High-definition fisheye lens

Abstract

The utility model discloses a high-definition fisheye lens, and relates to the field of optical lenses. The lens sequentially comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens from an object side to an image side along an optical axis. Wherein the first lens, the second lens and the third lens are meniscus lenses with negative focal power, the fourth lens is a biconvex balsaming lens with positive focal power, and the fifth lens is a plano-convex lens with positive focal power; the concave surfaces of the first lens and the second lens face the imaging surface, the convex surface of the third lens faces the imaging surface, and the convex surface of the fifth lens faces the object side surface. According to the high-definition fisheye lens provided by the utility model, high-definition imaging is realized only through five lenses, and the high-definition fisheye lens has the advantages of long total length, small number of lenses and high resolution, and is easy to produce and assemble.

Description

Technical Field

[0001] This utility model relates to the field of optical lenses, specifically to a high-definition fisheye lens. Background Technology

[0002] A fisheye lens is a special type of photographic lens with an extremely large field of view, and is therefore widely used in fields such as scene monitoring, satellite positioning, robot navigation, micro-intelligent systems, and engineering surveying.

[0003] In some designs, a fisheye lens may be composed of a dozen or so different lenses. During the imaging process, incident light rays are refracted to varying degrees and projected onto an imaging plane of finite size. However, such designs are costly to manufacture and process, and difficult to assemble. Summary of the Invention

[0004] The technical problem to be solved by this utility model is to provide a high-definition fisheye lens that achieves high-definition imaging with only five lenses. It has the advantages of short total length, few lenses, and high resolution, and is easy to manufacture and assemble.

[0005] This utility model is implemented as follows:

[0006] A high-definition fisheye lens comprises, from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially along the optical axis; wherein the first lens, the second lens, and the third lens are all meniscus lenses with negative optical power, the fourth lens is a biconvex cemented lens with positive optical power, and the fifth lens is a plano-convex lens with positive optical power; the concave surfaces of the first and second lenses face the imaging plane, the convex surface of the third lens faces the imaging plane, and the convex surface of the fifth lens faces the object side.

[0007] Furthermore, it also includes an aperture stop, which is disposed between the third lens and the fourth lens.

[0008] Furthermore, the fourth lens consists of a meniscus lens and a biconvex lens.

[0009] Furthermore, the refractive index of the third lens is 1.85, the refractive index of the fourth lens (meniscus) is 1.92, the refractive index of the fourth lens (biconvex) is 1.77, and the refractive index of the fifth lens is 1.75.

[0010] Furthermore, the total optical length of the lens is 27.5mm.

[0011] Furthermore, the centering coefficient of the first lens is 0.24, the centering coefficient of the second lens is 0.37, the centering coefficient of the third lens is 0.06, and the centering coefficient of the fourth lens (a meniscus lens) is 0.20.

[0012] Furthermore, the first and second lenses are made of the same low-dispersion optical material, with an optical Abbe number of 60.4.

[0013] Furthermore, the radii of curvature of the five optical spherical lenses satisfy the following condition:

[0014] First lens: 16≤R1≤25, 3.5≤R2≤8.0;

[0015] Second lens: 37≤R1≤50, 2.0≤R2≤7.0;

[0016] Third lens: -40≤R1≤-33, -13.0≤R2≤-5.0;

[0017] Fourth lens: 7≤R1≤13, 2.5≤R2≤8.0, -12.0≤R3≤-5.0;

[0018] Fifth lens: 4≤R1≤12, R2 is infinite;

[0019] Among them, R n Let be the curvature of the nth spherical surface of each lens from the object side.

[0020] Furthermore, it also includes a protective window, positioned between the fifth lens and the imaging plane.

[0021] The advantages of this invention are as follows: by rationally distributing the optical power of the five lenses (three negative and two positive), a wide-angle field of view and short length can be achieved. Due to the small number of lenses, the processing and assembly are very convenient. With a 4.9mm image plane (CCD & CMOS), the field of view can reach 185°, and even at a field of view of 185°, the edge field of view still has 66.14% illumination. The total optical length is only 27.5mm, and the image circle diameter of the image plane is designed to be 4.5mm, which can achieve excellent 12MP imaging effect when imaging with the same small image plane, while also having good infrared confocality. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Figure 1 This is a schematic diagram of the structure of an embodiment of the present utility model;

[0024] Figure 2 This is a schematic diagram of a dotted line diagram of an embodiment of the present utility model;

[0025] Figure 3 This is a schematic diagram of the field curvature and distortion of the optical system according to an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the diffraction ring energy according to an embodiment of the present invention;

