Digital-holografische Rekonstruktion der Oberflächenform (HoloReForm): Entwicklung eines mathematischen Modells zur Rekonstruktion von Oberflächenformen unter Verwendung eines einzigen digitalen Hologramms HoloReForm II)

• Applicant: Dr. Christoph von Kopylow
• Subject Area: Measurement Systems
• Term: from 2006 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 27070599

• Final Report Year: 2013

Final Report Abstract

In the course of this project, it could successfully be shown that the shape reconstruction problem in digital holography, i.e. extraction of 3D information from a single 2D digital hologram, can be formulated as an inverse problem thereby attaining a much better solution e.g. in terms of reduced cross-talk and improved accuracy. Hereby deconvolution inverse solutions were formulated and investigated. Following is a summary of the major findings and results of the project: • In the beginning a least square (LSQ) estimator for the inverse reconstruction of digital holograms based on a point source model, and one that utilizes gradient based algorithms to iteratively minimize an obective function was investigated. This approach was successfully applied to reconstruct a hologram resulting from light scattered by randomly distributed particles across a volume. • The LSQ approach was applied to reconstruct experimentally recorded digital in-line particle holograms. Various numerical experiments were also undertaken to assess the achievable accuracy and stability. The methods were also applied to determine the position and size of marine plankton in water. • A 3D deconvolution based method was investigated and compared to the LSQ method using the hologram of a synthetic object. The effect of speckle noise was also investigated. • To tackle the problem of multiple local extrema in the LSQ approach, a global optimization algorithm was adopted and a new autofocus scheme was implemented. The resulting method was investigated by reconstructing both experimental as well as numerical data.

Publications

• Digital Holographic System for the Imaging and analysis of living marine plankton interrelational Behavior, 3rd EOS Topical Meeting (on Blue Photonics- Optics in the Sea) Texel (2012) ISBN 978-3-9815022-5-1 (CD Rom)
  Kamau, E.N. ; Huke, P.; Bergmann, R. B.
  
• Point source based model for the inverse numerical reconstruction of digital holograms., EOS Annual Meeting Aberdeen (2012) ISBN 978-3-9815022-4-4 (CD Rom)
  Kamau, E. N.; Wang, N.; Falldorf, C.; v. Kopylow, C.; Bergmann, R. B.