Fixed-focus large-aperture short-axis high-definition imaging optical system

Abstract

The invention discloses a fixed-focus large-aperture short-axis high-definition imaging optical system, and relates to the technical field of optical imaging equipment. The optical system sequentially comprises a first biconvex lens, a first meniscus lens, a first biconcave lens, a first plano-concave lens, a first plano-convex lens, a second biconvex lens, a third biconvex lens, a second plano-convex lens and a second plano-concave lens from an object plane to an image plane. Wherein the first biconvex lens and the first meniscus lens form a first balsaming lens, and the second plano-convex lens and the second plano-concave lens form a second balsaming lens; the first meniscus lens is a positive meniscus lens, and the object side surfaces of the first plano-concave lens, the first plano-convex lens and the second plano-concave lens are planes; the first plano-convex lens serves as an aperture stop, and the clear aperture is reduced on the object plane sides of the first biconvex lens and the second biconvex lens. According to the fixed-focus large-aperture short-axis high-definition imaging optical system provided by the invention, a short-axis fixed-focus imaging system is formed only through nine lenses, and meanwhile, large-target-surface high-definition imaging is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of optical imaging devices, and particularly to a fixed-focus large-aperture short-axis high-definition 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, a long overall optical length and insufficient resolution at a focal length of 16 mm. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a fixed-focus large-aperture short-axis high-definition imaging optical system, which forms a short-axis fixed-focus imaging system with only nine lenses, and realizes high-definition imaging with a large target surface at the same time.

[0004] The present invention is implemented as follows:

[0005] A fixed-focus large-aperture short-axis high-definition imaging optical system sequentially includes, from the object surface to the image surface: a first double convex lens, a first meniscus lens, a first double concave lens, a first plano-concave lens, a first plano-convex lens, a second double convex lens, a third double convex lens, a second plano-convex lens, and a second plano-concave lens; wherein, the first double convex lens and the first meniscus lens form a first cemented lens, and the second plano-convex lens and the second plano-concave lens form a second cemented lens; the first meniscus lens is a positive meniscus lens, and the object sides of the first plano-concave lens, the first plano-convex lens and the second plano-concave lens are planes; the first plano-convex lens serves as an aperture stop, and at the same time reduces the light passing aperture on the object surface sides of the first double convex lens and the second double convex lens.

[0006] Further, the optical interval between the first cemented lens and the first double concave lens is 0.44 mm, the optical interval between the first double concave lens and the first plano-concave lens is 0.60 mm, the optical interval between the first plano-concave lens and the first plano-convex lens is 0.64 mm, and the optical intervals between the first plano-convex lens and the second double convex lens, between the second double convex lens and the third double convex lens, and between the third double convex lens and the second cemented lens are all 0.13 mm.

[0007] Preferably, the optical interval is maintained by setting corresponding spacer rings.

[0008] Further, the reduction ratio of the light passing aperture on the object surface sides of the first double convex lens and the second double convex lens is 0.36%-9.36% of the lens diameter.

[0009] Further, the reduction ratio of the light passing aperture on the object surface sides of the first double convex lens and the second double convex lens is 1% of the lens diameter.

[0010] Further, the curvatures of the nine optical spherical lenses satisfy the following relationships:

[0011] First biconvex lens: 9 ≤ R 1 ≤ 13, -5.5 ≤ R 2 ≤ -8;

[0012] First meniscus lens: -5 ≤ R 1 ≤ -8.5, -42 ≤ R 2 ≤ -48;

[0013] First biconcave lens: -11 ≤ R 1 ≤ -15, -11 ≤ R 2 ≤ -15;

[0014] First plano - concave lens: R 1 = 0, 8 ≤ R 2 ≤ 12;

[0015] First plano - convex lens: R 1 = 0, -36 ≤ R 2 ≤ -39;

[0016] Second biconvex lens: 17.5 ≤ R 1 ≤ 21.5, -11 ≤ R 2 ≤ -15;

[0017] Third biconvex lens: 21 ≤ R 1 ≤ 24, -39 ≤ R 2 ≤ -43;

[0018] Second plano - convex lens: 7 ≤ R 1 ≤ 11, R 2 = 0;

[0019] Second plano - concave lens: R 1 = 0, 3 ≤ R 2 ≤ 7;

[0020] Among them, R 1 is the curvature of the object side, and R 2 is the curvature of the image side.

