A day and night confocal optical lens and imaging device

Abstract

The present invention discloses a day-night confocal optical lens and an imaging device, comprising a first lens group with positive focal power, an aperture stop, a second lens group with negative focal power, and a third lens group with positive focal power, which are arranged in sequence from an object plane to an image plane along an optical axis. The third lens group moves along the optical axis during focusing. The day-night confocal optical lens satisfies the following conditional formulas: 33≤F1*F3 / F2≤61; 4.5<F 12 / F≤20; wherein F1, F2 and F3 represent the focal lengths of the first lens group, the second lens group and the third lens group respectively, F represents the focal length of the day and night confocal optical lens, F 12 represents the combined focal length of the first lens group and the second lens group; the beneficial effect of the present invention is to provide a day and night confocal optical lens and an imaging device which can clearly image in both visible spectrum and near infrared spectrum and have excellent imaging performance. Moreover, the number of lenses included is small and the cost is low.

Description

Technical Field

[0001] The invention relates to the field of imaging equipment, in particular to a day-night confocal optical lens and imaging equipment. Background Art

[0002] With the construction of safe projects, people's awareness of safety precautions has been continuously improved, and nighttime monitoring has gradually been taken seriously by people. Day and night confocal imaging equipment refers to an imaging system that can clearly image both during the day and at night. The working spectrum of the imaging system during the day is the visible spectrum, and the working spectrum at night is the near-infrared spectrum; usually, because the refractive index changes with the wavelength, the image plane position of the visible light band and the near-infrared band is inconsistent, resulting in blurred imaging, poor imaging quality and other problems. Therefore, the day and night confocal imaging equipment requires that the optical lens used with it can clearly image in both the visible and near-infrared spectra. In order to achieve monitoring during the day and at night, the design of the lens is required to be optimized in both the visible light band and the near-infrared band. For existing day and night confocal imaging equipment, most of the existing technologies contain multiple aspherical lenses, resulting in a high cost of the imaging equipment. Summary of the invention

[0003] The object of the present invention is to provide a day and night confocal optical lens and imaging device to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A day-night confocal optical lens comprises a first lens group with positive focal power, an aperture stop, a second lens group with negative focal power, and a third lens group with positive focal power, which are sequentially arranged along the optical axis from the object plane to the image plane, wherein the third lens group moves along the optical axis during focusing, and the day-night confocal optical lens satisfies the following conditional formula:

[0006] 33≤F1*F3 / F2≤61 (1);

[0007] 4.5<F 12 / F≤20 (2);

[0008] Wherein F1, F2 and F3 represent the focal lengths of the first lens group, the second lens group and the third lens group respectively, F represents the focal length of the day and night confocal optical lens, and F 12 represents the combined focal length of the first lens group and the second lens group.

[0009] As a further solution of the present invention: the first lens group and the second lens group are fixed relative to the image plane.

[0010] As a further solution of the present invention: the first lens group is composed of at least a first positive refractive element, a second positive refractive element, and a refractive element including a negative refractive element, the negative refractive element is arranged on the image side of the first lens group, the second positive refractive element is arranged between the first positive refractive element and the negative refractive element, the first positive refractive element is a first positive lens, the second positive refractive element is a second positive lens, and the negative refractive element is a negative lens.

[0011] As a further solution of the present invention: the day and night confocal optical lens satisfies the following conditional formula:

[0012] 2.0<f1 / v1+f2 / v2+f3 / v3<2.4 (3);

[0013] Wherein f1 and v1 represent the focal length and Abbe number of the first positive lens of the first lens group, respectively; wherein f1 and v2 represent the focal length and Abbe number of the second positive lens of the first lens group, respectively; wherein f3 and v3 represent the focal length and Abbe number of the negative lens configured on the image side of the first lens group, respectively.

[0014] As a further solution of the present invention: it also includes a lens barrel, which is used to encapsulate the first lens group, the aperture stop, the second lens group and the third lens group.

[0015] As a further solution of the present invention: the lens barrel is provided with a thread or a buckle on the side close to the third lens group for connection with an external thread or buckle.

[0016] As another solution of the present invention: an imaging device includes a solid-state image sensor and a camera housing, wherein the solid-state image sensor is arranged in the camera housing, and also includes any one of the above-mentioned day and night confocal optical lenses, wherein the day and night confocal optical lens cooperates with the camera housing.

