A Fourier stack remote sensing high-resolution imaging system and imaging method

Abstract

The application provides a Fourier superposition remote sensing high-resolution imaging system and an imaging method, and is used for solving the technical problems that the optical path of an existing analog Fourier superposition remote sensing imaging system is relatively complex, the adjustment difficulty increases with the increase of the working distance of a target, or the illumination optical path part of an actual remote sensing imaging target cannot meet the actual situation. The Fourier superposition remote sensing high-resolution imaging system of the application adopts a fiber collimator and a beam expander to form parallel light of a laser light source. The parallel light obtained in this way is no longer shaped and constrained, which not only greatly simplifies the illumination system, but also can better simulate the actual illumination condition of the remote sensing imaging target. Meanwhile, a 4f-like imaging system is used to receive the reflection information of the remote sensing imaging target. Whether in the case of limited laboratory work or in the real field experiment condition meeting the far-field diffraction condition, the imaging can be realized only through simple adjustment.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging, and particularly relates to a Fourier stacked remote sensing high-resolution imaging system and imaging method for achieving high-resolution imaging of distant targets. Background Technology

[0002] High-precision, high-resolution imaging is the main direction for future Earth imaging, optical situational awareness, early warning and space target imaging. In spaceborne optical imaging systems, the traditional method to improve the resolution of imaging targets is to expand the aperture of the receiving optical system by using techniques such as unfoldable splicing and modular assembly of optical synthetic apertures. However, considering the quality, volume and processing and assembly difficulty of the optical system, as well as the requirements for phase matching accuracy, it is not possible to simply increase the aperture of the receiving optical system.

[0003] Fourier layered imaging technology has expanded from millimeter-level working distances in optical microscopy to meter-level working distances. Furthermore, with the increasing distance of laser illumination, the continuous growth of optical apertures, and the application of more sensitive cameras, it is possible to extend this technology to detection ranges of tens or even hundreds of kilometers. This technology can revolutionize traditional synthetic aperture techniques, providing important research ideas for exploring novel, large-field-of-view, high-performance, and low-cost active coherent synthetic aperture long-range imaging technologies.

[0004] However, based on existing simulated Fourier stacked remote sensing imaging systems, the optical systems are mainly divided into two experimental systems to meet laboratory imaging requirements: one is to shape the light source at the emission end to satisfy far-field Fraunhofer diffraction, constrain the spectrum at the image plane position of the light source, i.e., the spectral position of the object, and then receive the image through the imaging optical lens and detector; the other is to use a collimator to simulate the parallel beam of remote sensing imaging, with the target located in front of the collimator, and the target's spectrum received and constrained at the rear end of the collimator, and then received and imaged through the imaging lens and detector. While the two imaging systems mentioned above can basically meet the requirements of far-field Fourier stacked far-field diffraction imaging, the first method, regardless of whether it is light source scanning or detector scanning, has a relatively complex optical path, and the difficulty of adjustment increases as the target working distance increases. The collimator in the second method can simulate a parallel optical path well, but under actual conditions, when the laser actively images the remote sensing target, the spherical wave emitted by the laser expands into a plane wave after long-distance transmission and is received by the detector, but it is not a plane wave in the strict sense. Therefore, the collimator simulates a remote sensing target at a distance, which is a more ideal situation. The actual situation is more complex, and the illumination optical path for the actual remote sensing imaging target still cannot better meet the actual situation. Summary of the Invention

[0005] The purpose of this invention is to address the technical problems of existing analog Fourier stacked remote sensing imaging systems, such as complex optical paths, increasing adjustment difficulty with the target's working distance, or the inability of the illumination optical path to meet the actual needs of remote sensing imaging targets. This invention proposes a Fourier stacked remote sensing high-resolution imaging system and imaging method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A Fourier stacked remote sensing high-resolution imaging system, characterized in that it includes a Fourier stacked remote sensing imaging system and a host computer.

[0008] The Fourier stacked remote sensing imaging system includes an active illumination system and an imaging receiving system;

[0009] The active illumination system includes a fiber laser, a two-dimensional moving platform, and a fiber collimator and a beam expander mounted on the two-dimensional moving platform.

[0010] The fiber collimator and beam expander are located sequentially in the laser output path of the fiber laser, and are used to collimate and expand the output laser of the fiber laser in sequence to form parallel light.

[0011] The two-dimensional moving platform is used to move the fiber collimator and beam expander in the horizontal and vertical directions.

