Electric Field Imagaing

Electric Field Imaging:
"Seeing" by Inverse Electrostatics

Josh Smith

Overview of Electric Field Sensing

Electric Field Sensing lets machines inexpensively sense in 3 dimensions, with high precision and fast update rates. For user interface applications, the user does not have to wear or hold anything, because the technique directly measures the bulk conductivity of the human body. It does not require a line of sight to the body being measured---thus a device can see what its user is doing, right through a plastic case.

In the last year of my Ph.D., I finished development of the LazyFish, a tiny electric field sensing board with 8 measurement channels. The demodulation is done in software on a microcontroller, using a technique I call synchronous undersampling. The LazyFish is designed to be embedded in handheld devices...though it can be used as an input device to a conventional computer, the typical application I imagine is one in which there is *no PC.* For example, I also designed (with Josh Strickon) a tiny MIDI synthesizer and Sequencer board, the Mini Midi, which was used in the Musical Jacket Project. The LazyFish could be used as the controller for this synthesizer.

Before the LazyFish, I developed the School of Fish, a distributed, scalable implementation of Electric Field Sensing. In my PhD thesis, I present algorithms for inferring body geometry from field measurements, and implement them with data collected by the School of Fish. The thesis explains how to extract the available geometrical information from any sized electric field sensing array. A single channel provides a touch sensitive button; a few channels enable a 3d mouse, and many channels enable a kind of imaging.