Tuesday, November 13, 2012

Image projection via caustics -- wow!

I just came across a method for projecting a monochrome still image that is stunning in both its simplicity and efficiency. Developed at École Polytechnique Fédérale de Lausanne (EPFL; Lausanne, Switzerland), the method relies on an acrylic projection "slide" that has nothing embedded within it and nothing printed on it, but instead has a surface shaped to be slightly uneven.

Place it at the right point between a reasonably small, bright light source and a wall, and an image appears. The image is formed from the "caustics" that arise when an optically smooth but rippled surface slightly and unevenly deflects light, producing lighter and darker areas (such as what you see at the bottom of a swimming pool on a sunny day).

Form the ripples in the right way, and you can project whatever image you want -- such as this image of Alan Turing, the British mathematician and father of modern computer science, shown in the light of an ordinary white LED.

Credit: (c) Alain Herzog

The surface shape to provide a specific image is calculated via an algorithm. Because this type of projection doesn't rely on absorption, the process is virtually lossless. Almost any transparent item could be made into a projector -- windows, display cases, architectural ornamentation, vases, glasses, jewelry, and so on.  See this EPFL Youtube video for more.

Researchers in EPFL's Computer Graphics and Geometry Laboratory showed working image-projecting caustic plates recently at the Advances in Architectural Geometry Conference in Paris. Contributors to the project include Mark Pauly (EPFL), Thomas Kiser (EPFL), Michael Eigensatz (Evolute; Perchtoldsdorf, Austria ), Minh Man Nguyen (WAO Architecture; Paris, France) and architect Philippe Bompas.

Thursday, November 8, 2012

Telepresence to go microscopic?

A couple of weeks ago (on Halloween, in fact), I posted a news story to Laser Focus World about "telepresence" robots crafted especially to allow people to attend corporate meetings; the remote attendees wear head-mounted displays and other devices, while at the other end their physical robot avatars sit at the meeting, displaying facial expressions and waving their hands impatiently.

However, this is only the beginning. A group of European and American scientists recently created a somewhat similar telepresence system, except that the meeting consisted of one human and one rat.1 The human, who wore an eye-tracking head-mounted display, was represented by a rodent-sized robot that allowed the person to communicate with the rat on its own scale; the rat, tracked by two stereoscopic cameras, was represented to the human as a humanoid avatar on a computer screen. The human got to play carefully scripted games with the rat; the rat got to play along and occasionally receive a dab of jam for a reward.

So what's next? Well, back in the 1960s, a science-fiction movie, Fantastic Voyage, was based on the implausible idea of shrinking a submarine and a few people to microscopic size and injecting the sub into someone's body so that the crew could find and eliminate a blood clot. It made little sense then, but telepresence could make this sort of thing a reality (minus the teeny humans).

For example, the "Pillcam," invented by Given Imaging (Yoqneam, Israel) more than ten years ago and now moving toward FDA approval, is swallowed by a patient and moves naturally through the patient's gastrointestinal tract looking for polyps, conceivably eliminating the need for a colonoscopy. Such devices could be made smaller -- perhaps much smaller -- and could possibly be steered or even self-propelled, delivering drugs or doing microsurgery. As for photonics hardware, an extreme version of a camera-on-a-chip would be needed for vision, and other (perhaps plasmonic) sensors would be a must. Or the devices could be tracked using optical coherence tomography (OCT). Or . . .

Rats, I have to get back to work.


1. Jean-Marie Normand et al., PLOS ONE (2012) doi:10.1371/journal.pone.0048331.