Medium-wave infrared compound eye imaging system with completely overlapped view fields

Abstract

The invention relates to a compound eye imaging system, in particular to a medium-wave infrared compound eye imaging system with completely overlapped view fields, and aims to overcome the defect that an existing medium-wave infrared multi-detector is difficult to meet stereoscopic measurement of a fast moving target. The medium-wave infrared compound eye imaging system comprises a compound eye lens, an optical relay image transfer subsystem and a medium-wave infrared detector which are sequentially arranged from an object space to an image space along an optical axis, the fly-eye lens is used for receiving light of a target object and primarily imaging to form a primary image plane, and comprises a lens array consisting of M * N small eyes with the same optical parameters, M is greater than or equal to 2, and N is greater than or equal to 2; the optical relay image transfer subsystem is used for receiving light passing through a primary image surface and imaging the light on a target surface of the medium-wave infrared detector, the medium-wave infrared detector is used for secondary imaging, and three-dimensional measurement can be realized only by arranging one medium-wave infrared detector.

Description

Technical Field

[0001] The present invention relates to a compound eye imaging system, and particularly to a mid-wave infrared compound eye imaging system with completely overlapping fields of view. Background Art

[0002] Traditional mid-wave infrared optical systems usually adopt a single-aperture lens design, which has significant limitations in complex scene applications. First, there is an inherent contradiction between the field of view angle and resolution of a single-aperture lens, making it difficult to meet the requirements of both a large field of view and high resolution simultaneously. Second, a single-aperture lens has limited capabilities in three-dimensional detection and multi-dimensional information perception, and cannot achieve high-precision depth information extraction and target three-dimensional reconstruction. In addition, a single-aperture lens has poor adaptability to dynamic scenes and is difficult to cope with rapidly changing optical environments.

[0003] Existing mid-wave infrared imaging systems are mostly set in the form of a camera array to achieve three-dimensional measurement, forming a mid-wave infrared multi-detector. In the three-dimensional measurement of fast-moving targets, it is difficult for the mid-wave infrared multi-detector to achieve high synchronization of data acquisition, and complex three-dimensional calibration is required. Summary of the Invention

[0004] The object of the present invention is to solve the deficiencies of existing mid-wave infrared multi-detectors that are difficult to meet the three-dimensional measurement of fast-moving targets, and to provide a mid-wave infrared compound eye imaging system with completely overlapping fields of view.

[0005] The inventive concept of the present invention: To overcome the limitations of mid-wave infrared multi-detectors, the mid-wave infrared compound eye technology of the present invention emerges as the times require. By simulating the multi-aperture structure of insect compound eyes and adopting an array optical system, the present invention realizes the synchronous optimization of a large field of view and high resolution. In addition, the compound eye technology also has high dynamic range and fast response characteristics, and can adapt to complex and changeable mid-wave infrared detection scenarios. In the mid-wave infrared compound eye imaging system with completely overlapping fields of view of the present invention, each ommatidium independently images, and global information is obtained by using an image reconstruction algorithm, significantly improving the three-dimensional detection ability of the system. Only one mid-wave infrared detector is set to achieve the three-dimensional measurement of the target, there is no problem of asynchronous image acquisition, and no three-dimensional calibration step is required. Only the compound eye camera needs to be calibrated to achieve the three-dimensional measurement of the target.

[0006] To achieve the above object and inventive concept, the technical solution provided by the present invention is as follows: A mid-wave infrared compound eye imaging system with completely overlapping fields of view, characterized in that it includes a compound eye lens, an optical relay image rotation subsystem, and a mid-wave infrared detector arranged in sequence from the object side to the image side along the optical axis; the compound eye lens is used to receive the light of the target object and form a primary image to form a primary image plane, and includes a lens array composed of M×N small eyes with the same optical parameters, where M≥2 and N≥2; the lens array matches the shape of the target surface of the mid-wave infrared detector; the M×N small eyes are located on the same plane, and the included angle between the optical axes of adjacent small eyes is 0°; the optical relay image rotation subsystem is used to receive the light passing through the primary image plane and image it on the target surface of the mid-wave infrared detector; the mid-wave infrared detector is used for secondary imaging.

