Infrared continuous zoom lens

Abstract

The disclosure provides an infrared continuous zoom lens, and relates to the field of optical elements. The infrared continuous zoom lens comprises, in sequence from the object side to the image side along the optical axis, a front fixed group, a zoom group, a compensation group, a rear fixed group and a non-cooled long-wave infrared detector; the front fixed group comprises a first lens with positive refractive power; the zoom group comprises a second lens with negative refractive power and a third lens with negative refractive power; the compensation group comprises a fourth lens with positive refractive power; the rear fixed group comprises a fifth lens with negative refractive power and a sixth lens with positive refractive power; the positions of the zoom group and the compensation group in the direction of the optical axis are adjustable. The infrared continuous zoom lens has an optical structure for realizing continuous zoom, can realize a high zoom ratio, has high imaging quality, and has a smooth zoom cam curve.

Description

Technical Field

[0001] This disclosure relates to the field of optical components, and more particularly to an infrared continuous zoom lens. Background Technology

[0002] Infrared continuous zoom lenses are commonly used for target search and identification, and are increasingly important in fields such as road monitoring, forest fire prevention, straw burning, and airport surveillance.

[0003] The related technology uses a five-element infrared continuous zoom lens, which includes aspherical lenses and binary diffractive lenses. However, due to limitations in infrared materials and design methods, the resolution of this technology is relatively low, mostly around 640×512. It is difficult to achieve a high optical transfer function at higher cutoff frequencies, and it is easy to lose detailed information about objects when detecting them. Summary of the Invention

[0004] This disclosure provides an infrared continuous zoom lens to at least solve the above-mentioned technical problems existing in the prior art.

[0005] According to a first aspect of this disclosure, an infrared continuous zoom lens is provided, comprising, sequentially along the optical axis from the object side to the image side, a front fixed group, a zoom group, a compensation group, a rear fixed group, and an uncooled long-wave infrared detector; wherein...

[0006] The front fixation group includes a first lens with positive optical power;

[0007] The zoom group includes a second lens with negative optical power and a third lens with negative optical power;

[0008] The compensation group includes a fourth lens with positive optical power;

[0009] The rear fixed assembly includes a fifth lens with negative optical power and a sixth lens with positive optical power.

[0010] In one embodiment, the focal length f1 of the front fixed group is 146.8 to 157.4 mm; the focal length f2 of the zoom group is -28.1 to -32.9 mm; the focal length f3 of the compensation group is 31.9 to 49.3 mm; and the focal length f4 of the rear fixed group is 42.3 to 54.8 mm.

[0011] In one embodiment, the focal length f1 of the front fixed group is 156.8 mm; the focal length f2 of the zoom group is -31.9 mm; the focal length f3 of the compensation group is 49.3 mm; and the focal length f4 of the rear fixed group is 43.8 mm.

[0012] In one possible embodiment, the first lens is a meniscus lens with its convex surface facing the object side;

[0013] The first lens is a meniscus positive lens with positive optical power and a convex surface facing the object side;

[0014] The second lens is a meniscus negative lens with negative optical power;

[0015] The third lens is a negative diconcave lens;

[0016] The fourth lens is a biconvex positive lens with positive optical power;

[0017] The fifth lens is a meniscus negative lens with a negative optical power and a convex surface facing the image side;

[0018] The sixth lens is a meniscus negative lens with a negative optical power and a convex surface facing the object side. In one possible embodiment, the optical surfaces of the third lens facing the object side, the fourth lens facing the object side, the fifth lens facing the object side, and the sixth lens facing the image side are high-order aspherical surfaces, which satisfy the following conditions:

[0019]

[0020] Where z represents the position of the even-order aspherical surface along the optical axis at a height of r, from the vertex of the aspherical surface; c represents the curvature of the vertex; k represents the conic coefficients; and a4, a6, a8, a... 10 This represents the higher-order aspheric coefficients.

[0021] In one possible embodiment, the optical surface of the fifth lens facing the object side is a binary diffractive aspherical surface, which satisfies the following:

[0022]

[0023] Where z represents the position of the even-order aspherical surface along the optical axis at a height of r, from the vertex of the aspherical surface; c represents the curvature of the vertex; k represents the conic coefficients; and a4, a6, a8, a... 10 a 12 The higher-order aspherical coefficients are represented; 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 fifth lens; and n0 is the air refractive index.

[0024] In one embodiment, the material of the second lens is zinc sulfide; and the materials of the first lens, third lens, fourth lens, fifth lens and sixth lens are germanium.

