A small day and night confocal security zoom lens and a working method thereof

Abstract

The application relates to a small day and night confocal security zoom lens and a working method thereof. The lens is composed of a compensation group and a zoom group arranged in sequence along the light incidence direction. The compensation group is composed of a first lens, a second lens and a third lens arranged in sequence along the light incidence direction. The zoom group is composed of a fourth lens, a fifth lens and a sixth lens arranged in sequence along the light incidence direction. The compensation group has a negative focal length, and the zoom group has a positive focal length. The lens is reasonably matched, so that the optical system has the optical characteristics of wide spectrum, large relative aperture, miniaturization, high image quality, day and night confocal monitoring and the like, and on-axis and off-axis aberrations are well corrected, and the imaging quality is good.

Description

TECHNICAL FIELD

[0001] The present application relates to a small day and night confocal security zoom lens and a working method thereof. BACKGROUND

[0002] According to different application environments, security lenses have fixed focus, zoom, floating aperture, fixed aperture, and lenses suitable for different wavelengths, such as: narrow space or home monitoring can use short-focus fixed-focus lenses; large-scale monitoring areas such as forest fire prevention and border monitoring use zoom lenses; visible infrared confocal lenses can be used at night or in low-illumination environments. The zoom lens can be regarded as being composed of multiple fixed-focus lenses with different focal lengths, which can realize short-distance large-scale monitoring and long-distance small-scale monitoring, so the selection of the lens should consider the use environment and cost to ensure that the use requirements can be met while the cost is controlled to the minimum. Widening the system working wavelength and field of view can obtain more information of the monitoring target, therefore, the security zoom lens with wide spectrum, large field of view, small size and high image quality has become the focus of research and development of security companies. Among them, the development of the day and night zoom monitoring lens with wide spectrum, large relative aperture, small size and high image quality is the core target of security companies and the target pursued by designers. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides a small day and night confocal security zoom lens and a working method thereof, which simultaneously considers optical characteristics such as wide spectrum, large relative aperture, small size, high image quality, day and night confocal monitoring, etc.

[0004] The solution adopted by the present application to solve the technical problem is a small day and night confocal security zoom lens: the lens is composed of a compensation group and a zoom group arranged in sequence along the light incident direction, the compensation group is composed of a first lens, a second lens and a third lens arranged in sequence along the light incident direction, the zoom group is composed of a fourth lens, a fifth lens and a sixth lens arranged in sequence along the light incident direction, the compensation group has negative optical power, the zoom group has positive optical power, and the fifth lens and the sixth lens are glued into a glued lens group.

[0005] Further, the first lens is a meniscus concave negative lens, the object side surface of which is a convex surface, and the image side surface of which is a concave surface; the second lens is a double-concave negative lens, the object side surface of which is a concave surface, and the image side surface of which is a concave surface; the third lens is a double-convex positive lens, the object side surface of which is a convex surface, and the image side surface of which is a convex surface; the fourth lens is a double-convex positive lens, the object side surface of which is a convex surface, and the image side surface of which is a convex surface; the fifth lens is a double-convex positive lens, the object side surface of which is a convex surface, and the image side surface of which is a convex surface; and the sixth lens is a double-concave negative lens, the object side surface of which is a concave surface, and the image side surface of which is a concave surface.

[0006] Further, 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.

[0007] Further, the air gap between the first lens and the second lens in the compensation group is 4.1-4.5 mm; the air gap between the second lens and the third lens is 1.0-1.5 mm; and the air gap between the fourth lens and the fifth lens in the zoom group is 0.1-0.5 mm.

[0008] Further, 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; and the sixth lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; wherein N d is the refractive index, and V d is the Abbe number.

[0009] Further, 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 ratios with respect to f1: 2.0<f2 / f1<3.0, -4.0<f3 / f1<-3.0, -2.0<f4 / f1<-1.0, -2.0<f5 / f1<-1.0, and 1.0<f6 / f1<2.0.

[0010] Further, the aspherical lens curve equation expressions of the second lens, the third lens, the fifth lens, and the sixth lens are as follows:

[0011]

[0012] wherein Z is the sagittal height of the aspherical surface at a height of h along the optical axis from the vertex of the aspherical surface; c is the paraxial curvature of the aspherical surface; k is the conic constant; and α1, α2, α3, α4, α5, α6, α7, and α8 are high-order coefficients.

[0013] Further, the lens satisfies: 3.0≤EFFL≤4.0 mm; the aperture F≤1.6; and the field of view angle: 2w≥120°.

[0014] Further, the rear side of the variable magnification group is provided with a filter, and the rear of the compensation group is provided with a diaphragm.