[0007] Further, the optical relay image rotation subsystem includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence from the object side to the image side along the optical axis, and the fifth lens is arranged close to the detection end of the mid-wave infrared detector; The optical powers of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are positive, negative, positive, positive, and negative respectively; The convex surfaces of the first lens and the fifth lens face the object side, and the convex surfaces of the second lens, the third lens, and the fourth lens face the image side.

[0008] Further, the first lens is a spherical lens, with a central thickness of 6.8 mm, a front surface curvature radius of 113.6 mm, and a rear surface curvature radius of 380.2 mm; The second lens is an aspherical lens, with a central thickness of 4.5 mm, a front surface curvature radius of -19.88 mm, and a rear surface curvature radius of -89.33 mm; The third lens is a spherical lens, with a central thickness of 5 mm, a front surface curvature radius of -63.417 mm, and a rear surface curvature radius of -30.2 mm; The fourth lens is a spherical lens, with a central thickness of 5 mm, a front surface curvature radius of -89.95 mm, and a rear surface curvature radius of -36.48 mm; The fifth lens is a spherical lens, with a central thickness of 4 mm, a front surface curvature radius of 128.23 mm, and a rear surface curvature radius of 105.44 mm.

[0009] Further, the expression of the aspherical surface of the second lens is:

[0010] where z is the height of the aspherical surface along the optical axis direction, c is the curvature, r is the curvature radius, k is the conic constant, and A, B, C, and D are all aspherical coefficients, A = 0.18×10 -4 ,B = 3.12×10 -9, C = D = 0.

[0011] Further, the axial distance between the first lens and the second lens is 43.0 mm, the axial distance between the second lens and the third lens is 1.7 mm, the axial distance between the third lens and the fourth lens is 6.2 mm, the axial distance between the fourth lens and the fifth lens is 7.5 mm, and the axial distance between the fifth lens and the target surface of the mid-wave infrared detector is 28.6 mm.

[0012] Further, the second lens and the fifth lens are made of germanium material, and the first lens, the third lens, and the fourth lens are all made of silicon material.

[0013] Further, it is defined that the center distance between adjacent ommatidia along the short side direction of the lens array is the first distance X, and the center distance between adjacent ommatidia along the long side direction of the lens array is the second distance Y. Then, the first distance X and the second distance Y satisfy: Y = 1.2X to 1.3X; The ommatidia are set as rectangular lenses and are spherical lenses, and the lens parameters of each ommatidium are the same; The ommatidia are made of silicon material.

[0014] Further, it further includes a sealed housing. The sealed housing includes a first housing and a second housing connected in sequence. The compound eye lens and the optical relay image rotation subsystem are respectively arranged in the first housing and the second housing. One end of the second housing away from the first housing is connected to the mid-wave infrared detector; The compound eye lens further includes a mounting bracket for mounting the lens array. The mounting bracket includes a planar aperture array perpendicular to the optical axis. The planar aperture array is composed of M × N rectangular frames, and M × N ommatidia are respectively arranged in the M × N rectangular frames.

[0015] Further, the rectangular frames are made of metal material; the sealed housing is made of aluminum material; The mid-wave infrared detector is a cooled mid-wave infrared detector. The detection end of the cooled mid-wave infrared detector is sequentially provided with a filter and a cold stop. Among them, the cold stop is located at a position away from the optical relay image rotation subsystem, and an aperture stop is arranged on the side close to the filter, and the aperture stop matches the cold stop.

[0016] Further, M = 3, N = 3, Y = 1.25X; It is defined that the center coordinates of the ommatidium at the center of the lens array are (0, 0), and the center coordinates of the remaining ommatidia are respectively (11, 0), (11, -13), (0, -13), (-11, -13), (-11, 0), (-11, 13), (0, 13), (11, 13), unit: mm.

