Today's optical manufacturing industry is facing increasing pressure on cost, quality, and delivery performance. There is also in an environment of decreasing batch sizes, a move towards higher tolerances - usually for very quality conscious customers. A frequent response is to invest in new manufacturing technology. The alternative discussed here is to focus on improving the underlying processes.
David J. Smith,
"Manufacture of optical components under statistical process control", Proc. SPIE 3739, Optical Fabrication and Testing, (6 September 1999); doi: 10.1117/12.360135; https://doi.org/10.1117/12.360135