Long-wave continuous zooming infrared lens and lens module

Abstract

The invention belongs to the technical field of infrared optics, and discloses a long-wave continuous zooming infrared lens and a lens module. The lens comprises a first lens, a movable lens group and a fifth lens which are sequentially arranged on the same optical axis from an object side to an image side. The first lens is a meniscus lens of which the convex surface faces the object side, and the fifth lens is a meniscus lens of which the convex surface faces the object side; the relative positions of the first lens and the fifth lens are fixed; the movable lens group comprises a second lens, a third lens and a fourth lens which are arranged in sequence; the second lens is a biconcave lens, the third lens is a biconvex lens, and the fourth lens is a meniscus lens of which the convex surface faces the image side; and the second lens, the third lens and the fourth lens can move along the optical axis to realize continuous zooming. The system is short in length, small in number of lenses, high in light transmittance, good in imaging quality and capable of being matched with a detector with the number of pixels being 1280 * 1024 and the size of the pixels being 12 micrometers.

Description

Technical Field

[0001] The present technology belongs to the field of infrared optical technology, and in particular relates to a long-wave continuous zoom infrared lens and a lens module. Background Art

[0002] Compared with the fixed-focus system, the zoom system has the advantages of being able to identify and track targets in a small field of view and being able to search for targets over a large range in a large field of view. It has been increasingly widely used in search, navigation, detection, and tracking.

[0003] As the application of infrared continuous zoom systems becomes more and more extensive, higher requirements are also placed on the lenses that match them. For example, the long-wave infrared lenses on the existing market are mainly suitable for 320×256 pixel or 640×512 pixel arrays, which have the disadvantages of small field of view and low imaging resolution. The new long-wave infrared array detector has a pixel of 1280×1024, which is smaller and has a higher resolution, and needs to be matched with a continuous zoom lens with higher imaging quality. Although there are high-resolution continuous zoom lenses in the prior art, they often have disadvantages such as small focal range, low light transmittance, complex structure, and too long total system length. Summary of the invention

[0004] In order to solve the above problems, one object of the present invention is to provide a long-wave continuous zoom infrared lens. The specific technical solution is as follows: A long-wave continuous zoom infrared lens, the lens comprising a first lens, a movable lens group and a fifth lens which are arranged in sequence on the same optical axis from the object side to the image side; The first lens is a meniscus lens with a convex surface facing the object, and has positive optical power; the fifth lens is a meniscus lens with a convex surface facing the object, and has positive optical power; the relative positions of the first lens and the fifth lens are fixed; The movable lens group includes a second lens, a third lens, and a fourth lens arranged in sequence; the second lens is a double concave lens; the third lens is a double convex lens; the fourth lens is a meniscus lens with the convex surface facing the image side and has negative optical power; the second lens, the third lens, and the fourth lens can move along the optical axis to achieve continuous zoom.

[0005] Furthermore, when the lens changes from long focus to short focus, the second lens moves toward the object side; when the lens changes from short focus to long focus, the second lens moves toward the image side; When the lens is in the longest focal length state, the variable interval between the first lens and the second lens is in the maximum state, the variable interval between the second lens and the third lens is in the minimum state, the variable interval between the third lens and the fourth lens is in the maximum state, and the variable interval between the fourth lens and the fifth lens is in the minimum state; When the lens is in the shortest focal length state, the variable interval between the first lens and the second lens is in the minimum state, the variable interval between the second lens and the third lens is in the maximum state, and the variable interval between the third lens and the fourth lens is in the minimum state.

[0006] Furthermore, the first lens, the second lens, the third lens, the fourth lens and the fifth lens are all made of germanium.

[0007] Furthermore, the object side surface of the second lens, the image side surface of the second lens, the object side surface of the third lens, the image side surface of the third lens, the image side surface of the fourth lens, and the image side surface of the fifth lens are aspherical surfaces and satisfy the aspherical surface formula: Among them, Z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height r along the optical axis; c=1 / R; R is the paraxial curvature fitting radius of the mirror; k is the cone coefficient; A, B, C, D, and E are high-order aspherical coefficients.

[0008] Furthermore, the object side surface of the third lens is a binary surface, which satisfies the aspheric surface formula and satisfies the expression equation of the binary surface in Zemax: M(B1ρ 2 +B2ρ 4 +B3ρ 6 ), where M is the diffraction order, B1, B2, B3 are the binary surface phase coefficients, and ρ is the normalized radius.

