A compact short-wave infrared optical lens

Abstract

The application provides a compact short-wave infrared optical lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a prism, a fifth lens and a sixth lens arranged in sequence along the direction from the object side to the image side; the prism comprises a half-pentaprism and an isosceles prism; the object side and the image side of the first lens are both provided with a convex structure; the object side of the second lens is provided with a concave structure, and the image side is provided with a concave structure; the object side of the third lens is provided with a convex structure, and the image side is provided with a concave structure; the object side of the fourth lens is provided with a concave structure, and the image side is provided with a plane structure; the object side of the fifth lens is provided with a concave structure, and the image side is provided with a plane structure; the object side of the sixth lens is provided with a plane structure, and the image side is provided with a convex structure; the light from the object side is reflected five times in the prism, of which three times are total reflection and twice are internal reflection, so as to fold the optical path. The compact short-wave infrared optical lens is compact and small in size.

Description

Technical Field

[0001] This application relates to the field of optical system design technology, specifically to a compact short-wave infrared optical lens. Background Technology

[0002] With the continuous development of technology, short-wave infrared optics is being used more and more widely in many fields such as security monitoring, industrial inspection, and medical diagnosis. However, traditional short-wave infrared optical lenses are usually large in size and long in length, which brings many inconveniences to some application scenarios with strict requirements on equipment size. For example, in portable devices, optical systems carried by drones, and some installation environments with limited space, traditional long optical lenses are difficult to meet practical needs. At the same time, the large size and weight also increase the manufacturing and operating costs of the equipment, limiting its wider application. Summary of the Invention

[0003] In view of the above-mentioned defects or deficiencies in the prior art, this application aims to provide a compact short-wave infrared optical lens, comprising:

[0004] A first lens, a second lens, a third lens, a fourth lens, a Behnken prism, a fifth lens, and a sixth lens are arranged sequentially along the direction from the object side to the image side; wherein the lens surface closer to the object side is the object side surface, and the lens surface closer to the image side is the image side surface; the Behnken prism includes a semi-pentagonal prism closer to the fourth lens side, and an isosceles prism farther from the fourth lens side of the semi-pentagonal prism.

[0005] Both the object-side and image-side surfaces of the first lens are convex.

[0006] The object side of the second lens is concave, and the image side is also concave.

[0007] The object side of the third lens is convex, and the image side is concave.

[0008] The object-side surface of the fourth lens is concave, and the image-side surface is planar.

[0009] The object side of the fifth lens is concave, and the image side is planar.

[0010] The object-side surface of the sixth lens is a planar structure, and the image-side surface is a convex structure.

[0011] The light rays from the object undergo five reflections inside the prism, including three total internal reflections and two internal reflections, in order to fold the light path.

[0012] According to the technical solution provided in the embodiments of this application, the optical material of the first lens is ZLAF78, the radius of the object side is 55mm, the light-transmitting aperture is φ40mm, the radius of the image side is 742mm, the light-transmitting aperture is φ39.3mm, and the thickness is 6mm.

[0013] According to the technical solution provided in the embodiments of this application, the second lens is made of ZF88 optical material, with an object side radius of 502mm and a light-transmitting aperture of φ39mm; an image side radius of φ36.4mm and a light-transmitting aperture of 39.9mm; and a thickness of 2.25mm.

[0014] According to the technical solution provided in the embodiments of this application, the optical material of the third lens is ZLAF56, the radius of the object side is 38.95mm, the light-transmitting aperture is φ36.6mm, the radius of the image side is 278mm, the light-transmitting aperture is φ36mm, and the thickness is 6mm.

[0015] According to the technical solution provided in the embodiments of this application, the optical material of the fourth lens is LAF7, the radius of the object side is 45.7mm, the light-transmitting aperture is φ19.3mm, the image side is flat, the light-transmitting aperture is φ19mm, and the thickness is 1.8mm.

[0016] According to the technical solution provided in the embodiments of this application, the optical material of the semi-pentagonal prism is F51, which has three first working surfaces, and all three first working surfaces are planes. The light undergoes three folds inside, and the optical axis lengths are 10mm, 14.14mm and 10mm, respectively. The light transmission apertures of the three first working surfaces are φ18mm, φ29.6mm and φ17mm, respectively.

