Infrared microscope objective and imaging device

Abstract

The application discloses an imaging device, which comprises an infrared microscope lens and a detector capable of receiving the image formed by the infrared microscope lens. The magnification β of the infrared microscope lens satisfies 0.11≤β≤0.15, the object-side linear field of view 2y satisfies 75mm≤2y≤80mm, and the infrared microscope lens is composed of a first lens, a second lens and a third lens arranged in sequence along the optical axis. The infrared microscope lens only uses three lenses to efficiently reduce the large-size primary image formed by a front optical system to a small target infrared detector, has a simple and compact structure and low manufacturing cost. Meanwhile, the infrared microscope lens has good aberration correction, high imaging clarity consistency, stable imaging quality in a working temperature range and excellent thermal-aberration-correcting capability.

Description

Technical Field

[0001] This application belongs to the field of optical lens technology, specifically relating to an infrared microscope lens and imaging device. Background Technology

[0002] In optical imaging systems, relay imaging lenses are often used to re-image the real image formed by the preceding optical module (such as a microscope objective, telescope objective, or pre-imaging group) to the subsequent detector or visual system at a certain magnification, thereby achieving image plane position conversion, size scaling, and pupil matching.

[0003] In applications such as infrared microscopy, semiconductor detection, and low-light signal acquisition, the following technical contradictions are often encountered: On the one hand, to obtain high resolution or large numerical aperture (NA), the imaging field of view of the pre-stage objective lens is usually designed to be large, with the size of the primary image plane reaching several millimeters or even tens of millimeters; on the other hand, the photosensitive target size of the post-stage infrared detector (such as cooled InSb or MCT focal plane array) is often very small, with a typical diagonal size of only 1 mm to 2 mm. If the large primary real image formed by the pre-stage is directly projected onto the small target detector, it will result in the loss of most light energy, a severe reduction in the effective field of view, and an inability to achieve synchronous imaging of the entire sample area.

[0004] To address this issue, the traditional approach is to replace the front-stage objective lens with one of different magnifications or sacrifice resolution to adjust the field of view. However, this increases system complexity and cost, and it's difficult to simultaneously meet the requirements of a large field of view, high resolution, and detector-target surface matching. Another method is to add a fixed-magnification imaging lens group between the primary image plane and the detector, i.e., a relay lens. However, commercially available relay lenses typically have a magnification of 1× or higher. When used for magnifications below 1×, they often suffer from problems such as difficulty in aberration correction, insufficient telecentricity, and a short back working distance that prevents the installation of detector windows or cooling structures.

[0005] Furthermore, the infrared band (especially the mid-wave infrared 3~5μm or long-wave infrared 8~12μm) has a high diffraction limit, which limits the choice of lens materials (such as silicon, germanium, chalcogenide glass, etc.) and the dispersion characteristics vary greatly, making it more difficult to achieve relay imaging in a wide range while simultaneously controlling spherical aberration, coma, field curvature and distortion.

[0006] Therefore, there is an urgent need for a specially designed relay lens with a magnification of less than 1×, which can efficiently reduce the large-size single real image formed by the front-end optical system and image it onto a small target infrared detector, while maintaining good aberration correction, so as to improve the system's light energy utilization and imaging consistency. Summary of the Invention

[0007] Therefore, it is necessary to provide an infrared microscope head and imaging device with a magnification of less than 1×, which can efficiently reduce the large-size single real image formed by the pre-stage optical system to a small target infrared detector, while maintaining good aberration correction.

[0008] The technical solution proposed in this application is as follows: An infrared microscope head has a magnification β satisfying: 0.11≤β≤0.15, an object-side field of view 2y satisfying: 75mm≤2y≤80mm, and a working wavelength range of 8~12μm. The infrared microscope head is composed of a first lens, a second lens, and a third lens arranged sequentially along the optical axis. The first lens is a meniscus positive lens with its convex surface facing the object side, the second lens is a meniscus negative lens with its convex surface facing the object side, and the third lens is a biconvex positive lens. The air gap between the first lens and the second lens is 4.54 mm, and the air gap between the second lens and the third lens is 7.81 mm.

