Use of digital holographic microscopy in tomography

摘要

Digital Holographic Microscopy (DHM) provides three-dimensional (3D) images with a high vertical accuracy in the nanometer range and a diffracted limited transverse resolution. This paper focuses on 3 different tomographic applications based on DHM. First, we show that DHM can be combined with time gating: a series of holograms is acquired at different depths by varying the reference path length, providing after reconstruction images of slices at different depths in the specimen thanks to the short coherence length of the light source. Studies on enucleated porcine eyes will be presented. Secondly, we present a tomography based on the addition of several reconstructed wavefronts measured with DHM at different wavelengths. Each wavefront phase is individually adjusted to be equal in a given plane of interest, resulting in a constructive addition of complex waves in the selected plane and destructive addition in the others. Varying the plane of interest enables the scan of the object in depth. Thirdly, DHM is applied to perform optical diffraction tomography of a pollen grain: transmission phase images are acquired for different orientations of the rotating sample, then the 3D refractive index spatial distribution is computed by inverse radon transform. The presented works will exemplify the versatility of DHM, but above all its capability of providing quantitative tomographic data of biological specimen in a quick, reliable and non-invasive way.