Lock-In thermography was developed to complement other non-destructive techniques.
It can assist in understanding material heterogeneities or electrical failures (short circuit or leakage).
The load can be of any kind - thermal, electrical or mechanical, and of several types - continuous, pulsed or periodic (lock-in).
With static thermography, surface phenomena or thermal heterogeneities can be measured.
To detect internal inconsistencies within the sample (interface, crack, etc), a thermal flux is created, dynamic system and then its repartition at sample surface is observed.
With Dynamic « lock-in » Infrared Thermography, the mean is very sensitive and « hot spot » of some 10-3K (or even 10-4K) is detected.