Ultrasonic Motor Enables Silent AF Operation Enjoy More Precise Control
Please tell us a little about the Silent Wave Motor employed in the AF drive.
Sure. Conventional AF lenses use something called a coupling drive. The DC motor inside the body serves as the drive source -- the body and lens are linked by gears, through which the force necessary to drive the autofocus mechanism are transmitted. The SWM, on the other hand, uses ultrasonic vibration to directly drive the lens.
How does the SWM work ?
- YAMAZAKI using diagrams to explain the operation of the SWM.
He uses a surfing analogy in order to break a technical concept down into the simplest terms possible.
"Ultrasonic" describes frequencies of mechanical vibrations that are inaudible to the human ear. When people converse, as you and I are, we can hear each other because the sound causes the air to vibrate. These vibrations spread out, or propagate, through the air, and are called "traveling waves".
In the SWM, ultrasonic traveling waves move in a spiral pattern inside the lens barrel. The motor is positioned on top of the waves, and they drive it from below.
Think of it this way: in surfing, the waves drive or push the surfer provided he's balanced atop them. It's the same with the SWM -- the motor is driven by the ultrasonic waves from underneath.
What are some of the difficulties you encountered in working with ultrasonic motor technology ?
Well, just like surfing, the hardest part is staying balanced on the wave!
In order to keep the vibration caused by the ultrasonic traveling wave headed in a set direction, we needed technology that would allow the creation of regular waveforms.
Nikon has been using SWMs in its products for about five years now, and from the very beginning our motors have delivered highly precise operation. Now we are focusing our efforts on providing the same performance at a lower price, making the products accessible to a broader range of customers.
What are the major advantages of the Silent Wave Motor ?
Just like the name says -- the motor enables silent autofocus operation.
But it's more than just quiet -- the mechanism drives the motor very smoothly and steadily, enabling highly precise control. Furthermore, the motor is in the shape of a cylinder, which allows it to fit nicely within the lens barrel.