A middle wave dual view field infrared lens and an imaging device

Abstract

The application belongs to the field of infrared optical technology and discloses a kind of middle wave double view field infrared lens and imaging device.The lens includes front fixed group, field of view switching mirror and rear fixed group which are coaxially arranged in turn along the transmission direction of optical axis.The front fixed group is the first lens.The field of view switching mirror is the second lens, and the second lens moves along the optical axis to realize the field of view switching of short focus 55mm and long focus 220mm.The rear fixed group is composed of third lens, fourth lens, fifth lens, sixth lens, seventh lens and eighth lens in turn.The lens realizes the double field of view switching of short focus and long focus through the movement of the second lens, and the field of view switching is convenient;without additional setting adjusting lens and diffraction surface for temperature and distance compensation, the imaging quality is good;it can match the detector with pixel number 640×512 and pixel size 15μm, the working waveband is 3.7μm-4.8μm, and it is suitable for target detection in bad environment with smoke, cloudy and the like.

Description

Technical Field

[0001] This technology belongs to the field of infrared optical technology, and specifically relates to a mid-wave dual-field infrared lens and imaging device. Background Technology

[0002] Mid-wave cooled infrared detectors, due to their high sensitivity, superior penetration performance, ease of observing high-temperature targets, and significant price advantage over similar long-wave infrared detectors, have broad application prospects in military and related civilian fields such as target search, missile early warning detection, and intelligence reconnaissance. With the development of mid-wave cooled detectors, higher requirements are being placed on their matching mid-wave dual-field-of-view infrared lenses.

[0003] Dual-field-of-view infrared lenses can rapidly switch fields of view, combining the wide coverage of a short focal length field of view with the high resolution of a long focal length field of view. Working together, they can achieve large-field-of-view target search and small-field-of-view tracking and measurement. To achieve greater detection distances, lenses with large target surfaces and long focal lengths are required. However, in the structural design of dual-field-of-view optical systems, especially for lenses with large target surfaces and long focal lengths, in order to further compensate for the effects of temperature and distance, in addition to the adjustment lenses for field-of-view switching, additional adjustment lenses for temperature and distance compensation are needed, further complicating the structure of the dual-field-of-view optical system. Alternatively, diffraction techniques may be used, reducing the system's transmittance. Summary of the Invention

[0004] To address the above issues, this invention proposes a mid-wave dual-field-of-view infrared lens, employing a field-of-view switching mirror to achieve two focal lengths: a short focal length of 55mm and a long focal length of 220mm, resulting in high image quality. The specific technical solution is as follows.

[0005] A mid-wave dual-field infrared lens, comprising a front fixed group, a field-of-view switching mirror, and a rear fixed group arranged coaxially along the optical axis transmission direction; the front fixed group is a first lens; the field-of-view switching mirror is a second lens, the second lens moving along the optical axis to achieve field-of-view switching between a short focal length of 55mm and a long focal length of 220mm; the rear fixed group consists of a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially.

[0006] Further, the first lens has a center thickness of 11.6 mm, an object-side radius of curvature of 157.73 mm, and an image-side radius of curvature of 304.74 mm; the second lens has a center thickness of 5 mm, an object-side radius of curvature of -205.9 mm, and an image-side radius of curvature of 207.88 mm; the third lens has a center thickness of 4 mm, an object-side radius of curvature of 91 mm, and an image-side radius of curvature of 75 mm; the fourth lens has a center thickness of 9 mm, an object-side radius of curvature of 84.9 mm, and an image-side radius of curvature of 2616.2 mm; the third... The fifth lens has a center thickness of 4.8 mm, an object-side radius of curvature of -19.86 mm, and an image-side radius of curvature of -22.56 mm; the sixth lens has a center thickness of 5.5 mm, an object-side radius of curvature of 65 mm, and an image-side radius of curvature of -71.52 mm; the seventh lens has a center thickness of 6.7 mm, an object-side radius of curvature of -21.65 mm, and an image-side radius of curvature of 60.66 mm; and the eighth lens has a center thickness of 5.9 mm, an object-side radius of curvature of -174.55 mm, and an image-side radius of curvature of -30.68 mm.

