Technology Of Image Scanning For Detecting Precipitation

Precipitation's physical parameters play an important role in areas such as weather modification, weather observations and weather radar calibration, etc. A precipitation scanning method based on linear CCD is proposed. The following work has been done to verify the feasibility of the new method:1 Scattering characteristic of precipitation was studied theoretically Optical characteristic of precipitation was analyzed theoretically. According to the boundary diffraction theory, edge diffraction effects of raindrops are derived and numerical simulations were carried out. This work provides theoretical guidance for shadow detecting of precipitation based on linear CCD.2 several key subsystems were designed, and then the whole experimental system was built.The experimental system includes three hardware subsystems: laser diode beam collimation-expanding system, driving circuit for linear CCD, data acquisition system. To meet light source requirements of the detection system, the matching between CCD requirement and illumination was analyzed, and then laser diode was selected to be used as the light source. Transmission characteristics of Gaussian laser beam and thin lens transformation were studied. Based on simulation in ZEMAX, a collimation-expanding system, whose amplification factor can reach 5.97, was designed. The timing requirement of linear array CCD-TCD1209D was analyzed. Based on CPLD, the driving circuit for CCD is designed. The simulation results on the Quartus II show that the driving circuit satisfies the timing requirement of CCD. A DSP-based high-speed data acquisition board was designed. Hardware and software design of the acquisition system are described in detail.3 the functions of all the subsystems were verified experimentally. Beam characteristic of the light source subsystem was analyzed using beam analyzer. The results show that the beam divergence angle and homogeneity of the parallel linear light meet the light source requirement. The CCD driving circuit was tested, and it fulfils the timing requirement of the CCD. The CCD driving circuit also offers a sampling signal to data acquisition system. The data acquisition system was proved work well. The entire system was built up and preliminary experiments were carried out. It is proved that the whole system can work well. Grayscale images of several simulation particles were recovered preliminary.