Fisheye lens

Abstract

The present invention relates to a fisheye lens, comprising a first lens (L1) with negative focal power, a second lens (L2) with negative focal power, a third lens (L3) with negative focal power, a fourth lens (L4) with positive focal power, a stop (STO), a fifth lens (L5) with positive focal power, a sixth lens (L6) with negative focal power and a seventh lens (L7) with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis, wherein the distance d56 from the image side optical axis center of the fifth lens (L5) to the object side optical axis center of the sixth lens (L6) and the distance BFL from the image side optical axis center of the seventh lens (L7) to the image plane satisfy the following relationship: 0.01≤d56 / BFL≤0.06. The fisheye lens of the present invention has the characteristics of large angle, high resolution, day and night confocality and no defocusing in the temperature range of -40°C to 80°C.

Description

Technical Field

[0001] The present invention relates to the technical field of optical imaging, and in particular to a fisheye lens. Background Art

[0002] With the improvement of living standards and the enhancement of safety awareness, people have higher requirements for home security. Therefore, consumers generally require surveillance lenses to have wide angles, high resolutions, and bright and clear camera images even in dim environments at night. Among the many optical lenses used in the field of surveillance, fisheye lenses have the advantage of a large field of view, but the imaging quality of most existing fisheye lenses is not ideal, and they cannot achieve day and night confocality, thus failing to meet the growing needs of consumers. Therefore, it is urgent to design a fisheye lens with high imaging performance and day and night confocality. Summary of the invention

[0003] The object of the present invention is to provide a fisheye lens.

[0004] To achieve the above-mentioned object of the invention, the present invention provides a fisheye lens, comprising a first lens with negative optical focal power, a second lens with negative optical focal power, a third lens with negative optical focal power, a fourth lens with positive optical focal power, an aperture, a fifth lens with positive optical focal power, a sixth lens with negative optical focal power and a seventh lens with positive optical focal power, which are arranged in sequence from the object side to the image side along the optical axis, wherein a distance d56 from the optical axis center of the image side surface of the fifth lens to the optical axis center of the object side surface of the sixth lens and a distance BFL from the optical axis center of the image side surface of the seventh lens to the image plane satisfy the following relationship: 0.01≤d56 / BFL≤0.06.

[0005] According to one aspect of the present invention, the first lens is convexo-concave, the second lens is convexo-concave, the third lens is biconcave, the fourth lens is convexo-concave or biconvex, the fifth lens is biconvex, the sixth lens is biconcave, and the seventh lens is biconvex.

[0006] According to one aspect of the present invention, the first lens is a spherical lens, the second lens is an aspherical lens, the third lens is an aspherical lens, the fourth lens is a spherical or aspherical lens, the fifth lens is a spherical or aspherical lens, the sixth lens is an aspherical lens, and the seventh lens is an aspherical lens.

[0007] According to one aspect of the present invention, an Abbe number of at least one of the fourth lens and the fifth lens is ≥50.

[0008] According to one aspect of the present invention, the focal length f1 of the first lens, the focal length f3 of the third lens and the focal length f6 of the sixth lens respectively satisfy the following relationship with the effective focal length f of the fisheye lens: -8.1≤f1 / f≤-4.2; -5.4≤f3 / f≤-2; -2.7≤f6 / f≤-1.4.

[0009] According to one aspect of the present invention, the focal length f2 of the second lens, the focal length f4 of the fourth lens, the focal length f5 of the fifth lens and the focal length f7 of the seventh lens respectively satisfy the following relationship with the effective focal length f of the fisheye lens: -3.8≤f2 / f≤-2.1; 2≤f4 / f≤4.1; 2.1≤f5 / f≤3; 1.7≤f7 / f≤2.8.

[0010] According to one aspect of the present invention, a distance BFL from the center of the image-side optical axis of the seventh lens to the image plane and a total length TTL of the fisheye lens satisfy the following relationship: 0.19≤BFL / TTL≤0.32.

[0011] According to one aspect of the present invention, the total length TTL and the effective focal length f of the fisheye lens satisfy the following relationship: 9.7≤TTL / f≤13.6.