[0025] In one embodiment, the sixth lens moves along the optical axis to compensate for the effect of temperature on imaging; when the focal length of the infrared continuous zoom lens remains constant, the axial displacement distance of the sixth lens is positively correlated with the temperature; when the ambient temperature is higher than a preset temperature, the axial displacement distance of the sixth lens is positively correlated with the focal length of the infrared continuous zoom lens; when the ambient temperature is lower than the preset temperature, the axial displacement distance of the sixth lens is negatively correlated with the focal length of the infrared continuous zoom lens.

[0026] In one embodiment, the zoom group moves along the optical axis, causing the focal length of the infrared continuous zoom lens to switch between short focal length, medium focal length, and long focal length.

[0027] In one embodiment, the infrared continuous zoom lens further includes a lens barrel made of aluminum alloy with a coefficient of thermal expansion of 23.6*10⁻⁶. -6 K.

[0028] According to a first aspect of this disclosure, an imaging apparatus is also provided, which is provided with an electronic photosensitive element for imaging, and the imaging apparatus is equipped with the infrared continuous zoom lens described above.

[0029] The infrared continuous zoom lens disclosed herein has an optical structure that enables continuous zoom, achieving a high zoom ratio, suitable for large target detectors, and exhibiting high imaging quality and a smooth zoom cam curve. The infrared continuous zoom lens is compact, lightweight, small in size, and has high imaging resolution.

[0030] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0031] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. Several embodiments of this disclosure are illustrated in the drawings by way of example and not limitation, in which:

[0032] In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0033] Figure 1 A schematic diagram of the structure of the infrared continuous zoom lens provided in this embodiment is shown. Figure 1 ;

[0034] Figure 2 A schematic diagram of the structure of the infrared continuous zoom lens provided in this embodiment is shown. Figure 2 ;

[0035] Figure 3 A schematic diagram of the structure of the infrared continuous zoom lens provided in this embodiment is shown. Figure 3 ;

[0036] Figure 4 A schematic diagram of the structure of the infrared continuous zoom lens provided in this embodiment is shown. Figure 4 ;

[0037] Figure 5 The transfer function diagram of an infrared continuous zoom lens in short focal length mode at room temperature, provided in an embodiment of this disclosure, is shown.

[0038] Figure 6 A dot diagram is shown of an infrared continuous zoom lens in a short focal length state at room temperature, according to an embodiment of the present disclosure.

[0039] Figure 7 The transfer function diagram of an infrared continuous zoom lens in mid-range mode at room temperature, provided in an embodiment of this disclosure, is shown.

[0040] Figure 8 A dot plot of an infrared continuous zoom lens in mid-range mode at room temperature, provided in an embodiment of this disclosure, is shown.

[0041] Figure 9 The transfer function diagram of an infrared continuous zoom lens in telephoto mode at room temperature provided in an embodiment of this disclosure is shown.

[0042] Figure 10 A dot diagram is shown of an infrared continuous zoom lens in telephoto mode at room temperature, according to an embodiment of the present disclosure.

[0043] Figure 11 A zoom cam curve diagram of an infrared continuous zoom lens provided in an embodiment of this disclosure is shown. Detailed Implementation

[0044] To make the objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0045] Figure 1 This illustration shows a structural diagram of an infrared continuous zoom lens provided in an embodiment of the present disclosure. Figure 1 The infrared continuous zoom lens comprises, along the optical axis from the object side to the image side, the following components in sequence: front fixed group G1, zoom group G2, compensation group G3, rear fixed group G4, and uncooled long-wave infrared detector G5.

[0046] The front fixed assembly G1 includes a first lens L1 with positive optical power. The first lens L1 is a meniscus positive lens with its convex surface facing the object side, and both surfaces are spherical. The material of the first lens L1 is germanium. In one possible embodiment, the concave aperture of the first lens L1 is determined by the maximum focal length of the infrared continuous zoom lens and the system F-number. In this disclosure, the optical surface of the first lens L1 facing the object side is denoted as S11, and the optical surface facing the image side is denoted as S12. In one possible embodiment, the focal length f1 of the front fixed assembly G1 is 146.8–157.4 mm.

[0047] The zoom group G2 includes a second lens L2 with negative optical power and a third lens L3 with negative optical power. The second lens L2 is a meniscus negative lens, and its material is zinc sulfide. In this disclosure, the optical surface of the second lens L2 facing the object side is designated S21, and the optical surface facing the image side is designated S22. The third lens L3 is a biconcave positive lens, and its material is germanium. The zoom group G2 is movable along the optical axis to change the focal length of the infrared continuous zoom lens. In this disclosure, the optical surface of the third lens L3 facing the object side is designated S31, and the optical surface facing the image side is designated S32. The position of the zoom group G2 in the optical axis direction is adjustable. In one embodiment, the focal length f2 of the zoom group G2 is -28.1 to -32.9 mm.

