Fourier lamination remote sensing high-resolution imaging system and imaging method

Abstract

The invention provides a Fourier lamination remote sensing high-resolution imaging system and an imaging method, and aims to solve the problems that an optical path of an existing simulation Fourier lamination remote sensing imaging system is relatively complex, and the adjustment difficulty is increased along with the increase of the working distance of a target; or the technical problem that the illumination light path part of the actual remote sensing imaging target cannot meet the actual condition is solved. According to the Fourier laminated remote sensing high-resolution imaging system, the optical fiber collimator and the beam expander are adopted to enable the laser light source to form parallel light, the parallel light obtained in the mode is not subjected to shaping constraint any more, an illumination system is greatly simplified, and the actual illumination condition of a remote sensing imaging target can be better simulated; and meanwhile, reflection information of a remote sensing imaging target is received by adopting a similar 4f imaging system, and imaging can be realized only through simple adjustment under the condition that the laboratory work is limited or under the real external field experiment condition that the far field diffraction condition is met.

Description

Technical Field

[0001] The present invention belongs to the field of optical imaging, and in particular relates to a Fourier stack remote sensing high-resolution imaging system and an imaging method, which are used to achieve high-resolution imaging of a long-distance target. Background Art

[0002] High-precision and high-resolution imaging is the main direction for future ground imaging, optical situational awareness, early warning and space target imaging. In satellite-borne optical imaging systems, the traditional method to improve the resolution of imaging targets is mainly to expand the aperture of the receiving optical system by using technologies such as splicing expandable and block assembly optical synthetic apertures. However, considering the quality and volume of the optical system, the difficulty of processing and assembly, and the phase matching accuracy, it is impossible to simply improve the aperture of the receiving optical system.

[0003] Fourier stack imaging technology has been extended from the millimeter-level working distance in optical microscopy to the current meter-level working distance. With the extension of laser illumination distance, the continuous increase of optical aperture and the application of more sensitive cameras, it is possible to extend this technology to tens or even hundreds of kilometers for detection. This technology can subvert the traditional synthetic aperture technology and provide an important research idea for exploring new, large-field-of-view, high-performance and low-cost active coherent synthetic aperture long-distance imaging technology.

[0004] However, from the perspective of existing simulated Fourier stack remote sensing imaging systems, the optical system is mainly divided into two experimental systems to meet the requirements of laboratory imaging: one is to perform shaping from the light source emission end to meet the far-field Fraunhofer far-field diffraction, and perform spectral domain constraints at the image plane position of the light source, that is, the spectral position of the object, and then the imaging optical lens and the detector receive the image; the other is to use a parallel light tube to simulate the parallel light beam of remote sensing imaging. The target is located in front of the parallel light tube, and the target's spectrum is received and constrained at the rear end of the parallel light tube, and then the imaging lens and the detector receive the image. Although the above two imaging systems can basically meet the requirements of far-field Fourier stack far-field diffraction imaging, the first method, whether it is light source scanning or detector scanning, has a relatively complex optical path, and the difficulty of adjustment increases as the working distance of the target continues to increase; the second method's collimator can simulate the parallel optical path very well, but under actual conditions, the laser actively images the remote sensing target, and the spherical wave emitted by the laser is expanded 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, it is an ideal situation for the collimator to simulate remote sensing long-distance targets. The actual situation is relatively complicated, and the illumination optical path part for the actual remote sensing imaging target still cannot better meet the actual situation. Summary of the invention

[0005] The purpose of the present invention is to propose a Fourier stack remote sensing high-resolution imaging system and imaging method to address the technical problems that the optical path of the existing simulated Fourier stack remote sensing imaging system is relatively complex, the adjustment difficulty increases with the increase of the working distance of the target, or the illumination optical path part of the actual remote sensing imaging target cannot meet the actual situation.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A Fourier stack remote sensing high-resolution imaging system, which is special in that it comprises a Fourier stack remote sensing imaging system and a host computer;

[0008] The Fourier stack remote sensing imaging system includes an active lighting system and an imaging receiving system;

[0009] The active illumination system comprises a fiber laser, a two-dimensional mobile platform, and a fiber collimator and a beam expander arranged on the two-dimensional mobile platform;

[0010] The fiber collimator and the beam expander are sequentially located on the laser output light 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 drive the optical fiber collimator and the beam expander to move in the horizontal direction and the vertical direction;

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

[0013] The optical fiber head of the optical fiber laser is fixed on the optical fiber collimator, and is used to make the optical fiber head of the optical fiber laser move with the optical 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 comprises a front lens, an imaging lens and an imaging detector which are sequentially located on the optical path of the target reflected light;

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

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

[0017] The input end of the host computer is connected to the output end of the imaging detector, and is used to arrange the low-resolution intensity images of the remote sensing imaging target when illuminated at different angles in a scanning order to form a low-resolution intensity image array, and 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 spot diameter of the parallel light after being expanded by the beam expander is 10 times the spot diameter of the beam after being collimated by the fiber collimator.

