Long-distance infrared detection system with total entrance pupil filling rate and laminated array structure

Abstract

The invention discloses a long-distance infrared detection system with a total entrance pupil filling rate and a laminated array structure, and belongs to the technical field of optical detection. The prior art is complex in structure and strong and weak in received light. A front laminated lens array, a rear laminated lens array, an array rear diaphragm and a subsequent lens group are sequentially arranged on the same optical axis from the incident direction of imaging infrared light to the emergent direction of the imaging infrared light; each of the front laminated lens array and the rear laminated lens array is formed by laminating n * n sub-lenses a and sub-lenses b; the cross sections of the sub-lens a and the sub-lens b are square; the front laminated lens array and the rear laminated lens array form a lens array group, the entrance pupil of the lens array group is located at the incident mirror surface of the front laminated lens array, and the exit pupil of the lens array group is overlapped with the position of the rear diaphragm; the front laminated lens array can be offset by + / -delta 1 relative to the optical axis in the radial direction, and the rear-array diaphragm is offset by + / -delta 2 in the direction opposite to the offset direction of the front laminated lens array. The method can be used for searching and identifying infrared targets in the civil field.

Description

Technical Field

[0001] The invention belongs to the technical field of optical detection. Background Art

[0002] Long-distance infrared optical detection of targets is achieved by using the self-radiation of the detected target. Compared with visible light optical detection, infrared optical detection has the advantages of all-weather, no environmental influence, strong penetration, etc. With the development of infrared focal plane array devices, infrared optical detection technology has evolved from the original hot spot detection to imaging detection. The infrared detection system that has emerged can achieve more accurate identification of targets and has become the main means of obtaining target information.

[0003] In the prior art, there are two types of infrared detection systems used for long-distance target detection:

[0004] The first is a scheme disclosed in a Chinese utility model patent with application number 201820201750.9 and the name of "Ultra-long-range passive infrared detection system and ship navigation avoidance warning system". The components of the scheme include optical elements, such as narrow-band interference filter lenses, hemispherical Fresnel lenses, etc.; optoelectronic components, such as infrared detectors; electrical components, such as post-amplifiers; and precision mechanical parts, such as pan / tilts. In this scheme, multiple infrared receiving units are combined into an array. In each infrared receiving unit, a Fresnel lens is used, and each lens end face is inlaid with multiple infrared detectors; the narrow-band interference filter lens is arranged parallel to the main mounting plate, and the distance between the two is 20 to 25 cm. The detection distance of this scheme reaches 150 to 200 km for aerial targets and 40 to 50 km for sea targets; the detection azimuth reaches 360°. This scheme is applied in the field of military detection, and can receive the beam of ultra-long-range infrared targets, realize the detection of ultra-long-range invisible targets, and become a highly concealed military detection system. However, it can also be seen that this solution has its shortcomings, such as complex structure, high manufacturing cost, loose structure, large size, and insufficient light energy that can be received.

[0005] The second is a solution disclosed in a Chinese utility model patent with application number 202022905288.0 and the name "Dual Field Scanning Infrared Optical System". The solution consists of a telescope assembly, a scanning mirror assembly, an imaging lens assembly and an infrared detector assembly. In two modes, the large field of view (search) and the small field of view (identification) are scanned respectively. In the small field of view mode, the field of view lens group in the telescope assembly moves out of the light path, and the infrared light from the target enters the objective lens and directly irradiates the focusing lens. The light energy is lossless in this link. However, the structure of this solution is relatively complex due to the structural characteristics of its telescope assembly; a large amount of light energy cannot enter the optical system, so the light energy utilization rate is low, resulting in a short detection distance; in the process of switching between large and small fields of view, the driving assembly needs to move the field of view lens group with large movements, and in the scanning working mode, the scanning mirror assembly needs to swing at high frequency. These make the scheme have many mechanical movements and large movements, which limits the application of this scheme. Summary of the invention

[0006] In order to simplify the structure of the detection system, improve its compactness, reduce its size, simplify the operating actions to the greatest extent, receive imaging light to the greatest extent, and reduce the manufacturing cost of the detection system under the premise of achieving long-range infrared detection, this patent application proposes an invention called "Long-range infrared detection system with full pupil filling rate and stacked array structure".

