Ultrasonic Silent Drive Technology In Tamron Lenses

Many of Tamron's lenses feature Ultrasonic Silent Drive technology, such as the SP 70-200mm and SP 90mm Macro. 

The USD in Tamron's lenses enables them to auto-focus both fast and smoothly. The focusing ring, which is attached to a rotor at the back of the lens, is made to rotate by high frequency ultrasonic vibrations. 

The high-frequency ultrasonic vibrations that cause the rotor to move are produced by a ring called the stator. Ultrasonic vibrations are caused when a voltage of a specific frequency is applied to an element called piezoelectric ceramic. This is arranged in a ring formation on the stator, which causes two ultrasonic vibrations to occur. 

By combining the two ultrasonic vibrations produced, it is possible to create an energy called deflective traveling waves by converting the energy from the vibrations. 

The waves produced on the stator produce force, which turns the rotor, which is in turn linked to the focusing ring lens, making for a smooth movement.