Imaging adjustment system and method for differential synthetic aperture lidar

Abstract

The present invention provides an imaging adjustment system for a differential synthetic aperture lidar, comprising a receiving light beam combiner, a detector, a data acquisition unit, a data processing unit, a control unit, and a drive unit, arranged in sequence. Two symmetrically distributed subapertures are formed on the detector; the data processing unit is used to obtain the detector's relative azimuth tilt angle, and the drive unit is capable of driving the detector to rotate within a plane to adjust the tilt angle. The present invention has the advantage of detecting subaperture signals on the detector through the data processing unit and obtaining tilt angle data, which is then fed back to the control unit. The control unit then issues a control instruction to activate the drive unit, adjusting the detector's tilt angle to ultimately 0 degrees, thereby eliminating deviations in the subaperture positions and improving imaging quality.

Description

Technical Field

[0001] The present invention relates to the technical field of synthetic aperture laser radar, and in particular to an imaging adjustment system and method for differential synthetic aperture laser radar. Background Art

[0002] Differential synthetic aperture lidar is a hardware-based phase error correction method that can effectively eliminate the common-mode phase error between radar echo pulses and reconstruct phase-error-free imaging, which has important research significance.

[0003] However, the imaging process of differential synthetic aperture lidar requires that the receiving fields of view between adjacent sub-apertures at adjacent sampling positions in azimuth are completely matched, which places higher demands on the sub-aperture position, sampling step interval, radar platform stability, etc. Regarding the position deviation between sub-apertures in distance that causes differential synthetic aperture lidar imaging tilt, some units have conducted research [Lei, W., Jin, W., Danyang, L., Debin, W., and Changjun, K., “Image inclination in differential synthetic aperture ladar,” Opt. Eng, 58(3), 033101(2019)], analyzed the principle of imaging tilt, and repaired the imaging results accordingly through data post-processing. In actual imaging environments, a moving platform can easily cause azimuth sampling position deviations between subapertures, leading to subaperture field of view mismatch. This can also introduce additional phase errors, affecting imaging quality [Guo, Z., Yebin, Z., Kai, W., et al. “Sub-aperture field of view mismatch in differential synthetic aperture ladar,” Proc of SPIE, 119070U, (2021)]. Currently, there are various autofocus devices and methods [Zhou Honglong, Kang Zhongjia, Zhang Wenyan, Huang Yucheng. “Autofocus Method and Autofocus Device,” Patent No. ZL104133339B], but these devices are only suitable for focusing optical intensity imaging and are not suitable for adjusting field of view mismatch and position deviation between subapertures in differential synthetic aperture lidar.

[0004] Patent application CN102122082A discloses a phase shift error correction device for a sparse optical synthetic aperture imaging system. It also discloses a technical solution for compensating for phase shift errors using an error compensator. This solution compensates for the phase error between multiple samplings of a single aperture in a sparse optical synthetic aperture imaging system and is not suitable for compensating for phase errors between subapertures of a differential synthetic aperture lidar (DSA) system. During DSA imaging, the field of view (FOV) between subapertures must be perfectly matched to suppress common-mode phase errors between them. Field of view mismatch and positional deviation between subapertures significantly impact imaging quality. Currently, there are no reported solutions for real-time correction of field of view mismatch and positional deviation between subapertures, which cannot meet the needs of applications requiring high imaging quality. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an imaging adjustment system and method which can automatically adjust the position of the sub-aperture to eliminate the adverse effect of tilt on imaging quality.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions: an imaging adjustment system for a differential synthetic aperture lidar, comprising a receiving photosensor, a detector, a data acquisition unit, a data processing unit, a control unit and a driving unit arranged in sequence, forming two symmetrically distributed sub-apertures on the detector; the data processing unit is used to obtain the inclination angle of the detector relative to the azimuth direction, and the driving unit can drive the detector to rotate in a plane to adjust the inclination angle.

[0007] The present invention detects the sub-aperture signal on the detector through a data processing unit and obtains the inclination data, which is then fed back to the control unit. The control unit issues a control instruction to activate the driving unit to adjust the detector inclination, ensure that the deviation of the sub-aperture position is eliminated, and improve the imaging quality.

[0008] Preferably, a plurality of pixels are distributed in an array on the detector, and each sub-aperture includes a plurality of pixels arranged in an equal number in an array.

[0009] Preferably, the data acquisition unit acquires output data of each pixel on the detector and transmits the data to the data processing unit.

[0010] Preferably, the data processing unit is further capable of performing synthetic aperture imaging based on the output data of the data acquisition unit, and determining a sub-aperture structure with the best imaging effect.

[0011] Preferably, the driving unit is a motor that is in transmission cooperation with the detector, and the output shaft of the driving unit is perpendicular to the surface of the detector.

