Far infrared optical lens and image acquisition equipment

Abstract

The utility model relates to the technical field of optical imaging, in particular to a far infrared optical lens and image acquisition equipment. The far infrared optical lens comprises a first lens, a second lens, a diaphragm and a third lens which are sequentially arranged along a light incidence direction, wherein the first lens is a positive meniscus lens, the second lens is a negative meniscus lens, and the third lens is a positive meniscus lens; the first lens, the second lens and the third lens are all aspherical mirrors; the first lens, the second lens and the third lens are made of far infrared glass; and the far infrared optical lens can be used for imaging in a wave band of 7-14 microns. The utility model can reduce the number of lenses, reduce the size of the lenses and enhance the imaging quality.

Description

Technical Field

[0001] The utility model relates to the technical field of optical imaging, in particular to a far-infrared optical lens and image acquisition equipment. Background Art

[0002] Traditional far-infrared lenses may require more lenses to correct various optical distortions, resulting in a complex optical system structure and increased difficulty in assembly and calibration. Moreover, more lenses and larger size will result in a larger overall weight and volume of the far-infrared lens, which is not conducive to some applications that require lightness and compactness. Utility Model Content

[0003] The technical problem to be solved by the embodiments of the utility model is to provide a far-infrared optical lens and an image acquisition device to solve the problems of complex optical system structure and large overall weight and volume of the lens in the prior art.

[0004] The utility model discloses a far-infrared optical lens, comprising: a first lens, a second lens, a diaphragm and a third lens which are sequentially arranged along the incident direction of light;

[0005] Wherein, the first lens is a positive meniscus lens, the second lens is a negative meniscus lens, and the third lens is a positive meniscus lens; the first lens, the second lens and the third lens are all aspherical lenses;

[0006] The materials of the first lens, the second lens and the third lens are far-infrared glass;

[0007] The far-infrared optical lens can form images in the 7um to 14um band.

[0008] Optionally, the object side surface of the first lens is convex and the image side surface is concave; the object side surface of the second lens is concave and the image side surface is convex; the object side surface of the third lens is convex and the image side surface is concave.

[0009] Optionally, the first lens satisfies the following conditions:

[0010] R1=5.63mm, R2=6.85mm, Nd=4.0, D=0.90mm; Conic1=-0.05;

[0011] Conic2 = 0.136;

[0012] The second lens meets the following conditions:

[0013] R1=-10.48mm, R2=-17.52mm, Nd=3.3, D=1.6mm; Conic1=2.225, Conic2=0.8;

[0014] The third lens meets the following conditions:

[0015] R1=8.1mm, R2=19.01mm, Nd=4.0, D=1.03mm; Conic1=5.85, Conic2=95.81;

[0016] Among them, R1 represents the curvature radius of the object side, R2 represents the curvature radius of the image side, Nd represents the refractive index, D represents the center thickness, and Conic1 and Conic2 represent the parameters of the aspherical surface.

[0017] Optionally, the center distance between the first lens and the second lens is 0.89 mm;

[0018] The center distance between the second lens and the aperture is 1.32 mm;

[0019] The center distance between the aperture and the third lens is 0.08 mm.

[0020] Optionally, the lens focal lengths of the first lens, the second lens and the third lens and the system focal length of the far-infrared optical lens meet the following conditions:

[0021] 1.4 <f1 / f<1.6,-2.5<f2 / f<-3.2,0.5<f3 / f<1.5;

[0022] Among them, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f is the system focal length.

[0023] Optionally, a ratio of the system image height of the far-infrared optical lens to the system focal length is greater than or equal to 0.885.

[0024] Optionally, the refractive indexes of the first lens, the second lens and the third lens are all greater than or equal to 2.0.

[0025] Optionally, the F number of the far-infrared optical lens is less than or equal to 1.2.

[0026] The utility model also discloses an image acquisition device, comprising the far-infrared optical lens and the far-infrared imaging sensor as described above, wherein the far-infrared thermal imaging sensor is located at the light-emitting side of the far-infrared optical lens.

[0027] Optionally, a ratio of a distance from the front surface of the first lens to an imaging surface of the far-infrared imaging sensor to a system focal length of the far-infrared optical lens is greater than or equal to 1.5 and less than or equal to 2.0.