[0017] Compared with the prior art, the invention has the beneficial effects of providing a day-night confocal optical lens that can clearly image in both the visible spectrum and the near-infrared spectrum, realizing monitoring during the day and at night, and having excellent imaging performance in the visible light band and the near-infrared band. It is applied to a variety of monitoring imaging fields, and the number of lenses involved is small, and the cost of the imaging equipment is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a cross-sectional view along the optical axis of the day and night confocal optical lens of Example 1.

[0019] Figure 2 The figure is a schematic diagram of the structure of a day and night confocal optical lens and imaging equipment.

[0020] Figure 3Graphs showing various aberrations of the day-night confocal optical lens of Example 1 in the infinity focused state in the visible light band.

[0021] Figure 3 A, B, and C are respectively the spherical aberration diagram, astigmatism diagram, and distortion diagram of the day and night confocal optical lens of Example 1 in the infinity focused state in the visible light band.

[0022] Figure 4 Graphs showing various aberrations of the day-night confocal optical lens of Example 1 in the closest focusing state in the visible light band.

[0023] Figure 4 A, B, and C are respectively the spherical aberration diagram, the astigmatism diagram, and the distortion diagram of the day and night confocal optical lens of Example 1 in the closest focusing state in the visible light band.

[0024] Figure 5 Graphs showing various aberrations of the day-night confocal optical lens of Example 1 in the infinity focused state in the near-infrared band.

[0025] Figure 5 A, B, and C are respectively the spherical aberration diagram, astigmatism diagram, and distortion diagram of the day and night confocal optical lens of Example 1 in the infinity focused state in the near-infrared band.

[0026] Figure 6 This is a cross-sectional view along the optical axis of the day and night confocal optical lens of Example 2.

[0027] Figure 7 Graphs showing various aberrations of the day-night confocal optical lens of Example 2 in the infinity focused state in the visible light band.

[0028] Figure 7 A, B, and C are respectively the spherical aberration diagram, astigmatism diagram, and distortion diagram of the day and night confocal optical lens of Example 2 in the infinity focused state in the visible light band.

[0029] Figure 8 Graphs showing various aberrations of the day-night confocal optical lens of Example 2 in the closest focusing state in the visible light band.

[0030] Figure 8 A, B, and C are respectively the surface aberration diagram, astigmatism diagram, and distortion diagram of the day and night confocal optical lens of Example 2 in the closest focusing state in the visible light band.

[0031] Fig. 9 Graphs showing various aberrations of the day-night confocal optical lens of Example 2 in the infinity focused state in the near-infrared band.

[0032] Fig. 9 A, B, and C are respectively the surface aberration diagram, astigmatism diagram, and distortion diagram of the day and night confocal optical lens of Example 2 in the infinity focused state in the near-infrared band.

[0033] Fig.10 This is a cross-sectional view along the optical axis of the day and night confocal optical lens of Example 3.

[0034] Fig.11 Graphs showing various aberrations of the day-night confocal optical lens of Example 3 in the infinity focused state in the visible light band.

[0035] Fig.11 A, B, and C are respectively the spherical aberration diagram, astigmatism diagram, and distortion diagram of the day and night confocal optical lens of Example 3 in the infinity focused state in the visible light band.

[0036] Fig.12 Graphs showing various aberrations of the day-night confocal optical lens of Example 3 in the closest focusing state in the visible light band.

[0037] Fig.12 A, B, and C are respectively the surface aberration diagram, astigmatism diagram, and distortion diagram of the day and night confocal optical lens of Example 3 in the closest focusing state in the visible light band.

[0038] Fig.13 The aberration diagrams of the day and night confocal optical lens of Example 3 in the infinity focused state in the near-infrared band.

[0039] Fig.13 A, B, and C are respectively the surface aberration diagram, astigmatism diagram, and distortion diagram of the day and night confocal optical lens of Example 3 in the infinity focused state in the near-infrared band.

[0040] In the accompanying drawings: 1-day and night confocal optical lens, 2-lens barrel, 3-solid-state image sensor, 20-camera housing, G1-first lens group, G2-second lens group, G3-third lens group, L1-first positive lens, L2-second positive lens, L3-negative lens, IMG-imaging surface, A-spherical aberration diagram, B-astigmatism diagram, C-distortion diagram.

[0041] In the attached figure: d line is equal to 587nm, c line is equal to 656nm, g line is equal to 435nm, S and T represent the sagittal and meridian directions respectively. DETAILED DESCRIPTION

[0042] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present embodiment disclosure as detailed in the appended claims.

[0043] In the following lens data, the refractive index and focal length are the values ​​of the d-line; among them, in the optical lens related data, the unit of length is mm, and its unit will be omitted.

