Nano USM is a compact ultrasonic motor that achieves high-speed AF. It first appeared in 2016 in the EF-S18-135mm f/3.5-5.6 IS USM. Through vibrational energy from ultrasonic waves, it moves in a straight line along a slider and enables high-speed AF by moving the focus lens, which is coupled with a rack-like component, in the direction of the optical axis. Suited to highly precise micro-movements, it is a revolutionary AF actuator that delivers high performance for video and for shooting in Live View mode.
Nano USM was first used in an L lens in the RF24-105mm F4 L IS USM. Developed to be thin enough to fit into the confines of the lens barrel, it was built into the lens in the pursuit of compact design. The newly designed model of Nano USM eliminates the spring that had applied pressure to a piezoelectric ceramic element from the back side. In its place, springs are positioned in the four corners of the unit to achieve significantly greater thinness while maintaining high-torque properties. Capable of driving the focus unit at high speed and stopping it with precision, the Nano USM enables high-speed autofocus for still images. For video, it achieves smooth and silent focus drive, ready to take on any creative intent.