[0009] Furthermore, a stop is provided on the object side of the third lens.

[0010] Furthermore, the operating band of the lens is 8 μm to 12 μm, and the focal length is 25 to 225 mm.

[0011] Furthermore, the variable interval between the first lens and the second lens is 122.913-51.228 mm, the variable interval between the second lens and the third lens is 8.934-126.355 mm, the variable interval between the third lens and the fourth lens is 74.649-10.967 mm, and the variable interval between the fourth lens and the fifth lens is 38.117-57.066 mm.

[0012] Further, the center thickness of the first lens is 13 mm, the object side curvature radius is 242.955 mm, and the image side curvature radius is 369.549 mm; the center thickness of the second lens is 4 mm, the object side curvature radius is -331.554 mm, and the image side curvature radius is 212.430 mm; the center thickness of the third lens is 8 mm, the object side curvature radius is 385.056 mm, and the image side curvature radius is -312.355 mm; the center thickness of the fourth lens is 4 mm, the object side curvature radius is -93.890 mm, and the image side curvature radius is -164.769 mm; the center thickness of the fifth lens is 10 mm, the object side curvature radius is 117.015 mm, and the image side curvature radius is 495.086 mm.

[0013] Another object of the present invention is to provide a lens module, comprising the above-mentioned long-wave continuous zoom infrared lens and a detector, wherein the number of pixels of the detector is 1280×1024 and the pixel size is 12 μm.

[0014] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: (1) The system length of this application is relatively short, for example, the total length can be controlled within 330 mm; (2) It has a small number of lenses, a high light transmittance, and good imaging quality, and can match a detector with a pixel number of 1280×1024 and a pixel size of 12μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0016] Figure 1 This is the optical path diagram of the long-wave continuous zoom infrared lens of Example 1.

[0017] Figure 2 This is a lens composition diagram of the long-wave continuous zoom infrared lens of Example 1.

[0018] Figure 3 This is a point diagram of the long-wave continuous zoom infrared lens in the longest focal length state of Example 1.

[0019] Figure 4 This is the MTF diagram of the long-wave continuous zoom infrared lens in the longest focal length state of Example 1.

[0020] Figure 5This is a point diagram of the long-wave continuous zoom infrared lens in the shortest focal length state of Example 1.

[0021] Figure 6 This is the MTF diagram of the long-wave continuous zoom infrared lens in the shortest focal length state of Example 1.

[0022] Reference numerals: 1, first lens; 2, second lens; 3, third lens; 4, fourth lens; 5, fifth lens; 6, protective window; 7, image plane. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. It should be noted that the terms "first" and "second" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features.

[0024] For ease of understanding, the relevant terms involved are explained below.

[0025] The object side is the side of the lens along the direction of light propagation where the light is incident, that is, the surface of the lens close to the object side; the image side is the side of the lens along the direction of light propagation where the light is emitted, that is, the surface of the lens close to the image side; the meniscus lens, also known as a crescent lens, has one concave side and the other convex side near the optical axis.

[0026] like Figure 1 As shown, a long-wave continuous zoom infrared lens comprises a first lens 1, a movable lens group and a fifth lens 5 which are arranged in sequence on the same optical axis from the object side to the image side; wherein the first lens 1 is a meniscus lens with a convex surface facing the object side and has a positive optical power; the fifth lens 5 is a meniscus lens with a convex surface facing the object side and has a positive optical power; the first lens 1 and the fifth lens 5 are fixed in relative position; the movable lens group comprises a second lens 2, a third lens 3 and a fourth lens 4 which are arranged in sequence; the second lens 2 is a biconcave lens, the third lens 3 is a biconvex lens, and the fourth lens 4 is a meniscus lens with a convex surface facing the image side and has a negative optical power; the second lens 2, the third lens 3 and the fourth lens 4 can move along the optical axis to achieve continuous zoom.