[0007] The long-distance infrared detection system with full pupil filling rate and stacked array structure of the present invention is characterized by: Figure 1 As shown, from the incident direction to the emitting direction of the imaging infrared light, the front stacked lens array 1, the rear stacked lens array 2, the rear aperture 3, and the subsequent lens group 4 are arranged in sequence on the same optical axis; the front stacked lens array 1 and the rear stacked lens array 2 are each composed of n×n sub-lenses a and sub-lenses b stacked, as shown in FIG. Figure 2 , Figure 3 as well as Figure 1 As shown; the cross sections of sub-lens a and sub-lens b are both square, as shown Figure 4 As shown, sub-lens a and sub-lens b are both positive focal length meniscus thick lenses, the curvature radii of the incident mirror surface and the exit mirror surface of sub-lens a are both positive, and the curvature radii of the incident mirror surface and the exit mirror surface of sub-lens b are both negative; the post-array aperture 3 is composed of n×n sub-apertures c, as shown in Figure 2 , Figure 3 as well as Figure 1 As shown; the front stacked lens array 1 and the rear stacked lens array 2 constitute a lens array group, such as Figure 1 As shown, the entrance pupil 5 of the lens array group is located at the incident mirror surface of the front stacked lens array 1, and the exit pupil 6 of the lens array group overlaps with the position of the rear aperture 3; Figure 3 , Figure 4As shown, the front stacked lens array 1 can be shifted by ±Δ1 relative to the optical axis in the radial direction, and the rear aperture 3 can be shifted by ±Δ2 in the direction opposite to the shift direction of the front stacked lens array 1 at the same time.

[0008] The imaging process of the long-distance infrared detection system with full pupil filling rate and stacked array structure of the present invention is described as follows.

[0009] The imaging infrared light from the detected target is parallel to the optical axis of the long-range infrared detection system and fills the entrance pupil 5, as shown in Figure 1 , Figure 2 As shown, the image is formed on the intermediate image plane 7 through the front stacked lens array 1, and then passes through the rear stacked lens array 2 and the rear aperture 3 in sequence, and finally converges on the image plane 8 by the subsequent lens group 4 to complete the target image detection.

[0010] The imaging infrared light from the detected target and the optical axis of the long-range infrared detection system fill the entrance pupil 5 at a certain field of view angle (FOV), such as Figure 3 , Figure 4 As shown, at this time, the front stacked lens array 1 is shifted by ±Δ1 relative to the optical axis in the radial direction, and the rear aperture 3 is shifted by ±Δ2 in the direction opposite to the shift direction of the front stacked lens array 1. The imaging infrared light passes through the front stacked lens array 1, the rear stacked lens array 2, and the rear aperture 3 in sequence, and is finally converged on the image plane 8 by the subsequent lens group 4 to complete the target image detection.

[0011] When the imaging infrared light enters the front stacked lens array 1 at a certain viewing angle, such as 3.5°, the front stacked lens array 1 is displaced by Δ1, such as 1.39 mm, relative to the optical axis in the radial direction, and the rear aperture 3 is displaced by Δ2, such as 0.753 mm, in the direction opposite to the displaced direction of the front stacked lens array 1. Figure 3 , Figure 4 As shown, at this time, the imaging infrared light can fill the entrance pupil 5 with a full entrance pupil filling rate, as shown in FIG. Figure 5 As shown, the light energy receiving rate of the imaging infrared light is greatly improved. Although the imaging infrared light from the detected target suffers a large loss after being propagated through the atmosphere over a long distance (such as 8km to 10km), the imaging infrared light received by the long-distance infrared detection system of the present invention still has a light intensity that can produce high-brightness and clear imaging, thereby realizing infrared image detection of long-distance targets. If the imaging infrared light is incident on the front stacked lens array 1 at a certain field of view angle, and the front stacked lens array 1 and the rear aperture 3 remain in their original positions, light shearing will occur at the entrance pupil 5, and no imaging infrared light will be incident on the edge of each sub-lens a, as shown in FIG. Figure 6 As shown, the reception rate of imaging infrared light is greatly reduced, and the intensity of the received imaging infrared light is difficult to meet the needs of long-distance infrared target image detection.

