More questions !!

Sorry - something more popped into my mind:

Something is nagging me ! A while back - sorry I don't remember
who said it - they said something about linear and rotary encoders.
Something like - there is a problem, you can't replace a linear
encoder with the rotary on the motor. Why not ?

And to Jon Elson, - I remember your laser for PCB artwork, and
have wanted to ask what kind of resolution you have on this ?

The thing is: Is 8 or 16 mm movie films still available ? You
could make miles of linear encoders ! You could add index pulse,
gray or V-scan areas if you like. As far as I know, - the frames on
the film, is made by the shutter. That is, the film is in fact
blank. With index, you could correct some with lookup tables. (
gray coding may be useful here )
Put on a reflective bar, then you could also use reflective opto
sensors. The area available is large, so there should bee plenty of
room for them.

It was just a thought - but I have had it in the back of my mind for
a long time.

//ARNE