基于离轴干涉原理和共光路结构布局, 设计和搭建了以激光作为光源的衍射相位显微成像系统, 在未放样品的情况下, 测得该系统的平均噪声误差仅有6.70 nm.利用标称直径为4.8 μm的标准聚苯乙烯微球来检验该系统检测的准确性, 测量误差与理论预期结果相比不超过4%.用该系统测量100只贾第鞭毛虫包囊个体, 并重建贾第鞭毛虫包囊的相位图, 在相位图的基础上, 估算出每个贾第鞭毛虫包囊的干质量.对测量结果进行统计分析, 结果表明贾第鞭毛虫包囊呈椭圆形状, 长轴范围为8~15 μm, 短轴范围为4~7 μm, 包囊的干质量在42.70~137.07 pg之间.该衍射相位显微成像系统采集速度快、准确性高, 可以满足对单个寄生虫形态和干质量进行定量分析的需求.

Based on the principles of off-axis interferometry and common-path geometry, a laser diffraction phase microscopy system is designed and built up, and the spatial noise standard deviation of the system without sample is measured as 6.70 nm. Standard polystyrene spheres with diameter of 4.8 μm are used as the calibration samples, the measured phase shift error does not exceed 4% compared to the expected results. 100 Giardia lamblia cysts are measured using this system and the unwrapped phase images are reconstructed, the dry mass of each cyst is estimated on the basis of phase image. Statistical analysis results indicate that shape of Giardia lamblia cysts appear to be elliptical, the major and minor diameters of cysts range from 8μm to 15 μm and 4 μm to 7 μm respectively, and the dry mass is calculated to be in the range from 42.70 pg to 137.07 pg. The proposed diffraction phase microscopy has a fast acquisition speed and a high accuracy and can meet the requirements of the quantitative analysis of morphology and dry mass of the single protozoan parasite.