[0021] Further, the focal length of the optical system is 16 mm ± 5%, and the total optical length is 28.68 mm.

[0022] Preferably, the first plano - convex lens, the second biconvex lens, and the third biconvex lens are made of ultra - low dispersion glass.

[0023] The present invention has the following advantages:

[0024] Two groups of cemented lenses are adopted. The nine lenses have a short optical interval. The light is converged by the first meniscus lens with a negative focal power, diverged by the first plano-concave lens with a positive focal power, converged by the second plano-convex lens, and diverged by the second plano-concave lens, realizing a large-angle refraction of light. The optical total length can be shortened preferably. When the focal length is 16 mm, the optical total length is only 28.68 mm. At the same time, the last lens is a plano-concave lens, which can diverge the light to realize a large target surface. When the focal length is 16 mm, the target surface reaches 1 / 1.8", and the resolution can reach 8 MP. The MTF (Modulation Transfer Function) is still greater than 0.3 at 250 mm / lp, and the comprehensive performance is very prominent. In addition, the nine optical lenses forming the optical system have no special shape, which is convenient for processing, has low sensitivity to tolerances, and can be mass-produced.

[0025] The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. In order to make the above and other purposes, features, and advantages of the present invention more obvious and understandable, the following specific embodiments of the present invention are given. Brief Description of the Drawings

[0026] The present invention will be further described below with reference to the drawings in conjunction with embodiments.

[0027] Figure 1 It is a schematic structural diagram of the optical system of the present invention;

[0028] Figure 2 It is a schematic diagram of the spot diagram of the optical system of the embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of the modulation transfer function result of the embodiment of the present invention;

[0030] Figure 4 It is one of the schematic diagrams of the optical aberration of the embodiment of the present invention;

[0031] Figure 5 It is another schematic diagram of the optical aberration of the embodiment of the present invention;

[0032] Figure 6 It is the third schematic diagram of the optical aberration of the embodiment of the present invention;

[0033] Figure 7 It is the fourth schematic diagram of the optical aberration of the embodiment of the present invention;

[0034] Figure 8 It is the fifth schematic diagram of the optical aberration of the embodiment of the present invention;

[0035] Figure 9 It is the sixth schematic diagram of the optical aberration of the embodiment of the present invention;

[0036] Figure 10Schematic diagram of the field curvature and distortion of the optical system according to the embodiments of the present invention. Detailed implementation manners

[0037] The embodiments of the present invention provide a fixed-focus large-aperture short-axis high-definition imaging optical system. The short-axis fixed-focus imaging system is composed of only 9 lenses, and high-definition imaging with a large target surface is achieved simultaneously.

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

[0039] Two groups of cemented lenses are adopted. The optical intervals of the nine lenses are short. The positive meniscus lens located at the second lens converges light, the plano-concave lens located at the fourth lens diverges light, the plano-convex lens located at the eighth lens converges light, and the plano-concave lens located at the ninth lens diverges light, so as to realize a large-angle refraction of light and better shorten the overall optical length. The last lens is a plano-concave lens, which can diverge light to realize a large target surface. Due to the divergence of the fourth plano-concave lens, the aperture stop is designed on the fifth lens to control the diverging light within the range required by the system design, so as to reduce aberration and improve clarity. At the same time, the light passing aperture is deliberately reduced on the left end of the first lens and the object side of the sixth lens to reduce the entry of stray light, which can reduce aberration and improve image quality.

[0040] According to the above invention idea, the present embodiment provides a fixed-focus large-aperture short-axis high-definition imaging optical system, as Figure 1 shown, which sequentially includes from the object surface to the image surface: a first biconvex lens 1, a first meniscus lens 2, a first biconcave lens 3, a first plano-concave lens 4, a first plano-convex lens 5, a second biconvex lens 6, a third biconvex lens 7, a second plano-convex lens 8, and a second plano-concave lens 9; wherein, the first biconvex lens 1 and the first meniscus lens 2 form a first cemented lens, and the second plano-convex lens 8 and the second plano-concave lens 9 form a second cemented lens for correcting chromatic aberration and improving the imaging effect; the first meniscus lens 2 is a positive meniscus lens, and the object sides of the first plano-concave lens 4, the first plano-convex lens 5, and the second plano-concave lens 9 are planes; the first plano-convex lens 5 serves as the aperture stop, and at the same time, the light passing aperture is reduced on the object sides of the first biconvex lens 1 and the second biconvex lens 6.

