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Iodine absorption filters for Doppler global velocimetry

The iodine absorption filter is a critical component in the implementation of the emerging flow measurement technique of Doppler global velocimetry. The aim of this paper is to discuss the various factors influencing the performance of this type of frequency sensitive optical filter and to suggest how its design should be optimized. This advice, based upon the authors' own experience and a surprisingly large body of literature, is designed to help prospective users of Doppler global velocimetry. Some of the material may also have relevance to other forms of optical measurement which employ absorption filters.