People are always looking for new ways of interaction to computer. So far keyboard and mouse are still the most reliable and common way to do so. Of course touch screen is another wide spread method of user input. All of those require physical touch to device in order to enter info. But there are many areas where we would like to manipulate things from distance. Possible applications could be hazardous areas, wet or other places where it would be better to control things, enter information from distance without touching anything.
Magiciant have been experimenting with ultrasonic radar based user input. All you need is to draw with pen in the air in front of ultrasonic sensor and information is captured in to computer screen. Hardware setup is accessible to anyone because it is based on popular Arduino DUE, four HC-SR04 ultrasonic sensors and four channel MCP6024 buffer amplifier. Other magic is inside software where Fast Fourier transform does quite a job. Out of four ultrasonic sensors only one sends pulses while all four capture reflection. By combining collected information system is able to distinguish objects about 5cm apart and 12um depth. Effective working distance can be up to 3m. Update frame rate may be set from 10Hz to 60Hz.