[0041] The first plano-convex lens 5, serving as the aperture stop, is located in the front-middle position of the entire optical system, which can effectively reduce the interference of other components inside the lens on light. When light passes through the aperture stop, it is restricted within a smaller range, thereby reducing the interaction with other components inside the lens and decreasing the possibility of internal reflection and scattering. The object-side surfaces of the first biconvex lens 1 and the second biconvex lens 6 are the surfaces with larger curvature. By reducing the clear aperture, part of the imaging light beams emitted from off-axis object points is blocked, reducing aberration, improving the clarity of the image, and enhancing the off-axis imaging quality. It can also improve the MTF (Modulation Transfer Function) performance of the lens, thus improving the overall quality of the image. Through the combination of positive, negative, negative, positive, positive, positive, and negative focal powers, an optical system can be achieved with a system focal length of 16 mm ± 5%, a phase plane meeting the same image quality for the entire field of view of 1 / 4", a resolution of 8 MP, an aperture of 2.1, and an MTF (Modulation Transfer Function) still greater than 0.3 at 250 mm / lp.

[0042] In a possible implementation, the optical interval between the first cemented lens and the first biconcave lens 3 is 0.44 mm, the optical interval between the first biconcave lens 3 and the first plano-concave lens 4 is 0.60 mm, the optical interval between the first plano-concave lens 4 and the first plano-convex lens 5 is 0.64 mm, and the optical intervals between the first plano-convex lens 5 and the second biconvex lens 6, between the second biconvex lens 6 and the third biconvex lens 7, and between the third biconvex lens 7 and the second cemented lens are all 0.13 mm. The optical intervals are maintained by setting corresponding spacer rings, and preferably, metal spacer rings can be used.

[0043] In a possible implementation, the reduction ratio of the clear aperture on the object-side surface of the first biconvex lens 1 and the second biconvex lens 6 is 0.36% - 9.36% of the lens diameter, and the preferred reduction ratio in this embodiment is 1% of the lens diameter.

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

[0045] First biconvex lens 1: 9 ≤ R 1 ≤ 13, -5.5 ≤ R 2 ≤ -8;

[0046] First meniscus lens 2: -5 ≤ R 1 ≤ -8.5, -42 ≤ R 2 ≤ -48;

[0047] First biconcave lens 3: -11 ≤ R 1 ≤ -15, -11 ≤ R 2 ≤ -15;

[0048] First plano-concave lens 4: R 1 = 0, 8 ≤ R 2 ≤ 12;

[0049] The first plano-convex lens 5: R 1 = 0, -36 ≤ R 2 ≤ -39;

[0050] The second biconvex lens 6: 17.5 ≤ R 1 ≤ 21.5, -11 ≤ R 2 ≤ -15;

[0051] The third biconvex lens 7: 21 ≤ R 1 ≤ 24, -39 ≤ R 2 ≤ -43;

[0052] The second plano-convex lens 8: 7 ≤ R 1 ≤ 11, R 2 = 0;

[0053] The second plano-concave lens 9: R 1 = 0, 3 ≤ R 2 ≤ 7;

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

[0055] Preferably, the first plano-convex lens 5, the second biconvex lens 6, and the third biconvex lens 7 are made of ultra-low dispersion glass, such as ultra-low dispersion glass of model H-FK61. Using ultra-low dispersion glass with a large Abbe number for the lenses with larger optical powers, namely the fifth, sixth, and seventh lenses, can effectively reduce the chromatic aberration of the system, improve the image quality, and enhance the infrared resolution.

[0056] In this embodiment, the optical system composed of the above lens group reaches the following optical indicators:

[0057] The focal length is 16 mm ± 5%, the total optical length is 28.68 mm, the target surface is 1 / 1.8", and the resolution is 8 MP.

[0058] As Figure 2 shown, it is the optical aberration schematic diagram of the embodiment of the present invention. The RMS radius is less than 2.8 (usually less than 3 is already a better indicator), and the GEO radius is less than 18 (usually less than 20 is already a better indicator).

[0059] 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 greater than 0.3 at 250 mm / lp.

[0060] Figures 4 to 9 This is the optical aberration schematic diagram of the embodiment of the present invention, which are the results when the image plane is at 0 mm, 1 mm, 2 mm, 3 mm, 3.8 mm, and 4.43 mm respectively.

