SWIR and IR optical lens materials are difficult to machine, since often they are based on micro-crystalline or crystalline substrates which makes them also brittle and difficult to polish. SWIR spectrometer optics for CarbonSat, Sentinel 5 or NISP (Euclid) for instance are highly critical with respect to straylight performance. For mass and volume reasons the optical design of the camera of the spectrometer is based on lenses (Si, ZnSe, ZnS).

Increasing numbers of regulations in Europe (e.g. RoHS, REACH) are implemented targeting sustainable development, environmental impact and protection of human health leading directly to obsolescence of qualified materials, processes and technologies, as manufacturers are forced to change materials compositions, alter manufacturing processes or take the decision to remove materials from the European market. The REACH roadmap for identification of future substances of very high concern (SVHC) indicates to target a wider range of isocyanates.