[0048] The compensation group G3 includes a fourth lens L4 with positive optical power. The fourth lens L4 is a biconvex positive lens made of germanium. In one embodiment, the fourth lens L4 is movable along the optical axis to compensate for changes in the image plane position caused by the movement of the fixed group G1, thereby making the image on the uncooled long-wave infrared detector G5 clearer. In this disclosure, the optical surface of the fourth lens L4 facing the object side is designated S41, and the optical surface facing the image side is designated S42. The position of the compensation group G2 in the optical axis direction is adjustable. In one embodiment, the focal length f3 of the compensation group G3 is 31.9–49.3 mm.

[0049] The rear fixed assembly G4 includes a fifth lens L5 with negative optical power and a sixth lens L6 with positive optical power. The fifth lens L5 is a meniscus negative lens with its convex surface facing the image side, and both surfaces are spherical. The material of the fifth lens L5 is germanium. The fifth lens L5 is used to compensate for chromatic aberration in an infrared continuous zoom lens. In this disclosure, the optical surface of the fifth lens L5 facing the object side is designated S51, and the optical surface facing the image side is designated S52. The sixth lens L6 is a meniscus negative lens with its convex surface facing the object side, and the surface facing the image side is spherical. The material of the sixth lens L6 is germanium. The sixth lens L6 is used for temperature compensation. In this disclosure, the optical surface of the sixth lens L6 facing the object side is designated S61, and the optical surface facing the image side is designated S62. In one possible embodiment, the focal length f4 of the rear fixed assembly G4 is 42.3–54.8 mm.

[0050] In one embodiment, the infrared continuous zoom lens further includes a lens barrel made of aluminum alloy with a coefficient of thermal expansion of 23.6*10. -6 K.

[0051] In one embodiment, the sixth lens L6 moves along the optical axis to compensate for the effect of temperature on imaging. When the focal length of the infrared continuous zoom lens remains unchanged, the axial displacement distance of the sixth lens L6 is positively correlated with the temperature. When the ambient temperature is higher than a preset temperature, the axial displacement distance of the sixth lens L6 is positively correlated with the focal length of the infrared continuous zoom lens. When the ambient temperature is lower than the preset temperature, the axial displacement distance of the sixth lens L6 is negatively correlated with the focal length of the infrared continuous zoom lens.

[0052] In one embodiment, the zoom group G2 moves along the optical axis, causing the focal length of the infrared continuous zoom lens to switch between short focal length, medium focal length, and long focal length. Figure 2 A schematic diagram of the short focal length structure of an infrared continuous zoom lens is shown. Figure 3 A schematic diagram of the mid-focus structure of an infrared continuous zoom lens is shown. Figure 4 A schematic diagram of the telephoto structure of an infrared continuous zoom lens is shown.

[0053] In one embodiment, the focal length f1 of the front fixed group G1 and the focal length f2 of the zoom group G2 satisfy: 4.4 < |f1 / f2| < 5. In one embodiment, the focal length f2 of the zoom group G2 and the focal length f3 of the compensation group G3 satisfy: 1.3 < |f3 / f2| < 1.8. In one embodiment, the focal length f2 of the zoom group G2 and the focal length f4 of the rear fixed group G4 satisfy: 1.5 < |f4 / f2| < 2.1.

[0054] In one embodiment, the focal length f1 of the front fixed group G1 is 156.8 mm; the focal length f2 of the zoom group G2 is -31.9 mm; the focal length f3 of the compensation group G3 is 49.3 mm; and the focal length f4 of the rear fixed group G4 is 43.8 mm.

[0055] In one possible implementation, Table 1 records the parameters of each optical element in this embodiment:

[0056] Table 1 Optical Component Parameters

[0057]

[0058]

[0059] Where ti represents the thickness of the i-th optical element. di represents the air gap between the i-th optical element and the next optical element. d1, d3, and d4 are variable gaps. d1 is the air gap between the zoom group G2 and the front fixed group G1. d3 is the variable gap between the zoom group G2 and the compensation group G3. d4 is the variable gap between the compensation group G3 and the rear fixed group G4.

[0060] In one possible embodiment, the optical surfaces of the third lens L3 facing the object side, the fourth lens L4 facing the object side, the fifth lens L5 facing the object side, and the sixth lens L6 facing the image side are higher-order aspherical surfaces. These higher-order aspherical surfaces satisfy the following:

[0061]

[0062] Where z represents the position of the even-order aspherical surface along the optical axis at a height of r, from the vertex of the aspherical surface; c represents the curvature of the vertex; k represents the conic coefficients; and a4, a6, a8, a... 10 This represents the higher-order aspheric coefficients.