[0012] According to one aspect of the present invention, a curvature radius R11 of the image-side surface of the fifth lens and a curvature radius R12 of the object-side surface of the sixth lens satisfy the following relationship: 0.5≤|R12 / R11|≤3.

[0013] According to one aspect of the present invention, a curvature radius R5 of the object side surface of the third lens and a curvature radius R15 of the image side surface of the seventh lens satisfy the following relationship: 2.5≤|R5 / R15|≤4.5.

[0014] According to the concept of the present invention, a glass-plastic hybrid fisheye lens is provided which can achieve large angle, high resolution, day and night confocality and no defocusing in the temperature range of -40°C to 80°C.

[0015] According to one solution of the present invention, the maximum aperture of the fisheye lens reaches FNO2.0, and the imaging target surface reaches 1 / 3". Moreover, by mixing glass lenses and plastic lenses, visible light and infrared light can be confocal, thereby effectively reducing the cost of the lens. The CRA of the lens is ≤22°, so it can be adapted to a variety of sensors, making the application prospects broad and the market competitiveness greater. The lens can also achieve image capture with an object field angle of 214° and F-theta distortion ≤38%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A structural diagram schematically showing a fisheye lens according to a first embodiment of the present invention;

[0017] Figure 2 Schematically showing the FFT-MTF diagram of the fisheye lens with a frequency of 200 lp / mm according to the first embodiment of the present invention;

[0018] Figure 3 Schematically showing a Through-Focus-MTF diagram of a fisheye lens with a frequency of 120 lp / mm according to a first embodiment of the present invention;

[0019] Figure 4 Schematically showing the Through-Focus-MTF diagram of the fisheye lens of the first embodiment of the present invention at a low temperature of -40°C and a frequency of 120lp / mm;

[0020] Figure 5 Schematically showing the Through-Focus-MTF diagram of the fisheye lens of the first embodiment of the present invention at a high temperature of 80°C and a frequency of 120lp / mm;

[0021] Figure 6 A diagram schematically showing an F-Theta distortion curve of a fisheye lens according to a first embodiment of the present invention;

[0022] Figure 7 A structural diagram schematically showing a fisheye lens according to a second embodiment of the present invention;

[0023] Figure 8 Schematically showing the FFT-MTF diagram of the fisheye lens with a frequency of 200 lp / mm according to the second embodiment of the present invention;

[0024] Fig. 9 Schematically showing a Through-Focus-MTF diagram of a fisheye lens with a frequency of 120 lp / mm according to a second embodiment of the present invention;

[0025] Fig.10 Schematically showing the Through-Focus-MTF diagram of the fisheye lens of the second embodiment of the present invention at a low temperature of -40°C and a frequency of 120 lp / mm;

[0026] Fig.11 Schematically showing the Through-Focus-MTF diagram of the fisheye lens of the second embodiment of the present invention at a high temperature of 80°C and a frequency of 120lp / mm;

[0027] Fig.12 A diagram schematically showing an F-Theta distortion curve of a fisheye lens according to a second embodiment of the present invention;

[0028] Fig.13 A schematic diagram showing the structure of a fisheye lens according to a third embodiment of the present invention;

[0029] Fig.14 Schematically showing the FFT-MTF diagram of the fisheye lens with a frequency of 200 lp / mm according to the third embodiment of the present invention;

[0030] Fig.15 Schematically showing a Through-Focus-MTF diagram of a fisheye lens with a frequency of 120 lp / mm according to a third embodiment of the present invention;

[0031] Fig.16 Schematically showing the Through-Focus-MTF diagram of the fisheye lens of the third embodiment of the present invention at a low temperature of -40°C and a frequency of 120lp / mm;

[0032] Fig.17 Schematically showing the Through-Focus-MTF diagram of the fisheye lens of the third embodiment of the present invention at a high temperature of 80°C and a frequency of 120lp / mm;

[0033] Fig.18 FIG. 1 schematically shows an F-Theta distortion curve of a fisheye lens according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0036] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not therefore limited to the following embodiments.