[0017] According to the technical solution provided in the embodiments of this application, the isosceles prism optical material is F51, has three second working surfaces, and all three second working surfaces are planes. The light undergoes four folds inside, and the optical axis lengths are 10mm, 14.14mm, 10mm and 10mm respectively. The light transmission apertures of the three second working surfaces are φ18mm, φ11mm and φ26mm respectively.

[0018] According to the technical solution provided in the embodiments of this application, the optical material of the fifth lens is ZLAF78, the radius of the object side is 12.2mm, the light-transmitting aperture is φ8.5mm; the image side is flat, the light-transmitting aperture is φ9mm; and the thickness is 1.5mm.

[0019] According to the technical solution provided in the embodiments of this application, the optical material of the sixth lens is ZF88, the object side is flat, the light-transmitting aperture is φ13.3mm; the radius of the image side is 19.2mm, the light-transmitting aperture is φ13.8mm; and the thickness is 3.2mm.

[0020] According to the technical solution provided in the embodiments of this application, the distance between the first lens and the second lens is 0.65 mm; the distance between the second lens and the third lens is 0.5 mm; the distance between the third lens and the fourth lens is 35.41 mm; the distance between the fourth lens and the semi-pentagonal prism is 2 mm; the distance between the semi-pentagonal prism and the isosceles prism is 1 mm; the distance between the isosceles prism and the fifth lens is 1.73 mm; and the distance between the fifth lens and the sixth lens is 7.6 mm.

[0021] In summary, this application proposes a compact short-wave infrared optical lens, comprising a first lens, a second lens, a third lens, a fourth lens, a Behnken prism, a fifth lens, and a sixth lens arranged sequentially along the object-side to image-side direction. The Behnken prism includes a semi-pentagonal prism near the fourth lens and an isosceles prism away from the fourth lens. The object-side and image-side surfaces of the first lens are both convex. The object-side and image-side surfaces of the second lens are both concave. The object-side and image-side surfaces of the third lens are both convex. The object-side and image-side surfaces of the fourth lens are both concave. The object-side and image-side surfaces of the fifth lens are both concave. The object-side and image-side surfaces of the sixth lens are both planar. The light rays from the object side undergo five reflections inside the Behnken prism, including three total internal reflections and two internal reflections, to fold the light path.

[0022] Compared with existing technologies, the advantages of this application are as follows: By introducing a Behan prism into the optical system and utilizing its internal five reflections (three total internal reflections and two internal reflections) to fold the optical path, this application effectively shortens the overall system length, making the short-wave infrared optical lens more compact and miniaturized. This meets the application scenarios with strict requirements on device size, such as portable devices and space-constrained installation environments. At the same time, the object-side and image-side surfaces of each lens adopt specific convex, concave, and planar structures, which work in conjunction with the Behan prism to optimize optical performance and ensure image quality. The Behan prism uses a combination of a semi-pentagonal prism and an isosceles prism, which reduces system weight and overall device weight while ensuring optical performance, making it easier to install and use. This compact and miniaturized short-wave infrared optical lens can be better applied to multiple fields such as security monitoring, industrial inspection, and medical diagnosis, providing strong support for the technological development of these fields. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a compact short-wave infrared optical lens provided in an embodiment of this application;

[0024] Figure 2Optical path diagram of a compact short-wave infrared optical lens provided in the embodiments of this application;

[0025] Figure 3 The equivalent system diagram of the compact short-wave infrared optical lens provided in the embodiments of this application is the optical path diagram after the Beyhan prism in the optical path is equivalent to a parallel plate;

[0026] Figure 4 MTF curve of the compact short-wave infrared optical lens provided in the embodiments of this application at +20°C;

[0027] Figure 5 MTF curve of a compact short-wave infrared optical lens provided in this application embodiment at -45°C;

[0028] Figure 6 MTF curve of the compact short-wave infrared optical lens provided in the embodiments of this application at 80°C;

[0029] Figure 7 A dot plot of a compact short-wave infrared optical lens provided in an embodiment of this application at +20°C;

[0030] Figure 8 A dot plot of a compact short-wave infrared optical lens provided in an embodiment of this application at -45°C;

[0031] Figure 9 Dot plot of a compact short-wave infrared optical lens provided in an embodiment of this application at 80°C;

[0032] Figure 10 The distortion curve of the compact short-wave infrared optical lens provided in the embodiments of this application at room temperature.

