基于全息图放大的数字全息显微结构测量

针对典型预放大数字显微全息光路中存在的二次位相误差，本文设计了基于全息图放大的数字全息显微光路。此设计中，光束首先照射透明显微物体，然后与平行参考光干涉，形成全息图，最后经显微镜获得放大的全息图。这种光路从系统上直接消除了主要由球面波引起的位相畸变，有利于数字处理及实时化。作者以位相光栅(30 lines/mm，槽深约0.3 µm)作为实验样本，对此光路进行了分析研究，并分别用菲涅耳近似法和卷积法再现单幅全息图，同时获取了物体的强度信息和三维位相信息，位相深度的计算结果为0.27 µm。结果表明本文设计的光路对二次位相产生的离焦误差有明显的抑制作用。

Micro-structure measurement of phase object by digital microholography based on magnified hologram

A digital micro-holographic optical system based on magnified hologram is designed. Compared with the typical pre-magnification system, the proposed system directly eliminates the main phase error introduced by spherical wave before record. In the post-magnification system, the object beam interferes with the parallel reference beam to generate hologram. A microscope is used to magnify the hologram and then recorded by a CCD camera. This method intends to be more useful to the post numerical reconstruc-tion and real-time operation because of no quadratic phase aberration. The system is studied by the experiments with the phase grating (30 lines/mm, about 0.3 µm depth). Besides, Fresnel approximation and convolution algorithm are respectively used to reconstruct amplitude and phase information of the micro sample. Phase depth is about 0.27 µm. The results show that the present system is greatly helpful to restrain the quadratic phase error.