[0007] Furthermore, the air gap between the first lens and the second lens is adjustable from 19mm to 69.43mm; the air gap between the second lens and the third lens is adjustable from 10mm to 60.42mm; the air gap between the third lens and the fourth lens is 1.35mm; the air gap between the fourth lens and the fifth lens is 84.61mm; the air gap between the fifth lens and the sixth lens is 11mm; the air gap between the sixth lens and the seventh lens is 5.24mm; and the air gap between the seventh lens and the eighth lens is 4.97mm.

[0008] Furthermore, the operating wavelength of the lens is 3.7μm-4.8μm.

[0009] Furthermore, the first lens, the fourth lens, the sixth lens, and the eighth lens are made of silicon; the second lens and the third lens are made of germanium; the fifth lens is made of zinc selenide; and the seventh lens is made of zinc sulfide.

[0010] Furthermore, the lens also includes a protective window, a chopper window, and a cold screen arranged sequentially after the rear fixing group.

[0011] Furthermore, the object-side surfaces of the second lens, the third lens, the fifth lens, and the seventh lens are all aspherical and satisfy the aspherical formula:

[0012]

[0013] Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

[0014] Another object of the present invention is to provide an imaging device, including the above-described mid-wave dual-field infrared lens and a detector for receiving the image formed by the mid-wave dual-field infrared lens.

[0015] Furthermore, the detector is a cooled detector with 640×512 pixels and a pixel size of 15μm.

[0016] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0017] The lens of this invention achieves dual field-of-view switching between a short focal length of 55mm and a long focal length of 220mm by moving the second lens, making field-of-view switching convenient; it eliminates the need for additional adjustment lenses and diffraction surfaces for temperature and distance compensation, resulting in good image quality; it can be matched with detectors with a pixel count of 640×512 and a pixel size of 15μm, and operates in the 3.7μm-4.8μm band, making it suitable for target detection in harsh environments such as smoke and clouds. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a diagram showing the lens composition of the mid-wave dual-field infrared lens in Example 1;

[0020] Figure 2 This is the optical path diagram of the mid-wave dual-field infrared lens in Example 1;

[0021] Figure 3 This is a dot plot of the 220mm focal length of the mid-wave dual-field infrared lens in Example 1;

[0022] Figure 4 The MTF diagram for the 220mm focal length of the mid-wave dual-field infrared lens in Example 1 is shown.

[0023] Figure 5 This is a dot plot of the 55mm focal length of the mid-wave dual-field infrared lens in Example 1;

[0024] Figure 6The image shows the MTF diagram of the mid-wave dual-field infrared lens with a focal length of 55mm in Example 1.

[0025] Reference numerals: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Eighth lens; 9. Protective window; 10. Chopper window; 11. Focal plane array of the detector. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that the terms "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features.

[0027] Example 1

[0028] This embodiment provides a mid-wave dual-field-of-view infrared lens. The lens includes a front fixed group, a field-of-view switching mirror, and a rear fixed group, coaxially arranged along the optical axis transmission direction. The following example uses a mid-wave dual-field-of-view infrared lens applied to a 640×512, 15μm cooled detector, with an operating wavelength of 3.7μm-4.8μm. Figure 1 As shown, the front fixed group is the first lens 1; the field-of-view switching mirror is the second lens 2; and the rear fixed group consists of the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 arranged in sequence.

