"Folding" light again and again provides a lot of magnification in a small space
In 2003, a program funded by the Pentagon’s Defense Advanced Research Projects Agency (Darpa) known as MONTAGE asked universities to find ways to squeeze unprecedented levels of magnification and resolution from small, super-thin lenses—technology that could be used in future imaging devices for finding, tracking, and identifying military targets. With some advice from his adviser Joseph Ford, UCSD graduate student Eric Tremblay decided to use an old idea—”folding” light, or reflecting it over and over—to solve the problem. “Astronomers have been doing this for hundreds of years with telescopes,” says Tremblay (whose research on this problem was first mentioned in this magazine in May 2007). But doing it in a smaller space, he says, “required an extreme extension of the basic idea and would not have been possible without the recent maturity of modern fabrication techniques.” The essential technique is called single-point diamond turning, in which a computer guides a diamond-tipped lathe to cut lenses and optics to the dimensions set by a CAD model. By using diamond-turning, Tremblay, Ford and collaborators from the optical-design company Distant Focus were able to build a tiny optical system that folds light back on itself multiple times, like origami, instead of focusing it on a single point like a standard camera lens does. The result: “a lot of magnification in a really tight space,” Tremblay says.
WHAT’S NEXT Like most Darpa-funded research, the work has commercial as well as military potential. Tremblay says he’s a little more than a year away from an optic small enough for a cellphone: his smallest is 14 millimeters in diameter, and he wants to get to 10. Not surprisingly, Samsung and Motorola have come calling.
Inventor: Eric Tremblay, graduate student
University of California at San Diego