture is provided between the compensation group and the zoom group. The present invention reasonably matches the optical lenses to make the system structure compact and reasonable, easy to assemble, with low tolerance sensitivity, and more suitable for large-scale high-yield production. The wide-angle end F number is smaller, the light aperture is larger, and sufficient light input to the system is ensured. The invention can adapt to a variety of complex environments, can make good compensation for focal plane displacement at high and low temperatures, has adaptability to complex environments, corrects various axial chromatic aberrations, vertical axis chromatic aberrations, and high-order chromatic aberrations, and ensures that the imaging system has high imaging quality even at large angles.

Description

Technical Field

[0001] The invention relates to a six-piece security triple zoom lens and an imaging method thereof. Background Art

[0002] Depending on the application environment, security lenses come in fixed-focus, zoom, floating aperture, fixed aperture, and lenses suitable for different wavelengths. For example, short-focus fixed lenses are suitable for confined spaces or home monitoring; zoom lenses are suitable for large-scale monitoring areas such as forest fire prevention and border surveillance; and visible infrared confocal lenses can be used for nighttime or low-light environments. Zoom lenses can be thought of as composed of multiple fixed-focus lenses with different focal lengths. They can achieve both short-range, large-area monitoring and long-range, small-area monitoring. Therefore, lens selection should consider the application environment and cost, ensuring that the lens meets the application requirements while minimizing costs.

[0003] Public safety monitoring is mostly all-weather monitoring during the day and at night, which makes the requirements for the performance and stability of zoom lenses more stringent. Therefore, most designs on the market use all-glass structures or structures with more lenses. Due to cost considerations, this is not conducive to the popularization and promotion of products. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is to provide a six-element security triple zoom lens and its imaging method, while taking into account the optical characteristics of wide spectrum, large relative aperture, miniaturization and high image quality, day and night confocal monitoring, etc.

[0005] The solution adopted by the present invention to solve the technical problem is a six-piece security triple zoom lens: the lens is composed of a compensation group and a magnification group arranged in sequence along the incident direction of light, the compensation group is composed of a first lens, a second lens, and a third lens arranged in sequence along the incident direction of light, and the magnification group is composed of a fourth lens, a fifth lens, and a sixth lens arranged in sequence along the incident direction of light.

[0006] Furthermore, the first lens is a meniscus concave negative lens, whose object side surface is convex and image side surface is concave; the second lens is a biconcave negative lens, whose object side surface is concave and image side surface is concave; the third lens is a biconvex positive lens, whose object side surface is convex and image side surface is convex; the fourth lens is a biconvex positive lens, whose object side surface is convex and image side surface is convex; the fifth lens is a biconvex positive lens, whose object side surface is convex and image side surface is convex; the sixth lens is a meniscus concave negative lens, whose object side surface is concave and image side surface is convex.

[0007] Furthermore, the first lens and the fourth lens are glass spherical lenses, and the second lens, the third lens, the fifth lens and the sixth lens are plastic aspherical lenses.

[0008] Furthermore, the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are f1, f2, f3, f4, f5, and f6, respectively, wherein f2, f3, f4, f5, and f6 satisfy the following ratio with f1: 0.0 <f2 / f1<1.0,-2.0<f3 / f1<-1.0,-1.0<f4 / f1<0.0,-1.0<f5 / f1<0.0,0.0<f6 / f1<1.0。

[0009] Furthermore, the first lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the second lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the third lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; the fourth lens satisfies the relationship: 1.2≤N d ≤1.5, V d ≥50.0; the fifth lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the sixth lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; where N d is the refractive index, V d is the Abbe constant.

[0010] Furthermore, the air gap between the first lens and the second lens is 2.5 to 3.0 mm; the air gap between the second lens and the third lens is 1.5 to 2.0 mm; the air gap between the fourth lens and the fifth lens is 0.1 to 0.5 mm; and the air gap between the fifth lens and the sixth lens is 0.1 to 0.5 mm.