[0029] The air gap between the first lens 1 and the second lens 2 is adjustable from 19mm to 69.43mm; the air gap between the second lens 2 and the third lens 3 is adjustable from 10mm to 60.42mm; the air gap between the third lens 3 and the fourth lens 4 is 1.35mm; the air gap between the fourth lens 4 and the fifth lens 5 is 84.61mm; the air gap between the fifth lens 5 and the sixth lens 6 is 11mm; the air gap between the sixth lens 6 and the seventh lens 7 is 5.24mm; and the air gap between the seventh lens 7 and the eighth lens 8 is 4.97mm.

[0030] Adjusting the second lens 2 to switch between large and small fields of view: When changing to a short focal length of 55mm, the second lens 2 moves towards the object side until the air gap between the first lens 1 and the second lens 2 is 19mm, and the air gap between the second lens 2 and the third lens 3 is 60.42mm; when changing to a long focal length of 220mm, the second lens 2 moves towards the image side until the air gap between the first lens 1 and the second lens 2 is 69.43mm, and the air gap between the second lens 2 and the third lens 3 is 10mm.

[0031] like Figure 2 As shown, the light beam passes sequentially from left to right through the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8, and then through the protective window 9, the chopper window 10, and the cold screen located after the rear fixed group, before being imaged on the detector focal plane array 11. In this embodiment, the mid-wave dual-field-of-view infrared lens achieves the switching between a short focal length 55mm field of view and a long focal length 220mm field of view by moving the second lens 2 along the optical axis.

[0032] As shown in Table 1, in one specific embodiment, the first lens 1 has a center thickness of 11.6 mm, an object-side radius of curvature of 157.73 mm, and an image-side radius of curvature of 304.74 mm; the second lens 2 has a center thickness of 5 mm, an object-side radius of curvature of -205.9 mm, and an image-side radius of curvature of 207.88 mm; the third lens 3 has a center thickness of 4 mm, an object-side radius of curvature of 91 mm, and an image-side radius of curvature of 75 mm; and the fourth lens 4 has a center thickness of 9 mm, an object-side radius of curvature of 84.9 mm, and an image-side radius of curvature of 2616.2 mm. The fifth lens 5 has a center thickness of 4.8 mm, an object-side radius of curvature of -19.86 mm, and an image-side radius of curvature of -22.56 mm; the sixth lens 6 has a center thickness of 5.5 mm, an object-side radius of curvature of 65 mm, and an image-side radius of curvature of -71.52 mm; the seventh lens 7 has a center thickness of 6.7 mm, an object-side radius of curvature of -21.65 mm, and an image-side radius of curvature of 60.66 mm; the eighth lens 8 has a center thickness of 5.9 mm, an object-side radius of curvature of -174.55 mm, and an image-side radius of curvature of -30.68 mm. It can be understood that along the optical axis from left to right, the left side is the object side, and the right side is the image side. For example, the S1 surface of the first lens 1 is the object side, and the S2 surface is the image side. Other lenses will not be described further here.

[0033] Table 1 Parameters of each lens

[0034]

[0035] In a specific implementation, the first lens 1, the fourth lens 4, the sixth lens 6, and the eighth lens 8 are made of silicon; the second lens 2 and the third lens 3 are made of germanium; the fifth lens 5 is made of zinc selenide; and the seventh lens 7 is made of zinc sulfide.

[0036] As shown in Table 2, the object-side surface S3 of the second lens, the object-side surface S5 of the third lens, the object-side surface S9 of the fifth lens, and the object-side surface S13 of the seventh lens are all aspherical surfaces and satisfy the aspherical surface formula:

[0037]

[0038] In the formula: Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

[0039] Table 2 Aspheric coefficient data

[0040]

[0041] Figure 4 , Figure 6 These are the MTF plots for the long and short focal lengths of a mid-wave dual-field infrared lens, respectively. The horizontal axis represents different spatial frequencies, and the vertical axis represents modulation degree. The MTF curves for all fields of view representing the meridional plane are shown as the curve labeled T in the figure, while the MTF curve representing the sagittal plane is shown as the curve labeled S in the figure. The label DIFF.LIMIT represents the diffraction limit. Figure 3 , Figure 5 The images show dot plots for the mid-wave dual-field infrared lens at both long and short focal lengths. It can be seen that the MTF is close to the diffraction limit, the root-mean-square diameter of the diffuse spot is smaller than the Airy disk diameter, and the image quality is good.

