Nano USM
The Nano Ultrasonic Motor (USM) is a small ultrasonic motor that enables high-speed AF. It was first released in 2016 with the EF-S18-135mm f/3.5-5.6 IS USM lens. Using vibrational energy from ultrasonic waves, the motor moves in a straight line along a slider. The position of the focus lens, which is mounted on a rack-like component, can be precisely adjusted along the optical axis, allowing for high-speed autofocus. This revolutionary AF actuator's extremely precise micro-movements enable the lens to achieve high-performance autofocus for both still photography and video recording. In 2018, a new type of Nano USM was introduced for the first time in an L-series lens. The new Nano USM has been miniaturised to fit within a compact lens barrel, reducing the lens's overall size to the greatest extent possible. It was initially featured on the RF24-105mm f/4L IS USM lens.
The Nano USM's new design eliminates the spring that used to apply pressure to a piezoelectric ceramic element on the back. This structure has been replaced with springs at the unit's four corners, resulting in a significant reduction in thickness while maintaining high torque. The Nano USM can drive a lens at high speeds and precisely stop it, allowing for high-speed autofocus when taking still photos. When shooting films, it achieves a smooth and nearly silent focus for a variety of expressive purposes.