| CPC G06F 3/04186 (2019.05) [G06F 3/043 (2013.01); G01S 15/02 (2013.01); G01S 15/08 (2013.01); G01S 15/12 (2013.01); G06F 3/03547 (2013.01); G06F 3/0383 (2013.01); G06F 3/0433 (2013.01); G06F 3/0436 (2013.01)] | 27 Claims |
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1. A touch sensor, comprising:
a housing having a recess;
a touch structure coupled to the housing and arranged over the recess such that the recess forms an enclosed interior volume, wherein the touch structure comprises a touch surface and an inner surface arranged opposite to the touch surface, wherein the inner surface faces towards the enclosed interior volume;
a temperature sensor arranged inside the enclosed interior volume and configured to measure a temperature;
a memory configured to store a plurality of sets of reference samples that each corresponds to a different temperature, of a plurality of temperatures, or a different range of temperatures of a plurality of ranges of temperatures;
a transmitter arranged inside the enclosed interior volume, wherein the transmitter is configured to transmit an ultra-sonic transmit signal towards the inner surface;
a receiver arranged inside the enclosed interior volume and coupled to the transmitter via a propagation path, wherein the receiver is configured to receive an ultra-sonic reflected signal produced from the ultra-sonic transmit signal and the propagation path; and
a sensor circuit, arranged inside the enclosed interior volume, configured to:
receive the temperature from the temperature sensor,
select, based on the temperature, a set of reference samples, of the plurality of sets of reference samples, to be used as a first plurality of reference samples,
receive the ultra-sonic reflected signal from the receiver,
acquire a plurality of digital samples, from the ultra-sonic reflected signal, within an observation window that starts at an expected time-of-flight of the ultra-sonic reflected signal plus a duration of the ultra-sonic transmit signal,
calculate a difference of each digital sample, of the plurality of digital samples, from a corresponding reference sample, of the first plurality of reference samples,
calculate a sum of the difference of each digital sample, the plurality of digital samples, from the corresponding reference sample, of the first plurality of reference samples,
determine a first Euclidean distance of the plurality of digital samples to the first plurality of reference samples based on the sum, and
determine whether a no-touch event or a touch event has occurred at the touch surface based on the first Euclidean distance.
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