re: using optical mouse for DRO / servo feedback

Just come through from Farnell electronics (a distributor) on the new
products is an optical mouse sensor for use on "a surface", it just reads
the surface, be it a mouse pad, a bit of desk-top, an envelope (or possibly
a dusty rail), and uses an on-chip camera and some signal processing to give
400-800 counts per inch x and y. Quadrature or serial outputs, etc. maximum
speed of motion it says are 12 inches per second.
anyway manufacturer is AGILENT, and part number is
ADNS-2051, looks promising

Nig