[0017] Advantages of the present invention: 1. In the compound eye lens of the present invention, the ommatidia with the same optical parameters are arranged in an M×N array to form a lens array on the same plane. The included angle between the optical axes of adjacent ommatidia is 0°, realizing complete overlap of the fields of view. Thus, only one mid-wave infrared detector is needed to achieve three-dimensional measurement. At the same time, the present invention sets up an optical relay image rotation subsystem, which greatly reduces the aperture of the compound eye lens, adapts the imaging of the relatively large lens array to the mid-wave infrared detector, has high applicability, and realizes large-field imaging under the condition of limited size of the mid-wave infrared detector.

[0018] 2. In the present invention, the field of view is divided by multiple ommatidia, reducing imaging distortion. In addition, the optical relay image rotation subsystem introduces aspherical lenses and adopts a combination of various infrared optical materials, reducing system aberration and effectively reducing the cold reflection phenomenon, improving the imaging quality of the mid-wave infrared compound eye imaging system.

[0019] 3. The ommatidia of the present invention are set as rectangular lenses according to the target surface shape of the mid-wave infrared detector and are arranged in an array. The first spacing X and the second spacing Y between adjacent ommatidia satisfy Y = 1.2X~1.3X, increasing the area ratio of the ommatidia in the lens array, greatly improving the filling ratio of the sub-images corresponding to each ommatidia during secondary imaging, and at the same time avoiding the coincidence and blurring of the edges of adjacent sub-images.

[0020] 4. Multiple rectangular lenses in the present invention have exactly the same optical parameters, can be processed in batches, are easy to replace, facilitate quick installation and disassembly, and can reduce the installation and use costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the optical path structure of an embodiment of the present invention; Figure 2 is a schematic diagram of the structure of the lens array in an embodiment of the present invention; Figure 3 is a transfer function diagram of the ommatidium numbered 1 in an embodiment of the present invention; Figure 4 is a spot diagram of the ommatidium numbered 1 in an embodiment of the present invention; Figure 5 is a distortion diagram of the ommatidium numbered 1 in an embodiment of the present invention; Figure 6 is a transfer function diagram of the ommatidium numbered 2 in an embodiment of the present invention; Figure 7 is a spot diagram of the ommatidium numbered 2 in an embodiment of the present invention; Figure 8 is a distortion diagram of the ommatidium numbered 2 in an embodiment of the present invention; Figure 9 is a transfer function diagram of the ommatidium numbered 4 in an embodiment of the present invention; Figure 10 This is the spot diagram of the ommatidium numbered 4 in the embodiment of the present invention; Figure 11 This is the distortion diagram of the ommatidium numbered 4 in the embodiment of the present invention; Figure 12 This is the transfer function diagram of the ommatidium numbered 9 in the embodiment of the present invention; Figure 13 This is the spot diagram of the ommatidium numbered 9 in the embodiment of the present invention; Figure 14 This is the distortion diagram of the ommatidium numbered 9 in the embodiment of the present invention.

[0022] Explanation of reference numerals: 01 - Compound eye lens, 02 - Optical relay image rotation subsystem, 10 - First lens, 11 - Second lens, 12 - Third lens, 13 - Fourth lens, 14 - Fifth lens, 20 - Aperture stop, 21 - Cold stop, 22 - Filter. Detailed implementation manners

[0023] A mid-wave infrared compound eye imaging system with completely overlapping fields of view according to the present invention includes a compound eye lens 01, an optical relay image rotation subsystem 02, and a mid-wave infrared detector arranged in sequence along the optical axis from the object side to the image side, as Figure 1 shown.

[0024] The compound eye lens 01 is used to receive the light of the target object and perform a preliminary imaging at the position of the primary image plane, and the primary image plane is located between the compound eye lens 01 and the optical relay image rotation subsystem 02. The compound eye lens 01 is composed of a mounting bracket and a lens array. The lens array is composed of M×N ommatidia with the same optical parameters and located in the same plane, where M≥2, N≥2, and the included angle between the optical axes of adjacent ommatidia is 0°, realizing completely overlapping fields of view. In this embodiment, a total of 9 ommatidia are provided and arranged in a 3×3 array. The 9 ommatidia are all silicon material lenses with positive optical power, and the surface types are all spherical surfaces.

