05-30-2012 12:38 PM
I haven't found one. One thing I have seen is that devices with autofocus do seem to focus while the scanned image changes. As long as there is movement (like the image getting closer and farther away), autofocus is active. Once the image stops moving, autofocus/scanning stops as well.
Possibly the bigger issue is devices with fixed focus lenses. There are quite a few of them.