Inline thickness measurement with imaging ellipsometry

In many coating-lines exact thickness-control is essential. We demonstrate some results with a stroboscopic imaging ellipsometer, which enables to acquire an image of the thickness distribution of a certain layer during or right after production making it an ideal tool for inline-monitoring. The prototype obtains a thickness-distribution with 10-100Hz acquisition rate. The accuracy is in the range 2-10% of the layer thickness. Since there are no moving parts and only monochromatic illumination with a standard laser-diode the solution is cost-effective and can be easily installed. We demonstrate three different applications, namely SiO₂ on Si, oil on steel, and MgF₂ on glass.