[0012] The present invention also provides a method for performing imaging adjustment on a differential synthetic aperture laser radar based on the system, comprising:

[0013] S1, assemble the system according to the preset order, adjust the optical path, so that the signal light and the local oscillator light enter the detector through the receiving combiner;

[0014] S2, determining the inclination of the detector relative to the azimuth through the data processing unit and feeding it back to the control unit;

[0015] S3, the control unit controls the action of the driving unit based on the inclination angle of the detector to adjust the inclination angle of the detector;

[0016] S4: Repeat S2-S3 until the inclination angle of the detector is 0 degrees.

[0017] Preferably, the method further includes a step of determining an optimal subaperture structure based on a data processing unit, comprising:

[0018] Step i: After adjusting the detector inclination angle to 0 degrees, the M×N pixels on the detector are evenly divided into two left and right sub-apertures. The number of pixels in each sub-aperture is Initialize i=0;

[0019] Step ii: the data processing unit performs synthetic aperture two-dimensional imaging based on the output signals of all pixels in the two sub-apertures;

[0020] Step iii: The signal-to-noise ratio corresponding to the pixel with the largest signal intensity in the obtained image is used as the signal-to-noise ratio N of the sub-aperture structure. i ;

[0021] Step iv: If

[0022] When mod(i, 2) = 0, set i = i + 1, delete the outermost column of the current sub-aperture, and return to step ii;

[0023] When mod(i, 2) = 1, set i = i + 1, delete the innermost column of the current sub-aperture, and return to step ii;

[0024] Where mod(i, 2) represents the remainder when i is divided by 2;

[0025] Otherwise, output N i The value of i corresponding to the maximum value.

[0026] Preferably, the signal-to-noise ratio of the pixel point is the ratio of the signal intensity to the background noise intensity.

[0027] The imaging adjustment system and method for differential synthetic aperture lidar (DSA) provided by the present invention have the advantages of detecting subaperture signals on the detector through a data processing unit, obtaining tilt angle data, and then feeding this data back to a control unit. The control unit then issues control instructions to activate the drive unit, adjusting the detector tilt angle, ensuring that deviations in subaperture position are eliminated and improving imaging quality. The data processing unit can select corresponding pixels for data processing based on the subaperture structure, making it easy to use. Furthermore, the data processing unit can evaluate imaging quality and determine the optimal subaperture structure, which can be directly used for DSA imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of an imaging adjustment system for a differential synthetic aperture laser radar provided by an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of a detector tilt state of an imaging adjustment system for a differential synthetic aperture laser radar provided by an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of the initial sub-aperture structure of an imaging adjustment system for a differential synthetic aperture lidar provided by an embodiment of the present invention;

[0031] Figure 4 A schematic diagram of the optimal sub-aperture structure of an imaging adjustment system for a differential synthetic aperture lidar provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the following describes the technical solutions of the present invention clearly and completely with reference to specific embodiments and the accompanying drawings. It is obvious that the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] like Figure 1 As shown, this embodiment provides an imaging adjustment system for a differential synthetic aperture lidar, comprising a receiving photosensor 1, a detector 2, a data acquisition unit 3, a data processing unit 4, a control unit 5 and a driving unit 6 arranged in sequence, forming two symmetrically distributed sub-apertures on the detector 2; the data processing unit 4 is used to obtain the inclination angle of the detector 2 relative to the azimuth direction, and the driving unit 6 can drive the detector 2 to rotate in a plane to adjust the inclination angle.

[0034] In this embodiment, the data processing unit 4 detects the sub-aperture signal on the detector 2 and obtains the inclination data, which is then fed back to the control unit 5. The control unit 5 issues a control instruction to activate the driving unit 6 to adjust the inclination of the detector 2, thereby ensuring that the deviation of the sub-aperture position is eliminated and improving the imaging quality.

[0035] refer to Figure 2 The data processing unit 4 obtains the data received by the data acquisition unit 3, and then calculates the inclination data based on the basic principle of differential synthetic aperture lidar imaging inclination, thereby obtaining the inclination angle β of the detector 2. For a specific method, please refer to the document "Lei, W., Jin, W., Danyang, L., Debin, W., and Changjun, K., "Image inclination in differential synthetic aperture ladar," Opt. Eng, 58(3), 033101(2019)". Based on the obtained inclination angle β, the inclination angle of the detector 2 can be adjusted by the driving unit 6.

[0036] refer to Figure 3 The detector 2 has a plurality of pixels arranged in an array, and each subaperture includes a plurality of pixels arranged in an equal array. The data acquisition unit 3 collects the output data of each pixel on the detector 2 and transmits the data to the data processing unit 4. The data processing unit 4 processes the data based on the data corresponding to all pixels included in the subaperture. The data processing unit 4 can also perform synthetic aperture imaging based on the data output by the data acquisition unit 3 and determine the subaperture structure that achieves the best imaging effect.

[0037] The driving unit 6 is an electrode that cooperates with the detector 2 in transmission. The detector 2 is fixed on a rotating shaft. The driving unit 6 controls the inclination angle of the detector 2 by cooperating with the rotating shaft. The output shaft of the driving unit 6 is perpendicular to the surface of the detector 2.

