利用频谱相位最大值自适应定位全息正一级频谱

Adaptivly locating holographic positive first-order spectrum using maximum value of spectral phase

为了解决正一级频谱区域定位方法依赖先验模板或参考光波倾斜角的问题,提出一种利用频谱相位最大值自适应定位全息正一级频谱区域的方法。对预放大数字全息的频谱相位分布进行了理论分析,获知频谱相位的最大值处于正一级频谱的中心位置。利用频谱相位的最大值点与全息频谱振幅的三个区域(正一级、负一级和零级频谱区域)重心的最小距离,判定和定位全息正一级频谱区域。最后,以微孔阵列、相位台阶为样本进行了实验。实验结果与理论分析一致,该方法测量相位台阶的横向误差为3.7μm,高度标准偏差为4.2%,能准确地定位正一级频谱的区域位置,而不依赖于先验模板或参考光波的倾斜角,为离轴全息频谱滤波提供了一种频谱区域自适应定位方法。

The region localization methods of the positive first-order spectrum rely on the prior template or the tilt angle of the reference wave,which can be problematic. Therefore,a new method for locating the positive first-order spectrum that uses the maximum spectral phase value is proposed. The theoretical distribution of the spectral phase in pre-magnified digital holography is analyzed,which reveals that the maximum phase point is located in the center of the positive first-order term spectrum. Furthermore,the minimum distance between the centroids of the three regions(positive first-order spectrum,negative first-order spectrum,and zero-order term spectrum)and the maximum phase point is used to judge and locate the positive first-order spectrum region. Finally,using a micro-hole array and phase step as examples,experiments are carried out,the results of which are consistent with the theoretical analysis. Specifically,they demonstrate that the absolute error is 3. 7 μm,and the standard deviation of depth is 4. 2% when measuring the phase step. Therefore,the proposed method can accurately locate the positive first-order spectrum region. Moreover,it does not depend on the prior template or the tilt angle of the reference wave,which provides an automatic spectrum localization method for spatial filtering in off-axis digital holographic microscopy.