Abstract: A protective optical filter assembly for thin film filters having two transparent substrates facing one another and separated by a resilient element, a sealed region is formed between the transparent substrates by applying a compressive force that compresses the resilient element. The thin film filter may be contained within a carrier. The compressive force may be generated by one or more interference-fit aperture rings or threaded apertures ring, a given aperture ring may be opposed by another such aperture ring or a fixed stop. Alternatively a snap fit carrier may be used to generate the compressive force. The sealed region may have a gas having a positive pressure or a liquid.