Fixed-focus high-definition long-focus infrared confocal imaging optical system

Abstract

The invention discloses a fixed-focus high-definition long-focus infrared confocal imaging optical system, and relates to the technical field of optical imaging equipment. The optical system sequentially comprises a first meniscus lens, a first biconvex lens, a first biconcave lens, a second biconcave lens, a second biconvex lens, a second meniscus lens, a third biconvex lens, a third meniscus lens and a fourth meniscus lens from an object plane to an image plane. Wherein the first biconvex lens and the first biconcave lens form a first balsaming lens, the second biconcave lens and the second biconvex lens form a second balsaming lens, and the third biconvex lens and the third meniscus lens form a third balsaming lens; the first meniscus lens and the third meniscus lens are positive meniscus lenses, and the second meniscus lens and the fourth meniscus lens are negative meniscus lenses. The aperture diaphragm is disposed between the first biconcave lens and the second biconcave lens. According to the fixed-focus high-definition long-focus infrared confocal imaging optical system provided by the invention, large-target-surface high-definition imaging is realized only through nine lenses when the focal length is 35mm.

Description

Technical Field

[0001] The present invention relates to the technical field of optical imaging devices, and particularly to a fixed-focus high-definition long-focus infrared confocal imaging optical system. Background Art

[0002] With the gradual improvement of the public's quality of life, higher requirements have been put forward for the small size, light weight and high-definition imaging of lenses in the fields of smart home, face recognition, mobile security, etc. However, the existing security lenses have a small target surface at a focal length of 35 mm, insufficient infrared confocal ability, and insufficient resolution. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a fixed-focus high-definition long-focus infrared confocal imaging optical system, which can achieve large-target-surface high-definition imaging at a focal length of 35 mm only through nine lenses.

[0004] The present invention is implemented as follows:

[0005] A fixed-focus high-definition long-focus infrared confocal imaging optical system sequentially includes a first meniscus lens, a first biconvex lens, a first biconcave lens, a second biconcave lens, a second biconvex lens, a second meniscus lens, a third biconvex lens, a third meniscus lens, and a fourth meniscus lens from the object surface to the image surface; wherein, the first biconvex lens and the first biconcave lens form a first cemented lens, the second biconcave lens and the second biconvex lens form a second cemented lens, and the third biconvex lens and the third meniscus lens form a third cemented lens; the first meniscus lens and the third meniscus lens are positive meniscus lenses, and the second meniscus lens and the fourth meniscus lens are negative meniscus lenses; the aperture stop is arranged between the first biconcave lens and the second biconcave lens.

[0006] Further, a first virtual surface is arranged between the first meniscus lens and the first biconvex lens to limit the incident light angle and reduce the entry of stray light.

[0007] Further, the floating aperture of the first virtual surface is 0.1%-8% of the lens diameter.

[0008] Further, a second virtual surface is arranged between the second meniscus lens and the third biconvex lens to limit the light angle diverged by the second meniscus lens.

[0009] Further, the floating aperture of the second virtual surface is 0.3%-7% of the lens diameter.

[0010] Furthermore, the optical interval between the first meniscus lens and the first cemented lens ranges from 0.1 to 0.2 mm, the optical interval between the first cemented lens and the second cemented lens is 7 to 8.5 mm, the optical interval between the second cemented lens and the second meniscus lens ranges from 0.1 to 0.2 mm, the optical interval between the second meniscus lens and the third cemented lens ranges from 0.3 to 0.9 mm, and the optical interval between the third cemented lens and the fourth meniscus lens is 7 to 8.5 mm.

[0011] Furthermore, each optical interval is maintained by setting corresponding spacer rings.

[0012] Furthermore, the curvatures of the nine optical spherical lenses satisfy the following relationships:

[0013] First meniscus lens: 25 ≤ R 1 ≤ 30, 89 ≤ R 2 ≤ 93;

[0014] First biconvex lens: 12 ≤ R 1 ≤ 15, -283 ≤ R 2 ≤ -279;

[0015] First biconcave lens: -284 ≤ R 1 ≤ -280, 8 ≤ R 2 ≤ 12;

[0016] Second biconcave lens: -19 ≤ R 1 ≤ -15, 12 ≤ R 2 ≤ 15;

[0017] Second biconvex lens: 11 ≤ R 1 ≤ 14, -19 ≤ R 2 ≤ -16;

[0018] Second meniscus lens: -17 ≤ R 1 ≤ -13, -25 ≤ R 2 ≤ -21;

[0019] Third biconvex lens: 18 ≤ R 1 ≤ 21, -13 ≤ R 2 ≤ -16;

