Lenses and imaging devices for gas detection

Abstract

This application discloses a lens for gas detection, comprising a front fixed group, a movable group, and a rear fixed group arranged sequentially along the optical axis transmission direction. The front fixed group includes a first lens and a second lens arranged sequentially along the optical axis transmission direction. The first lens is a meniscus positive lens with its convex surface facing the object side, and the second lens is a meniscus negative lens with its convex surface facing the object side. The movable group includes a third lens and a fourth lens arranged sequentially along the optical axis transmission direction. The third lens is a biconcave lens, and the fourth lens is a biconvex lens. Both the third and fourth lenses are capable of reciprocating along the optical axis. The rear fixed group includes a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis transmission direction. The fifth lens is a meniscus positive lens with its convex surface facing the object side, the sixth lens is a meniscus positive lens with its convex surface facing the image side, and the seventh lens is a meniscus positive lens with its convex surface facing the object side. This lens can detect industrial gases such as methane. This application also discloses an imaging device.

Description

Technical Field

[0001] This application belongs to the field of infrared optical technology, and specifically relates to a lens and imaging device for gas detection. Background Technology

[0002] Infrared detectors are increasingly widely used in the detection field. Due to their non-contact and visual characteristics, they are also being applied to industrial gas detection. Most industrial gases, such as hydrocarbon organic compounds, possess unique infrared absorption spectra. Utilizing this characteristic, industrial gases that are invisible to the naked eye within specific wavelengths of their infrared absorption spectrum can be imaged using an infrared lens in a specific infrared band; this is called optical gas imaging. Based on this imaging method, leak sources can be located, and the direction of gas diffusion can be clearly displayed, making this imaging method an important technical means for gas leak detection and source tracing. Infrared detectors are used in optical gas imaging to reduce emissions, improve production efficiency, and ensure a safe working environment.

[0003] With the increasing demand for infrared detectors used to detect gases, the development of matching lenses is urgently needed. Summary of the Invention

[0004] To address the above problems, this invention proposes a lens for gas detection. The specific technical solution is as follows.

[0005] The technical solution proposed in this application is as follows: A lens for gas detection includes a front fixed group, a movable group, and a rear fixed group arranged sequentially along the optical axis transmission direction; The front fixing group includes a first lens and a second lens arranged sequentially along the optical axis transmission direction. The first lens is a positive meniscus lens with its convex surface facing the object side, and the second lens is a negative meniscus lens with its convex surface facing the object side. The movable group includes a third lens and a fourth lens arranged sequentially along the optical axis transmission direction. The third lens is a biconcave lens and the fourth lens is a biconvex lens. Both the third lens and the fourth lens are capable of reciprocating along the optical axis. The rear fixing group includes a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis transmission direction. The fifth lens is a meniscus lens with its convex surface facing the object side, the sixth lens is a meniscus lens with its convex surface facing the image side, and the seventh lens is a meniscus lens with its convex surface facing the object side.

[0006] Furthermore, when the focal length of the lens is 30mm, the air gap between the second lens and the third lens is 20.756mm, the air gap between the third lens and the fourth lens is 41.099mm, and the air gap between the fourth lens and the fifth lens is 2.164mm. When the focal length of the lens is 60mm, the air gap between the second lens and the third lens is 34.846mm, the air gap between the third lens and the fourth lens is 20.611mm, and the air gap between the fourth lens and the fifth lens is 8.563mm. When the focal length of the lens is 90mm, the air gap between the second lens and the third lens is 41.876mm, the air gap between the third lens and the fourth lens is 9.996mm, and the air gap between the fourth lens and the fifth lens is 12.147mm.

[0007] Furthermore, the center thickness of the first lens is 11.4 mm, the object side radius of curvature is 87.62 mm, and the image side radius of curvature is 700 mm; The second lens has a center thickness of 4.5 mm, an object-side radius of curvature of 114.96 mm, and an image-side radius of curvature of 62.49 mm. The third lens has a center thickness of 3.5 mm, an object-side radius of curvature of -142.33 mm, and an image-side radius of curvature of 157.88 mm. The fourth lens has a center thickness of 10mm, an object-side radius of curvature of 85.95mm, and an image-side radius of curvature of -76.88mm. The fifth lens has a center thickness of 5.76 mm, an object-side radius of curvature of 19.89 mm, and an image-side radius of curvature of 15.93 mm. The sixth lens has a center thickness of 5.51 mm, an object-side radius of curvature of -11.56 mm, and an image-side radius of curvature of -13.6 mm. The seventh lens has a center thickness of 5.2 mm, an object-side radius of curvature of 53.1 mm, and an image-side radius of curvature of -1414 mm.

