US 12,072,407 B2
Methods and apparatuses for distance measurement
Dimitri Torfs, Stuttgart (DE); Hugo Embrechts, Stuttgart (DE); and Gonzalo Bailador del Pozo, Stuttgart (DE)
Assigned to SONY CORPORATION, Tokyo (JP)
Filed by Sony Corporation, Tokyo (JP)
Filed on Jul. 31, 2019, as Appl. No. 16/527,019.
Claims priority of application No. 18187572 (EP), filed on Aug. 6, 2018.
Prior Publication US 2020/0041633 A1, Feb. 6, 2020
Int. Cl. G01S 11/14 (2006.01)
CPC G01S 11/14 (2013.01) 19 Claims
OG exemplary drawing
 
1. A distance measurement system, consisting of:
an electronic device having a first transmitter and a first receiver; and
a wearable electronic device having a second transmitter and a second receiver, the wearable electronic device being different from the electronic device,
wherein the first transmitter and the second receiver are clock-synchronized to each other,
wherein the first transmitter is configured to emit an ultrasonic signal at a plurality of predefined transmit times, the predefined transmit times being known to the first transmitter and the second receiver at an initial time of emitting the ultrasonic signal, the predefined transmit times each being a multiple of 100 ms,
wherein the second receiver is configured to receive the ultrasonic signal and to calculate a distance between the first transmitter and the second receiver based on the received ultrasonic signal and the known predefined transmit times,
wherein the first transmitter and the second receiver are configured to share a symmetric cryptographic key prior to emitting the ultrasonic signal,
wherein the electronic device is configured to encode a first number of bits based on a current transmit time and the shared symmetric cryptographic key and to modulate the ultrasonic signal based on the encoded bits,
wherein the wearable device is configured to
calculate a second number of bits based on the known predefined transmit time of the received ultrasonic signal and the shared symmetric cryptographic key, and
compare the calculated second number of bits to the encoded first number of bits of the received ultrasonic signal, and
wherein the electronic device is configured to, responsive to detection of the wearable electronic device being worn and being within a predetermined distance away from the electronic device, unlock the electronic device for use by a user.