CONTROLLED STRESS THERMAL COMPENSATION FOR FILTERS

A temperature compensated optical filter assembly comprising a plurality of thin films having temperature dependent indices of refraction which are deposited on a glass substrate so as to form a conventional interference filter thereon. The glass substrate is adhesively coupled to a metal holder such that the deposited thin film interference filter is interposed between the glass substrate and an adhesive layer distributed along a mounting surfa ce of the holder. Thus, a first thermal mismatch stress is applied by the glass substrate onto an inner layer of the interference filter and a second mismat ch stress is applied by the holder onto an outer layer of the interference filter, wherein the first and second mismatch stresses depend on the temperature of the filter assembly. The glass substrate, the adhesive, and t he holder are preferably formed of materials having mechanical properties such that the first and second mismatch stresses compensate for the effects of th e temperature dependent indices of refraction of the thin films so as to uniformly maintain the spectral performance of the filter assembly in respon se to a change in temperature. In one embodiment, an additional degree of freed om is obtained by electro/magneto-strictively prestressing the thin film stack during the formation thereof. In another embodiment, an active stress management system is utilized.