[0021] In addition, the present invention also provides a Fourier stack remote sensing high-resolution imaging method, which is special in that it includes the following steps:

[0022] Step 1, constructing the above-mentioned Fourier stack remote sensing high-resolution imaging system;

[0023] Step 2, controlling the two-dimensional mobile platform to move in the horizontal direction and the vertical direction 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 mobile platform maintains a fixed moving distance in the horizontal direction and the vertical direction for a single movement, so as to ensure that the overlap rate between every two low-resolution images is more than 50%;

[0024] Step 3, after the target reflected light under different angles of illumination passes through the front lens, a spectrum image of the remote sensing imaging target under the corresponding angle of illumination is obtained at the rear focal plane position of the front lens, and then a corresponding low-resolution intensity image of the remote sensing imaging target is obtained on the imaging detector through the imaging lens;

[0025] Step 4: The host computer arranges the low-resolution intensity images of the remote sensing imaging target when illuminated at different angles input by the imaging detector in a scanning order to form a low-resolution intensity image array, and then performs Fourier stacking high-resolution reconstruction on the low-resolution intensity image array to obtain a high-resolution image of the remote sensing imaging target.

[0026] Furthermore, in step 2, the single moving distance of the two-dimensional moving platform in the horizontal direction and the vertical direction is 10 mm.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a Fourier stack remote sensing high-resolution imaging system, in which an active lighting system uses a fiber collimator and a beam expander to collimate and expand a laser light source to form parallel light. The parallel light obtained in this way is no longer subject to shaping constraints, and directly illuminates a remote sensing imaging target, simulating the active laser illumination of a remote sensing target at infinity, which not only greatly simplifies the lighting system, but also can better simulate the illumination of the target in actual remote sensing imaging to meet the actual situation; at the same time, a 4f-like imaging system is used to receive reflection information of the remote sensing imaging target, so the system is simpler and easier to adjust. This method can be applied to a laboratory or any working mode that does not meet the Fraunhofer remote sensing long-distance imaging requirements, and when the imaging system distance meets the Fraunhofer remote sensing long-distance imaging conditions or the actual remote sensing imaging conditions, imaging can be achieved by directly removing the front lens; therefore, compared with the existing remote sensing imaging lens, this receiving system method is simpler and more flexible, and the sampling process is more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic structural diagram of an embodiment of a Fourier stack remote sensing high-resolution imaging system of the present invention;

[0030] Figure 2 A schematic diagram of the structure of an imaging receiving system in an embodiment of the present invention;

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

[0032] Figure 4 This is a comparison diagram of a low-resolution intensity image obtained when the remote sensing imaging target is illuminated at the 25th angle and a high-resolution image after reconstruction in an embodiment of a Fourier stack remote sensing high-resolution imaging method of the present invention, wherein (a) is the low-resolution intensity image of the remote sensing imaging target obtained when illuminated at the 25th angle, and (b) is the high-resolution image of the remote sensing imaging target after reconstruction.

[0033] The specific reference numerals are as follows:

[0034] 1-host computer; 2-fiber laser; 3-two-dimensional mobile platform; 4-fiber collimator; 5-beam expander; 6-remote sensing imaging target; 7-front lens; 8-imaging lens; 9-imaging detector. DETAILED DESCRIPTION

[0035] In order to make the advantages and features of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] like Figure 1As shown, a Fourier stack remote sensing high-resolution imaging system includes a Fourier stack remote sensing imaging system and a host computer 1. The Fourier stack 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 mobile platform 3, a fiber collimator 4 and a beam expander 5. The fiber laser 2 preferably adopts a continuous single-mode fiber laser, which is used to illuminate the remote sensing imaging target 6. The fiber collimator 4 and the beam expander 5 are sequentially located on the laser output light path of the fiber laser 2. The fiber collimator 4 is used to collimate the output laser of the fiber laser 2, and the beam expander 5 is used to expand the collimated light beam passing through the fiber collimator 4 to form parallel light. The spot diameter of the parallel light after expansion is about 10 times the spot diameter of the collimated light beam.