[0015] A working method of a small-sized day and night confocal security zoom lens is as follows: when light is incident, the light path sequentially enters a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens and a sixth lens, and finally forms an image on an image plane.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] 1. The lens has an imaging angle of the object greater than 120 degrees at the wide-angle end, and has the advantages of high imaging clarity, large light aperture, low tolerance sensitivity and good high-low temperature stability at the wide-angle end and the telephoto end, and can monitor more comprehensively;

[0018] 2. By reasonably matching the optical lenses, the system structure is compact and reasonable, easy to assemble, low in tolerance sensitivity, and more suitable for large-scale high-yield production;

[0019] 3. Two glass lenses are matched with four plastic lenses, which has lighter system mass compared with a full-glass system, and has stronger optical performance stability compared with a full-plastic system, while reducing the cost while adapting to the environment;

[0020] 4. The zoom design has both long-distance and near-distance wide-angle high-image-quality monitoring capabilities;

[0021] 5. The wide-angle end has a smaller F number and a larger light aperture, ensuring sufficient light quantity of the system, and being able to adapt to various complex environments;

[0022] 6. The focusing surface displacement can be compensated well at high and low temperatures, and has complex environment adaptability;

[0023] 7. The axial color difference, the sagittal color difference and the high-order color difference are corrected, so that the imaging system can also have high imaging quality at a large angle. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic view of the optical structure of the wide-angle end of the present application;

[0025] Figure 2 is an axial color difference graph of the wide-angle end of the present application;

[0026] Figure 3 is a sagittal color difference graph of the wide-angle end of the present application;

[0027] Figure 4 is a field curvature distortion graph of the wide-angle end of the present application;

[0028] Figure 5 is an axial chromatic aberration graph of the tele end of the present application;

[0029] Figure 6 is a transverse chromatic aberration graph of the tele end of the present application;

[0030] Figure 7 is a field curvature distortion graph of the tele end of the present application.

[0031] In the figure: STO - stop; L1 - first lens; L2 - second lens; L3 - third lens; L4 - fourth lens; L5 - fifth lens; L6 - sixth lens; L7 - equivalent glass flat plate; IMA - imaging plane. DETAILED DESCRIPTION

[0032] The present application is further illustrated below in conjunction with the accompanying drawings and specific embodiments.

[0033] As Figure 1 shown in the figure, a small day and night confocal security zoom lens: the lens is composed of a compensation group and a zoom group arranged in sequence along the light incident direction, the compensation group is composed of a first lens, a second lens and a third lens arranged in sequence along the light incident direction, the zoom group is composed of a fourth lens, a fifth lens and a sixth lens arranged in sequence along the light incident direction, the compensation group has a negative focal power, the zoom group has a positive focal power, the fifth lens and the sixth lens are glued into a glued lens group, wherein the first lens and the second lens are lenses with negative focal power, which adjusts large-angle light, wherein the plastic aspheric surface also has the effect of reducing the distortion of the optical system. The fifth lens and the sixth lens form an achromatic double-glued lens.

[0034] In this embodiment, the first lens is a meniscus concave negative lens, the object side surface of which is a convex surface, and the image side surface of which is a concave surface; the second lens is a double-concave negative lens, the object side surface of which is a concave surface, and the image side surface of which is a concave surface; the third lens is a double-convex positive lens, the object side surface of which is a convex surface, and the image side surface of which is a convex surface; the fourth lens is a double-convex positive lens, the object side surface of which is a convex surface, and the image side surface of which is a convex surface; the fifth lens is a double-convex positive lens, the object side surface of which is a convex surface, and the image side surface of which is a convex surface; the sixth lens is a double-concave negative lens, the object side surface of which is a concave surface, and the image side surface of which is a concave surface.

[0035] 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 aspheric lenses.

[0036] In this embodiment, the air gap between the first lens and the second lens in the compensation group is 4.1-4.5 mm; the air gap between the second lens and the third lens is 1.0-1.5 mm; and the air gap between the fourth lens and the fifth lens in the zoom group is 0.1-0.5 mm.

[0037] In the 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; wherein N d is the refractive index, V d is the Abbe number.

[0038] In the 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, wherein f2, f3, f4, f5, and f6 satisfy the following ratios with respect to f1: 2.0<f2 / f1<3.0, -4.0<f3 / f1<-3.0, -2.0<f4 / f1<-1.0, -2.0<f5 / f1<-1.0, and 1.0<f6 / f1<2.0.

[0039] In the embodiment, the aspherical lens curve equation expressions of the second lens, the third lens, the fifth lens, and the sixth lens are as follows:

[0040]

[0041] wherein Z is the sagittal height of the aspherical surface at a height of h along the optical axis; c is the paraxial curvature of the aspherical surface; k is the conic constant; and α1, α2, α3, α4, α5, α6, α7, and α8 are high-order coefficients.

