Laser Scanner Reads Air Writing

A new method for inputting text into a personal digital assistant or mobile phone could have folks writing in the air instead of pointing with a stylus or typing on a keyboard. The Smart Laser Scanner prototype, designed by research fellow Alvaro Cassinelli and his team at the University of Tokyo, tracks finger motion and could be used to recognize letters written in the air.

Conversely, the technology can work to output letters onto any surface - you could read your email in the palm of your hand. According to Cassinelli, the system doesn’t require a person to use a stylus, special markers, or gloves like those needed with other gesture-capturing technology.
 
In addition, his apparatus could be shrunk down to the size of a computer chip and installed in electronic devices, freeing up space previously occupied by keyboards or screens and allowing engineers to create button-sized computers. “Just wave in the air in front of one of the buttons of your jacket,” said Cassinelli.
 
The technique uses a laser, an array of moveable micro-mirrors, an instrument that detects light called a photodector, and special software written by Cassinelli’s team to collect finger-motion data. The laser sends a beam of light to the array of micro-mirrors, which redirect the laser beam to shine on the finger tip.
 
A photodector senses light reflected off the finger and works with the software to minutely and quickly adjust the micro-mirrors so that they constantly beam the laser light onto the fingertip. The tracking system works in a way similar to how a blind person might use a cane to sense objects in the environment. Instead of swinging the cane indiscriminately around the environment, small, localized tapping movements are performed around objects.
 
The laser beam behaves similarly when it touches something of interest, in this case, the finger. The mirrors move the beam around in rapid circular motions to maintain contact with the finger as it moves through the air.
 
Because the beam performs nearly 1,000 circular motions each second, the finger appears, to the laser, to be moving extremely slowly and therefore is very easy to track. “Not only does it figure out where the finger is, it can display text or a graphic on that object. That is really a nice ability,” said Thad Starner, assistant professor of computing at Georgia Institute of Technology and an expert in gesture-recognition technology.
 
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