Crystal-Clear Path to Advanced Encryption and High-Resolution Photography Published Sept. 18, 2009 By Maria Callier Office of Scientific Research ARLINGTON, Virginia -- Air Force Research Laboratory-funded research of unconventional imaging methods may prompt advancements for the Air Force, particularly in the areas of data encryption and wide-area, high-resolution photography. Princeton University's Dr. Jason W. Fleischer leads a team exploring the use of a special optical device for capturing images. The device (and the novel technique it enables) relies on a nonlinear crystal, rather than an ordinary lens, as follows. Every object--and thus, every potential image--comprises a collection of light waves. An ordinary lens bends (i.e., refracts) these waves towards a detector, whereas nonlinear material causes the waves to "talk" and interact with each other--a process which, in turn, generates new waves and distorts the ones that already exist. This wave mixing is actually a form of physical (as opposed to numerical) encryption, which is useless unless the process can also be reversed. Accordingly, the algorithm used by Dr. Fleischer's research team provides a way to "undo" the imaging process and thus recover the original signal. For signals already encrypted from the start, this new method serves as another layer of protection. The reversal algorithm also enables the capture of information that is lost during other imaging processes. Experimentally, the team's emergent method relies on imaging both the intensity and the travel direction of the waves, achieved by first taking a standard photograph of the object alone and then taking another that includes the object and an added plane of waves. The final step is to feed the result, called a hologram, into the numerical code. The researchers took photos of various objects using the image-capturing equipment associated with the nontraditional technique, and their images consistently reflected a wide field of view and high resolution. They confirmed these findings via an AF resolution chart, a specialized tool designed to check the quality of imaging systems. Potential applications for this emergent imaging technology include optical systems that maintain their field of view as they zoom, sharper microscopes, improved lithography, and dynamic imaging of three-dimensional objects. The researchers are now searching for new materials to increase wave mixing levels in order to realize stronger, faster interactions at lower light levels. This focus could later translate to a capability for taking multiple pictures simultaneously and performing faster image reconstruction than current computer processing permits.