[0063] In one embodiment, the aspherical coefficients of optical surfaces S31, S41, S51, and S51 are shown in Table 2, wherein optical surface S51 is a binary diffraction aspherical surface. Table 2 is as follows:

[0064] Table 2 Aspherical Coefficients

[0065]

[0066]

[0067] In one possible implementation, the optical surface S51 is a diffraction surface that satisfies:

[0068]

[0069] Where z represents the position of the even-order aspherical surface along the optical axis at a height of r, from the vertex of the aspherical surface; c represents the curvature of the vertex; k represents the conic coefficients; and a4, a6, a8, a... 10 a 12 The higher-order aspherical coefficients are represented; HOR is the diffraction order; C1, C2, and C3 are the diffraction surface coefficients; λ0 is the design center wavelength; n is the refractive index of the fifth lens; and n0 is the air refractive index.

[0070] In one possible implementation, the diffraction coefficients of the optical surface S51 are shown in Table 3:

[0071] Table 3 Diffraction coefficients of optical surface S51

[0072] S51 10μm <![CDATA[-1.73·10 -05 ]]> <![CDATA[-4.20·10 -08 ]]> <![CDATA[4.75·10 -11 ]]>

[0073] In one embodiment, the infrared continuous zoom lens has a working wavelength of 8-12 micrometers, a focal length of 25-225 millimeters, a zoom ratio of 9x, an optical F-number of 1.5, and a total optical length of 271.05 millimeters.

[0074] In one embodiment, the focal length f1 of the front fixed group G1 is 156.8 mm; the focal length f2 of the zoom group G2 is -31.9 mm; the focal length f3 of the compensation group G3 is 49.3 mm; and the focal length f4 of the rear fixed group G4 is 43.8 mm.

[0075] For example, Table 4 records the values ​​of the variable intervals d1, d3, and d4 of the infrared continuous zoom lens of this disclosure at different focal length positions.

[0076] Table 4 Relationship between focal length position and variable spacing

[0077]

[0078]

[0079] In one embodiment, the infrared continuous zoom lens of this disclosure exhibits an average MTF > 0.15 (Modulation Transfer Function) across the entire focal length and field of view in scenarios below -40°C, and an average MTF > 0.22 at the mid-frequency (33 lp / mm). In scenarios below 20°C, the average MTF > 0.2 at the high-frequency (42 lp / mm) and average MTF > 0.25 at the mid-frequency (33 lp / mm). In scenarios below 60°C, the average MTF > 0.2 at the high-frequency (42 lp / mm) and average MTF > 0.23 at the mid-frequency (33 lp / mm). Therefore, the infrared continuous zoom lens provided in this embodiment demonstrates excellent MTF performance in scenarios ranging from -40°C to 60°C, enabling it to adapt to different environments and broadening its application scenarios.

[0080] In one possible implementation, Figure 5 The diagram shows the transfer function of an infrared continuous zoom lens in a short focal length state at room temperature, as provided in an embodiment of this disclosure. Figure 6 A dot plot of an infrared continuous zoom lens in a short focal length state at room temperature, as provided in an embodiment of this disclosure, is shown. From Figure 5 and Figure 6 As can be seen, under normal temperature conditions, the transfer function of the infrared continuous zoom lens in its short focal length state is close to the diffraction limit, resulting in good imaging. In one possible implementation, Figure 7 The diagram shows the transfer function of an infrared continuous zoom lens in mid-range mode at room temperature, as provided in an embodiment of this disclosure. Figure 8 A dot plot of an infrared continuous zoom lens in mid-range mode at room temperature, as provided in an embodiment of this disclosure, is shown. From Figure 7 and Figure 8 As can be seen, under normal temperature conditions, the transfer function of the mid-focus state of the infrared continuous zoom lens is close to the diffraction limit, resulting in good imaging. In one possible implementation, Figure 9 A transfer function graph of an infrared continuous zoom lens in telephoto mode at room temperature, provided in an embodiment of this disclosure, is shown. A dot plot of an infrared continuous zoom lens in telephoto mode at room temperature, provided in an embodiment of this disclosure, is also shown. From... Figure 9 and Figure 10 As can be seen, under normal temperature conditions, the transfer function of the infrared continuous zoom lens in the telephoto state is close to the diffraction limit, resulting in good imaging. Therefore, the infrared continuous zoom lens provided in this embodiment has a transfer function close to the diffraction limit in the short, medium, and long focal length states, resulting in good imaging and realizing the design of a high zoom ratio and high resolution infrared continuous zoom lens.

