A Laser Extensometer of the type W-400RT was used for strain measurement on a foam specimen. The specimen was marked with high reflective sticky stripes in a distance of 20 mm.
The stripes are only glued at the material surface. Thus the inner areas of the specimen are not influenced.

The high reflective stripes are reliably detected by the Extensometer intependent of the specimen's color. The large scanning range of the W-400RT of 400 mm is a basis to use large measuring lengths. Together with the resolution of 1.7 µm the laser extensometer can be used for the whole range from small strain at the beginning of the measurement up to large strain at rupture.

Thus a accurate strain measuring without influrence or damage of the specimen is easily possible.