Focus Drift Correction Method For Micro-nano CT

In recent years,with the development of X-ray source technology and detection technology,micro-nano CT has gradually entered people's field of vision.As a highresolution non-destructive testing instrument,micro-nano CT has the advantages of small focus,high spatial resolution,fast detection speed,and good image quality.It is mainly used to detect the microstructure inside tiny objects,and has important application value in Biology and other fields.The spatial resolution of micro-nano CT can reach micron level or even sub-micron level.The study found that in addition to the main factors that affect the spatial resolution of micro-nano CT,such as the X-ray source focus size,detector pixel size,and scanning motion accuracy,the radiation source focus position drift also has an important effect on the CT image quality and spatial resolution.We have studied this problem and proposed a method based on projected image adaptive feature matching to achieve real-time effective focus drift correction.First,the simulation analyzes the effect of focus drift on the quality of the reconstructed image.It is demonstrated that the runout error of the micro-nano CT used in this paper is negligible relative to the focus drift,and the amount of focus drift can be inferred by the deviation of the projected image.Then,the effect of ambient temperature and ray source power on focus drift is analyzed by wireframe model.It is found that although ambient temperature has little effect on focus drift,ray source power has a great relationship with focus drift.In general,the amount of focus drift and the power of the ray source is positively correlated.Through experiments,it was found that the focus drift of the microfocus ray source is mainly the position drift caused by the thermal expansion of the target.It is concluded that the focus drift has certain repeatability and randomness,so it needs to be corrected in real time.At the same time,we found that the focus drift will stabilize after about 30 minutes of open source.Secondly,based on the above analysis,we propose a new correction method of micronano CT focus drift,that is,a method based on adaptive feature matching of the projected image.This method is improved on the basis of the reference scan compensation method.The innovative point is comparing the actual projection and the reference projection through the adaptive feature matching method to solve the focus drift.And we use the interpolated focus drift to compensate the actual projection,reconstructing the corrected image.A large number of experiments have verified the effectiveness of this method.And we compare the method we proposed with the reference scan compensation method based on phase correlation.The results show that the speed and correction effect of the focus drift of the method we proposed are better than the reference scan compensation based on phase correlation law.The method proposed in this paper has a fast solution to the focus drift of the ray source,accurate results,good correction effect,and simple operation.It can correct the image blur and distortion caused by the focus drift effectively,improve the quality of the reconstructed image effectively,and has a very good Engineering practicality.