Natural light holography: possible approaches and current examples

Michael K. Finegan
Creative Engineering, NYC, USA
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Keywords: holography, digital holography, laser, pulse-laser, stereogram It is desired to create holographic images of outdoor scenes, both still life and figure. Target applications are both artistic and scientific. Pulse laser holography allows for the capture of outdoor scenes, for a restricted field of view determined by coherence length and power output. It has been applied specifically to human and animal portraits, but not extended natural scenes. It has typically been limited to monochrome information. Stereograms (and kinetic holograms) allow for film frames to be stored in a full color hologram [1], with each frame mapped to a portion of the angular field of view. For a stereogram, the intent is to simulate the three dimensional nature of what was filmed. This mapping is typically along one view axis only, providing horizontal parallax but not vertical parallax. A camera array (similar to what commercial motion picture studios now have) could be used to digitize in full parallax, but this has not yet been linked to digital holography. This approach does not capture the complete light field but rather a plane of viewpoints at a fixed distance from the subject. Examples will be given where this fails to provide adequate reconstruction. Digital holography from a computer model can provide the same result without the complex exposure geometries [2] and reconstructing the entire light field – but requires the outdoor scene to be digitized in 3D. Commercially available three dimensional color digitizers exist, but have practical restrictions regarding field of view, depth and resolution. In each example, digital data has to be created, manipulated and then rendered in full color for all three dimensions. In both cases, the effective geometry of the film capture has to correspond exactly to the geometry of the holographic rendering. While full parallax stereograms are possible, they are only just appearing [3]. Geometries, camera configurations and issues will be discussed both for natural and artificial 3D input to digital stereograms. Finally, a novel method is presented that allows natural light holography of outdoor scenes with unconstrained field of view or depth. The method relies on a conversion of incoherent natural light to coherent laser light using available optical components. This approach is contrasted with existing holographic techniques. A new optical component (similar to DLP micro-mirror components) would be required for this approach. A system architecture and component level design will be presented. Examples of digital stereograms of natural scenes and the corresponding capture geometries will also be discussed. One application of outdoor natural light holography that intrigues me is to save your favorite landscapes and present them in a faux window. In a futuristic world maybe ‘wallpaper’ can be digital holography of natural scenes. References Benton, S. A., “Survey of holographic stereograms”, Proceedings of the SPIE, Vol. 367, 1982, pp.15-19. Klug, M. A., Klein, A., Plesniak, W., Kropp, A., Chen, B. “Optics for full-parallax holographic stereograms”, Proceedings of the SPIE, Vol. 3011, 1997, pp. 78-88 Gentet, Yves, “Beau Dieu”,