[0081] In one possible implementation, Figure 11 A zoom cam curve diagram of an infrared continuous zoom lens provided in an embodiment of this disclosure is shown. From... Figure 11 The zoom cam curve of the infrared continuous zoom lens disclosed herein is smooth, which facilitates the switching of different focal lengths during zooming and is beneficial for machining.

[0082] In one embodiment, this disclosure also provides an imaging device equipped with an electronic photosensitive element for imaging, the imaging device being fitted with the infrared continuous zoom lens described above.

[0083] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this disclosure can be achieved, and this is not limited herein.

[0084] 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 disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0085] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. An infrared continuous zoom lens, characterized in that, Along the optical axis from the object side to the image side, it includes, in sequence, a front fixed group, a zoom group, a compensation group, a rear fixed group, and an uncooled long-wave infrared detector; among them... The front fixation group includes a first lens with positive optical power; The zoom group includes a second lens with negative optical power and a third lens with negative optical power; the second lens is a meniscus negative lens made of zinc sulfide; the third lens is a biconcave negative lens made of germanium. The compensation group includes a biconvex fourth lens with positive optical power, made of germanium; The rear fixation assembly includes a fifth lens with negative optical power and a convex surface facing the image side, and a sixth lens with positive optical power and a convex surface facing the object side. The positions of the zoom group and the compensation group are adjustable along the optical axis; the focal length f1 of the front fixed group and the focal length f2 of the zoom group satisfy 4.4 < |f1 / f2| < 5.

2. The infrared continuous zoom lens according to claim 1, characterized in that, The focal length f2 of the zoom group, the focal length f3 of the compensation group, and the focal length f4 of the rear fixed group respectively satisfy: 1.3 < |f3 / f2| < 1.8; 1.5 < |f4 / f2| < 2.

1.

3. The infrared continuous zoom lens according to claim 1, characterized in that, The focal length f1 of the front fixed group is 146.8~157.4 mm; the focal length f2 of the zoom group is -28.1~-32.9 mm; the focal length f3 of the compensation group is 31.9~49.3 mm; and the focal length f4 of the rear fixed group is 42.3~54.8 mm.

4. The infrared continuous zoom lens according to claim 1, characterized in that, The optical surfaces of the third lens facing the object side, the fourth lens facing the object side, the fifth lens facing the object side, and the sixth lens facing the image side are high-order aspherical surfaces, which satisfy the following conditions: ； Where z represents the position of the even-order aspherical surface along the optical axis at a height of r, from the vertex of the aspherical surface; c represents the curvature of the vertex; and k represents the conic coefficient. , , , This represents the higher-order aspheric coefficients.

5. The infrared continuous zoom lens according to claim 1, characterized in that, The optical surface of the fifth lens facing the object side is a binary diffractive aspherical surface, which satisfies the following: ； Where z represents the position of the even-order aspherical surface along the optical axis at a height of r, from the vertex of the aspherical surface; c represents the curvature of the vertex; and k represents the conic coefficient. , , , , Represents the higher-order aspherical coefficients; HOR represents the diffraction order; , , The diffraction surface coefficient; The design center wavelength is given by n; n is the refractive index of the fifth lens. The refractive index of air.

6. The infrared continuous zoom lens according to any one of claims 1 to 3, characterized in that, The first lens, the fifth lens, and the sixth lens are made of germanium.

7. The infrared continuous zoom lens according to any one of claims 1 to 3, characterized in that, The sixth lens moves along the optical axis to compensate for the effect of temperature on imaging. When the focal length of the infrared continuous zoom lens remains constant, the axial displacement distance of the sixth lens is positively correlated with the temperature. When the ambient temperature is higher than the preset temperature, the axial displacement distance of the sixth lens is positively correlated with the focal length of the infrared continuous zoom lens. When the ambient temperature is lower than the preset temperature, the axial displacement distance of the sixth lens is negatively correlated with the focal length of the infrared continuous zoom lens.

8. The infrared continuous zoom lens according to any one of claims 1 to 3, characterized in that, The zoom group moves along the optical axis, causing the focal length of the infrared continuous zoom lens to switch between short focal length, medium focal length, and long focal length.

9. The infrared continuous zoom lens according to any one of claims 1 to 3, characterized in that, The infrared continuous zoom lens also includes a lens barrel made of aluminum alloy with a coefficient of thermal expansion of 23.

6. 10 -6 K.

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