Short-coherence digital holography for the investigation of 3D microscopic samples

摘要

An optical system based on short-coherence digital holography suitable for three-dimensional microscopic investigations is described. An in-line arrangement is used, in which the light source is a short-coherence laser and the holograms are recorded on a CCD sensor. The interference (hologram) occurs only when the path lengths of the reference and the object beam are matched within the coherence length of the laser. The phase of the object wave front in the plane of the CCD detector is determined by phase shifting. The image of the part of the sample that matches the reference beam is reconstructed by numerical evaluation of the hologram. The three-dimensional scanning of the sample is easily obtained by shifting the position of a mirror in the reference arm of the interferometer. Reconstruction of different layers of the sample is possible up to a depth of several hundred micrometers. However, in tissues and other biological samples, while the surface of the sample is properly reconstructed, the multiple scattering and the inhomogeneties in the refractive index reduce the imaging quality of the deepest layers. The possibility to correct numerically this sample-induced aberrations has been studied. Simulations and experimental results are presented.