[0038] The two-dimensional mobile platform 3 can move in the horizontal direction and the vertical direction. The fiber collimator 4 and the beam expander 5 are fixedly arranged on the two-dimensional mobile platform 3. At the same time, the fiber head of the fiber laser 2 is fixed on the fiber collimator 4, which is used to drive the fiber collimator 4 and the beam expander 5 to move accordingly through the movement of the two-dimensional mobile platform 3 in the horizontal direction and the vertical direction, thereby driving the fiber head of the fiber laser 2 to move accordingly.

[0039] The remote sensing imaging target 6 is usually a mirror resolution target or a diffuse reflection target with certain scattering characteristics, which is located on the parallel light path through the beam expander 5 and is used to reflect the parallel light to form 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 position of the parallel light incident on the remote sensing imaging target 6 is different, and the angle of the target reflected light formed by the reflection at each illumination position incident on the imaging receiving system is also different.

[0040] The imaging receiving system includes a front lens 7, an imaging lens 8 and an imaging detector 9 which are sequentially located on the optical path of the target reflected light. The front lens 7 is arranged 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 quasi-4f imaging system. Figure 2 As shown, the rear focal plane position of the front lens 7 is the spectrum surface of the remote sensing imaging target 6, the image plane center position of the imaging detector 9 is the imaging surface of the low-resolution intensity image, and the target reflected light under different angles of illumination passes through the front lens 7, and the spectrum image of the remote sensing imaging target 6 under the corresponding angle of illumination is obtained at the rear focal plane position of the front lens 7, and then passes through the imaging lens 8 to form a low-resolution intensity image of the remote sensing imaging target 6 under the corresponding angle of illumination.

[0041] The imaging detector 9 is used to detect the low-resolution intensity image of the remote sensing imaging target 6 when illuminated at different angles and convert it into an electrical signal. The input end of the host computer 1 is connected to the output end of the imaging detector 9, and is used to arrange the low-resolution intensity images of the remote sensing imaging target 6 when illuminated at different angles in a scanning order to form a low-resolution intensity image array, and perform Fourier stacking high-resolution reconstruction on the low-resolution intensity image array to obtain a high-resolution reconstructed image.

[0042] Based on the above-mentioned Fourier stack remote sensing high-resolution imaging system, the present invention also provides a Fourier stack remote sensing high-resolution imaging method, which specifically includes the following steps:

[0043] Step 1: Build the above-mentioned Fourier stack remote sensing high-resolution imaging system.

[0044] In this embodiment, the mirror American standard is selected as the remote sensing imaging target 6. After preparing the fiber laser 2, the two-dimensional mobile platform 3, the fiber collimator 4, the beam expander 5, the front lens 7, the imaging lens 8 and the imaging detector 9, the fiber collimator 4 and the beam expander 5 are fixed on the two-dimensional mobile platform 3, and the fiber collimator 4 and the beam expander 5 are sequentially located on the laser emission optical path of the fiber laser 2; then the remote sensing imaging target 6 is set on the parallel light optical path through the beam expander 5, and the working distance between the remote sensing imaging target 6 and the fiber laser 2 is about 34m, and then the front lens 7, the imaging lens 8, and the imaging detector 9 are sequentially set on the optical path of the target reflected light, and the front lens 7 and the imaging lens 8 constitute a 4f-like imaging system. After the above structure is built, the fiber head of the fiber laser 2 is finally fixed on the fiber collimator 4.

[0045] Step 2, control the two-dimensional mobile platform 3 to move in the horizontal direction and the vertical direction, and keep a fixed moving distance for each single movement in the horizontal direction and the vertical direction, so that the fiber laser 2 illuminates the remote sensing imaging target 6 at N×N different angles in a row-by-row scanning manner, that is, the two-dimensional mobile platform 3 drives the fiber laser 2 to illuminate at N different angles from left to right in the first row, and then illuminate at N different angles from left to right in the second row, and so on, and finally illuminate at N different angles from left to right in the Nth row. The illumination change sequence of the fiber laser 2 on the remote sensing imaging target 6 is:

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

[0047] Second row: 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 in a line-by-line scanning manner. The two-dimensional mobile platform 3 maintains a fixed moving distance in a single movement in the horizontal direction and the vertical direction, which can effectively ensure that the overlap rate between each two low-resolution images is more than 50%. The specific moving distance is determined according to the system aperture of the fiber laser 2. In this embodiment, the distance of the two-dimensional mobile platform 3 in a single movement in the horizontal direction and the vertical direction is 10 mm. The illumination change sequence of the remote sensing imaging target 6 by the fiber laser 2 is:

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

[0052] Second row: 8,9,10,…,14;

[0053]

