Miniaturized infrared athermal optical system with large target surface and high resolution

Abstract

This invention relates to a miniaturized, large-target, high-resolution infrared thermal ablation optical system. The optical system comprises a first meniscus negative lens, a first meniscus positive lens, a fixed aperture, a second meniscus negative lens, a biconvex positive lens, and a second meniscus positive lens, arranged coaxially from the object side to the image side. The optical structure adopts a reverse telescopic structure, achieving a large-target optical system with a field of view of 40.0° x 32.5° and a target size of 19.7 mm. It can be adapted to a high-resolution long-wave infrared detector with a pixel count of 1280 x 1024 and a pixel pitch of 12 μm. Through the rational allocation of the optical power of each lens and the coordination of the lens optical materials, a thermal ablation optical system that can achieve good imaging over a wide temperature range of -55℃ to +70℃ is achieved. While achieving thermal ablation over a wide temperature range, the system length is shortened, thereby enabling miniaturization and reducing the weight of the entire device. In addition, the system has a large back working distance, which facilitates the design of the back-end calibration plate and detector mounting structure.

Description

Technical Field

[0001] This invention relates to the field of uncooled infrared imaging optical systems, and more specifically to a miniaturized, large-target, high-resolution infrared thermochromic optical system. Background Technology

[0002] In recent years, with the advancement of infrared detector manufacturing technology, uncooled infrared detectors have achieved high resolution by increasing array size and reducing pixel spacing while improving sensitivity and frame rate. This has enhanced the target detection and recognition capabilities of uncooled infrared systems, making it possible for uncooled infrared systems to be widely used in various military and civilian fields.

[0003] Internationally, Raytheon in the US has developed a large-area uncooled infrared detector with an array size of 2048×1536 and a pixel pitch of 17μm, while BAE Systems in the UK has developed a large-area uncooled infrared detector with an array size of 1920×1200 and a pixel pitch of 12μm. Domestically, Wuhan Guide Infrared Co., Ltd. has achieved mass production of a long-wavelength uncooled infrared detector with an array size of 1280×1024 and a pixel pitch of 12μm, and Yantai IRay Optoelectronics Technology Co., Ltd. has also developed a vanadium oxide uncooled infrared focal plane array detector with an array size of 1280×1024 and a pixel pitch of 12μm, suitable for various high-end military and civilian applications.

[0004] In engineering applications, large-area infrared detectors require infrared optical lenses with corresponding target surfaces; otherwise, black corners will appear in the system's output image. Therefore, when designing an infrared optical system, the target surface size should not be smaller than the target surface size of the selected infrared detector. Thus, researching a large-target-surface optical system capable of accommodating 1280×1024 long-wavelength uncooled detectors is of practical significance.

[0005] Furthermore, since the refractive index of infrared optical materials varies significantly with temperature, changes in the operating environment temperature of an infrared optical system can cause image plane drift, leading to a decrease in image quality. Therefore, for infrared optical systems with large temperature variations in their operating environment, thermal differential design is required to eliminate or reduce the temperature-induced reduction in image quality, ensuring that the optical system maintains good imaging performance over a wide temperature range. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a miniaturized, large-target-area, high-resolution infrared thermochromic optical system.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A miniaturized, large-target, high-resolution infrared thermochromic optical system is disclosed. The optical system comprises a first meniscus negative lens, a first meniscus positive lens, a second meniscus negative lens, a biconvex positive lens, and a second meniscus positive lens arranged coaxially from the object side to the image side. The first meniscus negative lens and the first meniscus positive lens are both bent towards the image side, while the second meniscus negative lens and the second meniscus positive lens are bent towards the object side. A fixed aperture is provided between the first meniscus positive lens and the second meniscus negative lens.

[0009] Furthermore, the first meniscus negative lens is made of single-crystal germanium (Ge), the first meniscus positive lens and the biconvex positive lens are both made of chalcogenide glass (IRG204), and the second meniscus negative lens and the second meniscus positive lens are both made of chalcogenide glass (IRG206).

