Replication Process Explained
The optical replication process is an established technique for producing complex surfaces accurately and cost effectively. It is a process that is ideally suited for medium to high volume production of complex surfaces such as diffraction gratings, hollow retroreflectors, freeform mirrors, off-axis parabolic mirrors (OAPs), elliptical mirrors and toroidal mirrors. A surface quality of λ/10 or better is often achievable.
The process starts with an original or master optic which is very similar to the required finished product with the same specification. Often a customer’s existing part can be used as a master, saving on engineering costs.
This master is coated with a release agent and then an epoxy mixture before being bonded to a second part – the negative master or sub-master – which is coated with an adhesive. The epoxy layer moulds itself to the master taking on the exact profile and surface quality. The epoxy layer is cured (hardened) using heat or UV light and then the master and negative master are carefully separated.
Because the master has been treated with a release layer and the negative master with an adhesive layer – the epoxy layer is transferred to the negative master. The negative master now has a profile that is a perfect “negative” of the required part.
The final process is where the profile from the negative master is transferred to the replica substrate. The replica substrate (which can be glass, aluminum, stainless steel, beryllium, silicon carbide, plastic or other materials) is coated with an epoxy mixture and the negative master is then used to “stamp” the profile required into the epoxy layer on the substrate. The epoxy layer is cured (either by heat or UV light) and the result is a finished replicated part that is ready for coating.
The quality of the finished part and its optical performance is indistinguishable from the original or from parts manufactured using conventional manufacturing techniques. For large or complex parts, the cost savings can be quite dramatic – often up to about half the cost of conventionally manufactured optics.
The replication process also offers the capability of replicating onto metal substrates that already incorporate tabs, mounting holes or brackets to produce an integrated mounted optic – cutting down on the number of parts required, decreasing alignment and mounting time as well as reducing weight and increasing stability.
Our current manufacturing gives us the capabilty of replicating up to 12 inch (300mm) diameter parts.