Acoustic phase conjugation

[1] Acoustic imaging can be improved by applying selective phase conjugation on some harmonics of the incident wave.

This narrows the focal distribution of those harmonics and reduces the sidelobes and reverberation noise, thus increasing the image resolution.

[2] Selective acoustic phase conjugation can be used to detect isoechogenic objects whose nonlinear parameters differ from that of the medium.

The linear acoustic properties of such objects are close to that of the medium which make them invisible with traditional echography techniques.

[3] Another field of application is nonlinear ultrasonic velocimetry, one order of magnitude more precise than with the usual Doppler effect.