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

Abstract

The present application relates to a kind of small day and night confocal security zoom optical system and its working method: optical system is sequentially arranged by compensation group and zoom group along the direction of light incidence, the compensation group is sequentially arranged by first lens, second lens, third lens along the direction of light incidence, the zoom group is sequentially arranged by fourth lens, fifth lens, sixth lens along the direction of light incidence, the compensation group has negative optical power, the zoom group has positive optical power, the present application is by reasonable lens collocation, so that optical system realizes wide spectrum, large relative aperture, miniaturization and high image quality, day and night confocal monitoring and other optical characteristics, while on-axis, off-axis aberration is well corrected, with good imaging quality.

Description

Technical Field

[0001] The invention relates to a small day and night confocal security zoom optical system and a working method thereof. Background Art

[0002] Market demands for intelligent surveillance and security systems require not only effective daytime operation but also the ability to capture every detail of objects in low-light and nighttime environments, including color and facial features. The more detailed the features, the higher the efficiency of intelligent recognition. Visible-infrared confocal lenses can be used for nighttime and low-light environments. Broadening the system's operating wavelength and field of view allows for more information on the monitored target. Therefore, security zoom lenses with wide spectrum and large field of view have become a key R&D focus for security companies. The development of day / night zoom surveillance lenses with wide spectrum, large relative aperture, miniaturization, and high image quality is a core goal for security companies and a goal pursued by designers. Summary of the Invention

[0003] In view of the deficiencies in the prior art, the present invention provides a small day and night confocal security zoom optical system and its working method, which take into account the optical characteristics of wide spectrum, large relative aperture, miniaturization, high image quality, day and night confocal monitoring, etc.

[0004] The solution adopted by the present invention to solve the technical problem is a small day and night confocal security zoom optical system: the optical system 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, the compensation group has a negative optical focal length, and the magnification group has a positive optical focal length.

[0005] Furthermore, the first lens is a meniscus concave negative lens, whose object side surface is convex and the image side surface is concave; the second lens is a meniscus concave negative lens, whose object side surface is concave and the image side surface is convex; the third lens is a biconvex positive lens, whose object side surface is convex and the image side surface is convex; the fourth lens is a biconvex positive lens, whose object side surface is convex and the image side surface is convex; the fifth lens is a biconvex positive lens, whose object side surface is convex and the image side surface is convex; the sixth lens is a meniscus concave negative lens, whose object side surface is concave and the image side surface is convex.

[0006] 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.

[0007] Further, the air gap between the first lens and the second lens in the compensation group is 4.5-5.0 mm; the air gap between the second lens and the third lens is 0.1-0.5 mm; the air gap between the fourth lens and the fifth lens in the zoom group is 0.1-0.5 mm; and the air gap between the fifth lens and the sixth lens 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; 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

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

[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 optical system satisfies: 3.0≤EFFL≤4.0 mm; aperture F≤1.6; field of view angle: 2w≥120°.

[0014] Further, the rear side of the zoom 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 optical system: 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.

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

[0017] 1. The lens has an imaging angle of more 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 intake 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, sagittal color difference and high-order color difference are corrected, ensuring that the imaging system also has 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 This is a field curvature distortion diagram at the wide-angle end of the present invention;

[0028] Figure 5 is an axial chromatic aberration diagram at the telephoto end of the present invention;

[0029] Figure 6 is a diagram of vertical axial chromatic aberration at the telephoto end of the present invention;

[0030] Figure 7 This is a diagram of field curvature distortion at the telephoto end of the present invention.

[0031] 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

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] like Figure 1 As shown, a small day and night confocal security zoom optical system: the optical system 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, and the magnification group consists of 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, and the magnification group has positive optical power, wherein the first lens and the second lens are both lenses with negative optical power, which adjust large-angle light, and the plastic aspheric surface also has the function of reducing optical system distortion.

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

[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 aspherical lenses.

[0036] In the embodiment, the air gap between the first lens and the second lens in the compensation group is 4.5-5.0 mm; the air gap between the second lens and the third lens is 0.1-0.5 mm; the air gap between the fourth lens and the fifth lens in the zoom group is 0.1-0.5 mm; and the air gap between the fifth lens and the sixth lens 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, and 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, -3.0<f3 / f1<-2.0, -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 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.

[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 indexes realized by the optical system of the embodiment are as follows:

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

[0045] (2) aperture F≤1.6;

[0046] (3) field of view angle: 2w≥120°;

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

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

[0049]

[0050]

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

[0052]

[0053] 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 20.835 Telephoto end 0.45

[0055] A working method of a small-sized day-and-night confocal security zoom optical system: 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 by reasonable lens matching, and simultaneously well corrects on-axis and off-axis aberrations, and has good imaging quality, as shown in FIG. 5. Figures 2 to 7

[0057] Any technical solution disclosed in the present application, unless otherwise stated, if it discloses a numerical range, 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-mentioned enumerated values should not constitute a limitation on the protection scope of the present application.

[0058] ​If the words "first", "second" or the like are used in the description and claims to describe various components, it should be understood that these components should not be limited to the above terms as these terms are used only to distinguish one component from another. It is also possible that the words "first", "second" or the like are used to describe one component or feature while the other component or feature might also be claimed in other claims, without departing from the scope of the application.

[0059] If the present application discloses or involves mutually fixedly connected components or structural parts, unless otherwise stated, the fixed connection can be understood as: detachably fixed connection (for example, connected by using bolts or screws), or 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, integrally formed by using casting process) (except for obvious cases where integral forming process cannot be used).

[0060] In addition, the above-mentioned position relationship or position relationship for indicating the position relationship, such as "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. The orientation or position relationship shown in the drawing is based on the orientation or position relationship shown in the drawing, 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, and therefore cannot be understood as a limitation on the patent, and the above-mentioned position relationship for indicating the position relationship in any technical solution disclosed by the present application includes shapes similar, similar or close to the shape unless otherwise stated.

[0061] Any component provided by the present application can be assembled from a plurality of 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; 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 claimed.

Claims

1. A small day and night confocal security zoom optical system, characterized by: The optical system comprises a compensation group and a zoom group arranged in sequence along the incident direction of light, wherein the compensation group comprises a first lens, a second lens, and a third lens arranged in sequence along the incident direction of light, and the zoom group comprises a fourth lens, a fifth lens, and a sixth lens arranged in sequence along the incident direction of light, wherein the compensation group has a negative optical power and the zoom group has a positive optical power; The first lens is a negative meniscus concave lens with a convex object-side surface and a concave image-side surface. The second lens is a negative meniscus concave lens with a concave object-side surface and a convex 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 negative meniscus concave lens with a concave object-side surface and a convex image-side surface. The air gap between the first and second lenses in the compensation group is 4.5-5.0 mm; the air gap between the second and third lenses is 0.1-0.5 mm; the air gap between the fourth and fifth lenses in the zoom group is 0.1-0.5 mm; the air gap between the fifth and sixth lenses is 0.1-0.5 mm; 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,-3.0<f3 / f1<-2.0,-2.0<f4 / f1<-1.0,-2.0<f5 / f1<-1.0,1.0<f6 / f1<2.0。 2. The zoom optical system 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 zoom optical system according to claim 1, wherein: 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 zoom optical system according to claim 1, wherein: 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 zoom optical system according to claim 1, wherein: The optical system satisfies: 3.0≤EFFL≤4.0mm; aperture F≤1.6; Field of view: 2w≥120°.

6. The zoom optical system 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 optical system, using the zoom optical system 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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