[0044] It is important to note that the symbols used in the table and in the following description are as follows:

[0045] "Si" indicates the surface number; "Ri" is the radius of curvature; "di" is the on-axis surface distance between the i-th surface and the i+1-th surface; "nd" is the refractive index; "vd" is the Abbe number; "Fno" is the F number; and "ω" is the half field angle. Regarding the surface number, "ASP" indicates that the surface is an aspherical surface, and regarding the radius of curvature, "∞" indicates that the surface is a flat surface, "INF" indicates macro, "MOD" indicates modified adopted value, and "RED" indicates focus adjustment.

[0046] Example 1

[0047] See also Figures 1 to 5 In Embodiment 1 of the present invention, a day-night confocal optical lens comprises a first lens group G1 with positive focal power, an aperture stop ST, a second lens group G2 with negative focal power, and a third lens group G3 with positive focal power, which are sequentially arranged along the optical axis from the object plane to the image plane. The third lens group G3 moves along the optical axis during focusing. The day-night confocal optical lens satisfies the following conditional formula:

[0048] 33≤F1*F3 / F2≤61 (1);

[0049] 4.5<F 12 / F≤20 (2);

[0050] Wherein F1, F2 and F3 represent the focal lengths of the first lens group G1, the second lens group G2 and the third lens group G3 respectively, F represents the focal length of the day and night confocal optical lens 1, and F 12 represents the combined focal length of the first lens group G1 and the second lens group G2.

[0051] Specifically, conditional expression (1) specifies the focal power ratio between the three lens groups, achieving miniaturization while maintaining good imaging performance; conditional expression (2) specifies the ratio range between the combined focal length of the first lens group G1 and the second lens group G2 and the focal length of the optical lens, achieving good imaging performance in the entire focusing range; an aperture stop is arranged between the first lens group G1 and the second lens group G2, so that the entrance pupil is closer to the object side, and the aperture of the first lens group G1 is small.

[0052] See also Figure 1 In Example 1 of the present invention, the first lens group G1 and the second lens group G2 are fixed relative to the image plane.

[0053] Specifically, the first lens group G1 and the second lens group G2 do not move during focusing, and the third lens group G3 moves along the optical axis from the imaging surface IMG to the object side to perform focusing from the infinity focus state to the closest focus state; preferably, an aperture stop is arranged between the first lens group G1 and the second lens group G2. In this way, the incident pupil is closer to the object side, and the diameter of the first lens group G1 is small. If the aperture stop is arranged after the second lens group G2, the incident pupil is too close to the image side, so the diameter of the first lens group G1 has to be increased. If the diameter of the lens is enlarged, the weight of the lens also increases.

[0054] See also Figure 1 In Embodiment 1 of the present invention, the first lens group G1 is composed of at least a first positive refractive element, a second positive refractive element and a negative refractive element, the first positive refractive element is a first positive lens L1, the second positive refractive element is a second positive lens L2, the negative refractive element is a negative lens L3, the negative lens L3 is arranged on the image side of the first lens group G1, and the second positive lens L2 is arranged between the first positive lens L1 and the negative lens L3.

[0055] See also Figure 1-5 , Table 1, Table 2, Table 3, in Example 1 of the present invention, the day and night confocal optical lens satisfies the following conditional formula:

[0056] 2.0<f1 / v1+f2 / v2+f3 / v3<2.4 (3);

[0057] Wherein f1 and v1 respectively represent the focal length and Abbe number of the positive lens L1 of the first lens group G1, wherein f2 and v2 respectively represent the focal length and Abbe number of the positive lens L2 of the first lens group G1, wherein f3 and v3 respectively represent the focal length and Abbe number of the negative lens L3 arranged on the image side of the first lens group G1.

[0058] Specifically, analyze Figure 3 , 4 , 5, the spherical aberration diagram A, the astigmatism diagram B and the distortion diagram C show that the conditional formula (3) specifies the sum of the chromatic aberrations produced by each lens in the first lens group G1. By satisfying the conditional formula (3), good imaging performance can be maintained in both the visible light band and the near-infrared band. If the conditional formula (3) is at the lower limit, the sum of the chromatic aberrations of the first lens group G1 in the visible light band is too small, and a secondary spectrum is produced in the near-infrared band, resulting in poor imaging quality in the near-infrared band; if the conditional formula (3) is exceeded, the sum of the chromatic aberrations of the first lens group G1 in the visible light band is too large, resulting in poor imaging quality in the visible light band.

