Sjödahl Mikael, Picart Pascal
Appl Opt. 2024 Mar 1;63(7):B104-B113. doi: 10.1364/AO.510753.
In digital holography and holographic interferometry, refocusing to the correct image plane can be challenging and may be obtained by various metrics. This paper proposes a digital refocus approach utilizing the linear relationship between in-plane speckle motion and defocus as a response to an induced phase gradient. The theory based on cross-correlations between pairs of intensity images reconstructed at different distances from the recording plane is discussed. Two simple metrics, based on the cross-correlation properties of the reconstructed speckle images, are proposed and evaluated utilizing both simulations and experiments. Experiments exhibit similar trends in which the estimate of the correct reconstruction distance differs by a small amount between the two metrics. The difference is found less than 1% in the estimate of the true reconstruction distance. The results show that either metric is able to yield a sufficient reconstruction distance for the reconstruction of the image plane.
在数字全息术和全息干涉测量中，重新聚焦到正确的像平面可能具有挑战性，并且可以通过各种指标来实现。本文提出了一种数字重新聚焦方法，该方法利用面内散斑运动与离焦之间的线性关系来响应诱导的相位梯度。讨论了基于在距记录平面不同距离处重建的强度图像对之间的互相关的理论。提出了两种基于重建散斑图像互相关特性的简单指标，并通过模拟和实验进行了评估。实验呈现出相似的趋势，即两个指标对正确重建距离的估计相差不大。在真实重建距离的估计中，发现差异小于1%。结果表明，任一指标都能够为像平面的重建提供足够的重建距离。