[0010] Furthermore, the system's back working distance BFL, i.e. the distance between the back surface of the second meniscus positive lens and the imaging plane, satisfies the following condition: 13.8mm≤BFL≤16.0mm.

[0011] Furthermore, the optical system satisfies the following conditions: -3.5≤f1 / f≤-3.0, 1.3≤f2 / f≤1.5, -1.3≤f4 / f≤-1.1, 0.8≤f5 / f≤1.0, 1.9≤f6 / f≤2.1, where f is the focal length of the optical system, f1 is the effective focal length of the first meniscus negative lens, f2 is the effective focal length of the first meniscus positive lens, f4 is the effective focal length of the second meniscus negative lens, f5 is the effective focal length of the biconvex positive lens, and f6 is the effective focal length of the second meniscus positive lens.

[0012] Furthermore, the distance on the optical axis between the first meniscus negative lens and the first meniscus positive lens is T. 12 The distance on the optical axis between the first meniscus positive lens and the second meniscus negative lens is T. 24 The thickness of the first meniscus positive lens on the optical axis is CT2, satisfying the following condition: 5.0 ≤ (T 12 +T 24 ) / CT2≤5.5.

[0013] Furthermore, the exit surface of the first meniscus positive lens, the incident surface of the biconvex positive lens, and the incident surface of the second meniscus positive lens are all aspherical.

[0014] Furthermore, the exit surface of the second meniscus negative lens is a diffractive aspherical surface.

[0015] Furthermore, the technical parameters achieved by the optical system are as follows: operating wavelength: 8μm~12μm; F #: 1.0; Field of view: 40.0° × 32.5°, Image plane diameter: Φ19.7mm, Total optical length: 67mm, where F # The calculation formula is f / D, where f is the focal length of the optical system and D is the diameter of the entrance pupil.

[0016] Beneficial effects:

[0017] 1. The optical structure of this invention adopts an anti-long-range structure, realizing a large target surface optical system with a field of view of 40.0°×32.5° and a target surface size of 19.7mm, which can be adapted to a high-resolution long-wave infrared detector with a pixel count of 1280×1024 and a pixel pitch of 12μm.

[0018] 2. In this invention, the first meniscus positive lens and the biconvex positive lens are both made of chalcogenide glass material with a low refractive index temperature coefficient of IRG204, and the second meniscus negative lens and the second meniscus positive lens are both made of chalcogenide glass material with a low refractive index temperature coefficient of IRG206. This achieves a thermodifference-reducing optical system that can produce good images in a wide temperature range of -55℃ to +70℃. There is no need to set up a separate focusing mechanism to compensate for the decrease in image quality caused by temperature changes in the optical system, which effectively simplifies the system structure.

[0019] 3. By optimizing the spacing between lenses, rationally allocating the optical power of each lens, and coordinating the optical materials of the lenses, the system length is shortened while achieving thermal aberration reduction over a wide temperature range. The total optical length (distance from the front surface of the first lens to the image plane) is 67mm, which enables miniaturization and reduces the weight of the entire device. In addition, the system has a large rear working distance, which facilitates the design of the installation structure of the back-end calibration plate and detector. Attached Figure Description

[0020] Figure 1 This is the optical path diagram of the optical system;

[0021] Figure 2 The graph shows the transfer function of the optical system at room temperature (20℃).

[0022] Figure 3 The transfer function of the optical system at a low temperature of -55℃ is shown in the graph.

[0023] Figure 4 The transfer function of the optical system at a high temperature of 70°C is shown in the graph.

[0024] Figure 5 A dot plot of the optical system at room temperature (20°C);

[0025] Figure 6 A dot plot of the optical system at a low temperature of -55°C;

[0026] Figure 7 A dot plot of the optical system at a high temperature of 70°C;

[0027] Figure 8 Field curvature and distortion diagram of an optical system.

