A high-resolution long-wave infrared continuous zoom optical system

Abstract

This invention relates to a high-resolution long-wave infrared continuous zoom optical system, comprising a first meniscus positive lens, a biconcave negative lens, a biconvex positive lens, a first meniscus negative lens, a second meniscus negative lens, and a second meniscus positive lens arranged coaxially from the object side to the image side. The biconcave negative lens is a zoom lens, and the biconvex positive lens is a compensation lens. Through the reasonable allocation of the optical power of each lens and the optimized setting of the positions of the aspherical and diffraction surfaces, the optical system achieves continuous zoom within the range of 30mm to 150mm while realizing a large target surface design. It can be adapted to new high-resolution long-wave detectors with a resolution of 1024x768 and a pixel spacing of 12μm and a resolution of 1280x1024 and a pixel spacing of 12μm. It has high imaging quality, clear imaging throughout the zoom process, and no motion lag.

Description

Technical Field

[0001] This invention relates to the field of infrared optical systems, and more specifically to a high-resolution long-wave infrared continuous zoom optical system. Background Technology

[0002] In infrared systems, infrared detectors are crucial for detecting and identifying targets. Their main function is to convert incident infrared signals into detectable electrical signals for output. Uncooled infrared detectors, because they do not require cooling devices and can operate at room temperature, are widely used in the infrared field due to their low cost, small size, and low power consumption. Currently, with the development of infrared technology, the array size and resolution of uncooled infrared detectors are continuously increasing. Large-area, high-resolution detectors with a resolution of 1280×1024 pixels and a pixel pitch of 12μm have already achieved mature mass production.

[0003] Large-area infrared detectors require infrared optical lenses with correspondingly large target areas; otherwise, the system output image will appear washed out around the edges. Therefore, when designing an infrared optical system, the target area size of the optical system must be no smaller than the target area size of the selected infrared detector.

[0004] Furthermore, the optoelectronic systems used for target search and recognition require infrared thermal imaging systems to be capable of both wide-field-of-view target search and narrow-field-of-view recognition of distant targets. Therefore, single-field-of-view infrared optical systems cannot meet this requirement. The optical system of an infrared thermal imager needs to be designed as a zoom optical system to achieve this function. Continuous zoom infrared optical systems offer wide coverage with a wide field of view at short focal lengths and high resolution with a narrow field of view at long focal lengths. The wide field of view can be used for searching a large area of ​​targets, while the narrow field of view can be used for target recognition; the target image remains clear throughout the zoom process, allowing for any field of view transition within the zoom range, without losing track of the target during continuous zooming, and the ability to select an appropriate working field of view based on scene and target characteristics, greatly improving human-machine interface efficiency.

[0005] Most existing ordinary long-wave infrared zoom lenses can only be used with uncooled infrared detectors with a resolution of 640×612, which cannot meet the needs of the current new long-wave detectors with a resolution of 1280×1024 and a pixel size of 12μm. Although some infrared zoom systems can be used with high-resolution detectors, they have problems such as small zoom ratio and short focal length, or long system length and large size, which make it difficult to meet airborne requirements.

[0006] Therefore, it is necessary to propose a high-resolution long-wave infrared continuous zoom optical system, which can be effectively applied to high-resolution uncooled infrared detectors with a resolution of 1280×1024. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a high-resolution long-wave infrared continuous zoom optical system.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A high-resolution long-wave infrared continuous zoom optical system comprises a first meniscus positive lens, a biconcave negative lens, a biconvex positive lens, a first meniscus negative lens, a second meniscus negative lens, and a second meniscus positive lens arranged coaxially from the object side to the image side. The surfaces of the first meniscus positive lens, the first meniscus negative lens, and the second meniscus positive lens are convex towards the object side with positive radii of curvature, while the surfaces of the second meniscus negative lens are convex towards the image side with negative radii of curvature. The biconcave negative lens is a zoom lens, and the system's focal length is changed by moving the biconcave negative lens along its axial direction. When the system changes from a wide-angle end to a telephoto end, the zoom lens moves towards the image side. The biconvex positive lens is a compensation lens, and when the system changes from a wide-angle end to a telephoto end, the compensation lens moves away from the image side.

[0010] Furthermore, the center-to-center distance between the first meniscus positive lens and the biconcave negative lens is 20–56.5 mm, the center-to-center distance between the biconcave negative lens and the biconvex positive lens is 7.0–86.8 mm, and the center-to-center distance between the biconvex positive lens and the first meniscus negative lens is 6.5–49.9 mm; during the transition from the wide-angle end to the telephoto end, the travel of the biconcave negative lens is 46.5 mm, and the travel of the biconvex positive lens is 43.4 mm.

