rough digitizing using proximity sensors

A few weeks ago we were talking about making
(or retrofitting) our own digitizers. At that time,
I suggested a digitizing "roughing" pass would enable
optimal trajectory planning for the "finishing" digitizing
pass.

In the MSC 2000/2001 catalog (http://www.mscdirect.com )
page 3932 from Omron there is a:

"convergent beam photo-micro sensor" $37.52

both side and end facing sensors
2 to 6mm sensing distance
0.2 mm differential distance at 3 mm sensing distance
100 Hz response frequency
takes 5-24 Volts

As a non-contact means of probing, perhaps appropriate
algorithms can be developed to rough digitize (here, rough might
mean 0.2 mm) at maximum feed rates.

Doug Fortune