[0028] Reference numerals in the attached figures: 1 is the first meniscus negative lens, 2 is the first meniscus positive lens, 3 is the fixed aperture, 4 is the second meniscus negative lens, 5 is the biconvex positive lens, 6 is the second meniscus positive lens, and 7 is the image plane. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings. The purpose of disclosing this invention is to protect all technical improvements within the scope of this invention. In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," and "right," etc., indicating orientation or positional relationships, are merely for the purpose of describing the invention and do not indicate or imply that the device or element referred to must have a specific orientation.

[0030] like Figure 1 The miniaturized large-target high-resolution infrared thermochromic optical system shown consists of a first meniscus negative lens 1, a first meniscus positive lens 2, a fixed aperture 3, a second meniscus negative lens 4, a biconvex positive lens 5, and a second meniscus positive lens 6 arranged sequentially from the object side to the image side.

[0031] As is common knowledge, the direction closer to object space is called the object side, and the direction closer to image space is called the image side. From the object side to the image side, the two sides of the lens are the incident surface and the exit surface, respectively.

[0032] The terms “first,” “second,” and “third” are used for descriptive purposes only, referring to the order in which lenses of this type appear, and should not be construed as indicating or implying relative importance.

[0033] The first meniscus negative lens 1, the first meniscus positive lens 2, the second meniscus negative lens 4, the biconvex positive lens 5, and the second meniscus positive lens 6 are arranged coaxially from the object side to the image side. The first meniscus negative lens 1 and the first meniscus positive lens 2 are both curved towards the image side; the second meniscus negative lens 4 and the second meniscus positive lens 6 are curved towards the object side; a fixed aperture 3 is provided between the first meniscus positive lens 2 and the second meniscus negative lens 4.

[0034] Preferably, the first meniscus negative lens 1 is made of single-crystal germanium (Ge), the first meniscus positive lens 2 and the biconvex positive lens 5 are both made of chalcogenide glass IRG204, and the second meniscus negative lens 4 and the second meniscus positive lens 6 are both made of chalcogenide glass IRG206.

[0035] Furthermore, the system's back working distance is 13.8mm≤BFL≤16.0mm, meaning that the distance between the back surface S10 of the second meniscus positive lens 6 and the imaging surface 7 satisfies the following condition: 13.8mm≤BFL≤16.0mm.

[0036] The specific light transmission path of the optical system of the present invention is as follows: the light emitted by the infrared radiation of the external scene is diverged by the first meniscus negative lens 1 and reaches the first meniscus positive lens 2. After being converged by the first meniscus positive lens 2, it passes through the fixed aperture 3 and reaches the second meniscus negative lens 4. After being diverged by the second meniscus negative lens 4, it reaches the biconvex positive lens 5. After being converged by the biconvex positive lens 5, it reaches the second meniscus positive lens 6. After being converged by the second meniscus positive lens 6, it is imaged on the image plane 7.

[0037] Preferably, the first meniscus negative lens 1 satisfies the following condition: -3.5≤f1 / f≤-3.0, where f is the focal length of the optical system and f1 is the effective focal length of the first meniscus negative lens 1;

[0038] The first meniscus positive lens 2 satisfies the following condition: 1.3≤f2 / f≤1.5, where f is the focal length of the optical system and f2 is the effective focal length of the first meniscus positive lens 2;

[0039] The second meniscus negative lens 4 satisfies the following condition: -1.3≤f4 / f≤-1.1, where f is the focal length of the optical system and f4 is the effective focal length of the second meniscus negative lens 4;

[0040] The biconvex positive lens 5 satisfies the following condition: 0.8≤f5 / f≤1.0, where f is the focal length of the optical system and f5 is the effective focal length of the biconvex positive lens 5;

[0041] The second meniscus positive lens 6 satisfies the following condition: 1.9≤f6 / f≤2.1, where f is the focal length of the optical system and f6 is the effective focal length of the second meniscus positive lens 6.

[0042] Furthermore, the distance on the optical axis between the first meniscus negative lens 1 and the first meniscus positive lens 2 is T12, the distance on the optical axis between the first meniscus positive lens 2 and the second meniscus negative lens 4 is T24, and the thickness of the first meniscus positive lens 2 on the optical axis is CT2, satisfying the following condition: 5.0≤(T12+T24) / CT2≤5.5.

