Double-view-field infrared lens with large focal length range and imaging system

Abstract

The invention provides an imaging system which comprises a double-view-field infrared lens, the lens comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged in the optical axis transmission direction, the second lens can reciprocate in the optical axis direction, the air interval between the first lens and the second lens ranges from 73.36 mm to 36.9 mm, and the air interval between the first lens and the second lens ranges from 73.36 mm to 36.9 mm. The air gap between the second lens and the third lens ranges from 20.25 mm to 56.71 mm, and the air gap between the third lens and the fourth lens ranges from 38.44 mm. The lens is large in focal length range, can achieve long-distance imaging and is clear in imaging.

Description

Technical Field

[0001] The present application belongs to the field of infrared optical technology, and specifically relates to a dual-field-of-view infrared lens and imaging system. Background Art

[0002] CN114236793A discloses a F22.5-45MM dual-field infrared focusing lens, the optical system of which consists of a front fixed group, a field switching mirror and a rear fixed group arranged in sequence from front to back along the transmission direction of the optical axis; the front fixed group comprises a meniscus positive lens A with its convex surface facing the object side; the field switching mirror comprises a biconcave lens B; the rear fixed group comprises a biconvex lens C and a meniscus positive lens D with its convex surface facing the image side arranged in sequence along the transmission direction of the optical axis; the biconcave lens B can move forward and backward along the transmission direction of the optical axis; the lens can work at a working temperature of -40°C to 60°C and has a good imaging effect; the field of view switching is convenient, stable and fast.

[0003] However, the above dual-field-of-view infrared lens has a small focal range and cannot perform long-distance imaging. Summary of the invention

[0004] In view of the above technical problems, it is necessary to provide a dual-field-of-view infrared lens and an imaging system with a large focal length range.

[0005] The technical solution proposed in this application is: A dual-field-of-view infrared lens comprises a first lens, a second lens, a third lens, and a fourth lens arranged in sequence along an optical axis transmission direction, wherein the second lens can move back and forth along the optical axis direction, and the air gap between the first lens and the second lens is 73.36-36.9 mm, the air gap between the second lens and the third lens is 20.25-56.71 mm, and the air gap between the third lens and the fourth lens is 38.44 mm.

[0006] Furthermore, the center thickness of the first lens is 8.5 mm, the object side curvature radius is 125.050 mm, and the image side curvature radius is 174.381 mm; the center thickness of the second lens is 3 mm, the object side curvature radius is -192.595 mm, and the image side curvature radius is 190.370 mm; the center thickness of the third lens is 7 mm, the object side curvature radius is 364.486 mm, and the image side curvature radius is -348 mm; the center thickness of the fourth lens is 6.3 mm, the object side curvature radius is 1136.199 mm, and the image side curvature radius is -258 mm.

[0007] Further, the focal length is 40~120mm; When the focal length is 40 mm, the air space between the first lens and the second lens is 36.9 mm, and the air space between the second lens and the third lens is 56.71 mm; When the focal length is 120 mm, the air space between the first lens and the second lens is 73.36 mm, and the air space between the second lens and the third lens is 20.25 mm.

[0008] Furthermore, the first lens, the second lens, the third lens, and the fourth lens are made of germanium single crystal.

[0009] Furthermore, the first lens is a meniscus positive lens with a convex surface facing the object side, the second lens is a double concave negative lens, the third lens is a double convex positive lens, and the fourth lens is a double convex positive lens.

[0010] Furthermore, the image side surface of the first lens, the object side surface of the second lens, the object side surface of the third lens, and the object side surface of the fourth lens are all 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.

[0011] 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. 1= -26.687, B 2= 2.9811, B 3= -0.0493, ρ=35.

[0012] Furthermore, the lens has an operating band of 8-12 μm and an F number of 1.

[0013] An imaging system comprises the dual-field-of-view infrared lens as described above and a detector for receiving images formed by the dual-field-of-view infrared lens.

[0014] Furthermore, the detector is a non-cooled detector, and the resolution of the detector is 1280×1024, and the pixel size is 12 μm.