[0008] Furthermore, the air gap between the first lens and the second lens is 3 mm; the air gap between the fifth lens and the sixth lens is 29.22 mm; and the air gap between the sixth lens and the seventh lens is 23.19 mm.

[0009] Furthermore, the first lens is made of silicon single crystal, the second lens, the third lens, the fifth lens, the sixth lens and the seventh lens are all made of germanium single crystal, and the fourth lens is made of zinc selenide.

[0010] Furthermore, the image-side surfaces of the first lens, the second lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens, as well as the object-side surface of the third lens, are all aspherical surfaces and satisfy the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

[0011] Furthermore, the lens operates in the wavelength range of 3.2μm to 3.4μm, has an operating temperature range of -40℃ to 60℃, and an F-number of 1.2.

[0012] An imaging apparatus includes a lens for gas detection as described above and a detector for receiving the image formed by the lens.

[0013] Furthermore, the detector includes a protective window, an aperture, and a detector focal plane array arranged sequentially.

[0014] Furthermore, the detector is a cooled mid-wave infrared detector with 640×512 pixels and a pixel size of 15μm.

[0015] Using the aforementioned lens and imaging device, industrial gases such as methane can be detected, which has wide application value in industrial settings. Attached Figure Description

[0016] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof.

[0017] Figure 1 A schematic diagram of the imaging device provided in an embodiment of this application when the focal length is 30mm; Figure 2 for Figure 1 The diagram shows the structure of the imaging device at a focal length of 60mm. Figure 3 for Figure 1 The diagram shows the structure of the imaging device at a focal length of 90mm. Figure 4 This is a dot plot of the imaging device at a focal length of 30mm. Figure 5 The MTF diagram of the imaging device at a focal length of 30mm; Figure 6 This is a dot plot of the imaging device at a focal length of 60mm. Figure 7 The MTF diagram of the imaging device at a focal length of 60mm; Figure 8 This is a dot plot of the imaging device at a focal length of 90mm. Figure 9 This is the MTF diagram of the imaging device at a focal length of 90mm.

[0018] Label Explanation: 11. First lens; 12. Second lens; 13. Third lens; 14. Fourth lens; 15. Fifth lens; 16. Sixth lens; 17. Seventh lens; 21. Protective window; 22. Aperture stop; 23. Detector focal plane array. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the equipment 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 application.

[0021] This application provides an imaging device, which includes a lens for gas detection and a detector for receiving the image captured by the lens. The detector is a cooled mid-wave infrared detector with 640×512 pixels and a pixel size of 15μm. The lens has a focal length of 30mm to 90mm, a zoom ratio of three times, an operating wavelength of 3.2μm to 3.4μm, an operating temperature of -40℃ to 60℃, and an F-number of 1.2.

[0022] like Figure 1As shown, the lens includes a front fixed group, a movable group and a rear fixed group arranged sequentially along the optical axis transmission direction, and a protective window, an aperture and a detector focal plane array are arranged sequentially behind the lens.

[0023] The front fixed group includes a first lens and a second lens arranged sequentially along the optical axis transmission direction. The first lens is a meniscus positive lens with its convex surface facing the object side, and the second lens is a meniscus negative lens with its convex surface facing the object side. The first and second lenses are used to converge light rays. The movable group includes a third lens and a fourth lens arranged sequentially along the optical axis transmission direction. The third lens is a biconcave lens, and the fourth lens is a biconvex lens. Both the third and fourth lenses can reciprocate along the optical axis to change the focal length of the lens and adjust the zoom ratio. The rear fixed group includes a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis transmission direction. The fifth lens is a meniscus positive lens with its convex surface facing the object side, used to compensate for image shift during zooming. The sixth lens is a meniscus positive lens with its convex surface facing the image side, and the seventh lens is a meniscus positive lens with its convex surface facing the object side. The sixth and seventh lenses are used to match the aperture stop and perform secondary imaging.

