I happened to visit the Makezine website one day and found out this interesting project, which requires one to only use some aluminium foils to do 3D tracking of the current location of our hand. Since mininal materials are required, I decided to build one touchless 3D tracking interface.
This 3D touchless interface actually uses the same concept on how a capacitive screen on a smartphone detects the a touched location: Capacitive Sensing. This technique takes the human body capacitance as an input, for example, when we touch the screen, it actually changes the state of the sensor. When there the person does not touch the screen, the electrostatic field will remain constant. As the person touches the screen, the capacitance of the sensor changes, which the sensor will register the location of the changed state & thus registering the location of the screen the user have touched.
How this device works?
The aluminium foils actually acts as a capacitor that stores charge when there is voltage across the foil. Hence, these foils are connected to the arduino to provide current and voltage to charge the foils. When your hands are nearer to the foil, the capacitance will be lower & the foil will take a shorter time to charge.
The original code is found here.