基于全息图放大的数字全息显微结构测量

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

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,设计了基于全息图放大的数字全息显微光路。首先用光束照射透明显微物体,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,有利于处理的数字化及实时化。以位相光栅(30 lp/mm,槽深约0.3μm)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,位相深度为0.27μm。实验结果表明,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。

A digital micro-holographic optical system based on magnified hologram was designed. Compared with the typical pre-magnification system, the proposed system directly eliminated the main phase error caused by spherical wave. In the post-magnification system, the object beam interfered with the parallel reference beam to generate hologram,and a microscope was used to magnify the hologram recorded by a CCD camera. This method is more useful to the post numerical reconstruction and real-time operation for its no quadratic phase aberration. A experiment with the phase grating （30 lp/ mm, about 0.3μm in depth）was carried out, Fresnel approximation and convolution algorithm were used to reconstruct the amplitude and phase information of a micro sample,respectively, phase depth about 0.27 μm was abtained. The experimental results show that proposed system is greatly helpful to restrain the quadratic phase error.