基于参考透镜法的数字全息显微相位畸变校正技术

Compensation of the Phase Aberrations in Digital Holographic Microscopy Based on Reference Lens Method

建立了数值与物理方法结合的参考透镜法,对离轴数字全息显微系统进行畸变相位校正.对离轴全息图进行频谱分析,通过频谱滤波、移位的数值方法对一次相位畸变进行校正.在参考光路中引入参考透镜,根据频谱中心能量判别参考透镜的轴向最佳位置,利用物理方法对多次相位畸变进行校正.在相位校正理论分析的基础上,结合实验用参考透镜法验证其有效性和准确性.微台阶表面形貌测量结果表明,参考透镜法能够准确校正相位畸变,通过校正的相位可以获取44nm标准微台阶形貌数据,测量标准差能够达到0.8nm,且测量结果与轮廓仪测量结果一致.表明参考透镜法能够有效、准确地校正离轴数字全息显微系统的畸变相位.

In order to correct phase aberrations in the digital holographic microscopy measurement system, a numerical method combined with physical method, namely reference lens method is applied in off-axis digital holographic microscopy system. Firstly, the frequency spectrum of digital hologram is analyzed. By filtering and displacing a part of spectrum, the first-order phase aberration is corrected. Then, the reference lens is introduced in reference path. The axial best position of reference lens is discriminated according to the spectrum center energy. By using this physical method, high-order phase aberration is corrected. Based on the analysis of the phase correction theory, the validity and accuracy of the reference lens method is verified by the combined experiment. The experimental results show that the method of reference lens can accurately correct phase aberration. The standard deviation can reach 0.8 nm. And the measured results agree with measurement results of mechanical profiler, showing that reference lens method can effectively and accurately correct phase aberration of off-axis digital holographic microscopy system.