Super cheap DRO

Hi all, I have played around with some idea's on DROs & I'm sure it
has all been done before, but for those newcomers to the forum it may
be food for thought that will trigger some idea's that may lead to
successful DROs in someones home shop. For encoders I used optical
mice. (the type that use photo diodes & slotted discs) they are
available free from computor repair shops (At least mine were, I was
given a bag with about 8 mice, 4 optical & 4 mechanical in it) I made
up a couple of cheek plates with spacers in between, like a small
clock, mounted the encoder disc on a small shaft (cut the shaft in
the middle, tapped 1 half 1/8 inch, threaded the end of the other
half a matching thread, drilled the disc 1/8 inch & sandwiched the
disc in between) mounted another shaft with a drum about 1 inch in
diam. between the cheeks & connected the two with a small square
section belt from a video recorder repair shop (the belt is about
0.080" cross section & 1 inch diam.)I cut small 90 degree V grooves
for the belt to run in. With a 0.020" stainless flexible stranded
cable (from fishing tackle shops) wrapped twice around the drum &
each end secured to the ends of a test track, as the trolly with the
encoder is traversed the encoder outputs one thousand quadrature
transitions for each inch of movement. I fed the pulses to a
quadrature decoder chip from Digital...? in the States, (they sell
encoders etc.) & then drove an up/down counter. Works O.K. The next
move (If I ever get the time)is to build a small clock spring into
the unit to retract the cable so that I can mount the unit on 1 end
of the machine & just have the cable exiting the housing via a swarf
seal & connnected to the slide/table etc. This should make for a
neater, easier, installation. The next move would probably be to do
away with the decoder and counter & feed the outputs into an old
computor with one of the programs in this forum (CAN ANYONE TELL ME
WHICH ONE TO USE?) this will give me 3 axis plus metric conversion
plus able to re-zereo & perhaps radius/diameter, also with a switch
box I will be able to select mill or lathe. I hope the above
ramblings are helpful to someone, Ian Sutherland.