The Encoder Designer Program was written to help design incremental encoder disks for use in robotics.

a circuit board could be etched with a pattern produced by an encoder design program. The disk would be mounted to a shaft with epoxy, T-NUT, or whatever creative means one found. By using a copper clad board, (the phenolic that we tested was IR invisible) the emitter detector pair would work fine with this disk mounted in the middle, however the reflective technique was easy with the copper. Once etched, spray it with lacquer to prevent the tarnish and you are on your way. It was also realized that paper, or a transparency could also be used as a substrate, and then attached the paper to any stiff disk.