[0011] Furthermore, the aspheric curve equations of the second lens, the third lens, the fifth lens, and the sixth lens are expressed as follows:

[0012]

[0013] Among them, Z is the height of the aspheric surface from the vertex of the aspheric surface when it is at a height of h along the optical axis; r is the height in the vertical direction relative to the optical axis; c is the paraxial curvature of the aspheric surface; k is the cone constant; α1, α2, α3, α4, α5, α6, α7·α8 are all high-order coefficients.

[0014] Furthermore, the system focal length of the overall optical lens satisfies: 3.0≤EFFL≤4.0mm.

[0015] Furthermore, the aperture F of the overall optical lens is ≤ 1.65, and the field of view angle of the overall optical lens is: 2w ≥ 130°.

[0016] An imaging method for a six-element security triple zoom lens: when light is incident, the light path sequentially enters a first lens, a second lens, a third lens, an aperture, a fourth lens, a fifth lens, and a sixth lens, and finally forms an image on an image plane.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The imaging angle of the lens at the wide-angle end is greater than 130 degrees. Both the wide-angle and telephoto ends have the advantages of high imaging clarity, large aperture, low tolerance sensitivity and good high and low temperature stability, which can provide more comprehensive monitoring.

[0019] 2. Through the reasonable matching of optical lenses, the system structure is compact and reasonable, easy to assemble, with low tolerance sensitivity, and more suitable for large-scale high-yield production;

[0020] 3. It uses two glass lenses with four plastic lenses. Compared with the all-glass system, it has a lighter system mass and stronger optical performance stability than the all-plastic system. At the same time, it can adapt to the environment and reduce costs.

[0021] 4. The zoom design provides both long-distance and close-range wide-angle and high-quality image monitoring capabilities;

[0022] 5. The F number at the wide-angle end is smaller and the aperture is larger, ensuring sufficient light entering the system and being able to adapt to a variety of complex environments;

[0023] 6. Able to make good compensation for focal plane displacement at high and low temperatures, and have adaptability to complex environments;

[0024] 7. The axial chromatic aberration, vertical chromatic aberration and high-order chromatic aberration are corrected to ensure that the imaging system can have high imaging quality even at large angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the optical structure of the wide-angle end of the present invention;

[0026] Figure 2 is an axial chromatic aberration diagram at the wide-angle end of the present invention;

[0027] Figure 3 This is a vertical axial chromatic aberration diagram at the wide-angle end of the present invention;

[0028] Figure 4 This is a field curvature distortion diagram at the wide-angle end of the present invention;

[0029] Figure 5 is an axial chromatic aberration diagram at the telephoto end of the present invention;

[0030] Figure 6 is a diagram of vertical axial chromatic aberration at the telephoto end of the present invention;

[0031] Figure 7 This is a field curvature distortion diagram at the telephoto end of the present invention.

[0032] In the figure: STO - aperture; L1 - first lens; L2 - second lens; L3 - third lens; L4 - fourth lens; L5 - fifth lens; L6 - sixth lens; L7 - equivalent glass plate; IMA - imaging surface. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0034] like Figure 1 As shown, a six-element security triple zoom lens: the lens consists of a compensation group and a magnification group arranged in sequence along the incident direction of light, the compensation group consists of a first lens, a second lens, and a third lens arranged in sequence along the incident direction of light, the magnification group consists of a fourth lens, a fifth lens, and a sixth lens arranged in sequence along the incident direction of light, an aperture is provided between the compensation group and the magnification group, and a filter is provided on the rear side of the magnification group.

[0035] In this embodiment, the first lens is a meniscus concave negative lens with a convex object-side surface and a concave image-side surface; the second lens is a biconcave negative lens with a concave object-side surface and a concave image-side surface; the third lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the fourth lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the fifth lens is a biconvex positive lens with a convex object-side surface and an image-side surface; and the sixth lens is a meniscus concave negative lens with a concave object-side surface and a convex image-side surface.

