Estimation of particle depth from two defocused images using the Fourier transform  

作　　者：Wu Zhou Xu Luo Benting Chen Yukun Zhang Xiaoshu Cai 

机构地区：[1]School of Energy and Power Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China [2]Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering,Shanghai 200093,China

出　　处：《Particuology》2020年第2期48-54,共7页颗粒学报（英文版）

基　　金：The authors gratefully acknowledge support from the National Natural Science Foundation of China(51576130,51327803);the Basic Research Program of Major Projects for Aeronautical and Gas Turbines(2017-V-0016-0069);the Educational Development Foundation of Shanghai Municipal Education Commission(14CG46).

摘　　要：Depth from defocus is one technology for depth estimation.We estimate particle depth information from two defocused images captured simultaneously by two coaxial cameras with different imaging distances.The images are processed with the Fourier transform to obtain the characteristic parameter(i.e.,the standard deviation of the relative blur kernel of these two defocused images).First,we theoretically analyze the functional relationship between the object depth and the standard deviation or variation of the relative blur kernel.Then,we verify the relationship experimentally.We analyze the influence of particle size,window size and image noise on the calibration curves using both numerical simulations and experiments.We obtain the depth range and accuracy of this measurement system experimentally.For the verification experiments,we use a sample of glass microbeads and the irregularly-shaped dust particles on a microscope slide.Both of these experiments present a suitable depth measurement result.Finally,we apply the measuring system to the depth estimation of drops from a small anti-fogging spray.The results show that our system and image processing algorithm are robust for different types of particles,facilitating the in-line three-dimensional positioning of particles.

关 键 词：Depth from two defocused images Fourier transform Standard deviation of relative blur kernel Drops depth measurement Sensitivity and accuracy analysis 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术]