filename     : Papas12.pdf
entry        : toappear
conference   : ACM SIGGRAPH ASIA 2012, Singapore, Singapore, 28 November - 1 December, 2012
pages        : to appear
year         : 2012
month        : December
title        : The Magic Lens: Refractive Steganography
subtitle     :
author       : Marios Papas, Thomas Houit, Derek Nowrouzezahrai, Markus Gross and Wojciech Jarosz
booktitle    : 
ISSN/ISBN    : 
editor       : 
publisher    : ACM
publ.place   : Singapore
volume       : 
issue        : 
language     : English
keywords     : Steganography, Image Morphing, Lens Fabrication
abstract     : 
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.