PZD ( Piezo Drive)
Ultrasonic motors are divided into two categories depending on the principle that generates the energy to move the drive: traveling wave motors and standing wave motors. Traveling wave motors include the ring type ultrasonic motor used in the recently launched 70-300mm F/4-5.6 VC USD. as well as other lenses, but this lens employs a newer technology, the PZD ( Piezo Drive), which functions on the standing wave principle.
A standing wave ultrasonic motor utilizes high-frequency voltage to extend and turn the piezoelectric (piezoceramic) element, thus moving the entire element in a standing wave movement. A metal tip on the piezoceramic element is elliptically rotated by the rotary movement of the element and in turn drives the rotor by means of friction. Standing wave ultrasonic motors have the distinct advantage of being smaller than their traveling wave counterparts, and therefore allow a more compact SLR lens size.
The Tamron Piezo Drive distinguishes with its precise, fast and silent autofocus.