[0020] Third meniscus lens: -13 ≤ R 1 ≤ -16, -22 ≤ R 2 ≤ -19;

[0021] Fourth meniscus lens: -15 ≤ R 1 ≤ -11, -53 ≤ R 2 ≤ -50;

[0022] wherein, R 1The curvature of the object side is R 2 The curvature of the image side is

[0023] Furthermore, the focal length of the optical system is 35 mm ± 5%, the resolution reaches 8 MP, and the aperture is 1.8

[0024] Furthermore, at least two of the three groups of cemented lenses are made of ultra-low dispersion glass

[0025] The present invention has the following advantages

[0026] By setting the first lens as a positive meniscus lens, it is possible to converge light at a larger angle into the optical system, achieving a large aperture and a large diaphragm; the aperture stop is set between the third and fourth lenses, at the front end of the optical system, restricting the large-angle light converged by the positive meniscus lens and the cemented lens group in front of the aperture stop, which can effectively reduce aberration and improve clarity; a group of cemented lenses is set at each end of the aperture stop to achieve good achromatic aberration correction and improve infrared confocal clarity; a total of three groups of cemented lenses are set, effectively reducing the total length of the system while achieving achromatic aberration and improving infrared clarity; the last lens is a negative meniscus lens, diverging the light to achieve a large target surface; thus, an optical system with a focal length of 35 mm ± 5% is realized only by an optical system composed of nine lenses, the phase surface satisfies the same image quality in the 1' full field of view, the resolution reaches 8 MP, and the aperture is 1.8. The large target surface has high-definition imaging, and the comprehensive performance is very prominent. Moreover, the nine optical lenses have no special shape, are easy to process, are less sensitive to tolerances, and can be mass-produced BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings in conjunction with embodiments

[0028] Figure 1 It is a schematic structural diagram of the optical system of the present invention

[0029] Figure 2 It is a schematic diagram of the spot diagram of the optical system of the embodiment of the present invention

[0030] Figure 3 It is a schematic diagram of the modulation transfer function result of the embodiment of the present invention

[0031] Figure 4 It is one of the ray fan diagrams of the embodiment of the present invention

[0032] Figure 5 It is the second ray fan diagram of the embodiment of the present invention

[0033] Figure 6 It is the third ray fan diagram of the embodiment of the present invention

[0034] Figure 7 It is the fourth ray fan diagram of the embodiment of the present invention

[0035] Figure 8 This is the fifth light fan diagram of the embodiment of the present invention;

[0036] Figure 9 This is a schematic diagram of the field curvature and distortion of the optical system in the embodiment of the present invention. Detailed implementation manners

[0037] In the embodiment of the present invention, a fixed-focus high-definition long-focus infrared confocal imaging optical system is provided, which can achieve high-definition imaging of a large target surface at a focal length of 35 mm with only nine lenses.

[0038] The general idea of the technical solution in the embodiment of the present invention is as follows:

[0039] The first lens of the optical system is set as a positive meniscus lens, which can converge light at a larger angle into the system to achieve a large aperture and a large aperture diaphragm. The aperture stop is arranged between the third and fourth lenses, at the front end of the optical system, restricting the large-angle light converged by the positive meniscus lens and the cemented lens group in front of the aperture stop, which can effectively reduce aberration and improve clarity. A group of cemented lenses is arranged at each end of the aperture stop to achieve good chromatic aberration correction and improve infrared confocal clarity. The system is provided with three groups of cemented lenses in total, effectively reducing the total length of the system while achieving chromatic aberration correction and improving infrared clarity. The last lens uses a negative meniscus lens to diverge the light to achieve a large target surface. The optical system adopts a combination of positive, positive, negative, negative, negative, positive, negative, and positive optical powers, which can achieve a system focal length of 35 mm ± 5%, the phase surface satisfies the same image quality in the 1' full field of view, the resolution reaches 8 MP, and the aperture is 1.8.

[0040] In addition, virtual surfaces are respectively set between the first lens and the second lens, and between the sixth lens and the seventh lens as floating apertures. The former is used to limit the incident light angle, reduce stray light entry, reduce aberration and improve clarity; the latter is used to limit the light angle diverged by the sixth negative meniscus lens to avoid excessive angle and inability to converge the light later.

