Linear measuring devices feed back

[wtherapy]

Hello,

I'm a newbie in the field ( perhaps my title sounds a little bit confusing ) but this is what I need to do:
create a hobby cnc lathe by attaching stepper motors and stuff to an Optimum 180x300 lathe ( that is closed to a 7x12 inch lathe ) and I want to attach it a device that automatically tracks the movements. That is, I need to know ( or my computer needs to know ) any time what are the coordinates on each axis.
I have found several linear encoders such as Easson, Optimum, Haidenhein:

http://www.top-maschinen.de/digitale...2000/index.htm
http://www.top-maschinen.de/digitale...muem/index.htm

( scroll bellow the displays )

http://www.bzt-cnc.de/product_info.p...549317c46f2df4

etc

I don't need the display as the computer processes the coordinate information. The question: how is the signal taken from the linear encoder to the computer? My best option would be to enter it in a microcontroller, A/D converter ( I don't know even if it's digital or analogic signal ). Has anyone did such a thing?
Any help appreciated. Thanks

[rustamd]

why not use servos?

[wtherapy]

Hello,

don't know much about servos, BTW, I need to do small, precise parts ( such as miniature brushless motors ).

[wtherapy]

the main idea with the linear encoders is to eliminate ( better said, to measure and react against ) backlashes and plays in the threads, so I thought the best approach is to use an independent measurement device.

[justCNCit]

same question I had some time ago, everybody showed me how expensive those parts are.

had a hard time believing it b/c the mills at school use these kind of encoders & I can't see how they could cost that much. they look pretty simple to me