[0036] In this embodiment, the first lens and the fourth lens are glass spherical lenses, and the second lens, the third lens, the fifth lens, and the sixth lens are plastic aspherical lenses.

[0037] In this embodiment, both the first lens and the second lens are lenses with negative optical power, which adjust large-angle light. The plastic aspheric surface also has the function of reducing the distortion of the optical system.

[0038] In this embodiment, the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are f1, f2, f3, f4, f5, and f6, respectively, where f2, f3, f4, f5, and f6 satisfy the following ratio with f1: 0.0 <f2 / f1<1.0,-2.0<f3 / f1<-1.0,-1.0<f4 / f1<0.0,-1.0<f5 / f1<0.0,0.0<f6 / f1<1.0。

[0039] In this embodiment, the first lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the second lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the third lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; the fourth lens satisfies the relationship: 1.2≤N d ≤1.5, V d ≥50.0; the fifth lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the sixth lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; where N d is the refractive index, V d is the Abbe constant.

[0040] In this embodiment, the air gap between the first lens and the second lens is 2.5 to 3.0 mm; the air gap between the second lens and the third lens is 1.5 to 2.0 mm; the air gap between the fourth lens and the fifth lens is 0.1 to 0.5 mm; and the air gap between the fifth lens and the sixth lens is 0.1 to 0.5 mm.

[0041] In this embodiment, the aspheric curve equations of the second lens, the third lens, the fifth lens, and the sixth lens are expressed as follows:

[0042]

[0043] Among them, Z is the height of the aspheric surface from the vertex of the aspheric surface when it is at a height of h along the optical axis; r is the height in the vertical direction relative to the optical axis; c is the paraxial curvature of the aspheric surface; k is the cone constant; α1, α2, α3, α4, α5, α6, α7·α8 are all high-order coefficients.

[0044] The aspheric coefficients of the aspheric lenses of the optical system of this embodiment are as follows:

[0045]

[0046] In this embodiment, the technical indicators achieved by the optical system of this embodiment are as follows:

[0047] (1) System focal length: 3.0 ≤ EFFL ≤ 4.0 mm;

[0048] (2) Aperture F≤1.65;

[0049] (3) Field of view: 2w ≥ 130°;

[0050] (4) Working band: visible light and 850nm short-wave infrared band.

[0051] To achieve the above design parameters, the specific design adopted by the optical system of this embodiment is shown in the following table:

[0052]

[0053]

[0054] An imaging method for a six-element security triple zoom lens: when light is incident, the light path sequentially enters a first lens, a second lens, a third lens, an aperture, a fourth lens, a fifth lens, and a sixth lens, and finally forms an image on an image plane.

[0055] When this embodiment is moved from the wide-angle end to the telephoto end, the values of the thickness of the air layer between the compensation group and the zoom group are as follows:

[0056] Air layer distance between compensation group and zoom group / mm Wide-angle end 20.553 Telephoto end 2.402

[0057] This embodiment uses a reasonable lens combination to enable the optical system to achieve zoom, ultra-wide angle, large aperture, day and night confocal, and low temperature drift design, while also performing good correction for on-axis and off-axis aberrations, and having good imaging quality. Figures 2 to 7 shown.

[0058] Unless otherwise stated, for any of the technical solutions disclosed in the present invention, if a numerical range is disclosed, the disclosed numerical range is a preferred numerical range. Any person skilled in the art should understand that the preferred numerical range is merely a numerical range that is representative or has a more obvious technical effect among many feasible numerical values. Due to the large number of numerical values, it is impossible to enumerate them exhaustively. Therefore, the present invention discloses some numerical values to illustrate the technical solutions of the present invention. Moreover, the numerical values listed above should not be construed as limiting the scope of protection of the present invention.

