Digital holography reconstruction algorithms to estimate the morphology and depth of non-spherical, absorbing particles

In digital holography an object wave is numerically reconstructed from a recorded hologram. Using this technique it is possible to detect the position and size of particles in a 3D domain. In this work, particular focus is placed on quantification of particles with non-spherical morphologies. The in-line configuration is chosen due to the simplicity of the optical setup and minimal distortions of in-plane morphologies. However, this geometry is also characterized by a large depth-of-focus and high uncertainty in the detected depth. To quantify these uncertainties, this work begins with the definition of a non-dimensional model of hologram recording and reconstruction applied to single spherical and non-spherical particles. Typical CCD noise sources are included. Application of this model to two particle detection methods reveals the relevant merits and limitations of each particle detection method. From the lessons learned, a new hybrid particle detection method is proposed. Simulations indicate the hybrid method significantly improves upon the accuracy of the measured depth and particle morphologies. Furthermore, the proposed method automatically determines the optimum threshold for each particle, and, therefore, requires minimal user inputs. Finally, initial experimental results for spherical particles confirm the accuracy of the proposed hybrid method.