[0041] According to the above inventive concept, this embodiment provides a fixed-focus large-aperture short-axis high-definition imaging optical system, as Figure 1As shown in the figure, from the object surface to the image surface, it successively includes: a first meniscus lens 1, a first biconvex lens 2, a first biconcave lens 3, a second biconcave lens 4, a second biconvex lens 5, a second meniscus lens 6, a third biconvex lens 7, a third meniscus lens 8, and a fourth meniscus lens 9. Among them, the first biconvex lens 2 and the first biconcave lens 3 form a first cemented lens, the second biconcave lens 4 and the second biconvex lens 5 form a second cemented lens, and the third biconvex lens 7 and the third meniscus lens 8 form a third cemented lens. The first meniscus lens 1 and the third meniscus lens 8 are positive meniscus lenses, and the second meniscus lens 6 and the fourth meniscus lens 9 are negative meniscus lenses. The aperture stop 10 is arranged between the first biconcave lens 3 and the second biconcave lens 4. A total of three groups of cemented lenses are set, which can effectively reduce the total length of the system while achieving achromatism and improving infrared clarity. The aperture stop 10 is located at the front end of the optical system, restricting the large-angle light rays converged by the positive meniscus lens and the cemented lens group in front of the aperture stop 10, which can effectively reduce aberration and improve clarity.

[0042] In a possible implementation manner, a first virtual surface A is arranged between the first meniscus lens 1 and the first biconvex lens 2, which is used to limit the incident light angle, reduce the entry of stray light, reduce aberration and improve clarity. A second virtual surface B is arranged between the second meniscus lens 6 and the third biconvex lens 7, which is used to limit the light angle diverged by the second meniscus lens 6 to avoid the situation that the light rays cannot converge later due to too large an angle. Preferably, the floating aperture of the first virtual surface A is 0.1%-8% of the lens diameter, and the floating aperture of the second virtual surface B is 0.3%-7% of the lens diameter. At least two of the three groups of cemented lenses can be made of ultra-low dispersion glass. For example, ultra-low dispersion glass of model H-FK95N can be used, which can effectively reduce the chromatic aberration of the system and improve infrared clarity. Ideally, the virtual surface is realized by designing a single surface with almost no thickness but having a light passing aperture.

[0043] In a possible implementation manner, the optical interval between the first meniscus lens 1 and the first cemented lens ranges from 0.1 to 0.2 mm, the optical interval between the first cemented lens and the second cemented lens is 7 to 8.5 mm, the optical interval between the second cemented lens and the second meniscus lens 6 is 0.1 to 0.2 mm, the optical interval between the second meniscus lens 6 and the third cemented lens is 0.3 to 0.9 mm, and the optical interval between the third cemented lens and the fourth meniscus lens 9 is 7 to 8.5 mm. Each optical interval is maintained by setting corresponding spacer rings. Preferably, metal spacer rings can be used. After the spacer ring shrinks the aperture, it can also be used to realize the above-mentioned first virtual surface A and second virtual surface B at the same time.

[0044] In a specific embodiment, the curvatures of the nine optical spherical lenses satisfy the following relationship:

[0045] For the first meniscus lens: 25 ≤ R 1≤30, 89 ≤ R 2 ≤93;

[0046] First biconvex lens: 12 ≤ R 1 ≤15, -283 ≤ R 2 ≤ -279;

[0047] First biconcave lens: -284 ≤ R 1 ≤ -280, 8 ≤ R 2 ≤12;

[0048] Second biconcave lens: -19 ≤ R 1 ≤ -15, 12 ≤ R 2 ≤15;

[0049] Second biconvex lens: 11 ≤ R 1 ≤14, -19 ≤ R 2 ≤ -16;

[0050] Second meniscus lens: -17 ≤ R 1 ≤ -13, -25 ≤ R 2 ≤ -21;

[0051] Third biconvex lens: 18 ≤ R 1 ≤21, -13 ≤ R 2 ≤ -16;

[0052] Third meniscus lens: -13 ≤ R 1 ≤ -16, -22 ≤ R 2 ≤ -19;

[0053] Fourth meniscus lens: -15 ≤ R 1 ≤ -11, -53 ≤ R 2 ≤ -50;

[0054] Wherein, R 1 is the curvature of the object side, and R 2 is the curvature of the image side.

[0055] In this embodiment, the optical system composed of the above lens group achieves the following optical indicators: the focal length is 35mm ± 5%, the resolution reaches 8MP, the aperture is 1.8, and the comprehensive performance is very prominent.

[0056] As Figure 2 shown, it is the optical aberration schematic diagram of the embodiment of the present invention. It can be seen that the RMS radius is less than 3.3 and the GEO radius is less than 18.2.

[0057] Figure 3 This is the modulation transfer function result of the embodiment of the present invention. It can be seen that the MTF (modulation transfer function) is still basically greater than 0.2 at 200mm / lp.

[0058] Figures 4 to 8 The ray fan diagram of the embodiment of the present invention, which are the results when the object plane is at 0mm, 4mm, 7.5mm, 10.4mm, and 14.3mm respectively.