[0009] Furthermore, the first lens has a center thickness of 6 mm, an object-side radius of curvature of 19.39 mm, and an image-side radius of curvature of 45.335 mm; the second lens has a center thickness of 2 mm, an object-side radius of curvature of 31.161 mm, and an image-side radius of curvature of 10.069 mm; and the third lens has a center thickness of 4.7 mm, an object-side radius of curvature of 37 mm, and an image-side radius of curvature of -79.565 mm.

[0010] Furthermore, the numerical aperture NA of the infrared microscope head satisfies: 0.05≤NA≤0.08, the object-side working distance WD satisfies: 199mm≤WD≤201mm, the horizontal field of view HFOV satisfies: 16°≤HFOV≤18°, and the vertical field of view satisfies: 13°≤VFOV≤14°.

[0011] Furthermore, all lenses are made of chalcogenide glass.

[0012] Furthermore, the image-side surface of the first lens, the object-side surface of the second lens, and the image-side surface of the third lens are all aspherical surfaces, and satisfy the aspherical surface 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.

[0013] An imaging device includes the aforementioned infrared microscope head and a detector capable of receiving images from the infrared microscope head.

[0014] Furthermore, the detector has a resolution of 640×512 and a pixel size of 12μm.

[0015] Furthermore, the total optical length of the imaging device is 35.11 mm, and the back intercept is 10.06.

[0016] In summary, this application discloses an imaging device, including an infrared microscope head and a detector capable of receiving images from the infrared microscope head. The infrared microscope head has an F-number of 1.0, an operating wavelength of 8~12μm, and an operating temperature of -40℃~+80℃. The magnification β of the infrared microscope head satisfies: 0.11≤β≤0.15, the object-side field of view 2y satisfies: 75mm≤2y≤80mm, the numerical aperture NA satisfies: 0.05≤NA≤0.08, the object-side working distance WD satisfies: 199mm≤WD≤201mm, the horizontal field of view HFOV satisfies: 16°≤HFOV≤18°, and the vertical field of view satisfies: 13°≤VFOV≤14°. The detector is an uncooled infrared detector with a resolution of 640×512 and a pixel size of 12μm. This infrared microscope lens utilizes only three lenses to efficiently reduce the large-size real image formed by the pre-amplifier optical system and project it onto a small-target infrared detector. Its structure is simple and compact, resulting in low manufacturing costs. Furthermore, this infrared microscope lens exhibits excellent aberration correction, high consistency in image sharpness, and stable image quality within its operating temperature range, demonstrating superior thermal distortion mitigation capabilities. Attached Figure Description

[0017] 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.

[0018] Figure 1 This is a schematic diagram of the optical path structure of an infrared microscope head provided in one embodiment of this application; Figure 2 MTF image of an infrared microscope lens at 20°C provided in one embodiment of this application; Figure 3 MTF image of an infrared microscope lens at -40°C provided in one embodiment of this application; Figure 4 MTF image of an infrared microscope head at 80°C provided in one embodiment of this application; Figure 5 A dot plot of an infrared microscope head at 20°C provided in an embodiment of this application; Figure 6 A dot plot of an infrared microscope lens at -40°C provided in one embodiment of this application; Figure 7A dot plot of an infrared microscope head at 80°C provided in an embodiment of this application; Figure 8 A field distortion image of an infrared microscope head provided in one embodiment of this application; Figure 9 A diffraction-enclosed energy map of an infrared microscope head provided in an embodiment of this application; Figure 10 A relative illumination diagram of an infrared microscope lens provided in one embodiment of this application; Figure 11 A vignetting image of an infrared microscope lens provided in one embodiment of this application.