[0043] Table 1 shows the technical specifications of the present invention, where F # The formula for calculating the F-number of an optical system is f / D, where f is the focal length of the optical system and D is the diameter of the entrance pupil.

[0044] Table 1. Performance Indicators of the Optical System

[0045] parameter Technical indicators detector 1280×1024 Uncooled Infrared Detector Pixel size 12μm Operating band 8μm~12μm <![CDATA[F # (F-number of the optical system) 1.0 Field of view 40.0°×32.5° Image plane diameter Φ19.7mm

[0046] Table 2 lists detailed data of the optical system embodiments according to the present invention, including the surface shape, radius of curvature, thickness, and material of each lens. The units for the radius of curvature and thickness of the lens are mm. The radius of curvature of spherical and aspherical surfaces refers to the radius of curvature at the intersection of the lens surface and the optical axis. The "surface number" in Table 2 is counted along the direction of light propagation. For example, the beam incident surface of the first meniscus negative lens 1 is numbered S1, and the beam exit surface is numbered S2. Other mirror surface numbers follow the same pattern. The curved surfaces of the first meniscus negative lens 1, the first meniscus positive lens 2, the second meniscus negative lens 4, the biconvex positive lens 5, and the second meniscus positive lens 6 along the object-to-image direction are respectively marked as S1, S2, S3, S4, S5, S6, S7, S8, S9, and S10. The "radius" in Table 2 represents the radius of curvature of the surface. The positive or negative sign is determined by taking the intersection of the surface and the principal optical axis as the starting point and the center of the curved surface as the ending point. If the direction of the connecting line is the same as the direction of light propagation, it is positive; otherwise, it is negative. If the surface is planar, its radius of curvature is infinite. The "Thickness" in Table 2 gives the distance between two adjacent surfaces on the optical axis. The sign is determined by taking the vertex of the current surface as the starting point and the vertex of the next surface as the ending point. If the direction of the connecting line is the same as the direction of light propagation, it is positive; otherwise, it is negative. If the material between the two surfaces is infrared material, the thickness represents the lens thickness; if there is no material between the two surfaces, it represents the air gap between the two lenses.

[0047] Table 2 Detailed data of the embodiments of the present invention

[0048]

[0049] Furthermore, in the miniaturized large-target high-resolution infrared thermochromic optical system of the present invention, the exit surface S4 of the first meniscus positive lens 2, the incident surface S7 of the biconvex positive lens 5, and the incident surface S9 of the second meniscus positive lens 6 are all aspherical surfaces.

[0050] The surface equations of the above aspherical surfaces are as follows:

[0051]

[0052] Where z is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis, c is the curvature, c = 1 / R, R represents the radius of curvature of the lens surface, r is the radial coordinate perpendicular to the optical axis, k is the quadratic curve constant, A is the fourth-order aspherical coefficient, B is the sixth-order aspherical coefficient, and C is the eighth-order aspherical coefficient.

[0053] Table 3 lists the aspherical coefficients of the exit surface S4 of the first meniscus positive lens 2, the incident surface S7 of the biconvex positive lens 5, and the incident surface S9 of the second meniscus positive lens 6 according to the present invention. The table uses scientific notation; for example, -1.064777e-005 represents -1.064777 × 10⁻⁶. -5 .

[0054] Table 3 Aspheric coefficients in this invention

[0055]

[0056] Furthermore, the exit surface S6 of the second meniscus negative lens 4 is aspherical, and a continuous relief structure is formed on the aspherical substrate by diamond turning to create a diffraction surface, which satisfies the following equation:

[0057]

[0058] Where z is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis, c is the curvature (c = 1 / R), where R represents the radius of curvature of the lens surface, r is the radial coordinate perpendicular to the optical axis, k is the quadratic curve constant, A is the fourth-order aspherical coefficient, B is the sixth-order aspherical coefficient, and C is the eighth-order aspherical coefficient; HOR is the diffraction order, C1, C2, and C3 are the diffraction surface coefficients, λ0 is the designed center wavelength, n is the refractive index of the lens, and n0 is the air refractive index.