[0059] If words such as "first" and "second" are used in this document to limit components, those skilled in the art should know that the use of "first" and "second" is only for the convenience of description to distinguish between components. Unless otherwise stated, the above words have no special meaning.

[0060] If the present invention discloses or involves components or structural parts that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by integrated molding using a casting process) (except where it is obviously impossible to use an integrated molding process).

[0061] In addition, the orientations or positional relationships indicated by terms such as "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", and "outside" used in any of the technical solutions disclosed in the above invention are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing this patent, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this patent. Unless otherwise stated, the terms used to indicate shapes used in any of the technical solutions disclosed in the above invention include shapes that are approximate, similar, or close to them.

[0062] Any component provided by the present invention may be assembled from multiple separate components, or may be a separate component manufactured by an integral molding process.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention. They should all be included in the scope of the technical solution for protection of the present invention.

Claims

1. A six-element security triple zoom lens, characterized by: The lens is composed of a compensation group and a zoom group arranged in sequence along the incident direction of light. The compensation group is composed of a first lens, a second lens, and a third lens arranged in sequence along the incident direction of light. The zoom group is composed of a fourth lens, a fifth lens, and a sixth lens arranged in sequence along the incident direction of light. The first lens is a meniscus concave negative lens with a convex object-side surface and a concave image-side surface; the second lens is a biconcave negative lens with a concave object-side surface and a concave image-side surface; the third lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the fourth lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the fifth lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the sixth lens is a meniscus concave negative lens with a concave object-side surface and a convex image-side surface; The focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are f1, f2, f3, f4, f5, and f6, respectively, where f2, f3, f4, f5, and f6 satisfy the following ratio with f1: 0.0 <f2 / f1<1.0,-2.0<f3 / f1<-1.0,-1.0<f4 / f1<0.0,-1.0<f5 / f1<0.0,0.0<f6 / f1<1.0。 2. The six-element security triple zoom lens according to claim 1, characterized in that: The first lens and the fourth lens are glass spherical lenses, and the second lens, the third lens, the fifth lens and the sixth lens are plastic aspherical lenses.

3. The six-element security triple zoom lens according to claim 1, characterized in that: The first lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the second lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the third lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; the fourth lens satisfies the relationship: 1.2≤N d ≤1.5, V d ≥50.0; the fifth lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the sixth lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; where N d is the refractive index, V d is the Abbe constant.

4. The six-element security triple zoom lens according to claim 3, characterized in that: The air gap between the first lens and the second lens is 2.5 to 3.0 mm; the air gap between the second lens and the third lens is 1.5 to 2.0 mm; the air gap between the fourth lens and the fifth lens is 0.1 to 0.5 mm; and the air gap between the fifth lens and the sixth lens is 0.1 to 0.5 mm.

5. The six-element security triple zoom lens according to claim 4, characterized in that: The aspheric curve equations of the second lens, the third lens, the fifth lens and the sixth lens are expressed as follows: Among them, Z is the height of the aspheric surface from the vertex of the aspheric surface when it is at a height of h along the optical axis; r is the height in the vertical direction relative to the optical axis; c is the paraxial curvature of the aspheric surface; k is the cone constant; α1, α2, α3, α4, α5, α6, α7·α8 are all high-order coefficients.

6. The six-element security triple zoom lens according to claim 5, characterized in that: The system focal length of the overall optical lens satisfies: 3.0≤EFFL≤4.0mm.

7. The six-element security triple zoom lens according to claim 6, characterized in that: The aperture of the overall optical lens is F≤1.65, and the field of view angle of the overall optical lens is: 2w≥130°.

8. An imaging method for a six-element security triple zoom lens, using the six-element security triple zoom lens of claim 7, characterized in that: When light is incident, the light path enters the first lens, the second lens, the third lens, the aperture, the fourth lens, the fifth lens and the sixth lens in sequence, and finally forms an image on the image plane.

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