Method of characterizing an object including, at least locally, a plane of symmetry

1. A method of characterizing an object that includes, at least locally, a plane of symmetry, the method comprising:

performing at least one observation of an ultrasound wave transmitted through the object by a first ultrasound transducer and received by a second ultrasound transducer, each observation being performed on an observation axis perpendicular to the plane of symmetry, each observation including:

emitting of the ultrasound wave generated by the first ultrasound transducer along a transducer axis of the first ultrasound transducer and meeting the object along the transducer axis of the first ultrasound transducer at an angle of incidence other than normal, the ultrasound wave meeting the object to follow a path to the second ultrasound transducer that is symmetrical relative to the plane of symmetry, and

receiving the emitted ultrasound wave following the path by the second ultrasound transducer;

determining a travel time of the emitted ultrasound wave, and/or a position of the transducer axis and a position the observation axis; and

characterizing the object based on the travel time of the emitted ultrasound wave and/or the position of the transducer axis and the position of the observation axis.

2. A method according to claim 1 , wherein the first and second ultrasound transducers positioned on a common axis are shifted while emitting the ultrasound wave and observing the emitted ultrasound wave, at least two waves selected from a longitudinal wave, a transverse wave, and a Rayleigh wave are transmitted and received, and observations are made on at least two waves selected from the longitudinal, transverse, and Rayleigh waves.

3. A method according to claim 2 , wherein observations are made on all of three waves from the longitudinal, transverse, and Rayleigh waves, and the method further comprises determining speeds of the longitudinal, transverse, and Rayleigh waves, and validating the determined speed of the Rayleigh wave based on the speeds of the longitudinal and transverse waves.

4. A method according to claim 2 , wherein the characterizing of the object includes determining Poisson's ratio and Young's modulus of the object.

5. A method according to claim 1 , wherein, for the object having a second plane of symmetry perpendicular to the plane of symmetry, the first and second ultrasound transducers positioned on a common axis are shifted on either side of the second plane of symmetry while emitting the ultrasound wave and observing the transmitted ultrasound wave, and two longitudinal waves or two transverse waves are observed on opposite sides of the second plane of symmetry.

6. A method according to claim 1 , wherein the at least one observation is made of at least one Rayleigh wave created at a surface of the object by the ultrasound wave meeting the object.

7. A method according to claim 1 , wherein the first and second ultrasound transducers are immersion ultrasound transducers.

8. A method according to claim 1 , wherein the object has a surface that includes at least one arc of an ellipse.

9. A method according to claim 8 , wherein the surface includes at least one arc of a circle.

10. A method according to claim 1 , wherein the object is a bearing ball or roller.