Mesoscopic IR Radiometry
The mesoscopic infrared radiometry scheme is quite straightforward. The
sample is heated by a modulated or impusional source, the heat is diffused
as described above, and the Stefan-Boltzmann emission variation from the
sample surface is measured by an appropriate infrared detector. Although
surface quality is relatively unimportant, the sample must be an IR emitter,
and thus metallic samples can not be used. Minimum temperature variations
which can be measured are on the order of Delta T = 10-2 to
10-3 K. One application of this technique that we have developed utilizes
computer controlled scanning of the sample, and an Cassegrain objective for
light collection. By scanning the sample surface around the heated region,
thermal diffusivity can be measured. Measures associated with a twin
detector permits differential imaging of mechanical defects such as vertical
and slanted cracks in metals which act as thermal barriers.