[0012] The remote sensing imaging target is located on the parallel light path after passing through the beam expander, which is used to reflect the parallel light to form the target reflected light;

[0013] The fiber optic head of the fiber laser is fixed on the fiber collimator, which is used to make the fiber optic head of the fiber laser follow the movement of the fiber collimator, so as to illuminate the remote sensing imaging target at different angles in a line-by-line scanning manner.

[0014] The imaging receiving system includes a front-facing lens, an imaging lens, and an imaging detector, which are sequentially located on the optical path of the reflected light from the target.

[0015] The front-facing lens is positioned on the object side of the imaging lens, and the rear focal plane of the front-facing lens coincides with the shortest imaging position of the imaging lens, so that the front-facing lens and the imaging lens constitute a 4f-like imaging system. The target reflected light under illumination at different angles passes through the front-facing lens and obtains the corresponding remote sensing imaging target spectrum image at the rear focal plane of the front-facing lens, and then passes through the imaging lens to form the corresponding remote sensing imaging target low-resolution intensity image.

[0016] The imaging detector is used to detect low-resolution intensity images under illumination at different angles and convert them into electrical signals;

[0017] The input terminal of the host computer is connected to the output terminal of the imaging detector. It is used to arrange the low-resolution intensity images of the remote sensing imaging target under different illumination angles in the scanning order to form a low-resolution intensity image array, and to perform Fourier stacking high-resolution reconstruction on the low-resolution intensity image array to obtain a high-resolution image of the remote sensing imaging target.

[0018] Furthermore, the fiber laser is a continuous single-mode fiber laser.

[0019] Furthermore, the two-dimensional mobile platform is an electric mobile platform.

[0020] Furthermore, the diameter of the parallel light spot after beam expansion by the beam expander is 10 times the diameter of the beam spot after collimation by the fiber collimator.

[0021] In addition, the present invention also provides a Fourier stacked remote sensing high-resolution imaging method, which is characterized by including the following steps:

[0022] Step 1: Construct the aforementioned Fourier stacked remote sensing high-resolution imaging system;

[0023] Step 2: Control the two-dimensional moving platform to move in the horizontal and vertical directions respectively, so that the fiber laser illuminates the remote sensing imaging target at different angles in a line-by-line scanning manner; the two-dimensional moving platform maintains a fixed moving distance in each single movement in the horizontal and vertical directions to ensure that the overlap rate between each two low-resolution images is more than 50%.

[0024] Step 3: The target reflected light under different illumination angles passes through the front lens and is used to obtain the remote sensing target spectrum image at the rear focal plane of the front lens under the corresponding illumination angle. Then, it passes through the imaging lens and is used to obtain the corresponding remote sensing target low-resolution intensity image on the imaging detector.

[0025] Step 4: The host computer arranges the low-resolution intensity images of the remote sensing target under different illumination angles input by the imaging detector in the scanning order to form a low-resolution intensity image array. Then, Fourier stacking high-resolution reconstruction is performed on the low-resolution intensity image array to obtain a high-resolution image of the remote sensing target.

[0026] Furthermore, in step 2, the single movement distance of the two-dimensional mobile platform in both the horizontal and vertical directions is 10mm.

[0027] The advantages of this invention compared to the prior art are as follows:

[0028] This invention provides a Fourier stacked remote sensing high-resolution imaging system. The active illumination system uses an optical fiber collimator and beam expander to collimate and expand the laser source to form parallel light. This parallel light, without the need for shaping constraints, directly illuminates the remote sensing target, simulating active laser illumination of a remote sensing target at infinity. This not only greatly simplifies the illumination system but also better simulates target illumination in actual remote sensing imaging, meeting practical requirements. Simultaneously, a 4f-like imaging system is used to receive the reflection information of the remote sensing target, making the system simpler and easier to adjust. This method can be applied in laboratories or any working mode that does not meet Fraunhofer remote sensing long-distance imaging requirements. Furthermore, when the imaging system distance meets the Fraunhofer remote sensing long-distance imaging conditions or actual remote sensing imaging scenarios, the front lens can be directly removed to achieve imaging. Therefore, compared to existing remote sensing imaging lenses, this receiving system is simpler, more flexible, and has higher sampling efficiency. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of an embodiment of a Fourier stacked remote sensing high-resolution imaging system according to the present invention;

[0030] Figure 2 This is a schematic diagram of the imaging receiving system in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the low-resolution intensity image array formed in step 4 of an embodiment of the Fourier stacked remote sensing high-resolution imaging method of the present invention.

