首先从理论上推导准相干或宽带光照明下空间光干涉光场的分布,由此可得准相干或宽带光照明下的四步相移法。其次,通过搭建绿光空间光干涉显微镜(SLIM)系统,以直径为6 μm的聚苯乙烯微球分散于显微镜物镜用油模拟细胞的微环境。最后,利用4幅SLIM图像成功重建出油浸微球的相位分布,平均半径相对误差为6.5%,光程差体积相对误差为8.4%。由于相干光的四步相移法和宽带光的四步相移法重建结果相差较小,因此,在追求成像速度的场合且细胞厚度较小时,可不对四步相移法进行修正,以加快相位重建的速度。

In this study, we first derive the light field distribution for the spatial interference with quasi-coherent or broadband light illumination, so as to obtain a four-step phase shift corrected method for such an illumination. Second, we construct a spatial interference microscope system that uses green light and diluted 6-μm polystyrene microsphere into the microscopic objective oil to simulate microenvironment of a cell. Finally, using four of the spatial-interference images, we reconstruct the phase distribution of the oil-immersed microspheres. The relative error in the microsphere radius is 6.5%, and the relative error of optical path difference volume of the oil-immersed microsphere is 8.4%. By comparing these results with those achieved by the traditional four-step phase shift method, the improvement can be neglected. Therefore, in situations where the imaging speed is important and the observed cell is sufficiently thin, it is not necessary to use the corrected four-step phase-shift method to increase the imaging speed.