Force sensing in touch sensor by directivity control of transmit transducers

A touch sensor, comprising:

• a housing having an ultrasound port;
• a touch structure coupled to the housing and arranged over the ultrasound port such that the ultrasound port forms an enclosed interior volume, wherein the touch structure comprises a touch interface and an inner interface arranged opposite to the touch interface, wherein the inner interface faces towards the enclosed interior volume;
• an array of transceiver transducers arranged inside the enclosed interior volume, wherein each transceiver transducer is configured transmit a respective ultra-sonic transmit wave in response to being activated by a respective excitation signal, wherein a main directivity lobe directed at the touch interface is produced by at least one ultra-sonic transmit wave,
• wherein the array of transceiver transducers is configured to receive an ultra-sonic reflected wave produced at least in part by internal reflection of the main directivity lobe at the touch interface and convert the ultra-sonic reflected wave into at least one measurement signal;
• a controller configured to modulate an activation of the transceiver transducers to control a directivity characteristic of the main directivity lobe by selectively generating at least one respective excitation signal;
• and
• a receiver circuit configured to receive the at least one measurement signal, detect edges of a contact patch of a touch event present at the touch interface based on the at least one measurement signal, determine a size of the contact patch based on the detected edges, and determine an amount of contact force applied during the touch event based on the size of the contact patch.

A touch sensor, comprising:

• a housing having an ultrasound port;
• a touch structure coupled to the housing and arranged over the ultrasound port such that the ultrasound port forms an enclosed interior volume, wherein the touch structure comprises a touch interface and an inner interface arranged opposite to the touch interface, wherein the inner interface faces towards the enclosed interior volume;
• an array of transmit transducers arranged inside the enclosed interior volume, wherein each transmit transducer is configured to transmit a respective ultra-sonic transmit wave in response to being activated by a respective excitation signal, wherein a main directivity lobe directed at the touch interface is produced by at least one ultra-sonic transmit wave;
• an array of receive transducers arranged inside the enclosed interior volume and acoustically coupled to the array of transmit transducers, wherein the array of receive transducers receive an ultra-sonic reflected wave produced at least in part by internal reflection of the main directivity lobe at the touch interface and convert the ultra-sonic reflected wave into at least one measurement signal;
• a controller configured to modulate an activation of the transmit transducers to control a directivity characteristic of the main directivity lobe by selectively generating at least one respective excitation signal;
• and
• a receiver circuit configured to receive the at least one measurement signal, determine a size of a contact patch of a touch event present at the touch interface based on the at least one measurement signal and the directivity characteristic of the main directivity lobe, and determine an amount of contact force applied during the touch event based on the size of the contact patch.

A touch sensor, comprising:

• a housing having an ultrasound port;
• a touch structure coupled to the housing and arranged over the ultrasound port such that the ultrasound port forms an enclosed interior volume, wherein the touch structure comprises a touch interface and an inner interface arranged opposite to the touch interface, wherein the inner interface faces towards the enclosed interior volume;
• an array of transceiver transducers arranged inside the enclosed interior volume, wherein each transceiver transducer is configured transmit a respective ultra-sonic transmit wave in response to being activated by a respective excitation signal, wherein a main directivity lobe directed at the touch interface is produced by at least one ultra-sonic transmit wave,
• wherein the array of transceiver transducers is configured to receive an ultra-sonic reflected wave produced at least in part by internal reflection of the main directivity lobe at the touch interface and convert the ultra-sonic reflected wave into at least one measurement signal;
• a controller configured to modulate an activation of the transceiver transducers to control a directivity characteristic of the main directivity lobe by selectively generating at least one respective excitation signal;
• and
• a receiver circuit configured to receive the at least one measurement signal, determine a size of a contact patch of a touch event present at the touch interface based on the at least one measurement signal and the directivity characteristic of the main directivity lobe, and determine an amount of contact force applied during the touch event based on the size of the contact patch.