[0042] The mid-wave dual-field infrared lens in this embodiment operates in the 3.7μm-4.8μm band; has a focal length f′=55 / 220mm; a resolution of 640×512, 15μm; an F number of 2; no diffraction surface, resulting in good imaging quality; and strong penetration, making it particularly suitable for target detection in harsh environments such as smoke and clouds.

[0043] Obviously, the above embodiments are merely examples to clearly illustrate the technical solutions of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A mid-wave dual-field infrared lens, characterized in that, The lens comprises a front fixed group, a field-of-view switching lens, and a rear fixed group arranged coaxially along the optical axis transmission direction; the front fixed group is a first lens; the field-of-view switching lens is a second lens, which moves along the optical axis to achieve field-of-view switching between a short focal length of 55mm and a long focal length of 220mm; the rear fixed group consists of a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in sequence; the lens contains eight lenses with optical power. The first lens has a center thickness of 11.6 mm, an object-side radius of curvature of 157.73 mm, and an image-side radius of curvature of 304.74 mm; the second lens has a center thickness of 5 mm, an object-side radius of curvature of -205.9 mm, and an image-side radius of curvature of 207.88 mm; the third lens has a center thickness of 4 mm, an object-side radius of curvature of 91 mm, and an image-side radius of curvature of 75 mm; the fourth lens has a center thickness of 9 mm, an object-side radius of curvature of 84.9 mm, and an image-side radius of curvature of 2616.2 mm; the fifth lens... The center thickness of the first lens is 4.8 mm, the object-side radius of curvature is -19.86 mm, and the image-side radius of curvature is -22.56 mm; the center thickness of the sixth lens is 5.5 mm, the object-side radius of curvature is 65 mm, and the image-side radius of curvature is -71.52 mm; the center thickness of the seventh lens is 6.7 mm, the object-side radius of curvature is -21.65 mm, and the image-side radius of curvature is 60.66 mm; the center thickness of the eighth lens is 5.9 mm, the object-side radius of curvature is -174.55 mm, and the image-side radius of curvature is -30.68 mm. The first, fourth, sixth, and eighth lenses are made of silicon; the second and third lenses are made of germanium; the fifth lens is made of zinc selenide; and the seventh lens is made of zinc sulfide.

2. The mid-wave dual-field infrared lens according to claim 1, characterized in that, The air gap between the first and second lenses is adjustable from 19mm to 69.43mm; the air gap between the second and third lenses is adjustable from 10mm to 60.42mm; the air gap between the third and fourth lenses is 1.35mm; the air gap between the fourth and fifth lenses is 84.61mm; the air gap between the fifth and sixth lenses is 11mm; the air gap between the sixth and seventh lenses is 5.24mm; and the air gap between the seventh and eighth lenses is 4.97mm.

3. The mid-wave dual-field infrared lens according to any one of claims 1 to 2, characterized in that, The object-side surfaces of the second lens, the third lens, the fifth lens, and the seventh lens are all aspherical and satisfy the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

4. The mid-wave dual-field infrared lens according to claim 1, characterized in that, The lens also includes a protective window, a chopper window, and a cold screen, which are arranged sequentially after the rear fixing group.

5. The mid-wave dual-field infrared lens according to claim 1, characterized in that, The lens operates in the wavelength range of 3.7μm-4.8μm.

6. An imaging device, characterized in that, It includes the mid-wave dual-field infrared lens as described in any one of claims 1 to 5 and a detector for receiving the image formed by the mid-wave dual-field infrared lens.

7. The imaging apparatus according to claim 6, characterized in that, The detector is a cooled detector with 640×512 pixels and a pixel size of 15μm.

Images