At ICB - Institute for Chemical and Biochemical Sensor Research we still lead a project for the optimisation of an identification system for black plastics, which we presented at the Hannover Fair 2000.
It is based on AOTF (Acousto-Optical Tunable Filter)- technology, which allows contact-free measurements, without being forced to use the spectral area of the mid infrared. Thus, sensitive halogenide optics can be avoided. [Details]
The left half of the above picture shows a wheel with applied polymer samples from automobile recycling. For demonstration purposes they pass in turn the sensor (right half).
The system is of course applicable to other tasks, e.g. the contact-free thickness measurement of organic layers, especially on metal surfaces. An existing application is the on- or off-line-measurement of oil films.