Focusing a lens requires moving the lens back and forth. That's the way it has been for over 100 years. This is even true with Nikon's SWM (silent wave motor) and Canon's USM (ultrasonic motor), where the mechanism for moving the lens back-and-forth is quiet.
Today I just stumbled on the following news that a company raised $30 million dollars to create cameras that can autofocus without mechanical movements! You apply voltage to a lens that changes the refractive index. WHOA!!!!!! I've heard lenses that can change opacity by applying voltage, but changing refractive index is a first for me. Imagine, if this is possible on a teeny-weeny scaled lens, who knows what the future of big lens technology will be like in another 100 years? In the 22nd century, we'll probably look back to 2010 and laugh at the $8000.00 super 600mm f/2.8L/G FX SWM/USM auto focus lens that weighs 999 tons.
