Figures of merit of thermoelectric and bolometric thermal radiation sensors

Figures of merit condensing the performance parameters of radiation sensors such as responsivity, noise equivalent power and time constant in a single number can be useful for rating the performance of a particular sensor in comparison to other ones or to fundamental performance limits. The classification system and the figures of merit of radiation sensors introduced by R. C. Jones are revisited for thermal radiation sensors with the focus on thermopiles and bolometers. As a result it is stated that radiation thermopiles and bolometers should be classified differently: Type III detectors for thermopiles vs. Type II detectors for bolometers. Modified figures of merit are suggested and relations between them given. The figures of merit are applied in an overview on state-of-the-art thermopiles and bolometers operated at room temperature.