研究了用数字全息层析成像技术测量微毛细管结构的可行性。考虑毛细管具有理想的柱对称结构, 因此采用单幅全息图获取到的物光波复振幅数据来模拟不同角度下的投影数据。分别运用滤波反投影重建算法和傅里叶衍射重建算法对微毛细管进行折射率三维重构;根据重构的折射率切片图, 进一步运用相关的边缘提取算法处理得到毛细管的内径及壁厚尺寸。实验结果表明, 在合理的光路环境设置下, 满足Rytov近似条件下的傅里叶衍射重建算法比滤波反投影重建算法更能够正确反映物体的结构尺寸, 更适合用于微小弱散射物体的几何参数测量。实验结果验证了用数字全息方法实现衍射层析重建的可行性, 从而为具有柱对称结构的弱散射物体的无损测量提供了一种新的途径。

The feasibility to measure the inner diameter and wall thickness of a micro-capillary by using digital holographic tomography was explored. As the micro-capillary had an ideal cylindrically symmetric structure, the single reconstructed data under zero incidence angle were used to simulate all measured field data under different angles. A tomography was performed for the micro-capillary by a filtered back-projection algorithm and a Fourier diffraction algorithm respectively to reconstruct the 3-D map of refractive index. According to the 3-D distribution of refractive index, the size of inner diameter and wall thickness of micro-capillary were obtained by the related edge detection algorithm of image processing. Experimental results show that diffraction tomography based on the Rytov approximation can better response the dimensions of the micro-capillary than the filtered back-projection reconstruction algorithm for tiny weakly-diffracting objects under the condition of reasonable light path environment of the hologram recording. It proves that the digital holographic tomography can measure the inner diameter and wall thickness of the micro-capillary exactly and can provide a new way for the nondestructive measurement of tiny weakly-diffracting objects.