Research On Scanning Method Of Nano-CT System

To meet the requirements of scientific research and actual production, the industrialCT resolution requirements are developing from micron grade scale to nano-scale, theimaging accuracy and detection efficiency of the CT system are required higher andhigher. The development of the scanning system of ultra-high precision is one of thesubprojects of Nano-CT instrument exploitation. The precision of scanning systemdirectly influences the quality of image reconstruction and the accuracy of measurement,and the price of the scanning system directly affects the cost of the instrument. Thescanning methods of Nano-CT is studied in this paper, in order to ensure accuracy andreduce cost.The developments of Nano-CT, system principle and application field arepresented in this thesis, and the principle, merits and demerits of traditional and modernCT scan are analyzed in detail. In view of higher requirements for tested object’s size,imaging accuracy and detection efficiency in Industrial nondestructive testing andbiomedical field at present, a static scan method of Nano-CT is proposed in this paper.Time-sharing scanning technology of line array radiation source is used in thisscanning methods, replacing the traditional mechanical rotation to obtain the differentangle data, and achieving the scanning of detected objects in the static condition. Notonly it eliminates the influence of mechanical rotating accuracy, but also reduces thescan time, and improves the imaging precision of CT scan. But the scanning methodrequires high repositioning precision turntable and the scanning synchronization controlaccuracy. Because of asymmetric and heterogeneous characteristics of geometriclocation for static scan, projection data can only be obtained within the scope of thelimited point of view for CT system. In view of the finite angle issue, the feasibility ofimage reconstruction is discussed in this paper.Line array radiation source is still in research stage at present, without the listedproducts, so the emulation of time-sharing scanning method of line array radiationsource becames another key and difficult points. For the sake of resolving this puzzle, ahigh speed and high precision positioning platform is designed in this paper, to getcommand of the single focus X-ray source translation scanning movement, simulatingtime-sharing scanning of Line array radiation. Positioning platform adopts hybrid Driveway, coarse positioning platform is driven by linear motor, and precision positioning platform is driven by piezoelectric ceramic. First of all, the modeling and simulation ofcoarse positioning platform are done, the simulation results show that the coarsepositioning platform has good stability and dynamic performance, and the accuracy is inmicron scale. Due to nonlinear hysteresis characteristics of piezoelectric ceramics, themodeling and simulation of precision positioning platform of the compensation for thehysteresis compensation and hysteresis are done, the simulation results show thatprecision positioning platform after compensating, Compared to platform withoutcompensation, these is no overshoot, no oscillation, and stable time is short, stableprecision can be from micron grade reduced to the nanoscale, the theoretical foundationis laid for achieving static scan method by Line array radiation source later.