Researchers in Kiel develop a new method of thermographic
imaging
(July 27, 2015) Those
who wish to renovate their houses and make them more energy-efficient often use
the well-known yellow to blue thermal images to visually identify weak spots
applying infra-red measurements. Thermographic imaging is also used in industry
for materials testing. Depending on the material, however, the method can
result in large measurement errors. Scientists at Kiel University have now
developed a technology that visually identifies the slightest temperature
differences with high spatial resolution, whatever the material. This new
principle competes with other procedures as well, as reported by researchers in
the current edition of the scientific journal, Advanced Materials.
In their research, the scientists in Kiel make use of the
magnetic properties of a certain material. In experiments, a thin, transparent
layer of a garnet compound (garnet is a mineral from the silicates category) is
placed on the object to be investigated - in this case, an integrated circuit
of a microchip. If the temperature anywhere on the circuit changes even by the
slightest amount, the layer of material reacts by changing its magnetic
properties. The warmer it becomes, the smaller the magnetisation.
This magnetisation, being different depending on the
temperature, can be made visible with a so-called polarisation microscope:
polarised light is light that is forced into a certain direction of oscillation
(similar to some sunglasses). When it reaches the surface of the thin layer, it
is reflected differently, depending on the materials’ magnetisation. A digital,
light-sensitive camera captures the reflected light. The magneto-optical images
show the temperature distribution in the circuit and the tiny magnetic domains
of the material; these are separate areas that have the same polarisation.