Digital cameras and camera-phones could capture 3D information using just an in-built flash and some clever software, say Japanese researchers.
Kazunori Umeda and Naoya Ogawa from Chuo University in Tokyo, Japan, were inspired by a prototype device made by electronics manufacturer Toshiba in 1999, called the Motion Processor.
It resembles a webcam surrounded by several infrared LEDs. It captures 3D information by recording the pattern and intensity of infrared light reflected by a scene. Since this depends to an extent on the distance and orientation of an object, it is possible to calculate simple things like roughly how far away it is and how it is positioned.
This made it possible for the Motion Processor to detect a user's hand gestures to control software. "Toshiba proposed the infrared system as an interface device for a PC – a kind of 3D mouse," explains Umeda. "Our aim is to add range measurement function to a standard digital camera."
To do this, Umeda's team used a consumer digital camera. They took pictures of simple objects with and without a flash activated. By mathematically subtracting the first image from the second it was possible to examine just the light reflected from the flash.
Image subtraction
Comparing the pattern and strength of this reflected light allowed them to estimate the distances to, and the relative angles of, different surfaces in a scene. The researchers tested the method using angled pieces of card (see image), and more complex scenes such as a whole room.
Their results show that a rough 3D model can reconstructed using the technique, although identifying some surfaces can be a problem. "A diffuse, white surface is easiest," Umeda told New Scientist, "and [reflective] surfaces are hardest - the worst is a mirror."
Umeda has not devoted much thought to potential applications, but says the system could perhaps be used to automatically pick out people in an image, by distinguishing them from the background.
The device currently estimates distances with an accuracy of around 6%. But the researchers say they can improve this by taking into account the way different parts of a scene are illuminated by a flash. For example, objects around the edge of a scene are not illuminated as well as those at the centre. Future research will also test whether they can create 3D images of more irregularly shaped objects.
http://www.newscientisttech.com/article/dn11776-camera-flashes-reveal-scenes-in-3d.html