[0012] On the premise of realizing long-distance infrared detection, since the components of the present invention are only the front stacked lens array 1, the rear stacked lens array 2, the rear aperture 3, and the subsequent lens group 4, compared with the prior art, the present invention simplifies the structure of the detection system, improves its compactness, and reduces its volume. For example, the total optical length of the long-distance infrared detection system is only 120 mm.

[0013] During the imaging process of the present invention, only the front stacked lens array 1 and the rear aperture 3 have a small millimeter-level offset movement. Therefore, compared with the prior art, the present invention simplifies the operating action to the greatest extent and receives the imaging infrared light to the greatest extent.

[0014] In summary, the manufacturing cost of the present invention is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall structure and imaging process of the present invention. In the figure, the imaging infrared light is parallelly incident on the front stacked lens array.

[0016] Figure 2 The figure is a schematic diagram of the optical path of a group of sub-lenses a, a sub-lens b and a sub-aperture c of the present invention for incident and emitted imaging infrared light. In the figure, the imaging infrared light is incident on the sub-lens a in parallel.

[0017] Figure 3 The figure is a schematic diagram of the optical path of a group of sub-lenses a, a sub-lens b and a sub-aperture c of the present invention for incident and emitted imaging infrared light. In the figure, the imaging infrared light is incident on the sub-lens a at a certain field angle.

[0018] Figure 4 It is a schematic diagram of the overall structure and imaging process of the present invention. In the figure, imaging infrared light is incident on the front stacked lens array at a certain field angle. The figure also serves as an abstract figure.

[0019] Figure 5 Schematic diagram of the incident effect of the stacked lens array still achieving full pupil filling rate before imaging infrared light is incident at a certain field of view angle.

[0020] Figure 6 Schematic diagram of the problem that the stacked lens array fails to fully fill the pupil when imaging infrared light is incident at a certain field of view angle.

[0021] Figure 7 It is the standard spot diagram of the present invention under the state of parallel incidence of imaging infrared light.

[0022] Figure 8 It is the standard spot diagram of the present invention when the imaging infrared light is incident at a certain field angle.

[0023] Fig. 9It is the MTF curve diagram of the present invention under the state of parallel incident imaging infrared light.

[0024] Fig.10 It is an MTF curve diagram of the present invention when the imaging infrared light is incident at a certain field angle. DETAILED DESCRIPTION

[0025] The technical features that require further definition of the present invention are as follows.

[0026] The front stacked lens array 1 and the rear stacked lens array 2 are each composed of n×n sub-lenses a and sub-lenses b stacked together. Figure 2 , Figure 3 as well as Figure 1 As shown, the value of n×n is 3×3 to 7×7, such as 5×5. The 5×5 stacking arrangement not only takes into account the requirements of the diffraction performance, geometric image quality, total optical length and displacement amplitude of the long-range infrared detection system, but also realizes long-range infrared image detection by using only a small number of array units, which is beneficial to the installation and adjustment of the long-range infrared detection system.

[0027] The material of sub-lens a and sub-lens b are both germanium.

[0028] The post-array aperture 3 is composed of n×n sub-apertures c, such as Figure 2 , Figure 3 as well as Figure 1 As shown, the value of n×n is the same as that of sub-lens a and sub-lens b, such as 3×3 to 7×7, specifically 5×5. The post-array aperture 3 serves to limit the light beam and eliminate stray light.

[0029] The front stacked lens array 1 is offset by ±Δ1 relative to the optical axis in the radial direction, and the rear aperture 3 is offset by ±Δ2 in the direction opposite to the offset direction of the front stacked lens array 1 to meet the following requirements:

[0030] Δ 1 =f 1 tan(fov)

[0031] Δ 2 =f 2 tan(fov)

[0032] Where: f 1 is the focal length of sub-lens a, f 2 is the focal length of sub-lens b, and fov is the field of view of the long-range infrared detection system.

[0033] The subsequent lens group 4 is composed of a front lens 9 and a rear lens 10. Figure 1 , Figure 4As shown, the material of the front lens 9 is silicon, and the material of the rear lens 10 is germanium. The front lens 9 and the rear lens 10, as a combination of positive and negative lenses, can play an achromatic effect.

