Mechanical design implementation and mathematical considerations for ultra precise diamond turning of multiple freeform mirrors on a common substrate

For optical systems consisting of metal (in general freeform) mirrors there exist several diamond turning fabrication approaches. These are distuingished by the effort in manufacturing and integration of the later system. The more work one puts into the manufacturing stage the less complicated is the alignment and integration afterwards. For example the most degrees of freedom have to be aligned in integration phase if every mirror of the system is fabricated as a single optical component. For a three mirror anastigmat with three freeform mirrors the degrees of freedom sum up to 18. Therefore the mirror fabrication itself is more or less easy, but the integration is very difficult. There are three major parts in the design and manufacturing process chain to be considered for tackling this integration problem. At the first position in the process chain there is the optical design occuring. At this stage a negotiation between manufacturing and design could improve manufacturability because of more possible integration approaches. The second stage is the mechanical design. Here the appropriate manufacturing approach is already chosen, but may be revisited due to incompatiblities with, e.g., stress specifications. The third level is the manufacturing stage. Here are different clamping approaches and fabrication methods possible. The current article will focus on an approach ("snap-together") where two mirrors are fabricated on one substrate and therefore a reduction of the number of degrees of freedom to be aligned are reduced to six. This improves the amount of time needed for the system integration significantly in contrast to a single mirror fabrication.