Optical glass and the EU directive RoHS

Abstract

Optical glass is part of optical systems, being subject to the EU directive RoHS, restricting the use of certain hazardous substances in electric and electronic equipment. Some special optical and filter glasses contain lead or cadmium, since these elements are essential for some special glass properties needed by high end optical systems. Most lead containing glass for consumer optics has been replaced by lead free versions. A lot of effort has been spent searching for substitute glass types. But for some remaining applications a set of lead or cadmium containing glass types have revealed to be irreplaceable. Even though they are used only in small amounts and are of negligible environmental influence, long and tedious effort was necessary to obtain an exemption from the directive. The optics community has to stay alert to prevent vast damages due to possible non-availability of glass types crucial for very important applications such as fluorescence microscopy. There are tendencies to restrict the use of even more elements, which could endanger the existence of most optical and filter glass types. These materials are key enabling factors of technical civilization as a whole because they are used in all industries and many research fields. They must be taken out of the scope of RoHS in total since exemption procedures will lead to periods of secured availability too short to be acceptable for the design of optical systems, which usually takes years and in high end optics must be valid also for long term deliveries. New regulations improving ecological aspects should assess the consequences on other important goals of society.