The Silent Wave Motor, or SWM, is an ultrasonic autofocus motor developed by Nikon. Nikon's SWM converts "traveling waves" into rotational energy to drive the optics used for focusing. Any AF-S NIKKOR lens featuring the SWM delivers extremely smooth, quiet and comfortable auto focusing. Among the first lenses for which Nikon adopted the SWM was the Ai AF-S Nikkor 300mm f/2.8D IF-ED, released in 1996. In the fourteen years since its initial release, total production of NIKKOR lenses equipped with the SWM has reached twenty million.
Since its introduction, the SWM has been built into a total of 54* different lenses of all types, from ultra wide-angle to super telephoto DX- and FX-format lenses, zoom lenses, and micro lenses. Since 2007, more than 90% of NIKKOR lenses have been equipped with the SWM.
* Total number of NIKKOR lenses equipped with the SWM released since its introduction (As of September 15, 2010)