Athermalized infrared lens and imaging device

Abstract

The application discloses athermal infrared lens with a focal length of 3.2 mm, which comprises a first lens and a second lens arranged in sequence along the transmission direction of the optical axis, the first lens is a convex moon positive lens with a convex surface facing the object side, the second lens is a double convex lens, and a diaphragm is arranged between the first lens and the second lens; wherein the material of the first lens and the second lens is chalcogenide glass. In this way, by reasonably distributing the optical power, adjusting the combination and arrangement mode of the lens, utilizing the difference in thermal characteristics between different materials, the positive and negative optical powers are matched with each other to compensate the influence caused by temperature change, so that athermalization is realized under the condition of ensuring small volume. Moreover, the infrared lens only adopts two lenses, has a simple structure, a short focal length, and an angle FOV of 68°. The application further discloses an imaging device.

Description

Technical Field

[0001] This application belongs to the field of infrared lens technology, specifically relating to a thermally differential infrared lens and imaging device. Background Technology

[0002] Infrared lenses typically require operating temperatures ranging from -40℃ to 60℃. However, due to the large coefficients of thermal expansion and refractive index of infrared lens materials, changes in ambient temperature significantly alter the refractive index, surface curvature, thickness, and spacing between adjacent lenses. This can lead to severe defocusing in infrared lenses. Active thermal ablation methods, on the other hand, increase the size of the infrared lens. Therefore, there is an urgent need for an infrared lens that achieves calorimetry through passive thermal ablation while maintaining a smaller size. Summary of the Invention

[0003] Based on this, this application provides a thermally neutralized infrared lens and imaging device that achieves calorimetry through passive thermal differential elimination and has a small size.

[0004] The technical solution proposed in this application is as follows: A thermally ablated infrared lens with a focal length of 3.2mm, the infrared lens includes a first lens and a second lens arranged sequentially along the optical axis transmission direction, the first lens is a meniscus lens with its convex surface facing the object side, the second lens is a biconvex lens, and an aperture stop is provided between the first lens and the second lens; Both the first lens and the second lens are made of chalcogenide glass.

[0005] In this way, by rationally allocating optical power and adjusting the combination and arrangement of lenses, and utilizing the differences in thermal properties between different materials, the positive and negative optical power can complement each other to compensate for the effects of temperature changes, thereby achieving heatless operation while ensuring a small size. Moreover, this infrared lens uses only two lenses, has a simple structure, a short focal length, and a diagonal FOV of 68°.

[0006] Furthermore, the air gap between the first lens and the aperture stop is 0.5 mm, and the air gap between the aperture stop and the second lens is 0.189 mm.

[0007] Furthermore, the first lens has a center thickness of 1.13 mm, an object-side radius of curvature of 2.81 mm, and an image-side radius of curvature of 2.35 mm; the second lens has a center thickness of 1.41 mm, an object-side radius of curvature of 6.99 mm, and an image-side radius of curvature of -8.72 mm.

[0008] Furthermore, the focal length of the first lens is 20.364 mm; the focal length of the second lens is 2.744 mm.

[0009] Furthermore, the infrared lens has a relative aperture of 1.1, a field of view of 54.6°×41.7°, and an operating wavelength of 10-12μm.

[0010] Furthermore, all surfaces of the first lens and the second lens are 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.

[0011] An imaging device includes a thermally ablated infrared lens as described above and a detector for receiving images from the infrared lens, wherein the detector is a cooled detector.

[0012] Furthermore, the detector includes a protective window and an image plane arranged sequentially, the air gap between the fifth lens and the protective window is 1.6 mm, and the protective window is attached to the image plane.

[0013] Furthermore, the distance between the object-side surface of the first lens and the image surface on the optical axis is 5.55 mm, and the distance between the image-side surface of the second lens and the image surface on the optical axis is 2.325 mm.

[0014] Furthermore, the detector has 256×192 pixels and a pixel size of 12μm. Attached Figure Description

[0015] 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.

[0016] Figure 1 This is a schematic diagram of the optical path structure of an imaging device provided in an embodiment of this application; Figure 2 MTF image of the thermally ablated differential infrared lens provided in this application at 25°C; Figure 3 A dot plot of the thermally ablated infrared lens provided in this application at 25°C; Figure 4 MTF image of the thermally ablated differential infrared lens provided in this application at 60°C; Figure 5 A dot plot of the thermally ablated infrared lens provided in this application at 60°C; Figure 6 MTF plot of the thermally ablated differential infrared lens provided in this application at -40°C; Figure 7 A dot plot of the thermally ablated infrared lens provided in this application at -40°C.

[0017] Label Explanation: 11. First lens; 12. Second lens; 13. Aperture stop; 21. Protective window; 22. Image plane. Detailed Implementation

[0018] 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.

[0019] This application discloses an imaging device, including a pyrometric infrared lens and a detector that receives the image from the infrared lens. The detector is a cooled detector. The infrared lens has a focal length of 3.2 mm, a relative aperture of 1.1, a field of view of 54.6° × 41.7°, and an operating wavelength of 10-12 μm. The detector has 256 × 192 pixels and a pixel size of 12 μm.