[0025] The lens array is matched with the shape of the target surface of the mid-wave infrared detector and is set as a rectangular array. It is defined that the center distance between adjacent ommatidia along the short side direction of the lens array is the first distance X, and the center distance between adjacent ommatidia along the long side direction of the lens array is the second distance Y. Then, the first distance X and the second distance Y satisfy: Y = 1.2X~1.3X In this embodiment, Y = 1.25X, and the ommatidia are set as rectangular lenses. The filling ratio of the sub-images is improved through the cooperation of the first distance and the second distance. The mounting bracket includes a planar aperture array, and the planar aperture array is composed of rectangular frames arranged perpendicular to the optical axis and in a 3×3 array. The ommatidia are installed in the corresponding rectangular frames and fixed by retaining rings.

[0026] The optical relay image rotation subsystem 02 includes a first lens 10, a second lens 11, a third lens 12, a fourth lens 13, and a fifth lens 14 that are sequentially arranged from the object side to the image side along the optical axis. The fifth lens 14 is arranged close to the detection end of the mid-wave infrared detector and corresponds to the target surface of the mid-wave infrared detector. It is used to receive the light passing through the primary image plane and image it on the target surface of the mid-wave infrared detector. The mid-wave infrared detector performs a secondary imaging on it to form sub-images corresponding to each ommatidium. In this embodiment, a cooled mid-wave infrared detector is used. A filter 22 and a cold stop 21 are arranged at the detection end of the cooled mid-wave infrared detector. The cold stop 21 is arranged far from the fifth lens 14, and an aperture stop 20 is arranged on the side close to the fifth lens 14. The aperture stop 20 matches the cold stop 21, that is, the aperture of the aperture stop 20 needs to be consistent with that of the cold stop 21 and their positions coincide. Through the optical design of the optical relay image rotation subsystem 02 matching with the cold stop 21, the efficiency of the cold stop 21 reaches 100%. At the same time, the stray light generated by the lens barrel and other thermal backgrounds is completely blocked from entering the mid-wave infrared detector, significantly improving the signal-to-noise ratio of the output image and ensuring the final imaging quality.

[0027] The first lens 10 is a spherical silicon lens with positive optical power and a convex surface facing the object side. The second lens 11 is an aspherical germanium lens with negative optical power and a convex surface facing the image side. The third lens 12 is a spherical silicon lens with positive optical power and a convex surface facing the image side. The fourth lens 13 is a spherical silicon lens with positive optical power and a convex surface facing the image side. The fifth lens 14 is a spherical germanium lens with negative optical power and a convex surface facing the object side. The specific parameters are shown in the following table:

[0028] The aspherical surface of the second lens 11 corresponds to the following expression:

[0029] where z is the height of the aspherical surface along the optical axis direction, c is the curvature, r is the radius of curvature, k is the conic constant, and A, B, C, and D are all aspherical coefficients. A = 0.18×10 -4 and B = 3.12×10 -9 and C = D = 0.

[0030] The axial distance between the first lens 10 and the second lens 11 is 43.0 mm. The axial distance between the second lens 11 and the third lens 12 is 1.7 mm. The axial distance between the third lens 12 and the fourth lens 13 is 6.2 mm. The axial distance between the fourth lens 13 and the fifth lens 14 is 7.5 mm. The axial distance between the fifth lens 14 and the target surface of the mid-wave infrared detector is 28.6 mm.