[0027] Figure 5 This is a schematic diagram of the MTF curve of an embodiment of the present invention;

[0028] Figure 6 This is a schematic diagram of the illuminance curve of an embodiment of the present invention. Detailed Implementation

[0029] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings and specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0030] In the description of this utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0031] Please see Figure 1 As shown, this embodiment provides a high-definition fisheye lens, which includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and a fifth lens 5 sequentially along the optical axis from the object side to the image side. The first lens 1, second lens 2, and third lens 3 are all meniscus lenses with negative optical power; the fourth lens 4 is a biconvex cemented lens with positive optical power; and the fifth lens 5 is a plano-convex lens with positive optical power. The concave surfaces of the first lens 1 and second lens 2 face the image plane, the convex surface of the third lens 3 faces the image plane, and the convex surface of the fifth lens 5 faces the object side. The optical system of this embodiment includes four monolithic optical lenses and one cemented doublet lens from left to right; fewer lenses effectively reduce production and assembly costs.

[0032] It also includes an aperture stop 6, which is disposed between the third lens 3 and the fourth lens 4 to limit the beam size of the optical system and ensure that the beam refracted to the fourth lens 4 is kept within the aperture range of the aperture stop, which can effectively improve the optical imaging quality.

[0033] It also includes a protective window 7, which is positioned between the fifth lens 5 and the imaging surface.

[0034] In one possible implementation, the fourth lens 4 consists of a meniscus lens and a biconvex lens.

[0035] Preferably, to shorten the overall optical length, a larger bend is needed in the light path section. The refractive index of the third lens is 1.85, the refractive index of the fourth lens (meniscus) is 1.92, the refractive index of the fifth lens (biconvex) is 1.77, and the refractive index of the fifth lens is 1.75. In this embodiment, the total optical length of the lens is 27.5 mm.

[0036] In one possible implementation, the radii of curvature of the five optical spherical lenses satisfy the following condition:

[0037] First lens 1: 16≤R1≤25, 3.5≤R2≤8.0;

[0038] Second lens 2: 37≤R1≤50, 2.0≤R2≤7.0;

[0039] Third lens 3: -40≤R1≤-33, -13.0≤R2≤-5.0;

[0040] Fourth lens 4: 7≤R1≤13, 2.5≤R2≤8.0, -12.0≤R3≤-5.0;

[0041] Fifth lens 5: 4≤R1≤12, R2 is infinite (plane);

[0042] Among them, R n Let be the curvature of the nth spherical surface of each lens from the object side.

[0043] In this embodiment, the curvature radii of the two spherical surfaces of each lens are significantly different, which avoids the inability to distinguish the two surfaces of a single lens and facilitates processing and assembly.

[0044] The fabrication of meniscus lenses involves a centering coefficient. If this coefficient is too small, it will hinder fabrication and severely impact the optical imaging quality of the system. Therefore, a brief explanation is necessary. The formula for the centering coefficient is as follows:

[0045]

[0046] Where D1 and D2 are the outer diameter of the clamp or the diameters on both sides of the lens, and R1 and R2 are the radii of curvature of the two surfaces; when both surfaces are positive or negative (biconvex or biconcave lens), a positive sign (+) is selected in the formula; when one surface is positive and the other is negative (meniscus lens), a negative sign (-) is selected in the formula. Based on the calculation results, the following classifications can be made:

[0047] Z < 0.05, making it difficult to achieve a stable mindset;

[0048] 0.05≤Z≤0.15, conventional core

[0049] Z > 0.15, making it easy to settle down.

[0050] Preferably, in this embodiment, the four meniscus lenses have a centering coefficient of 0.24 for the first lens 1, 0.37 for the second lens 2, 0.06 for the third lens 3, and 0.20 for the fourth lens 4 (which is a meniscus lens). All of these are easy to manufacture and will not cause significant eccentricity.

[0051] Preferably, to further reduce optical chromatic aberration, the first lens 1 and the second lens 2 are made of the same low-dispersion optical material with an optical Abbe number of 60.4. Since the first lens 1 and the second lens 2 are made of the same material, they can be coated simultaneously, greatly saving costs. At the same time, the lens surfaces are coated using advanced processes, which effectively enhances light transmission, reduces reflection loss, and improves light transmission efficiency.

[0052] By setting up three meniscus lenses with negative optical power (first lens 1, second lens 2, and third lens 3) and two lenses with positive optical power (fourth lens 4 and fifth lens 5), the reasonable distribution of three negative and two positive optical powers can achieve the effect of wide-angle field of view and short length.