[0061] Figure 10 This is a schematic diagram of the field curvature and distortion of the optical system according to an embodiment of the present invention. The sagittal field curvature is 0.0290 mm, the meridional field curvature is 0.0280 mm, the maximum field of view is 15.574 degrees, and the maximum distortion is 0.4101%, showing excellent performance.

[0062] The present invention uses two groups of cemented lenses. The optical intervals of the nine lenses are short. The light is converged by the first meniscus lens with a negative focal power, the light is diverged by the first plano-concave lens with a positive focal power, the light is converged by the second plano-convex lens, and the light is diverged by the second plano-concave lens, realizing a large-angle refraction of the light, which can preferably shorten the overall optical length. When the focal length is 16 mm, the overall optical length is only 28.68 mm. At the same time, the last lens is a plano-concave lens, which can diverge the light to achieve a large target surface. When the focal length is 16 mm, the target surface reaches 1 / 1.8", and the resolution can reach 8 MP. The MTF (Modulation Transfer Function) is still greater than 0.3 at 250 mm / lp, and the comprehensive performance is very prominent. In addition, the nine optical lenses constituting the optical system have no special shape, which is convenient for processing, has low sensitivity to tolerances, and can be mass-produced.

[0063] 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 large aperture short-axis high-definition imaging optical system, characterized by: From the object plane to the image plane, the lens includes a first biconvex lens, a first meniscus lens, a first biconcave lens, a first plano-concave lens, a first plano-convex lens, a second biconvex lens, a third biconvex lens, a second plano-convex lens and a second plano-concave lens in sequence; wherein, the first biconvex lens and the first meniscus lens form a first cemented lens, and the second plano-convex lens and the second plano-concave lens form a second cemented lens; the first meniscus lens is a positive meniscus lens, and the object side surfaces of the first plano-concave lens, the first plano-convex lens and the second plano-concave lens are planes; the first plano-convex lens acts as an aperture stop, and at the same time reduces the clear aperture on the object plane side of the first biconvex lens and the second biconvex lens.

2. The fixed-focus large aperture short-axis high-definition imaging optical system according to claim 1, characterized in that: The optical spacing between the first cemented lens and the first biconcave lens is 0.44mm, the optical spacing between the first biconcave lens and the first plano-concave lens is 0.60mm, the optical spacing between the first plano-concave lens and the first plano-convex lens is 0.64mm, and the optical spacing between the first plano-convex lens and the second biconvex lens, the second biconvex lens and the third biconvex lens, and the third biconvex lens and the second cemented lens are all 0.13mm.

3. The fixed-focus large aperture short-axis high-definition imaging optical system according to claim 2, characterized in that: The optical spacing is maintained by providing corresponding spacers.

4. The fixed-focus large aperture short-axis high-definition imaging optical system according to claim 1, characterized in that: The reduction ratio of the object-side clear aperture of the first biconvex lens and the second biconvex lens is 0.36%-9.36% of the lens diameter.

5. The fixed-focus large aperture short-axis high-definition imaging optical system according to claim 2, characterized in that: The reduction ratio of the object-side clear aperture of the first biconvex lens and the second biconvex lens is 1% of the lens diameter.

6. The fixed-focus large aperture short-axis high-definition imaging optical system according to claim 1, characterized in that: The curvatures of the nine optical spherical lenses satisfy the following relationship: First biconvex lens: 9≤R1≤13, -5.5≤R2≤-8; First meniscus lens: -5≤R1≤-8.5, -42≤R2≤-48; First biconcave lens: -11≤R1≤-15, -11≤R2≤-15; First plano-concave lens: R1=0, 8≤R2≤12; First plano-convex lens: R1=0, -36≤R2≤-39; Second biconvex lens: 17.5≤R1≤21.5, -11≤R2≤-15; The third biconvex lens: 21≤R1≤24, -39≤R2≤-43; Second plano-convex lens: 7≤R1≤11, R2=0; Second plano-concave lens: R1=0, 3≤R2≤7; Among them, R1 is the object side curvature, and R2 is the image side curvature.

7. The fixed-focus large aperture short-axis high-definition imaging optical system according to claim 6, characterized in that: The focal length of the optical system is 16 mm±5%, and the total optical length is 28.68 mm.

8. The fixed-focus large aperture short-axis high-definition imaging optical system according to claim 1, characterized in that: The first plano-convex lens, the second biconvex lens and the third biconvex lens are made of extra-low dispersion glass.

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