Optical metrology: the long and unstoppable way to become an outstanding measuring tool

Abstract

Metrology and quality are two sides of the same coin and high quality standards are a must for the majority of manufacturers in all industrial branches. Above all, optical principles have some exceptional properties that make them indispensable for use in all aspects of quality control. To them belong in particular the non-contact and high speed interaction with the object under test, the largely free scalability of the dimension of the probing tool, the high resolution of the data, the diversity of information channels in the light field, and the flexible adaptability of the measuring standard – the wavelength of light. On the other hand the user is confronted with a number of serious challenges. Some of the biggest challenges that currently attract high attention in both the technical and life sciences, relate to exceeding the physical limits of resolution, to be ready for the exploration of exotic materials and to improve the precision of the measurement. Therefore optical measurement methods are subject to constant improvement. The characteristics that give rise to improve the performance of the systems are obviously dependent on the purpose of the measurement and the object under test. But there are also general features that can be used to assess the performance of a measurement system. To them belong especially the spatial and temporal resolution, the area related resolution, the precision, the trueness, robustness, the degree of automation, the process capability and the ability to work as close as possible to the process. After a short introduction in the history of optical metrology, we describe some important fields of application and the optical measurement principles used there. Based on this we make an attempt to create a list of general and application dependent features for the assessment of modern measurement systems and propose measures to improve their performance. Finally we illustrate this on example of a new nano positioning and measurement device and show selected measurement results.