We don’t realize it, but optical sensor technology and metrology are everywhere. The till scanner in the supermarket, the light curtain in the multi-storey car park, the laser spirit level, the speed camera on the motorway - these are just a few examples of optical metrology using specialized optical components with modified optical coatings. Yet metrology proper goes far beyond this - examining the ingredients of foods or determining harmful substances in air by means of spectroscopy, for example. Optical measuring methods of this kind share the common feature of using modified optical coatings such as colour filters, beam splitters and mirrors to extract the spectral ranges of interest. The requirements placed on optical elements of this kind may be enormous, with the result that the required coatings can often only be realized by the ion-beam sputtering method.In addition, imaging processes are also frequently used to obtain spatially-resolved spectral data in the ultraviolet, visible light or near infrared ranges, for example. This enables pictures of growth or disease in plants, for example, to be obtained. Such systems may already be very large as a result, which means the demands placed on the necessary coatings are always increasing.