[0019] Label Explanation: 11. First lens; 12. Second lens; 13. Third lens; 14. Protective window; 15. Image plane. Detailed Implementation

[0020] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0022] This application discloses an imaging device, including an infrared microscope head and a detector capable of receiving images from the infrared microscope head. The infrared microscope head has an F-number of 1.0, an operating wavelength of 8~12μm, and an operating temperature of -40℃~+80℃. The magnification β of the infrared microscope head satisfies: 0.11≤β≤0.15, the object-side field of view 2y satisfies: 75mm≤2y≤80mm, the numerical aperture NA satisfies: 0.05≤NA≤0.08, the object-side working distance WD satisfies: 199mm≤WD≤201mm, the horizontal field of view HFOV satisfies: 16°≤HFOV≤18°, and the vertical field of view VFOV satisfies: 13°≤VFOV≤14°. The detector is an uncooled infrared detector with a resolution of 640×512 and a pixel size of 12μm.

[0023] like Figure 1As shown, in one embodiment, the infrared microscope head comprises a first lens 11, a second lens 12, and a third lens 13 arranged sequentially along the optical axis. The first lens 11 is a meniscus positive lens with its convex surface facing the object side, the second lens 12 is a meniscus negative lens with its convex surface facing the object side, and the third lens 13 is a biconvex positive lens. Further, the detector includes a protective window 14 and an image plane 15 arranged sequentially along the optical axis.

[0024] In one specific embodiment, the magnification of the infrared microscope lens is β=0.129, the object-side field of view is 2y=77.6mm, the numerical aperture is NA=0.064, and the field of view is 16.9°×13.6°.

[0025] Furthermore, please also refer to Table 1. The air gap between the first lens 11 and the second lens 12 is 4.54 mm, the air gap between the second lens 12 and the third lens 13 is 7.81 mm, the air gap between the third lens 13 and the protective window 14 is 7.56 mm, and the air gap between the protective window 14 and the image plane 15 is 1.5 mm.

[0026] Furthermore, the first lens 11 has a center thickness of 6 mm, an object-side radius of curvature of 19.39 mm, and an image-side radius of curvature of 45.335 mm; the second lens 12 has a center thickness of 2 mm, an object-side radius of curvature of 31.161 mm, and an image-side radius of curvature of 10.069 mm; the third lens 13 has a center thickness of 4.7 mm, an object-side radius of curvature of 37 mm, and an image-side radius of curvature of -79.565 mm; and the protective window 14 has a thickness of 1 mm.

[0027] Based on the above embodiments, it can be determined that the total optical length of the imaging device is 35.11 mm and the back focal length is 10.06 mm.

[0028] In this embodiment, all lenses are made of chalcogenide glass to reduce manufacturing costs.

[0029] Table 1 Data for each component It needs to be explained that, in Figure 1 In the illustrated embodiment, from left to right along the optical axis, the left side is the object side and the right side is the image side. For example, the S1 surface of the first lens 11 is the object side surface and the S2 surface is the image side surface. Other lenses are similar and will not be described in detail here.

[0030] In this embodiment, the image-side surface of the first lens 11, the object-side surface of the second lens 12, and the image-side surface of the third lens 13 are all aspherical surfaces and satisfy the aspherical surface 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 aspherical data are shown in Table 2.

[0031] Table 2 Aspherical Data Please see Figures 2 to 8 , Figure 2 This is the MTF image of the infrared microscope lens at 20℃. Figure 3 This is the MTF image of the infrared microscope lens at -40℃. Figure 4 This is the MTF image of an infrared microscope lens at 80℃; Figure 5 This is a dot plot of an infrared microscope lens at 20°C. Figure 6 This is a dot plot of an infrared microscope lens at -40℃. Figure 7 This is a dot plot of an infrared microscope lens at 80°C. Figure 8 This is a field curvature distortion diagram of the infrared microscope lens. It can be seen that within the operating temperature range of -40℃ to 80℃, the MTF curve of this infrared microscope lens is close to the diffraction limit, and the RMS radius of the dot plot is less than or equal to the Airy disk radius, exhibiting excellent thermal distortion reduction performance. It is suitable for extreme temperature environments and also demonstrates good chromatic aberration correction capability across the entire field of view, resulting in high consistency in image clarity.