[0031] In this embodiment, the system aperture is set to F / 4, the working wavelength band is 3 - 5 μm, the focal length is 11 mm, and the field - of - view overlap rate of the nine ommatidia is 100%. Taking the ommatidium at the center of the lens array as a reference, it is defined that the center coordinates of the ommatidium are (0, 0), and this coordinate is also the center position of the compound - eye lens 01. Then the center coordinates of the remaining ommatidia are (11, 0), (11, - 13), (0, - 13), (-11, - 13), (-11, 0), (-11, 13), (0, 13), (11, 13) respectively. As Figure 2 shown, starting from the ommatidium at the center of the lens array, the nine ommatidia are sequentially numbered counter - clockwise, Figures 3 to 14 which are the imaging - quality diagrams of the ommatidia numbered 1, 2, 4, and 9 respectively. The imaging - quality diagram includes the transfer - function diagram, the spot - diagram, and the distortion diagram. Since there are nine channels in the mid - wave infrared compound - eye imaging system of the present invention, the imaging quality of the ommatidium numbered 1 at the center, the ommatidium numbered 9 on the diagonal, and the ommatidia numbered 2 and 4 at the center positions on the sides can be used to characterize the imaging effect of the overall optical system. The transfer - function diagram can comprehensively describe the imaging quality of the mid - wave infrared compound - eye imaging system. The spot - diagram can intuitively reflect the aberration of the system, and the distortion diagram can represent the distortion of the image. It can be seen from the transfer - function diagram that when the spatial frequency is 33 lp / mm (cycles / mm), the modulation transfer functions (MTFs) of the ommatidia numbered 1, 2, 4, and 9 are all close to the diffraction limit, and the spot diagrams are all within the Airy - disk range. Therefore, the present invention has a high imaging quality and fully meets the requirements for detecting multi - dimensional information in the object - space scene. In addition, it can be seen from the distortion diagram that the distortion of the optical system in this embodiment is less than 1.1%, indicating that the image distortion of the present invention is low, and it can realize the detection, recognition, and tracking of infrared targets.

[0032] To achieve integrated assembly, the present invention also provides a sealed housing made of all - hard aluminum. The sealed housing includes a first housing and a second housing that are sequentially connected by a flange. The compound - eye lens 01 and the optical relay image - rotation subsystem 02 are respectively arranged in the first housing and the second housing. One end of the second housing away from the first housing is connected to the mid - wave infrared detector to realize integrated alignment and adjustment with adjustable spatial dimensions. In addition, the present invention uses high - precision centering assembly to ensure a concentricity of 0.01 mm, performs black anodizing treatment and sand - blasting treatment on the surface of the sealed housing, and designs anti - stray - light threads and other measures to achieve the anti - stray - light effect.

Claims

1. A medium-wave infrared compound eye imaging system with completely overlapping fields of view, characterized in that: It comprises a compound eye lens (01), an optical relay image transfer subsystem (02) and a medium-wave infrared detector which are arranged in sequence from the object side to the image side along the optical axis; The compound eye lens (01) is used to receive target light and perform preliminary imaging to form a primary image plane, comprising a lens array composed of M×N ommatidia with the same optical parameters, wherein M≥2 and N≥2; the lens array matches the target surface shape of the medium-wave infrared detector; the M×N ommatidia are located in the same plane, and the angle between the optical axes of adjacent ommatidia is 0°; The optical relay image transfer subsystem (02) is used to receive light passing through the primary image plane and image it on the target surface of the medium-wave infrared detector; The medium-wave infrared detector is used for secondary imaging.

2. According to claim 1, a medium-wave infrared compound eye imaging system with completely overlapping fields of view is characterized in that: The optical relay image transfer subsystem (02) comprises a first lens (10), a second lens (11), a third lens (12), a fourth lens (13), and a fifth lens (14) which are arranged in sequence from the object side to the image side along the optical axis, and the fifth lens (14) is arranged close to the detection end of the medium-wave infrared detector; The optical powers of the first lens (10), the second lens (11), the third lens (12), the fourth lens (13), and the fifth lens (14) are respectively positive, negative, positive, positive, and negative; The convex surfaces of the first lens (10) and the fifth lens (14) face the object side, and the convex surfaces of the second lens (11), the third lens (12) and the fourth lens (13) face the image side.

