Observation of powder and particles in a container by pulsed thermography

We propose a technique for observing a granular substance, such as a powder or particles, in a container, where the characteristics of a transient decrease in temperature on the surface of the container are monitored by thermography following momentary heating of the surface of the container by a light flash. This technique is a type of non-destructive inspection employing pulsed thermography. We investigate the observation of polypropylene balls and ceramic balls in a polyvinyl chloride container and an aluminium container, and also demonstrate the observation technique using copper powder and wheat flour in a copper container and a paper container in addition to the containers described above. The proposed technique is successful in observing the polypropylene balls, ceramic balls, copper powder and wheat flour in the polyvinyl chloride and paper containers. However, the technique cannot clearly observe any of the substances in an aluminium or copper container because of the rapid homogenisation of the surface temperature distribution on the metal container by facile heat diffusion in the plane direction within the metal plate. We expect this non-contact observation technique to be useful for material control, product inspection and product analysis in manufacturing.