[sdiy] Laser knobs

[Richard Wentk]

At 11:09 04/05/2004 -0700, Tim Parkhurst wrote:


>On the laser based PDA interface:
>More info:
>http://www.palminfocenter.com/view_story.asp?ID=6394
>This is a device that attaches to your PDA and scans a flat surface with a
>diode laser. It looks for interference patterns and can figure out which key
>you're pressing on the projected keyboard.

Is it definitely based on interference patterns? Naively I'd have thought 
you'd get enough position information by timing any back-scattering wrt 
beam location. (Which, so far as I know, is more or less how barcode 
scanners work.)

I'm definitely curious about this item. If anyone has links to patents or 
other relevant details, I'd be very interested.

Richard