利用物体波前中含有振幅和相位信息这一特征,提出将物波前中的振幅与相位信息相结合作为数字全息再现像的焦平面判定依据。利用强度图像这一振幅的直接表现形式来对数字全息再现像的焦平面进行定位是当前的主流方法,其中,相关系数法又是众多基于强度图像进行判焦的优异方法。通过将位相信息运用于相关系数法中,取得位相的相关系数曲线峰值也能确定焦平面距离。模拟分析表明同一物体的振幅相关系数曲线和相位相关系数曲线峰值所确定的焦平面距离有一定差距。因此,利用加权因子将物体的振幅相关系数曲线和相位相关系数曲线峰值所确定的焦平面距离加权来确定物体的焦平面,可以进一步提高焦平面定位精度。分析讨论了加权因子的取值,获得了最佳的焦平面,并通过实验验证该方法,确认了其有效可行。
A novel approach taking advantage of both amplitude and phase information to detect a focal plane for particles is presented. The primary approaches of detecting focus plane are based on amplitude analysis which is only one piece of object information. The correlation coefficient (CC) method which has been proved on amplitude analysis is useful for phase analysis as well and has been validated in the paper. A weighting coefficient is used to combine the distance from amplitude and phase analysis together because of the difference on them. The weighting coefficient is dis- cussed to obtain a good focal plane. The effectiveness of the method has been validated in the experiments.