[0059] Table 4 lists the diffraction aspheric coefficients of the exit surface S6 of the second meniscus negative lens 4 according to the present invention.

[0060] Table 4. Diffraction Aspheric Coefficients

[0061]

[0062] After simulation using optical design software, such as Figure 2 , Figure 3 , Figure 4 As shown, when using an uncooled detector with a pixel size of 12μm and a pixel count of 1280×1024, corresponding to a spatial frequency of 42lp / mm, the transfer function of the optical system is greater than 0.3 at normal temperature (20℃), low temperature (-55℃), and high temperature (70℃). Figure 5 , Figure 6 , Figure 7 The figure shows the dot plots of the optical system at room temperature (20℃), low temperature (-55℃), and high temperature (70℃). As can be seen from the figure, the diameter of the diffuse spot of the system is smaller than the diameter of the Airy spot. Figure 8 The figure shows the field curvature and distortion of the optical system. As can be seen from the figure, the distortion at the edge of the field of view is less than 2.2%.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A miniaturized, large-target-area, high-resolution infrared thermochromic optical system, characterized in that, The optical system consists of a first meniscus negative lens, a first meniscus positive lens, a second meniscus negative lens, a biconvex positive lens, and a second meniscus positive lens arranged coaxially from the object side to the image side. The first meniscus negative lens and the first meniscus positive lens are both bent towards the image side, while the second meniscus negative lens and the second meniscus positive lens are bent towards the object side. A fixed aperture is provided between the first meniscus positive lens and the second meniscus negative lens. The focal lengths of the lenses mentioned above must meet the following conditions: -3.5≤ f 1 / f ≤-3.0，1.3≤ f 2 / f ≤1.5，-1.3≤ f 4 / f ≤-1.1，0.8≤ f 5 / f ≤1.0，1.9≤ f 6 / f ≤2.1； in f The focal length of the optical system; f 1 represents the effective focal length of the first meniscus negative lens; f 2 represents the effective focal length of the first meniscus positive lens; f 4 represents the effective focal length of the second meniscus negative lens; f 5 represents the effective focal length of the biconvex positive lens; f 6 represents the effective focal length of the second meniscus positive lens; A distance on the optical axis between the first meniscus negative lens and the first meniscus positive lens is T 12 A distance on the optical axis between the first meniscus positive lens and the second meniscus negative lens is T 24 A thickness on the optical axis of the first meniscus positive lens is CT2, satisfying the following condition: 5.0 ≤ (T 12 + T 24 ) / CT2 ≤ 5.

5.

2. The miniaturized large-target-area high-resolution infrared thermochromic aberration optical system according to claim 1, characterized in that, The first meniscus negative lens is made of single-crystal germanium (Ge), the first meniscus positive lens and the biconvex positive lens are both made of chalcogenide glass IRG204, and the second meniscus negative lens and the second meniscus positive lens are both made of chalcogenide glass IRG206.

3. The miniaturized large-target-area high-resolution infrared thermochromic optical system according to claim 1, characterized in that, The system's back working distance BFL, which is the distance between the back surface of the second meniscus positive lens and the imaging plane, satisfies the following condition: 13.8mm≤BFL≤16.0mm.

4. The miniaturized large-target-area high-resolution infrared thermochromic aberration optical system according to claim 1, characterized in that, The exit surface of the first meniscus positive lens, the incident surface of the biconvex positive lens, and the incident surface of the second meniscus positive lens are all aspherical.

5. The miniaturized large-target-area high-resolution infrared thermochromic optical system according to claim 1, characterized in that, The exit surface of the second meniscus negative lens is a diffractive aspherical surface.

6. The miniaturized large-target-area high-resolution infrared thermochromic optical system according to claim 1, characterized in that, The technical parameters achieved by the optical system are: operating wavelength: 8μm~12μm; F # :1.0; Field of view 40.0° 32.5°, image plane diameter: Φ19.7mm, total optical length: 67mm, of which, F # The calculation formula is f / D , f The focal length of the optical system. D The diameter is the entrance pupil.

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