[0059] See also Figure 1 , 2In Embodiment 1 of the present invention, a lens barrel 2 is further included, wherein the lens barrel 2 is used to encapsulate the first lens group G1, the aperture stop ST, the second lens group G2 and the third lens group G3. The first lens group G1 and the second lens group G2 are fixed, and the third lens group G3 moves along the optical axis. The focal length is adjusted by adjusting the third lens group G3, thereby obtaining a good imaging effect.

[0060] See also Figure 2 In Embodiment 1 of the present invention, the lens barrel 2 is provided with a thread or a buckle on the side close to the third lens group G3 for connection with an external thread or a buckle connection, and a more convenient buckle connection method is usually adopted.

[0061] See also Figures 1-2 In embodiment 1 of the present invention, an imaging device includes a solid-state image sensor 3 and a camera housing 20, wherein the solid-state image sensor 3 is arranged in the camera housing 20, and also includes any one of the above-mentioned day and night confocal optical lenses 1, wherein the day and night confocal optical lens 1 cooperates with the camera housing 20.

[0062] Specifically, after the light passes through the day and night confocal optical lens 1 , an image is formed on the solid-state image sensor 3 in the camera housing 20 .

[0063] In the following description of Example 1, "D(1)" indicates that the thickness (di) is 15.86 and 14.52 in the "INF" and "MOD" states, respectively, and "D(2)" indicates that the thickness (di) is 27.11 and 28.45 in the "INF" and "MOD" states, respectively. Various numerical data about the day and night confocal optical lens 1 of Example 1 are shown below.

[0064] Table 1 shows the basic data of the day and night confocal optical lens 1 in Example 1.

[0065]

[0066]

[0067] Table 2 is the focusing data of the day and night confocal optical lens 1 in Example 1.

[0068]

[0069]

[0070] Example 2

[0071] Figure 6This is a cross-sectional view along the optical axis of the day-night confocal optical lens of Example 2. The optical lens is configured such that the following lens groups are arranged in order from the object side of the figure: a first lens group G1 with positive refractive power; a second lens group G2 with negative refractive power; and a third lens group G3 with positive refractive power. In addition, an aperture stop ST with a predetermined aperture is arranged between the first lens group G1 and the second lens group G2.

[0072] The first lens group G1 is composed of a positive lens L1, a second positive lens L2, and a negative lens L3 arranged in order from the object side. In addition, the first lens group G1 and the second lens group G2 are fixed and do not move during focusing, and the third lens group G3 moves along the optical axis from the imaging plane IMG to the object side to perform focusing from the infinity focus state to the closest focus state.

[0073] analyze Figure 7 , 8 , 9, the spherical aberration diagram A, the astigmatism diagram B and the distortion diagram C show that the conditional formula (3) specifies the sum of the chromatic aberrations produced by each lens in the first lens group G1. By satisfying the conditional formula (3), good imaging performance can be maintained in both the visible light band and the near-infrared band. If the conditional formula (3) is at the lower limit, the sum of the chromatic aberrations of the first lens group G1 in the visible light band is too small, and a secondary spectrum is produced in the near-infrared band, resulting in poor imaging quality in the near-infrared band; if the conditional formula (3) is exceeded, the sum of the chromatic aberrations of the first lens group G1 in the visible light band is too large, resulting in poor imaging quality in the visible light band.

[0074] In the following description of Example 2, "D(1)" indicates that the thickness (di) is 16.62 and 15.27 in the "INF" and "MOD" states, respectively, and "D(2)" indicates that the thickness (di) is 18.87 and 20.22 in the "INF" and "MOD" states, respectively.

[0075] Various numerical data regarding the day and night confocal optical lens of Example 2 are shown below.

[0076] Table 3 is the basic data of the day and night confocal optical lens 1 in Example 2

[0077]

[0078]

[0079] Table 4 is the focusing data of the day and night confocal optical lens in Example 2.

[0080]

[0081] Example 3

[0082] Fig.10 This is a cross-sectional view along the optical axis of the day-night confocal optical lens of Example 3. The optical lens is configured such that the following lens groups are arranged in order from the object side of the figure: a first lens group G1 with positive refractive power; a second lens group G2 with negative refractive power; and a third lens group G3 with positive refractive power. In addition, an aperture stop ST with a predetermined aperture is arranged between the first lens group G1 and the second lens group G2.

[0083] The first lens group G1 is composed of a positive lens L1, a second positive lens L2, and a negative lens L3 arranged in order from the object side. In addition, the first lens group G1 and the second lens group G2 are fixed and do not move during focusing, and the third lens group G3 moves along the optical axis from the imaging plane IMG to the object side to perform focusing from the infinity focus state to the closest focus state.