[0053] In this embodiment, the optical system composed of the above-described lens group achieves the following optical properties:

[0054] With a 4.9mm image sensor (CCD & CMOS), the field of view reaches 185°, the total optical length is only 27.5mm, and the pixel count meets 12MP requirements. Even at a maximum field of view of 185°, the edge field of view still has 66.14% illumination. The image circle diameter is designed to be 4.5mm, achieving excellent 12MP imaging results with the same small image sensor. The focal length is only 1.5mm, distortion is 97.48%, and the maximum field of view is 185°; infrared confocal focusing is also good.

[0055] Figure 2 This is a schematic diagram of a dot pattern of an embodiment of the present invention. The dot pattern is basically within the Airy disk area, indicating that the imaging light is relatively concentrated and the imaging quality is high.

[0056] Figure 3 This is a schematic diagram of the field curvature and distortion of the optical system according to an embodiment of the present invention. Fisheye lenses all have distortion, but the distortion of this system can be controlled within -97.5%.

[0057] Figure 4 The diagram shows the diffraction ingress energy of an embodiment of this utility model. It can be seen that the curve fitting degree is high, indicating that the system energy is relatively concentrated.

[0058] Figure 5 The diagram shows the MTF curve of this utility model embodiment. It can be seen that the system MTF value is basically above 0.3 at a frequency of 200, indicating that the overall imaging quality of the system is high.

[0059] Figure 6 This is a schematic diagram of the illuminance curve of an embodiment of the present invention. Higher illuminance indicates better imaging quality.

[0060] This invention achieves a wide-angle, large field of view, and short length by rationally distributing the optical power of five lenses (three negative and two positive). Due to the small number of lenses, processing and assembly are very convenient. Combined with a 4.9mm image plane (CCD & CMOS), the field of view can reach 185°, and even at a field of view of 185°, the edge field of view still has 66.14% illumination. The total optical length is only 27.5mm, and the image circle diameter of the image plane is designed to be 4.5mm, which can achieve excellent 12MP imaging effect when imaging with the same small image plane, while also having good infrared confocality.

[0061] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended 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 within the scope of protection of the claims of the present invention.

Claims

1. A high definition fisheye lens characterized by: The first lens, the second lens, the third lens, the fourth lens and the fifth lens are sequentially arranged along the optical axis from the object side to the image side; wherein the first lens, the second lens and the third lens are meniscus lenses with negative focal power, the fourth lens is a double convex cemented lens with positive focal power, and the fifth lens is a plano-convex lens with positive focal power; the concave surface of the first lens and the second lens faces the imaging surface, the convex surface of the third lens faces the imaging surface, and the convex surface of the fifth lens faces the object side surface.

2. The high definition fisheye lens of claim 1, wherein: Further comprising a diaphragm, which is arranged between the third lens and the fourth lens.

3. The high definition fisheye lens of claim 1, wherein: The fourth lens is composed of a meniscus lens and a double convex lens.

4. The high definition fisheye lens of claim 3, wherein: The refractive index of the third lens is 1.85, the refractive index of the meniscus lens of the fourth lens is 1.92, the refractive index of the double convex lens of the fourth lens is 1.77, and the refractive index of the fifth lens is 1.

75.

5. The high definition fisheye lens of claim 4, wherein: The total optical length of the lens is 27.5mm.

6. The high definition fisheye lens of claim 3, wherein: The centering coefficient of the first lens is 0.24, the centering coefficient of the second lens is 0.37, the centering coefficient of the third lens is 0.06, and the centering coefficient of the meniscus lens of the fourth lens is 0.

20.

7. The high definition fisheye lens of claim 1, wherein: The first lens and the second lens are made of the same low dispersion optical material, and the optical Abbe number thereof is 60.

4.

8. The high definition fisheye lens of claim 1, wherein: The curvature radii of the five optical spherical lenses satisfy the following conditions: The first lens: 16≤R1≤25, 3.5≤R2≤8.0; The second lens: 37≤R1≤50, 2.0≤R2≤7.0; The third lens: -40≤R1≤-33, -13.0≤R2≤-5.0; The fourth lens: 7≤R1≤13, 2.5≤R2≤8.0, -12.0≤R3≤-5.0; The fifth lens: 4≤R1≤12, R2 is infinite; wherein R n is the curvature of the nth sphere from the object side for each lens.

9. The high definition fisheye lens of claim 1, wherein: Further comprising a protective window sheet arranged between the fifth lens and the imaging surface.

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