[0024] It is understandable that, along the optical axis from left to right, the left side is the object side and the right side is the image side. For example, the S1 surface of the first lens is the object side surface and the S2 surface is the image side surface. Other lenses will not be discussed here.

[0025] Using the aforementioned lens and imaging device, industrial gases such as methane can be detected, which has wide application value in industrial settings.

[0026] As shown in Table 1, the center thickness T1 of the first lens is 11.4 mm, the object-side radius of curvature is 87.62 mm, and the image-side radius of curvature is 700 mm; the center thickness T2 of the second lens is 4.5 mm, the object-side radius of curvature is 114.96 mm, and the image-side radius of curvature is 62.49 mm; the center thickness T3 of the third lens is 3.5 mm, the object-side radius of curvature is -142.33 mm, and the image-side radius of curvature is 157.88 mm; the center thickness T4 of the fourth lens is 10 mm, the object-side radius of curvature is... The radius of curvature of the first lens is 85.95 mm, and the radius of curvature of the image side is -76.88 mm; the center thickness T5 of the fifth lens is 5.76 mm, the radius of curvature of the object side is 19.89 mm, and the radius of curvature of the image side is 15.93 mm; the center thickness T6 of the sixth lens is 5.51 mm, the radius of curvature of the object side is -11.56 mm, and the radius of curvature of the image side is -13.6 mm; the center thickness T7 of the seventh lens is 5.2 mm, the radius of curvature of the object side is 53.1 mm, and the radius of curvature of the image side is -1414 mm.

[0027] Furthermore, the air gap D1 between the first and second lenses is 3 mm; the air gap adjustment range D2 between the second and third lenses is 20.756 mm to 41.876 mm; the air gap adjustment range D3 between the third and fourth lenses is 9.996 mm to 41.099 mm; the air gap adjustment range D4 between the fourth and fifth lenses is 2.164 mm to 12.147 mm; the air gap D5 between the fifth and sixth lenses is 29.22 mm; and the air gap D6 between the sixth and seventh lenses is 23.19 mm.

[0028] It should be noted that, Figure 1 , Figure 2 and Figure 3 These are lens composition diagrams for lens focal lengths of 30mm, 60mm, and 90mm. The arrangement of each lens element remains unchanged, and the parameters of each element are identical. Figure 1 The center thickness T and air gap D are marked. The air gap D represents the air gap between the two corresponding lenses, but there is no limit to the specific data of the air gap D.

[0029] Specifically, when the lens focal length is 30mm, the air gap between the second and third lenses (D2) is 20.756mm, the air gap between the third and fourth lenses (D3) is 41.099mm, and the air gap between the fourth and fifth lenses (D4) is 2.164mm; when the lens focal length is 60mm, the air gap between the second and third lenses (D2) is 34.846mm, the air gap between the third and fourth lenses (D3) is 20.611mm, and the air gap between the fourth and fifth lenses (D4) is 8.563mm; when the lens focal length is 90mm, the air gap between the second and third lenses (D2) is 41.876mm, the air gap between the third and fourth lenses (D3) is 9.996mm, and the air gap between the fourth and fifth lenses (D4) is 12.147mm.

[0030] The first lens is made of silicon single crystal; the second, third, fifth, sixth and seventh lenses are made of germanium single crystal; and the fourth lens is made of zinc selenide.

[0031] Table 1 Parameters of each lens As shown in Table 2, the image-side surfaces of the first, second, fourth, fifth, sixth, and seventh lenses, as well as the object-side surface of the third lens, are all aspherical and satisfy the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

[0032] Table 2 Aspherical data of lenses Figures 4 to 9 The images shown are dot plots and MTF plots of the lenses in the above embodiments at focal lengths of 30 / 60 / 90mm, respectively. In the MTF plots, the horizontal axis represents different spatial frequencies, and the vertical axis represents modulation density, with a cutoff resolution of 331p / mm for each MTF plot. It can be seen that the MTF is close to the diffraction limit, indicating good image quality.

