Computer Graphics Laboratory ETH Zurich


The Magic Lens: Refractive Steganography

M. Papas, T. Houit, D Nowrouzezahrai, M. Gross, W. Jarosz

Proceedings of ACM SIGGRAPH Asia (Singapore, November 28 - December 1, 2012), ACM Transactions on Graphics, vol. 31, no. 6, pp. 186:1-186:10


Motivated by classical steganography techniques we construct Magic Lenses, composed of refractive lenslet arrays, to reveal hidden images when placed over potentially unstructured printed or displayed source images. We determine the refractive geometry of these surfaces by formulating and efficiently solving an inverse light transport problem, taking into account additional constraints imposed by the physical manufacturing processes. We fabricate several variants on the basic magic lens idea including using a single source image to encode several hidden images which are only revealed when the lens is placed at prescribed rotational orientations or viewed from different angles. We also present an important special case, the universal lens, that forms an injection mapping from the lens surface to the source image grid, allowing it to be used with arbitrary source images. We use this type of lens to generate hidden animation sequences. We validate our simulation results with many real-world manufactured magic lenses, and experiment with two separate manufacturing processes.

The Magic Lens: Refractive Steganography

Marios Papas1,2 Thomas Houit1 Derek Nowrouzezahrai1,3 Markus Gross1,2 Wojciech Jarosz1
1Disney Research Zürich 2ETH Zürich 3University of Montreal

In ACM Transactions on Graphics (Proceedings of ACM SIGGRAPH Asia 2012)

We automatically design and manufacture magic lenses to warp source images into meaningful target images. Here we photograph a source image (far left) viewed through a manufactured lens with 32×32 facets (left), resulting in four images depending on the lens’ rotational orientation atop the source.


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