[0032] Figure 4 This is a comparison image of a low-resolution intensity image of a remotely sensed target obtained at the 25th angle of illumination and a reconstructed high-resolution image, as shown in an embodiment of the Fourier stacked remote sensing high-resolution imaging method of the present invention. (a) is the low-resolution intensity image of the remotely sensed target obtained at the 25th angle of illumination, and (b) is the reconstructed high-resolution image of the remotely sensed target.

[0033] The specific reference numerals in the attached figures are as follows:

[0034] 1-Host computer; 2-Fiber laser; 3-Two-dimensional moving platform; 4-Fiber collimator; 5-Beam expander; 6-Remote sensing imaging target; 7-Front-facing lens; 8-Imaging lens; 9-Imaging detector. Detailed Implementation

[0035] To make the advantages and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] like Figure 1As shown, a Fourier stacked remote sensing high-resolution imaging system includes a Fourier stacked remote sensing imaging system and a host computer 1. The Fourier stacked remote sensing imaging system includes an active illumination system and an imaging receiving system.

[0037] The active illumination system includes a fiber laser 2, a two-dimensional moving platform 3, a fiber collimator 4, and a beam expander 5. The fiber laser 2 is preferably a continuous single-mode fiber laser, used to illuminate the remote sensing imaging target 6. The fiber collimator 4 and beam expander 5 are sequentially located on the laser output path of the fiber laser 2. The fiber collimator 4 is used to collimate the output laser beam from the fiber laser 2, and the beam expander 5 is used to expand the collimated beam from the fiber collimator 4 to form parallel light. The diameter of the expanded parallel light spot is approximately 10 times the diameter of the collimated beam spot.

[0038] The two-dimensional moving platform 3 can move in both horizontal and vertical directions. The fiber collimator 4 and the beam expander 5 are fixedly mounted on the two-dimensional moving platform 3. At the same time, the fiber head of the fiber laser 2 is fixed on the fiber collimator 4. The two-dimensional moving platform 3 moves in both horizontal and vertical directions, thereby driving the fiber collimator 4 and the beam expander 5 to move accordingly, and in turn driving the fiber head of the fiber laser 2 to move accordingly.

[0039] The remote sensing imaging target 6 is typically a specular resolution target or a diffuse reflection target with certain scattering characteristics. It is located on the parallel light path after passing through the beam expander 5, used to reflect the parallel light to form the target reflected light. The fiber head of the fiber laser 2 follows the movement of the fiber collimator 4 in the horizontal and vertical directions, simulating the scanning path of the array laser, and is used to illuminate the remote sensing imaging target 6 at different angles in a line-by-line scanning manner. When the fiber laser 2 illuminates the remote sensing imaging target 6 at different angles, the parallel light incident on the remote sensing imaging target 6 is at different positions, and the angle at which the target reflected light formed at each illumination position incident on the imaging receiving system is also different.

[0040] The imaging receiving system includes a front-facing lens 7, an imaging lens 8, and an imaging detector 9, which are sequentially located on the optical path of the reflected light from the target. The front-facing lens 7 is positioned on the object side of the imaging lens 8, and the back focal plane of the front-facing lens 7 coincides with the shortest imaging position of the imaging lens 8, thus forming a 4f-like imaging system with the front-facing lens 7 and the imaging lens 8. Figure 2 As shown, the rear focal plane of the front lens 7 is the spectral plane of the remote sensing imaging target 6, and the center of the image plane of the imaging detector 9 is the imaging plane of the low-resolution intensity image. The target reflected light under different illumination angles passes through the front lens 7 and obtains the spectral image of the remote sensing imaging target 6 under the corresponding illumination angle at the rear focal plane of the front lens 7. Then, it passes through the imaging lens 8 to form the low-resolution intensity image of the remote sensing imaging target 6 under the corresponding illumination angle.

[0041] Imaging detector 9 is used to detect low-resolution intensity images of remotely sensed target 6 under illumination at different angles and convert them into electrical signals. The input terminal of host computer 1 is connected to the output terminal of imaging detector 9. It is used to arrange the low-resolution intensity images of remotely sensed target 6 under illumination at different angles in the scanning order to form a low-resolution intensity image array, and to perform Fourier stacking high-resolution reconstruction on the low-resolution intensity image array to obtain a high-resolution reconstructed image.

[0042] Based on the aforementioned Fourier stacked remote sensing high-resolution imaging system, this invention also provides a Fourier stacked remote sensing high-resolution imaging method, which specifically includes the following steps:

[0043] Step 1: Construct the aforementioned Fourier stacked remote sensing high-resolution imaging system.