[0054] The seventh row: 43, 44, 45, ..., 49;

[0055] The fiber laser 2 illuminates 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 is illuminated at the i-th angle, the target reflected light reflected by the remote sensing imaging target 6 is imaged once through the front lens 7, and the corresponding spectrum 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 spectrum image F i The corresponding low-resolution intensity image I of the remote sensing imaging 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 reflected by the remote sensing imaging target 6 when illuminated at 49 different angles is imaged once by the front lens 7, and the spectrum images of the remote sensing imaging target 6 obtained on the rear focal plane of the front lens 7 are respectively F 1 ~F 49 , spectrum image F 1 ~F 49 The low-resolution intensity images of the remote sensing imaging target 6 obtained by the imaging lens 8 at the center of the image plane of the imaging detector 9 are respectively I 1 ~I 49 Finally, the image plane center position of the imaging detector 9 corresponds to a set of low-resolution intensity images at 49 illumination angles as follows: Figure 3 shown.

[0057] Step 4: The host computer 1 arranges the low-resolution intensity images of 49 different illumination angles input by the imaging detector 9 in a scanning order to form Figure 3 The low-resolution intensity image array shown is used; the low-resolution intensity image array is reconstructed by Fourier stacking to obtain a high-resolution image of the remote sensing imaging target 6.

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

[0059] The above description is only used to illustrate the technical solution of the present invention rather than to limit it. For ordinary professional and technical personnel in the field, the specific technical solution recorded in the above embodiment can be modified, or some of the technical features therein can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution protected by the present invention.

Claims

1. A Fourier stack remote sensing high-resolution imaging system, characterized in that: It includes a Fourier stack remote sensing imaging system and a host computer (1); The Fourier stack remote sensing imaging system includes an active lighting system and an imaging receiving system; The active illumination system comprises a fiber laser (2), a two-dimensional mobile platform (3), and a fiber collimator (4) and a beam expander (5) arranged on the two-dimensional mobile platform (3); The optical fiber collimator (4) and the beam expander (5) are sequentially located on the laser output light path of the optical fiber laser (2) and are used to sequentially collimate and expand the output laser of the optical fiber laser (2) to form parallel light; The two-dimensional moving platform (3) is used to drive the optical fiber collimator (4) and the beam expander (5) to move in the horizontal direction and the vertical direction; The remote sensing imaging target (6) is located on the optical path of the parallel light passing through the beam expander (5), and is used to reflect the parallel light to form target reflected light; The optical fiber head of the optical fiber laser (2) is fixed on the optical fiber collimator (4), so that the optical fiber head of the optical fiber laser (2) moves along with the optical 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 comprises a front lens (7), an imaging lens (8) and an imaging detector (9) which are sequentially located on the optical path of the target reflected light; The front lens (7) is arranged 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 quasi-4f imaging system; the target reflected light under different angles of illumination passes through the front lens (7) to obtain a corresponding spectrum image of the remote sensing imaging target (6) at the rear focal plane position of the front lens (7), and then passes through the imaging lens (8) to form a corresponding low-resolution intensity image of the remote sensing imaging target (6); The imaging detector (9) is used to detect low-resolution intensity images of the remote sensing imaging target (6) when illuminated at different angles, and convert the images into electrical signals; The input end of the host computer (1) is connected to the output end of the imaging detector (9) and is used to arrange low-resolution intensity images of the remote sensing imaging target (6) in a scanning order when illuminated at different angles 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 (6).

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

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

5. A Fourier stack remote sensing high-resolution imaging method, characterized in that: The following steps are involved: Step 1, constructing the Fourier stack remote sensing high-resolution imaging system described in any one of claims 1 to 4; Step 2, controlling the two-dimensional mobile platform (3) to move in the horizontal direction and the vertical direction respectively, and maintaining a fixed moving distance for each single movement in the horizontal direction and the vertical direction, 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, after the target reflected light under different angles of illumination passes through the front lens (7), a spectrum image of the remote sensing imaging target (6) under the corresponding angle of illumination is obtained at the rear focal plane position of the front lens (7), and then passes through the imaging lens (8) to obtain a 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) input by the imaging detector (9) at different illumination angles in a scanning order to form a low-resolution intensity image array, and then performs Fourier stacking high-resolution reconstruction on the low-resolution intensity image array to obtain a high-resolution image of the remote sensing imaging target (6).

6. A Fourier stack remote sensing high-resolution imaging method according to claim 5, characterized in that: In step 2, the single moving distance of the two-dimensional moving platform (3) in the horizontal direction and the vertical direction is 10 mm.

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