On 9/02/06 8:40 AM, "Toralf Lund", <[EMAIL PROTECTED]> wrote:
> Both of which can come in packages that are identical to a traditional > DC motor, and could as far as I can tell be used in an in-body motor AF > system - which would cancel out the need for the traditional feedback loop. The version I described is nowhere near any traditional electric motor. It's a very clever use of the Piezo element, and some other people posted links to more detailed descriptions. It's sort of like a "worm" being Piezo element and the wave-like movement pushes and rotates the helicoids (or focusing ring). Re feedback loop, I too thought about this in terms of the positioning control, and it may not like traditional feedback loop with overshoot and correction to finally settle on the target point. USM having no overshoot, I think their control algorithm should be different. OTOH, I just have a feeling that the ultra accuracy might be difficult to obtain, as the feedback converges to a target focus, and enter into a certain range, it stops there. I can't think that this mechanism can make such a minute move toward the end of the motion. But it should be dependent on how finer movement tolerance a Piezo element is designed for. Gear drive like current Pentax's, while noisy, hunts and takes a bit longer time to settle and converge on the target focus, might be more accurate (but we are talking about very minute difference here). Cheers, Ken -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