3. The medium-wave infrared compound eye imaging system with completely overlapping fields of view according to claim 2, characterized in that: The first lens (10) is a spherical lens with a center thickness of 6.8 mm, a front surface curvature radius of 113.6 mm, and a rear surface curvature radius of 380.2 mm; The second lens (11) is an aspherical lens with a center thickness of 4.5 mm, a front surface curvature radius of -19.88 mm, and a rear surface curvature radius of -89.33 mm; The third lens (12) is a spherical lens with a center thickness of 5 mm, a front surface curvature radius of -63.417 mm, and a rear surface curvature radius of -30.2 mm; The fourth lens (13) is a spherical lens with a center thickness of 5 mm, a front surface curvature radius of -89.95 mm, and a rear surface curvature radius of -36.48 mm; The fifth lens (14) is a spherical lens with a center thickness of 4 mm, a front surface curvature radius of 128.23 mm, and a rear surface curvature radius of 105.44 mm.

4. According to claim 3, a medium-wave infrared compound eye imaging system with completely overlapping fields of view is characterized in that: The expression of the aspheric surface of the second lens (11) is: ； Where z is the height of the aspheric surface along the optical axis, c is the curvature, r is the radius of curvature, k is the cone constant, A, B, C, and D are all aspheric coefficients, A=0.18×10 -4 , B=3.12×10 -9 , C=D=0.

5. The medium-wave infrared compound eye imaging system with completely overlapping fields of view according to claim 4, characterized in that: The axial spacing between the first lens (10) and the second lens (11) is 43.0 mm, the axial spacing between the second lens (11) and the third lens (12) is 1.7 mm, the axial spacing between the third lens (12) and the fourth lens (13) is 6.2 mm, the axial spacing between the fourth lens (13) and the fifth lens (14) is 7.5 mm, and the axial spacing between the fifth lens (14) and the target surface of the medium-wave infrared detector is 28.6 mm.

6. The medium-wave infrared compound eye imaging system with completely overlapping fields of view according to claim 5, characterized in that: The second lens (11) and the fifth lens (14) are made of germanium material, and the first lens (10), the third lens (12) and the fourth lens (13) are all made of silicon material.

7. A medium-wave infrared compound eye imaging system with completely overlapping fields of view according to any one of claims 1 to 6, characterized in that: Define that the center spacing of adjacent ommatidia along the short side of the lens array is the first spacing X, and the center spacing of adjacent ommatidia along the long side of the lens array is the second spacing Y. Then the first spacing X and the second spacing Y satisfy: Y=1.2X~1.3X; The ommatidia are configured as rectangular lenses and spherical lenses, and the lens parameters of each ommatidia are the same; The small eyes are made of silicon material.

8. The medium-wave infrared compound eye imaging system with completely overlapping fields of view according to claim 7, characterized in that: It also includes a sealed housing, the sealed housing including a first housing and a second housing connected in sequence, the compound eye lens (01) and the optical relay image transfer subsystem (02) are respectively arranged in the first housing and the second housing, and one end of the second housing away from the first housing is connected to the medium-wave infrared detector; The compound eye lens (01) further comprises a mounting bracket for mounting the lens array, the mounting bracket comprising a planar aperture array arranged perpendicular to the optical axis, the planar aperture array consisting of M×N rectangular frames, and the M×N ommatidia arranged in the M×N rectangular frames in a one-to-one correspondence.

9. The medium-wave infrared compound eye imaging system with completely overlapping fields of view according to claim 8, characterized in that: The rectangular frame is made of metal; the sealed housing is made of aluminum; The medium-wave infrared detector adopts a refrigerated medium-wave infrared detector, and a filter (22) and a cold diaphragm (21) are sequentially arranged at the detection end of the refrigerated medium-wave infrared detector, wherein the cold diaphragm (21) is located away from the optical relay image transfer subsystem (02), and an aperture diaphragm (20) is arranged on a side close to the filter (22), and the aperture diaphragm (20) matches the cold diaphragm (21).

10. The medium-wave infrared compound eye imaging system with completely overlapping fields of view according to claim 9, characterized in that: M=3, N=3, Y=1.25X; It is defined that the center coordinate of the ommatidium located at the center of the lens array is (0, 0), and the center coordinates of the remaining ommatidium are (11, 0), (11, -13), (0, -13), (-11, -13), (-11, 0), (-11, 13), (0, 13), (11, 13), respectively, unit: mm.

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