[0011] Furthermore, by using an axially moving second meniscus lens, the system achieves image plane defocus compensation within a temperature range of -40℃ to +60℃, as well as system defocus compensation caused by changes in the distance of the observed object, thereby ensuring clear imaging of objects at different distances.

[0012] Furthermore, the first meniscus positive lens, the biconcave negative lens, the biconvex positive lens, and the first meniscus negative lens are all made of single-crystal germanium (Ge), the second meniscus negative lens is made of zinc sulfide (ZNS), and the second meniscus positive lens is made of zinc selenide (ZNSE).

[0013] Furthermore, the distance on the optical axis between the second meniscus negative lens and the second meniscus positive lens is T. 56 The distance on the optical axis between the second meniscus positive lens and the image plane is T. 67 The thickness of the second meniscus positive lens on the optical axis is CT6, satisfying the following condition: 7.5 ≤ (T 56 +T 67 ) / CT6≤9.5.

[0014] Furthermore, the first meniscus positive lens satisfies the following condition: 0.7≤f1 / f≤0.9, where f is the focal length of the optical system in its telephoto state and f1 is the effective focal length of the first meniscus positive lens;

[0015] The biconcave negative lens satisfies the following condition: -0.3≤f2 / f≤-0.2, where f is the focal length of the optical system in its telephoto state and f2 is the effective focal length of the biconcave negative lens;

[0016] The biconvex positive lens satisfies the following condition: 0.3≤f3 / f≤0.5, where f is the focal length of the optical system in its telephoto state and f3 is the effective focal length of the biconvex positive lens;

[0017] The first meniscus negative lens satisfies the following condition: -30≤f4 / f≤-25, where f is the focal length of the optical system in its telephoto state and f4 is the effective focal length of the first meniscus negative lens;

[0018] The second meniscus negative lens satisfies the following condition: -1.8≤f5 / f≤-1.5, where f is the focal length of the optical system in telephoto mode and f5 is the effective focal length of the second meniscus negative lens;

[0019] The second meniscus positive lens satisfies the following condition: 0.25≤f6 / f≤0.45, where f is the focal length of the optical system in telephoto mode and f6 is the effective focal length of the second meniscus positive lens.

[0020] Furthermore, the incident surfaces of the biconcave negative lens, the first meniscus negative lens, and the second meniscus negative lens are all aspherical.

[0021] The incident surface of the biconvex positive lens is a diffractive aspherical surface.

[0022] The technical parameters achieved by the optical system are: operating wavelength: 8μm~12μm; F # : 1.2; Focal length: 30mm~150mm; Total optical length from the front surface of the first meniscus positive lens to the image plane: 230mm; Field of view: 28.7°×23.2°~5.86°×4.69°; Adapted to a 1280×1024, 12μm long-wave infrared detector, 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.

[0023] Beneficial effects:

[0024] 1. The optical system of this invention achieves continuous zoom within the range of 30mm to 150mm by rationally allocating the optical power of each lens and optimizing the positions of aspherical and diffractive surfaces, while realizing a large target surface design. It can be adapted to new high-resolution long-wavelength detectors with a resolution of 1024×768 and a pixel spacing of 12μm and a resolution of 1280×1024 and a pixel spacing of 12μm.

[0025] 2. The zoom lens and compensation lens of the optical system of the present invention have a continuous and smooth motion trajectory curve during the zooming process, without any sudden inflection points, thereby ensuring clear imaging throughout the zooming process without any motion lag. Attached Figure Description

[0026] Figure 1 This is the optical path diagram of the optical system in the short focal length (30mm) state.

[0027] Figure 2 This is the optical path diagram of the optical system at a focal length of 75mm.

[0028] Figure 3 This is the optical path diagram of the optical system at a focal length of 150mm.

[0029] Figure 4 This is a schematic diagram of the zoom motion trajectory of the optical system;

[0030] Figure 5 Transfer function graph of the optical system at a short focal length of 30mm;

[0031] Figure 6 Transfer function diagram of the optical system at a focal length of 75mm;

[0032] Figure 7 Transfer function graph of the optical system at a telephoto focal length of 150mm;

[0033] Figure 8 Dot plot of the optical system at a short focal length of 30mm;

[0034] Figure 9 Dot diagram of the optical system at 75mm mid-focus;

[0035] Figure 10 A dot plot of the optical system at a telephoto focal length of 150mm;

[0036] Figure 11 Zoom curve of the optical system.