[0037] See also Figure 1The fisheye lens of the present invention comprises a first lens L1 with negative power, a second lens L2 with negative power, a third lens L3 with negative power, a fourth lens L4 with positive power, an aperture STO, a fifth lens L5 with positive power, a sixth lens L6 with negative power and a seventh lens L7 with positive power, which are arranged in sequence from the object side to the image side along the optical axis. In the present invention, the distance d56 from the center of the image side optical axis of the fifth lens L5 to the center of the object side optical axis of the sixth lens L6 and the distance BFL from the center of the image side optical axis of the seventh lens L7 to the image plane satisfy the following relationship: 0.01≤d56 / BFL≤0.06. In this way, when the back focal length is limited, it is beneficial to reduce the tolerance sensitivity of the optical system.

[0038] In the present invention, the first lens L1 is convexo-concave, the second lens L2 is convexo-concave, the third lens L3 is biconcave, the fourth lens L4 is convexo-concave or biconvex, the fifth lens L5 is biconvex, the sixth lens L6 is biconcave, and the seventh lens L7 is biconvex. In this way, by reasonably setting the concave-convexity of each lens, it is beneficial to reasonably distribute the optical power of the optical system, so that the light can be better transmitted to ensure the imaging quality.

[0039] In the present invention, the first lens L1 is a spherical lens, the second lens L2 is an aspherical lens, the third lens L3 is an aspherical lens, the fourth lens L4 is a spherical or aspherical lens, the fifth lens L5 is a spherical or aspherical lens, the sixth lens L6 is an aspherical lens, and the seventh lens L7 is an aspherical lens. In this way, through the reasonable combination of spherical lenses and aspherical lenses, various aberrations in the optical system can be corrected, thereby improving the resolution of the lens.

[0040] In the present invention, the Abbe number of at least one of the fourth lens L4 and the fifth lens L5 is ≥50. Meeting this condition can effectively balance the purple fringing and near-infrared aberrations. The focal length f1 of the first lens L1, the focal length f3 of the third lens L3, and the focal length f6 of the sixth lens L6 respectively satisfy the following relationship with the effective focal length f of the fisheye lens: -8.1≤f1 / f≤-4.2; -5.4≤f3 / f≤-2; -2.7≤f6 / f≤-1.4. Through the combination of the above focal length segments, effective correction of aberrations can be achieved, so that the optical system meets the characteristics of high resolution, while meeting the day and night confocality and high and low temperature non-false focus. The focal length f2 of the second lens L2, the focal length f4 of the fourth lens L4, the focal length f5 of the fifth lens L5 and the focal length f7 of the seventh lens L7 respectively satisfy the following relationship with the effective focal length f of the fisheye lens: -3.8≤f2 / f≤-2.1; 2≤f4 / f≤4.1; 2.1≤f5 / f≤3; 1.7≤f7 / f≤2.8. The above-mentioned distribution of optical power can make the light pass through the optical system smoothly, thereby reducing the tolerance sensitivity of the entire optical system. The distance BFL from the center of the optical axis of the image side of the seventh lens L7 to the image plane and the total length TTL of the fisheye lens satisfy the following relationship: 0.19≤BFL / TTL≤0.32. Satisfying this relationship can make the lens meet the size requirements of mainstream cameras and the characteristics of miniaturization. The total length TTL of the fisheye lens and the effective focal length f satisfy the following relationship: 9.7≤TTL / f≤13.6. In this way, it is conducive to achieving higher resolution while ensuring a small volume. The curvature radius R11 of the image side surface of the fifth lens L5 and the curvature radius R12 of the object side surface of the sixth lens L6 satisfy the following relationship: 0.5≤|R12 / R11|≤3. By distributing the curvature radii in this way, the incident angle of the main light can be adjusted to further converge the light and ensure clear imaging of the optical system. The curvature radius R5 of the object side surface of the third lens L3 and the curvature radius R15 of the image side surface of the seventh lens L7 satisfy the following relationship: 2.5≤|R5 / R15|≤4.5. In this way, it is beneficial to effectively correct the distortion of the optical system.