[0033] The lens and imaging device for gas detection provided in this application operate in the wavelength range of 3.2μm to 3.4μm, with a focal length of 30mm to 90mm, a zoom ratio of up to three times, an operating temperature range of -40℃ to 60℃, an F-number of 1.2, a pixel count of 640×512, and a pixel size of 15μm. This lens and imaging device can detect industrial gases such as methane and has wide application value in industrial settings.

[0034] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A lens for gas detection, characterized in that, It consists of a front fixed group, a movable group, and a rear fixed group arranged sequentially along the optical axis transmission direction; The front fixing group consists of a first lens and a second lens arranged sequentially along the optical axis transmission direction. The first lens is a positive meniscus lens with its convex surface facing the object side, and the second lens is a negative meniscus lens with its convex surface facing the object side. The movable group consists of a third lens and a fourth lens arranged sequentially along the optical axis transmission direction. The third lens is a biconcave lens and the fourth lens is a biconvex lens. Both the third lens and the fourth lens are capable of reciprocating along the optical axis. The rear fixing group consists of a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis transmission direction. The fifth lens is a meniscus lens with its convex surface facing the object side, the sixth lens is a meniscus lens with its convex surface facing the image side, and the seventh lens is a meniscus lens with its convex surface facing the object side. The first lens has a center thickness of 11.4 mm, an object-side radius of curvature of 87.62 mm, and an image-side radius of curvature of 700 mm. The second lens has a center thickness of 4.5 mm, an object-side radius of curvature of 114.96 mm, and an image-side radius of curvature of 62.49 mm. The third lens has a center thickness of 3.5 mm, an object-side radius of curvature of -142.33 mm, and an image-side radius of curvature of 157.88 mm. The fourth lens has a center thickness of 10mm, an object-side radius of curvature of 85.95mm, and an image-side radius of curvature of -76.88mm. The fifth lens has a center thickness of 5.76 mm, an object-side radius of curvature of 19.89 mm, and an image-side radius of curvature of 15.93 mm. The sixth lens has a center thickness of 5.51 mm, an object-side radius of curvature of -11.56 mm, and an image-side radius of curvature of -13.6 mm. The seventh lens has a center thickness of 5.2 mm, an object-side radius of curvature of 53.1 mm, and an image-side radius of curvature of -1414 mm.

2. The lens for gas detection according to claim 1, characterized in that, When the focal length of the lens is 30mm, the air gap between the second lens and the third lens is 20.756mm, the air gap between the third lens and the fourth lens is 41.099mm, and the air gap between the fourth lens and the fifth lens is 2.164mm. When the focal length of the lens is 60mm, the air gap between the second lens and the third lens is 34.846mm, the air gap between the third lens and the fourth lens is 20.611mm, and the air gap between the fourth lens and the fifth lens is 8.563mm. When the focal length of the lens is 90mm, the air gap between the second lens and the third lens is 41.876mm, the air gap between the third lens and the fourth lens is 9.996mm, and the air gap between the fourth lens and the fifth lens is 12.147mm.

3. The lens for gas detection according to claim 1, characterized in that, The air gap between the first lens and the second lens is 3 mm; the air gap between the fifth lens and the sixth lens is 29.22 mm; and the air gap between the sixth lens and the seventh lens is 23.19 mm.

4. The lens for gas detection according to claim 1, characterized in that, The first lens is made of silicon single crystal, the second lens, the third lens, the fifth lens, the sixth lens and the seventh lens are all made of germanium single crystal, and the fourth lens is made of zinc selenide.

5. The lens for gas detection according to claim 1, characterized in that, The image-side surfaces of the first lens, the second lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens, as well as the object-side surface of the third lens, are all aspherical and satisfy the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

6. The lens for gas detection according to claim 1, characterized in that, The lens operates in the wavelength range of 3.2μm to 3.4μm, has an operating temperature range of -40℃ to 60℃, and an F-number of 1.

2.

7. An imaging device, characterized in that, It includes the lens for gas detection as described in any one of claims 1 to 6, and the detector for receiving the image formed by the lens.

8. The imaging apparatus according to claim 7, characterized in that, The detector includes a protective window, an aperture, and a detector focal plane array arranged sequentially.

9. The imaging apparatus according to claim 7, characterized in that, The detector is a cooled mid-wave infrared detector with 640×512 pixels and a pixel size of 15μm.

Images