[0037] Wherein, 1 is the first meniscus positive lens, 2 is the biconcave negative lens, 2 is the biconvex positive lens, 4 is the first meniscus negative lens, 5 is the second meniscus negative lens, 6 is the second meniscus positive lens, and 7 is the image plane. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings. In the description of the present 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 present invention and do not indicate or imply that the device or element referred to must have a specific orientation.

[0039] 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.

[0040] like Figures 1-4 The high-resolution long-wave infrared continuous zoom optical system shown consists of a first meniscus positive lens 1, a biconcave negative lens 2, a biconvex positive lens 3, a first meniscus negative lens 4, a second meniscus negative lens 5, and a second meniscus positive lens 6 arranged sequentially from the object side to the image side.

[0041] 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.

[0042] Furthermore, the first meniscus positive lens 1, the biconcave negative lens 2, the biconvex positive lens 3, the first meniscus negative lens 4, the second meniscus negative lens 5, and the second meniscus positive lens 6 are arranged coaxially from the object side to the image side.

[0043] Furthermore, the first meniscus positive lens 1, the first meniscus negative lens 4, and the second meniscus positive lens 6 are all bent towards the image side (in this application, bending towards the image side specifically means that the convex surface of each lens faces the object side, and the radius of curvature is positive), and the second meniscus negative lens 5 is bent towards the object side (meaning that the convex surface of each lens faces the image side, and the radius of curvature is negative).

[0044] Furthermore, the biconcave negative lens 2 is a zoom lens. The focal length of the system is changed by moving the biconcave negative lens 2 along the axis. When the system changes from the wide-angle end (short focal length) to the telephoto end (long focal length), the zoom lens moves towards the image side. The biconvex positive lens 3 is a compensation lens. When the system changes from the wide-angle end to the telephoto end, the compensation lens moves away from the image side (towards the object side).

[0045] Furthermore, the center-to-center distance between the first meniscus positive lens 1 and the biconcave negative lens 2 is 20–56.5 mm, the center-to-center distance between the biconcave negative lens 2 and the biconvex positive lens 3 is 7.0–86.8 mm, and the center-to-center distance between the biconvex positive lens 3 and the first meniscus negative lens 4 is 6.5–49.9 mm. During the transition from the wide-angle end to the telephoto end, the travel of the biconcave negative lens 2 is 46.5 mm, and the travel of the biconvex positive lens 3 is 43.4 mm.

[0046] The high-resolution long-wave infrared continuous zoom optical system uses an axially moving second meniscus lens 6 to achieve image plane defocus compensation within a temperature range of -40℃ to +60℃, as well as system defocus compensation caused by changes in the distance of the observed object, thereby ensuring clear imaging of objects at different distances.

[0047] Preferably, the first meniscus positive lens 1, the biconcave negative lens 2, the biconvex positive lens 3, and the first meniscus negative lens 4 are all made of single-crystal germanium (Ge), the second meniscus negative lens 5 is made of zinc sulfide (ZNS), and the second meniscus positive lens 6 is made of zinc selenide (ZNSE).

[0048] Furthermore, the specific light transmission path is as follows: the light emitted by the infrared radiation from the external scene is converged by the first meniscus positive lens 1 and reaches the biconcave negative lens 2; after being diverged by the biconcave negative lens 2, it reaches the biconvex positive lens 3; after being converged by the biconvex positive lens 3, it reaches the first meniscus negative lens 4; after being diverged by the first meniscus negative lens 4, it reaches the second meniscus negative lens 5; after being diverged by the second meniscus negative lens 5, it reaches the second meniscus positive lens 6; and after being converged by the second meniscus positive lens 6, it is imaged on the image plane 7.

[0049] The distance on the optical axis between the second meniscus negative lens 5 and the second meniscus positive lens 6 is T56, and the distance on the optical axis between the second meniscus positive lens 6 and the image plane 7 is T. 67 The thickness of the second meniscus positive lens 6 on the optical axis is CT6, satisfying the following condition: 7.5 ≤ (T 56 +T 67 ) / CT6≤9.5.

