3D Reconstruction Of Plasma Intensity

The friction between the aircraft and the atmosphere in the adjacent space will generate plasma.The"plasma sheath"formed on the surface causes the"black barrier"phenomenon that seriously affects communication.How to solve the"black barrier"problem has become a difficult problem in the development of the aerospace industry.Therefore,it is necessary to diagnose the plasma that produces the"black barrier".The 3D reconstruction of plasma light intensity is expected to work with other plasma diagnostic equipment to diagnose plasma qualitatively and quantitatively,and the light intensity reconstruction algorithm can also be used in fields such as flame temperature field analysis.In this paper,three-dimensional reconstruction is carried out in two hardware systems for three-dimensional reconstruction:1)Circular distribution experimental system.A circular distributed experimental system was built to realize hardware synchronization triggering,light intensity response calibration,and camera internal and external parameter calibration.The system adopts flame to simulate plasma,the system is small and exquisite,and the experiment and debugging are convenient.2)Plasma diagnostic experiment system.Finished the work of camera installation,camera control,and experimental data collection.The camera was calibrated for light intensity response and internal and external parameters.Among them,it was found that the glass medium moved due to vacuuming,which caused the change of refraction angle and caused the image to shift.Phenomenon,it is proposed to use the image of the calibration board in the vacuum state to calibrate the external parameters of the camera,which improves the calibration accuracy.In this paper,two three-dimensional reconstruction methods are realized:surface tomography and volume tomography.Surface tomography is based on Radon transform,and volume tomography is based on projective geometry and camera imaging model.Surface tomography divides the three-dimensional object to be reconstructed into layers of unknown cross-sections.Each row(column)of the image represents the projection of each cross-section.There is no overlap relationship between the cross-sections,and each reconstructed layer is stacked.To form a three-dimensional model.Volume tomography divides the three-dimensional object to be reconstructed into a number of voxel grids of unknown brightness.The voxel grid is projected to the image plane through the principle of camera imaging geometry.The gray value of the pixels on the image plane is all the light passing through.The integral of the brightness value of the voxel grid.The camera calibration is used to obtain the correspondence between the voxel grid space position and the pixel,and the projection weight matrix is calculated by the projection area.This paper proposes a mask method to screen the spatial voxel grid,and the total calculation time has been reduced from the original 72 hours to 5 hoursThe effect of the 3D reconstruction is:the spatial resolution of the 3D reconstruction of the plasma of the volume1.804×10~7 mm~3 can reach 20mm;the spatial resolution of the 3D reconstruction of the partial plasma of the volume8.8×10~6 mm~3 can reach 10mm.Therefore,this paper fulfills the requirements of non-contact,omni-directional,high-precision 3D reconstruction of plasma intensity.