[0027] In this solution, continuous zooming of the optical system is achieved by driving the second lens 2, the third lens 3, and the fourth lens 4 to move along the same optical axis. For example, when the lens of the present application needs to be changed from long focus to short focus, the second lens 2 moves toward the object side to compensate for the image plane movement caused by the lens movement; and in the process of changing the lens from short focus to long focus, the second lens 2 moves toward the image side; when the lens is in the longest focal length state, the variable interval between the first lens 1 and the second lens 2 is in the maximum state, the interval between the second lens 2 and the third lens 3 is in the minimum state, the variable interval between the third lens 3 and the fourth lens 4 is in the maximum state, and the variable interval between the fourth lens 4 and the fifth lens 5 is in the minimum state; when the lens is in the shortest focal length state, the variable interval between the first lens 1 and the second lens 2 is in the minimum state, the variable interval between the second lens 2 and the third lens 3 is in the maximum state, and the variable interval between the third lens 3 and the fourth lens 4 is in the minimum state.

[0028] As a specific implementation, the materials of the first lens 1 , the second lens 2 , the third lens 3 , the fourth lens 4 , and the fifth lens 5 are all germanium.

[0029] As a specific implementation, the object-side surface S3 of the second lens 2, the image-side surface S4 of the second lens 2, the object-side surface S5 of the third lens 3, the image-side surface S6 of the third lens 3, the image-side surface S8 of the fourth lens 4, and the image-side surface S10 of the fifth lens 5 are aspherical surfaces and satisfy the aspherical surface formula: Among them, Z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height r along the optical axis; c=1 / R; R is the paraxial curvature fitting radius of the mirror; k is the cone coefficient; A, B, C, D, E are high-order aspherical coefficients.

[0030] The object side surface S5 of the third lens 3 is a binary surface, which satisfies the above aspheric surface formula and satisfies the expression equation of the binary surface in Zemax: M(B1ρ 2 +B2ρ 4 +B3ρ 6 ), where M is the diffraction order, the diffraction order is 1, B1, B2, B3 are the binary surface phase coefficients, and ρ is the normalized radius.

[0031] As a specific implementation, a stop is provided on the object-side surface S5 of the third lens 3 .

[0032] Example 1 The following is an example of a specific continuous zoom infrared lens for description. Specific parameters of the continuous zoom infrared lens of this embodiment are shown in Table 1, Table 2, and Table 3.

[0033] Table 1 Parameters of each component Table 2 Aspheric surface data of lens Table 3. Binary surface data of lens When focusing, the first lens 1 and the fifth lens 5 are relatively fixed, while the second lens 2, the third lens 3, and the fourth lens 4 move between the first lens 1 and the fifth lens 5. The air interval between the first lens 1 and the second lens 2, the air interval between the second lens 2 and the third lens 3, the air interval between the third lens 3 and the fourth lens 4, and the air interval between the fourth lens 4 and the fifth lens 5 are all variable intervals. For example, when the air interval between the first lens 1 and the second lens 2 is 122.913 mm, the air interval between the third lens 3 and the second lens 2 is 8.934 mm, the air interval between the third lens 3 and the fourth lens 4 is 74.649 mm, and the air interval between the fourth lens 4 and the fifth lens 5 is 38.117 mm, the system focal length is in the longest focal state, and the longest focal length of this embodiment is 225 mm. When the air gap between the first lens 1 and the second lens 2 is 51.228 mm, the air gap between the third lens 3 and the second lens 2 is 126.355 mm, the air gap between the third lens 3 and the fourth lens 4 is 10.967 mm, and the air gap between the fourth lens 4 and the fifth lens 5 is 56.064 mm, the system focal length is in the shortest focal state, and the shortest focal length of this embodiment is 25 mm.

[0034] Figure 3 , Figure 4 They are the point diagram and MTF diagram of the lens at the longest focal length (225mm). Figure 5 , Figure 6 The following are the spot diagram and MTF diagram of the lens at the shortest focal length (25mm). In the MTF diagram, the horizontal axis represents different spatial frequencies and the vertical axis represents the modulation degree. All fields of view represent the MTF curve of the meridian plane. It can be seen that the MTF is close to the diffraction limit, the RMS diameter of the diffuse spot is smaller than the Airy disk diameter, and the image quality is good.

[0035] The long-wave continuous zoom infrared lens of this embodiment has an operating band of 8 μm to 12 μm, a resolution of 1280×1024, 12 μm, an F number of 1.4, and a focal length range of 25 to 225 mm.

[0036] Based on the same inventive concept, this embodiment provides a lens module, including the above-mentioned long-wave continuous zoom infrared lens and a detector, wherein the number of pixels of the detector is 1280×1024 and the pixel size is 12 μm.