[0050] Preferably, the first meniscus positive lens 1 satisfies the following condition: 0.7≤f1 / f≤0.9, where f is the focal length of the optical system in telephoto mode and f1 is the effective focal length of the first meniscus positive lens 1;

[0051] The biconcave negative lens 2 satisfies the following condition: -0.3≤f2 / f≤-0.2, where f is the focal length of the optical system in its telephoto state and f2 is the effective focal length of the biconcave negative lens 2;

[0052] The biconvex positive lens 3 satisfies the following condition: 0.3≤f3 / f≤0.5, where f is the focal length of the optical system in its telephoto state and f3 is the effective focal length of the biconvex positive lens 3;

[0053] The first meniscus negative lens 4 satisfies the following condition: -30≤f4 / f≤-25, where f is the focal length of the optical system in its telephoto state and f4 is the effective focal length of the first meniscus negative lens 4;

[0054] The second meniscus negative lens 5 satisfies the following condition: -1.8 ≤ f5 / f ≤ -1.5, where f is the focal length of the optical system in telephoto mode and f5 is the effective focal length of the second meniscus negative lens 5.

[0055] The second meniscus positive lens 6 satisfies the following condition: 0.25≤f6 / f≤0.45, where f is the focal length of the optical system in its telephoto state and f6 is the effective focal length of the second meniscus positive lens 6;

[0056] Table 1 shows the technical specifications achieved by this invention. In the table, F# (F-number of the optical system) is calculated as f / D, where f is the focal length of the optical system and D is the diameter of the entrance pupil.

[0057] Table 1 Technical Specifications of the Optical System of the Invention

[0058] parameter Technical indicators detector 1280×1024 long-wave infrared detector Pixel size 12μm Operating band 8μm~12μm <![CDATA[F # (F-number of the optical system) 1.2 focal length 30mm~150mm Field of view 28.7°×23.2°～5.86°×4.69° Image plane diameter Φ20mm

[0059] Table 2 lists detailed data for embodiments of the optical system according to the present invention with focal lengths of 30mm to 150mm, 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, and the radius of curvature for spherical and aspherical surfaces refers to the radius of curvature at the intersection of the lens surface and the optical axis.

[0060] In Table 2, the "Surface Number" is counted along the direction of light propagation. For example, the incident surface of the first meniscus positive lens 1 is numbered S1, and the exit surface is numbered S2. The other surface numbers follow the same pattern. The curved surfaces of the first meniscus positive lens 1, the biconcave negative lens 2, the biconvex positive lens 3, the first meniscus negative lens 4, the second meniscus negative lens 5, and the second meniscus positive lens 6 along the object-to-image direction are respectively labeled S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, and S12. The "Radius" in Table 2 represents the radius of curvature of the surface. Its sign is determined by taking the intersection of the surface and the principal optical axis as the starting point and the center of the surface as the ending point. If the direction of the line connecting them 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 indicates the distance between two adjacent surfaces along 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 line connecting the two surfaces 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.

[0061] Table 2 Detailed data of the optical system in the embodiments of the present invention

[0062]

[0063]

[0064] In the aforementioned high-resolution long-wave infrared continuous zoom optical system, the incident surface S3 of the biconcave negative lens 2, the incident surface S7 of the first meniscus negative lens 4, and the incident surface S9 of the second meniscus negative lens 5 are all aspherical.

[0065] Furthermore, the surface equations of the above-mentioned aspherical surfaces are as follows:

[0066]

[0067] 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.

[0068] Table 3 lists the aspherical coefficients of the incident surface S3 of the biconcave negative lens 2, the incident surface S7 of the first meniscus negative lens 4, and the incident surface S9 of the second meniscus negative lens 5 according to the present invention. The table uses scientific notation; for example, -5.428036e-007 represents -5.428036 × 10⁻⁶. -7 .

[0069] Table 3 Aspheric coefficients of the present invention

[0070]

[0071] Furthermore, the incident surface S5 of the biconvex positive lens 3 is aspherical. A continuous relief structure is machined on the aspherical substrate using diamond turning to form a diffraction surface, which satisfies the following equation:

[0072]

[0073] 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 diffraction surface coefficients, λ0 is the design center wavelength, n is the refractive index of the lens, and n0 is the refractive index of air. Table 4 lists the diffraction aspherical coefficients of the incident surface of the biconvex positive lens 3 according to the present invention.

[0074] Table 4. Diffraction non-surface coefficients of the biconvex positive lens of the present invention.

[0075]

[0076] After simulation using optical design software, such as Figure 5 , Figure 6 , Figure 7 As shown, the transfer function of the optical system of the present invention is greater than 0.2 in the long focal length, medium focal length, and short focal length states; as Figure 8 , Figure 9 , Figure 10 As shown, the dot plots of the optical system of the present invention in long focal length, medium focal length, and short focal length states are illustrated. The diameter of the blur spot in this system is comparable to the pixel size of the detector. Figure 11 The figure shows the zoom curve of this continuous zoom optical system. The horizontal axis represents the focal length of the continuous zoom optical system, and the vertical axis represents the axial distance between the zoom group and the compensation group relative to the front fixed group. As can be seen from the figure, the zoom curve of this system is smooth and continuous, without any abrupt changes, which can effectively avoid the system from jamming during zooming.