[0059] Figure 9 The schematic diagram of the field curvature and distortion of the optical system of the embodiment of the present invention, with the maximum field of view being 14.3 degrees.

[0060] By setting the first lens as a positive meniscus lens, the present invention can converge light rays at a larger angle into the optical system to achieve a large aperture and large aperture ratio; the aperture stop is set between the third and fourth lenses, at the front end of the optical system, to limit the large-angle light rays converged by the positive meniscus lens and the cemented lens group in front of the aperture stop, which can effectively reduce aberration and improve clarity; a set of cemented lenses is provided at each end of the aperture stop to achieve good achromatic aberration correction and improve infrared confocal clarity; a total of three sets of cemented lenses are provided to effectively reduce the total length of the system while achieving achromatic aberration correction and improving infrared clarity; the last lens is a negative meniscus lens to diverge the light rays to achieve a large target surface; thus, an optical system with a focal length of 35mm ± 5% is achieved only by an optical system composed of nine lenses, the phase surface meets the same image quality for the entire 1' field of view, the resolution reaches 8MP, and the aperture is 1.8. The large target surface has high-definition imaging, and the comprehensive performance is very prominent. Moreover, the nine optical lenses have no special shape, are easy to process, have low sensitivity to tolerances, and can be mass-produced.

[0061] Although the specific embodiments of the present invention have been described above, those skilled in the art of this technology should understand that the specific embodiments we described are illustrative rather than used to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered by the scope protected by the claims of the present invention.

Claims

1. A fixed-focus high-definition long-focus infrared confocal imaging optical system, characterized in that: From the object plane to the image plane, the lens includes a first meniscus lens, a first biconvex lens, a first biconcave lens, a second biconcave lens, a second biconvex lens, a second meniscus lens, a third biconvex lens, a third meniscus lens and a fourth meniscus lens in sequence; wherein, the first biconvex lens and the first biconcave lens form a first cemented lens, the second biconcave lens and the second biconvex lens form a second cemented lens, and the third biconvex lens and the third meniscus lens form a third cemented lens; the first meniscus lens and the third meniscus lens are positive meniscus lenses, and the second meniscus lens and the fourth meniscus lens are negative meniscus lenses; and the aperture stop is arranged between the first biconcave lens and the second biconcave lens.

2. The optical system according to claim 1, characterized in that: A first virtual surface is provided between the first meniscus lens and the first biconvex lens to limit the angle of incoming light and reduce the entry of stray light.

3. The optical system according to claim 2, characterized in that: The floating aperture of the first virtual surface is 0.1%-8% of the lens diameter.

4. The optical system according to any one of claims 1, 2 and 3, characterized in that: A second virtual surface is provided between the second meniscus lens and the third biconvex lens, for limiting the angle of light rays diverged by the second meniscus lens.

5. The optical system according to claim 4, characterized in that: The floating aperture of the second virtual surface is 0.3%-7% of the lens diameter.

6. The optical system according to claim 1, characterized in that: The optical spacing between the first meniscus lens and the first cemented lens is in the range of 0.1-0.2mm, the optical spacing between the first cemented lens and the second cemented lens is 7-8.5mm, the optical spacing between the second cemented lens and the second meniscus lens is 0.1-0.2mm, the optical spacing between the second meniscus lens and the third cemented lens is 0.3-0.9mm, and the optical spacing between the third cemented lens and the fourth meniscus lens is 7-8.5mm.

7. The optical system according to claim 6, characterized in that: Each optical interval is maintained by setting a corresponding spacer.

8. The optical system according to claim 1, characterized in that The curvatures of the nine optical spherical lenses satisfy the following relationship: First meniscus lens: 25≤R1≤30, 89≤R2≤93; First biconvex lens: 12≤R1≤15, -283≤R2≤-279; First biconcave lens: -284≤R1≤-280, 8≤R2≤12; Second biconcave lens: -19≤R1≤-15, 12≤R2≤15; Second biconvex lens: 11≤R1≤14, -19≤R2≤-16; Second meniscus lens: -17≤R1≤-13, -25≤R2≤-21; The third biconvex lens: 18≤R1≤21, -13≤R2≤-16; Third meniscus lens: -13≤R1≤-16, -22≤R2≤-19; Fourth meniscus lens: -15≤R1≤-11, -53≤R2≤-50; Among them, R1 is the object side curvature, and R2 is the image side curvature.

9. The optical system according to claim 8, characterized in that: The optical system has a focal length of 35mm ± 5%, a resolution of 8MP, and an aperture of 1.

8.

10. The optical system according to claim 1, characterized in that: At least two of the three cemented lens groups are made of extra-low dispersion glass.

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