[0042] In the embodiment, a filter is arranged at the rear side of the zoom group, and a diaphragm is arranged at the rear of the compensation group.

[0043] The technical indicators achieved by the optical system in the embodiment are as follows:

[0044] (1) focal length: 3.0≤EFFL≤4.0 mm;

[0045] (2) aperture: F≤1.6;

[0046] (3) field of view: 2w≥120°;

[0047] (4) working waveband: visible and short-wave infrared waveband.

[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]

[0051] The aspheric coefficients of each aspheric lens of the optical system of the embodiment are shown in the following table:

[0052]

[0053] The numerical value of the air layer thickness between the compensation group and the zoom group when the embodiment changes from the wide-angle end to the telephoto end is shown in the following table:

[0054] Compensation group and variator group air gap / mm Wide angle end 21.19 Telephoto end 0.45

[0055] A working method of a small-sized day and night confocal security zoom lens, when light is incident, the light path sequentially enters a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens, and finally forms an image on an image plane.

[0056] The embodiment realizes zoom, super wide-angle, large aperture, day and night confocal, low temperature drift design through reasonable lens matching, and simultaneously well corrects on-axis and off-axis aberrations, and has good imaging quality, as shown in Figures 2 to 7 .

[0057] Any technical solution disclosed in the above embodiments, unless otherwise stated, if a numerical range is disclosed, 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 numerical values with more obvious technical effects or representative values. Since there are too many values, it is impossible to enumerate them all, so the present application discloses some values to illustrate the technical solutions of the present application, and the above enumerated values should not constitute a limitation on the protection scope of the present application.

[0058] If the terms "first", "second", etc. are used to limit the components in this document, those skilled in the art should know that the use of "first", "second" is only for the convenience of describing the components to distinguish them, and the above terms have no special meaning unless otherwise stated.

[0059] If the present application discloses or relates to mutually fixedly connected parts or structural members, unless otherwise stated, the fixed connection can be understood as: detachably fixedly connected (for example, connected using bolts or screws), and can also be understood as: non-detachable fixed connection (for example, riveting, welding), of course, the mutually fixed connection can also be replaced by an integral structure (for example, manufactured by integral forming using casting process) (obviously, integral forming process cannot be used).

[0060] In addition, the above-mentioned application discloses any technical solution applied to indicate the position relationship, such as "vertical", "horizontal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. The orientation or position relationship is based on the orientation 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 must have a specific orientation, be constructed and operated in a specific orientation, therefore cannot be understood as a limitation of the patent, and the above-mentioned application discloses any technical solution applied to indicate the shape, unless otherwise stated, the meaning includes the shape similar, similar or close to the shape.

[0061] Any part provided by the present application can be assembled from multiple individual components, or can be a single component manufactured by integral forming process.

[0062] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to limit them; although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or some technical features can be replaced by equivalent ones; without departing from the spirit of the technical solutions of the present application, they should be covered in the technical solution range of the present application.

Claims

1. A small day and night confocal security zoom lens, characterized by: The lens comprises a compensation group and a zoom group arranged in sequence along the incident direction of light; the compensation group comprises a first lens, a second lens, and a third lens arranged in sequence along the incident direction of light; the zoom group comprises a fourth lens, a fifth lens, and a sixth lens arranged in sequence along the incident direction of light; the compensation group has negative optical power, the zoom group has positive optical power, and the fifth lens and the sixth lens are cemented together to form a cemented lens group; 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 biconcave negative lens with a concave object-side surface and a concave 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, wherein f2, f3, f4, f5, and f6 satisfy the following ratio with f1: 2.0 <f2 / f1<3.0,-4.0<f3 / f1<-3.0,-2.0<f4 / f1<-1.0,-2.0<f5 / f1<-1.0,1.0<f6 / f1<2.0; The air space between the first lens and the second lens in the compensation group is 4.1-4.5 mm; the air space between the second lens and the third lens is 1.0-1.5 mm; the air space between the fourth lens and the fifth lens in the zoom group is 0.1-0.5 mm.

2. The security 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 security 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 security zoom lens according to claim 1, characterized in that: The aspheric lens 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; c is the paraxial curvature of the aspheric surface; k is the cone constant; α1, α2, α3, α4, α5, α6, α7, and α8 are all high-order coefficients.

5. The security zoom lens according to claim 1, characterized in that: The lens meets the following requirements: 3.0≤EFFL≤4.0mm; aperture F≤1.6; Field of view: 2w≥120°.

6. The security zoom lens according to claim 1, characterized in that: A filter is provided at the rear side of the zoom group, and an aperture is provided at the rear side of the compensation group.

7. A method for operating a small day-night confocal security zoom lens, using the security zoom lens according to any one of claims 1-6, 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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