[0084] analyze Fig.11 , 12 , 13, the spherical aberration diagram A, the astigmatism diagram B and the distortion diagram C show that the conditional formula (3) specifies the sum of the chromatic aberrations produced by each lens in the first lens group G1. By satisfying the conditional formula (3), good imaging performance can be maintained in both the visible light band and the near-infrared band. If the conditional formula (3) is within the lower limit, the sum of the chromatic aberrations of the first lens group G1 in the visible light band is too small, and a secondary spectrum is produced in the near-infrared band, resulting in poor imaging quality in the near-infrared band; if the conditional formula (3) is exceeded, the sum of the chromatic aberrations of the first lens group G1 in the visible light band is too large, resulting in poor imaging quality in the visible light band.

[0085] In the following description of Example 3, "D(1)" indicates that the thickness (di) is 9.14 and 7.82 in the "INF" and "MOD" states, respectively, and "D(2)" indicates that the thickness (di) is 23.96 and 25.28 in the "INF" and "MOD" states, respectively.

[0086] Various numerical data regarding the day and night confocal optical lens of Example 3 are shown below.

[0087] Table 5 shows the basic data of the day and night confocal optical lens 1 of Example 3.

[0088]

[0089]

[0090] Table 6 is the focusing data of the day and night confocal optical lens in Example 3.

[0091]

[0092]

[0093] Table 7 shows the conditional data of Example 1, Example 2 and Example 3.

[0094] serial number Example 1 Example 2 Example 3 Conditional expression (1) 55 33 61 Conditional expression (2) 6.6 4.6 19.8 Conditional expression (3) 2.12 2.35 2.13

[0095] The data in the above table are only exemplary. The parameters of each lens are not limited to the above examples. Similar effects can be achieved by adjusting the values ​​of each parameter.

[0096] The working principle of the present invention is: in addition to meeting the requirements of long focal length, large aperture and miniaturization, the consistency of the image plane in the visible light band and the near-infrared band is achieved in the entire focusing range by reasonably configuring the optical focal length between each lens group, reasonably setting the aperture stop position, and reasonably selecting the focusing lens group, so as to achieve good imaging performance in both the visible light band and the near-infrared band.

[0097] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the disclosure in the specification and examples. This application is intended to cover any variations, uses or adaptations of the present disclosure, which follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the claims.

[0098] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A day and night confocal optical lens, characterized in that: The invention comprises a first lens group with positive focal power, an aperture stop, a second lens group with negative focal power, and a third lens group with positive focal power, which are sequentially arranged along the optical axis from the object plane to the image plane, wherein the third lens group moves along the optical axis during focusing, and the day-night confocal optical lens satisfies the following conditional formula: 33≤F1*F3 / F2≤61 (1); 4.5<F 12 / F≤20 (2); Wherein F1, F2 and F3 represent the focal lengths of the first lens group, the second lens group and the third lens group respectively, F represents the focal length of the day and night confocal optical lens, and F 12 represents the combined focal length of the first lens group and the second lens group; Wherein, the optical lens is provided with three lens groups; The first lens group is composed of refractive elements including a first positive refractive element, a second positive refractive element, and a negative refractive element, the negative refractive element is arranged on the image side of the first lens group, the second positive refractive element is arranged between the first positive refractive element and the negative refractive element, the first positive refractive element is a first positive lens, the second positive refractive element is a second positive lens, and the negative refractive element is a negative lens; The day and night confocal optical lens meets the following conditional formula: 2.0<f1 / v1+f2 / v2+f3 / v3<2.4 (3); Wherein f1 and v1 represent the focal length and Abbe number of the first positive lens of the first lens group, respectively; f2 and v2 represent the focal length and Abbe number of the second positive lens of the first lens group, respectively; and f3 and v3 represent the focal length and Abbe number of the negative lens disposed on the image side of the first lens group, respectively; Also included is a lens barrel, which is used to encapsulate the first lens group, the aperture stop, the second lens group and the third lens group.

2. The day and night confocal optical lens according to claim 1, characterized in that: The first lens group and the second lens group are fixed relative to the image plane.

3. The day and night confocal optical lens according to claim 1, characterized in that: The lens barrel is provided with a thread or a buckle on the side close to the third lens group, which is used for connecting with an external thread or buckle.

4. An imaging device, comprising a solid-state image sensor and a camera housing, wherein the solid-state image sensor is disposed in the camera housing, characterized in that: It also includes the day and night confocal optical lens according to any one of claims 1 to 3, wherein the day and night confocal optical lens cooperates with the camera housing.

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