Comment on "Fast data processing method for multispectral radiation thermometry based on Euclidean distance optimization"

A recent publication [ Opt. Express , 32 , 1342 ( 2024 ) 10.1364/OE.510084 ] presents a processing method for multiwavelength pyrometry (MWP) that claims to be accurate without requiring an a priori emissivity model. MWP is known to be an underdetermined problem which, as a result, has an infinite number of exact solutions. The proposed method can therefore only lead to one of these solutions (albeit approximately), with no way of telling whether it’s close or far from the real solution we’re looking for. Notwithstanding this, the results obtained by the authors systematically showed small errors. The reason is that they relied on the minimum and maximum values of the actual emissivity spectrum, knowledge of which is in fact very demanding a priori. By the way, when this knowledge is available, the temperature and the emissivity spectrum can be recovered directly using a conventional method. Without tight constraints on emissivity range or a priori emissivity model, MWP leaves us with an infinite number of permitted solutions , among which the actual solution is impossible to guess, leading to a deadlock.