[0034] Half height h of the rear stacked lens array 2 2 Determined by the following formula:

[0035] h 2 =(f 1 +f 2 )·tan(Ifov1)

[0036] Where: f 1 is the focal length of sub-lens a, f 2 is the focal length of sub-lens b, such as Figure 3 As shown, Ifov1 is the instantaneous field of view of the front stacked lens array 1 (that is, the instantaneous field of view of the long-range infrared detection system).

[0037] A specific example of the long-distance infrared detection system with full pupil filling rate and stacked array structure of the present invention is given in the following table. The working wavelength of this example is 3.7 μm to 4.8 μm.

[0038]

[0039] The imaging data for this example is given in the table below.

[0040]

[0041]

[0042] When the field of view of the example is 3.5°, high-quality imaging can still be obtained. Figure 7 to Figure 10 As shown in the figure, Δ1 and Δ2 change with the change of FOV, and the instantaneous field of view angle remains unchanged, equal to ±0.34°, as shown in the figure. Fig. 9 , Fig.10 As shown in the figure, despite this, since the detection distance is as long as 8 to 10 km, when the FOV is a certain angle, the detection range is large enough. It can be used for searching and identifying infrared targets in the civilian field.

Claims

1. A long-range infrared detection system with full pupil filling rate and stacked array structure, characterized in that: From the incident direction to the exit direction of the imaging infrared light, the front stacked lens array (1), the rear stacked lens array (2), the rear aperture (3), and the subsequent lens group (4) are arranged in sequence on the same optical axis; the front stacked lens array (1) and the rear stacked lens array (2) are each composed of n×n sub-lenses a and sub-lenses b stacked in layers; the cross sections of the sub-lenses a and the sub-lens b are both square, the sub-lens a and the sub-lens b are both positive focal length meniscus thick lenses, the curvature radii of the incident mirror surface and the exit mirror surface of the sub-lens a are both positive values, and the incident mirror surface and the exit mirror surface of the sub-lens b are both positive values. The curvature radius of the incident mirror surface is a negative value; the rear aperture (3) is composed of n×n sub-apertures c; the front stacked lens array (1) and the rear stacked lens array (2) constitute a lens array group, the entrance pupil (5) of the lens array group is located at the incident mirror surface of the front stacked lens array (1), and the exit pupil (6) of the lens array group overlaps with the position of the rear aperture (3); the front stacked lens array (1) can be shifted by ±Δ1 relative to the optical axis in the radial direction, and the rear aperture (3) is simultaneously shifted by ±Δ2 in the direction opposite to the shift direction of the front stacked lens array (1).

2. The long-range infrared detection system with full pupil filling rate and stacked array structure according to claim 1, characterized in that: The value of n×n is 3×3 to 7×7.

3. The long-range infrared detection system with full pupil filling rate and stacked array structure according to claim 1, characterized in that: The material of sub-lens a and sub-lens b are both germanium.

4. The long-range infrared detection system with full pupil filling rate and stacked array structure according to claim 1, characterized in that: The front stacked lens array (1) is offset by ±Δ1 relative to the optical axis in the radial direction, and the rear aperture 4 is offset by ±Δ2 in the direction opposite to the offset direction of the front stacked lens array (1), satisfying the following requirements: Δ1=f1·tan(fov), Δ2=f2·tan(fov), Where: f1 is the focal length of sub-lens a, f2 is the focal length of sub-lens b, and fov is the field of view of the long-range infrared detection system.

5. The long-range infrared detection system with full pupil filling rate and stacked array structure according to claim 1, characterized in that: The subsequent lens group (4) consists of a front lens (9) and a rear lens (10); the material of the front lens (9) is silicon, and the material of the rear lens (10) is germanium.

6. The long-range infrared detection system with full pupil filling rate and stacked array structure according to claim 1, characterized in that: The half height h2 of the rear stacked lens array (2) is determined by the following formula: h2=(f1+f2)·tan(Ifov1), Wherein: f1 is the focal length of sub-lens a, f2 is the focal length of sub-lens b, Ifov1 is the instantaneous field of view of the front stacked lens array (1).

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