[0028] Compared with the prior art, the far-infrared optical lens provided by the embodiment of the utility model has the following beneficial effects:

[0029] The positive meniscus lens and the negative meniscus lens are arranged alternately, which can correct the optical distortion introduced by each other, such as spherical aberration and astigmatism, thereby improving the imaging quality of the entire system. Placing the aperture between the second lens and the third lens can effectively control the propagation of light, reduce optical interference and defocusing, and help simplify the design of the optical system. The first lens, the second lens, and the third lens are all aspherical lenses. The aspherical lens design can reduce the number of lenses, reduce the size of the lenses, enhance the imaging quality, improve the resolution, and improve the thermal imaging sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The technical solution of the utility model will be further described in detail below with reference to the accompanying drawings and embodiments, in which:

[0031] Figure 1 It is a structural schematic diagram of an embodiment of the far-infrared optical lens provided by the utility model;

[0032] Figure 2 This is a schematic diagram of the optical path of the far-infrared optical lens provided by the utility model;

[0033] Figure 3 This is a structural schematic diagram of an embodiment of the image acquisition device provided by the utility model

[0034] Figure 4 It is a schematic diagram of the MTF of the far-infrared optical lens provided by the utility model;

[0035] Figure 5 It is a point spread diagram of the far-infrared optical lens provided by the utility model.

[0036] The reference numerals in the figures are:

[0037] 1. First lens; 2. Second lens; 3. Aperture; 4. Third lens; 5. Far-infrared imaging sensor. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Now, in conjunction with the accompanying drawings, a preferred embodiment of the present utility model is described in detail.

[0039] The utility model embodiment provides a far-infrared optical lens, such as Figure 1 As shown, the far-infrared optical lens comprises a first lens 1, a second lens 2, an aperture 3 and a third lens 4 arranged in sequence along the incident direction of the light. The first lens 1 is a positive meniscus lens, the second lens 2 is a negative meniscus lens, and the third lens 4 is a positive meniscus lens. Figure 2 , Figure 2 It is a schematic diagram of the optical path of the far-infrared optical lens provided by the utility model.

[0040] Among them, the first lens 1 of the positive meniscus lens is used to correct spherical aberration, which can improve the imaging quality. The second lens of the negative meniscus lens is used to correct some optical distortions introduced by the positive meniscus lens, such as astigmatism and spherical aberration. It can help further optimize the imaging quality. The aperture 3 is used to limit the light beam passing through the optical system, controlling the resolution and optical defocus of the system. It can help reduce the defocus of the light, improve the imaging quality, and avoid some optical interference. The third lens 4 of the positive meniscus lens is used to further optimize the optical path, correct the residual optical distortion, and improve the imaging performance of the entire system.

[0041] By arranging the positive meniscus lens and the negative meniscus lens alternately, the optical distortion introduced, such as spherical aberration and astigmatism, can be mutually corrected, thereby improving the imaging quality of the entire system. The combination of the positive meniscus lens and the negative meniscus lens can help control chromatic aberration, further improve the imaging quality, and make the lens have better color performance in the far infrared band. Placing the aperture between the second lens 2 and the third lens 4 can effectively control the propagation of light, reduce optical interference and defocusing, help simplify the design of the optical system, and reduce the need for other optical elements.

[0042] The design of the first lens 1, the second lens 2, the aperture 3 and the third lens 4 in the utility model helps to simplify the optical system structure of the far-infrared optical lens, reduce the number of lenses, and maintain the system performance and imaging quality of the far-infrared optical lens. By carefully designing the arrangement sequence of the lenses, the system can be simplified without sacrificing function and performance, and the stability and reliability of the system can be improved.

[0043] The first lens 1, the second lens 2 and the third lens 4 are all aspherical lenses. The aspherical lens design can improve the transmission efficiency and sensitivity of the lens in the far-infrared band, thereby enhancing the thermal imaging sensing capability. This design can make the lens perform better in thermal imaging applications and improve the accuracy and reliability of detection and identification. The aspherical lens design can more effectively utilize the optical path space, reduce redundant components, and reduce the weight and volume of the entire lens. This makes the lens lighter, more compact, and more suitable for application scenarios that require lightweight and miniaturization. The aspherical lens design can realize complex optical functions on a single lens, such as correcting multiple optical distortions, controlling chromatic aberration, etc. Therefore, compared with traditional spherical lenses, the aspherical lens design can reduce the number of lenses required and simplify the structure of the entire optical system.

[0044] The materials of the first lens 1, the second lens 2 and the third lens 4 are far-infrared glass. Far-infrared glass is a special glass material with excellent transmission characteristics in the far-infrared spectral range. This glass is usually designed and manufactured for optical imaging and sensing applications in the far-infrared band (usually in the range of 7 microns to 14 microns).

[0045] The material properties of far-infrared glass enable the first lens 1, the second lens 2 and the third lens 4 to effectively transmit infrared light in the 7um to 14um band, so that the far-infrared optical lens is suitable for optical imaging needs in this band. In addition, far-infrared glass generally has good thermal stability and can maintain its optical properties in high temperature environments, making it suitable for thermal imaging and other high-temperature applications.

