  In this paper, we present a conceptual design of a novel gesture-based
instruction/input device using wave detection. The device recogonizes/detects
gestures from a person and based on which to give the specific orders/inputs to
the computing machine that is connected to it. The gestures are modelled as the
shapes of some impenetrable or penetrable scatterers from a certain admissible
class, called a dictionary. The device generates time-harmonic point signals
for the gesture recognition/detection. It then collects the scattered wave in a
relatively small backscattering aperture on a bounded surface containing the
point sources. The recognition algorithm consists of two steps and requires
only two incident waves of different wavenumbers. The approximate location of
the scatterer is first determined by using the measured data at a small
wavenumber and the shape of the scatterer is then identified using the computed
location of the scatterer and the measured data at a regular wavenumber. We
provide the mathematical principle with rigorous justifications underlying the
design. Numerical experiments show that the proposed device works effectively
and efficiently in some practical scenarios.
