Method and system for beam control in biometric sensing

1. A sensor comprising:

an ultrasonic sensor array including sensing elements;

a control unit configured for controlling, with respect to a position in a 3D space associated with a finger of a person in physical contact with the sensor:

a first set of transmitting sensing elements of the ultrasonic sensor array for transmitting ultrasonic signals to the finger, wherein transmission of the ultrasonic signals from at least two transmitting sensing elements of the first set are offset in a first time interval such that the ultrasonic signals from the at least two transmitting sensing elements arrive at the position at approximately a same time, and

a second set of receiving sensing elements of the ultrasonic sensor array for receiving amplitude signals caused by redirection of the ultrasonic signals received by the finger at the position, wherein reception of the amplitude signals by at least two receiving sensing elements of the second set are offset in a second time interval such that the amplitude signals arrive at the at least two receiving sensing elements at approximately a same time; and

a 3D representation forming unit configured for obtaining a three-dimensional representation of a subcutaneous structure inside the finger based on the amplitude signals received at respective receiving times.

2. The sensor of claim 1 , wherein the offset in the first time interval is in accordance with a distance between the at least two transmitting sensing elements and the position in the 3D space.

3. The sensor of claim 1 , wherein the offset in the second time interval is in accordance with a distance between the at least two receiving sensing elements and the position in the 3D space.

4. The sensor of claim 1 , wherein the amplitude signals and their respective receiving times are reflective of the subcutaneous structure and at least one parameter thereof.

5. The sensor of claim 1 , wherein the control unit is configured for controlling a first set of electrical connections with respect to the transmission of the ultrasonic signals and a second set of electrical connections with respect to the reception of the amplitude signals.

6. The sensor of claim 5 , wherein the first set of electrical connections is orthogonal to the second set of electrical connections.

7. The sensor of claim 1 , wherein a first set of the amplitude signals corresponding to 3D positions of a boundary of the subcutaneous structure is greater than a second set of the amplitude signals corresponding to a 3D position internal or external to the subcutaneous structure.

8. The sensor of claim 1 , wherein the control unit configured to operate the ultrasonic sensor array in a first mode or a second mode, wherein

in the first mode, the control unit is configured to obtain a two-dimensional representation of the finger based on acoustic energy transmitted and received by the sensing elements of the ultrasonic sensor array, and

in the second mode, the control unit is configured to obtain the three-dimensional representation.

9. The sensor of claim 1 , wherein the subcutaneous structure is a bone structure within the finger.

10. The sensor of claim 1 , wherein the subcutaneous structure is a vascular structure within the finger.

11. The sensor of claim 1 , wherein the three-dimensional representations of the subcutaneous structure are used to determine a dynamic property of the subcutaneous structure.

12. The sensor of claim 1 , wherein the dynamic property includes an elastic property of the subcutaneous structure.

13. The sensor of claim 1 , wherein the dynamic property is used to determine liveness of the person.

14. The sensor of claim 13 , wherein the dynamic property is used to measure a heartbeat.

15. The sensor of claim 13 , wherein the dynamic property is used to measure a blood flow through a vascular structure.