A novel method is proposed for non-contact measurement of the distribution of electrostatic charge on
a surface based on scanning the sample surface with a focused high frequency acoustic beam to excite
movement of the sample surface. An electric field is induced by exciting a charged film-like object, and
an electric field sensor measures it instead of an electrostatic field. The focused ultrasound waves are
generated by controlling individually the phase of each 285 airborne ultrasound transducers.