Lyncée Tec SA, PSE-A, CH-1015 Lausanne, Switzerland.
Opt Lett. 2010 Jun 1;35(11):1840-2. doi: 10.1364/OL.35.001840.
A recurrent problem in microscopy is the finite depth-of-focus linked to the NA of microscope objectives. Digital holographic microscopy (DHM) has the unique feature of being able to numerically change the focus from a single hologram without the need of moving the sample. Extended depth of focus of amplitude images has been demonstrated, but it has marginal interest for the metrological application of DHM that needs the topography. In this Letter, we demonstrate that DHM is able to provide not only extended depth-of-focus amplitude images but extended focused complex data from which the topography is computed. For this purpose, reflection and transmission measurements on micro-optics (microlens and retroreflector) performed by using standard reconstruction or the extended focused complex data are compared. These experiments demonstrate that DHM measures, from a single hologram acquisition, the accurate sample topography on a numerically increased depth-of-focus.
显微镜中的一个常见问题是与显微镜物镜的数值孔径相关的有限景深。数字全息显微镜 (DHM) 具有独特的功能，能够从单个全息图中通过数字方式改变焦点，而无需移动样品。已经证明了振幅图像的景深可以扩展，但是对于需要形貌的 DHM 的计量应用，其只有很小的意义。在本信中，我们证明 DHM 不仅能够提供扩展景深的振幅图像，而且还能够提供扩展聚焦的复数据，从而计算出形貌。为此，通过使用标准重建或扩展聚焦的复数据对微光学元件（微透镜和逆反射器）进行反射和透射测量，比较了这些测量方法。这些实验证明，DHM 能够从单个全息图采集，在数字上增加景深的情况下精确测量样品的形貌。
