Long-range infrared detection system with full entrance pupil fill and stacked array architecture

Abstract

The long-distance infrared detection system with full entrance pupil fill factor and laminated array structure belongs to the field of optical detection technology. The prior art has complex structure and weak receiving light intensity. From the direction of incident infrared light to the direction of outgoing light, the front laminated lens array, the rear laminated lens array, the array rear stop and the rear lens group are arranged along the optical axis in sequence; the front laminated lens array and the rear laminated lens array are each composed of n*n sub-lenses a and sub-lenses b which are laminated; the cross sections of the sub-lenses a and the sub-lenses b are all 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 overlaps with the position of the array rear stop; the front laminated lens array can be radially misaligned with the optical axis by ±Δ1, and the array rear stop is misaligned in the direction opposite to the misalignment direction of the front laminated lens array by ±Δ2. The present application can be used for searching and identifying infrared targets in the civil field.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optical detection technology. BACKGROUND

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

[0003] In the prior art, the infrared detection system applied to long-distance target detection has the following two kinds:

[0004] One is a scheme disclosed in a Chinese utility model patent with the application number 201820201750.9 and the name "ultra-long-distance passive infrared detection system and ship navigation avoidance early warning system", which constitutes each component part of the scheme, including optical elements such as narrow-band interference filter lens and hemispherical Fresnel lens; photoelectric elements such as infrared detector; electrical elements such as post-amplifier; and precision mechanical parts such as a cloud platform. In the scheme, multiple infrared receiving units are combined into an array, and a Fresnel lens is used in each infrared receiving unit, and multiple infrared detectors are inlaid on the end face of each lens; the narrow-band interference filter lens is arranged parallel to the total mounting plate, and the distance between them is 20-25 cm. The detection distance of the scheme reaches 150-200 km for air targets and 40-50 km for sea surface targets; the detection direction reaches 360°. The scheme is applied to the field of military detection, can receive the beam of an ultra-long-distance infrared target, realizes the detection of an ultra-long-distance invisible target, and becomes a military detection system with high concealment. However, it can be seen that the scheme has its shortcomings, such as complex structure, high manufacturing cost, loose structure, large volume, and insufficient received light energy.

[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. During the operation in the small field of view mode, the field mirror group in the telescope assembly moves out of the optical path, and the infrared light from the target enters the objective lens and directly illuminates the focusing lens. The light energy is not lost 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 mirror group with large movements. In the scanning working mode, the scanning mirror assembly needs to swing at high frequency. These make the solution have many mechanical movements and large movements, which limits the application of this solution. Summary of the Invention

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

[0007] The long-range 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 meniscus thick lenses with positive focal power. The curvature radius of the incident mirror surface and the exit mirror surface of sub-lens a are both positive, and the curvature radius 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 FIG. 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, as shown 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-range 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 is finally converged 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 offset by Δ1 relative to the optical axis in the radial direction, such as 1.39 mm, and the rear aperture 3 is offset by Δ2 in the direction opposite to the offset direction of the front stacked lens array 1, such as 0.753 mm. 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 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 significant loss after propagating through the atmosphere over a long distance (e.g., 8km to 10km), the imaging infrared light received by the long-distance infrared detection system of the present invention still has a light intensity capable of 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 clipping 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 achieving 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 existing technology, 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 existing technology, the present invention simplifies the operation 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 This is a schematic diagram of the overall structure and imaging process of the present invention. In the figure, the imaging infrared light is parallel to the incident front stacked lens array.

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

[0018] Figure 4 This 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 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 of the stacked lens array failing to achieve full pupil filling rate when imaging infrared light is incident at a certain field of view angle.

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

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

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

[0024] Figure 10 This 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, as shown in FIG. Figure 2 、 Figure 3 as well as Figure 1 As shown in the figure, the value of n×n ranges from 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 with only a small number of array units, which is beneficial to the installation and adjustment of the long-range infrared detection system.

[0027] The materials 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] Δ1=f1·tan(fov)

[0031] Δ2=f2·tan(fov)

[0032] 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.

[0033] The subsequent lens group 4 is composed of a front lens 9 and a rear lens 10. Figure 1 、 Figure 4 As 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 are a combination of positive and negative lenses, which can achieve achromatic effect.

[0034] The half height h2 of the rear stacked lens array 2 is determined by the following formula:

[0035] h2=(f1+f2)·tan(Ifov1)

[0036] Where: f1 is the focal length of sub-lens a, f2 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-range infrared detection system with a full pupil filling rate and a stacked array structure of the present invention is given in the table below. The operating 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 angle of the embodiment is 3.5°, high-quality imaging can still be obtained, such as Figures 7 to 10 As shown in Figure 2, 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 Figure 2. Figure 9 、 Figure 10 As shown in the figure, despite this, the detection range is as long as 8 to 10 km, and when the FOV is a certain angle, the detection range is large enough to be used for searching and identifying infrared targets in the civilian field.

Claims

1. A long-range infrared detection system with full pupil fill rate and stacked array structure, characterized in that: The detection system is composed of a front stacked lens array (1), a rear stacked lens array (2), a rear aperture (3), and a subsequent lens group (4), which are arranged in sequence along the optical axis from the incident direction to the exit direction of the imaging infrared light; 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; the cross sections of the sub-lenses a and sub-lenses b are both square, the sub-lenses a and sub-lenses 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, and the incident mirror surface of the sub-lens b is The curvature radii of the mirror surface and the exit mirror surface are both negative values; 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) can be shifted by ±Δ2 in the direction opposite to the shift direction of the front stacked lens array (1); The value of n×n ranges from 3×3 to 7×7; Sub-lens a and sub-lens b are both made of germanium; 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; The subsequent lens group (4) is composed 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; The half height h2 of the rear stacked lens array (2) is determined by the following formula: h2=(f1+f2)·tan(Ifov1), Where: 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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