[0041] In summary, the maximum aperture of the lens of the present invention can reach FNO2.0, and the imaging target surface can reach 1 / 3". The present invention adopts a mixed solution of glass lens and plastic lens, which can achieve confocality of visible light and infrared light, thereby effectively reducing the cost of the lens. In addition, the lens CRA≤22°, so it can be adapted to a variety of sensors, making the application prospects broad and the market competitiveness greater. The lens can also achieve non-defocusing in the temperature range of -40℃ to 80℃, so it can be used in different environments. In addition, the lens can also achieve image capture with an object field angle of 214° and F-theta distortion ≤38%.

[0042] The fisheye lens of the present invention is described in detail in three embodiments. In the following embodiments, S0, S1, ..., SN represent the surfaces of each optical element, the aperture may also be denoted as STO, the object plane may also be denoted as OBJ, and the image plane may also be denoted as IMA.

[0043] Parameters of various implementations that specifically meet the above conditional formula are shown in Table 1 below:

[0044]

[0045]

[0046] Table 1 The aspherical lens of the fisheye lens of the present invention satisfies the following formula:

[0047]

[0048] Where z is the axial distance from the surface to the vertex at a height h perpendicular to the optical axis along the optical axis; c represents the curvature at the vertex of the aspheric surface; k is the cone coefficient; A 4 , A 6 , A 8 , A 10 , A 12 , A 14 , A 16 ···represent the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, sixteenth-order···aspheric coefficients respectively.

[0049] First Implementation Method

[0050] See also Figures 1 to 6 In this embodiment, the parameters of the fisheye lens are: F#: 2.1; total lens length: 11.889 mm; field of view: 214°.

[0051] The relevant parameters of each lens of the fisheye lens of this embodiment include surface type, radius of curvature, thickness, refractive index of the material, and Abbe number, as shown in Table 2 below:

[0052]

[0053]

[0054] Table 2

[0055] The aspheric coefficients of each aspheric lens in this embodiment are shown in Table 3 below:

[0056]

[0057] Table 3

[0058] Where K is the quadratic constant of the surface, A4 , A 6 , A 8 , A 10 , A 12 They are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients respectively.

[0059] Second implementation method

[0060] See also Figures 7 to 12 In this embodiment, the parameters of the fisheye lens are: F#: 2.0; total lens length: 12.130 mm; field of view: 174°.

[0061] The relevant parameters of each lens of the fisheye lens of this embodiment include surface type, radius of curvature, thickness, refractive index of the material, and Abbe number, as shown in Table 4 below:

[0062]

[0063]

[0064] Table 4

[0065] The aspheric coefficients of each aspheric lens in this embodiment are shown in Table 5 below:

[0066]

[0067] Table 5

[0068] Where K is the quadratic constant of the surface, A 4 , A 6 , A 8 , A 10 , A 12 They are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients respectively.

[0069] The third implementation method

[0070] See also Figures 13 to 18 In this embodiment, the parameters of the fisheye lens are: F#: 2.0; total lens length: 12.067 mm; field of view: 180°.

[0071] The relevant parameters of each lens of the fisheye lens of this embodiment include surface type, radius of curvature, thickness, refractive index of the material, and Abbe number, as shown in Table 6 below:

[0072] Surface number Surface type R-Value thickness Refractive Index Abbe number S0(OBJ) Spherical Infinity Infinity S1 Spherical 8.716 0.578 1.79 48.2 S2 Spherical 3.260 1.474 S3 Aspheric 27.375 0.565 1.56 53.1 S4 Aspheric 1.520 1.585 S5 Aspheric -6.454 0.481 1.54 55.7 S6 Aspheric 2.026 0.070 S7 Spherical 2.082 1.814 1.78 25.7 S8 Spherical -5.561 0.364 S9(STO) Spherical Infinity 0.016 S10 Aspheric 7.713 0.703 1.54 57.0 S11 Aspheric -1.446 0.065 S12 Aspheric -1.179 0.401 1.66 20.4 S13 Aspheric 9.568 0.063 S14 Aspheric 2.208 1.185 1.53 56.1 S15 Aspheric -1.574 1.003 S16 Spherical Infinity 0.610 1.52 64.2 S17 Spherical Infinity 1.090 S18(IMA) Spherical Infinity - - -

[0073] Table 6

[0074] The aspheric coefficients of each aspheric lens in this embodiment are shown in Table 7 below:

[0075]

[0076]

[0077] Table 7

[0078] Where K is the quadratic constant of the surface, A 4 , A 6 , A 8 , A 10 , A 12 They are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients respectively.

