A device for sensing a motion of a deflectable surface includes a deflectable element having a first side beam deflectable and includes a reflective surface at a second side of the deflectable element, proposing the first side. The device includes an optical emitter for emitting an optical signal towards the reflective surface and an optical receiver for receiving a reflected optical signal from the reflective surface and for providing a reception signal based on a reflective optical signal. The device includes a control unit in communication with the optical receiver for determining information related to the motion of the deflectable element based on the reception signal.