[0033] The text labels in the image represent:

[0034] 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Semi-pentagonal prism; 6. Isosceles prism; 7. Fifth lens; 8. Sixth lens. Detailed Implementation

[0035] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] Example 1

[0038] As mentioned in the background section, this application proposes a compact short-wave infrared optical lens to address the problems in the prior art. Please refer to [link / reference]. Figure 1 As shown, the system includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a Behnken prism, a fifth lens 7, and a sixth lens 8 arranged sequentially along the direction from the object side to the image side; wherein the lens surface closer to the object side is the object-side surface, and the lens surface closer to the image side is the image-side surface; the Behnken prism includes a semi-pentagonal prism 5 close to the fourth lens 4, and an isosceles prism 6 on the side of the semi-pentagonal prism 5 away from the fourth lens 4;

[0039] Both the object-side and image-side surfaces of the first lens 1 are convex.

[0040] The object side of the second lens 2 is concave, and the image side is also concave.

[0041] The object side of the third lens 3 is convex, and the image side is concave.

[0042] The object side of the fourth lens 4 is a concave structure, and the image side is a planar structure.

[0043] The object-side surface of the fifth lens 7 is concave, and the image-side surface is planar.

[0044] The object-side surface of the sixth lens 8 is a planar structure, and the image-side surface is a convex structure.

[0045] The light rays from the object undergo five reflections inside the prism, including three total internal reflections and two internal reflections, in order to fold the light path.

[0046] Specifically, the Böhne prism is made of F51 material with a lower density and a slightly higher refractive index, which helps to reduce the system weight, decrease the critical angle of total internal reflection, and improve optical efficiency.

[0047] Please refer to Figure 2 As shown, the optical system employs a Behring prism folding optical path, with a total length of 103mm and a total length-to-focal-length ratio of 0.343. Please refer to [reference needed]. Figure 3 As shown, after the Biehan prism is equivalent to a parallel plate, the equivalent length of the optical system is 171mm, and the total length is shortened by 40%.

[0048] Specifically, all optical elements in this embodiment are made of Chengdu Guangming colorless optical materials with high transmittance in the 1.1μm-1.7μm wavelength range, with the density of the semi-pentagonal prism 5 and the isosceles prism 6 being 2.76 g / cm³. 3With a refractive index nd = 1.6398 and a critical angle for total internal reflection of 37.58°, the critical angle for total internal reflection is reduced by 3.67° compared to K9 material. This increases the proportion of light rays undergoing total internal reflection at the edge of the field of view, thereby improving the system's optical efficiency. The optical system operates in a temperature range of -45℃ to +80℃, and the structural components are made of titanium alloy, enabling a passive, calorimetric design without the need for focusing.

[0049] Furthermore, when using this compact short-wave infrared optical lens, a mid-wave cooled detector with a 640×512 array, a single pixel size of 15μm, and a high-frequency transfer function (MTF) value of 33lp / mm line pairs for image quality assessment are used in conjunction.

[0050] Specifically, the optical lens proposed in this embodiment has the following operating band / wavelength: 1.1μm~1.7μm; field of view: 2ω=2.3°; focal length: f=300mm; lens F number: 7.5; operating temperature range: -45℃~+80℃; distortion: ≤1%; detector array: 640×512; single detector element area: 15μm×15μm; image quality requirements: full field of view MTF@33lp / mm≥0.3.

[0051] In a preferred embodiment, the first lens 1 is made of ZLAF78 optical material, has an object side radius of 55mm and a light-transmitting aperture of φ40mm; an image side radius of 742mm and a light-transmitting aperture of φ39.3mm; and a thickness of 6mm.

[0052] Specifically, ZLAF78 is designated as heavy lanthanum flint 78.

[0053] In a preferred embodiment, the second lens 2 is made of ZF88 optical material, with an object-side radius of 502 mm and a light-transmitting aperture of φ39 mm; an image-side radius of φ36.4 mm and a light-transmitting aperture of 39.9 mm; and a thickness of 2.25 mm.

