In the face of small targets at a distance, conventional means of detection can often only be localized to see the target is just a point. And some special needs, the need to master its surface characteristics and even body characteristics, to achieve the movement of the target cognition, there is an urgent need to develop super-resolution imaging means. National University of Defense Technology Pulsed Power Laser Technology, director of the State Key Laboratory of Professor Hu Yihua team, following the realization of the 10 km distance in 2022 better than 2 cm resolution at home and abroad to report the highest level of reflection chromatography LIDAR super-resolution two-dimensional imaging based on the recent realization of three-dimensional super-resolution imaging of a major breakthrough.
Realization of three-dimensional super-resolution imaging with 2.0 x 2.0 x 3.5 cm resolution at a distance of 10 km
The principle of two-dimensional imaging by reflectance tomography lidar is getting mature, and relevant experimental research has been carried out at home and abroad, but the principle and method of three-dimensional imaging have not been reported at home and abroad. The team innovatively put forward the three-dimensional imaging technology architecture of reflective chromatography lidar, established the multi-angle and multi-field-of-view interleaved sampling of laser detection, high-speed and high-fidelity acquisition of narrow-pulse laser echo, and image reconstruction and fusion processing methods, and developed the three-dimensional imaging experimental system of reflective chromatography lidar, and carried out the outfield experiments in Zipeng Mountain area of Hefei, which was at a distance of 10.38 km, to realize the three-dimensional super-resolution reconstruction of the target image. The experiments were carried out at a distance of 10.38 km in Zipeng Mountain, Hefei, to realize three-dimensional super-resolution reconstruction of target images.
In the experiment, two types of targets were set up on a 100-meter-high experimental tower on the mountain (31°43′28″N, 116°59′55″E): 1) a stereo assembly with a height of 75 cm and a width of 30 cm, as shown in Fig. 1 (a); 2) a 60° trapezoidal target with a tilting angle of 60° and a tilting angle of 60°, which is composed of multiple blocks with a thickness of 1.7 cm and different cross-sectional areas, with the spacing decreasing from 9 to 2 cm from the bottom to the top, and with an area of gradually decreasing. tilt angle trapezoidal stereo resolution test target, as shown in Fig. 1 (b). The imaging experimental system was arranged on the upper floor of South China City (31°46′20″N, 117°5′35″E) in the city, as shown in Fig. 1 (c). Under a variety of experimental environments and experimental parameter settings, three-dimensional super-resolution imaging results of stereo targets were successfully obtained as shown in Figs. 2 (b) and 2 (d).
Fig. 1 Reflectance tomography lidar three-dimensional imaging experimental implementation diagrams
(a) Stereo assembly (b) Stereo resolution test target
(c) Reflectance tomography lidar 3D imaging experiment system
According to the principle of reflective chromatography LIDAR imaging, as long as the signal-to-noise ratio of the laser pulse echo is sufficient, the 3D imaging resolution is relatively independent of the optical aperture, distance, and laser divergence angle, so this experiment lays the foundation for realizing the 3D imaging of tiny targets at ultra-long distances of thousands of meters. Therefore, this experiment lays the foundation for the realization of three-dimensional imaging of ultra-long-distance tiny targets at kilometers. The optical aperture of the experimental system is 260 mm, and the diffraction limit angle of the optical imaging system with the same aperture is about 5 μrad, which corresponds to the limiting resolution of conventional optical imaging at 10 km of about 5 cm, and the present results have achieved the super-resolution imaging capability of small targets at a long distance that exceeds the diffraction limit of the optical imaging of the same aperture, and the imaging resolution is at the optimal level of the laser imaging field at home and abroad, especially the stereoscopic imaging of small objects is obtained for the first time by the original technical means and processing algorithms. The imaging resolution is the best in the field of laser imaging at home and abroad, especially the first time to get the centimeter-level super-resolution 3D imaging results of three-dimensional target structure at a distance of 10 km by the original technical means and processing algorithm.
Figure 2 Target object and imaging results
(a) Stereoscopic assembly
(b) Reconstructed image of the three-dimensional assembly
(c) Stereo resolution test target
(d) Reconstructed image of the stereo resolution test target