[0020] like Figure 1 As shown, in one embodiment, the infrared lens includes a first lens and a second lens arranged sequentially along the optical axis transmission direction, with an aperture stop between the first and second lenses. The first lens is a meniscus lens with its convex surface facing the object side, and the second lens is a biconvex lens. Both the first and second lenses are made of chalcogenide glass. Thus, by rationally allocating optical power and adjusting the combination and arrangement of the lenses, and utilizing the differences in thermal properties between different materials, the positive and negative optical powers are coordinated to compensate for the effects of temperature changes, thereby achieving heatless operation while maintaining a small size. Furthermore, this infrared lens uses only two lenses, has a simple structure, a short focal length, and a diagonal FOV of 68°. Specifically, the focal length of the first lens is 20.364 mm, and the focal length of the second lens is 2.744 mm.

[0021] In one embodiment, the detector includes a protective window and an image plane arranged sequentially, with the image plane fitting against the protective window to further reduce the size of the imaging device and facilitate miniaturization design. Specifically, in this embodiment, the distance between the object-side surface of the first lens and the image plane on the optical axis is 5.55 mm, meaning the total length of the optical system of the imaging device is 5.55 mm, while the distance between the image-side surface of the fifth lens and the image plane on the optical axis is 2.325 mm, meaning the back cutoff of the optical system is 2.325 mm.

[0022] As shown in Table 1, the air gap between the first lens and the aperture stop is 0.5 mm, the air gap between the aperture stop and the second lens is 0.189 mm, and the air gap between the second lens and the protective window is 1.6 mm.

[0023] Furthermore, the center thickness of the first lens is 1.13 mm, the radius of curvature of the object side is 2.81 mm, and the radius of curvature of the image side is 2.35 mm; the center thickness of the second lens is 1.41 mm, the radius of curvature of the object side is 6.99 mm, and the radius of curvature of the image side is -8.72 mm.

[0024] It is understandable that, such as Figure 1 As shown, the optical axis propagation direction is from left to right. The left and right sides of the lens are the object-side and image-side, respectively. Taking the first lens as an example, the S1 surface on the left side of the first lens is the object-side surface, and the S2 surface on the right side is the image-side surface. Other lenses will not be described in detail here.

[0025] Table 1 Lens Parameters In one embodiment, all surfaces of the first lens and the second lens are 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. The data for each of the above aspherical surfaces are shown in Table 2.

[0026] Table 2 Aspherical Data Please see Figures 2 to 7 , Figure 2 The image shows the MTF (cutoff resolution of 20 lp / mm) of the infrared lens in the above embodiment at a temperature of 25°C. Figure 3 This is a dot plot of the infrared lens in the above embodiment at a temperature of 25°C. Figure 4 The image shows the MTF (cutoff resolution of 20 lp / mm) of the infrared lens in the above embodiment at a temperature of 60°C. Figure 5 This is a dot plot of the infrared lens in the above embodiment at a temperature of 60°C. Figure 6 The image shows the MTF (cutoff resolution of 20 lp / mm) of the infrared lens in the above embodiment at a temperature of -40°C. Figure 7 This is a dot plot of the infrared lens in the above embodiment at a temperature of -40°C. The plot shows that the infrared lens has good image quality and a wide operating temperature range.

[0027] In summary, the pyrometric infrared lens provided in this application has a focal length of 3.2 mm, a relative aperture of 1.1, a field of view of 54.6°×41.7°, and an operating wavelength of 10-12 μm. It can be used with cooled detectors with a pixel count of 256×192 and a pixel size of 12 μm. This infrared lens has a relatively simple structure and produces clear images. Furthermore, it employs passive pyrometric correction to achieve a thermal effect, resulting in a small size.

[0028] 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 thermally ablated infrared lens, characterized in that the focal length is 3.2mm, the infrared lens is composed of a first lens and a second lens arranged sequentially along the optical axis transmission direction, the first lens is a meniscus lens with its convex surface facing the object side, the second lens is a biconvex lens, and an aperture is provided between the first lens and the second lens; Both the first and second lenses are made of chalcogenide glass. The first lens has a center thickness of 1.13 mm, an object-side radius of curvature of 2.81 mm, and an image-side radius of curvature of 2.35 mm. The second lens has a center thickness of... The object side has a curvature radius of 1.41 mm, the object side has a curvature radius of 6.99 mm, and the image side has a curvature radius of -8.72 mm.

2. The thermally ablated infrared lens according to claim 1, characterized in that, The air gap between the first lens and the aperture stop is 0.5 mm, and the air gap between the aperture stop and the second lens is 0.189 mm.

3. The thermally ablated infrared lens according to claim 1, characterized in that, The focal length of the first lens is 20.364 mm; the focal length of the second lens is 2.744 mm.

4. The thermally ablated infrared lens according to claim 1, characterized in that, The infrared lens has a relative aperture of 1.1, a field of view of 54.6°×41.7°, and a working wavelength of 10-12μm.

5. The thermally ablated infrared lens according to claim 1, characterized in that, All surfaces of the first lens and the second lens are 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. An imaging device, characterized in that, It includes the thermally ablation infrared lens as described in any one of claims 1-5 and a detector for receiving the image formed by the infrared lens, wherein the detector is a cooled detector.

7. The imaging apparatus according to claim 6, characterized in that, The detector includes a protective window and an image plane arranged sequentially. The air gap between the second lens and the protective window is 1.6 mm, and the protective window is attached to the image plane.

8. The imaging apparatus according to claim 7, characterized in that, The distance between the object-side surface of the first lens and the image surface on the optical axis is 5.55 mm, and the distance between the image-side surface of the second lens and the image surface on the optical axis is 2.325 mm.

9. The imaging apparatus according to claim 6, characterized in that, The detector has 256×192 pixels and a pixel size of 12μm.

Images