[0046] In one embodiment, the object side surface of the first lens 1 is convex and the image side surface is concave; the object side surface of the second lens 2 is concave and the image side surface is convex; the object side surface of the third lens 4 is convex and the image side surface is concave. The convex object side surface of the first lens 1 can make it easier for the lens to focus incident light, reduce distortion such as spherical aberration, and improve imaging quality. The concave image side surface can better control the defocusing properties of the lens, making it easier for the lens to focus light to a focal point, reducing aberrations and improving imaging clarity.

[0047] The concave surface of the object side of the second lens 2 can better control the direction and focusing properties of the incident light, help reduce distortion such as spherical aberration, and improve the accuracy of imaging. The convex surface of the image side can make it easier for the lens to focus light, reduce aberrations, and improve the clarity and accuracy of imaging.

[0048] The object side surface of the third lens 4 is convex, which can make it easier for the lens to focus incident light, reduce distortion such as spherical aberration, and improve image quality. The image side surface is concave, which can better control the defocusing properties of the lens, help focus light to the focal point, reduce aberrations, and improve the clarity of the image.

[0049] In one implementation scenario, the first lens 1 satisfies the following conditions:

[0050] R1=5.63mm, R2=6.85mm, Nd=4.0, D=0.90mm; Conic1=-0.05;

[0051] Conic2 = 0.136;

[0052] The second lens 2 meets the following conditions:

[0053] R1=-10.48mm, R2=-17.52mm, Nd=3.3, D=1.6mm; Conic1=2.225, Conic2=0.8;

[0054] The third lens 4 satisfies the following conditions:

[0055] R1=8.1mm, R2=19.01mm, Nd=4.0, D=1.03mm; Conic1=5.85, Conic2=95.81;

[0056] Among them, R1 represents the radius of curvature of the object side, R2 represents the radius of curvature of the image side, Nd represents the refractive index, D represents the center thickness, and Conic1 and Conic2 represent the parameters of the aspheric surface. When Conic1 is a negative value, it usually means that the aspheric lens has a hyperbolic shape. Conic1 is one of the parameters that describe the surface shape of an aspheric lens. It usually represents the conic constant of the aspheric surface and is a dimensionless value. The value of Conic1 can be negative, zero, or positive, and different values ​​represent different surface shapes. The common value range is from -1 to +1. When Conic1 is a negative value, the aspheric lens has a hyperbolic shape. When Conic1 is zero, the aspheric lens has a flat or spherical shape. When Conic1 is a positive value, the aspheric lens has an ellipsoidal shape. Conic2 is another parameter that describes the surface shape of an aspheric lens. It is often used to more accurately define the shape of an aspheric surface, especially when a more complex curvature is required. The value of Conic2 can also be negative, zero, or positive, and different values ​​represent different surface shapes.

[0057] In one implementation scenario, the center spacing between the first lens 1 and the second lens 2 is 0.89 mm; this is to achieve specific aberration control and focal length adjustment. A smaller spacing can help reduce certain aberrations and affect the focal length of the system. The center spacing between the second lens 2 and the aperture 3 is 1.32 mm; a larger spacing can help limit the size and direction of the incident light, reduce scattering and improve image quality. The center spacing between the aperture 3 and the third lens 4 is 0.08 mm, and the smaller spacing may be to control the light propagation of the system to avoid interference and scattering.

[0058] In one implementation scenario, the lens focal lengths of the first lens 1, the second lens 2, and the third lens 4 and the system focal length of the far-infrared optical lens meet the following conditions:

[0059] 1.4 <f1 / f<1.6

[0060] -2.5 <f2 / f<-3.2

[0061] 0.5 <f3 / f<1.5

[0062] Wherein, f1 is the focal length of the first lens 1, f2 is the focal length of the second lens 2, f3 is the focal length of the third lens 4, and f is the system focal length. Setting the ratio range of the lens focal length to the system focal length can ensure a suitable relationship between the system focal length and the lens focal length. This helps to control the focal length of the system to adapt it to specific imaging requirements.

[0063] In one implementation scenario, the ratio of the system image height and the system focal length of the far-infrared optical lens is greater than or equal to 0.885. In one implementation scenario, the refractive index of the first lens 1, the second lens 2, and the third lens 4 is greater than or equal to 2.0. Materials with a refractive index greater than 2.0 generally have a higher optical density and produce a stronger refraction and focusing effect on light. A higher refractive index means that the propagation of light in each lens will be more curved, which can help the light focus or scatter better, thereby achieving a more precise imaging effect. Lenses with a refractive index generally have better optical properties, such as higher dispersion performance and smaller aberrations, which help reduce distortion and color deviation in imaging.

[0064] The F number of the far infrared optical lens is less than or equal to 1.2. An optical system with an F number less than or equal to 1.2 usually has a larger aperture opening, which helps to improve the system's light throughput and light collection capabilities.