[0079] The above is only one embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fisheye lens, comprising a first lens (L1) with negative focal power, a second lens (L2) with negative focal power, a third lens (L3) with negative focal power, a fourth lens (L4) with positive focal power, a stop (STO), a fifth lens (L5) with positive focal power, a sixth lens (L6) with negative focal power and a seventh lens (L7) with positive focal power, arranged in sequence from the object side to the image side along the optical axis, characterized in that: A distance d56 from the image side optical axis center of the fifth lens (L5) to the object side optical axis center of the sixth lens (L6) and a distance BFL from the image side optical axis center of the seventh lens (L7) to the image plane satisfy the following relationship: 0.01≤d56 / BFL≤0.06; A curvature radius R5 of the object side surface of the third lens (L3) and a curvature radius R15 of the image side surface of the seventh lens (L7) satisfy the following relationship: 2.5≤|R5 / R15|≤4.

5.

2. The fisheye lens according to claim 1, characterized in that: The first lens (L1) is convex-concave, the third lens (L3) is biconcave, and the sixth lens (L6) is biconcave; The sixth lens (L6) is an aspherical lens.

3. The fisheye lens according to claim 1, characterized in that: The second lens (L2) is convex-concave, the fourth lens (L4) is convex-concave or biconvex, the fifth lens (L5) is biconvex, and the seventh lens (L7) is biconvex.

4. The fisheye lens according to claim 1, characterized in that: The first lens (L1) is a spherical lens, the second lens (L2) is an aspherical lens, the third lens (L3) is an aspherical lens, the fourth lens (L4) is a spherical or aspherical lens, the fifth lens (L5) is a spherical or aspherical lens, and the seventh lens (L7) is an aspherical lens.

5. The fisheye lens according to any one of claims 1 to 4, characterized in that: The Abbe number of at least one of the fourth lens (L4) and the fifth lens (L5) is ≥50.

6. The fisheye lens according to any one of claims 1 to 4, characterized in that: The focal length f1 of the first lens (L1), the focal length f3 of the third lens (L3) and the focal length f6 of the sixth lens (L6) respectively satisfy the following relationship with the effective focal length f of the fisheye lens: -8.1≤f1 / f≤-4.2; -5.4≤f3 / f≤-2; -2.7≤f6 / f≤-1.

4.

7. The fisheye lens according to any one of claims 1 to 4, characterized in that: The focal length f2 of the second lens (L2), the focal length f4 of the fourth lens (L4), the focal length f5 of the fifth lens (L5) and the focal length f7 of the seventh lens (L7) respectively satisfy the following relationship with the effective focal length f of the fisheye lens: -3.8≤f2 / f≤-2.1; 2≤f4 / f≤4.1; 2.1≤f5 / f≤3; 1.7≤f7 / f≤2.

8.

8. The fisheye lens according to any one of claims 1 to 4, characterized in that: A distance BFL from the center of the image-side optical axis of the seventh lens (L7) to the image plane and a total length TTL of the fisheye lens satisfy the following relationship: 0.19≤BFL / TTL≤0.

32.

9. The fisheye lens according to any one of claims 1 to 4, characterized in that: The total length TTL and the effective focal length f of the fisheye lens satisfy the following relationship: 9.7≤TTL / f≤13.

6.

10. The fisheye lens according to any one of claims 1 to 4, characterized in that: A curvature radius R11 of the image side surface of the fifth lens (L5) and a curvature radius R12 of the object side surface of the sixth lens (L6) satisfy the following relationship: 0.5≤|R12 / R11|≤3.

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