[0054] Specifically, ZF88 is represented as Heavy Firestone 88.

[0055] In a preferred embodiment, the third lens 3 is made of ZLAF56 optical material, with an object-side radius of 38.95 mm and a light-transmitting aperture of φ36.6 mm; an image-side radius of 278 mm and a light-transmitting aperture of φ36 mm; and a thickness of 6 mm.

[0056] Specifically, ZLAF56 is designated as heavy lanthanum flint 56.

[0057] In a preferred embodiment, the fourth lens 4 is made of LAF7 optical material, has an object side radius of 45.7 mm, a light-transmitting aperture of φ19.3 mm, an image side that is flat, a light-transmitting aperture of φ19 mm, and a thickness of 1.8 mm.

[0058] Specifically, LAF7 stands for Lanthanum Firestone 7.

[0059] In a preferred embodiment, the optical material of the semi-pentagonal prism 5 is F51, and it has three first working surfaces, all of which are planar. The light undergoes three folds inside, and the optical axis lengths are 10mm, 14.14mm and 10mm, respectively. The light transmission apertures of the three first working surfaces are φ18mm, φ29.6mm and φ17mm, respectively.

[0060] In a preferred embodiment, the isosceles prism 6 is made of F51 optical material and has three second working surfaces, all of which are planar. The light undergoes four folds inside, and the optical axis lengths are 10mm, 14.14mm, 10mm and 10mm respectively. The light-transmitting apertures of the three second working surfaces are φ18mm, φ11mm and φ26mm respectively.

[0061] Specifically, F51 is referred to as Flint 51.

[0062] In a preferred embodiment, the fifth lens 7 is made of ZLAF78 optical material, with an object-side radius of 12.2 mm and a light-transmitting aperture of φ8.5 mm; the image-side is flat with a light-transmitting aperture of φ9 mm; and the thickness is 1.5 mm.

[0063] In a preferred embodiment, the sixth lens 8 is made of ZF88 optical material, has a flat object side with a light-transmitting aperture of φ13.3mm, an image side radius of 19.2mm with a light-transmitting aperture of φ13.8mm, and a thickness of 3.2mm.

[0064] In a preferred embodiment, the distance between the first lens 1 and the second lens 2 is 0.65 mm; the distance between the second lens 2 and the third lens 3 is 0.5 mm; the distance between the third lens 3 and the fourth lens 4 is 35.41 mm; the distance between the fourth lens 4 and the semi-pentagonal prism 5 is 2 mm; the distance between the semi-pentagonal prism 5 and the isosceles prism 6 is 1 mm; the distance between the isosceles prism 6 and the fifth lens 7 is 1.73 mm; and the distance between the fifth lens 7 and the sixth lens 8 is 7.6 mm.

[0065] Specifically, Figures 3-5 To simulate the MTF curve of the optical lens using Code V optical design software, the design inputs were wavelengths of 1.1μm, 1.4μm, and 1.7μm, and half-fields of view of 0°, 0.35°, 0.59°, 0.82°, 1.0°, and 1.15°. As can be seen from the figure, the optical lens has an MTF@33lp / mm≥0.4 across the entire temperature range and the entire field of view, and the MTF curve is close to the diffraction limit, indicating good image quality correction.

[0066] Specifically, Figures 6-8 To simulate the optical lens dot plot using Code V optical design software, the design inputs were wavelengths of 1.1 μm, 1.4 μm, and 1.7 μm, with half-fields of view of 0°, 0.35°, 0.59°, 0.82°, 1.0°, and 1.15°. The figure shows that the optical lens exhibits good convergence of the speckle across the entire temperature range and field of view, with the RMS diameter of the speckle within one pixel across the entire field of view, indicating high system resolution.

[0067] Specifically, Figure 9 To simulate the distortion pattern of a room-temperature optical lens using Code V optical design software, the inputs were wavelengths of 1.1 μm, 1.4 μm, and 1.7 μm, with half-fields of view of 0°, 0.35°, 0.59°, 0.82°, 1.0°, and 1.15°. The horizontal axis represents the magnitude of distortion, and the vertical axis represents different fields of view. Table 1 lists the distortion magnitude of the optical lens at different temperatures and fields of view. Table 1 shows that the maximum distortion of this optical lens is less than 1% across the entire temperature range and field of view.

