Ultrasound diffraction-grating transducers produce beams at an angle to their face, which makes them useful for Doppler measurement of scattering fluids such as blood. The present invention discloses a diffraction-grating transducer, with the capability to focus transmitting or receiving beams to a desired point in space. This focusing capability leads to greater sensitivity when the diffraction-grating transducer is used as a receiver, and greater concentration of ultrasound energy when used as a transmitter. The focusing is achieved by using curved elements instead of the straight ones in conventional diffraction-grating transducers, and by using non-uniform spacing among these elements rather than the uniform spacing of conventional diffraction-grating transducers. Methods of computing the proper curvature of the elements and their spacing for a desired focal point in space are provided.