[0038] This embodiment also provides an imaging adjustment method for a differential synthetic aperture laser radar, comprising the following steps:

[0039] S1, assemble the system according to the preset sequence and adjust the optical path so that the signal light and the local oscillator light enter the detector 2 through the receiving combiner 1;

[0040] S2, determining the inclination of the detector 2 through the data processing unit 4 and feeding it back to the control unit 5;

[0041] S3, the control unit 5 controls the driving unit 6 to operate based on the inclination angle of the detector 2 to adjust the inclination angle of the detector 2;

[0042] S4: Repeat S2-S3 until the inclination angle of detector 2 is 0 degrees.

[0043] The above method continuously controls and adjusts the inclination angle of the detector 2 through the idea of ​​feedback regulation until the inclination angle is adjusted to 0 degrees.

[0044] This embodiment further includes a step of determining an optimal subaperture structure based on the data processing unit, including:

[0045] Step i: After adjusting the detector 2 inclination angle to 0 degrees, the M×N pixels on the detector 2 are divided into two left and right sub-apertures (such as Figure 3 As shown), the number of pixels in each sub-aperture is Initialize i=0;

[0046] Step ii: the data processing unit 4 performs differential synthetic aperture two-dimensional imaging based on the output signals of all pixels in the two sub-apertures;

[0047] Step iii: The signal-to-noise ratio corresponding to the pixel with the largest signal intensity in the obtained image is used as the signal-to-noise ratio N of the sub-aperture structure. i ;

[0048] Step iv: If

[0049] When mod(i, 2) = 0, set i = i + 1, delete the outermost column of the current sub-aperture, and return to step ii;

[0050] When mod(i, 2) = 1, set i = i + 1, delete the innermost column of the current sub-aperture, and return to step ii;

[0051] Where mod(i, 2) represents the remainder when i is divided by 2;

[0052] Otherwise, output N i The value of i corresponding to the maximum value.

[0053] The sub-aperture structure with the best imaging quality is expressed as Structural diagram reference Figure 4 .

[0054] The signal-to-noise ratio is the ratio of the signal intensity of the desired reading point to the background noise intensity, which can be obtained based on the calculation method in the prior art.

[0055] After the tilt adjustment of the detector 2 is completed, the data processing unit 4 may be replaced with a dedicated imaging unit to complete differential synthetic aperture imaging and imaging quality evaluation.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An imaging adjustment system for a differential synthetic aperture laser radar, characterized by: The invention comprises a receiving light beam combiner, a detector, a data acquisition unit, a data processing unit, a control unit and a driving unit, which are arranged in sequence, and two symmetrically distributed sub-apertures are formed on the detector; the data processing unit is used to obtain the inclination angle of the detector relative to the azimuth direction, and the driving unit can drive the detector to rotate in a plane to adjust the detector inclination angle; The detector has a plurality of pixels distributed in an array, and each sub-aperture includes a plurality of pixels arranged in an array in equal amounts; The data acquisition unit collects the output data of each pixel on the detector and transmits the data to the data processing unit; The data processing unit can also perform synthetic aperture imaging based on the output data of the data acquisition unit and determine the sub-aperture structure with the best imaging effect; The step of determining the optimal sub-aperture structure by the data processing unit includes: Step i: After adjusting the detector angle to 0 degrees, The pixels are evenly divided into two sub-apertures on the left and right, and the number of pixels in each sub-aperture is , initialize i=0; Step ii: the data processing unit performs differential synthetic aperture two-dimensional imaging based on the output signals of all pixels in the two sub-apertures; Step iii: The signal-to-noise ratio corresponding to the pixel with the largest signal intensity in the obtained image is used as the signal-to-noise ratio of the sub-aperture structure ; Step iv: If , exist When , let i = i + 1, delete the outermost column of the current sub-aperture, and return to step ii; exist When , let i = i + 1, delete the innermost column of the current sub-aperture, and return to step ii; in, It represents the remainder when i is divided by 2; Otherwise, output The i value corresponding to the maximum value; The signal-to-noise ratio of a pixel is the ratio of the signal intensity to the background noise intensity.

2. The imaging adjustment system for differential synthetic aperture laser radar according to claim 1, characterized in that: The driving unit is a motor that is in transmission cooperation with the detector, and the output shaft of the driving unit is perpendicular to the surface of the detector.

3. The method for performing imaging adjustment on a differential synthetic aperture laser radar according to any one of claims 1 to 2, characterized in that: include, S1, assemble the system according to the preset order and adjust the optical path so that the signal light and the local oscillator light enter the detector through the receiving combiner; S2, determining the inclination of the detector relative to the azimuth through the data processing unit and feeding it back to the control unit; S3, the control unit controls the driving unit to adjust the inclination of the detector based on the inclination of the detector; S4: Repeat S2-S3 until the inclination angle of the detector is 0 degrees.

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