Digital recording and numerical reconstruction of holograms

Abstract

This article describes the principles and major applications of digital recording and numerical reconstruction of holograms (digital holography). Digital holography became feasible since charged coupled devices (CCDs) with suitable numbers and sizes of pixels and computers with sufficient speed became available. The Fresnel or Fourier holograms are recorded directly by the CCD and stored digitally. No film material involving wet-chemical or other processing is necessary. The reconstruction of the wavefield, which is done optically by illumination of a hologram, is performed by numerical methods. The numerical reconstruction process is based on the Fresnel-Kirchhoff integral, which describes the diffraction of the reconstructing wave at the micro-structure of the hologram. In the numerical reconstruction process not only the intensity, but also the phase distribution of the stored wavefield can be computed from the digital hologram. This offers new possibilities for a variety of applications. Digital holography is applied to measure shape and surface deformation of opaque bodies and refractive index fields within transparent media. Further applications are imaging and microscopy, where it is advantageous to refocus the area under investigation by numerical methods.

Particle imaging techniques for volumetric three-component (3D3C) velocity measurements in microfluidics

“…With smaller pixel size and higher sensitivity of CCD chips, a technique was developed to digitally record holograms and reconstruct the object numerically (Schnars and Jüptner 1994). A comprehensive review on digital recording configurations and numerical reconstruction techniques can be found in Schnars and Jüptner (2002). An overview of the holographic PIV technique with a detailed discussion of rising problems is given by Hinsch (2002).…”

Single-pixel digital ghost holography

“…The invention of the laser boosted the field and the first practical three-dimensional (3D) holograms were achieved [2]. Recording interference patterns with a chargecoupled device (CCD) led to the development of digital holography, where the intensity and phase of the electromagnetic field are measured, stored, transmitted, and manipulated with the aid of a computer [3]. Digital holography is currently a ubiquitous diagnostic and metrological tool [4,5].…”

Self-calibration for lensless color microscopy

“…The conventional way to reconstruct a hologram is based on simulations of hologram diffraction by backpropagation [12,13]. However, the reconstructed planes are affected by many artifacts (edge effects, twin images, presence of out-of-focus objects, etc.).…”