Tactile feedback generated by non-linear interaction of surface acoustic waves

A method comprising:

• selecting a delineated area of at least two delineated areas of a display surface in response to a detected touch by a human appendage to the display surface;
• delivering a first ultrasound wave to the selected delineated area, the first ultrasound wave transmitted by a first ultrasound transmitter acoustically coupled to an ultrasound-conducting layer of the display surface and configured to deliver the first ultrasound wave to the delineated area selected from the at least two delineated areas of the display surface, the first ultrasonic wave having a first carrier frequency and amplitude sufficient to induce a non-linear vibrational response of the ultrasound-conducting layer;
• and
• delivering a second ultrasound wave to the selected delineated area, the second ultrasound wave transmitted by a second ultrasound transmitter acoustically coupled to the ultrasound-conducting layer and configured to deliver the second ultrasound wave to the selected delineated area, the second ultrasonic wave having a second carrier frequency and amplitude sufficient to induce a non-linear vibrational response of the ultrasound-conducting layer,
• the parameters of the first carrier frequency and amplitude and the second carrier frequency and amplitude are such that a non-linear interaction of the first ultrasound wave and the second ultrasound wave at the selected delineated area produce a stress pattern tactilely perceivable or discernible by the human appendage.

A system comprising:

• means for selecting a delineated area of at least two delineated areas of a display surface in response to a detected touch by a human appendage to the display surface;
• means for delivering a first ultrasound wave to the selected delineated area, the means for delivering the first ultrasound wave acoustically coupled to an ultrasound-conducting layer of the display surface and configured to deliver the first ultrasound wave to a delineated area selected from the at least two delineated areas of the display surface, the first ultrasonic wave having a first carrier frequency and amplitude sufficient to induce a non-linear vibrational response of the ultrasound-conducting layer;
• and
• means for delivering a second ultrasound wave to the selected delineated area, the means for delivering the second ultrasound wave acoustically coupled to the ultrasound-conducting layer and configured to deliver the second ultrasound wave to the selected delineated area, the second ultrasonic wave having a second carrier frequency and amplitude sufficient to induce a non-linear vibrational response of the ultrasound-conducting layer,
• the parameters of the first carrier frequency and amplitude and the second carrier frequency and amplitude are such that a non-linear interaction of the first ultrasound wave and the second ultrasound wave at the selected delineated area produce a stress pattern tactilely perceivable or discernible by the human appendage.