A protective optical filter assembly for thin film filters having first and second transparent substrates (210) (220) facing one another and separated by a resilient element (230). A sealed region is formed between the transparent substrates by applying a compressive force that compresses the resilient element. A first thin film filter (214) may be formed on the first substrate, and second thin film filter (224) may be formed on the second substrate. The thin film filter may be contained within a carrier (240). The compressive force, may be generated by one or more interference-fit aperture rings or threaded aperture rings, a given aperture ring may be opposed by another such aperture ring or a fixed stop (260). 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.