Research On Influencing Factors Of Measurement Accuracy For Micro-CT System

Micro-CT has the advantages of non-destructive detection,high resolution imaging and micron scale measurement.It is widely used in micro-electronics,material chemistry,petroleum geology and other research fields.The accuracy of reconstructed image quality,voxel size and quantity is the key to ensure the effective measurement results when Micro-CT is used for measurement.The ideal system geometry pose is the basis of Micro-CT imaging.However,the installation and positioning geometric parameters of instruments and equipment may be deviated,resulting in the quality of reconstructed images.At the same time,the main component of the Micro-CT system is located in the lead box.Influenced by the environment and long working time,the temperature in the box may change,and the thermal expansion property of the material causes the quality of the reconstructed image to decrease,thus affecting the measurement accuracy of the Micro-CT system.In addition,when the sample size is measured according to the reconstructed image,the determination of voxel size and quantity is related to the system geometric parameters,image edge extraction and other factors.Therefore,it is especially important to improve the measurement accuracy by improving the measurement method to accurately determine the size and quantity of voxel.In this paper,the geometric pose,temperature,measurement method that affect the measurement accuracy of the Micro-CT system are studied.The main work is as follows:1.A geometric pose correction method that can be directly corrected by using projected images is proposed,and the corresponding correction calibrator is designed for experimental verification.The method uses the projection data of the calibrator collected by the detector at a fixed projection angle.Then the method marks the spherical coordinates of the calibrator and its position relation on the actual detector to correct the system posture.It improves the reconstructed image quality.2.The appropriate ambient temperature of the Micro-CT system is evaluated,and the corresponding scanning parameters are optimized.The main heat source in the system is analyzed and the error correction temperature module which can be used in the Micro-CT system is designed.Under different experimental conditions,the temperature of the Micro-CT system is measured for several times in different positions to ensure that the temperature of the sample is basically constant.The measured results are modified with the thermodynamic parameters of the materials.They improve the environmental stability and measurement reliability of the Micro-CT system.3.Combined calibrator and sample measurement method is adopted to design combined combined calibrator: CT circular tube and CT square tube,and a method to correct scale error and threshold error in the measurement process of Micro-CT system is proposed.For the commonly used lightweight material polytetrafluoroethylene(ptfe),the experiment is carried out to measure the unidirectional distance and bidirectional distance.The experimental results are compared with other measurement methods in terms of measurement accuracy,occupation time and memory,showing obvious advantages.