[0077] 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 high-resolution long-wave infrared continuous zoom optical system, characterized in that, The optical system comprises a first meniscus positive lens, a biconcave negative lens, a biconvex positive lens, a first meniscus negative lens, a second meniscus negative lens, and a second meniscus positive lens, arranged coaxially from the object side to the image side. The convex surfaces of the first meniscus positive lens, the first meniscus negative lens, and the second meniscus positive lens are all convex towards the object side, and each surface has a positive radius of curvature. The convex surface of the second meniscus negative lens is all convex towards the image side, and each surface has a negative radius of curvature. The biconcave negative lens is a zoom lens, and the focal length of the system is changed by moving the biconcave negative lens along the axial direction. When the system changes from the wide-angle end to the telephoto end, the zoom lens moves towards the image side. The biconvex positive lens is a compensation lens, and when the system changes from the wide-angle end to the telephoto end, the compensation lens moves away from the image side.

2. The high-resolution long-wave infrared continuous zoom optical system according to claim 1, characterized in that, The center-to-center distance between the first meniscus positive lens and the biconcave negative lens is 20–56.5 mm, the center-to-center distance between the biconcave negative lens and the biconvex positive lens is 7.0–86.8 mm, and the center-to-center distance between the biconvex positive lens and the first meniscus negative lens is 6.5–49.9 mm. During the transition from the wide-angle end to the telephoto end, the travel distance of the biconcave negative lens is 36.5 mm, and the travel distance of the biconvex positive lens is 43.4 mm.

3. The high-resolution long-wave infrared continuous zoom optical system according to claim 1, characterized in that, The system employs an axially moving second meniscus lens to achieve image plane defocus compensation within a temperature range of -40℃ to +60℃, as well as system defocus compensation caused by changes in the distance of the observed object, thereby ensuring clear imaging of objects at different distances.

4. The high-resolution long-wave infrared continuous zoom optical system according to claim 1, characterized in that, The first meniscus positive lens, the biconcave negative lens, the biconvex positive lens, and the first meniscus negative lens are all made of single-crystal germanium (Ge), the second meniscus negative lens is made of zinc sulfide (ZNS), and the second meniscus positive lens is made of zinc selenide (ZNSE).

5. The high-resolution long-wave infrared continuous zoom optical system according to claim 1, characterized in that, The distance on the optical axis between the second meniscus negative lens and the second meniscus positive lens is T. 56 The distance on the optical axis between the second meniscus positive lens and the imaging plane is T. 67 The thickness of the second meniscus positive lens on the optical axis is CT6, satisfying the following condition: 7.5 ≤ (T 56 +T 67 ) / CT6≤9.

5.

6. A high-resolution long-wave infrared continuous zoom optical system according to claim 1, characterized in that... The focal lengths of the lenses mentioned above must meet the following conditions: 0.7≤f1 / f≤0.9, -0.3≤f2 / f≤-0.2, 0.3≤f3 / f≤0.5, -30≤f4 / f≤-25, -1.8≤f5 / f≤-1.5, 0.25≤f6 / f≤0.45; Where: f is the focal length of the optical system in telephoto mode. f1 is the effective focal length of the first meniscus positive lens. f2 is the effective focal length of the biconcave negative lens. f3 is the effective focal length of the biconvex positive lens. f4 is the effective focal length of the first meniscus negative lens. f5 is the effective focal length of the second meniscus negative lens. f6 is the effective focal length of the second meniscus positive lens.

7. A high-resolution long-wave infrared continuous zoom optical system according to claim 1, characterized in that, The incident surfaces of the biconcave negative lens, the first meniscus negative lens, and the second meniscus negative lens are all aspherical.

8. A high-resolution long-wave infrared continuous zoom optical system according to claim 1, characterized in that, The incident surface of the biconvex positive lens is a diffractive aspherical surface.

9. A high-resolution long-wave infrared continuous zoom optical system according to claim 1, characterized in that, The technical parameters achieved by the optical system are: operating wavelength: 8μm~12μm; F # : 1.2; Focal length: 30mm~150mm; Total optical length from the front surface of the first meniscus positive lens to the image plane: 230mm; Field of view: 28.7°×23.2°~5.86°×4.69°; Adapted to a 1280×1024, 12μm long-wave infrared detector, 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.

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