Thermal imaging lenses run from narrow fields of view 60 to 150, standard 250 view, and wide fields of view from 450 to 900. For special uses, for example in research and development (R&D), we will also see macro lenses that can see extremely sharp details. A thermal imaging scanner can use one or more than one lenses. It all depends on its uses.
Thermal lenses are made of crystal, not glass. To know the difference between crystal and glass click here. Therefore, there are minor differences in the physical properties.