[0015] The imaging system provided by the present application includes a dual-field infrared lens and a detector. The focal length of the lens is 40-120 mm, the working band is 8-12 μm, and the F number is 1. The detector is a non-cooled detector, and the resolution of the detector is 1280×1024, and the pixel size is 12 μm. At the same time, the lens has a large focal length range and clear imaging, and can be applied to the monitoring of objects at different distances. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide further understanding of the present application and constitute a part of the specification. They are used to explain the present application together with the embodiments of the present application and do not constitute a limitation of the present application.

[0017] Figure 1 A diagram of the lens composition of the imaging system provided for this application; Figure 2 MTF diagram of the dual-field infrared lens provided for this application at a focal length of 120mm; Figure 3 The spot diagram of the dual-field infrared lens provided for this application when the focal length is 120mm; Figure 4 MTF diagram of the dual-field infrared lens provided for this application at a focal length of 40mm; Figure 5 The spot diagram of the dual-field infrared lens provided for this application when the focal length is 40mm; Description of labels: 11. First lens; 12. Second lens; 13. Third lens; 14. Fourth lens; 21. Protection window; 22. Detector focal plane array. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] The present application provides an imaging system, which includes a dual-field-of-view infrared lens and a detector. The focal length of the lens is 40~120mm, the working band is 8~12μm, and the F number is 1; the detector is a non-cooled detector, and the resolution of the detector is 1280×1024, and the pixel size is 12μm.

[0020] like Figure 1As shown, the lens comprises a first lens 11, a second lens 12, a third lens 13, and a fourth lens 14 arranged in sequence along the optical axis transmission direction. The second lens 12 can reciprocate along the optical axis direction, and the air interval between the first lens 11 and the second lens 12 is 73.36-36.9 mm, the air interval between the second lens 12 and the third lens 13 is 20.25-56.71 mm, and the air interval between the third lens 13 and the fourth lens 14 is 38.44 mm.

[0021] Specifically, when the focal length is 40 mm, the air interval between the first lens 11 and the second lens 12 is 36.9 mm, and the air interval between the second lens 12 and the third lens 13 is 56.71 mm.

[0022] When the focal length is 120 mm, the air interval between the first lens 11 and the second lens 12 is 73.36 mm, and the air interval between the second lens 12 and the third lens 13 is 20.25 mm.

[0023] In one embodiment, the detector includes a protection window 21 and a detector focal plane array 22, such as Figure 1 As shown, the light beam passes through the first lens 11, the second lens 12, the third lens 13, and the fourth lens 14 from left to right, and then forms an image on the detector focal plane array 22 through the protective window 21. In practical applications, the air gap between the fourth lens 14 and the protective window 21 is 37.83 mm.

[0024] In one embodiment, the first lens 11 is a positive meniscus lens with a convex surface facing the object side, the second lens 12 is a double concave negative lens, the third lens 13 is a double convex positive lens, and the fourth lens 14 is a double convex positive lens.

[0025] Further, the center thickness of the first lens 11 is 8.5 mm, the radius of curvature of the object side is 125.050 mm, and the radius of curvature of the image side is 174.381 mm; the center thickness of the second lens 12 is 3 mm, the radius of curvature of the object side is -192.595 mm, and the radius of curvature of the image side is 190.370 mm; the center thickness of the third lens 13 is 7 mm, the radius of curvature of the object side is 364.486 mm, and the radius of curvature of the image side is -348 mm; the center thickness of the fourth lens 14 is 6.3 mm, the radius of curvature of the object side is 1136.199 mm, and the radius of curvature of the image side is -258 mm.

[0026] It can be understood that the incident direction of the light is the object side, and the outgoing direction is the image side. Figure 1 For example, along the optical axis from left to right, the left side of the lens is the object side, and the right side is the image side. For example, the S1 surface of the first lens 11 is the object side surface, and the S2 surface is the image side surface. Other lenses are not described here.

[0027] In one embodiment, the first lens 11, the second lens 12, the third lens 13, and the fourth lens 14 are all made of germanium single crystal. The parameters of each lens can be found in Table 1.