[0037] Obviously, the above embodiments are merely examples for clearly explaining the technical solutions of the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the protection of the claims of the present invention.

Claims

1. A long-wave continuous zoom infrared lens, characterized in that: The lens comprises a first lens, a movable lens group and a fifth lens which are arranged in sequence on the same optical axis from the object side to the image side; The first lens is a meniscus lens with a convex surface facing the object, and has positive optical power; the fifth lens is a meniscus lens with a convex surface facing the object, and has positive optical power; the relative positions of the first lens and the fifth lens are fixed; The movable lens group includes a second lens, a third lens, and a fourth lens arranged in sequence; the second lens is a double concave lens; the third lens is a double convex lens; the fourth lens is a meniscus lens with the convex surface facing the image side and has negative optical power; the second lens, the third lens, and the fourth lens can move along the optical axis to achieve continuous zoom.

2. The long-wave continuous zoom infrared lens according to claim 1, characterized in that: When the lens changes from long focus to short focus, the second lens moves toward the object side; when the lens changes from short focus to long focus, the second lens moves toward the image side; When the lens is in the longest focal length state, the variable interval between the first lens and the second lens is in the maximum state, the variable interval between the second lens and the third lens is in the minimum state, the variable interval between the third lens and the fourth lens is in the maximum state, and the variable interval between the fourth lens and the fifth lens is in the minimum state; When the lens is in the shortest focal length state, the variable interval between the first lens and the second lens is in the minimum state, the variable interval between the second lens and the third lens is in the maximum state, and the variable interval between the third lens and the fourth lens is in the minimum state.

3. The long-wave continuous zoom infrared lens according to claim 1, characterized in that: The first lens, the second lens, the third lens, the fourth lens and the fifth lens are all made of germanium.

4. The long-wave continuous zoom infrared lens according to claim 1, characterized in that: The object side surface of the second lens, the image side surface of the second lens, the object side surface of the third lens, the image side surface of the third lens, the image side surface of the fourth lens, and the image side surface of the fifth lens are aspherical surfaces and satisfy the aspherical surface formula: Among them, Z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height r along the optical axis; c=1 / R; R is the paraxial curvature fitting radius of the mirror; k is the cone coefficient; A, B, C, D, and E are high-order aspherical coefficients.

5. The long-wave continuous zoom infrared lens according to claim 4, characterized in that: The object side surface of the third lens is a binary surface, which satisfies the aspheric surface formula and satisfies the expression equation of the binary surface in Zemax: M(B1ρ 2 +B2ρ 4 +B3ρ 6 ), where M is the diffraction order, B1, B2, B3 are the binary surface phase coefficients, and ρ is the normalized radius.

6. The long-wave continuous zoom infrared lens according to claim 1, characterized in that: An aperture is provided on the object side of the third lens.

7. The long-wave continuous zoom infrared lens according to any one of claims 1 to 6, characterized in that: The working band of the lens is 8 μm to 12 μm, and the focal length is 25 to 225 mm.

8. The long-wave continuous zoom infrared lens according to claim 7, characterized in that: The variable interval between the first lens and the second lens is 122.913-51.228 mm, the variable interval between the second lens and the third lens is 8.934-126.355 mm, the variable interval between the third lens and the fourth lens is 74.649-10.967 mm, and the variable interval between the fourth lens and the fifth lens is 38.117-57.066 mm.

9. The long-wave continuous zoom infrared lens according to claim 7, characterized in that: The center thickness of the first lens is 13mm, the radius of curvature of the object side is 242.955mm, and the radius of curvature of the image side is 369.549mm; the center thickness of the second lens is 4mm, the radius of curvature of the object side is -331.554mm, and the radius of curvature of the image side is 212.430mm; the center thickness of the third lens is 8mm, the radius of curvature of the object side is 385.056mm, and the radius of curvature of the image side is -312.355mm; the center thickness of the fourth lens is 4mm, the radius of curvature of the object side is -93.890mm, and the radius of curvature of the image side is -164.769mm; the center thickness of the fifth lens is 10mm, the radius of curvature of the object side is 117.015mm, and the radius of curvature of the image side is 495.086mm.

10. A lens module, characterized in that: It comprises the long-wave continuous zoom infrared lens and the detector as claimed in any one of claims 1 to 9, wherein the number of pixels of the detector is 1280×1024 and the pixel size is 12 μm.

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