[0068] Table 1. Distortion of optical lenses at different temperatures and fields of view.

[0069]

[0070] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A compact short-wave infrared optical lens, characterized in that, It consists of a first lens (1), a second lens (2), a third lens (3), a fourth lens (4), a Behnken prism, a fifth lens (7), and a sixth lens (8) arranged sequentially along the direction from the object side to the image side; wherein the lens surface closer to the object side is the object side surface, and the lens surface closer to the image side is the image side surface; the Behnken prism includes a semi-pentagonal prism (5) closer to the fourth lens (4) and an isosceles prism (6) on the side of the semi-pentagonal prism (5) away from the fourth lens (4); The object side and image side of the first lens (1) are both convex structures; The object side of the second lens (2) is concave, and the image side is also concave. The object side of the third lens (3) is convex, and the image side is concave. The object side of the fourth lens (4) is set with a concave structure, and the image side is set with a planar structure; The object side of the fifth lens (7) is set with a concave structure, and the image side is set with a planar structure; The object side of the sixth lens (8) is a planar structure, and the image side is a convex structure. The light rays from the object undergo five reflections inside the prism, including three total internal reflections and two internal reflections, in order to fold the light path. The first lens (1) is made of ZLAF78 optical material, with an object side radius of 55mm and a light-transmitting aperture of φ40mm; an image side radius of 742mm and a light-transmitting aperture of φ39.3mm; and a thickness of 6mm. The second lens (2) is made of ZF88 optical material, with an object side radius of 502mm and a light-transmitting aperture of φ39mm; an image side radius of φ36.4mm and a light-transmitting aperture of 39.9mm; and a thickness of 2.25mm. The third lens (3) is made of ZLAF56 optical material, with an object side radius of 38.95 mm and a light-transmitting aperture of φ36.6 mm; an image side radius of 278 mm and a light-transmitting aperture of φ36 mm; and a thickness of 6 mm. The fourth lens (4) is made of LAF7 optical material, with an object side radius of 45.7 mm and a light-transmitting aperture of φ19.3 mm; the image side is flat with a light-transmitting aperture of φ19 mm; and the thickness is 1.8 mm. The optical material of the semi-pentagonal prism (5) is F51, and it has three first working surfaces, all of which are planes. The light undergoes three folds inside, and the optical axis lengths are 10mm, 14.14mm and 10mm, respectively. The light-transmitting apertures of the three first working surfaces are φ18mm, φ29.6mm and φ17mm, respectively. The isosceles prism (6) is made of F51 optical material and has three second working surfaces, all of which are planes. The light undergoes four folds inside, and the optical axis lengths are 10mm, 14.14mm, 10mm and 10mm respectively. The light-transmitting apertures of the three second working surfaces are φ18mm, φ11mm and φ26mm respectively. The fifth lens (7) is made of ZLAF78 optical material, with an object side radius of 12.2 mm and a light-transmitting aperture of φ8.5 mm; the image side is flat with a light-transmitting aperture of φ9 mm; and the thickness is 1.5 mm. The sixth lens (8) is made of ZF88 optical material, with a flat object side and a light-transmitting aperture of φ13.3mm; the image side has a radius of 19.2mm and a light-transmitting aperture of φ13.8mm; and a thickness of 3.2mm.

2. The compact short-wave infrared optical lens according to claim 1, characterized in that: The distance between the first lens (1) and the second lens (2) is 0.65 mm; the distance between the second lens (2) and the third lens (3) is 0.5 mm; the distance between the third lens (3) and the fourth lens (4) is 35.41 mm; the distance between the fourth lens (4) and the semi-pentagonal prism (5) is 2 mm; the distance between the semi-pentagonal prism (5) and the isosceles prism (6) is 1 mm; the distance between the isosceles prism (6) and the fifth lens (7) is 1.73 mm; and the distance between the fifth lens (7) and the sixth lens (8) is 7.6 mm.

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