[0044] In this embodiment, a mirror-like American standard is selected as the remote sensing imaging target 6. After preparing the fiber laser 2, two-dimensional moving platform 3, fiber collimator 4, beam expander 5, front lens 7, imaging lens 8, and imaging detector 9, the fiber collimator 4 and beam expander 5 are fixed on the two-dimensional moving platform 3, and simultaneously positioned in the laser output path of the fiber laser 2. The remote sensing imaging target 6 is then placed in the parallel light path of the beam expander 5, with a working distance of approximately 34m between the remote sensing imaging target 6 and the fiber laser 2. The front lens 7, imaging lens 8, and imaging detector 9 are then sequentially placed in the light path of the target's reflected light, forming a 4f-like imaging system with the front lens 7 and imaging lens 8. After the above structure is assembled, the fiber optic head of the fiber laser 2 is finally fixed to the fiber collimator 4.

[0045] Step 2: Control the two-dimensional moving platform 3 to move horizontally and vertically, maintaining a fixed movement distance for each horizontal and vertical movement. This allows the fiber laser 2 to illuminate the remote-sensing imaging target 6 at N×N different angles in a line-by-line scanning manner. Specifically, the two-dimensional moving platform 3 drives the fiber laser 2 to illuminate the first line from left to right at N different angles, then the second line from left to right at N different angles, and so on, finally illuminating the Nth line from left to right at N different angles. The sequence of illumination changes of the fiber laser 2 on the remote-sensing imaging target 6 is as follows:

[0046] First row: 1, 2, 3, ..., N;

[0047] The second line: N+1, N+2, N+3, ..., 2N;

[0048]

[0049] Line N: N 2 -N+1,N 2-N+2,N 2 -N+3,…,N 2 .

[0050] In this embodiment, the fiber laser 2 illuminates the remote sensing imaging target 6 at 7×7 different angles using a line-by-line scanning method. The two-dimensional moving platform 3 maintains a fixed moving distance in both the horizontal and vertical directions during a single movement, effectively ensuring an overlap rate of over 50% between any two low-resolution images. The specific moving distance is determined based on the system aperture of the fiber laser 2. In this embodiment, the distance of the two-dimensional moving platform 3 during a single movement in both the horizontal and vertical directions is 10mm. The illumination sequence of the fiber laser 2 on the remote sensing imaging target 6 is as follows:

[0051] First row: 1, 2, 3, ..., 7;

[0052] Second row: 8, 9, 10, ..., 14;

[0053]

[0054] Seventh line: 43, 44, 45, ..., 49;

[0055] The fiber laser 2 illuminated the remote sensing imaging target 6 at a total of N×N=7×7=49 different angles.

[0056] Step 3: When the fiber laser 2 illuminates at the i-th angle, the target reflected light from the remote sensing imaging target 6 is imaged by the front lens 7, and the corresponding spectral image F of the remote sensing imaging target 6 is obtained on the rear focal plane of the front lens 7. i Remote sensing imaging target 6-spectral image F i The low-resolution intensity image I of the remote sensing target 6 is obtained at the center of the image plane of the imaging detector 9 through the imaging lens 8. i i = 1, 2, 3, ..., N. In this embodiment, the target reflected light from the remote sensing imaging target 6 under 49 different illumination angles is imaged by the front lens 7, and the spectral images of the remote sensing imaging target 6 obtained on the rear focal plane of the front lens 7 are F1 to F2. 49 Spectral image F1~F 49 The low-resolution intensity images of the remote-sensing target 6 obtained by the imaging lens 8 at the center of the image plane of the imaging detector 9 are I1~I 49 The final image center position of the imaging detector 9 corresponds to the set of low-resolution intensity images under illumination at 49 angles, as shown in the figure. Figure 3 As shown.

[0057] Step 4: The host computer 1 arranges the 49 low-resolution intensity images from different illumination angles input by the imaging detector 9 according to the scanning order, forming a sequence as shown in the image. Figure 3The low-resolution intensity image array is shown; Fourier overlay high-resolution reconstruction is performed on the low-resolution intensity image array to obtain a high-resolution image of remote sensing target 6.

[0058] like Figure 4 As shown, this is a comparison between the low-resolution intensity image of remote sensing target 6 obtained under illumination at the 25th angle and the reconstructed high-resolution image. Since the low-resolution intensity image obtained under illumination at the 25th angle is an intermediate image, it is usually the highest resolution image in the low-resolution intensity image array. However, it can be seen that the resolution of the reconstructed high-resolution image of remote sensing target 6 is much higher than that of the low-resolution intensity image of remote sensing target 6 obtained under illumination at the 25th angle.

