4. Characterization of thermal imaging cameras

4.1 Sensitivity and resolution

Thermal cameras, being optical instruments, can be classically characterized in terms of field of view and resolution. The notion of sensitivity is expressed a little differently from that of instruments working in the visible range, for the following main reason.

In the visible spectrum, illuminance varies in large proportions between day and night (typically a ratio greater than 10 ⁹ ). On the other hand, contrast between objects is independent of illumination conditions. Sensitivity is therefore generally expressed in terms of minimum illuminance. In thermal infrared, at least for terrestrial applications, since scene temperature is within fairly narrow limits, scene luminance varies...