[0032] Please also refer to Figures 9 to 11 , Figure 9 This is a diffraction pattern surrounding the energy level of an infrared microscope lens. Figure 10 This is a relative illumination diagram of an infrared microscope lens. Figure 11 This is a vignetting pattern of the infrared microscope lens. It shows that this infrared microscope lens has high energy concentration and high illumination uniformity, making it suitable for detecting weak infrared signals. Furthermore, there is no mechanical obstruction within the lens's light-transmitting area, achieving 100% vignetting efficiency.

[0033] In summary, this application discloses an imaging device, including an infrared microscope head and a detector capable of receiving images from the infrared microscope head. The infrared microscope head has an F-number of 1.0, an operating wavelength of 8~12μm, and an operating temperature of -40℃~+80℃. The magnification β of the infrared microscope head satisfies: 0.11≤β≤0.15, the object-side field of view 2y satisfies: 75mm≤2y≤80mm, the numerical aperture NA satisfies: 0.05≤NA≤0.08, the object-side working distance WD satisfies: 199mm≤WD≤201mm, the horizontal field of view HFOV satisfies: 16°≤HFOV≤18°, and the vertical field of view satisfies: 13°≤VFOV≤14°. The detector is an uncooled infrared detector with a resolution of 640×512 and a pixel size of 12μm. This infrared microscope lens utilizes only three lenses to efficiently reduce the large-size real image formed by the pre-amplifier optical system and project it onto a small-target infrared detector. Its structure is simple and compact, resulting in low manufacturing costs. Furthermore, this infrared microscope lens exhibits excellent aberration correction, high consistency in image sharpness, and stable image quality within its operating temperature range, demonstrating superior thermal distortion mitigation capabilities.

[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. An infrared microscope objective, characterized by The magnification β satisfies: 0.11≤β≤0.15, the object-side field of view 2y satisfies: 75mm≤2y≤80mm, the working wavelength is 8~12μm, and the infrared microscope head is composed of a first lens, a second lens and a third lens arranged sequentially along the optical axis. The first lens is a meniscus positive lens with the convex surface facing the object side, the second lens is a meniscus negative lens with the convex surface facing the object side, and the third lens is a biconvex positive lens. The air gap between the first lens and the second lens is 4.54 mm, and the air gap between the second lens and the third lens is 7.81 mm.

2. The infrared microscope of claim 1, wherein, The first lens has a center thickness of 6 mm, an object-side radius of curvature of 19.39 mm, and an image-side radius of curvature of 45.335 mm; the second lens has a center thickness of 2 mm, an object-side radius of curvature of 31.161 mm, and an image-side radius of curvature of 10.069 mm; the third lens has a center thickness of 4.7 mm, an object-side radius of curvature of 37 mm, and an image-side radius of curvature of -79.565 mm.

3. The infrared microscope lens of claim 1, wherein, The numerical aperture NA of the infrared microscope head satisfies: 0.05≤NA≤0.08, the object working distance WD satisfies: 199mm≤WD≤201mm, the horizontal field of view HFOV satisfies: 16°≤HFOV≤18°, and the vertical field of view VFOV satisfies: 13°≤VFOV≤14°.

4. The infrared microscope head according to claim 1, characterized in that, All lenses are made of chalcogenide glass.

5. The infrared microscope head according to claim 1, characterized in that, The image-side surface of the first lens, the object-side surface of the second lens, and the image-side surface of the third lens are all aspherical surfaces and satisfy the aspherical surface 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 infrared microscope head as described in any one of claims 1-5 and a detector capable of receiving images from the infrared microscope head.

7. The imaging apparatus according to claim 6, characterized in that, The detector has a resolution of 640×512 and a pixel size of 12μm.

8. The imaging apparatus according to claim 6, characterized in that, The imaging device has an optical length of 35.11 mm and a back cutoff of 10.06.

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