[0065] Please refer to Figure 3 , Figure 3 The image acquisition device of the present invention comprises a far-infrared optical lens and a far-infrared imaging sensor 5 , wherein the far-infrared thermal imaging sensor 5 is located at the light-emitting side of the far-infrared optical lens, that is, at the light-emitting side of the third lens 4 .

[0066] The ratio of the distance from the front surface of the first lens 1 to the imaging plane of the far-infrared imaging sensor 5 to the system focal length of the far-infrared optical lens is greater than or equal to 1.5 and less than or equal to 2.0. The ratio of the distance from the front surface of the first lens 1 to the imaging plane of the far-infrared imaging sensor 5 to the system focal length of the far-infrared optical lens is between 1.5 and 2.0. A larger ratio can help reduce some aberrations in the optical system, such as astigmatism and distortion, thereby improving the imaging quality. At the same time, this design may also bring better focusing stability and fault tolerance of the optical system.

[0067] Please refer to Figure 4 and Figure 5 , Figure 4 It is a schematic diagram of the MTF (Modulation Transfer Function) of the far-infrared optical lens provided by the utility model. Figure 5 It is a point spread diagram of the far-infrared optical lens provided by the utility model. Figure 4 and Figure 5 The imaging quality of the far-infrared optical lens provided by the utility model under different field angles is shown, and it can be seen that the far-infrared optical lens provided by the utility model has good imaging quality.

[0068] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present utility model rather than to limit it. For those skilled in the art, the technical solutions described in the above embodiments can be modified, or some of the technical features therein can be replaced by equivalents; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present utility model.

Claims

1. A far-infrared optical lens, characterized in that: include: A first lens, a second lens, a stop and a third lens are sequentially arranged along the incident direction of light; Wherein, the first lens is a positive meniscus lens, the second lens is a negative meniscus lens, and the third lens is a positive meniscus lens; the first lens, the second lens and the third lens are all aspherical lenses; The materials of the first lens, the second lens and the third lens are far-infrared glass; The far-infrared optical lens can form images in the 7um to 14um band.

2. The far-infrared optical lens according to claim 1, characterized in that: The object side surface of the first lens is convex, and the image side surface is concave; the object side surface of the second lens is concave, and the image side surface is convex; the object side surface of the third lens is convex, and the image side surface is concave.

3. The far-infrared optical lens according to claim 2, characterized in that: The first lens meets the following conditions: R1=5.63mm, R2=6.85mm, Nd=4.0, D=0.90mm; Conic1=-0.05; Conic2=0.136; The second lens meets the following conditions: R1=-10.48mm, R2=-17.52mm, Nd=3.3, D=1.6mm; Conic1=2.225, Conic2=0.8; The third lens meets the following conditions: R1=8.1mm, R2=19.01mm, Nd=4.0, D=1.03mm; Conic1=5.85, Conic2=95.81; Among them, R1 represents the curvature radius of the object side, R2 represents the curvature radius of the image side, Nd represents the refractive index, D represents the center thickness, and Conic1 and Conic2 represent the parameters of the aspherical surface.

4. The far-infrared optical lens according to claim 3, characterized in that: The center distance between the first lens and the second lens is 0.89 mm; The center distance between the second lens and the aperture is 1.32 mm; The center distance between the aperture and the third lens is 0.08 mm.

5. The far-infrared optical lens according to claim 1, characterized in that: The lens focal lengths of the first lens, the second lens and the third lens and the system focal length of the far-infrared optical lens meet the following conditions: 1.4 <f1 / f<1.6,-2.5<f2 / f<-3.2,0.5<f3 / f<1.5; Among them, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f is the system focal length.

6. The far-infrared optical lens according to claim 5, characterized in that: The ratio of the system image height of the far-infrared optical lens to the system focal length is greater than or equal to 0.

885.

7. The far-infrared optical lens according to any one of claims 1 to 4, characterized in that: The refractive indexes of the first lens, the second lens and the third lens are all greater than or equal to 2.

0.

8. The far-infrared optical lens according to any one of claims 1 to 4, characterized in that: The F number of the far-infrared optical lens is less than or equal to 1.

2.

9. An image acquisition device, characterized in that: It comprises a far-infrared thermal imaging sensor and a far-infrared optical lens as described in any one of claims 1 to 8, wherein the far-infrared thermal imaging sensor is located at the light-emitting side of the far-infrared optical lens.

10. The image acquisition device according to claim 9, characterized in that: The ratio of the distance from the front surface of the first lens to the imaging surface of the far-infrared imaging sensor to the system focal length of the far-infrared optical lens is greater than or equal to 1.5 and less than or equal to 2.0.

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