[0028] Table 1 Lens parameters In one embodiment, the image side surface of the first lens 11, the object side surface of the second lens 12, the object side surface of the third lens 13, and the object side surface of the fourth lens 14 are all 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.

[0029] Table 2 Aspheric coefficients 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. M is 1, B1=-26.687, B2=2.9811, B3=-0.0493, ρ=35.

[0030] Figure 2 This is the MTF diagram when the focal length is 120mm. Figure 3 This is the spot diagram when the focal length is 120mm; Figure 4 This is the MTF diagram when the focal length is 40mm. Figure 5 This is the spot diagram when the focal length is 40mm. In the MTF diagram, the horizontal axis represents different spatial frequencies and the vertical axis represents the modulation degree. It can be seen that the MTF is close to the diffraction limit, the RMS of the diffuse spot is smaller than the Airy disk diameter, and the image quality is good.

[0031] In summary, the imaging system provided by the present application includes a dual-field infrared lens and a detector. The focal length of the lens is 40-150 mm, the working band is 8-12 μm, and the F number is 1. The detector is an uncooled detector, and the resolution of the detector is 1280×1024, and the pixel size is 12 μm. At the same time, the lens has clear imaging and a large focal length range.

[0032] Although the embodiments of the present application have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A dual-field-of-view infrared lens, characterized in that: It includes a first lens, a second lens, a third lens, and a fourth lens arranged in sequence along the transmission direction of the optical axis, the second lens can move back and forth along the optical axis, and the air gap between the first lens and the second lens is 73.36~36.9mm, the air gap between the second lens and the third lens is 20.25~56.71mm, and the air gap between the third lens and the fourth lens is 38.44mm.

2. The dual-field-of-view infrared lens according to claim 1, characterized in that: The center thickness of the first lens is 8.5mm, the radius of curvature of the object side is 125.050mm, and the radius of curvature of the image side is 174.381mm; the center thickness of the second lens is 3mm, the radius of curvature of the object side is -192.595mm, and the radius of curvature of the image side is 190.370mm; the center thickness of the third lens is 7mm, the radius of curvature of the object side is 364.486mm, and the radius of curvature of the image side is -348mm; the center thickness of the fourth lens is 6.3mm, the radius of curvature of the object side is 1136.199mm, and the radius of curvature of the image side is -258mm.

3. The dual-field-of-view infrared lens according to claim 1, characterized in that: Focal length is 40~120mm; When the focal length is 40 mm, the air space between the first lens and the second lens is 36.9 mm, and the air space between the second lens and the third lens is 56.71 mm; When the focal length is 120 mm, the air space between the first lens and the second lens is 73.36 mm, and the air space between the second lens and the third lens is 20.25 mm.

4. The dual-field-of-view infrared lens according to claim 1, characterized in that: The first lens, the second lens, the third lens, and the fourth lens are made of germanium single crystal.

5. The dual-field-of-view infrared lens according to claim 1, wherein: The first lens is a meniscus positive lens with a convex surface facing the object side, the second lens is a double concave negative lens, the third lens is a double convex positive lens, and the fourth lens is a double convex positive lens.

6. The dual-field-of-view infrared lens according to claim 1, wherein: The image side surface of the first lens, the object side surface of the second lens, the object side surface of the third lens, and the object side surface of the fourth lens are all 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.

7. The dual-field-of-view infrared lens according to claim 6, 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; M is 1, B 1= -26.687, B 2= 2.9811, B 3= -0.0493, ρ=35.

8. The dual-field-of-view infrared lens according to claim 1, characterized in that: The lens has an operating band of 8 to 12 μm and an F number of 1.

9. An imaging system, characterized in that: It comprises the dual-field-of-view infrared lens as described in any one of claims 1 to 8 and a detector for receiving images formed by the dual-field-of-view infrared lens.

10. The imaging system according to claim 9, characterized in that The detector is a non-cooling detector, and the resolution of the detector is 1280×1024, and the pixel size is 12 μm.

Images