As Avatar pushes forward the acceptability of 3D cinema and 3D television is becoming a reality, the EU’s research and development programme, Framework Programme 7 (FP7), is funding the Real 3D project with the objective of taking digital holography to the point where it, too, can become a realistic method of delivering moving images in true 3D. As Thomas Naughton, the project’s scientific leader explained to Holography News®, what differentiates this project from others dealing with digital holography is its focus on capturing and delivering 3D images of actual objects.

Real 3D is a €5.87m project, with a €4.5m grant from FP7, which involves nine organisations - primarily academic research centres - working to establish ‘digital holography for 3D and 4D real-world objects’ capture, processing and display.’ Started in early 2008, the project is due to complete in January 2011. It is co-ordinated by Oulu Southern Institute at University of Oulu in Finland, and other participants are: Electrical and Electronics Engineering Department at Bilkent University (Turkey); the National Institute for Optical Applications (Italy); the Advanced Photonics Laboratory at the Ecole Polytechnique, Lausanne (Switzerland); the Department of Computer Science at the National University of Ireland, Maynooth; the Institute of Micromechanics and Photonics, Warsaw University of Technology (Poland), Bremer Institut für Angewandte Strahltechnik (Germany), Lyncée Tec (Switzerland) and Holoeye Photonics, Germany - the last three being the only commercial organisations involved.

Real 3D is based on the premise that holography is the only genuinely three-dimensional medium which does not require glasses or other ‘interpreting’ equipment. The project is addressing the restrictions that to date, full 3D holography is static, and that stereograms and other moving or animated conventional stereo displays only provide horizontal parallax, do not provide motion parallax, or are restricted in number of simultaneous viewers. The Real 3D summary points out that the full implications of bringing digital holography ‘into the world of 3D video acquisition and 3D display… are as yet unknown.’ The project aims to eliminate current obstacles to achieving a fully functional system for 3D video capture, processing, and display ‘for unrestricted viewing … with full perspectives of the 3D scene.’ Multiple sensors and displays will be integrated, and both microscopic and macroscopic 3D scenes are being addressed.

Naughton, who is Senior Lecturer, National University of Ireland, Maynooth, and Marie Curie Fellow, University of Oulu, told Holography News that the project is on-track, and participants have presented or published numerous papers on work or developments which have been part of Real 3D. An example is a paper titled Color Holographic Reconstruction Using Multiple SLMs and LED Illumination by Fahri Yaras and Levent Onural of Bilkent University, which shows that Real 3D is approaching the issue using reflective type phase-only spatial light modulators (SLMs) and red, green and blue LEDs for reconstruction.

SLM-LED Combination

This paper reports the use of an iterative algorithm using Fresnel propagation to calculate in-line phase holograms, to be displayed on three phase-only SLMs illuminated by three LEDs - ie red-green and blue matching pairs to give full-colour reconstruction. Red, green and blue channels are separately controlled by a computer graphic card for display on the respective SLMs, which are supplied by Holoeye.

Compared to laser illumination, LEDs offer the benefits of low cost, low power, no retinal danger and no speckle, although they don’t have the coherence of laser beams. But filtered through a pinhole and then expanded they deliver acceptable results, as can be seen in the illustration. The three images are combined using beam splitters, mounted on optical stages to allow precision positioning. The integration of suitably post-processed digital holograms of real-world objects is the next step, says Naughton.

Naughton revealed that they have already made some encouraging discoveries and insights. Problems they were concerned about at the start of the project included the integration of multiple uncalibrated cameras and multiple displays, laser speckle and other inherent noise in holograms of real-world objects, and the anticipated huge processing power needed to handle true 3D moving images, but they have found that the human visual perception system compensates for some of these issues. These results will appear in Year 2 progress report to the EC (to be released in May) and in peer-reviewed papers.

Contact: www. Digitalholography.eu