[0059] The above description is only used to illustrate the technical solutions of the present invention, and is not intended to limit them. For those skilled in the art, modifications can be made to the specific technical solutions described in the above embodiments, or equivalent substitutions can be made to some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions protected by the present invention.

Claims

1. A Fourier stacked remote sensing high-resolution imaging system, characterized in that: Including a Fourier stacked remote sensing imaging system and a host computer (1); The Fourier stacked remote sensing imaging system includes an active illumination system and an imaging receiving system; The active illumination system includes a fiber laser (2), a two-dimensional moving platform (3), and a fiber collimator (4) and a beam expander (5) mounted on the two-dimensional moving platform (3); The fiber collimator (4) and the beam expander (5) are located sequentially on the laser output path of the fiber laser (2) to collimate and expand the output laser of the fiber laser (2) in sequence to form parallel light. The two-dimensional moving platform (3) is used to drive the fiber collimator (4) and the beam expander (5) to move in the horizontal and vertical directions; The remote sensing imaging target (6) is located on the parallel light path through the beam expander (5) and is used to reflect the parallel light to form the target reflected light; The fiber head of the fiber laser (2) is fixed on the fiber collimator (4) to make the fiber head of the fiber laser (2) follow the fiber collimator (4) to illuminate the remote sensing imaging target (6) at different angles in a line-by-line scanning manner. The imaging receiving system includes a front-facing lens (7), an imaging lens (8), and an imaging detector (9) located sequentially on the optical path of the reflected light from the target. The front lens (7) is positioned on the object side of the imaging lens (8), and the rear focal plane position of the front lens (7) coincides with the shortest imaging position of the imaging lens (8), so that the front lens (7) and the imaging lens (8) constitute a 4f-like imaging system; the target reflected light under different illumination angles passes through the front lens (7) and obtains the corresponding remote sensing imaging target (6) spectrum image at the rear focal plane position of the front lens (7), and then passes through the imaging lens (8) to form the corresponding remote sensing imaging target (6) low resolution intensity image; The imaging detector (9) is used to detect low-resolution intensity images of the remotely sensed imaging target (6) under illumination at different angles and convert them into electrical signals; The input end of the host computer (1) is connected to the output end of the imaging detector (9), which is used to arrange the low-resolution intensity images of the remote sensing imaging target (6) under different illumination angles in the scanning order to form a low-resolution intensity image array, and to perform Fourier stacked high-resolution reconstruction on the low-resolution intensity image array to obtain a high-resolution image of the remote sensing imaging target (6).

2. The Fourier stacked remote sensing high-resolution imaging system according to claim 1, characterized in that: The fiber laser (2) is a continuous single-mode fiber laser.

3. The Fourier stacked remote sensing high-resolution imaging system according to claim 2, characterized in that: The two-dimensional mobile platform (3) is an electric mobile platform.

4. The Fourier stacked remote sensing high-resolution imaging system according to claim 3, characterized in that: The diameter of the parallel light spot after beam expansion by the beam expander (5) is 10 times the diameter of the beam spot after collimation by the fiber collimator (4).

5. A Fourier layered remote sensing high-resolution imaging method, characterized in that, Includes the following steps: Step 1: Construct the Fourier stacked remote sensing high-resolution imaging system as described in any one of claims 1-4; Step 2: Control the two-dimensional moving platform (3) to move in the horizontal and vertical directions respectively, and keep a fixed moving distance for each single movement in the horizontal and vertical directions, so that the fiber laser (2) illuminates the remote sensing imaging target (6) at different angles in a line-by-line scanning manner; Step 3: The target reflected light under different illumination angles passes through the front lens (7) and then obtains the spectrum image of the remote sensing imaging target (6) under the corresponding illumination angle at the rear focal plane position of the front lens (7). Then, it passes through the imaging lens (8) and obtains the corresponding low-resolution intensity image of the remote sensing imaging target (6) on the imaging detector (9). Step 4: The host computer (1) arranges the low-resolution intensity images of the remote sensing imaging target (6) under different illumination angles input by the imaging detector (9) in the scanning order to form a low-resolution intensity image array. Then, Fourier stacking high-resolution reconstruction is performed on the low-resolution intensity image array to obtain a high-resolution image of the remote sensing imaging target (6).

6. The Fourier stacked remote sensing high-resolution imaging method according to claim 5, characterized in that: In step 2, the two-dimensional mobile platform (3) moves 10mm in both the horizontal and vertical directions in a single movement.

Images