The cheapest way you can achieve is using encoder wheel.
First, go --> http://www.mindspring.com/~tom2000/Delphi/Codewheel.html
You can find a link to the basic knowledge of encoder wheel.
There is also a software that will generate a wheel patern for you to cut.
But for that resolution you want .. you'll need to go to the laser cut shop .. and they can not accept the bitmap format generated by the software above.
Here it come the help for that situation
Go --> http://www.thingiverse.com/thing:1527
It have a poscript file that you can edit with text editor , preview it in gimp, and bring to laser cut shop.
Now , the limit is your ability to align the optical parts.
Have a nice hack (errrgghh .. alignment)